Three-Dimensional Dosimetry by Optical-CT and Radiochromic Gel Dosimeter of a Multiple Isocenter Craniospinal Radiation Therapy Procedure.

Craniospinal irradiation (CSI) is a complex radiation technique employed to treat patients with primitive neuroectodermal tumors such as medulloblastoma or germinative brain tumors with the risk of leptomeningeal spread. In adults, this technique poses a technically challenging planning process because of the complex shape and length of the target volume. Thus, it requires multiple fields and different isocenters to guarantee the primary-tumor dose delivery.

Evaluation of a composite Gel-Alanine phantom on an end-to-end test to treat multiple brain metastases by a single isocenter VMAT technique.

Purpose: This work aims to evaluate the application of a cylindrical phantom made of dosimetric gel containing alanine pellets distributed inside the gel volume during an end-to-end test of a single isocenter VMAT for simultaneous treatment of multiple brain metastases. The evaluation is based on the comparison of the results obtained with the composite phantom with the treatment planning system (TPS) dose distribution validated by using the clinical conventional quality control with point and planar dose measurements.

Methods: A cylindrical MAGIC-f gel phantom containing alanine dosimeters (composite phantom) was used to design the VMAT plan in the treatment planning system (TPS).