=Acta Ndurochirurgica
Acta Neurochir (Wien) (1992) 118:159-161
9 Springer-Verlag 1992 Printed in Austria
A New Model for Non-Invasive, Reproducible Fixation of a Stereotaxic Frame Using an Orthodontic Resin Plate Technical Note S. Carini 1, E. Calcagno 2, P. Tortori-Donati 3, and L. Andreussi 1 Department of Neurosurgery, 2 Department of Orthodontics, and 3 Department of Radiology-Neuroradiological Unit, "G. Gaslini" Research Children's Hospital, Genoa, Italy
Summary The authors describe a new method for reproducible, non-invasive fixation of a stereotaxic localizing frame. A localizing system similar to that of Brown-Roberts-Wells for MR can be fixed at the base of the facial skeleton to the upper dental arch by an orthodontic resin plate. Results of trials with CT scan, advantages and disadvantages are discussed. The new fixture could be employed in open surgery and in fractionated radiotherapy.
The fixing or the removal of the orthodontic plate are performed by a manual enlargement of the metallic hooks; this requires only a few seconds. The resin plate, so fixed to the upper teeth, constitutes the support-base of our localizing system. Localizing system. We have constructed a localizing system in plexiglas, cube-shaped, weighing 0.35 kilograms, similar to that for MR of Brown-Roberts-Wells2, 5 or to that of Tood-Wells7, but open posteriorly, so that a normal resting of the occipital region in the supine position is possible, Horizontal and vertical rods of the localizing frame hold a millimeter scale.
Keywords: Localization; instrumentation; sterotaxis.
Procedure and Results Introduction A s t e r e o t a x i c s y s t e m m u s t i d e a l l y fulfill t h e f o l l o w -
A n o r t h o d o n t i c resin p l a t e w a s m a d e specifically f o r a p a t i e n t a f f e c t e d b y a c h i a s m a t i c n e o p l a s m . A f t e r resin
ing r e q u i r e m e n t s : a c c u r a c y , e x a c t r e p r o d u c i b i l i t y , simplicity in use, e c o n o m y o f time. N o n i n v a s i v e n e s s is especially i m p o r t a n t w h e n n o s u r g i c a l i n t e r v e n t i o n is p l a n n e d at t h e t i m e o f t h e e x a m i n a t i o n o r s u b s e q u e n t r e p o s i t i o n i n g is r e q u i r e d f o r f r a c t i o n a t e d r a d i o t h e r a p y . A new simple computerized stereotaxic method, which c a n be o f s o m e h e l p in n e u r o s u r g e r y a n d in r a d i o t h e r a p y , is p r e s e n t e d .
Materials and Methods The new fixation system. Our stereotaxic system can be fixed at the base of the facial skeleton to the upper dental arch by an orthodontic resin plate. An impression of the upper teeth is taken as for a dental prosthesis. An orthodontic resin plate is then made including some metallic hooks and two cylindric bolts in the resin (Fig. 1). After one or two trials the orthodontic plate is ready to be fixed to the patient's teeth. A solid property of the fixture is obtained by the pliable nature of the metallic hooks, which are arranged to fit exactly between two adjacent teeth.
Fig. 1. An orthodontic resin plate fixed to upper teeth constitutes the support-base for the localizing system. Two cylindric bolts are included in the resin. The fixture is reinforced by metallic hooks
160
S. Carini et al.: Non-Invasive, Reproducible Fixation of a Stereotaxic Frame Using an Orthodontic Resin Plate
rl = xli + YlJ + zlk; r2 = x2i + Y2J + zzk; r3 --- x3i q- YaJ + z3k; r = xi + yj + zk Considering the vectors on the same plane: P1 P2 = r2-rl
P1P3 = r3-rl P1 P = r-r1 then P1 P" P1 P2 x P1 P3 = 0 or
(r-r1) 9(r2-rl) x (r3-rl) = 0 By applying rectangular co-ordinates, the last equation is as follows: Fig. 2. The localizing system-which is similar to that for MR of Brown-Roberts-Wells- is firmly connected to the support base. It is open posteriorly to permit a normal resting of the occipital region in the supine position
plate fixation to the patient's teeth, the localizing system was firmly connected to the support-base by means of two screws (Fig. 2). The solid property and comfort of the fixture gave an excellent result: no dislocation of the orthodontic plate was observed and oscillations were rate, the patient did not complain of any discomfort. Localization trials were performed utilizing a plexiglas phantom in which a plaster cast of teeth was included. Repeatability of target localization was verified by subsequent fixing and removal of prosthesis, utilizing 3 and 5 millimeter CT slices. Principles of target localization, utilized from Brown-Roberts-Wells' and Tood-Wells '1' 14 localizing systems, have been recently recounted by Kelly7. We have developed a software transforming the twodimensional co-ordinates deduced by diagnostic CT into three-dimensional ones. Axial CT slices produce seven reference points by crossing the rods of the localizing frame. The twodimensional co-ordinates of each reference point and of the target point are obtained by converting X and Y pixels into millimeters. The programme calculates the three-dimensional co-ordinates on the basis of reference points of three oblique rods 7. These three points (P1, P2, P3) in space establish an equation for the CT slice plane containing the target point (P). The points: Pl (Xl, YI, Zl), P2 (x2, Y2, z2), P3 (x3, Y3, z3) and P (x, y, z) have respectively the following position vectors:
[(x'xl) i + (Y-Yl)J + (z-zl)k]' r(X2-Xl)i -4- (Y2-Yl)J + (z2Zl)k ] x [(x3-xl)i + (Y3-Yl)J + (z3-Zl)k] = 0 Swiftly the programme derives target three-dimensional co-ordinates, which can be reproduced directly on the millimeter scale of the localizing system. Results demonstrated errors of less than 1 millimeter (mean 0.7 mm) in target localization with regard to x and y co-ordinates, while for z vertical co-ordinate we detected differences never over 1.7 millimeters, related to the different thickness of CT slices. An operating frame or a reference system for radiotherapy can finaly be applied to the support-base after of the removal of the localizing system. Discussion
A conventional stereotaxic frame is fixed to the patient's head by means of pins or rods which are screwed into the skull. That insures both the immobility between localizing or operating system and intracranial structures, and the repeatability of the procedure. Conventional sterotaxic procedures are still invasive even for diagnostic scanning and often require general anaesthesia, and are cumbersome in open surgery, and sig, nificantly prolong the time of the procedure. Furthermore they are too expensive for many neurosurgical units. Several non-invasive methods have been reported, which can reproduce the results of the scan on the scalp surface or on the plain skull film4, 6, 9, 10, 11, 13, 15, 16. All these methods have been of undoubted help in determining the site of craniotomy, but only for superficial hemispheric lesions. They are generally insufficient for precise fractionated radiotherapy. Our non-invasive
S. Carini et al.: Non-Invasive, Reproducible Fixation of a Stereotaxic Frame Using an Orthodontic Resin Plate stereotaxic system c a n be fixed at the base o f the facial skeleton to the u p p e r d e n t a l arch, which is easy to a p p r o a c h , a n d constitutes a firm s u p p o r t for localizing a n d o p e r a t i n g systems c o n s t r u c t e d with plexiglas, lexan or light alloys. N o r m a n 12 was the first to utilize a " m o u t h b i t e " to keep the p a t i e n t ' s h e a d s t e a d y in the C T g a n t r y . The use o f a d e n t a l resin p l a t e for r a d i o d i a g n o s t i c a n d therapeutic p r o c e d u r e s has been m a d e p r e v i o u s l y b y G r e i t z 3. Nevertheless the teeth were only a reference p o i n t a n d the resin was n o t r e i n f o r c e d b y metallic h o o k s . F u r t h e r m o r e the o p e r a t i n g system was t o o h e a v y a n d it was the cause o f some loss o f precision 8. O u r m e t h o d o f fixation, which causes little d i s c o m fort to the p a t i e n t a n d is a t r a u m a t i c , is easy to a p p l y a n d to r e m o v e within a s h o r t time. A n exact repeatability o f the p r o c e d u r e w i t h o u t further d i a g n o s t i c C T is possible. The fixture m a y be e m p l o y e d in a n y t y p e o f o p e n surgery a n d in f r a c t i o n a t e d r a d i o t h e r a p y . I n p a e d i a t r i c s the use is p o s s i b l e over the age o f five years. T h e m e t h o d c a n n o t be e m p l o y e d where there is absence o f teeth or where diseases are p r e s e n t w h i c h cause the teeth to be loose (e.g. P a p i l l o n - L e v e b r e disease, juvenile diabetes etc.).
References 1. Brown RA (1979) A computerized tomography-computcr graphics approach to stereotaxic localization. J Neurosurg 50:715 720 2. Brown RA, Roberts TS, Osborn AG (1980) Stereotaxic frame and computer software for CT-directed neurosurgical localization. Invest Radiol 15:308-312 3. Greitz T, Bergstrom M, Boethius J, etal (1980) Head fixation system for integration of radiodiagnostic and therapeutic procedures. Neuroradiology 19:1-6
161
4. Hariz MI, Fodstad H (1987) Stcrcotactic localization of small subcortical brain tumours for open surgery. Surg Neurol 28: 345-350 5. Heilbrun MP, Roberts TS, Apuzzo MLJ, et al (1983 ) Preliminary
experience with Brown-Roberts-Wells (BRW) computerized tomography stereotaxic guidance system. J Neurosurg 59: 2l 7222 6. Hirschberg H (1989) Localization of brain tumours with a simple scalp-mounted fiducial device. J Neurosurg 70:280-281 7. Kelly PJ, Goerss SJ, Kall BA (1988) Evolution of contemporary instrumentation for computer-assisted stereotactic surgery. Surg Neurol 30:204-215 8. Kingsley DPE, Bergstrom M, Berggren B-M (1980) A critical evaluation of two methods of head fixation. Neuroradiology 19: 7-12 9. Krol G, Galicich J, Arbit E, et al (1988) Preoperative localization
of intracranial lesions on MR. AJNR 9:513 516 10. Lee SH, Villafana T (1980) Localization of vertex lesions on cranial computed tomography. Radiology 134:539 540 1I. Moscley JI, Giannotta SL, Renaudin JW (1980) A simple, inexpensive technique for accurate mass localization by computerized tomography. Technical note. J Neurosurg 52:733-735 !2. Norman D, Newton TH (1975) Localization with the EMI scanner. Am J Roentgenol 125:961-964 13. Patil AA, Woosley RE (1986) Scalp marking of intracranial lesions using computed tomography (CT) images. A technical note. Acta Neurochir (Wien) 80:62-64 14. Perry JH, Rosenbaum AE, Lunsford LD, et al (1980) Computed tomography-guided stereotactic surgery: conception and development of a new stereotactic methodology. Neurosurgery 7: 376-381 15. Piskun WS, Stevens EA, Lamorgese JR, et al (1979) A simplified method of CT assisted localization and biopsy of intracranial lesions. Surg Neurol 11:413-417 16. Wester K, Sortland O, Hauglie-Hanssen E (1981) A simple and inexpensive method for CT-guided stereotaxy. Neuroradiology 20:255-256 Correspondence and Reprints: Dr. Santino Carini, Department of Neurosurgery, "G. Gaslini" Research Children's Hospital, L. go G. Gaslini, 5, 1-16148 Genova GE, Italy.
Acta Neurochir (Wien) (1992) 118:159-161
9 Springer-Verlag 1992 Printed in Austria
A New Model for Non-Invasive, Reproducible Fixation of a Stereotaxic Frame Using an Orthodontic Resin Plate Technical Note S. Carini 1, E. Calcagno 2, P. Tortori-Donati 3, and L. Andreussi 1 Department of Neurosurgery, 2 Department of Orthodontics, and 3 Department of Radiology-Neuroradiological Unit, "G. Gaslini" Research Children's Hospital, Genoa, Italy
Summary The authors describe a new method for reproducible, non-invasive fixation of a stereotaxic localizing frame. A localizing system similar to that of Brown-Roberts-Wells for MR can be fixed at the base of the facial skeleton to the upper dental arch by an orthodontic resin plate. Results of trials with CT scan, advantages and disadvantages are discussed. The new fixture could be employed in open surgery and in fractionated radiotherapy.
The fixing or the removal of the orthodontic plate are performed by a manual enlargement of the metallic hooks; this requires only a few seconds. The resin plate, so fixed to the upper teeth, constitutes the support-base of our localizing system. Localizing system. We have constructed a localizing system in plexiglas, cube-shaped, weighing 0.35 kilograms, similar to that for MR of Brown-Roberts-Wells2, 5 or to that of Tood-Wells7, but open posteriorly, so that a normal resting of the occipital region in the supine position is possible, Horizontal and vertical rods of the localizing frame hold a millimeter scale.
Keywords: Localization; instrumentation; sterotaxis.
Procedure and Results Introduction A s t e r e o t a x i c s y s t e m m u s t i d e a l l y fulfill t h e f o l l o w -
A n o r t h o d o n t i c resin p l a t e w a s m a d e specifically f o r a p a t i e n t a f f e c t e d b y a c h i a s m a t i c n e o p l a s m . A f t e r resin
ing r e q u i r e m e n t s : a c c u r a c y , e x a c t r e p r o d u c i b i l i t y , simplicity in use, e c o n o m y o f time. N o n i n v a s i v e n e s s is especially i m p o r t a n t w h e n n o s u r g i c a l i n t e r v e n t i o n is p l a n n e d at t h e t i m e o f t h e e x a m i n a t i o n o r s u b s e q u e n t r e p o s i t i o n i n g is r e q u i r e d f o r f r a c t i o n a t e d r a d i o t h e r a p y . A new simple computerized stereotaxic method, which c a n be o f s o m e h e l p in n e u r o s u r g e r y a n d in r a d i o t h e r a p y , is p r e s e n t e d .
Materials and Methods The new fixation system. Our stereotaxic system can be fixed at the base of the facial skeleton to the upper dental arch by an orthodontic resin plate. An impression of the upper teeth is taken as for a dental prosthesis. An orthodontic resin plate is then made including some metallic hooks and two cylindric bolts in the resin (Fig. 1). After one or two trials the orthodontic plate is ready to be fixed to the patient's teeth. A solid property of the fixture is obtained by the pliable nature of the metallic hooks, which are arranged to fit exactly between two adjacent teeth.
Fig. 1. An orthodontic resin plate fixed to upper teeth constitutes the support-base for the localizing system. Two cylindric bolts are included in the resin. The fixture is reinforced by metallic hooks
160
S. Carini et al.: Non-Invasive, Reproducible Fixation of a Stereotaxic Frame Using an Orthodontic Resin Plate
rl = xli + YlJ + zlk; r2 = x2i + Y2J + zzk; r3 --- x3i q- YaJ + z3k; r = xi + yj + zk Considering the vectors on the same plane: P1 P2 = r2-rl
P1P3 = r3-rl P1 P = r-r1 then P1 P" P1 P2 x P1 P3 = 0 or
(r-r1) 9(r2-rl) x (r3-rl) = 0 By applying rectangular co-ordinates, the last equation is as follows: Fig. 2. The localizing system-which is similar to that for MR of Brown-Roberts-Wells- is firmly connected to the support base. It is open posteriorly to permit a normal resting of the occipital region in the supine position
plate fixation to the patient's teeth, the localizing system was firmly connected to the support-base by means of two screws (Fig. 2). The solid property and comfort of the fixture gave an excellent result: no dislocation of the orthodontic plate was observed and oscillations were rate, the patient did not complain of any discomfort. Localization trials were performed utilizing a plexiglas phantom in which a plaster cast of teeth was included. Repeatability of target localization was verified by subsequent fixing and removal of prosthesis, utilizing 3 and 5 millimeter CT slices. Principles of target localization, utilized from Brown-Roberts-Wells' and Tood-Wells '1' 14 localizing systems, have been recently recounted by Kelly7. We have developed a software transforming the twodimensional co-ordinates deduced by diagnostic CT into three-dimensional ones. Axial CT slices produce seven reference points by crossing the rods of the localizing frame. The twodimensional co-ordinates of each reference point and of the target point are obtained by converting X and Y pixels into millimeters. The programme calculates the three-dimensional co-ordinates on the basis of reference points of three oblique rods 7. These three points (P1, P2, P3) in space establish an equation for the CT slice plane containing the target point (P). The points: Pl (Xl, YI, Zl), P2 (x2, Y2, z2), P3 (x3, Y3, z3) and P (x, y, z) have respectively the following position vectors:
[(x'xl) i + (Y-Yl)J + (z-zl)k]' r(X2-Xl)i -4- (Y2-Yl)J + (z2Zl)k ] x [(x3-xl)i + (Y3-Yl)J + (z3-Zl)k] = 0 Swiftly the programme derives target three-dimensional co-ordinates, which can be reproduced directly on the millimeter scale of the localizing system. Results demonstrated errors of less than 1 millimeter (mean 0.7 mm) in target localization with regard to x and y co-ordinates, while for z vertical co-ordinate we detected differences never over 1.7 millimeters, related to the different thickness of CT slices. An operating frame or a reference system for radiotherapy can finaly be applied to the support-base after of the removal of the localizing system. Discussion
A conventional stereotaxic frame is fixed to the patient's head by means of pins or rods which are screwed into the skull. That insures both the immobility between localizing or operating system and intracranial structures, and the repeatability of the procedure. Conventional sterotaxic procedures are still invasive even for diagnostic scanning and often require general anaesthesia, and are cumbersome in open surgery, and sig, nificantly prolong the time of the procedure. Furthermore they are too expensive for many neurosurgical units. Several non-invasive methods have been reported, which can reproduce the results of the scan on the scalp surface or on the plain skull film4, 6, 9, 10, 11, 13, 15, 16. All these methods have been of undoubted help in determining the site of craniotomy, but only for superficial hemispheric lesions. They are generally insufficient for precise fractionated radiotherapy. Our non-invasive
S. Carini et al.: Non-Invasive, Reproducible Fixation of a Stereotaxic Frame Using an Orthodontic Resin Plate stereotaxic system c a n be fixed at the base o f the facial skeleton to the u p p e r d e n t a l arch, which is easy to a p p r o a c h , a n d constitutes a firm s u p p o r t for localizing a n d o p e r a t i n g systems c o n s t r u c t e d with plexiglas, lexan or light alloys. N o r m a n 12 was the first to utilize a " m o u t h b i t e " to keep the p a t i e n t ' s h e a d s t e a d y in the C T g a n t r y . The use o f a d e n t a l resin p l a t e for r a d i o d i a g n o s t i c a n d therapeutic p r o c e d u r e s has been m a d e p r e v i o u s l y b y G r e i t z 3. Nevertheless the teeth were only a reference p o i n t a n d the resin was n o t r e i n f o r c e d b y metallic h o o k s . F u r t h e r m o r e the o p e r a t i n g system was t o o h e a v y a n d it was the cause o f some loss o f precision 8. O u r m e t h o d o f fixation, which causes little d i s c o m fort to the p a t i e n t a n d is a t r a u m a t i c , is easy to a p p l y a n d to r e m o v e within a s h o r t time. A n exact repeatability o f the p r o c e d u r e w i t h o u t further d i a g n o s t i c C T is possible. The fixture m a y be e m p l o y e d in a n y t y p e o f o p e n surgery a n d in f r a c t i o n a t e d r a d i o t h e r a p y . I n p a e d i a t r i c s the use is p o s s i b l e over the age o f five years. T h e m e t h o d c a n n o t be e m p l o y e d where there is absence o f teeth or where diseases are p r e s e n t w h i c h cause the teeth to be loose (e.g. P a p i l l o n - L e v e b r e disease, juvenile diabetes etc.).
References 1. Brown RA (1979) A computerized tomography-computcr graphics approach to stereotaxic localization. J Neurosurg 50:715 720 2. Brown RA, Roberts TS, Osborn AG (1980) Stereotaxic frame and computer software for CT-directed neurosurgical localization. Invest Radiol 15:308-312 3. Greitz T, Bergstrom M, Boethius J, etal (1980) Head fixation system for integration of radiodiagnostic and therapeutic procedures. Neuroradiology 19:1-6
161
4. Hariz MI, Fodstad H (1987) Stcrcotactic localization of small subcortical brain tumours for open surgery. Surg Neurol 28: 345-350 5. Heilbrun MP, Roberts TS, Apuzzo MLJ, et al (1983 ) Preliminary
experience with Brown-Roberts-Wells (BRW) computerized tomography stereotaxic guidance system. J Neurosurg 59: 2l 7222 6. Hirschberg H (1989) Localization of brain tumours with a simple scalp-mounted fiducial device. J Neurosurg 70:280-281 7. Kelly PJ, Goerss SJ, Kall BA (1988) Evolution of contemporary instrumentation for computer-assisted stereotactic surgery. Surg Neurol 30:204-215 8. Kingsley DPE, Bergstrom M, Berggren B-M (1980) A critical evaluation of two methods of head fixation. Neuroradiology 19: 7-12 9. Krol G, Galicich J, Arbit E, et al (1988) Preoperative localization
of intracranial lesions on MR. AJNR 9:513 516 10. Lee SH, Villafana T (1980) Localization of vertex lesions on cranial computed tomography. Radiology 134:539 540 1I. Moscley JI, Giannotta SL, Renaudin JW (1980) A simple, inexpensive technique for accurate mass localization by computerized tomography. Technical note. J Neurosurg 52:733-735 !2. Norman D, Newton TH (1975) Localization with the EMI scanner. Am J Roentgenol 125:961-964 13. Patil AA, Woosley RE (1986) Scalp marking of intracranial lesions using computed tomography (CT) images. A technical note. Acta Neurochir (Wien) 80:62-64 14. Perry JH, Rosenbaum AE, Lunsford LD, et al (1980) Computed tomography-guided stereotactic surgery: conception and development of a new stereotactic methodology. Neurosurgery 7: 376-381 15. Piskun WS, Stevens EA, Lamorgese JR, et al (1979) A simplified method of CT assisted localization and biopsy of intracranial lesions. Surg Neurol 11:413-417 16. Wester K, Sortland O, Hauglie-Hanssen E (1981) A simple and inexpensive method for CT-guided stereotaxy. Neuroradiology 20:255-256 Correspondence and Reprints: Dr. Santino Carini, Department of Neurosurgery, "G. Gaslini" Research Children's Hospital, L. go G. Gaslini, 5, 1-16148 Genova GE, Italy.
