Two-Staged Radiosurgical Treatment of Large Arteriovenous Malformations
Tóm tắt
When the size of an arteriovenous malformation (AVM) in any one direction is more than 4 cm, an attempt is made to treat it in two stages, separated by 6 months. The first stage treats one-half of the AVM and the remainder is treated in the second stage, thus giving rise to a higher prescription dose for each stage. Therefore, the AVM, as a whole, could be given a higher dose than if the entire AVM were treated in a single fraction. In order to reproduce, in each stage, the isocenter coordinates determined from a pair of orthogonal films, two techniques are applied. One is the use of BrainLAB's mask system, which maintains the isocenter accuracy within ± 1 mm between the two stages. The other is the use of four 3-mm long titanium screws (fiducial markers) embedded in the patient's skull. The coordinate transformation matrix established for the fiducial markers between the first- and second-treatment stages can be applied to the respective isocenter coordinates. Thus, the original isocenter can be reestablished in the coordinate system of the second-treatment stage. Application of this method was first tested with four 5-mm diameter aluminum balls (BBs) attached as fiducial markers to the external surface of the Rando head phantom and three 3-mm tungsten balls embedded as isocenters inside the skull. One patient case was also studied in terms of predicted accuracy, since the isocenters cannot be pinpointed in terms of anatomical structure (like the three tungsten balls). The two-staged radiosurgical approach with small screws embedded in the skull maintains the accuracy required for stereotactic radiosurgery, thereby facilitating the treatment of large AVMs. Since rigid fixation of the head, as is used with traditional stereotactic radiosurgery, is not used with this two-staged approach, treatment does not have to be delivered shortly after diagnostic images are acquired for treatment planning. This gives the physicist, radiation oncologist, and neurosurgeon additional time to optimize the treatment plan, if necessary. By dividing the treatment into two stages, it is hoped that a higher dose of radiation can be safely delivered to large AVMs, thereby increasing the likelihood of cure.
Tài liệu tham khảo
Luessenhop AJ, Natural history of cerebral arteriovenous malformations. In Intracranial Arteriovenous Malformations. CB Wilson, BM, Stein (eds). Baltimore: Williams & Wilkins, 1984, pp. 12–23
Heros RC, Tu YK. Is surgical therapy needed for unruptured arteriovenous malformations? Neurology 37:279–286, 1987
Svien HJ, McRae JA. Arteriovenous anomalies of the brain: Fate of patients not having definitive surgery. J Neurosurg 23:23–28, 1965
Stein BM, Kader A. Intracranial arteriovenous malformations. J Neurosurg 39:76–113, 1992
Levy RP, Fabrikant JI. Clinical applications of stereotactic radiosurgery. In Physical Aspects of Stereotactic Radiosurgery. Phillips MH, (ed): New York: Plenum Press, 1993, pp. 239–278
Mizoi K, Kokura H, Yoshimoto T, et al. Multimodality treatment for large and critically located arteriovenous malformations. Neurol Med Chir 38(Suppl):186–192, 1998
Laing RW, Childs J, Brada M. Failure of conventionally fractionated radiotherapy to decrease the risk of hemorrhage in inoperable arteriovenous malformations. Neurosurgery 30:872–876, 1992
Ogilvy CS. Radiation therapy for arteriovenous malformations: A review. Neurosurgery 26:725–735, 1990
Wilder RB. Treatment of arteriovenous malformations with stereotactic radiosurgery. Radiat Oncol Invest 2:57–65, 1994
Kjellberg RN. Stereotactic Bragg peak proton beam radiosurgery for cerebral arteriovenous malformations. Ann Clin Res 47:17–19, 1986
Fabrikant JI, Levy RP, Steinberg GK, et al. Charged-particle radiosurgery for intracranial vascular malformations. Neurosurg Clin North Am 3:99–139, 1992
Miyawaki L, Dowd C, Wara W, et al. Five year results of LINAC radiosurgery for arteriovenous malformations: outcome for large AVMS. Int J Radiat Oncol Biol Phys 44:1089–1106, 1999
Levy RP, Schulte RW, Slater JD, et al. Stereotactic radiosurgery-- the role of charged particles. Acta Oncol 38:165–169, 1999
Kirkeby OJ, Bakke S, Tveraa K, et al. Fractionated stereotactic radiation therapy for intracranial arteriovenous malformations. Stereotact Funct Neurosurg 66:10–14, 1996
Hall EJ, Brenner DJ. The radiobiology of radiosurgery: Rationale for different treatment regimes for AVMs and malignancies. Int J Radiat Oncol Biol Phys 25:381–385, 1993
Smith V, Petti PL, Verhey LJ, McDermott MW, Larson DL. Reestablishment of stereotactic coordinates for staged radiosurgery treatment of large AVMs. Unpublished report, 1977
Green, BF. The orthogonal approximation of an oblique simple structure in factor analysis. Psychometrika 17:429–440, 1952
Cliff, N. Orthogonal rotation to congruence. Psychometrika 31: 33–42, 1966
Schoenemann, PH. A generalized solution of the orthogonal procrustes problem. Psychometrika 31:1–10, 1996
Schoenemann, PH, Carroll, RM. Fitting one matrix to another under choice of a central dilation and a rigid motion. Psychometrika 35:245–255, 1970
Kubo HD, Wilder RB, Pappas CT. Impact of collimator leaf width on stereotactic radiosurgery and 3D conformal radiotherapy treatment plans. Int J Radiat Oncol Biol Phys 44:937–945, 1999