- Email: [email protected]
Stereotactic brain biopsy using a narrow aperture computed tomography scanner
ClinicalRadiology(1984) 35, 209-214 © 1984 Royal College of Radiologists
0009-9260/84/282209502.00
Stereotactic Brain Biopsy Using a Narrow Aperture Computed Tomography Scanner* G. S. M. T H O M S O N , D. P. E. K I N G S L E Y , F. A F S H A R and I. G. W Y L I E
Department of Radiodiagnosis, Section of Neurological Sciences, The London Hospital, London
A technique for stereotactic brain biopsy with guidance by computed tomography (CT) has been developed and the procedure carried out on a series of 12 patients. A head fixation device, based on the Leksell method, has been designed which allows exact transfer of CT co-ordinates to a Bennett stereotactic frame for the purpose of the biopsy. The development and initial experience of this stereotactic technique in 12 cases is reported and the accuracy of the method confirmed by histological examination and post-operative CT verification of the biopsy site, by means of a small marker inserted at the time of surgery.
The history of stereotaxis can be traced back to Z e r n o v ' s original demonstration of his encephalometer which was intended for neurosurgical procedures and anatomical studies of the h u m a n brain (Zernov, 1889). There is little documentation regarding its use, but it appears to have been employed in brain mapping and in the localisation of cerebral structures prior to surgery. The apparatus was later improved by Rossolimo (1907), but it was not until some 40 years later that Spiegel and Wycis (1952) introduced stereotaxis and stereo-encephalotomy into neurosurgery using the modified apparatus of Clarke and Horsley (1906). Since then, m a n y authors (Chernak et al., 1975; M a r o o n et al., 1977; James et al., 1979; Greitz et al., 1980) have shown the advantages of being able to combine c o m p u t e d t o m o g r a p h y (CT) with stereotaxis to obtain an accurate tissue diagnosis of intracranial lesions, particularly those close to vital centres. Each tomographic slice of a CT scan is a compound image based on a matrix system such that each picture element (pixel) is defined by a set of co-ordinates (x, y, z), allowing accurate localisation of a lesion. A similar co-ordinate system can be ascribed to any neurosurgical stereotactic f r a m e permitting the exact transfer of CT co-ordinates, by means of a head fixation device, without reference to anatomical landmarks.
aluminium tipped polypropylene screws (Fig. 1) applied directly to the scalp, without incising the skin (Fig. 2). The patient is transferred to the CT scanner and the base ring located into a special head support bracket attached to the scanner couch. A bolus of contrast medium (35-45 g iodine) is given intravenously and scanning proceeds until the whole of the lesion has been demonstrated. The x and y (axial) co-ordinates of the point chosen for biopsy and the centre of the aperture are established
Fig. 1 - Individual components of the modified Leksell stereotactic system showing the base ring (A) to which four L-shaped brackets (B) are attached (black arrows). The base ring is connected by the four catches (open arrows) to the four studs (arrowheads) of the U-shaped head support (C) which, in turn, locates into the patient couch head support bracket during the scanning procedure.
M A T E R I A L S AND M E T H O D S Following induction of general anaesthesia and head preparation the base ring is attached to the patient's head by means of four L-shaped brackets and four Address for reprints: Dr G. S. M. Thomson, Department of Radiodiagnosis, The London Hospital, Whitechapel, London E1 1BB. *Part of this material was used for a presentation delivered at the Annual General Meeting of the Royal College of Radiologists, London, 17 June 1983.
Fig. 2 - Assembled stereotactic CT system for head scanning.
210
CLINICAL RADIOLOGY
Fig. 3 - Pre-biopsyscan after intravenouscontrast medium. The centre of the scanner aperture (open arrow) and the chosenbiopsysite (black arrow) are denoted. The x and y co-ordinates of the biopsy site are printed on the scan imageusing a character generator (L +50, W 100).
using the line function facility of the diagnostic enhancement package for the EMI CT 1010 scanner (Fig. 3). The latter centre point has to be established and checked regularly by CT against a phantom, referencing the centre of the Bennett stereotactic frame, to exclude physical distortion of the interconnecting units. The height of the lesion from the base ring, or the z co-ordinate, is calculated from the distance the patient has travelled between the zero position and the chosen scan slice using a digital counter fixed to the scanner couch. A simple conversion factor is, therefore, all that is necessary to transpose these three co-ordinates to the
Bennett stereotactic frame. A conversion program for a microprocessor has been Written which not only carries out these calculations but permits other checks of accuracy to be incorporated into the system, as well as allowing a record of each patient procedure to be made (Fig. 4). The patient is transferred to the operating theatre where the Bennett stereotactic frame is attached to the base ring using the same four catches which attach the base ring to the scanner head support (Fig. 5a). The depth of the cannula tip is determined using a simulator (Fig. 5b), so that once the arc has been attached (Fig. 5c) and the co-ordinates set on the frame, the cannula can be introduced at any angle as the tip will always locate to the centre of the target. This eliminates the need for calculating trajectory angles in advance, so the position of the burr hole can be chosen on anatomical considerations alone. After the biopsy and frozen section or smear have been obtained, a small, barium-impregnated sphere, 0.75 mm in diameter is passed through the cannula and left at the site of biopsy. The wound is closed, the stereotactic frame removed and the patient, still anaesthetised and with the head fixation device attached, is returned to the X-ray department for a post-biopsy scan using the same co-ordinate parameters. No contrast medium is given as the location of the biopsy site is shown by the barium-impregnated sphere (Fig. 6), the co-ordinates of which are compared with those of the lesion on the initial scan (Fig. 4).
RESULTS The procedure has been performed on 12 patients, seven of whom were males and five females, including one patient who had previously had a negative open craniotomy (Fig. 7). Their ages ranged from 25 years to
B E N N E T T FRAME C O N V E R S I O N ........................ (Pre-btoply) Name No Born Examined
T.W. 17578-48L 04 02 11 19 05 83
Centre Lesion (C.T) Lesion(B.F) From c e n t r e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x Y Z
80 px 80 px 3 0 . 0 0 cm
100 px 68 px 3 0 . 0 0 cm (B)
1 . 9 0 cm 5 . 2 0 cm 1 . 0 0 cm
3 . 0 0 cm r i g h t 1 . 8 0 cm a n t
BENNETT FRAME CONVERSION ........................ (Post-biopsy) Name NO Born Examlned
T.W. 17578-48L 04 02 11 19 05 83
Center Marker (C.T) Errors ........................................... X Y Z
80 px 80 px 3 0 . 0 0 cm
101 px 67 px 3 0 . 0 0 cm (B)
(W.r.t
pre-biopsy)
. 1 5 cm . 1 5 cm . 0 0 cm
DIAGNOSIS ASTROCYTOMA, MEDIUM COMMENT:- DEEP MEDIAL TEMPORAL LESION. CLOSE TO BRAIN STEM AND MAJOR VESSELS MARKER : - BA SPHERE TAPE : - 261 SLOT = - 1 9 5 - 2 0 0 .
Fig. 4 - Printout of the pre- and post-biopsy information using simple computer software developed for a standard microprocessor.
211
S T E R E O T A C T I C B R A I N B I O P S Y U S I N G CT
(b)
(a) Fig~.5 - (a) The patient is positioned using the same four catches on the base ring and four identical studs on a plate attached to the Bennett apparatus, allowing direct transfer of the co-ordinates. (b) The depth of the cannula tip which lies at the centre of the arc is calculated on the simulator. (c) The arc is then attached to the frame and its position established from the co-ordinates transferred from the CT scanner, so that the chosen site is at the tip of the cannula and is not dependent upon the angle of trajectory.
(c)
73 y e a r s a n d b i o p s y r e v e a l e d 10 g l i o m a s a n d two metastases. T h e m e a n errors in the x a n d y axes were 1 . 5 9 m m and 1.49 m m , r e s p e c t i v e l y , w h i c h is e q u i v a l e n t to o n e pixel in e i t h e r d i r e c t i o n . T h e e r r o r in the z axis is h a r d e r to assess as C T scans o f 1 0 m m n o m i n a l t h i c k n e s s h a v e been performed and the study would require thinner scan slices to e v a l u a t e this m o r e a c c u r a t e l y . H o w e v e r , t h e s p h e r e has always b e e n l o c a t e d on the slice c o r r e s p o n d i n g to t h a t c h o s e n b e f o r e b i o p s y . T h e r e has b e e n no m o r b i d i t y o r m o r t a l i t y as a d i r e c t r e s u l t of t h e p r o c e d u r e , a l t h o u g h o n e p a t i e n t d i e d 5 d a y s after t h e p r o c e d u r e f r o m a p u l m o n a r y e m b o l u s , c o n f i r m e d at a u t o p s y . O n m a c r o s c o p i c e x a m i n a t i o n of t h e b r a i n the s p h e r e was l o c a t e d in t h e p o s t e r i o r c a p s u l e o f t h e t u m o u r at t h e p o s i t i o n d e m o n s t r a t e d on the p o s t - b i o p s y scan (Fig. 8). In two p a t i e n t s , clinical i m p r o v e m e n t f o l l o w e d a s p i r a t i o n of cyst fluid.
DISCUSSION With freehand biopsy techniques, multiple trajectories m a y be r e q u i r e d b e f o r e t h e lesion is l o c a t e d , with an
Fig. 6 - Same patient as Fig. 3. The site of biopsy marked by a barium impregnated sphere (arrowed) is seen and its co-ordinates, printed on the scan image, are within one pixel of the pre-operative co-ordinates (L +50, W 100).
212
CLINICAL RADIOLOGY
(a)
(b)
Fig. 7 - (a) CT scan after contrast medium.The site of the previous open craniotomy biopsy (black arrow) and the chosen position for the stereotactic biopsy (open arrow) are indicated (L +15, W75). (b) Post-operative CT scan showing the barium impregnated sphere at the biopsy site with the corresponding co-ordinates (L +9, W 100).
increased risk of causing cerebral haemorrhage and worsening cerebral oedema, which may already be present. Computed tomography-assisted stereotaxis has now become an established technique and is being increasingly used in the primary diagnosis of many types of intracranial lesion (Bo6thius et al., 1978; Ostertag et al., 1980; Perry et al., 1980; Broggi and Franzini, 1981; Koslow et al., 1981; Wester et al., 1981). It is the method of choice in tumours which are either small, deep seated, cystic or unresectable and has also been used in the evacuation of cerebral abscesses and acute, small, central haematomas (James et al., 1979; Moran et al., 1979; Wise and Gteason, 1979; Shelden et al., 1980; Anderson et al., 1983). Several CT stereotactic techniques have been described based on two fundamental methods: those that combine a head fixation device, suitable for scanning, with a conventional neurosurgical stereotactic frame and those where the biopsy is performed with the patient in the CT scanner, with per-operative scans to determine the trajectory and depth of the cannula. Most systems require the use of a wide-aperture scanner, either because the head frame is too bulky to fit into a dedicated head scanner (Brown, 1979a; Patil, 1982; Anderson et al., 1983) or because the stereotactic procedure can only be performed satisfactorily in the extra space afforded by a wide-aperture scanner (Hahn etal., 1979; James etal., 1979; Moran etal., 1979). One of the features of this system, derived from that developed at the Karolinska Hospital, Stockholm for use with EMI Mark 1 scanner and a modifed Leksell frame (Leksell, 1971; Bergstr6m and Greitz, 1976), is that it can be carried out in a narrow-aperture scanner. It could, if desired, be modified for per-operative CT scanning, but the advantages of a reduced procedure time and repeated CT verification of the position of the cannula tip compared with the more conventional operating theatre biopsy technique may be outweighed
by an increased risk of infection (Penn et al., 1978; Brown, 1979a). The reliability of the system has been verified by the constancy of the position of the sphere on the post-biopsy scans. In other techniques the accuracy has been established by experimentation with phantoms, as no marker is inserted at the time of surgery (Brown, 1979b; Patil, 1982). This technique and others simulate the position of the cannula tip prior to biopsy but slight displacement of the cannula could, theoretically, occur in vivo due to resistance of the brain substance. Confirmation of the accuracy of the biopsy site by means of an implanted barium-impregnated sphere was, therefore, preferred to the bubble of air or small haematoma which may indicate the biopsy site (Moran et al., 1979; Anderson et al., 1983) but which may be too small or diffuse to localise it sufficiently accurately. The application of the head fixation device is quick and simple and the position of the head within the scanner is not critical since the co-ordinates are referred to the base ring of the head fixation device. Furthermore, there is no need to correct for magnification, allow for parallax, or take into account rotation of the head, factors which may introduce a significant error in localisation of the position of lesions, especially those situated peripherally (Gleason et al., 1978; Penn et al., 1978; Goerss et al., 1982). Other techniques require the head to be aligned within the CT scanner so that the lesion and the intended site of the burr hole are visualised on the same plane. Preliminary scans with scalp markers are, therefore, required prior to trephine and biopsy (Moran et al., 1979; Wester etal., 1981; Patil, 1982). The four percutaneous screws applied directly to the scalp eliminate the need for twist drill fixation (Bo6thius et al., 1980; Goerss et al., 1982). The new screws, made from aluminium tipped polypropylene, and brackets, made of carbon fibre, are virtually free from artefact
213
S T E R E O T A C T I C B R A I N B I O P S Y U S I N G CT
(a)
(b)
Fig. 8 - (a) Post-biopsy CT scan demonstrating the barium sphere with a small amount of air within the tumour but anterior to the sphere; also in the subdural space (L +50, W 100). (b) Cut brain slice through the tumour showing the position of the sphere in the posterior part of the tumour.
distortion, a problem encountered with the original aluminium design. Neither does the cannula produce artefact distortion which might interfere with the biopsy of small lesions in per-operative scanning techniques (Moran et al., 1979; Penn, 1979). This series of 12 cases is too small to establish the safety of the procedure, but the absence of mortality and morbidity, particularly without the use of steroids, compares favourably, so far, with other series. A mortality rate of 1-2% and morbidity of 2 - 4 % have been reported (Heath et al., 1961; Marshall et al., 1974; Spence et al., 1974; Edner, 1975; Shetter et al., 1977) although, m o r e recently, a lower incidence of complications has been attributed to refinements in technique and the use of steroids in the per-operative period (Gleason et al., 1978; H a h n et al., 1979; James et al., 1979). I m p r o v e m e n t in the patients' neurological status following aspiration of cyst fluid from large necrotic tumours has been reported (James et al., 1979; Moran et al., 1979). In this series of 12 cases, two patients showed clinical i m p r o v e m e n t following stereotactic biopsy and fluid aspiration. The m a j o r disadvantages of the present procedure are the times taken to induce general anaesthesia and to transport the patient between the CT scanner and the operating theatre. Some centres perform stereotactic brain biopsy under sedation but, because of the distance between our CT scanner and operating theatre, it was
not considered appropriate for the procedure to be p e r f o r m e d under local anaesthesia. This system also requires the use of a neurosurgical stereotactic headframe, which is not needed by those methods employing a freehand biopsy technique. Despite these disadvantages, the procedure has proved to be reliable, simple to p e r f o r m and relatively inexpensive, but it does require close co-operation between the radiologist and neurosurgeon.
Acknowledgements. We would like to thank Miss Helen Davies for typing the manuscript, the radiographers for their assistance during the scanning procedure, Mr Henry Lawrence for his help with the computer program and the photographic department for the preparation of the illustrations.
REFERENCES
Anderson, R. E., Thomas, D. G. T. & du Boulay, G. H. (1983). Radiological aspects of CT guided stereotactic neurosurgical procedures. Neuroradiology, 24, 163-166. Bergstr6m, M. & Greitz, T. (1976). Stereotaxic computed tomography. American Journal of Roentgenology, 127, 167-170. Bo6thius, J., Collins, V. P., Edner, G., Lewander, R. & Zajicek, J. (1978). Stereotactic biopsies and computer tomography in gliomas. Acta Neurochirurgica, 40, 223-232. Bo6thius, J., Bergstr6m, M. & Greitz, T. (1980). Stereotaxic computerized tomography with a G.E. 8800 scanner. Journal of Neurosurgery, 52, 794-800.
214
CLINICAL RADIOLOGY
Broggi, G. & Franzini, A. (1981). Value of serial stereotactic biopsies and impedance monitoring in the treatment of deep brain tumours. Journal of Neurology, Neurosurgery and Psychiatry, 44, 39%401. Brown, R. A. (1979a). A stereotactic head frame for use with CT body scanners, investigative Radiology, 14, 300-304. Brown, R. A. (1979b). A computerized tomography-computer graphics approach to stereotaxic localization. Journal of Neurosurgery, 50, 715-720. Chernak, E. S., Rodriguez-Antunez, A., Jelden, G. L., Dhaliwal, R. S. & Lavik, P. S. (1975). The use of computed tomography for radiation therapy treatment planning. Radiology, 117, 613-614. Clarke, R. H. & Horsley, V. (1906). On a method of investigating the deep ganglia and tracta of the central nervous system (cerebellum). British Medical Journal, il, 1799-1800. Edner, G. (1975). Stereotaxic brain tumour biopsy - 5 years experience. Acta Neurochirurgica (Wien), 3, 261. Gleason, C. A., Wise, B. L. & Feinstein, B. (1978). Stereotactic localization (with computerized tomographic scanning), biopsy and radiofrequency treatment of deep brain lesions, Neurosurgery, 2, 217-223. Goerss, S., Kelly, P. J., Kall, B. & Alker, G. J., Jr (1982). A computed tomographic adaptation system. Neurosurgery, 10, 375-379. Greitz, T., Bergstr6m, M., Bo6thius, J., Kingsley, D, & Ribbe, T. (1980). Head fixation system for investigation of radiodiagnostic and therapeutic procedures. Neuroradiology, 19, 1-6. Hahn, J. F., Levy, W. J. & Weinstein, M. J. (1979). Needle biopsy of intracranial lesions guided by computerised tomography. Neurosurgery, 5, 11-15. Heath, R. G., John, S. & Foss, O. (1961). Stereotaxic biopsy. A method for the study of discrete brain regions of animals and man. Archives" of Neurology, 4, 291-300. James, H. E., Wells, M., Alksne, J. F., Wickbom, I., Siemers, P., Brahme, F. & Rosenberg, J. (1979). Needle biopsy under computerized tomographic control: a method for tissue diagnosis in intracranial lesions. Neurosurgery, 5, 671-674. Koslow,M., Abele, M. G., Griffith, R. C., Mair, G. A. & Chase, N. E. (1981). Stereotactic surgical system controlled by computed tomography. Neurosurgery, 8, 72-82. Leksell, L. (1971). Stereotaxis and Radiosurgery. An Operative System. Charles C. Thomas, Springfield, Illinois. Maroon, J. G., Bank, W. O., Drayer, B. P. & Rosenbaum, A. E. (1977). Intracranial biopsy assisted by computerized tomography. Journal of Neurosurgery, 46, 740-744. Marshall, L. F., Jennett, B. & Langfitt, T. W. (1974). Needle biopsy for the diagnosis of malignant glioma. Journal of the American Medical Association, 228, 141%1418.
Moran, C. J., Naidich, T. P., Gado, M. H. & Marchosky, J. A. (1979). Central nervous system lesions biopsied or treated by CT guided needle placement. Radiology, 131, 681-686. Ostertag, C. B., Mennel, H. D. & Kiessling, M. I. (1980). Stereotactic biopsy of brain tumours. Surgical Neurology, 14, 275-283. Patil, A. A. (1982). Computed tomography-orientated stereotacfic system. Neurosurgery, 10, 370-373. Penn, R. D., Whisler, W. W., Smith, C. A. & Yasnoff, W. A. (1978). Stereotactic surgery with image processing of computerised tomographic scan. Neurosurgery, 3, 157-161. Penn, R. D. (1979). 'Comments'. (In response to paper by Hahn et al. (1979).) Neurosurgery, 5, 14-15. Perry, J. H., Rosenbaum, A. E., Lunsford, L. D., Swink, C. A. & Zorab, D. S. (1980). Computed tomography-guided stereotactic surgery: conception and development of a new stereotactic methodology. Neurosurgery, 7, 376--381. Rossolimo, G. I. (1907). 'Brain Topograph'. A device for projection on the cranium of brain convolutions. Magazine of Korsakov, 4, 639. Shetter, A. G., Bertuccini, T. V. & Pittman, H. W. (1977). Closed needle biopsy in the diagnosis of intra-cranial mass lesions. Surgical Neurology, 8, 341-345. Shelden, C. H., McCann, G., Jaques, S., Lutes, H. R., Frazier, R. E., Katz, R. & Kuki, R. (1980). Development of a computerized microstereotaxic method for localization and removal of minute CNS lesions under direct 3-D vision. Journal of Neurosurgery, 52, 21-27. Spence, J. W., Richards, D. E. & Nulsen, F. E. (1974). Indications for brain tumour biopsy by trephine and needle: review of results. Presented at the 42nd Annual Meeting of the American Association of Neurological Surgeons, St Louis, Missouri, 24 April. Spiegel, E. A. & Wycis, H. T. (1952). Stereoencephalotomy. Methods" and Stereotaxic Atlas of Human Brain. Grune and Stratton, New York. Wester, K., Sortland, O. & Hauglie-Hanssen, E. (1981). A simple and inexpensive method for CT-guided stereotaxy. Neuroradiology, 20, 255-256. Wise, B. L. & Gleason, C. A. (1979). CT-directed stereotactic surgery in the management of brain abscesses. Annals of Neurology, 6, 457. Zernov, D. N. (1889). Encephalometer. A device for determination of the location of brain parts of living human. Demonstrated at the Meeting of Society of Physics and Medicine of Moscow University, 22 March.
0009-9260/84/282209502.00
Stereotactic Brain Biopsy Using a Narrow Aperture Computed Tomography Scanner* G. S. M. T H O M S O N , D. P. E. K I N G S L E Y , F. A F S H A R and I. G. W Y L I E
Department of Radiodiagnosis, Section of Neurological Sciences, The London Hospital, London
A technique for stereotactic brain biopsy with guidance by computed tomography (CT) has been developed and the procedure carried out on a series of 12 patients. A head fixation device, based on the Leksell method, has been designed which allows exact transfer of CT co-ordinates to a Bennett stereotactic frame for the purpose of the biopsy. The development and initial experience of this stereotactic technique in 12 cases is reported and the accuracy of the method confirmed by histological examination and post-operative CT verification of the biopsy site, by means of a small marker inserted at the time of surgery.
The history of stereotaxis can be traced back to Z e r n o v ' s original demonstration of his encephalometer which was intended for neurosurgical procedures and anatomical studies of the h u m a n brain (Zernov, 1889). There is little documentation regarding its use, but it appears to have been employed in brain mapping and in the localisation of cerebral structures prior to surgery. The apparatus was later improved by Rossolimo (1907), but it was not until some 40 years later that Spiegel and Wycis (1952) introduced stereotaxis and stereo-encephalotomy into neurosurgery using the modified apparatus of Clarke and Horsley (1906). Since then, m a n y authors (Chernak et al., 1975; M a r o o n et al., 1977; James et al., 1979; Greitz et al., 1980) have shown the advantages of being able to combine c o m p u t e d t o m o g r a p h y (CT) with stereotaxis to obtain an accurate tissue diagnosis of intracranial lesions, particularly those close to vital centres. Each tomographic slice of a CT scan is a compound image based on a matrix system such that each picture element (pixel) is defined by a set of co-ordinates (x, y, z), allowing accurate localisation of a lesion. A similar co-ordinate system can be ascribed to any neurosurgical stereotactic f r a m e permitting the exact transfer of CT co-ordinates, by means of a head fixation device, without reference to anatomical landmarks.
aluminium tipped polypropylene screws (Fig. 1) applied directly to the scalp, without incising the skin (Fig. 2). The patient is transferred to the CT scanner and the base ring located into a special head support bracket attached to the scanner couch. A bolus of contrast medium (35-45 g iodine) is given intravenously and scanning proceeds until the whole of the lesion has been demonstrated. The x and y (axial) co-ordinates of the point chosen for biopsy and the centre of the aperture are established
Fig. 1 - Individual components of the modified Leksell stereotactic system showing the base ring (A) to which four L-shaped brackets (B) are attached (black arrows). The base ring is connected by the four catches (open arrows) to the four studs (arrowheads) of the U-shaped head support (C) which, in turn, locates into the patient couch head support bracket during the scanning procedure.
M A T E R I A L S AND M E T H O D S Following induction of general anaesthesia and head preparation the base ring is attached to the patient's head by means of four L-shaped brackets and four Address for reprints: Dr G. S. M. Thomson, Department of Radiodiagnosis, The London Hospital, Whitechapel, London E1 1BB. *Part of this material was used for a presentation delivered at the Annual General Meeting of the Royal College of Radiologists, London, 17 June 1983.
Fig. 2 - Assembled stereotactic CT system for head scanning.
210
CLINICAL RADIOLOGY
Fig. 3 - Pre-biopsyscan after intravenouscontrast medium. The centre of the scanner aperture (open arrow) and the chosenbiopsysite (black arrow) are denoted. The x and y co-ordinates of the biopsy site are printed on the scan imageusing a character generator (L +50, W 100).
using the line function facility of the diagnostic enhancement package for the EMI CT 1010 scanner (Fig. 3). The latter centre point has to be established and checked regularly by CT against a phantom, referencing the centre of the Bennett stereotactic frame, to exclude physical distortion of the interconnecting units. The height of the lesion from the base ring, or the z co-ordinate, is calculated from the distance the patient has travelled between the zero position and the chosen scan slice using a digital counter fixed to the scanner couch. A simple conversion factor is, therefore, all that is necessary to transpose these three co-ordinates to the
Bennett stereotactic frame. A conversion program for a microprocessor has been Written which not only carries out these calculations but permits other checks of accuracy to be incorporated into the system, as well as allowing a record of each patient procedure to be made (Fig. 4). The patient is transferred to the operating theatre where the Bennett stereotactic frame is attached to the base ring using the same four catches which attach the base ring to the scanner head support (Fig. 5a). The depth of the cannula tip is determined using a simulator (Fig. 5b), so that once the arc has been attached (Fig. 5c) and the co-ordinates set on the frame, the cannula can be introduced at any angle as the tip will always locate to the centre of the target. This eliminates the need for calculating trajectory angles in advance, so the position of the burr hole can be chosen on anatomical considerations alone. After the biopsy and frozen section or smear have been obtained, a small, barium-impregnated sphere, 0.75 mm in diameter is passed through the cannula and left at the site of biopsy. The wound is closed, the stereotactic frame removed and the patient, still anaesthetised and with the head fixation device attached, is returned to the X-ray department for a post-biopsy scan using the same co-ordinate parameters. No contrast medium is given as the location of the biopsy site is shown by the barium-impregnated sphere (Fig. 6), the co-ordinates of which are compared with those of the lesion on the initial scan (Fig. 4).
RESULTS The procedure has been performed on 12 patients, seven of whom were males and five females, including one patient who had previously had a negative open craniotomy (Fig. 7). Their ages ranged from 25 years to
B E N N E T T FRAME C O N V E R S I O N ........................ (Pre-btoply) Name No Born Examined
T.W. 17578-48L 04 02 11 19 05 83
Centre Lesion (C.T) Lesion(B.F) From c e n t r e . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x Y Z
80 px 80 px 3 0 . 0 0 cm
100 px 68 px 3 0 . 0 0 cm (B)
1 . 9 0 cm 5 . 2 0 cm 1 . 0 0 cm
3 . 0 0 cm r i g h t 1 . 8 0 cm a n t
BENNETT FRAME CONVERSION ........................ (Post-biopsy) Name NO Born Examlned
T.W. 17578-48L 04 02 11 19 05 83
Center Marker (C.T) Errors ........................................... X Y Z
80 px 80 px 3 0 . 0 0 cm
101 px 67 px 3 0 . 0 0 cm (B)
(W.r.t
pre-biopsy)
. 1 5 cm . 1 5 cm . 0 0 cm
DIAGNOSIS ASTROCYTOMA, MEDIUM COMMENT:- DEEP MEDIAL TEMPORAL LESION. CLOSE TO BRAIN STEM AND MAJOR VESSELS MARKER : - BA SPHERE TAPE : - 261 SLOT = - 1 9 5 - 2 0 0 .
Fig. 4 - Printout of the pre- and post-biopsy information using simple computer software developed for a standard microprocessor.
211
S T E R E O T A C T I C B R A I N B I O P S Y U S I N G CT
(b)
(a) Fig~.5 - (a) The patient is positioned using the same four catches on the base ring and four identical studs on a plate attached to the Bennett apparatus, allowing direct transfer of the co-ordinates. (b) The depth of the cannula tip which lies at the centre of the arc is calculated on the simulator. (c) The arc is then attached to the frame and its position established from the co-ordinates transferred from the CT scanner, so that the chosen site is at the tip of the cannula and is not dependent upon the angle of trajectory.
(c)
73 y e a r s a n d b i o p s y r e v e a l e d 10 g l i o m a s a n d two metastases. T h e m e a n errors in the x a n d y axes were 1 . 5 9 m m and 1.49 m m , r e s p e c t i v e l y , w h i c h is e q u i v a l e n t to o n e pixel in e i t h e r d i r e c t i o n . T h e e r r o r in the z axis is h a r d e r to assess as C T scans o f 1 0 m m n o m i n a l t h i c k n e s s h a v e been performed and the study would require thinner scan slices to e v a l u a t e this m o r e a c c u r a t e l y . H o w e v e r , t h e s p h e r e has always b e e n l o c a t e d on the slice c o r r e s p o n d i n g to t h a t c h o s e n b e f o r e b i o p s y . T h e r e has b e e n no m o r b i d i t y o r m o r t a l i t y as a d i r e c t r e s u l t of t h e p r o c e d u r e , a l t h o u g h o n e p a t i e n t d i e d 5 d a y s after t h e p r o c e d u r e f r o m a p u l m o n a r y e m b o l u s , c o n f i r m e d at a u t o p s y . O n m a c r o s c o p i c e x a m i n a t i o n of t h e b r a i n the s p h e r e was l o c a t e d in t h e p o s t e r i o r c a p s u l e o f t h e t u m o u r at t h e p o s i t i o n d e m o n s t r a t e d on the p o s t - b i o p s y scan (Fig. 8). In two p a t i e n t s , clinical i m p r o v e m e n t f o l l o w e d a s p i r a t i o n of cyst fluid.
DISCUSSION With freehand biopsy techniques, multiple trajectories m a y be r e q u i r e d b e f o r e t h e lesion is l o c a t e d , with an
Fig. 6 - Same patient as Fig. 3. The site of biopsy marked by a barium impregnated sphere (arrowed) is seen and its co-ordinates, printed on the scan image, are within one pixel of the pre-operative co-ordinates (L +50, W 100).
212
CLINICAL RADIOLOGY
(a)
(b)
Fig. 7 - (a) CT scan after contrast medium.The site of the previous open craniotomy biopsy (black arrow) and the chosen position for the stereotactic biopsy (open arrow) are indicated (L +15, W75). (b) Post-operative CT scan showing the barium impregnated sphere at the biopsy site with the corresponding co-ordinates (L +9, W 100).
increased risk of causing cerebral haemorrhage and worsening cerebral oedema, which may already be present. Computed tomography-assisted stereotaxis has now become an established technique and is being increasingly used in the primary diagnosis of many types of intracranial lesion (Bo6thius et al., 1978; Ostertag et al., 1980; Perry et al., 1980; Broggi and Franzini, 1981; Koslow et al., 1981; Wester et al., 1981). It is the method of choice in tumours which are either small, deep seated, cystic or unresectable and has also been used in the evacuation of cerebral abscesses and acute, small, central haematomas (James et al., 1979; Moran et al., 1979; Wise and Gteason, 1979; Shelden et al., 1980; Anderson et al., 1983). Several CT stereotactic techniques have been described based on two fundamental methods: those that combine a head fixation device, suitable for scanning, with a conventional neurosurgical stereotactic frame and those where the biopsy is performed with the patient in the CT scanner, with per-operative scans to determine the trajectory and depth of the cannula. Most systems require the use of a wide-aperture scanner, either because the head frame is too bulky to fit into a dedicated head scanner (Brown, 1979a; Patil, 1982; Anderson et al., 1983) or because the stereotactic procedure can only be performed satisfactorily in the extra space afforded by a wide-aperture scanner (Hahn etal., 1979; James etal., 1979; Moran etal., 1979). One of the features of this system, derived from that developed at the Karolinska Hospital, Stockholm for use with EMI Mark 1 scanner and a modifed Leksell frame (Leksell, 1971; Bergstr6m and Greitz, 1976), is that it can be carried out in a narrow-aperture scanner. It could, if desired, be modified for per-operative CT scanning, but the advantages of a reduced procedure time and repeated CT verification of the position of the cannula tip compared with the more conventional operating theatre biopsy technique may be outweighed
by an increased risk of infection (Penn et al., 1978; Brown, 1979a). The reliability of the system has been verified by the constancy of the position of the sphere on the post-biopsy scans. In other techniques the accuracy has been established by experimentation with phantoms, as no marker is inserted at the time of surgery (Brown, 1979b; Patil, 1982). This technique and others simulate the position of the cannula tip prior to biopsy but slight displacement of the cannula could, theoretically, occur in vivo due to resistance of the brain substance. Confirmation of the accuracy of the biopsy site by means of an implanted barium-impregnated sphere was, therefore, preferred to the bubble of air or small haematoma which may indicate the biopsy site (Moran et al., 1979; Anderson et al., 1983) but which may be too small or diffuse to localise it sufficiently accurately. The application of the head fixation device is quick and simple and the position of the head within the scanner is not critical since the co-ordinates are referred to the base ring of the head fixation device. Furthermore, there is no need to correct for magnification, allow for parallax, or take into account rotation of the head, factors which may introduce a significant error in localisation of the position of lesions, especially those situated peripherally (Gleason et al., 1978; Penn et al., 1978; Goerss et al., 1982). Other techniques require the head to be aligned within the CT scanner so that the lesion and the intended site of the burr hole are visualised on the same plane. Preliminary scans with scalp markers are, therefore, required prior to trephine and biopsy (Moran et al., 1979; Wester etal., 1981; Patil, 1982). The four percutaneous screws applied directly to the scalp eliminate the need for twist drill fixation (Bo6thius et al., 1980; Goerss et al., 1982). The new screws, made from aluminium tipped polypropylene, and brackets, made of carbon fibre, are virtually free from artefact
213
S T E R E O T A C T I C B R A I N B I O P S Y U S I N G CT
(a)
(b)
Fig. 8 - (a) Post-biopsy CT scan demonstrating the barium sphere with a small amount of air within the tumour but anterior to the sphere; also in the subdural space (L +50, W 100). (b) Cut brain slice through the tumour showing the position of the sphere in the posterior part of the tumour.
distortion, a problem encountered with the original aluminium design. Neither does the cannula produce artefact distortion which might interfere with the biopsy of small lesions in per-operative scanning techniques (Moran et al., 1979; Penn, 1979). This series of 12 cases is too small to establish the safety of the procedure, but the absence of mortality and morbidity, particularly without the use of steroids, compares favourably, so far, with other series. A mortality rate of 1-2% and morbidity of 2 - 4 % have been reported (Heath et al., 1961; Marshall et al., 1974; Spence et al., 1974; Edner, 1975; Shetter et al., 1977) although, m o r e recently, a lower incidence of complications has been attributed to refinements in technique and the use of steroids in the per-operative period (Gleason et al., 1978; H a h n et al., 1979; James et al., 1979). I m p r o v e m e n t in the patients' neurological status following aspiration of cyst fluid from large necrotic tumours has been reported (James et al., 1979; Moran et al., 1979). In this series of 12 cases, two patients showed clinical i m p r o v e m e n t following stereotactic biopsy and fluid aspiration. The m a j o r disadvantages of the present procedure are the times taken to induce general anaesthesia and to transport the patient between the CT scanner and the operating theatre. Some centres perform stereotactic brain biopsy under sedation but, because of the distance between our CT scanner and operating theatre, it was
not considered appropriate for the procedure to be p e r f o r m e d under local anaesthesia. This system also requires the use of a neurosurgical stereotactic headframe, which is not needed by those methods employing a freehand biopsy technique. Despite these disadvantages, the procedure has proved to be reliable, simple to p e r f o r m and relatively inexpensive, but it does require close co-operation between the radiologist and neurosurgeon.
Acknowledgements. We would like to thank Miss Helen Davies for typing the manuscript, the radiographers for their assistance during the scanning procedure, Mr Henry Lawrence for his help with the computer program and the photographic department for the preparation of the illustrations.
REFERENCES
Anderson, R. E., Thomas, D. G. T. & du Boulay, G. H. (1983). Radiological aspects of CT guided stereotactic neurosurgical procedures. Neuroradiology, 24, 163-166. Bergstr6m, M. & Greitz, T. (1976). Stereotaxic computed tomography. American Journal of Roentgenology, 127, 167-170. Bo6thius, J., Collins, V. P., Edner, G., Lewander, R. & Zajicek, J. (1978). Stereotactic biopsies and computer tomography in gliomas. Acta Neurochirurgica, 40, 223-232. Bo6thius, J., Bergstr6m, M. & Greitz, T. (1980). Stereotaxic computerized tomography with a G.E. 8800 scanner. Journal of Neurosurgery, 52, 794-800.
214
CLINICAL RADIOLOGY
Broggi, G. & Franzini, A. (1981). Value of serial stereotactic biopsies and impedance monitoring in the treatment of deep brain tumours. Journal of Neurology, Neurosurgery and Psychiatry, 44, 39%401. Brown, R. A. (1979a). A stereotactic head frame for use with CT body scanners, investigative Radiology, 14, 300-304. Brown, R. A. (1979b). A computerized tomography-computer graphics approach to stereotaxic localization. Journal of Neurosurgery, 50, 715-720. Chernak, E. S., Rodriguez-Antunez, A., Jelden, G. L., Dhaliwal, R. S. & Lavik, P. S. (1975). The use of computed tomography for radiation therapy treatment planning. Radiology, 117, 613-614. Clarke, R. H. & Horsley, V. (1906). On a method of investigating the deep ganglia and tracta of the central nervous system (cerebellum). British Medical Journal, il, 1799-1800. Edner, G. (1975). Stereotaxic brain tumour biopsy - 5 years experience. Acta Neurochirurgica (Wien), 3, 261. Gleason, C. A., Wise, B. L. & Feinstein, B. (1978). Stereotactic localization (with computerized tomographic scanning), biopsy and radiofrequency treatment of deep brain lesions, Neurosurgery, 2, 217-223. Goerss, S., Kelly, P. J., Kall, B. & Alker, G. J., Jr (1982). A computed tomographic adaptation system. Neurosurgery, 10, 375-379. Greitz, T., Bergstr6m, M., Bo6thius, J., Kingsley, D, & Ribbe, T. (1980). Head fixation system for investigation of radiodiagnostic and therapeutic procedures. Neuroradiology, 19, 1-6. Hahn, J. F., Levy, W. J. & Weinstein, M. J. (1979). Needle biopsy of intracranial lesions guided by computerised tomography. Neurosurgery, 5, 11-15. Heath, R. G., John, S. & Foss, O. (1961). Stereotaxic biopsy. A method for the study of discrete brain regions of animals and man. Archives" of Neurology, 4, 291-300. James, H. E., Wells, M., Alksne, J. F., Wickbom, I., Siemers, P., Brahme, F. & Rosenberg, J. (1979). Needle biopsy under computerized tomographic control: a method for tissue diagnosis in intracranial lesions. Neurosurgery, 5, 671-674. Koslow,M., Abele, M. G., Griffith, R. C., Mair, G. A. & Chase, N. E. (1981). Stereotactic surgical system controlled by computed tomography. Neurosurgery, 8, 72-82. Leksell, L. (1971). Stereotaxis and Radiosurgery. An Operative System. Charles C. Thomas, Springfield, Illinois. Maroon, J. G., Bank, W. O., Drayer, B. P. & Rosenbaum, A. E. (1977). Intracranial biopsy assisted by computerized tomography. Journal of Neurosurgery, 46, 740-744. Marshall, L. F., Jennett, B. & Langfitt, T. W. (1974). Needle biopsy for the diagnosis of malignant glioma. Journal of the American Medical Association, 228, 141%1418.
Moran, C. J., Naidich, T. P., Gado, M. H. & Marchosky, J. A. (1979). Central nervous system lesions biopsied or treated by CT guided needle placement. Radiology, 131, 681-686. Ostertag, C. B., Mennel, H. D. & Kiessling, M. I. (1980). Stereotactic biopsy of brain tumours. Surgical Neurology, 14, 275-283. Patil, A. A. (1982). Computed tomography-orientated stereotacfic system. Neurosurgery, 10, 370-373. Penn, R. D., Whisler, W. W., Smith, C. A. & Yasnoff, W. A. (1978). Stereotactic surgery with image processing of computerised tomographic scan. Neurosurgery, 3, 157-161. Penn, R. D. (1979). 'Comments'. (In response to paper by Hahn et al. (1979).) Neurosurgery, 5, 14-15. Perry, J. H., Rosenbaum, A. E., Lunsford, L. D., Swink, C. A. & Zorab, D. S. (1980). Computed tomography-guided stereotactic surgery: conception and development of a new stereotactic methodology. Neurosurgery, 7, 376--381. Rossolimo, G. I. (1907). 'Brain Topograph'. A device for projection on the cranium of brain convolutions. Magazine of Korsakov, 4, 639. Shetter, A. G., Bertuccini, T. V. & Pittman, H. W. (1977). Closed needle biopsy in the diagnosis of intra-cranial mass lesions. Surgical Neurology, 8, 341-345. Shelden, C. H., McCann, G., Jaques, S., Lutes, H. R., Frazier, R. E., Katz, R. & Kuki, R. (1980). Development of a computerized microstereotaxic method for localization and removal of minute CNS lesions under direct 3-D vision. Journal of Neurosurgery, 52, 21-27. Spence, J. W., Richards, D. E. & Nulsen, F. E. (1974). Indications for brain tumour biopsy by trephine and needle: review of results. Presented at the 42nd Annual Meeting of the American Association of Neurological Surgeons, St Louis, Missouri, 24 April. Spiegel, E. A. & Wycis, H. T. (1952). Stereoencephalotomy. Methods" and Stereotaxic Atlas of Human Brain. Grune and Stratton, New York. Wester, K., Sortland, O. & Hauglie-Hanssen, E. (1981). A simple and inexpensive method for CT-guided stereotaxy. Neuroradiology, 20, 255-256. Wise, B. L. & Gleason, C. A. (1979). CT-directed stereotactic surgery in the management of brain abscesses. Annals of Neurology, 6, 457. Zernov, D. N. (1889). Encephalometer. A device for determination of the location of brain parts of living human. Demonstrated at the Meeting of Society of Physics and Medicine of Moscow University, 22 March.