End-to-end test for brain single and fractionated stereotactic radiotherapy using the LUCY 3D phantom

Stereotactic Radiosurgery is nowadays the main radiotherapy treatment used for small-sized diseases located within the brain. Given the highest complexity related to this technique, periodic tests are mandatory to ensure an efficient workflow is correctly implemented. Our study aims to perform an end-to-end quality assurance test for brain stereotactic radiosurgery using the Lucy 3D QA phantom. CT-images of Lucy phantom were acquired following the same H&N CT-protocol simulating real real-world scenario, with a plugged Pinpoint 3D ionization chamber. A dose distribution was calculated on DICOM images and taken as the gold standard for subsequent comparison with the measured dose under the VersaHD LINAC. 10 patients, noted P1 to P10, were selected and classified as two cohorts based on the prescribed dose (i.e., 5 patients with 20 Gy, and 5 patients with 27 Gy prescribed dose) and one lesion with a maximum diameter less than 5cm. Errors ranged from -5.49% for the P10 to 3.55% for P8, which were both with 27Gy as prescribed dose. Maximum and minimum doses within the ionization chamber’s active volume range from 15.249 Gy for P4 and 21.171 Gy for P6 to 23.418 Gy for P3 and 32.282 Gy for P8, for patients with 20 Gy and 27 Gy prescribed dose, respectively. The difference Max-min ranges from 4.3 Gy for P10 to 12.052 Gy for P4. Our findings show that all of the selected plans respect the adopted tolerance, with small errors that could be caused by the user or material performance, which add additional errors to the final analyzed result.