Room: ePoster Forums
Purpose: Craniospinal irradiation (CSI) is an integral in the treatment paradigm of medulloblastomas MBs. The conventional technique for irradiation of CSI consists of two opposed lateral brain fields matched to one or two PA or AP/PA spine fields. However, field edge matching in conventional CSI is technically very challenging because it requires precise patient setup. We have developed a simple IMRT technique for CSI and compared dose homogeneity, and normal organ sparing and total treatment time with conventional 3D-CRT technique.
Methods: The IMRT plan used three field sets, each with their unique isocenter. One field set with two left-right (LR) lateral fields treated the cranium. Two field sets treated the spine, each set using one posterioanterior (PA) field, one left posterior oblique, and one right posterior oblique beams. Adjacent fields were intentionally overlapped, allowing the optimization process smoothly integrate the dose inside the overlapped junction. Later, another plan using conventional 3D-CRT field matching method was prepared for comparison.
Results: Comparing the IMRT plan with the 3D-CRT plan, the average simplified homogeneity index was 1.27 and 1.44 respectively. Overall, we observed significantly more homogeneous dose distributions around field junctions with IMRT plan compared to 3D field matching technique. Moreover, dose to normal structures was significantly lower with IMRT plan compared to 3D-CRT plan.
Conclusion: We have developed a simplified three isocenter IMRT approach for CSI. The dose homogeneity to the brain and spine is significantly improved, compared to the conventional 3D-CRT. This alternative technique simplifies the set up and eliminates the need for shifting junctions during course of CSI treatment and saves valuable time for patients with MBs.