- Email: [email protected]
Quality assessment of 3D-CTVR, MPR and section plane techniques in ossicular chain reconstruction in middle ear cholesteatoma
Computerized Medical Imaging and Graphics 38 (2014) 696–701
Contents lists available at ScienceDirect
Computerized Medical Imaging and Graphics journal homepage: www.elsevier.com/locate/compmedimag
Quality assessment of 3D-CTVR, MPR and section plane techniques in ossicular chain reconstruction in middle ear cholesteatoma Yang Liu a,∗ , Jianjun Sun a,∗∗ , Yong Guo b , Qiaohui Lu b , Danheng Zhao a , Yongsheng Lin a a b
Center of Otolaryngology, PLA Navy General Hospital, Beijing 100048, China Department of Radiology, PLA Navy General Hospital, Beijing 100048, China
a r t i c l e
a b s t r a c t
i n f o
Article history: Received 11 August 2013 Received in revised form 24 May 2014 Accepted 27 June 2014 Keywords: Cholesteatoma Ossicular chain Volume rendered computer tomography Multi-planar reformation Section plane
Aim: To assess the quality of three-dimensional volume rendered computer tomography (3D-CTVR), multi-planar reformation (MPR) and CT section plane in the fine diagnosis of ossicular chain in middle ear cholesteatoma. Methods: Sixty patients with middle ear cholesteatoma were selected in this retrospective study. All cases underwent pre-operative CT scan. The respective radiologic reports of the ossicles status via three protocols were then compared to surgical findings. Results: Quality assessment of these three protocols in the fine diagnosis of fine ossicles buried inside the soft tissue showed that both CTVR and MPR are more superior to conventional section plane, especially CTVR. Conclusion: The uses of CTVR and MPR, in conjunction with conventional section plane, are better able to show where the true and fine ossicular chain in the cholesteatoma mass is. In the final analysis, we believe that the use of CTVR and MPR techniques can have profound contributive value in future clinical work. © 2014 Elsevier Ltd. All rights reserved.
1. Introduction It is widely recognized that the ossicular chain plays an important role in sound conduction. In pre-operative cholesteatoma surgery, understanding the extent of abnormality of the ossicles are essential in the reconstruction of the ossicular chain. The two axial and coronal section planes of conventional HRCT (high resolution CT) are insufficient to allow otologists to clearly determine the degree of ossicle conditions such as the absence or destruction of ossicular chain within the surrounding soft tissues. In recent years, the increasing use of three dimensional volume rendered computer tomography (3D-CTVR) has enabled otologists to view the condition of the ossicular chain inside middle ear cholesteatoma. The employment of CTVR can certainly reveal the distinct 3D ossicle imaging, especially when soft tissues around the ossiculum are removed. Another important method, the multi-planar reconstruction (MPR) technique, can even project multiple section planes of
∗ Corresponding author at: ENT Department, PLA Navy General Hospital, No. 6 Fucheng Road, Haidian District, Beijing 100048, China. ∗∗ Co-corresponding author at: ENT Department, PLA Navy General Hospital, No.6 Fucheng Road, Haidian District, Beijing 100048, China. E-mail addresses: [email protected] (Y. Liu), [email protected] (J. Sun). http://dx.doi.org/10.1016/j.compmedimag.2014.06.019 0895-6111/© 2014 Elsevier Ltd. All rights reserved.
ossicles onto the same plane. Several authors have reported and discussed the advantages and limitations of these two protocols in their literature [1–3]. In our study, both the CTVR and MPR techniques, in conjunction with conventional axial and coronal section plane, were used to show up the fine structures of the ossicular chain. Our results convince us that the combined uses of these techniques will likely become a trend in future clinical work.
2. Materials and methods 2.1. Cases size From February 2010 through March 2012, sixty cases of middle ear cholesteatoma from our department were selected for this study. All cases were approved by the ethics committee of our hospital. These 60 not only have cholesteatoma in their middle ear cavity, but also in the mastoid cavity. All patients had conductive hearing loss (air-bone gap from 15 dB to 45 dB). Of these 60 cases, 34 were male and 26 female, ranging in age from 16 through 65 (mean age: 42.6). All surgeries for this study were performed by the first author, with notes taken within the 1st to 3rd day after CT scan. Canal wall-up and canal wall-down mastoidectomy were also performed, along with written observations of the ossicle chain during
Y. Liu et al. / Computerized Medical Imaging and Graphics 38 (2014) 696–701
697
Fig. 1. (a) Axial section: the plane of epitympanum. (b) The plane of epitympanum in the coronal section. (c) The plane of vestibular window in the coronal section. (1) Head of malleus; (2) handle of malleus; (3) malleoincudal joint; (4) body of incus; (5) long limb of incus; f, vestibular window.
and after each surgery. In all instances, their ossicular chains were embedded inside soft tissues (either cholesteatoma or granulation). 2.2. CT scan and post-processing The 128-channel multi-detector row CT scanner (Philips Brilliance iCT128) was used. Scanning ranges from the lower margin of the external auditory meatus to the top margin of the petrous bone, with every subject in the supine position. The axial thin slice scanning was set at a collimation of 20 mm × 0.65 mm, with pitch at 0.25 mm, horizon (FOV) at 150 mm × 150 mm, matrix at 1024 × 1024, voltage at 120 kV and current at 350 mAs. The Ysharp bone algorithm was used, with reconstruction set at 0.34 mm intervals overlap and the result of 128–140 layer image. Voxel dimensions were 0.1465 mm for X and Y, and 0.34 mm for Z. All data were then transmitted to the EBW4 workstation for reconstruction of three post-processing protocols. These were: (1) the conventional axial and coronal section planes of high resolution CT (HRCT); (2) the imaging of multi-planar reconstruction (MPR); and (3) the three-dimensional reconstructed volume rendered computer tomography (3D-CTVR). The window level for the 3D imaging was set at 500 to −400 HU, with window width set at 2000 HU. 2.3. Data analysis All radiologic reports analyzed by three independent and experienced radiologists concluded that: (1) the standard observation planes of conventional axial and coronal section plane were (a) the plane of epitympanum in the axial section (Fig. 1a); (b) the plane of epitympanum in the coronal section (Fig. 1b); and (c) the plane of vestibular window in the coronal section (Fig. 1c); (2) the standard observation planes of the MPR were (a) along the plane of the long axes of the incus and the reconstructed malleus paralleling
the incudal long process (Fig. 2a); and (b) along the plane of anterior and posterior crus of stapes (Fig. 2b); and (3) the reconstructed CTVR imaging located in a designed cube can be magnified and rotated. Otologists are generally familiar with the two standard viewing field of CTVR, namely (1) from the posterior-inferior edge of tympanic membrane to the mesotympanum and epitympanum (Fig. 3a); and (2) from the antrum and epitympanum to the mesotympanum (Fig. 3b). 2.4. Statistical analysis All key segments of the ossicular chain which were analyzed are tabulated in Table 1. This table is a simple, modified version of the classification used by Zhang et al. [1]. During surgery, otologists are generally more concerned with the head of malleus, the handle of malleus, the body of incus, the long limb of incus, and the malleoincudal joint. The reason for this is that when dealing with ossicular chain, otologists must first focus on the connection of stapes and long limb of incus. If the long limb of incus exists, the connection should be divided by cutting the incudostapedial joint in order to protect the inner ear. Since the attic is occupied by the head of malleus and body of incus, to eradicate cholesteatoma, the latter two typically needs to be removed. The handle of malleus plays an important role in supporting the tympanum membrane and the reconstruction of the ossicular chain. At the same time, segments of the ossicular chain such as the lateral process of malleus, the neck of malleus, the short limb of the incus, the lenticular process and incudostapedial joint are given no more consideration. In all our operations, if the crus were either eroded or absent, total ossicular replacement prosthesis (TORP) were implanted, while the anterior and posterior crus were replaced with the superstructure of stapes. Since the CTVR and MPR imaging only shows the structure of the footplates instead of its state (vibration or fixation), and for which
Fig. 2. The standard observation planes of MPR. (a) The plane of malleus and incus. (b) The plane of vestibular and stapes. (1) Head of malleus; (2) handle of malleus; (3) malleoincudal joint; (4) body of incus; (5) long limb of incus; (6) incudostapedial joint; h: head of stapes; f, footplate of stapes; pc, posterior crus of stapes; and ac, anterior crus of stapes.
698
Y. Liu et al. / Computerized Medical Imaging and Graphics 38 (2014) 696–701
Fig. 3. The two standard viewing direction of CTVR; (a) view from the tympanic membrane to the mesotympanum and epitympanum; (b) view from the antrum and epitympanum to the mesotympanum; (1) head of malleus; (2) handle of malleus; (3) malleoincudal joint; (4) body of incus; (5) long limb of incus; (6) incudostapedial joint; pc, posterior crus of stapes; ac, anterior crus of stapes; f, footplate of stapes; s, short limb of incus; lp, later process of malleus.
we are chiefly concerned, the footplate of stapes were thus ignored. All segment details, including surgical finding comparisons for all three protocols are listed in Table 1. SPSS software was used to complete the chi-square test. The quantitative assessments for the representation of different segments were based on a 3-point scoring system. A segment is scored 2 if were intact, 1 if partial and eroded, and 0 if absent (see Table 1 results). In order to evaluate the sensitivity, specificity and accuracy of these three different protocols, segments with 0 score were considered negative or absent, and segments with score of 1 or 2 were considered positive for intact bone (see Table 2 results). We also assessed the ossicular clarity of conventional section plane, MPR and CTVR imaging. From these 60 patients, we selected cases where ossicles were present during surgery. Ossicular clarity was subsequently evaluated based on their imaging results. For example, one case was selected if the malleus existed proved in the operation, then that malleus imaging was classified either as clear, vague or not showing in three different protocols. The same assessment was used for incus and stapes (see Table 3 results). In this study, stapes superstructures were used to replace stapes.
differences (p = 0.000). This indicated that the representation of these two segments via section plane do not coincide well with surgical findings. The reason of poor imaging may be partial absorption of the handle of malleus and much fine stapes superstrure. Where MPR and CTVR are concerned, the p value of stapes superstructure were 0.04 (0.05 > p > 0.01), respectively. In Table 1, statistical data for short limb of incus in MPR were excluded because it was blocked in the MPR selected plane. Other data in Table 1 further revealed that assessments for the various segments of the three different protocols have no significant differences (p > 0.05). 3.2. Efficacy of the three protocols in the assessment of various segments Table 2 lists the sensitivity, specificity and accuracy data of the three protocols assessed in various segments. Sensitivity for CTVR was found to be highest in the handle of malleus (95.42%), and lowest in section planes to the stapes superstructure (12.50%). Specificity for CTVR was also highest in the short limb of incus (93.75%) and lowest in section plane to the head of malleus (13.04%). Similarly, accuracy for CTVR was highest in the handle of malleus (93.33%) and lowest in section plane to the stapes superstructure (40.00%). Overall, the efficacy of CTVR is superior to that of section plane. The p value of stapes superstructure in section plane was 0.61. This indicated that the assessment of stapes superstructure in section plane were both uncertain and unworthy. Statistical data for the short limb of incus in MPR were also excluded in Table 1.
3. Results 3.1. Quantitative assessments of various segments for the three different protocols The quantitative assessment results for conventional section plane, MPR and CTVR for different ossicular segments are summarized in Table 1. Most of p values are much higher than 0.05, this explained that the imaging assessments were quite coincidental to surgical findings. With regard to section plane, the p values of handle of malleus and stapes superstructure showed significant
3.3. Clarity comparison of the various protocols for the three ossicles The clarity for the three protocols (conventional section plane, MPR and CTVR) for the assessment of ossicles is summarized in
Table 1 Quantitative assessment. Segments*
Protocols Section plane
Head of malleus Handle of malleus Malleoincudal joint Long limb of incus Body of incus Short limb of incus Stapes Superstructure
p
2
1
0
MV
SD
18 17 19 9 18 22 1
16 24 11 8 11 4 5
26 19 30 43 31 34 54
0.87 0.97 0.82 0.43 0.78 0.81 0.12
0.85 0.78 0.89 0.75 0.89 0.96 0.37
0.53 0.00* 0.36 0.45 0.84 0.82 0.00*
MPR
p
2
1
0
MV
SD
20 36 16 15 20 – 26
17 8 20 10 13 – 9
23 16 24 35 27 – 25
0.95 1.33 0.87 0.67 0.88 – 1.02
0.85 0.88 0.81 0.86 0.89 – 0.93
0.92 0.14 0.54 0.45 0.54 – 0.04*
CTVR
p
2
1
0
MV
SD
28 44 28 19 29 24 26
10 5 4 3 7 3 9
22 11 28 39 24 33 25
1.10 1.55 1.00 0.68 1.08 0.85 1.02
0.92 0.79 0.97 0.93 0.94 0.97 0.93
0.40 1.00 0.84 0.39 0.07 1.00 0.04*
* Comparison for different segments of three protocol with surgical findings. p > 0.05: no significant differences. The imaging assessments were quite coincidental to surgical findings. MV, score mean value; SD, standard deviation.
Y. Liu et al. / Computerized Medical Imaging and Graphics 38 (2014) 696–701
699
Table 2 Efficacy of three protocols. Segments
Protocols Section plane
Head of malleus Handle of malleus Malleoincudal joint Long limb of incus Body of incus Short limb of incus Stapes Superstructure
MPR
CTVR
p
SN (%)
SP (%)
AC (%)
p
SN (%)
SP (%)
AC (%)
p
SN (%)
SP (%)
AC (%)
0.000 0.000 0.000 0.000 0.000 0.000 0.61
83.78 81.63 79.41 68.42 89.66 82.14 12.50
13.04 90.90 88.46 90.24 80.65 90.63 95.00
56.67 83.33 83.33 83.33 85.00 86.66 40.00
0.000 0.000 0.000 0.000 0.000 – 0.001
86.48 87.76 91.18 94.74 87.50 – 75.00
78.26 90.90 80.76 82.93 82.14 – 75.00
66.66 88.33 86.67 86.66 85.00 – 75.00
0.000 0.000 0.000 0.000 0.000 0.000 0.000
86.48 95.42 76.47 94.74 80.51 89.28 80.00
73.91 81.82 76.92 90.24 87.50 93.75 85.00
81.67 93.33 76.67 91.67 83.33 91.67 81.67
SN, sensitivity; SP, specificity; AC, accuracy.
Table 3 Comparison of clarity. 2
Ossicle
Malleus
Exist
50
Imaging
Plane
MPR
CTVR
Clearly
16 32% 24 48% 10 20%
41 82% 3 6% 6 12%
48 96% –
Vague No show
p
2
Incus
p
35
2 4%
Plane 53.51
0.000 10 28.57% 13 37.14% 12 34.29%
Stapes superstructure
2
p
48.14
0.000
40 MPR
CTVR
27 77.14% 3 8.57% 5 14.29%
32 91.43% –
Plane 35.64
3 8.57%
0.000
0 4 10% 36 90%
MPR
CTVR
23 57.5% 7 17.5% 10 25.0%
23 57.5% 7 17.5% 10 25.0%
In all the 60 subjects who underwent operation, the cases with completed malleus (50), incus (35), stapes superstructures (40) were selected to assess the imaging of three different protocols via clearly, vague and no showing. p value (=0.000) explained that the statistical result with probability of error is 0.000.
Table 3. In all the 60 subjects who underwent operation, 50 cases had completed malleus, 35 had completed incus, and 40 had completed stapes superstructures. These subjects were selected to assess the imaging of three different protocols via clearly, vague and no showing. p value (=0.000) explained that the probability of error for the statistical result is 0.000. For malleus, the clear images were obtained 48(96%) from CTVR, 41(82%) from MPR, and only 16(32%) from conventional section plane. Furthermore, in section plane imaging, 10 cases (20%) have no images showing at all. Incus was present in 35 of the 60 subjects. Of these 35 cases, 32 (91.43%) have clear images from CTVR, 27(77.14%) from MPR and only 10 (28.57%) from conventional section plane. Here again, 12 cases (34.29%) in section plane showed no images. Also in this study, we found 40 cases of stapes superstructure. Of these 40, 23 cases (57.50%) have clear showings from CTVR, 23(57.50%) from MPR, and in section plane, 36 cases (90%) with no showings. It can be seen in Table 3 that both MPR and CTVR have significant advantages in showing ossicles images over that of conventional section plane. However, the images of stapes superstructure were not as good as that of malleus and incus. In middle ear cholesteatoma, the thin and smaller crus of stapes were surrounded by soft tissues, making it difficult to distinguish the stapes superstructure.
3.4. Case examples Fig. 4 is an image example of a patient with middle ear cholesteatoma. In the section plane (Fig. 4a1), the ossicles resemble an “ice cone” (the imaging of ossicles in this plane resembles the shape of ice cones). It was also not very clear. In the MPR image (Fig. 4b), we can clearly see the handle of malleus, the body of incus and soft tissues around the ossicular chain. In Fig. 4c1 and c2, the CTVR image of the ossicular chain can be observed directly and clearly. No long limb of incus was present in this instance. Fig. 5 shows another patient’s imaging with the ossicular chain surrounded by soft tissues. Here in the section plane, the ossicular chain cannot be clearly seen. However, using
CTVR, the ossicular chain is clearly visible when soft tissues are removed 4. Discussion Through CT section plane alone, it is difficult to accurately show the three ossicles in middle ear cavity. Moreover, for cholesteatoma with ossicular erosion and deformity, it is particularly difficult to show ossicular changes due to soft tissue density (such as in cholesteatoma matrix and granulation). Modern CT technology, including “multi-slice spiral scanning,” “volume scanning” and “isotropic scanning,” [4], allow data to be immediately transmitted to post-processing workstation where 3D images of ossicular chains are created. In recent years, the more popular reconstruction techniques have included MPR, CTVR and endoscopy (CTVE) [5]. In fact, it is common nowadays to combine these various techniques in the diagnosis of ossicular lesions [3]. CTVE imaging, which is based on shaded-surface displays (SSD-based CTVE), has been discussed by many authors [4–6]. Since CTVE barely shows 10% of data, loss of information are inevitable [1]. Its major disadvantage is its inability to distinguish bony tissues from soft tissues inside cavity filled with cholesteatoma [6,7]. To differentiate from previous other studies [1,2,4,5] where the ossicular chain was in well-aerated middle ear cavity (high density contrast between air and bone), we use CTVR and MPR protocols instead on patients with ossicular chain buried in soft tissue mass in middle ear cholesteatoma 4.1. Conventional axial and coronal section plane The conventional axial and coronal section plane primarily examines whether any air spaces or soft tissues are in middle ear cavity. This plane offers important structural information such as the cochlea [8]. However, its limitations are its vague showing of the ossicular chain, especially in middle ear cholesteatoma. Fuse T. et al. reported that pre-operative detection of total defects in the head of malleus, the body and long process of the incus via
700
Y. Liu et al. / Computerized Medical Imaging and Graphics 38 (2014) 696–701
Fig. 4. (a) Section planes of conventional CT. (a1) axial section; (a2 and a3) coronal section; (b) MPR imaging; (c1 and c2) CTVR imaging; (1) head of malleus; (2) handle of malleus; (3) malleoincudal joint; (4) body of incus; (6) incudostapedial joint; st, soft tissue.
high-resolution CT were possible in all their cases. Their analysis found the defect in the handle of the malleus and superstructure of the stapes to be 33.3% and 60%, respectively. In addition, partial defects of the stapes crus could not be correctly diagnosed by pre-operative estimation [9]. Their conclusion concurred with our results tabulated in Table 1. The p value (p = 0.00) of the handle of malleus and stapes superstructure is indicative that the assessment of these two segments in section plane were far different (or coincided badly) when compared to surgical findings in cholesteatoma surgery. According to Trojanowska A., the analysis of axial images alone does not provide sufficient information in ossicular diagnosis. Their sensitivity (89%) and specificity (87%) findings were all lower than those of MPR [3]. In our study, the sensitivity, specificity and accuracy levels of conventional section planes were also lower than that of MPR and CTVR as listed in Table 2, as were the clarity of ossicles depicted in conventional section plane (Table 3). 4.2. MPR imaging MPR imaging is more advantageous than section plane in showing different ossicular segments. The former is created by reformation of the pixels. In comparison to original 2D imaging, both resolution and contrasts are maintained [1]. One of the major
advantages of MPR is that it can show total and fine ossicular chains within the same layer via multi-directional adjustment [3,10]. Consequently, both soft and bony tissues are easily distinguishable. This is precisely what most otologists are chiefly concerned with during cholesteatoma surgery. Fig. 2a and b are examples of this feature of MPR with clear imaging of the ossicular chain and soft tissues. In terms of the efficacy of the three protocols for demonstration of the ossicles’ structures, Zhang LC et al. reported that MPR exhibited significant superiority in most structures [1]. Our statistical data (Table 2: MPR-AC: 66.66–88.33%) support their conclusions. UIIa M.B. (2008) also stated that the anatomic and pathologic characterization of middle ear structure can be improved using the MPR technique [11]. In his pre-operative imaging assessment of ossicles in 30 chronic suppurative otitis media with cholesteatoma patients, Pandey described that their assessments were satisfactory in larger ossicular parts. However, in the evaluation of stapes superstructure, their accuracy of MPR (in multiplanar 2D reformation) was only 76.97% [12]. In our study, it was 75% for MPR but 40% for section plane. This is indicative that MPR can reveal anatomical features and pathologic conditions more precisely than in section plane. For precise surgical planning and diagnosis of diseases, the MPR visualization in middle ear and adjacent structures are ideal.
Fig. 5. (a) Coronal section plane of conventional CT; (b) MPR imaging; (c1 and c2) CTVR imaging; with soft tissues (st) of cholesteatoma around the ossicular chain filtered out (c1 ) and the whole ossicular chain exposed with no long limb of incus; (1) handle of malleus; (4) body of incus; h, head of stapes; vw, vestibular window; st, soft tissue; ss, superstructure of stapes (vague). No long limb of incus exists in this case.
Y. Liu et al. / Computerized Medical Imaging and Graphics 38 (2014) 696–701
701
4.3. 3D- CTVR imaging
Conflict of interest
In our study, the CTVR technique was the key method used. In our study for CTVR technique, the six lines on coronal and axial referenced images were defined in the post-processing workstation. Furthermore, two standard fields of view were selected according to the surgical field. In order to define an ossicular destruction well, a wide range of window was used. As a result, the 3D imagings of ossicular chain structures were got far better here. In the majority of previous studies, the 3D CTVE protocol, as a surface-rendering technique, was the main procedure used to perform 3D-reconstruction [7,11,13,14]. In middle ear cholesteatoma, the ossicular chain is usually surrounded by granulation and/or cholesteatoma. For this reason, the surrounding “irrelevant structures” of ossicles should be dissected in order that the ossicular chain buried in the soft tissue can be showed completely. Here too, we found the threshold filtering feature of CTVR better enables radiologists and otologists to assess the pathological status of the ossicular chain after soft tissues around it are removed. This is actually CTVR’s major advantage over all the other 3D techniques. Jang reported that in 15 of his patients with chronic otitis media with cholesteatoma, the 3D-CT clearly outlined the damaged bony structures [17]. Our typical case study in Fig. 5c1 and c2 visibly show the exposed abnormal ossicular chain after soft tissues of the cholesteatoma were removed. As can be seen in Table 1, all of our data for quantitative assessment in various segments of CTVR are superior to section plane. The p values of stapes superstructure for MPR and CTVR in our case were 0.04 in middle ear cholesteatoma. Even though this indicated that representation of stapes superstructure were unsatisfactory in MPR and CTVR, it is still better than in section plane. These findings coincide with that of Zhang et al. [1]. In the overall analysis, the efficacy of CTVR in various segments are superior to that of section plane. With regard to clarity assessments of these three protocols, CTVR ranked highest, followed by MPR, with section plane third.
Authors declare that they have no conflicts of interest concerning this article.
5. Conclusion Our final analysis of quality for the three protocols in the fine diagnosis of ossicles buried within the cholesteatoma is that both MPR and CTVR remain superior to conventional section plane. We believe that MPR and CTVR are invaluable protocols in the diagnosis of ossicular chain in middle ear cholesteatoma. We also believe that the combination use of these two protocols, along with conventional axial and coronal section plane, could be the way to go in future pre-operative ossicular chain diagnosis. Except for the fine diagnosis of ossicular chain in the cholesteatoma, the VR and MPR technology can also be used well in the differential diagnosis of otosclerosis, tympanosclerosis, interruption of the ossicular chain, and ossicular malformation. In the assessment of implanted ossicular prosthesis, it can also give well showing.
Acknowledgements We thank Prof. Jie Chen for generously providing his assistance in the statistical portion of our study. Prof. Chen: Department of Statistics, Peking University People’s Hospital, Beijing, 100044, China References [1] Zhang LC, Sha Y, Wang ZM, Luo DT, Huang WH, Dai PD, et al. 3D image of the middle ear ossicles: three protocols of post-processing based on multislice computed tomography. Eur Arch Otorhinolaryngol 2011;268(May (5)):677–83. [2] Fatterpekar GM, Doshi AH, Dugar M, Delman BN, Naidich TP, Som PM. Role of 3D CT in the evaluation of the temporal bone. Radiographics 2006;26(October (Suppl. 1)):S117–32 [review]. [3] Trojanowska A, Trojanowski P, Olszanski W, Klatka J, Drop A. How to reliably evaluate middle ear diseases? Comparison of different methods of postprocessing based on multislice computed tomography examination. Acta Otolaryngol 2007;127(March):258–64. [4] Fujii N, Inui Y, Katada K. Temporal bone anatomy: correlation of multiplanar reconstruction sections and three-dimensional computed tomography images. Jpn J Radiol 2010;28(November (9)):637–48. [5] Ho AC, Lee R, Co MT, Chow Ck, Au Yeung KM. Is virtual endoscopy of the middle ear useful? Ear Nose Throat J 2011;90(June (6)):256–60. [6] Chen DY, Chen XW, Wang Y, Cao KL, Jin ZY. Virtual otoscopy of middle ear structure and pathology. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi 2005;40(January (1)):18–21 [article in Chinese]. [7] Jiang LX, Ma YK, Luo D, Yang N, Li YZ. Evaluation of the virtual endoscopy on traumatic ossicular chain disruption pre- and post-operation. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi 2008;43(April (4)):272–6. [8] Tan TY, Goh JP. Imaging of congenital middle ear deafness. Ann Acad Med Singapore 2003;32(July (4)):495–9 [review]. [9] Fuse T, Aoyagi M, Koike Y, Sugai Y. Diagnosis of the ossicular chain in the middle ear by high-resolution CT. ORL J Otorhinolaryngol Relat Spec 1992;54(5): 251–4. [10] Gong RZ, Chao BT, Liu K, Fan ZM, Wang HB, Chen QH, et al. CT multiplan reconstruction images of disorder of stapes. Zhonghua Er Bi Yan Hou Ke Za Zhi 2004;39(May (5)):265–8. [11] Blanco Ulla M, Vázquez F, Pumar JM, et al. Oblique multiplanar reformation in multislice temporal bone CT. Surg Radiol Anat 2009;31(July (6)):475–9. [12] Pandey AK, Bapuraj JR, Gupta AK, Gupta AK, Khandelwal N. Is there a role for virtual otoscopy in the preoperative assessment of the ossicular chain in chronic suppurative otitis media? Comparison of HRCT and virtual otoscopy with surgical findings. Eur Radiol 2009;19(6):1408–16. [13] Himi T, Sakata M, Shintani Mitsuzawa H, Kamagata M, Satoh J, et al. Middle ear imaging using virtual endoscopy and its application in patients with ossicular chain anomaly. ORL J Otorhinolaryngol Relat Spec 2000;62(November–December (6)):316–20. [14] Rodt T, Bartling S, Schmidt AM, Weber BP, Lenarz T, Becker H. Virtual endoscopy of the middle ear: experimental and clinical results of a standardised approach using multi-slice helical computed tomography. Eur Radiol 2002;12(July (7)):1684–92. [17] Jang CH, Wang PC. Preoperative evaluation of bone destruction using three-dimensional computed tomography in cholesteatoma. J Laryngol Otol 2004;118(October (10)):827–9.
Contents lists available at ScienceDirect
Computerized Medical Imaging and Graphics journal homepage: www.elsevier.com/locate/compmedimag
Quality assessment of 3D-CTVR, MPR and section plane techniques in ossicular chain reconstruction in middle ear cholesteatoma Yang Liu a,∗ , Jianjun Sun a,∗∗ , Yong Guo b , Qiaohui Lu b , Danheng Zhao a , Yongsheng Lin a a b
Center of Otolaryngology, PLA Navy General Hospital, Beijing 100048, China Department of Radiology, PLA Navy General Hospital, Beijing 100048, China
a r t i c l e
a b s t r a c t
i n f o
Article history: Received 11 August 2013 Received in revised form 24 May 2014 Accepted 27 June 2014 Keywords: Cholesteatoma Ossicular chain Volume rendered computer tomography Multi-planar reformation Section plane
Aim: To assess the quality of three-dimensional volume rendered computer tomography (3D-CTVR), multi-planar reformation (MPR) and CT section plane in the fine diagnosis of ossicular chain in middle ear cholesteatoma. Methods: Sixty patients with middle ear cholesteatoma were selected in this retrospective study. All cases underwent pre-operative CT scan. The respective radiologic reports of the ossicles status via three protocols were then compared to surgical findings. Results: Quality assessment of these three protocols in the fine diagnosis of fine ossicles buried inside the soft tissue showed that both CTVR and MPR are more superior to conventional section plane, especially CTVR. Conclusion: The uses of CTVR and MPR, in conjunction with conventional section plane, are better able to show where the true and fine ossicular chain in the cholesteatoma mass is. In the final analysis, we believe that the use of CTVR and MPR techniques can have profound contributive value in future clinical work. © 2014 Elsevier Ltd. All rights reserved.
1. Introduction It is widely recognized that the ossicular chain plays an important role in sound conduction. In pre-operative cholesteatoma surgery, understanding the extent of abnormality of the ossicles are essential in the reconstruction of the ossicular chain. The two axial and coronal section planes of conventional HRCT (high resolution CT) are insufficient to allow otologists to clearly determine the degree of ossicle conditions such as the absence or destruction of ossicular chain within the surrounding soft tissues. In recent years, the increasing use of three dimensional volume rendered computer tomography (3D-CTVR) has enabled otologists to view the condition of the ossicular chain inside middle ear cholesteatoma. The employment of CTVR can certainly reveal the distinct 3D ossicle imaging, especially when soft tissues around the ossiculum are removed. Another important method, the multi-planar reconstruction (MPR) technique, can even project multiple section planes of
∗ Corresponding author at: ENT Department, PLA Navy General Hospital, No. 6 Fucheng Road, Haidian District, Beijing 100048, China. ∗∗ Co-corresponding author at: ENT Department, PLA Navy General Hospital, No.6 Fucheng Road, Haidian District, Beijing 100048, China. E-mail addresses: [email protected] (Y. Liu), [email protected] (J. Sun). http://dx.doi.org/10.1016/j.compmedimag.2014.06.019 0895-6111/© 2014 Elsevier Ltd. All rights reserved.
ossicles onto the same plane. Several authors have reported and discussed the advantages and limitations of these two protocols in their literature [1–3]. In our study, both the CTVR and MPR techniques, in conjunction with conventional axial and coronal section plane, were used to show up the fine structures of the ossicular chain. Our results convince us that the combined uses of these techniques will likely become a trend in future clinical work.
2. Materials and methods 2.1. Cases size From February 2010 through March 2012, sixty cases of middle ear cholesteatoma from our department were selected for this study. All cases were approved by the ethics committee of our hospital. These 60 not only have cholesteatoma in their middle ear cavity, but also in the mastoid cavity. All patients had conductive hearing loss (air-bone gap from 15 dB to 45 dB). Of these 60 cases, 34 were male and 26 female, ranging in age from 16 through 65 (mean age: 42.6). All surgeries for this study were performed by the first author, with notes taken within the 1st to 3rd day after CT scan. Canal wall-up and canal wall-down mastoidectomy were also performed, along with written observations of the ossicle chain during
Y. Liu et al. / Computerized Medical Imaging and Graphics 38 (2014) 696–701
697
Fig. 1. (a) Axial section: the plane of epitympanum. (b) The plane of epitympanum in the coronal section. (c) The plane of vestibular window in the coronal section. (1) Head of malleus; (2) handle of malleus; (3) malleoincudal joint; (4) body of incus; (5) long limb of incus; f, vestibular window.
and after each surgery. In all instances, their ossicular chains were embedded inside soft tissues (either cholesteatoma or granulation). 2.2. CT scan and post-processing The 128-channel multi-detector row CT scanner (Philips Brilliance iCT128) was used. Scanning ranges from the lower margin of the external auditory meatus to the top margin of the petrous bone, with every subject in the supine position. The axial thin slice scanning was set at a collimation of 20 mm × 0.65 mm, with pitch at 0.25 mm, horizon (FOV) at 150 mm × 150 mm, matrix at 1024 × 1024, voltage at 120 kV and current at 350 mAs. The Ysharp bone algorithm was used, with reconstruction set at 0.34 mm intervals overlap and the result of 128–140 layer image. Voxel dimensions were 0.1465 mm for X and Y, and 0.34 mm for Z. All data were then transmitted to the EBW4 workstation for reconstruction of three post-processing protocols. These were: (1) the conventional axial and coronal section planes of high resolution CT (HRCT); (2) the imaging of multi-planar reconstruction (MPR); and (3) the three-dimensional reconstructed volume rendered computer tomography (3D-CTVR). The window level for the 3D imaging was set at 500 to −400 HU, with window width set at 2000 HU. 2.3. Data analysis All radiologic reports analyzed by three independent and experienced radiologists concluded that: (1) the standard observation planes of conventional axial and coronal section plane were (a) the plane of epitympanum in the axial section (Fig. 1a); (b) the plane of epitympanum in the coronal section (Fig. 1b); and (c) the plane of vestibular window in the coronal section (Fig. 1c); (2) the standard observation planes of the MPR were (a) along the plane of the long axes of the incus and the reconstructed malleus paralleling
the incudal long process (Fig. 2a); and (b) along the plane of anterior and posterior crus of stapes (Fig. 2b); and (3) the reconstructed CTVR imaging located in a designed cube can be magnified and rotated. Otologists are generally familiar with the two standard viewing field of CTVR, namely (1) from the posterior-inferior edge of tympanic membrane to the mesotympanum and epitympanum (Fig. 3a); and (2) from the antrum and epitympanum to the mesotympanum (Fig. 3b). 2.4. Statistical analysis All key segments of the ossicular chain which were analyzed are tabulated in Table 1. This table is a simple, modified version of the classification used by Zhang et al. [1]. During surgery, otologists are generally more concerned with the head of malleus, the handle of malleus, the body of incus, the long limb of incus, and the malleoincudal joint. The reason for this is that when dealing with ossicular chain, otologists must first focus on the connection of stapes and long limb of incus. If the long limb of incus exists, the connection should be divided by cutting the incudostapedial joint in order to protect the inner ear. Since the attic is occupied by the head of malleus and body of incus, to eradicate cholesteatoma, the latter two typically needs to be removed. The handle of malleus plays an important role in supporting the tympanum membrane and the reconstruction of the ossicular chain. At the same time, segments of the ossicular chain such as the lateral process of malleus, the neck of malleus, the short limb of the incus, the lenticular process and incudostapedial joint are given no more consideration. In all our operations, if the crus were either eroded or absent, total ossicular replacement prosthesis (TORP) were implanted, while the anterior and posterior crus were replaced with the superstructure of stapes. Since the CTVR and MPR imaging only shows the structure of the footplates instead of its state (vibration or fixation), and for which
Fig. 2. The standard observation planes of MPR. (a) The plane of malleus and incus. (b) The plane of vestibular and stapes. (1) Head of malleus; (2) handle of malleus; (3) malleoincudal joint; (4) body of incus; (5) long limb of incus; (6) incudostapedial joint; h: head of stapes; f, footplate of stapes; pc, posterior crus of stapes; and ac, anterior crus of stapes.
698
Y. Liu et al. / Computerized Medical Imaging and Graphics 38 (2014) 696–701
Fig. 3. The two standard viewing direction of CTVR; (a) view from the tympanic membrane to the mesotympanum and epitympanum; (b) view from the antrum and epitympanum to the mesotympanum; (1) head of malleus; (2) handle of malleus; (3) malleoincudal joint; (4) body of incus; (5) long limb of incus; (6) incudostapedial joint; pc, posterior crus of stapes; ac, anterior crus of stapes; f, footplate of stapes; s, short limb of incus; lp, later process of malleus.
we are chiefly concerned, the footplate of stapes were thus ignored. All segment details, including surgical finding comparisons for all three protocols are listed in Table 1. SPSS software was used to complete the chi-square test. The quantitative assessments for the representation of different segments were based on a 3-point scoring system. A segment is scored 2 if were intact, 1 if partial and eroded, and 0 if absent (see Table 1 results). In order to evaluate the sensitivity, specificity and accuracy of these three different protocols, segments with 0 score were considered negative or absent, and segments with score of 1 or 2 were considered positive for intact bone (see Table 2 results). We also assessed the ossicular clarity of conventional section plane, MPR and CTVR imaging. From these 60 patients, we selected cases where ossicles were present during surgery. Ossicular clarity was subsequently evaluated based on their imaging results. For example, one case was selected if the malleus existed proved in the operation, then that malleus imaging was classified either as clear, vague or not showing in three different protocols. The same assessment was used for incus and stapes (see Table 3 results). In this study, stapes superstructures were used to replace stapes.
differences (p = 0.000). This indicated that the representation of these two segments via section plane do not coincide well with surgical findings. The reason of poor imaging may be partial absorption of the handle of malleus and much fine stapes superstrure. Where MPR and CTVR are concerned, the p value of stapes superstructure were 0.04 (0.05 > p > 0.01), respectively. In Table 1, statistical data for short limb of incus in MPR were excluded because it was blocked in the MPR selected plane. Other data in Table 1 further revealed that assessments for the various segments of the three different protocols have no significant differences (p > 0.05). 3.2. Efficacy of the three protocols in the assessment of various segments Table 2 lists the sensitivity, specificity and accuracy data of the three protocols assessed in various segments. Sensitivity for CTVR was found to be highest in the handle of malleus (95.42%), and lowest in section planes to the stapes superstructure (12.50%). Specificity for CTVR was also highest in the short limb of incus (93.75%) and lowest in section plane to the head of malleus (13.04%). Similarly, accuracy for CTVR was highest in the handle of malleus (93.33%) and lowest in section plane to the stapes superstructure (40.00%). Overall, the efficacy of CTVR is superior to that of section plane. The p value of stapes superstructure in section plane was 0.61. This indicated that the assessment of stapes superstructure in section plane were both uncertain and unworthy. Statistical data for the short limb of incus in MPR were also excluded in Table 1.
3. Results 3.1. Quantitative assessments of various segments for the three different protocols The quantitative assessment results for conventional section plane, MPR and CTVR for different ossicular segments are summarized in Table 1. Most of p values are much higher than 0.05, this explained that the imaging assessments were quite coincidental to surgical findings. With regard to section plane, the p values of handle of malleus and stapes superstructure showed significant
3.3. Clarity comparison of the various protocols for the three ossicles The clarity for the three protocols (conventional section plane, MPR and CTVR) for the assessment of ossicles is summarized in
Table 1 Quantitative assessment. Segments*
Protocols Section plane
Head of malleus Handle of malleus Malleoincudal joint Long limb of incus Body of incus Short limb of incus Stapes Superstructure
p
2
1
0
MV
SD
18 17 19 9 18 22 1
16 24 11 8 11 4 5
26 19 30 43 31 34 54
0.87 0.97 0.82 0.43 0.78 0.81 0.12
0.85 0.78 0.89 0.75 0.89 0.96 0.37
0.53 0.00* 0.36 0.45 0.84 0.82 0.00*
MPR
p
2
1
0
MV
SD
20 36 16 15 20 – 26
17 8 20 10 13 – 9
23 16 24 35 27 – 25
0.95 1.33 0.87 0.67 0.88 – 1.02
0.85 0.88 0.81 0.86 0.89 – 0.93
0.92 0.14 0.54 0.45 0.54 – 0.04*
CTVR
p
2
1
0
MV
SD
28 44 28 19 29 24 26
10 5 4 3 7 3 9
22 11 28 39 24 33 25
1.10 1.55 1.00 0.68 1.08 0.85 1.02
0.92 0.79 0.97 0.93 0.94 0.97 0.93
0.40 1.00 0.84 0.39 0.07 1.00 0.04*
* Comparison for different segments of three protocol with surgical findings. p > 0.05: no significant differences. The imaging assessments were quite coincidental to surgical findings. MV, score mean value; SD, standard deviation.
Y. Liu et al. / Computerized Medical Imaging and Graphics 38 (2014) 696–701
699
Table 2 Efficacy of three protocols. Segments
Protocols Section plane
Head of malleus Handle of malleus Malleoincudal joint Long limb of incus Body of incus Short limb of incus Stapes Superstructure
MPR
CTVR
p
SN (%)
SP (%)
AC (%)
p
SN (%)
SP (%)
AC (%)
p
SN (%)
SP (%)
AC (%)
0.000 0.000 0.000 0.000 0.000 0.000 0.61
83.78 81.63 79.41 68.42 89.66 82.14 12.50
13.04 90.90 88.46 90.24 80.65 90.63 95.00
56.67 83.33 83.33 83.33 85.00 86.66 40.00
0.000 0.000 0.000 0.000 0.000 – 0.001
86.48 87.76 91.18 94.74 87.50 – 75.00
78.26 90.90 80.76 82.93 82.14 – 75.00
66.66 88.33 86.67 86.66 85.00 – 75.00
0.000 0.000 0.000 0.000 0.000 0.000 0.000
86.48 95.42 76.47 94.74 80.51 89.28 80.00
73.91 81.82 76.92 90.24 87.50 93.75 85.00
81.67 93.33 76.67 91.67 83.33 91.67 81.67
SN, sensitivity; SP, specificity; AC, accuracy.
Table 3 Comparison of clarity. 2
Ossicle
Malleus
Exist
50
Imaging
Plane
MPR
CTVR
Clearly
16 32% 24 48% 10 20%
41 82% 3 6% 6 12%
48 96% –
Vague No show
p
2
Incus
p
35
2 4%
Plane 53.51
0.000 10 28.57% 13 37.14% 12 34.29%
Stapes superstructure
2
p
48.14
0.000
40 MPR
CTVR
27 77.14% 3 8.57% 5 14.29%
32 91.43% –
Plane 35.64
3 8.57%
0.000
0 4 10% 36 90%
MPR
CTVR
23 57.5% 7 17.5% 10 25.0%
23 57.5% 7 17.5% 10 25.0%
In all the 60 subjects who underwent operation, the cases with completed malleus (50), incus (35), stapes superstructures (40) were selected to assess the imaging of three different protocols via clearly, vague and no showing. p value (=0.000) explained that the statistical result with probability of error is 0.000.
Table 3. In all the 60 subjects who underwent operation, 50 cases had completed malleus, 35 had completed incus, and 40 had completed stapes superstructures. These subjects were selected to assess the imaging of three different protocols via clearly, vague and no showing. p value (=0.000) explained that the probability of error for the statistical result is 0.000. For malleus, the clear images were obtained 48(96%) from CTVR, 41(82%) from MPR, and only 16(32%) from conventional section plane. Furthermore, in section plane imaging, 10 cases (20%) have no images showing at all. Incus was present in 35 of the 60 subjects. Of these 35 cases, 32 (91.43%) have clear images from CTVR, 27(77.14%) from MPR and only 10 (28.57%) from conventional section plane. Here again, 12 cases (34.29%) in section plane showed no images. Also in this study, we found 40 cases of stapes superstructure. Of these 40, 23 cases (57.50%) have clear showings from CTVR, 23(57.50%) from MPR, and in section plane, 36 cases (90%) with no showings. It can be seen in Table 3 that both MPR and CTVR have significant advantages in showing ossicles images over that of conventional section plane. However, the images of stapes superstructure were not as good as that of malleus and incus. In middle ear cholesteatoma, the thin and smaller crus of stapes were surrounded by soft tissues, making it difficult to distinguish the stapes superstructure.
3.4. Case examples Fig. 4 is an image example of a patient with middle ear cholesteatoma. In the section plane (Fig. 4a1), the ossicles resemble an “ice cone” (the imaging of ossicles in this plane resembles the shape of ice cones). It was also not very clear. In the MPR image (Fig. 4b), we can clearly see the handle of malleus, the body of incus and soft tissues around the ossicular chain. In Fig. 4c1 and c2, the CTVR image of the ossicular chain can be observed directly and clearly. No long limb of incus was present in this instance. Fig. 5 shows another patient’s imaging with the ossicular chain surrounded by soft tissues. Here in the section plane, the ossicular chain cannot be clearly seen. However, using
CTVR, the ossicular chain is clearly visible when soft tissues are removed 4. Discussion Through CT section plane alone, it is difficult to accurately show the three ossicles in middle ear cavity. Moreover, for cholesteatoma with ossicular erosion and deformity, it is particularly difficult to show ossicular changes due to soft tissue density (such as in cholesteatoma matrix and granulation). Modern CT technology, including “multi-slice spiral scanning,” “volume scanning” and “isotropic scanning,” [4], allow data to be immediately transmitted to post-processing workstation where 3D images of ossicular chains are created. In recent years, the more popular reconstruction techniques have included MPR, CTVR and endoscopy (CTVE) [5]. In fact, it is common nowadays to combine these various techniques in the diagnosis of ossicular lesions [3]. CTVE imaging, which is based on shaded-surface displays (SSD-based CTVE), has been discussed by many authors [4–6]. Since CTVE barely shows 10% of data, loss of information are inevitable [1]. Its major disadvantage is its inability to distinguish bony tissues from soft tissues inside cavity filled with cholesteatoma [6,7]. To differentiate from previous other studies [1,2,4,5] where the ossicular chain was in well-aerated middle ear cavity (high density contrast between air and bone), we use CTVR and MPR protocols instead on patients with ossicular chain buried in soft tissue mass in middle ear cholesteatoma 4.1. Conventional axial and coronal section plane The conventional axial and coronal section plane primarily examines whether any air spaces or soft tissues are in middle ear cavity. This plane offers important structural information such as the cochlea [8]. However, its limitations are its vague showing of the ossicular chain, especially in middle ear cholesteatoma. Fuse T. et al. reported that pre-operative detection of total defects in the head of malleus, the body and long process of the incus via
700
Y. Liu et al. / Computerized Medical Imaging and Graphics 38 (2014) 696–701
Fig. 4. (a) Section planes of conventional CT. (a1) axial section; (a2 and a3) coronal section; (b) MPR imaging; (c1 and c2) CTVR imaging; (1) head of malleus; (2) handle of malleus; (3) malleoincudal joint; (4) body of incus; (6) incudostapedial joint; st, soft tissue.
high-resolution CT were possible in all their cases. Their analysis found the defect in the handle of the malleus and superstructure of the stapes to be 33.3% and 60%, respectively. In addition, partial defects of the stapes crus could not be correctly diagnosed by pre-operative estimation [9]. Their conclusion concurred with our results tabulated in Table 1. The p value (p = 0.00) of the handle of malleus and stapes superstructure is indicative that the assessment of these two segments in section plane were far different (or coincided badly) when compared to surgical findings in cholesteatoma surgery. According to Trojanowska A., the analysis of axial images alone does not provide sufficient information in ossicular diagnosis. Their sensitivity (89%) and specificity (87%) findings were all lower than those of MPR [3]. In our study, the sensitivity, specificity and accuracy levels of conventional section planes were also lower than that of MPR and CTVR as listed in Table 2, as were the clarity of ossicles depicted in conventional section plane (Table 3). 4.2. MPR imaging MPR imaging is more advantageous than section plane in showing different ossicular segments. The former is created by reformation of the pixels. In comparison to original 2D imaging, both resolution and contrasts are maintained [1]. One of the major
advantages of MPR is that it can show total and fine ossicular chains within the same layer via multi-directional adjustment [3,10]. Consequently, both soft and bony tissues are easily distinguishable. This is precisely what most otologists are chiefly concerned with during cholesteatoma surgery. Fig. 2a and b are examples of this feature of MPR with clear imaging of the ossicular chain and soft tissues. In terms of the efficacy of the three protocols for demonstration of the ossicles’ structures, Zhang LC et al. reported that MPR exhibited significant superiority in most structures [1]. Our statistical data (Table 2: MPR-AC: 66.66–88.33%) support their conclusions. UIIa M.B. (2008) also stated that the anatomic and pathologic characterization of middle ear structure can be improved using the MPR technique [11]. In his pre-operative imaging assessment of ossicles in 30 chronic suppurative otitis media with cholesteatoma patients, Pandey described that their assessments were satisfactory in larger ossicular parts. However, in the evaluation of stapes superstructure, their accuracy of MPR (in multiplanar 2D reformation) was only 76.97% [12]. In our study, it was 75% for MPR but 40% for section plane. This is indicative that MPR can reveal anatomical features and pathologic conditions more precisely than in section plane. For precise surgical planning and diagnosis of diseases, the MPR visualization in middle ear and adjacent structures are ideal.
Fig. 5. (a) Coronal section plane of conventional CT; (b) MPR imaging; (c1 and c2) CTVR imaging; with soft tissues (st) of cholesteatoma around the ossicular chain filtered out (c1 ) and the whole ossicular chain exposed with no long limb of incus; (1) handle of malleus; (4) body of incus; h, head of stapes; vw, vestibular window; st, soft tissue; ss, superstructure of stapes (vague). No long limb of incus exists in this case.
Y. Liu et al. / Computerized Medical Imaging and Graphics 38 (2014) 696–701
701
4.3. 3D- CTVR imaging
Conflict of interest
In our study, the CTVR technique was the key method used. In our study for CTVR technique, the six lines on coronal and axial referenced images were defined in the post-processing workstation. Furthermore, two standard fields of view were selected according to the surgical field. In order to define an ossicular destruction well, a wide range of window was used. As a result, the 3D imagings of ossicular chain structures were got far better here. In the majority of previous studies, the 3D CTVE protocol, as a surface-rendering technique, was the main procedure used to perform 3D-reconstruction [7,11,13,14]. In middle ear cholesteatoma, the ossicular chain is usually surrounded by granulation and/or cholesteatoma. For this reason, the surrounding “irrelevant structures” of ossicles should be dissected in order that the ossicular chain buried in the soft tissue can be showed completely. Here too, we found the threshold filtering feature of CTVR better enables radiologists and otologists to assess the pathological status of the ossicular chain after soft tissues around it are removed. This is actually CTVR’s major advantage over all the other 3D techniques. Jang reported that in 15 of his patients with chronic otitis media with cholesteatoma, the 3D-CT clearly outlined the damaged bony structures [17]. Our typical case study in Fig. 5c1 and c2 visibly show the exposed abnormal ossicular chain after soft tissues of the cholesteatoma were removed. As can be seen in Table 1, all of our data for quantitative assessment in various segments of CTVR are superior to section plane. The p values of stapes superstructure for MPR and CTVR in our case were 0.04 in middle ear cholesteatoma. Even though this indicated that representation of stapes superstructure were unsatisfactory in MPR and CTVR, it is still better than in section plane. These findings coincide with that of Zhang et al. [1]. In the overall analysis, the efficacy of CTVR in various segments are superior to that of section plane. With regard to clarity assessments of these three protocols, CTVR ranked highest, followed by MPR, with section plane third.
Authors declare that they have no conflicts of interest concerning this article.
5. Conclusion Our final analysis of quality for the three protocols in the fine diagnosis of ossicles buried within the cholesteatoma is that both MPR and CTVR remain superior to conventional section plane. We believe that MPR and CTVR are invaluable protocols in the diagnosis of ossicular chain in middle ear cholesteatoma. We also believe that the combination use of these two protocols, along with conventional axial and coronal section plane, could be the way to go in future pre-operative ossicular chain diagnosis. Except for the fine diagnosis of ossicular chain in the cholesteatoma, the VR and MPR technology can also be used well in the differential diagnosis of otosclerosis, tympanosclerosis, interruption of the ossicular chain, and ossicular malformation. In the assessment of implanted ossicular prosthesis, it can also give well showing.
Acknowledgements We thank Prof. Jie Chen for generously providing his assistance in the statistical portion of our study. Prof. Chen: Department of Statistics, Peking University People’s Hospital, Beijing, 100044, China References [1] Zhang LC, Sha Y, Wang ZM, Luo DT, Huang WH, Dai PD, et al. 3D image of the middle ear ossicles: three protocols of post-processing based on multislice computed tomography. Eur Arch Otorhinolaryngol 2011;268(May (5)):677–83. [2] Fatterpekar GM, Doshi AH, Dugar M, Delman BN, Naidich TP, Som PM. Role of 3D CT in the evaluation of the temporal bone. Radiographics 2006;26(October (Suppl. 1)):S117–32 [review]. [3] Trojanowska A, Trojanowski P, Olszanski W, Klatka J, Drop A. How to reliably evaluate middle ear diseases? Comparison of different methods of postprocessing based on multislice computed tomography examination. Acta Otolaryngol 2007;127(March):258–64. [4] Fujii N, Inui Y, Katada K. Temporal bone anatomy: correlation of multiplanar reconstruction sections and three-dimensional computed tomography images. Jpn J Radiol 2010;28(November (9)):637–48. [5] Ho AC, Lee R, Co MT, Chow Ck, Au Yeung KM. Is virtual endoscopy of the middle ear useful? Ear Nose Throat J 2011;90(June (6)):256–60. [6] Chen DY, Chen XW, Wang Y, Cao KL, Jin ZY. Virtual otoscopy of middle ear structure and pathology. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi 2005;40(January (1)):18–21 [article in Chinese]. [7] Jiang LX, Ma YK, Luo D, Yang N, Li YZ. Evaluation of the virtual endoscopy on traumatic ossicular chain disruption pre- and post-operation. Zhonghua Er Bi Yan Hou Tou Jing Wai Ke Za Zhi 2008;43(April (4)):272–6. [8] Tan TY, Goh JP. Imaging of congenital middle ear deafness. Ann Acad Med Singapore 2003;32(July (4)):495–9 [review]. [9] Fuse T, Aoyagi M, Koike Y, Sugai Y. Diagnosis of the ossicular chain in the middle ear by high-resolution CT. ORL J Otorhinolaryngol Relat Spec 1992;54(5): 251–4. [10] Gong RZ, Chao BT, Liu K, Fan ZM, Wang HB, Chen QH, et al. CT multiplan reconstruction images of disorder of stapes. Zhonghua Er Bi Yan Hou Ke Za Zhi 2004;39(May (5)):265–8. [11] Blanco Ulla M, Vázquez F, Pumar JM, et al. Oblique multiplanar reformation in multislice temporal bone CT. Surg Radiol Anat 2009;31(July (6)):475–9. [12] Pandey AK, Bapuraj JR, Gupta AK, Gupta AK, Khandelwal N. Is there a role for virtual otoscopy in the preoperative assessment of the ossicular chain in chronic suppurative otitis media? Comparison of HRCT and virtual otoscopy with surgical findings. Eur Radiol 2009;19(6):1408–16. [13] Himi T, Sakata M, Shintani Mitsuzawa H, Kamagata M, Satoh J, et al. Middle ear imaging using virtual endoscopy and its application in patients with ossicular chain anomaly. ORL J Otorhinolaryngol Relat Spec 2000;62(November–December (6)):316–20. [14] Rodt T, Bartling S, Schmidt AM, Weber BP, Lenarz T, Becker H. Virtual endoscopy of the middle ear: experimental and clinical results of a standardised approach using multi-slice helical computed tomography. Eur Radiol 2002;12(July (7)):1684–92. [17] Jang CH, Wang PC. Preoperative evaluation of bone destruction using three-dimensional computed tomography in cholesteatoma. J Laryngol Otol 2004;118(October (10)):827–9.