ESTRO 2024 - Abstract Book

S3866

Physics - Image acquisition and processing

ESTRO 2024

healthy brain across all fractions. The resulting value was the threshold for significant intensity change between two images.

The proposed method was tested for feasibility using daily positioning TrueFISP scans of 6 glioblastoma patients treated on a 0.35T MR-Linac (ViewRay, Denver, CO, USA). Informed consent or general consent was given by all patients. Three patients (subjects 1 to 3) were treated in 15 fractions of 2.67 Gy, the others (subjects 4 to 6) in 30 fractions of 2 Gy. All patients were imaged using a TrueFISP sequence during the treatment simulation, which served as the baseline, and then at each fraction. The voxel size was 1.5x1.5x1.5 mm^3. All patients had previously undergone a resection, however for patient 6 the largest lesion was not resected. Brain, GTV and CTV were delineated on the simulation images.

For each patient and each time point, we calculated the proportion of voxels showing a significant intensity change compared to the image at fraction 1 for the GTV, the CTV excluding the GTV and the brain excluding the CTV.

Results: