Free-breathing diffusion-weighted single-shot echo-planar MR imaging using parallel imaging (GRAPPA 2) and high b value for the detection of primary rectal adenocarcinoma

Our objective was to determine the diagnostic accuracy of a free-breathing diffusion-weighted single-shot echo-planar magnetic resonance imaging (FBDW-SSEPI) technique with parallel imaging and high diffusion factor value (b = 1000 s/mm(2)) in the detection of primary rectal adenocarcinomas. Thirty-one patients (14M and 17F; mean age 67 years) with histopathologically proven primary rectal adenocarcinomas and 31 patients without rectal malignancies (14M and 17F; mean age 63.6 years) were examined with FBDW-SSEPI (repetition time (TR/echo time (TE) 3900/91 ms, gradient strength 45 mT/m, acquisition time 2 min) at 1.5 T using generalized autocalibrating partially parallel acquisitions (GRAPPA, acceleration factor 2) and a b value of 1000 s/mm(2). Apparent diffusion coefficients (ADCs) of rectal adenocarcinomas and normal rectal wall were measured. FBDW-SSEPI images were evaluated for tumour detection by 2 readers. Sensitivity, specificity, accuracy and Youden score for rectal adenocarcinoma detection were calculated with their 95% confidence intervals (CI) for ADC value measurement and visual image analysis. Rectal adenocarcinomas had significantly lower ADCs (mean 1.036 × 10(−3 )± 0.107 × 10(−3) mm(2)/s; median 1.015 × 10(−3) mm(2)/s; range (0.827–1.239) × 10(−3) mm(2)/s) compared with the rectal wall of control subjects (mean 1.387 × 10(−3 )± 0.106 × 10(−3) mm(2)/s; median 1.385 × 10(−3) mm(2)/s; range (1.176–1.612) × 10(−3) mm(2)/s) (p < 0.0001). Using a threshold value ≤ 1.240 × 10(−3) mm(2)/s, all rectal adenocarcinomas were correctly categorized and 100% sensitivity (31/31; 95% CI 95–100%), 94% specificity (31/33; 95% CI 88–100%), 97% accuracy (60/62; 95% CI 92–100%) and Youden index 0.94 were obtained for the diagnosis of rectal adenocarcinoma. FBDW-SSEPI image analysis allowed depiction of all rectal adenocarcinomas but resulted in 2 false-positive findings, yielding 100% sensitivity (31/31; 95% CI 95–100%), 94% specificity (31/33; 95% CI 88–100%), 97% accuracy (60/62; 95% CI 92–100%) and Youden index 0.94 for the diagnosis of primary rectal adenocarcinoma. We can conclude that FBDW-SSEPI using parallel imaging and high b value may be helpful in the detection of primary rectal adenocarcinomas.