MO‐F‐CAMPUS‐I‐05: Quantitative ADC Measurement of Esophageal Cancer Before and After Chemoradiation

Purpose: We investigated whether quantitative diffusion imaging can be used as an imaging biomarker for early prediction of treatment response of esophageal cancer. Methods: Eight patients with esophageal cancer underwent a baseline and an interim MRI studies during chemoradiation on a 3T whole body MRI scanner with an 8‐channel torso phased array coil. Each MRI study contained two axial diffusion‐weighted imaging (DWI) series with a conventional DWI sequence and a reduced field‐of‐view DWI sequence (FOCUS) of varying b‐values. ADC maps with two b‐values were computed from conventional DWI images using a mono‐exponential model. For each of DWI sequences, separate ADCall was computed by fitting the signal intensity of images with all the b‐values to a single exponential model. For the FOCUS sequence, a bi‐exponential model was used to extract perfusion and diffusion coefficients (ADCperf and ADCdiff) and their contributions to the signal decay. A board‐certified radiologist contoured the tumor region and mean ADC values and standard deviations of tumor and muscle ROIs were recorded from different ADC maps. Results: Our results showed that (1) the magnitude of ADCs from the same ROIs by the different analysis methods can be substantially different. (2) For a given method, the change between the baseline and interim muscle ADCs was relatively small (≤10%). In contrast, the change between the baseline and interim tumor ADCs was substantially larger, with the change in ADCdiff by FOCUS DWI showing the largest percentage change of 73.2%. (3) The range of the relative change of a specific parameter for different patients was also different. Conclusion: Presently, we do not have the final pathological confirmation of the treatment response for all the patients. However, for a few patients whose surgical specimen is available, the quantitative ADC changes have been found to be useful as a potential predictor for treatment response.