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 cm(3), 0.97 cm(3), 0.98 cm(3), 0.82 cm(3), and 1.13 cm(3). 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 cm(3) (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.