Optimal Setup and Parameters of Diffusion-Weighted Magnetic Resonance Imaging for Translational Evaluation of a Tumor Progression Model for Soft Tissue Sarcomas

Abstract

PurposeDefining a microscopic tumor infiltration boundary is critical to the success of radiation therapy. Currently, radiation oncologists use margins to geometrically expand the visible tumor for radiation treatment planning in soft tissue sarcomas (STS). Image-based models of tumor progression would be critical to personalize treatment radiation field to the pattern of sarcoma spread. Evaluation of these models is necessary to demonstrate feasibility in the clinical setting. This study presents an imaging protocol for the preclinical evaluation of a tumor progression model in extremity STS. MethodsWe recruited seven healthy volunteers and acquired diffusion-weighted MRI (DW-MRI) images of the thigh on an MRI scanner used for imaging cancer patients in a radiation oncology department. We developed a protocol, which includes positioning the patient, configuring the RF coils, and setting the diffusion-weighted MRI sequence parameters. To find the optimal parameter configuration, the image signal-to-noise ratio (SNR) and the directional variability (DV) of the principal eigenvector of the diffusion tensor were calculated. ResultsThe mean SNR across all trials and 12 thigh muscles was 41 with a range of 12 to 72. The mean DV was 13° and ranged from 11° to 23°. The longest scan time was 22 min 58 s and the shortest 11 min 46 s. For the high-resolution image with a voxel volume of 1.3×1.3×6 mm3 and 38 slices, the optimal parameters were found to be a repetition time of 8000 ms, 12 signal averages, and 6 gradient directions. This configuration resulted in a scan time of 11 min 46 s, an SNR of 34, and a DV of 13°. ConclusionsA DW-MRI scan duration acceptable for imaging cancer patients was achieved with an image quality suitable for reproducible modeling of tumor infiltration. The developed protocol can be used for preclinical evaluation in STS patients.