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- Title
Investigation of the optimal prescription isodose for stereotactic radiosurgery.
- Authors
Gevaert, T.; Levivier, M.; Engels, B.; Tuleasca, C.; Verellen, D.; De Ridder, M.
- Abstract
Objectives: Stereotactic radiosurgery is a well-established treatment technique for intracranial benign and malignant lesions. However, a controversy remains about the best prescription isodose to use for treatment. The Gamma Knife approach generally uses the 50% prescription isodose while the Linac-based approach proposes higher isodose, usually the 80% isodose. A treatment plan is considered acceptable when a Paddick conformity index close to 1 is achieved, while the gradient index is kept below 3. The aim of this study was to investigate if the prescription isodose can be adjusted to achieve a better conformity and gradient. Methods: We enrolled 40 patients with vestibular schwannoma (Koos I-III) treated with Gamma Knife Perfexion (Elekta AB, Sweden) and replanned them with different prescription isodoses, both on Gamma Knife Perfexion system and a dedicated Linac-based system, the Novalis (Brainlab AG, Germany). The ideal prescription isodose for each case and treatment machine were analyzed with the use of the Paddick conformity index and gradient index. Prescription isodoses between 30 % and 80 % were explored. Preliminary Results: The original Gamma Knife Perfexion patient plans achieved a conformity index of 0.77 (SD 0.04) with a gradient index of 2.59 (SD 0.10) at the 50% prescription isodose line. For the Novalis system, a mean value of 67% prescription isodose, not 80 % as might be anticipated for Linac-based systems, was calculated to be relevant for a good conformity and gradient outside the target, reflected by a mean conformity index of 0.68 (SD 0.05) and a gradient index of 3.1 (SD 0.4) were found. Gamma Knife Perfexion treatment plans with different prescription isodoses will further be investigated. Conclusion: In a retrospective series of 40 dose plans for the treatment of vestibular schwannoma, the optimal prescription isodose was assessed. For Linac-based systems, the adaptation of the prescription isodose for each patient will lead to more optimal treatment plans with regard to conformity and dose fall-off Disclosure: No significant relationships.
- Subjects
ACOUSTIC neuroma; STEREOTACTIC radiosurgery; ISODOSE curves; RADIATION dosimetry
- Publication
Journal of Radiosurgery & SBRT, 2013, Vol 2, p147
- ISSN
2156-4639
- Publication type
Article