Encrypted login | home

Program Information

Diffusion MRI for Treatment Response Assessment of MRI-Guided Tri-Cobalt 60 Radiotherapy

no image available
Y Yang

Y Yang1*, D Low1, M Cao1 , K Sheng1 , J Lamb1 , D Thomas1, M Kamrava1 , P Hu2 , (1) Deparment of Radiation Oncology, University of California Los Angeles, Los Angeles, CA, (2) Department of Radiology, University of California, Los Angeles, Los Angeles, CA,


TH-CD-204-6 (Thursday, July 16, 2015) 10:00 AM - 12:00 PM Room: 204

Purpose: To develop a diffusion MRI pulse sequence on the 0.35T MRI in a commercially available MRI-guided tri-Cobalt 60 radiotherapy system (Viewray), and demonstrate the initial utility of this pulse sequence on a patient undergoing radiation therapy.
Methods: The pulse sequence is a diffusion-weighted spin echo (SE) single-shot echo planar imaging (EPI) sequence. The pulse sequence parameters included: flip angle=90°, repetition time (TR) = 1500ms, echo time (TE) = 140ms, EPI factor = 128, b values = 0, 300, 500 s/mm2, 5 averages, and total scan time of 27sec. To assess the apparent diffusion coefficient (ADC) calculation accuracy, a uniform water phantom was scanned using the developed diffusion sequence on the Viewray system and on a 1.5T Siemens system at the same ambient temperature. The diffusion MRI sequence was further tested in a patient with sarcoma at the thigh who underwent a 25-fraction treatment regime. A single 2D slice diffusion images were acquired on the Viewray system immediately after her 20th fraction treatment while she remained on the treatment couch.
Results: In the phantom, the calculated ADC value was 1.94x10-3 s/mm2 based on the Viewray images, which agreed well with the results based on the 1.5T Siemens images (2.03x10-3 s/mm2). The diffusion image acquired on the sarcoma patient had excellent image quality and showed heterogeneous structure within the gross tumor volume (GTV). The ADC was 2.36x10-3 s/mm2 at the bladder and 1.44x10-3 s/mm2 at the tumor.
Conclusion: This is the first in vivo study of a diffusion MRI sequence on a hybrid MRI-Radiotherapy system. We demonstrate the feasibility of diffusion MRI on the hybrid MRI-60Co radiotherapy system with 0.35 Tesla magnet and it may be a powerful tool for assessing the longitudinal changes in tumor ADC, the tumor response to radiotherapy and for adaptive radiotherapy.

Contact Email: