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Near Infrared Transillumination in Acute Maxillary Sinusitis: Theoretical Background – Clinical Application – Diagnostic Potential – Limitations
Med. Laser Appl. 18: 217–231 (2003) © Urban & Fischer Verlag http://www.urbanfischer.de/journals/lasermed
Near Infrared Transillumination in Acute Maxillary Sinusitis: Theoretical Background – Clinical Application – Diagnostic Potential – Limitations MARIETTA HOPF1 and JÜRGEN U. G. HOPF1,2 1
Department of Otorhinolaryngolgy, Head and Neck Surgery, University Medical Center, Campus Benjamin Franklin (Head: Prof. Dr. H. Scherer), Charité Universitätsmedizin Berlin, Germany 2 “HNO am Roseneck”, Berlin, Germany
Submitted: June 2003 · Accepted: July 2003
Summary Among the inflammatory diseases of the paranasal sinuses in man the acute maxillary sinusitis shows a particularily high incidence. Mostly emerging from a primarily viral rhinitis or rhinosinusitis the paranasal inflammation secondarily becomes purulent, if mucosal swellings and drainage disorders in the osteomeatal unit of the middle nasal meatus persist to be. The insufficient ventilation of the related paranasal sinuses – sinus maxillaris, sinus ethmoidalis and sinus frontalis – gives rise to a bacterial superinfection of the mucosa. In cases where the right diagnosis has not been found early enough or the acute sinusitis stays untreated the situation can culminate in serious complications to the orbit, to the facial soft tissues and even to the endocranium possibly leaving continual damages to the patient’ health. Despite the otorhinolaryngologic examination significantly improved and refined by endo- and transnasal endoscopy, the direct visual inspection of the maxillary sinus for diagnostic reasons is normally not possible. This refers to the very small natural orifice of the maxillary sinus and the mucosal swellings which block the endoscope from penetrating into the middle nasal meatus as well as the sinus. Therefore plain film X-ray-imaging and sonography – in minor cases and in the follow up period – represent the gold standard for making the diagnosis of sinusitis up to now. Stimulated by promising basic investigations on the small spectrum light transillumination of biological tissues with selected wavelengths we re-adopted the principle of diaphanoscopy for diagnostic imaging of the maxillary sinuses. For its clinical application we designed a measuring setup where we replaced “cold (white) light transillumination” of the sinus by diaphanoscopy with photons of the near infra red spectrum of light (NIR). In this narrow part of the spectrum ranging from a wavelength of 650 to 1100 nm – the so-called ‘optical window` – the incidence of photon scattering is much higher than absorption events by the tissue. This biophysical finding renders it possible in an excellent manner to utilize NIR-photons for the transillumination of body cavities and their detection in order to create a two-dimensional imaging. Our clinically controlled study supplied clearly categorizable NIR-diaphanoscopic images of different stages of an acute maxillary sinusitis showing a good positive correlation to traditional plain radiography and computer tomography (CT scan-imaging). Additionally NIR-diaphanoscopy is not only a system of morphological imaging but also of biomonitoring in the considered anatomical area.
Key words Sinusitis, cold light diaphanoscopy, Near IR diaphanoscopy, diagnostic imaging, infrared spectrum, otorhinolaryngology 1615-1615/03/18/03-217 $ 15.00/0
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Introduction Acute sinusitis maxillaris is a widely spread disease, although exact data on its incidence are missing in the relevant literature. For sinusitis maxillaris chronica, the reported incidence ranges between 5 and 25% (1). Etiologically, acute sinusitis maxillaris mainly develops within an acute rhinitis, with a primarily viral infection entailing a secondarily bacterial purulent rhinositis. Pathophysiologically, the functional obstruction of the natural junctions of the main nasal cavity and the maxillary sinus by swelling of the mucosa leads to ischesis and inflammations of the mucosa in the affected sinus. The otolaryngologist’s diagnosis is based primarily on the patient’s history and the inspection of the main nasal cavity (rhinoscopia anterior and posterior). Redness, swelling and accumulation of pus in the middle meatus of the nose indicate an acute inflammation. The small diameter of only a few millimetres makes a direct endoscopic inspection of the maxillary sinus through its natural ostium via the middle meatus of the nose impossible in most cases. Another indication is obtained by digital palpation of the foramen infraorbitale at the bony facial wall of the maxillary sinus. The irritation of the trigeminal infraorbital nerve leaving its bony channel here causes pain on pressure.
Diagnostic Imaging In diagnostic imaging the plain film X-ray in occipito-mental ray trajectory (om) according to Waters is the standard tool for maxillary sinus evaluation. It serves for an exact representation of the anatomic structures prior to any invasive therapeutic strategies to the maxillary sinuses. An empyema in example may require a sharp needle puncture of the sinus through the inferior nasal meatus and an antrum rinsing for pus evacuation. For this purpose, an X-ray image according to Waters which shows the individual empyema’s size and location is indispensable. If the acute maxillary sinusitis spreads to the surrounding anatomic structures of neighbouring organs, complications like an orbital phlegmon will occur. In such case, further diagnostic imaging (CT, MRT) is absolutely necessary.
For many ENT specialists, sonography of the maxillary sinuses is the diagnostic tool of choice to confirm their tentative diagnosis. The patient’s pain and the risk of serious complications compel the attending physician to initiate an adequate medication or even surgery, without delay. The ultrasonic examination is well suited for this purpose in initial stages of the disease. It can be done quickly and at favourable cost and be repeated as often as required. For such ultrasonic examinations, the ENT specialist prefers the B mode sonography over the A mode sonography. For the A mode sonography the signal of the acoustic wave is recorded in the form of an one-dimensional derivation as an echogram only. The conclusiveness of this ultrasonic examination is limited, however, because the gain of signals is considerably impeded if air is still inside of the sinus. The use a two-dimensional signal gain (B-mode sonography) reveals much more detail information on the target, is much easier interpretable but also impeded by air that leads to total signal extinction making pathologic processes “behind the air shield” difficult or not to image, at all. Nevertheless, sonography has become the established routine procedure in modern rhinology. Attempts to develop an easy-to-apply reliable routine diagnostic procedure in addition to or even replacing sonography, led from the historical endeavours (7, 13, 14, 15).to the use of photons for the transillumination of the paranasal sinuses (6). Thus, quantifiable stray light information can be obtained which allow the state of the maxillary sinus to be evaluated. The knowledge that • light of NIR wavelength has a specifically high penetration depth into biological tissue and that • light of the NIR spectral range responds very sensitively to even tiny tissue changes by absorption and scattering make the near infrared transillumination a promising diagnostic possibility. The goal of transillumination procedures was the imaging of inner structures of the human body. In 1929 Cutler (4) reported on the transillumination of the female breast to diagnose lesions with this method. He took advantage of the different absorption coefficients of tumour and healthy breast tissue. Scattering was neglected as a disturbing effect. Transmission measurements showed that an optical win-
Near Infrared Transillumination in Acute Maxillary Sinusitis
dow between 600 and 1300 nm exists in tissue. Olsen et al. used this procedure for cancer screening in female breasts. Although their pictures were diffuse and hazy because of light scattering they could detect 95% of the mammae tumours examined. First examination of tissue parameters in the near infrared in 1982 by Beuthan (2) showed the way for the infrared trasillumination in the diagnosis of sinusitis by using the scattered radiation for diagnosis.
In general the transmission is determined by: T = Iout/Iin (Iout = irradiated light intensity, Iin = light intensity after transillumination of a layer) In time integrated imaging all photons (mainly scattered photons) can be used for detection: Iout = Iin · exp [ – µ effd], µ eff = [3µa (µ a + µ s)]1/2 (µ eff = efficient scattering coefficient, d = layer thickness) In this diffusion approximation the transmission is about 6 × 10–10 and can be detected by standard sensors.
Theoretical background The inspection of parts of the human body with the help of optical instruments has been used in medical diagnosis for more than a century, although its application has been limited, so far. In recent years however extended knowledge of tissue optics (absorption/ scattering) and improved sensor technology offered new solutions to this problem. The most important condition for the realisation of the time integrated IR- transillumination is the knowledge of the optical tissue parameters. The scattering coefficient µ s, the absorption coefficient µ a and the anisotropy factor g of the tissues involved in transillumination limit the use of this method. In general, in the range of the near infrared spectra the scattering coefficient is one order of magnitude larger than the absorption coefficient (12): It is:
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Fig. 1. Scattering of light irradiating biological tissue.
µs > µa
There will be an excessive intensity of light by scattering in tissue (Fig. 1), which will be particularly high in the hollow organs including the paranasal sinuses (factor 7). The reduced scattering coefficient µ s‘ includes the anisotropy factor g: µs‘ = µs (1 – g) The anisotropy factor g indicates the preferred propagation direction of scattering and may range from values of g = –1 (backward scattering) via g = 0 (isotropic scattering) to g = +1 (forward scattering) (Fig. 2). In all biological tissue the anisotropy factor g has a high value (e.g. 0.93 to 0.98) in the near infrared, e.g. tissue shows a high degree of forward scattering.
Fig. 2. Anisotropy factor g, backward scattering, isotropic and forward scattering (modified according to Roggan (1997).
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Fig. 3. Distribution of the scattering of photons in a tissue layer (Beuthan 1993) (layer thickness = 10 mm, µ a = 0.005 mm–1, µ s= 10 mm–1, g = 0.07, 106 photons) 30 times of the main free path lengths.
Infrared-imaging is used in regions of the body in which (in relation to the main free path length) thick tissue layers are transilluminated. We have to deal with layer thicknesses of at least 30 times of the main free path length. In this case the “direction memory” of the photons is considerable spread. For illustration Fig. 3 shows the result of a Monte Carlo simulation. A point light source is put orthogonally on an infinitely expanded tissue layer of 10 mm in thickness (µ a = 0.05 mm–1, µ s = 10 mm–1, g = 0.97, 106 photons are irradiated into the tissue). The simulation shows among other things that on the other side of the layer the majority of the escaping photons were scattered 130 times or more. Only one photon was scattered only 77 times. Therefore, it is necessary to consider two situations when looking at infrared imaging: A: µ s varies with the metabolism of the tissue (diseased/healthy). In this functional variation the diaphanoscopical procedure has to react to the changes of scattered light. Such a situation can be found when transilluminating the maxillary sinuses. B: µ‘ s1 𠵑 s2 or/and µ a1 π µ a2. This situation is given in blood vessels in all kinds of tissue and in thin layers of very different optical parameters (i.e. bone cladded by connective tissue). If in
this case partial congruences appear in the direction of the projection and the contrast is sufficient for the detection of simple structures. Especially the combination of bone and other tissue is very important for the endoscopic diagnosis in the head. In near infrared imaging the paranasal sinuses are penetrated by electromagnetic waves of the near infrared spectrum. The emergent radiation can be measured by means of a NIR camera thus providing scattering light data on the transilluminated region. These data can be represented as a two-dimensional picture and then evaluated. Consequently, infrared imaging is a transmitter-receiver system and suitable for medical diagnostic imaging. In sinusitis changes of the tissue are observed in the area of the paranasal sinuses. By intensified blood supply of the mucous membranes the absorption of the tissue increases in the near infrared spectrum. At the same time layers with enhanced scattering are growing. In the extreme case the inflamed cavity is filled with fluid. This process corresponds to the situation described in A. µ s can increase by one order of magnitude. Therefore, the changes caused can be easily detected. Fig. 4 shows the principal sketch, a practicable set-up and the examination of the infrared imaging technique in the diagnosis of sinusitis.
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The near infrared irradiation (650–1100 nm) of a forceps-like applicator positioned in the mouth penetrates the jaw bone to reach the right and left maxillary sinus simultaneously. Hereby the radiation is scattered in relation to the state of illness (the change of absorption is negligible). The detection of the scattered radiation can be compared with the measuring situation at an integrated sphere on which a measuring opening is closed with a semi-opaque membrane. In the given case this membrane is the thin bone of the orbital floor. At the boundary eye/orbita ground parts of the emergent scattered radiation can be visualised on the surface of the face in the infraorbital region (Fig. 5). In comparison to the imaging situation during plain radiography Fig. 6 shows the light pattern of near infrared imaging.
Fig. 5. Schematic drawing of a sagittal section of the head. The arrows show the direction of the near infrared irradiation. After penetration of the maxillary sinus (1+2) the scattered radiation in the direction of the face can be visualised in the area between the bulbus oculi and the orbital floor.
Fig. 4. Principal sketch of infrared imaging technique and the demonstration of the examination procedure. Near infrared radiation is administered through an applicator in the mouth. The scattered light is detected by a filtered CCD camera and can be visualised on a monitor. For documentation a video printer or digitalisation of the image is possible.
Fig. 6. Comparison (X-ray/Near Infrared Imaging) of projection and diagnostic findings in principle
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Material and Methods Diagnostic Imaging Procedures Near infrared imaging of the sinuses The maxillary sinuses were represented using a near infrared imaging system with integrated monitor. The related findings (in the form of scattered light projections upon the contour of the face) of each patient were photo-documented by means of a video printer. A-mode sonography of the paranasal sinuses For A-mode sonography of the paranasal sinuses a Homoth echoscope with an Atmos 3.5 MHz sonic head in the classical examination technique was used (8). The findings were documented separately for each sinus and side through curve plotting of a “frozen” representative monitor image. The method is suitable for representing fluid- and soft-tissue proof structures in the maxillary sinuses’ region. B-mode sonography of the paranasal sinuses B-mode sonography of the paranasal sinuses was done with a Picker CS 9000 one each 7.5 MHz linear and 5 MHz sector scanning sonic head in the classical examination technique with and without water path (5, 8). The findings were documented separately for each side and sinus by means of a polaroid instant photography or video print of a “frozen” representative and informative monitor image.
Classical radiographs of the paranasal sinuses For routine symptom-related diagnostic radiography of pathological changes of the paranasal sinuses we applied the two conventional settings in the occipitofrontal and occipito-mental ray trajectory. Computer tomography of the paranasal sinuses Next to nuclear magnetic resonance imaging (MRI), computer tomography (CT) happens to be the most reliable and most sensitive imaging procedure for regular anatomic and pathological findings. We had computer tomograms in the bone and soft-tissue window, with and without contrast medium. Lamination was made in coronar and axial section planes of layer thicknesses ranging from 2 to 5 mm.
Near-Infrared Diaphanoscopy The analysis was based on the evaluation of the infraorbital scattered light corona above the maxillary sinus. For the correct diagnosis it is necessary to examine some hundred patients. In all cases of no pathological findings in the maxillary sinuses we could detect a typical near infrared diaphanoscopic image as shown in Fig. 7. The scattered light appears as a “sickle shaped figure” with clear light in the region of the orbital floor. In cases of sinusitis, the sickle shaped figure was not found. The scattered light decreased or was not visible (Fig. 8). For documentation we defined a Valuation-Index (VI) from one to four and additionally a statement if both sides appear symmetric or asymmetric in light or figure as shown in Table 1: Table 1. Valuation-Index (VI) for near infrared imaging of maxillary sinuses. • • • • • •
VI 1 – sickle shaped figure VI 2 – reduced scattering light VI 3 – scarcely scattering light VI 4 – no scattering light A – symmetric B – asymmetric
Examination methods for clinical evaluation
Fig. 7. Normal near infrared imaging of maxillary sinuses.
The clinical evaluation of the new near infrared imaging procedure was based on the following examinations and documentation:
Near Infrared Transillumination in Acute Maxillary Sinusitis
• • • • •
general and symptom-related patient’s history basic clinical examination by the ENT specialist NIR transillumination of the maxillary sinuses A-mode sonography of the maxillary sinuses B-mode sonography of the maxillary sinuses (with and without water path) • plain X-ray radiography • computer tomography in axial and/or coronary layers
Course of examination, documentation and statistical evaluation Patient’s history, clinical ENT status, endoscopy, infrared diaphanoscopy, sonography were taken or made by different physicians of the University ENT department, with the near infrared imaging, A-mode and B-mode sonographies being evaluated by different physicians who had no knowledge of the other examination results. This course guaranteed an unprejudiced evaluation. The radiological procedures (plain X-ray radiography and computer tomography) were evaluated by senior specialists of the University Radiological Department. For statistical computation of the sensivities and specifities we used standard computer software.
Number of patients examined For clinical evaluation of NIR transillumination, we received 400 maxillary sinus findings (of 200 pa-
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tients), in total. All these findings had been made in our ENT Department. The findings were found suitable if radiographs and a computer tomography of the paranasal sinuses had been made. The patients had consulted the ENT Department because of a disease or in order to exclude an ENT disease. A total of 379 maxillary sinuses were included in the study, 260 of which had been diagnosed as healthy while the remaining 119 showed the clinical diagnosis of an acute sinusitis. In 84 patients bilaterally healthy maxillary sinuses were found, 92 patients suffered from unilateral acute sinusitis, with the respective opposite side being healthy, 13 patients were found to have contracted bilateral acute sinusitis maxillaris, and in one patient a unilateral sinusitis acuta and a chronic polypous sinusitis on the opposite side were found. To simplify the procedure, the maxillary sinus findings were evaluated not in pairs, but individually independent of the fact whether or not the opposite side was healthy or affected, too. The statistical evaluation included only those patients for whom all the afore-mentioned examinations including the imaging procedures had been completely documented. Having evaluated all the findings (history, ENT status, endoscopy, A-mode and B-mode sonography, plain X ray radiography of the paranasal sinus and computer tomography), the maxillary sinuses were categorised into the groups “healthy” or “diseased”.
Fig. 8. Near infrared imaging of maxillary sinuses in case of acute maxillary sinusitis on one site, endoscopic view of the nasal cavity with purulent secretion.
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The youngest patient was of an age of 6 years, the oldest patient was 73 years of age. The average age was 33 years, the median was 31.5 years. The study extended to 112 female and 78 male patients.
Results We examined 379 maxillary sinuses of 190 patients. All of them have had a computer tomography in coro-
nary and/or axial sections as well as standard plain Xrays according to Waters of the paranasal sinuses and additionally an A-mode and B-mode sonography. Computer tomography (Fig. 9) in combination with the history, the ENT-examination and the patient’s symptoms were our gold standard for statistical evaluation of near infrared imaging. 260 sinuses were healthy. In 119 maxillary sinuses we found an acute maxillary sinusitis. In 11% the sinus was totally filled, in 36% the sinus was partly filled with fluid.
Fig. 9. Clinically acute maxillary sinusitis, identified by different diagnostic procedures: NIR transillumination (A), plain radiography (B), A-mode sonography (C), computer tomography (D), B-mode sonography (E).
Near Infrared Transillumination in Acute Maxillary Sinusitis
In cases of healthy sinus or acute maxillary sinusitis the examination results of each imaging procedure, each analyzed from another physician were categorised into five groups (Table 2): Table 2. Analysis and interpretation of the imaging results of all methods used for diagnosis of the maxillary sinuses. Category 1: “sure healthy” Category 2: “healthy” Category 3: “healthy/pathologic in question” Category 4: “pathologic” Category 5: “sure pathologic”
Healthy maxillary sinuses The results for healthy maxillary sinuses (n = 260) are shown in (Table 3): Table 3. Clinically healthy maxillary sinuses, identified as healthy or diseased by different diagnostic imaging procedures. Diagnosis: Healthy Maxillary Sinuses (n = 260)
Identified as healthy (Category 1–2)
Identified as diseased (Category 3–5)
Computer Tomography Plain X-ray Radiography B-mode Sonography A-mode Sonography NIR Transillumination
260 (100%) 255 (98.1%) 260 (100%) 259 (99.6%) 259 (99.6%)
0% 5 (1.9%) 0% 1 (0.4%) 1 (0.4%)
Applying NIR transillumination 246 maxillary sinuses (94.6%) were found to be in the category 1 “sure healthy”, 13 maxillary sinuses (5.0%) in the category 2 “healthy”, und 1 sinus (0.4%) in the category 3 “healthy/pathologic in question” and none in the category 4 “pathologic” or category 5 “sure pathologic” In comparison • with the A-mode sonography 259 maxillary sinuses (99.6%) were in the category 1 “sure healthy”, and 1 sinus (0.4%) in the category 3 “healthy/pathologic in question” and none in the category 4 “pathologic” or category 5 “sure pathologic” • with the B-mode sonography 244 maxillary sinuses (93.8%) were in the category 1 “sure healthy”, 16 maxillary sinuses (6.2%) in the
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category 2 “healthy”, none the category 3 “healthy/ pathologic in question” and none in the category 4“pathologic” or category 5 “sure pathologic” • with the plain radiography of the paranasal sinuses 255 maxillary sinuses (98.1%) were in the category 1 “sure healthy” and 5 maxillary sinuses (1.9%) in the category 3 “healthy/pathologic in question”. • and with computer tomography of the paranasal sinuses 260 maxillary sinuses (100%) in the category 1 “sure healthy” and no maxillary sinus in the other categories. In order to determine the specifity, all maxillary sinuses of the validation indices “sure healthy” (1) and “healthy” (2) were categorised into the “identified as being healthy” group, while all maxillary sinuses of the validation indices “healthy/pathologic in question” (3), “pathologic” (4) or “sure pathologic” (5) were classified into the “identified as being diseased” group. With computer tomography and B-mode sonography all healthy maxillary sinuses had been actually identified as being healthy. By means of plain radiography of the paranasal sinuses, 5 healthy maxillary sinuses (1.9%) were identified as “healthy/pathologic in question” (category 3), and so was one each (0.4%) healthy maxillary sinus by means of NIR transillumination, A-mode and B-mode sonographies, Consequently, these maxillary sinuses were categorised into the “identified as being diseased” group.
Acute maxillary sinusitis The results for acute maxillary sinusitis (n = 119) are shown in (Table 4): Table 4. Clinical diagnosis “acute maxillary sinusitis”: all maxillary sinuses were classified by the different diagnostic procedures into the group “identified as diseased“. Diagnosis: Acute Maxillary Sinusitis (n = 119)
Recognized as diseased (Category 3–5)
Computer Tomography Plain X-ray Radiography B-mode Sonography A-mode Sonography NIR Transillumination
119 (100%) 119 (100%) 119 (100%) 119 (100%) 119 (100%)
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With NIR transillumination 9 maxillary sinuses (7.6%) were in the category 3 “healthy/pathologic in question”, 66 (55.5%) in the category 4 “pathologic” and 44 (36.9%) in the category 5 “sure pathologic”. In comparison • with the A-mode sonography 4 maxillary sinuses (3.4%) were in the category 3 “healthy/pathologic in question”, 74 (62.2%) in the category 4 “pathologic” and 41 (34.5%) in the category 5 “sure pathologic”. • with the B-mode sonography 63 maxillary sinuses (52.9%) were in the category 4 “pathologic” and 56 (47.1%) in the category 5 “sure pathologic”. • with the plain radiography of the paranasal sinuses and CT-Scan all 119 maxillary sinuses (100%) were in the category category 5 “sure pathologic”. In all cases (119) of acute maxillary sinusitis the different diagnostic imaging procedures recognized a “diseased sinus” (Valuation Index 3–5), (Tab. 4).
Specifitiy and Sensitivity The statistical evaluation provided the results shown in Table 5. The specifity for identifying a healthy maxillary sinus was 99.6% in the case of near infrared diaphanoscopy and A-mode sonography. As for plain radiography of the paranasal sinuses, the specifity was less, namely 98.1%.
For B-mode sonography and computer tomography of the paranasal sinuses a 100% specifity was recorded. Each diseased maxillary sinus (n = 119) was identified as such by all examination methods including infrared diaphanoscopy. This corresponds to a 100% sensitivity for all methods.
Discussion Our studies on the system analysis and clinical evaluation showed that infrared diaphanoscopy can be applied for diagnostics in otolaryngology and considered a reasonable complement to other imaging procedures. On the contrary to other imaging procedures, the system does not measure the changes in the tissue layer thicknesses, but images changes in the tissue state based on metabolic processes. Even slight changes in the state, such as an hyperaemia of the paranasal sinus mucosa, result in an enhanced absorption and scattering of tissue photons and, consequently, in a reduced transillumination of the scattered light. Infrared diaphanoscopy detects the transillumination of infrared light of the maxillary sinus. In healthy maxillary sinuses, the emergent scattered light appears in the shape of an infraorbital light sickle. Diseased maxillary sinuses generate a different image, which is deformed and of reduced intensity. Infrared diaphanoscopy was developed by Beuthan (2, 3). Having found no references in literature, our clinical evaluation of the suitability of infrared radiation for application in paranasal sinuses diagnostics seems to be unprecedented.
Table 5. Specifity of the different diagnostic imaging procedures for healthy maxillary sinuses and sensitivity for acute maxillary sinusitis with 95%-Confidential-Interval (CI). Diagnostic imaging methods of the maxillary sinus
SPECIFITY Healthy maxillary sinuses (n = 260) Confidential-Interval CI (95%) · 100
SENSITIVITY Acute maxillary sinusitis (n = 119) Confidential-Interval CI (95%) · 100
Computer Tomography Plain X-ray Radiography B-mode Sonography A-mode Sonography NIR Transillumination
… 100% (99.99–100) … 98.1% (96.40–99.75) … 100% (99.99–100) … 99.6% (98.90–100) … 99.6% (98.90–100)
… 100% (99.99–100) … 100% (99.99–100) … 100% (99.99–100) … 100% (99.99–100) … 100% (99.99–100)
Near Infrared Transillumination in Acute Maxillary Sinusitis
Among the issues most difficult to solve was the definition of valuation criteria for the unambiguous description and classification of infrared diaphanoscopy findings. For this purpose, the scattered light intensity had to be evaluated for its qualitative value. For this purpose, the reproducibility of “normal findings” had to be ensured by subjecting healthy people to a large number of examinations. Like for the A-scan and Bmode sonographies, both examination and evaluation should be done by the same physician because the material to be evaluated, i.e. the images, is but one component of the dynamic examination. Some specific experience is required in order to safely evaluate an infrared diaphanoscopy result, which applies to other imaging procedures, too. For infrared diaphanoscopy evaluation the following principles hold: 1. A healthy maxillary sinus shows a typically shaped infraorbital scattered light sickle of high scattered light intensity (Fig. 7). 2. In healthy state, the right and left maxillary sinuses are symmetrical to large extent, minor lateral differences are physiological (Fig. 7). 3. The light intensity, i.e. the scattered light corona, is larger with healthy maxillary sinuses than with acute sinusitis (Fig. 8). 4. In case of people with unilateral or bilateral maxillary sinus disease this scattered light sickle symmetry is not achieved. It always differs from that of healthy maxillary sinuses (Fig. 8). 5. The operation of this examination instrument including the selection of the output light intensity and positioning of the applicator determine the image quality and should be left to an experienced examiner. 6. The evaluation principle for infrared diaphanoscopy is based on the evaluation of different scattered light intensities above each paranasal sinus (1 – normal transillumination, 2 – reduced transillumination, 3 – hard to recognize , 4 – no representation) with data whether or not a lateral difference existed. Actually, however, infrared diaphanoscopy does not permit a differential diagnosis. Consequently, it does by no means replace the established radiological procedures.
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The data are then entered into an evaluation scheme (5 groups, namely “sure healthy” – 1; “healthy” – 2, “healthy/pathologic in question” – 3, “pathologic” – 4, “sure pathologic” – 5). If a paranasal sinus is diagnosed as being diseased, the differential diagnosis can partly be derived from the patient’s history and symptomatology. Thus it is not necessary in each and every case to take further diagnostic steps in order to start an adequate therapy. This refers particularly to large part of sinusitis acuta. In such a case, follow-ups to evaluate the therapeutic result are mostly sufficient. If the scattered light is initially missing or drastically reduced, an increasing scattering light intensity above the respective paranasal sinus indicates the therapeutic result (Fig. 10 follow-up). Comprising all usual examination findings (endoscopy, intraoperative findings) and the computer tomography findings (being the gold standard of the imaging techniques) the clinical diagnosis formed the gold standard for the statistical evaluation. For statistical evaluation, the findings were classified either “identified as healthy” or “identified as diseased”, separately for each imaging procedure. The “healthy” group included all paranasal sinuses, which had been found “sure healthy” and “healthy”. The paranasal sinuses found “healthy/pathologic in question”, “pathologic” and “sure pathologic” were classified into the “diseased” group. The evaluation of all imaging procedures is closely tied to the examiner’s subjective component, which correlates with the physician’s rich experience. In case of radiographs or CT images evaluated by radiologists or ENT specialists, e.g., discrepancies may occur depending on their specific experience, which, in turn, may lead to different diagnoses. Bearing this in mind and knowing the patient’s history, each examination was made or evaluated by that specialist who had the largest experience. All radiological findings (x-ray and CT-scan) were evaluated by the radiologist, the ultrasonic findings by the otolaryngologist and the IRD findings by the authors themselves. The establishment of a new diagnostic method is not justified unless it is at least as good as existing procedures and involves advantages in application or cost. When statistically evaluating the infrared diaphanoscopy in clinical use on 260 healthy maxillary sinuses, the specifity was found to be 99.6%. This means that IRD was equally good as A-mode sono-
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Fig. 10. Follow up of NIR transillumination in maxillary sinusitis: A: day of diagnosis, B: after 8 days of medication, C: 15 days after therapy, D: 22 days after diagnosis, E: pathological findings in the plain radiography at the day of diagnosis, F: computer tomography 6 weeks after diagnosis of acute maxillary sinusitis.
graphy and with a 98.1% specifity even superior to paranasal sinus radiography. Radiography may have been inferior to NIR-transillumination because of its bad recording technique with other anatomical structures interfering. This would explain that 1.9% of the healthy maxillary sinuses had been classified “healthy/pathologic in question” (3) and, consequently, “identified diseased” in statistical evaluation. The specifity for B-mode sonography was at 100%. The cause for the excellent performance of B-mode sonography may have been that the anterior wall of the maxillary sinus is well to image in ultrasound. The air-containing maxillary sinus as such causes the sound to be extinguished so that pathological process-
es at the back wall of the maxillary sinus, e.g., are hard to image or not to image, at all. But the existence of isolated pathological areas at the back part of the maxillary sinus with a healthy anterior segment of the sinus which is fully air filled is not common in an acute maxillary infection. This fact explains the high specifity of B-mode sonography. Regarding all examination methods, the sensitivity for a diseased maxillary sinus (sinusitis acuta) was at 100%. Radiological imaging procedures represent the sinusitis acuta syndrome as a circular swelling of the mucous membrane, partly with fluid accumulation in the maxillary sinus. By ultrasound examination (Amode and B-mode sonography) an extended anterior
Near Infrared Transillumination in Acute Maxillary Sinusitis
wall echo can be identified. In case of fluid accumulation, a back wall echo can be represented, too. Mann (8) reported in an analysis of A-scan sonography that less distinctive swellings of the mucous membrane at the bottom of maxillary and frontal sinuses can hardly and secretion amounts below 1 ml cannot be detected, at all. Not stating whether or not the respective cases referred to acute or chronic inflammations, he reported that as a result 8.1% of sinusitis maxillaris cases were misinterpreted as healthy. This percentage corresponded to the value established by us for sinusitis chronica (10%). In his study on patients suffering from asthma and chronic sinusitis maxillaris Pfister (10) reported on a 22.2% specifity and a 70% sensivity when applying A-scan sonography. However, the examiners had no previous patient data. Due to the large number of falsely positive examination results, Pfister considers A-scan sonography to be unsuitable as screening procedure. Literature provides IRD-related sensivity and specifity data only for diagnosis of female breast diseases. Marshall (9) found a diagnostic specifity of 96–99% and a sensivity of 77% when examining the female breast with infrared light. A-mode sonography is a one-dimensional imaging procedure, which permits a differential diagnosis to be made only through indirect signs and to a very limited extent. The examination results can only be clearly evaluated if the individual ultrasonic echoes are far away from each other. If, however, there are various interfaces at a close distance to each other, the evaluation becomes very difficult. Different to A-mode sonography, infrared diaphanoscopy generates a two-dimensional image. Since the contour of the patient’s head can be represented, the location of the detected scattered light pattern is clearly described. Thus, standardisation has been achieved, to some extent. Error sources can easily be identified and considered when evaluating any findings, which the examiner has not made on his own (scattered light reflections, applicator positioning). Positioning and alignment of the sound head for A-mode sonography is not documented in the one-dimensional findings. This may complicate statements on the progress of a disease in follow-up examinations. In case of NIR diaphanoscopy, the examiner can generate an image of equal standard without having knowledge of previous findings.
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But actually it is not possible to make a differential diagnosis using infrared diaphanoscopy. The actual sensitivity of this procedure could not be elucidated in this study. This means that we could not find out to which minimum changes in a state can be detected by infrared diaphanoscopy. This should be subject to further research and will require both more efficient examination instruments and a way to quanitfy the findings. More recent investigations in the field of indicate that infrared diaphanoscopy is a very reasonable supplementary procedure for acquiring information on early-stage inflammatory rheumatoid changes (11). Interestingly the investigations indicate that the method responds already to slight changes in the functional state that cannot be recorded by other imaging procedures. Therefore, infrared diaphanoscopy may play a role as screening method in the future. For otorhinolaryngology, too, NIR transillumination with its very short examination time seems to be applicable in daily routine for various tasks: 1. It could be used as screening method in order to provide information as to whether or not a maxillary or frontal sinus is diseased or healthy. 2. This could also be of major assistance in the search for foci (e.g. dermatological diseases). In case of a bland chronic sinusitis maxillaris, the disease would be indicated by a reduced scattered light pattern. In this connection, it could be a first approach in the search for foci in case of fever of unknown origin in intubated patients at intensive care units, too, because these patients are difficult to move and could be subjected to IRD at their bedside at minor expense. 3. Another field of application is the examination of children. In case of diseases such as mucoviscidosis an involvement of the paranasal sinuses could be possible. 4. Pregnant women can be subjected to IRD without any risk. 5. The progress of diseases and convalescences of acute inflammations of maxillary or frontal sinuses can be documented by IRD, with x-rays partly no longer being necessary. 6. Further clinical studies have to clarify whether IRD may contribute to early detection of an involvement of the paranasal sinus system in allergic and asthmatic persons.
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As already mentioned, a differential diagnosis cannot be made with NIR transillumination. Nevertheless, those indications should be determined, for which an NIR transillumination application seems reasonable. Considering the sensitivity of the infrared diaphanoscopy system, the inflammatory diseases are clearly in the focus of attention, above all the acute sinusitis maxillaries and frontalis, followed by the chronic variant. Near infrared diaphanoscopy plays a minor role in fracture diagnosis. Here, the attention is primarily focused on the indication for reconstructive surgery, which requires a clear structural bone representation. If a maxillary or frontal sinus is fractured, NIR transillumination responds by absorption at the extravasal blood (haematosinus) with a strong attenuation or even absence of the scattered light pattern. Near infrared diaphanoscopy – up to now – is still unsuitable for tumour diagnostics.
Die NIR-Diaphanoskopie bei der akuten Sinusitis maxillaris: Theoretischer Hintergrund – Klinische Applikation – Diagnostische Möglichkeiten und Grenzen
Unter den entzündlichen Erkrankungen der Nasennebenhöhlen zeigt die akute Sinusitis maxillaris eine besonders hohe Inzidenz. Als sekundär bakteriell-purulente Entzündung entsteht sie häufig konkomitant oder im Nachgang einer banalen primär viralen Rhinitis oder Rhinosinusitis, wenn es zu Schleimhautschwellungen und Ventilations- und Drainagestörungen im Bereich der osteomeatalen Einheit des mittleren Nasengangs kommt. In den nachgeschalteten paranasalen Sinus frontalis, ethmoidalis und maxillaris kommt die korrekte Ventilation zum Erliegen, eine bakterielle Superinfektion der Mukosa entsteht. Im nicht diagnostizierten oder unbehandelten Fall kann dies in ernsthaften Komplikationen an Orbita, fazialen Weichteilen und Endocranium gipfeln. Neben der HNO-ärzlichen Untersuchung bei der akuten Sinusitis maxillaris, die durch endoskopische Verfahren deutlich verbessert und verfeinert werden konnte, bleibt jedoch die direkte visuelle Inspektion der Kieferhöhle zur Diagnosefindung in der Regel unmöglich, da die akut mukosal obstruierten natürlichen Ostien eine Endoskoppassage nicht zulassen. Goldstandard zur Diagnosesicherung ist daher bis heute die Bildgebung mit Röntgenstrahlung und – mit Einschränkungen – die Sonographie. Angeregt von vielversprechenden Grundlagenuntersuchungen zu den Interaktionen von Lichtstrahlung ausgesuchter Spektralbereiche mit biologischen Geweben, griffen wir das Prinzip der Diaphanoskopie der Kieferhöhlen wieder auf und konzipierten eine zweidimensional abbildende Meßeinrichtung für die Diagnostik von Erkrankungen der Nasennebenhöhlen. Dabei ersetzten
wir die Kaltlicht- Diaphanoskopie durch eine Transillumination mit Photonen aus dem Spektralbereich des nahen Infrarot (NIR). Im sog. “optischen Fenster” liegt eine deutlich verminderte Absorption von Licht in biologischem Gewebe vor, so dass Körperhöhlen durchleuchtet und das Streulicht in hervorragender Weise zur Diagnostik verwendet werden kann. Unsere klinisch kontrollierte Studie erbrachte kategorisierbare Transilluminationsaufnahmen, die eine gute positive Korrelation zu den traditionell bildgebenden Verfahren zeigten. Mit der NIRDiaphanoskopie steht also ein abbildendes System zur Verfügung, welches die Fähigkeit eines in-vivo-Stoffwechselmonitorings im betrachteten anatomischen Areal besitzt.
Schlüsselwörter Sinusitis, Kaltlicht-Diaphanoskopie, Infrarot-Diaphanoskopie, Bildgebende Diagnostik, Infrarot-Spektrum, Oto-Rhino-Laryngologie
References 1. ALBEGGER K: Unspezifische Entzündungen der Nasennebenhöhlen und dentogene Entzündungen. In: Kastenbauer E (Hrsg.), Oto-Rhino-Laryngologie in Klinik und Praxis, Thieme Verlag Stuttgart, New York 1992, S. 216 2. Beuthan J: Grundlagenuntersuchungen zur Infrarot-Diaphanoskopie. Diss. MMA (Standort: Deutsche Bücherei Leipzig) 1982 3. Beuthan J, Müller G, Minet O, Prapavat V: IR-Diaphanoscopy in medicine. In: Medical Optical Tomography-Functional Imaging and Monitoring. Eds.: Müller G, Chance B, SPIE Institute Series Vol. IS11, SPIE-Press, Washington 1993 4. Cutler M: Transillumination as an aid in the diagnosis of breast lesions. With special reference to ist value in cases of bleeding nipple. J Surg Gynecol Obstet 48: 721–729 (1929) 5. Czembirek H, Frühwald F, Gritzmann N (Hrsg): Kopf-HalsSonographie. Springer Verlag, Wien, New York 1988 6. Feldmann H: Die Geschichte der Diaphanoskopie. LaryngRhino-Otol 77: 297–304 (1998) 7. Gerber PH: Ein Doppeldiaphanoskop zur Durchleuchtung der Stirnhöhlen. Dtsch med Wschr 26: 177–180 (1900) 8. Mann, W.J.: Ultraschall im Kopf-Hals-Bereich. Springer Verlag, Berlin, Heidelberg 1984 9. Marshall V, Williams DC, Smith KD: Diaphanoscopy as a Means of Detecting Breast Cancer. Radiology 150: 339–343 (1984) 10. Pfister R, Lütolf M, Schapowal A, Glatte B, Schmitz M, Menz G: Screening for sinus disease in patients with asthma: A computed tomography-controlled comparison of A-mode ultrasonography and standard radiography. J Allergy Clin Immunol 5: 804–809 (1994) 11. Prapavat V: Anwendung der experimentellen Systemanalyse zur Informationsgewinnung aus Streulicht im Frühstadium entzündlich-rheumatischer Veränderungen. Hrsg.: Müller, Berlien, ecomed Verlag Berlin, Bd.18, Fortschritte in der Lasermedizin, Diss. (1998)
12. Roggan A, Minet O, Schroeder C, Müller G: Measurements of optical tissue properties using integrating shpere technique. In: Medical Optical Tomography-Functional Imaging and Monitoring. Eds.: Müller G, Chance B, SPIE Institute Series Vol. IS11, SPIE-Press, Washington 1993, 149–166 13. Vohsen C: Die Durchleuchtung der Oberkieferhöhle und Stirnhöhle und deren Erkrankungen. Berl klin Wschr 27: 1060–1063 (1890) 14. Vohsen C: Methodik der Durchleuchtung von Oberkieferund Stirnhöhle. Berl klin Wschr 45: 1311–1312 (1908) 15. Voltolini R: Die Krankheiten der Nase und des Nasenrachenraums nebst einer Abhandlung über Elektrolyse für Specialisten, Chirurgen und praktische Aerzte. Morgenstern, Breslau (1888)
Correspondence address: Privatdozentin Dr. med. habil. Marietta Hopf, Charité – Universitätsmedizin Berlin, Universitäts-HNO-Klinik Campus Benjamin Franklin, Hindenburgdamm 30, D-12200 Berlin, Germany Tel.: ++49-30-825 86 36; Fax: ++49-30-897 287 50; e-mail: [email protected]
Near Infrared Transillumination in Acute Maxillary Sinusitis: Theoretical Background – Clinical Application – Diagnostic Potential – Limitations MARIETTA HOPF1 and JÜRGEN U. G. HOPF1,2 1
Department of Otorhinolaryngolgy, Head and Neck Surgery, University Medical Center, Campus Benjamin Franklin (Head: Prof. Dr. H. Scherer), Charité Universitätsmedizin Berlin, Germany 2 “HNO am Roseneck”, Berlin, Germany
Submitted: June 2003 · Accepted: July 2003
Summary Among the inflammatory diseases of the paranasal sinuses in man the acute maxillary sinusitis shows a particularily high incidence. Mostly emerging from a primarily viral rhinitis or rhinosinusitis the paranasal inflammation secondarily becomes purulent, if mucosal swellings and drainage disorders in the osteomeatal unit of the middle nasal meatus persist to be. The insufficient ventilation of the related paranasal sinuses – sinus maxillaris, sinus ethmoidalis and sinus frontalis – gives rise to a bacterial superinfection of the mucosa. In cases where the right diagnosis has not been found early enough or the acute sinusitis stays untreated the situation can culminate in serious complications to the orbit, to the facial soft tissues and even to the endocranium possibly leaving continual damages to the patient’ health. Despite the otorhinolaryngologic examination significantly improved and refined by endo- and transnasal endoscopy, the direct visual inspection of the maxillary sinus for diagnostic reasons is normally not possible. This refers to the very small natural orifice of the maxillary sinus and the mucosal swellings which block the endoscope from penetrating into the middle nasal meatus as well as the sinus. Therefore plain film X-ray-imaging and sonography – in minor cases and in the follow up period – represent the gold standard for making the diagnosis of sinusitis up to now. Stimulated by promising basic investigations on the small spectrum light transillumination of biological tissues with selected wavelengths we re-adopted the principle of diaphanoscopy for diagnostic imaging of the maxillary sinuses. For its clinical application we designed a measuring setup where we replaced “cold (white) light transillumination” of the sinus by diaphanoscopy with photons of the near infra red spectrum of light (NIR). In this narrow part of the spectrum ranging from a wavelength of 650 to 1100 nm – the so-called ‘optical window` – the incidence of photon scattering is much higher than absorption events by the tissue. This biophysical finding renders it possible in an excellent manner to utilize NIR-photons for the transillumination of body cavities and their detection in order to create a two-dimensional imaging. Our clinically controlled study supplied clearly categorizable NIR-diaphanoscopic images of different stages of an acute maxillary sinusitis showing a good positive correlation to traditional plain radiography and computer tomography (CT scan-imaging). Additionally NIR-diaphanoscopy is not only a system of morphological imaging but also of biomonitoring in the considered anatomical area.
Key words Sinusitis, cold light diaphanoscopy, Near IR diaphanoscopy, diagnostic imaging, infrared spectrum, otorhinolaryngology 1615-1615/03/18/03-217 $ 15.00/0
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Introduction Acute sinusitis maxillaris is a widely spread disease, although exact data on its incidence are missing in the relevant literature. For sinusitis maxillaris chronica, the reported incidence ranges between 5 and 25% (1). Etiologically, acute sinusitis maxillaris mainly develops within an acute rhinitis, with a primarily viral infection entailing a secondarily bacterial purulent rhinositis. Pathophysiologically, the functional obstruction of the natural junctions of the main nasal cavity and the maxillary sinus by swelling of the mucosa leads to ischesis and inflammations of the mucosa in the affected sinus. The otolaryngologist’s diagnosis is based primarily on the patient’s history and the inspection of the main nasal cavity (rhinoscopia anterior and posterior). Redness, swelling and accumulation of pus in the middle meatus of the nose indicate an acute inflammation. The small diameter of only a few millimetres makes a direct endoscopic inspection of the maxillary sinus through its natural ostium via the middle meatus of the nose impossible in most cases. Another indication is obtained by digital palpation of the foramen infraorbitale at the bony facial wall of the maxillary sinus. The irritation of the trigeminal infraorbital nerve leaving its bony channel here causes pain on pressure.
Diagnostic Imaging In diagnostic imaging the plain film X-ray in occipito-mental ray trajectory (om) according to Waters is the standard tool for maxillary sinus evaluation. It serves for an exact representation of the anatomic structures prior to any invasive therapeutic strategies to the maxillary sinuses. An empyema in example may require a sharp needle puncture of the sinus through the inferior nasal meatus and an antrum rinsing for pus evacuation. For this purpose, an X-ray image according to Waters which shows the individual empyema’s size and location is indispensable. If the acute maxillary sinusitis spreads to the surrounding anatomic structures of neighbouring organs, complications like an orbital phlegmon will occur. In such case, further diagnostic imaging (CT, MRT) is absolutely necessary.
For many ENT specialists, sonography of the maxillary sinuses is the diagnostic tool of choice to confirm their tentative diagnosis. The patient’s pain and the risk of serious complications compel the attending physician to initiate an adequate medication or even surgery, without delay. The ultrasonic examination is well suited for this purpose in initial stages of the disease. It can be done quickly and at favourable cost and be repeated as often as required. For such ultrasonic examinations, the ENT specialist prefers the B mode sonography over the A mode sonography. For the A mode sonography the signal of the acoustic wave is recorded in the form of an one-dimensional derivation as an echogram only. The conclusiveness of this ultrasonic examination is limited, however, because the gain of signals is considerably impeded if air is still inside of the sinus. The use a two-dimensional signal gain (B-mode sonography) reveals much more detail information on the target, is much easier interpretable but also impeded by air that leads to total signal extinction making pathologic processes “behind the air shield” difficult or not to image, at all. Nevertheless, sonography has become the established routine procedure in modern rhinology. Attempts to develop an easy-to-apply reliable routine diagnostic procedure in addition to or even replacing sonography, led from the historical endeavours (7, 13, 14, 15).to the use of photons for the transillumination of the paranasal sinuses (6). Thus, quantifiable stray light information can be obtained which allow the state of the maxillary sinus to be evaluated. The knowledge that • light of NIR wavelength has a specifically high penetration depth into biological tissue and that • light of the NIR spectral range responds very sensitively to even tiny tissue changes by absorption and scattering make the near infrared transillumination a promising diagnostic possibility. The goal of transillumination procedures was the imaging of inner structures of the human body. In 1929 Cutler (4) reported on the transillumination of the female breast to diagnose lesions with this method. He took advantage of the different absorption coefficients of tumour and healthy breast tissue. Scattering was neglected as a disturbing effect. Transmission measurements showed that an optical win-
Near Infrared Transillumination in Acute Maxillary Sinusitis
dow between 600 and 1300 nm exists in tissue. Olsen et al. used this procedure for cancer screening in female breasts. Although their pictures were diffuse and hazy because of light scattering they could detect 95% of the mammae tumours examined. First examination of tissue parameters in the near infrared in 1982 by Beuthan (2) showed the way for the infrared trasillumination in the diagnosis of sinusitis by using the scattered radiation for diagnosis.
In general the transmission is determined by: T = Iout/Iin (Iout = irradiated light intensity, Iin = light intensity after transillumination of a layer) In time integrated imaging all photons (mainly scattered photons) can be used for detection: Iout = Iin · exp [ – µ effd], µ eff = [3µa (µ a + µ s)]1/2 (µ eff = efficient scattering coefficient, d = layer thickness) In this diffusion approximation the transmission is about 6 × 10–10 and can be detected by standard sensors.
Theoretical background The inspection of parts of the human body with the help of optical instruments has been used in medical diagnosis for more than a century, although its application has been limited, so far. In recent years however extended knowledge of tissue optics (absorption/ scattering) and improved sensor technology offered new solutions to this problem. The most important condition for the realisation of the time integrated IR- transillumination is the knowledge of the optical tissue parameters. The scattering coefficient µ s, the absorption coefficient µ a and the anisotropy factor g of the tissues involved in transillumination limit the use of this method. In general, in the range of the near infrared spectra the scattering coefficient is one order of magnitude larger than the absorption coefficient (12): It is:
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Fig. 1. Scattering of light irradiating biological tissue.
µs > µa
There will be an excessive intensity of light by scattering in tissue (Fig. 1), which will be particularly high in the hollow organs including the paranasal sinuses (factor 7). The reduced scattering coefficient µ s‘ includes the anisotropy factor g: µs‘ = µs (1 – g) The anisotropy factor g indicates the preferred propagation direction of scattering and may range from values of g = –1 (backward scattering) via g = 0 (isotropic scattering) to g = +1 (forward scattering) (Fig. 2). In all biological tissue the anisotropy factor g has a high value (e.g. 0.93 to 0.98) in the near infrared, e.g. tissue shows a high degree of forward scattering.
Fig. 2. Anisotropy factor g, backward scattering, isotropic and forward scattering (modified according to Roggan (1997).
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Fig. 3. Distribution of the scattering of photons in a tissue layer (Beuthan 1993) (layer thickness = 10 mm, µ a = 0.005 mm–1, µ s= 10 mm–1, g = 0.07, 106 photons) 30 times of the main free path lengths.
Infrared-imaging is used in regions of the body in which (in relation to the main free path length) thick tissue layers are transilluminated. We have to deal with layer thicknesses of at least 30 times of the main free path length. In this case the “direction memory” of the photons is considerable spread. For illustration Fig. 3 shows the result of a Monte Carlo simulation. A point light source is put orthogonally on an infinitely expanded tissue layer of 10 mm in thickness (µ a = 0.05 mm–1, µ s = 10 mm–1, g = 0.97, 106 photons are irradiated into the tissue). The simulation shows among other things that on the other side of the layer the majority of the escaping photons were scattered 130 times or more. Only one photon was scattered only 77 times. Therefore, it is necessary to consider two situations when looking at infrared imaging: A: µ s varies with the metabolism of the tissue (diseased/healthy). In this functional variation the diaphanoscopical procedure has to react to the changes of scattered light. Such a situation can be found when transilluminating the maxillary sinuses. B: µ‘ s1 𠵑 s2 or/and µ a1 π µ a2. This situation is given in blood vessels in all kinds of tissue and in thin layers of very different optical parameters (i.e. bone cladded by connective tissue). If in
this case partial congruences appear in the direction of the projection and the contrast is sufficient for the detection of simple structures. Especially the combination of bone and other tissue is very important for the endoscopic diagnosis in the head. In near infrared imaging the paranasal sinuses are penetrated by electromagnetic waves of the near infrared spectrum. The emergent radiation can be measured by means of a NIR camera thus providing scattering light data on the transilluminated region. These data can be represented as a two-dimensional picture and then evaluated. Consequently, infrared imaging is a transmitter-receiver system and suitable for medical diagnostic imaging. In sinusitis changes of the tissue are observed in the area of the paranasal sinuses. By intensified blood supply of the mucous membranes the absorption of the tissue increases in the near infrared spectrum. At the same time layers with enhanced scattering are growing. In the extreme case the inflamed cavity is filled with fluid. This process corresponds to the situation described in A. µ s can increase by one order of magnitude. Therefore, the changes caused can be easily detected. Fig. 4 shows the principal sketch, a practicable set-up and the examination of the infrared imaging technique in the diagnosis of sinusitis.
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The near infrared irradiation (650–1100 nm) of a forceps-like applicator positioned in the mouth penetrates the jaw bone to reach the right and left maxillary sinus simultaneously. Hereby the radiation is scattered in relation to the state of illness (the change of absorption is negligible). The detection of the scattered radiation can be compared with the measuring situation at an integrated sphere on which a measuring opening is closed with a semi-opaque membrane. In the given case this membrane is the thin bone of the orbital floor. At the boundary eye/orbita ground parts of the emergent scattered radiation can be visualised on the surface of the face in the infraorbital region (Fig. 5). In comparison to the imaging situation during plain radiography Fig. 6 shows the light pattern of near infrared imaging.
Fig. 5. Schematic drawing of a sagittal section of the head. The arrows show the direction of the near infrared irradiation. After penetration of the maxillary sinus (1+2) the scattered radiation in the direction of the face can be visualised in the area between the bulbus oculi and the orbital floor.
Fig. 4. Principal sketch of infrared imaging technique and the demonstration of the examination procedure. Near infrared radiation is administered through an applicator in the mouth. The scattered light is detected by a filtered CCD camera and can be visualised on a monitor. For documentation a video printer or digitalisation of the image is possible.
Fig. 6. Comparison (X-ray/Near Infrared Imaging) of projection and diagnostic findings in principle
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Material and Methods Diagnostic Imaging Procedures Near infrared imaging of the sinuses The maxillary sinuses were represented using a near infrared imaging system with integrated monitor. The related findings (in the form of scattered light projections upon the contour of the face) of each patient were photo-documented by means of a video printer. A-mode sonography of the paranasal sinuses For A-mode sonography of the paranasal sinuses a Homoth echoscope with an Atmos 3.5 MHz sonic head in the classical examination technique was used (8). The findings were documented separately for each sinus and side through curve plotting of a “frozen” representative monitor image. The method is suitable for representing fluid- and soft-tissue proof structures in the maxillary sinuses’ region. B-mode sonography of the paranasal sinuses B-mode sonography of the paranasal sinuses was done with a Picker CS 9000 one each 7.5 MHz linear and 5 MHz sector scanning sonic head in the classical examination technique with and without water path (5, 8). The findings were documented separately for each side and sinus by means of a polaroid instant photography or video print of a “frozen” representative and informative monitor image.
Classical radiographs of the paranasal sinuses For routine symptom-related diagnostic radiography of pathological changes of the paranasal sinuses we applied the two conventional settings in the occipitofrontal and occipito-mental ray trajectory. Computer tomography of the paranasal sinuses Next to nuclear magnetic resonance imaging (MRI), computer tomography (CT) happens to be the most reliable and most sensitive imaging procedure for regular anatomic and pathological findings. We had computer tomograms in the bone and soft-tissue window, with and without contrast medium. Lamination was made in coronar and axial section planes of layer thicknesses ranging from 2 to 5 mm.
Near-Infrared Diaphanoscopy The analysis was based on the evaluation of the infraorbital scattered light corona above the maxillary sinus. For the correct diagnosis it is necessary to examine some hundred patients. In all cases of no pathological findings in the maxillary sinuses we could detect a typical near infrared diaphanoscopic image as shown in Fig. 7. The scattered light appears as a “sickle shaped figure” with clear light in the region of the orbital floor. In cases of sinusitis, the sickle shaped figure was not found. The scattered light decreased or was not visible (Fig. 8). For documentation we defined a Valuation-Index (VI) from one to four and additionally a statement if both sides appear symmetric or asymmetric in light or figure as shown in Table 1: Table 1. Valuation-Index (VI) for near infrared imaging of maxillary sinuses. • • • • • •
VI 1 – sickle shaped figure VI 2 – reduced scattering light VI 3 – scarcely scattering light VI 4 – no scattering light A – symmetric B – asymmetric
Examination methods for clinical evaluation
Fig. 7. Normal near infrared imaging of maxillary sinuses.
The clinical evaluation of the new near infrared imaging procedure was based on the following examinations and documentation:
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• • • • •
general and symptom-related patient’s history basic clinical examination by the ENT specialist NIR transillumination of the maxillary sinuses A-mode sonography of the maxillary sinuses B-mode sonography of the maxillary sinuses (with and without water path) • plain X-ray radiography • computer tomography in axial and/or coronary layers
Course of examination, documentation and statistical evaluation Patient’s history, clinical ENT status, endoscopy, infrared diaphanoscopy, sonography were taken or made by different physicians of the University ENT department, with the near infrared imaging, A-mode and B-mode sonographies being evaluated by different physicians who had no knowledge of the other examination results. This course guaranteed an unprejudiced evaluation. The radiological procedures (plain X-ray radiography and computer tomography) were evaluated by senior specialists of the University Radiological Department. For statistical computation of the sensivities and specifities we used standard computer software.
Number of patients examined For clinical evaluation of NIR transillumination, we received 400 maxillary sinus findings (of 200 pa-
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tients), in total. All these findings had been made in our ENT Department. The findings were found suitable if radiographs and a computer tomography of the paranasal sinuses had been made. The patients had consulted the ENT Department because of a disease or in order to exclude an ENT disease. A total of 379 maxillary sinuses were included in the study, 260 of which had been diagnosed as healthy while the remaining 119 showed the clinical diagnosis of an acute sinusitis. In 84 patients bilaterally healthy maxillary sinuses were found, 92 patients suffered from unilateral acute sinusitis, with the respective opposite side being healthy, 13 patients were found to have contracted bilateral acute sinusitis maxillaris, and in one patient a unilateral sinusitis acuta and a chronic polypous sinusitis on the opposite side were found. To simplify the procedure, the maxillary sinus findings were evaluated not in pairs, but individually independent of the fact whether or not the opposite side was healthy or affected, too. The statistical evaluation included only those patients for whom all the afore-mentioned examinations including the imaging procedures had been completely documented. Having evaluated all the findings (history, ENT status, endoscopy, A-mode and B-mode sonography, plain X ray radiography of the paranasal sinus and computer tomography), the maxillary sinuses were categorised into the groups “healthy” or “diseased”.
Fig. 8. Near infrared imaging of maxillary sinuses in case of acute maxillary sinusitis on one site, endoscopic view of the nasal cavity with purulent secretion.
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The youngest patient was of an age of 6 years, the oldest patient was 73 years of age. The average age was 33 years, the median was 31.5 years. The study extended to 112 female and 78 male patients.
Results We examined 379 maxillary sinuses of 190 patients. All of them have had a computer tomography in coro-
nary and/or axial sections as well as standard plain Xrays according to Waters of the paranasal sinuses and additionally an A-mode and B-mode sonography. Computer tomography (Fig. 9) in combination with the history, the ENT-examination and the patient’s symptoms were our gold standard for statistical evaluation of near infrared imaging. 260 sinuses were healthy. In 119 maxillary sinuses we found an acute maxillary sinusitis. In 11% the sinus was totally filled, in 36% the sinus was partly filled with fluid.
Fig. 9. Clinically acute maxillary sinusitis, identified by different diagnostic procedures: NIR transillumination (A), plain radiography (B), A-mode sonography (C), computer tomography (D), B-mode sonography (E).
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In cases of healthy sinus or acute maxillary sinusitis the examination results of each imaging procedure, each analyzed from another physician were categorised into five groups (Table 2): Table 2. Analysis and interpretation of the imaging results of all methods used for diagnosis of the maxillary sinuses. Category 1: “sure healthy” Category 2: “healthy” Category 3: “healthy/pathologic in question” Category 4: “pathologic” Category 5: “sure pathologic”
Healthy maxillary sinuses The results for healthy maxillary sinuses (n = 260) are shown in (Table 3): Table 3. Clinically healthy maxillary sinuses, identified as healthy or diseased by different diagnostic imaging procedures. Diagnosis: Healthy Maxillary Sinuses (n = 260)
Identified as healthy (Category 1–2)
Identified as diseased (Category 3–5)
Computer Tomography Plain X-ray Radiography B-mode Sonography A-mode Sonography NIR Transillumination
260 (100%) 255 (98.1%) 260 (100%) 259 (99.6%) 259 (99.6%)
0% 5 (1.9%) 0% 1 (0.4%) 1 (0.4%)
Applying NIR transillumination 246 maxillary sinuses (94.6%) were found to be in the category 1 “sure healthy”, 13 maxillary sinuses (5.0%) in the category 2 “healthy”, und 1 sinus (0.4%) in the category 3 “healthy/pathologic in question” and none in the category 4 “pathologic” or category 5 “sure pathologic” In comparison • with the A-mode sonography 259 maxillary sinuses (99.6%) were in the category 1 “sure healthy”, and 1 sinus (0.4%) in the category 3 “healthy/pathologic in question” and none in the category 4 “pathologic” or category 5 “sure pathologic” • with the B-mode sonography 244 maxillary sinuses (93.8%) were in the category 1 “sure healthy”, 16 maxillary sinuses (6.2%) in the
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category 2 “healthy”, none the category 3 “healthy/ pathologic in question” and none in the category 4“pathologic” or category 5 “sure pathologic” • with the plain radiography of the paranasal sinuses 255 maxillary sinuses (98.1%) were in the category 1 “sure healthy” and 5 maxillary sinuses (1.9%) in the category 3 “healthy/pathologic in question”. • and with computer tomography of the paranasal sinuses 260 maxillary sinuses (100%) in the category 1 “sure healthy” and no maxillary sinus in the other categories. In order to determine the specifity, all maxillary sinuses of the validation indices “sure healthy” (1) and “healthy” (2) were categorised into the “identified as being healthy” group, while all maxillary sinuses of the validation indices “healthy/pathologic in question” (3), “pathologic” (4) or “sure pathologic” (5) were classified into the “identified as being diseased” group. With computer tomography and B-mode sonography all healthy maxillary sinuses had been actually identified as being healthy. By means of plain radiography of the paranasal sinuses, 5 healthy maxillary sinuses (1.9%) were identified as “healthy/pathologic in question” (category 3), and so was one each (0.4%) healthy maxillary sinus by means of NIR transillumination, A-mode and B-mode sonographies, Consequently, these maxillary sinuses were categorised into the “identified as being diseased” group.
Acute maxillary sinusitis The results for acute maxillary sinusitis (n = 119) are shown in (Table 4): Table 4. Clinical diagnosis “acute maxillary sinusitis”: all maxillary sinuses were classified by the different diagnostic procedures into the group “identified as diseased“. Diagnosis: Acute Maxillary Sinusitis (n = 119)
Recognized as diseased (Category 3–5)
Computer Tomography Plain X-ray Radiography B-mode Sonography A-mode Sonography NIR Transillumination
119 (100%) 119 (100%) 119 (100%) 119 (100%) 119 (100%)
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With NIR transillumination 9 maxillary sinuses (7.6%) were in the category 3 “healthy/pathologic in question”, 66 (55.5%) in the category 4 “pathologic” and 44 (36.9%) in the category 5 “sure pathologic”. In comparison • with the A-mode sonography 4 maxillary sinuses (3.4%) were in the category 3 “healthy/pathologic in question”, 74 (62.2%) in the category 4 “pathologic” and 41 (34.5%) in the category 5 “sure pathologic”. • with the B-mode sonography 63 maxillary sinuses (52.9%) were in the category 4 “pathologic” and 56 (47.1%) in the category 5 “sure pathologic”. • with the plain radiography of the paranasal sinuses and CT-Scan all 119 maxillary sinuses (100%) were in the category category 5 “sure pathologic”. In all cases (119) of acute maxillary sinusitis the different diagnostic imaging procedures recognized a “diseased sinus” (Valuation Index 3–5), (Tab. 4).
Specifitiy and Sensitivity The statistical evaluation provided the results shown in Table 5. The specifity for identifying a healthy maxillary sinus was 99.6% in the case of near infrared diaphanoscopy and A-mode sonography. As for plain radiography of the paranasal sinuses, the specifity was less, namely 98.1%.
For B-mode sonography and computer tomography of the paranasal sinuses a 100% specifity was recorded. Each diseased maxillary sinus (n = 119) was identified as such by all examination methods including infrared diaphanoscopy. This corresponds to a 100% sensitivity for all methods.
Discussion Our studies on the system analysis and clinical evaluation showed that infrared diaphanoscopy can be applied for diagnostics in otolaryngology and considered a reasonable complement to other imaging procedures. On the contrary to other imaging procedures, the system does not measure the changes in the tissue layer thicknesses, but images changes in the tissue state based on metabolic processes. Even slight changes in the state, such as an hyperaemia of the paranasal sinus mucosa, result in an enhanced absorption and scattering of tissue photons and, consequently, in a reduced transillumination of the scattered light. Infrared diaphanoscopy detects the transillumination of infrared light of the maxillary sinus. In healthy maxillary sinuses, the emergent scattered light appears in the shape of an infraorbital light sickle. Diseased maxillary sinuses generate a different image, which is deformed and of reduced intensity. Infrared diaphanoscopy was developed by Beuthan (2, 3). Having found no references in literature, our clinical evaluation of the suitability of infrared radiation for application in paranasal sinuses diagnostics seems to be unprecedented.
Table 5. Specifity of the different diagnostic imaging procedures for healthy maxillary sinuses and sensitivity for acute maxillary sinusitis with 95%-Confidential-Interval (CI). Diagnostic imaging methods of the maxillary sinus
SPECIFITY Healthy maxillary sinuses (n = 260) Confidential-Interval CI (95%) · 100
SENSITIVITY Acute maxillary sinusitis (n = 119) Confidential-Interval CI (95%) · 100
Computer Tomography Plain X-ray Radiography B-mode Sonography A-mode Sonography NIR Transillumination
… 100% (99.99–100) … 98.1% (96.40–99.75) … 100% (99.99–100) … 99.6% (98.90–100) … 99.6% (98.90–100)
… 100% (99.99–100) … 100% (99.99–100) … 100% (99.99–100) … 100% (99.99–100) … 100% (99.99–100)
Near Infrared Transillumination in Acute Maxillary Sinusitis
Among the issues most difficult to solve was the definition of valuation criteria for the unambiguous description and classification of infrared diaphanoscopy findings. For this purpose, the scattered light intensity had to be evaluated for its qualitative value. For this purpose, the reproducibility of “normal findings” had to be ensured by subjecting healthy people to a large number of examinations. Like for the A-scan and Bmode sonographies, both examination and evaluation should be done by the same physician because the material to be evaluated, i.e. the images, is but one component of the dynamic examination. Some specific experience is required in order to safely evaluate an infrared diaphanoscopy result, which applies to other imaging procedures, too. For infrared diaphanoscopy evaluation the following principles hold: 1. A healthy maxillary sinus shows a typically shaped infraorbital scattered light sickle of high scattered light intensity (Fig. 7). 2. In healthy state, the right and left maxillary sinuses are symmetrical to large extent, minor lateral differences are physiological (Fig. 7). 3. The light intensity, i.e. the scattered light corona, is larger with healthy maxillary sinuses than with acute sinusitis (Fig. 8). 4. In case of people with unilateral or bilateral maxillary sinus disease this scattered light sickle symmetry is not achieved. It always differs from that of healthy maxillary sinuses (Fig. 8). 5. The operation of this examination instrument including the selection of the output light intensity and positioning of the applicator determine the image quality and should be left to an experienced examiner. 6. The evaluation principle for infrared diaphanoscopy is based on the evaluation of different scattered light intensities above each paranasal sinus (1 – normal transillumination, 2 – reduced transillumination, 3 – hard to recognize , 4 – no representation) with data whether or not a lateral difference existed. Actually, however, infrared diaphanoscopy does not permit a differential diagnosis. Consequently, it does by no means replace the established radiological procedures.
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The data are then entered into an evaluation scheme (5 groups, namely “sure healthy” – 1; “healthy” – 2, “healthy/pathologic in question” – 3, “pathologic” – 4, “sure pathologic” – 5). If a paranasal sinus is diagnosed as being diseased, the differential diagnosis can partly be derived from the patient’s history and symptomatology. Thus it is not necessary in each and every case to take further diagnostic steps in order to start an adequate therapy. This refers particularly to large part of sinusitis acuta. In such a case, follow-ups to evaluate the therapeutic result are mostly sufficient. If the scattered light is initially missing or drastically reduced, an increasing scattering light intensity above the respective paranasal sinus indicates the therapeutic result (Fig. 10 follow-up). Comprising all usual examination findings (endoscopy, intraoperative findings) and the computer tomography findings (being the gold standard of the imaging techniques) the clinical diagnosis formed the gold standard for the statistical evaluation. For statistical evaluation, the findings were classified either “identified as healthy” or “identified as diseased”, separately for each imaging procedure. The “healthy” group included all paranasal sinuses, which had been found “sure healthy” and “healthy”. The paranasal sinuses found “healthy/pathologic in question”, “pathologic” and “sure pathologic” were classified into the “diseased” group. The evaluation of all imaging procedures is closely tied to the examiner’s subjective component, which correlates with the physician’s rich experience. In case of radiographs or CT images evaluated by radiologists or ENT specialists, e.g., discrepancies may occur depending on their specific experience, which, in turn, may lead to different diagnoses. Bearing this in mind and knowing the patient’s history, each examination was made or evaluated by that specialist who had the largest experience. All radiological findings (x-ray and CT-scan) were evaluated by the radiologist, the ultrasonic findings by the otolaryngologist and the IRD findings by the authors themselves. The establishment of a new diagnostic method is not justified unless it is at least as good as existing procedures and involves advantages in application or cost. When statistically evaluating the infrared diaphanoscopy in clinical use on 260 healthy maxillary sinuses, the specifity was found to be 99.6%. This means that IRD was equally good as A-mode sono-
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Fig. 10. Follow up of NIR transillumination in maxillary sinusitis: A: day of diagnosis, B: after 8 days of medication, C: 15 days after therapy, D: 22 days after diagnosis, E: pathological findings in the plain radiography at the day of diagnosis, F: computer tomography 6 weeks after diagnosis of acute maxillary sinusitis.
graphy and with a 98.1% specifity even superior to paranasal sinus radiography. Radiography may have been inferior to NIR-transillumination because of its bad recording technique with other anatomical structures interfering. This would explain that 1.9% of the healthy maxillary sinuses had been classified “healthy/pathologic in question” (3) and, consequently, “identified diseased” in statistical evaluation. The specifity for B-mode sonography was at 100%. The cause for the excellent performance of B-mode sonography may have been that the anterior wall of the maxillary sinus is well to image in ultrasound. The air-containing maxillary sinus as such causes the sound to be extinguished so that pathological process-
es at the back wall of the maxillary sinus, e.g., are hard to image or not to image, at all. But the existence of isolated pathological areas at the back part of the maxillary sinus with a healthy anterior segment of the sinus which is fully air filled is not common in an acute maxillary infection. This fact explains the high specifity of B-mode sonography. Regarding all examination methods, the sensitivity for a diseased maxillary sinus (sinusitis acuta) was at 100%. Radiological imaging procedures represent the sinusitis acuta syndrome as a circular swelling of the mucous membrane, partly with fluid accumulation in the maxillary sinus. By ultrasound examination (Amode and B-mode sonography) an extended anterior
Near Infrared Transillumination in Acute Maxillary Sinusitis
wall echo can be identified. In case of fluid accumulation, a back wall echo can be represented, too. Mann (8) reported in an analysis of A-scan sonography that less distinctive swellings of the mucous membrane at the bottom of maxillary and frontal sinuses can hardly and secretion amounts below 1 ml cannot be detected, at all. Not stating whether or not the respective cases referred to acute or chronic inflammations, he reported that as a result 8.1% of sinusitis maxillaris cases were misinterpreted as healthy. This percentage corresponded to the value established by us for sinusitis chronica (10%). In his study on patients suffering from asthma and chronic sinusitis maxillaris Pfister (10) reported on a 22.2% specifity and a 70% sensivity when applying A-scan sonography. However, the examiners had no previous patient data. Due to the large number of falsely positive examination results, Pfister considers A-scan sonography to be unsuitable as screening procedure. Literature provides IRD-related sensivity and specifity data only for diagnosis of female breast diseases. Marshall (9) found a diagnostic specifity of 96–99% and a sensivity of 77% when examining the female breast with infrared light. A-mode sonography is a one-dimensional imaging procedure, which permits a differential diagnosis to be made only through indirect signs and to a very limited extent. The examination results can only be clearly evaluated if the individual ultrasonic echoes are far away from each other. If, however, there are various interfaces at a close distance to each other, the evaluation becomes very difficult. Different to A-mode sonography, infrared diaphanoscopy generates a two-dimensional image. Since the contour of the patient’s head can be represented, the location of the detected scattered light pattern is clearly described. Thus, standardisation has been achieved, to some extent. Error sources can easily be identified and considered when evaluating any findings, which the examiner has not made on his own (scattered light reflections, applicator positioning). Positioning and alignment of the sound head for A-mode sonography is not documented in the one-dimensional findings. This may complicate statements on the progress of a disease in follow-up examinations. In case of NIR diaphanoscopy, the examiner can generate an image of equal standard without having knowledge of previous findings.
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But actually it is not possible to make a differential diagnosis using infrared diaphanoscopy. The actual sensitivity of this procedure could not be elucidated in this study. This means that we could not find out to which minimum changes in a state can be detected by infrared diaphanoscopy. This should be subject to further research and will require both more efficient examination instruments and a way to quanitfy the findings. More recent investigations in the field of indicate that infrared diaphanoscopy is a very reasonable supplementary procedure for acquiring information on early-stage inflammatory rheumatoid changes (11). Interestingly the investigations indicate that the method responds already to slight changes in the functional state that cannot be recorded by other imaging procedures. Therefore, infrared diaphanoscopy may play a role as screening method in the future. For otorhinolaryngology, too, NIR transillumination with its very short examination time seems to be applicable in daily routine for various tasks: 1. It could be used as screening method in order to provide information as to whether or not a maxillary or frontal sinus is diseased or healthy. 2. This could also be of major assistance in the search for foci (e.g. dermatological diseases). In case of a bland chronic sinusitis maxillaris, the disease would be indicated by a reduced scattered light pattern. In this connection, it could be a first approach in the search for foci in case of fever of unknown origin in intubated patients at intensive care units, too, because these patients are difficult to move and could be subjected to IRD at their bedside at minor expense. 3. Another field of application is the examination of children. In case of diseases such as mucoviscidosis an involvement of the paranasal sinuses could be possible. 4. Pregnant women can be subjected to IRD without any risk. 5. The progress of diseases and convalescences of acute inflammations of maxillary or frontal sinuses can be documented by IRD, with x-rays partly no longer being necessary. 6. Further clinical studies have to clarify whether IRD may contribute to early detection of an involvement of the paranasal sinus system in allergic and asthmatic persons.
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As already mentioned, a differential diagnosis cannot be made with NIR transillumination. Nevertheless, those indications should be determined, for which an NIR transillumination application seems reasonable. Considering the sensitivity of the infrared diaphanoscopy system, the inflammatory diseases are clearly in the focus of attention, above all the acute sinusitis maxillaries and frontalis, followed by the chronic variant. Near infrared diaphanoscopy plays a minor role in fracture diagnosis. Here, the attention is primarily focused on the indication for reconstructive surgery, which requires a clear structural bone representation. If a maxillary or frontal sinus is fractured, NIR transillumination responds by absorption at the extravasal blood (haematosinus) with a strong attenuation or even absence of the scattered light pattern. Near infrared diaphanoscopy – up to now – is still unsuitable for tumour diagnostics.
Die NIR-Diaphanoskopie bei der akuten Sinusitis maxillaris: Theoretischer Hintergrund – Klinische Applikation – Diagnostische Möglichkeiten und Grenzen
Unter den entzündlichen Erkrankungen der Nasennebenhöhlen zeigt die akute Sinusitis maxillaris eine besonders hohe Inzidenz. Als sekundär bakteriell-purulente Entzündung entsteht sie häufig konkomitant oder im Nachgang einer banalen primär viralen Rhinitis oder Rhinosinusitis, wenn es zu Schleimhautschwellungen und Ventilations- und Drainagestörungen im Bereich der osteomeatalen Einheit des mittleren Nasengangs kommt. In den nachgeschalteten paranasalen Sinus frontalis, ethmoidalis und maxillaris kommt die korrekte Ventilation zum Erliegen, eine bakterielle Superinfektion der Mukosa entsteht. Im nicht diagnostizierten oder unbehandelten Fall kann dies in ernsthaften Komplikationen an Orbita, fazialen Weichteilen und Endocranium gipfeln. Neben der HNO-ärzlichen Untersuchung bei der akuten Sinusitis maxillaris, die durch endoskopische Verfahren deutlich verbessert und verfeinert werden konnte, bleibt jedoch die direkte visuelle Inspektion der Kieferhöhle zur Diagnosefindung in der Regel unmöglich, da die akut mukosal obstruierten natürlichen Ostien eine Endoskoppassage nicht zulassen. Goldstandard zur Diagnosesicherung ist daher bis heute die Bildgebung mit Röntgenstrahlung und – mit Einschränkungen – die Sonographie. Angeregt von vielversprechenden Grundlagenuntersuchungen zu den Interaktionen von Lichtstrahlung ausgesuchter Spektralbereiche mit biologischen Geweben, griffen wir das Prinzip der Diaphanoskopie der Kieferhöhlen wieder auf und konzipierten eine zweidimensional abbildende Meßeinrichtung für die Diagnostik von Erkrankungen der Nasennebenhöhlen. Dabei ersetzten
wir die Kaltlicht- Diaphanoskopie durch eine Transillumination mit Photonen aus dem Spektralbereich des nahen Infrarot (NIR). Im sog. “optischen Fenster” liegt eine deutlich verminderte Absorption von Licht in biologischem Gewebe vor, so dass Körperhöhlen durchleuchtet und das Streulicht in hervorragender Weise zur Diagnostik verwendet werden kann. Unsere klinisch kontrollierte Studie erbrachte kategorisierbare Transilluminationsaufnahmen, die eine gute positive Korrelation zu den traditionell bildgebenden Verfahren zeigten. Mit der NIRDiaphanoskopie steht also ein abbildendes System zur Verfügung, welches die Fähigkeit eines in-vivo-Stoffwechselmonitorings im betrachteten anatomischen Areal besitzt.
Schlüsselwörter Sinusitis, Kaltlicht-Diaphanoskopie, Infrarot-Diaphanoskopie, Bildgebende Diagnostik, Infrarot-Spektrum, Oto-Rhino-Laryngologie
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Correspondence address: Privatdozentin Dr. med. habil. Marietta Hopf, Charité – Universitätsmedizin Berlin, Universitäts-HNO-Klinik Campus Benjamin Franklin, Hindenburgdamm 30, D-12200 Berlin, Germany Tel.: ++49-30-825 86 36; Fax: ++49-30-897 287 50; e-mail: [email protected]