Comparison of reduced field-of-view diffusion-weighted imaging (DWI) and conventional DWI techniques in the assessment of rectal carcinoma at 3.0T: Image quality and histological T staging.

Abstract

To compare image quality (IQ) of reduced field-of-view (rFOV) and full FOV (fFOV) diffusion-weighted imaging (DWI) sequences at 3T, with histological T staging of rectal cancer as a reference standard. In all, 81 patients with rectal cancer received magnetic resonance (MR) scans (3.0T), including both rFOV and fFOV DWI sequences. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were quantitatively evaluated using the paired t-test. Two radiologists independently assessed subjective IQ parameters, including image sharpness, distortion, artifacts, lesion conspicuity, and overall subjective IQ of both sequences. The Wilcoxon signed rank test was used to compare subjective IQ scores and tumor apparent diffusion coefficients (ADCs) between DWI sequences. Spearman correlation analysis was used to correlate ADC values and corresponding T staging of rectal cancer. CNR was significantly higher in rFOV DWI than in fFOV DWI (7.15 ± 2.77 vs. 5.39 ± 2.08, P < 0.001). SNR was significantly higher in rFOV DWI than in fFOV DWI (44.17 ± 11.01 vs. 34.76 ± 13.30, P < 0.001). The subjective IQ parameters of rFOV DWI sequence were rated superior to those of fFOV DWI sequence by both readers (P < 0.001). No significant differences between mean tumor ADC values of both sequences (0.991 ± 0.121 vs. 0.100 ± 0.126 × 10-3 mm2 /s, P = 0.617) were noted. Apart from T1 stage, T staging of rectal cancer was inversely correlated with ADC values of rFOV DWI (r = -0.688, P < 0.001) and fFOV DWI sequences (r = -0.641, P < 0.001). The rFOV DWI sequence provided significantly better IQ and lesion conspicuity than the fFOV DWI sequence. In addition, rFOV and fFOV DWI sequences can be used in evaluation of histological T staging of rectal cancer. 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:967-975.