Diffusion tensor imaging of rectal carcinoma: Clinical evaluation and its correlation with histopathological findings.

Objective: This study sought to assess the feasibility of diffusion tensor imaging (DTI) to noninvasively evaluate histological grade and lymph node metastasis in patients with rectal carcinoma (RC).

Methods: Thirty-seven consecutive patients with histologically confirmed RC were examined by 1.5-T MRI. DTI was performed using a single-shot echo-planar imaging sequence with b values of 0 and 1000 s/mm2 and motion-probing gradients in nine noncollinear directions. Fractional anisotropy (FA), axial diffusivity (AD), mean diffusivity (MD), and radial diffusivity (RD) maps were compared with histopathological findings.

Results: The FA values (0.357 ± 0.047) of the RCs were significantly lower than those of the normal rectal wall, muscle, prostate, and uterus (P < 0.001 for all), while the AD, MD, and RD values (1.221 ± 0.131, 0.804 ± 0.075, and 0.667 ± 0.057 × 10-3 mm2/s, respectively) were also significantly lower than their respective normal values (P < 0.001 for all). The FA, AD, MD, and RD values for RC additionally showed significant inverse correlations with histological grades (r = -0.781, r = -0.750, r = -0.718, and r = -0.682, respectively; P < 0.001 for all). Further, the FA (0.430 vs. 0.611), AD (1.246 vs. 1.608 × 10-3 mm2/s), MD (0.776 vs. 1.036 × 10-3 mm2/s), and RD (0.651 vs. 0.824 × 10-3 mm2/s) (P < 0.001 for all) of the metastatic and nonmetastatic lymph nodes were significantly different.

Conclusions: DTI may be clinically useful for the noninvasive evaluation of histological grade and lymph node metastasis in patients with RC.