A Comparative Study of Multiparametric MRI Sequences in Measuring Prostate Cancer Index Lesion Volume.

Objectives: To compare the effectiveness of individual multiparametric prostate MRI (mpMRI) sequences-T2W, diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC), and dynamic contrast-enhanced (DCE)-in assessing prostate cancer (PCa) index lesion volume using whole-mount pathology as the ground-truth; to assess the impact of an endorectal coil (ERC) on the measurements.

Materials and methods: We retrospectively enrolled 72 PCa patients who underwent 3T mpMRI with (n = 39) or without (n = 33) an ERC. A pathologist drew the index lesion borders on whole-mount pathology using planimetry (whole-mount_vol). A radiologist drew the borders of the index lesion on each mpMRI sequence-T2W_vol, DWI_vol, ADC_vol, and DCE_vol. Additionally, we calculated the maximum index lesion volume for each patient (maxMRI_vol). The correlation and differences between mpMRI and whole-mount pathology in measuring the index lesion volume and the impact of an ERC were investigated.

Results: The median T2W_vol, DWI_vol, ADC_vol, DCE_vol, and maxMRI_vol were 0.68 cm³, 0.97 cm³, 0.98 cm³, 0.82 cm³, and 1.13 cm³. There were good positive correlations between whole-mount_vol and mpMRI sequences. However, all mpMRI-derived volumes underestimated the median whole-mount_vol volume of 1.97 cm³ (P ≤ 0.001), with T2W_vol having the largest volumetric underestimation while DWI_vol and ADC_vol having the smallest. The mean relative index lesion volume underestimations of maxMRI_vol were 39.16% ± 32.58% and 7.65% ± 51.91% with and without an ERC (P = 0.002).

Conclusion: T2W_vol, DWI_vol, ADC_vol, DCE_vol, and maxMRI_vol substantially underestimate PCa index lesion volume compared with whole-mount pathology, with T2W_vol having the largest volume underestimation. Additionally, using an ERC exacerbates the volume underestimation.