Dosimetric evaluation of bone marrow sparing in proton radiotherapy for cervical cancer guided by MR functional imaging

Abstract

Background To segment the pelvic active bone marrow (PABM) using magnetic resonance (MR) functional imaging and investigate the feasibility and dosimetric characteristics of cervical cancer proton radiotherapy for active bone marrow (ABM) sparing. Methods We collected CT and MR simulation images of 33 patients with cervical cancer retrospectively. The PBM was contoured on the MRI FatFrac images; the PBM was divided into high-active bone marrow (ABM-high) and low-active bone marrow based on the fat content of the PBM. Four radiotherapy plans were created for each patient, which included intensity-modulated photon therapy (IMRT), bone marrow sparing IMRT (IMRT-BMS), intensity-modulated proton therapy (IMPT), and bone marrow sparing IMPT (IMPT-BMS). The dosimetric differences among the four plans were compared. Results The ABM-high volume in the enrolled patients accounted for 45.2% of the total ABM volume. The target coverage was similar among the four radiotherapy plans. IMRT-BMS, IMPT, and IMPT-BMS reduced the Dmean of ABM-high by 16.6%, 14.2%, and 44.5%, respectively, compared to the Dmean of IMRT (p < 0.05). IMPT-BMS had the best protective effect on the bone marrow. Compared to IMRT, the volume of ABM-high receiving an irradiation dose of 5–40 Gy decreased by 10.2%, 36.8%, 58.8%, 67.4%, 64.9%, and 44.5%, respectively (p < 0.001). Conclusions The MR functional imaging technique helped in the grading and segmentation of PABM. MR functional image-guided proton radiotherapy for cervical cancer can achieve optimal BMS.

Feasibility of identifying proliferative active bone marrow with fat fraction MRI and multi-energy CT

“…A voxel with a higher fat fraction indicates that it is composed of less active, fatty marrow, and a voxel with a lower fat fraction indicates that is if composed of more active marrow due to increased perfusion in these areas. Pichardo et al (2011) and MacEwan et al (2014) both validated MR-based water-fat quantification against histological samples and a number of other studies have investigated the use of FFMRI to identify ABM in RT studies (Bolan et al 2013, Liang et al 2013, Qin et al 2022, Sajeevan et al 2022. MR scanners are becoming more prevalent in radiation oncology clinics and could be used to identify adipose regions of the marrow for RT planning purposes.…”