Magnetic Resonance Of Rectal Cancer Response To Therapy: An Image Quality Comparison Between 3.0 And 1.5 Tesla

Purpose. To evaluate signal intensity (SI) differences between 3.0 T and 1.5 T on T2-weighted (T2w), diffusion-weighted imaging (DWI), and apparent diffusion coefficient (ADC) in rectal cancer pre-, during, and postneoadjuvant chemoradiotherapy (CRT). Materials and Methods. 22 patients with locally advanced rectal cancer were prospectively enrolled. All patients underwent T2w, DWI, and ADC pre-, during, and post-CRT on both 3.0 T MRI and 1.5 T MRI. A radiologist drew regions of interest (ROIs) of the tumor and obturator internus muscle on the selected slice to evaluate SI and relative SI (rSI). Additionally, a subanalysis evaluating the SI before and after-CRT ( increment SI pre-post) in complete responder patients (CR) and nonresponder patients (NR) on T2w, DWI, and ADC was performed. Results. Significant differences were observed for T2w and DWI on 3.0 T MRI compared to 1.5 T MRI pre-, during, and post-CRT (all P0.001), whereas no significant differences were reported for ADC among all controls (all P0.05). rSI showed no significant differences in all the examinations for all sequences (all P0.05). increment SI showed significant differences between 3.0 T and 1.5 T MRI for DWI- increment SI in CR and NR (188.39 +/- 166.90 vs. 30.45 +/- 21.73 and 169.70 +/- 121.87 vs. 22.00 +/- 31.29, respectively, all P 0.02) and ADC- increment SI for CR (-0.58 +/- 0.27 vs. -0.21 +/- 0.24P value 0.02), while no significant differences were observed for ADC- increment SI in NR and both CR and NR for T2w- increment SI. Conclusion. T2w-SI and DWI-SI showed significant differences for 3.0 T compared to 1.5 T in all three controls, while ADCSI showed no significant differences in all three controls on both field strengths. rSI was comparable for 3.0 T and 1.5 T MRI in rectal cancer patients; therefore, rectal cancer patients can be assessed both at 3.0 T MRI and 1.5 T MRI. However, a significant DWI- increment SI and ADC- increment SI on 3.0 T in CR might be interpreted as a better visual assessment in discriminating response to therapy compared to 1.5 T. Further investigations should be performed to confirm future possible clinical application.