Study of dose distribution with the gamma knife using indices for patients suffering from vestibular schwannomas

Abstract

Author(s): Mohsen Hamoud Jasim*, Siham Sabah Abdullah and Moneer Khammas Faraj

Background: By dividing the tumour into spheres for the purpose of this study, we are investigating whether or not there is a correlation between the degree of sphericity of a target volume and the dose distribution. This relationship is assessed using the selectivity, gradient index, and Isodose Volume to Target Volume (IV/TV) ratios, as well as metrics covering coverage, selectivity, and targetvolume.

While planning radiosurgery for vestibular schwannoma, it is important to consider both the conformity index and the mean dose. Purpose: Covering all the tumour with radiation and reducing the effect of radiation on normal tissue and evaluation indices include selectivity, gradient index (GI), and Paddick Conformity Index (PCI). Methods: A cross-sectional study, The sphericity degree (φ) was determined for each Target Volume (TV) of the fifty patients who had Stereotactic Radiosurgery (SRS) performed on them in order to treat vestibular schwannoma, Calculating this parameter required developing a theoretical concept for operational sphericity, which was done and following are some of the measurements that are used in the analysis of the values that were found: Coverage (C), Selectivity (S), Gradient Index (GI), Paddick Conformity Index (CI Paddick), and Dose Distribution(IV/TV).

Results: The patients included in this study, the mean age of patients was 44.54 ± 11.93 years ranging from (20–80) years and the prevalence of females in this study is 35 (70%) more than the males 15 (30 %). The prescribed dose for vestibular schwannoma patients was 12 Gy. The mean target volume is 5.367 ± 0.058 cm³, ranging from (0.079 – 26.497) cm³.

Conclusion: According to the findings o f t his study, t he t umour c an be separated into spheres; the first sphere o utlines t he r egular p art o f the tumour, while the second sphere outlines the irregular cancer components. For analyzing the dose distribution of a plan for the treatment of vestibular schwannoma, the degree of sphericity is an ideal parameter to employ because the reference plan is a spherical target, and with a Leksell Gamma Knife® Icon (LGKI).

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