Shaverdian Narek, Yang Yingli, Hu Peng, Hart Steven, Sheng Ke, Lamb James, Cao Minsong, Agazaryan Nzhde, Thomas David, Steinberg Michael, Low Daniel A, Lee Percy
1 Department of Radiation Oncology, University of California, Los Angeles, CA, USA.
2 Department of Radiological Sciences, University of California, Los Angeles, CA, USA.
Br J Radiol. 2017 Mar;90(1071):20160739. doi: 10.1259/bjr.20160739. Epub 2017 Jan 12.
To evaluate the feasibility of on-board diffusion-weighted imaging (DWI) with an integrated low-field MRI radiotherapy system to assess responses to neoadjuvant chemoradiation (NAC) in rectal cancer.
A spin echo-based planar imaging diffusion sequence on a 0.35-T MRI radiotherapy system was acquired over the course of NAC. The apparent diffusion coefficients (ADCs) from the tumour regions of interest (ROIs) were calculated. A functional diffusion map (fDM) was created showing a pixelwise ADC analysis of the ROI over the course of treatment. Surgical pathology was correlated with ADC data.
Consecutive patients treated on a 0.35-T MRI radiotherapy system were evaluated. Patient A had the worst pathological response to NAC with a tumour regression score of 1 and was the only patient with a negative slope in the change of ADC values over the entire course of NAC, and during both the first and second half of NAC. The fDM from the first half of NAC for Patient A showed discrete dark areas in the tumour ROI, reflecting subregions with decreasing ADC values during NAC. Patient C had the most favourable pathological response to NAC with a Grade 3 response and was the only patient who had an increase in the slope in the change of ADC values from the first to the second half of NAC.
DWI using a low-field MRI radiotherapy system for evaluating the responses to NAC is feasible. Advances in knowledge: ADC values obtained using a 0.35-T MRI radiotherapy system over the course of NAC for rectal cancer correlate with pathological responses.
评估集成式低场MRI放射治疗系统进行机载扩散加权成像（DWI）以评估直肠癌新辅助放化疗（NAC）反应的可行性。
在NAC过程中，在0.35-T MRI放射治疗系统上采集基于自旋回波的平面成像扩散序列。计算感兴趣肿瘤区域（ROI）的表观扩散系数（ADC）。创建功能扩散图（fDM），显示治疗过程中ROI的逐像素ADC分析。将手术病理与ADC数据相关联。
对在0.35-T MRI放射治疗系统上接受治疗的连续患者进行评估。患者A对NAC的病理反应最差，肿瘤退缩评分为1，是整个NAC过程中以及NAC的前半程和后半程中ADC值变化唯一呈负斜率的患者。患者A在NAC前半程的fDM显示肿瘤ROI中有离散的暗区，反映了NAC期间ADC值降低的子区域。患者C对NAC的病理反应最有利，为3级反应，是唯一一位从NAC前半程到后半程ADC值变化斜率增加的患者。
使用低场MRI放射治疗系统进行DWI评估NAC反应是可行的。知识进展：在直肠癌NAC过程中使用0.35-T MRI放射治疗系统获得的ADC值与病理反应相关。
