Diffusion-weighted Single Shot Echo Planar Imaging of Colorectal Cancer Using a Sensitivity-encoding Technique

Abstract

Background: We wanted to determine the feasibility of diffusion-weighted single shot echo planar imaging using a sensitivity-encoding technique (SENSE-DWI) in depicting colorectal cancer. Methods: Forty-two patients with sigmoid colon cancer and rectal cancer, all proven pathologically, were examined on T2-turbo spin echo (TSE) and SENSE-DWI. No bowel preparation was performed before examination. The b-factors used in SENSE-DWI were zero and 1000 s/mm². In 10 randomly selected cases, the images whose b-factors were 250 and 500 s/mm² were also obtained. The reduction factor of SENSE was 2.0 in all sequences. Two radiologists evaluated the obtained images from the viewpoints of tumor detectability, image distortion and misregistration of the tumors. The apparent diffusion coefficients (ADCs) of the tumors and urine in the urinary bladders in each patient were measured to evaluate the correlation between ADC and pathological classification of each tumor. Results: All tumors were depicted hyperintensely on SENSE-DWI. Even though single shot echo planar imaging (EPI) was used, the image distortion and misregistration was quite pronounced because of simultaneous use of SENSE. On SENSE-DWI whose b-factor was 1000 s/mm², the normal colon wall and feces were always hypointense and easily differentiated from the tumors. The mean ADC value of each tumor was 1.02 ± 0.1 (×10⁻³) mm²/s. No overt correlation can be pointed out between ADC and pathological classification of each tumor. Conclusion: SENSE-DWI is a feasible method for depicting colorectal cancer. SENSE-DWI provides strong contrast among colorectal cancers, normal rectal wall and feces.