Diagnostic Accuracy of a MR Protocol Acquired with and without Endorectal Coil for Detection of Prostate Cancer: A Multicenter Study

Abstract

Introduction: The purpose of this study was to compare diagnostic accuracy of a prostate multiparametric magnetic resonance imaging (mpMRI) protocol for detection of prostate cancer between images acquired with and without en-dorectal coil (ERC).

Materials: This study was approved by the regional ethics committee. Between 2014 and 2015, 33 patients (median age 51.3 years; range 42.1-77.3 years) who underwent prostate-MRI at 3T scanners at 2 different institutions, acquired with (mpMRI_ERC) and without (mpMRI_PPA) ERC and who received radical prostatectomy, were included in this retrospective study. Two expert readers (R1, R2) attributed a PI-RADS version 2 score for the most suspect (i. e. index) lesion for mpMRI_PPA and mpMRI_ERC. Sensitivity and positive predictive value for detection of index lesions were assessed using 2 × 2 contingency tables. Differences between groups were tested using the McNemar test. Whole-mount histopathology served as reference standard.

Results: On a quadrant-basis cumulative sensitivity ranged between 0.61-0.67 and 0.76-0.88 for mpMRI_PPA and mpMRI_ERC protocols, respectively (p > 0.05). Cumulative positive predictive value ranged between 0.80-0.81 and 0.89-0.91 for mpMRI_PPA and mpMRI_ERC protocols, respectively. The differences were not statistically significant for R1 (p = 0.267) or R2 (p = 0.508).

Conclusion: Our results suggest that there may be no significant differences for detection of prostate cancer between images acquired with and without an ERC.

Keywords: Diagnostic accuracy; Endorectal coil; Index lesion; Prostate MRI; Prostate cancer.

Fig. 1

A 67-year-old patient (PSA, 30 ng/ml) undergoing mpMRI of the prostate for cancer detection and local staging. T2w (A, C) and ADC maps (B, D) were used side-by-side with histopathology for correlation of every mismatched lesion. Reconstructed whole-mount histopathology (E) reveals a 4 + 4 tumor (approximately 160 mm2) on the left aspect of the peripheral zone, at the level of the midgland (E, green ROI). At one of the two institutions the slices were digitalized and the lesions outlined electronically. T2w images with corresponding ADC maps from the mpMRIERC (A, B) and mpMRIPPA (C, D) sets and a whole-mount histopathology (E) from the midgland are shown. The corresponding PI-RADS reader score was 4 for both readers and for both image sets.

Fig. 2

A 54-year-old patient (PSA, 7.7 ng/ml) undergoing mpMRI of the prostate for detection and local staging. On the mpMRI_ERC image set, the tumor (arrow) is clearly appreciated on the posterior median aspect of the apex, showing focal T2w hypointensity (A) and corresponding diffusion restriction on the ADC-map (B). On the mpMRI_PPA image set however, the tumor is less evident on T2w series (C) and does show no clearly appreciable diffusion restriction on the ADC map (D). Both readers only identified the tumor using the mpMRI_ERC image set (A, B).

Fig. 3

A 56-year-old patient undergoing mpMRI of the prostate for local staging of a bioptically diagnosed 4 + 3 tumor on the right side of the gland. On the mpMRI_ERC image set, the tumor (arrow) is clearly appreciated on the postero-lateral aspect of the right midgland, showing focal T2w hypointensity (A) and corresponding diffusion restriction on the ADC-map (B). The same is true for the mpMRI_PPA image set (C, D). Both readers correctly identified the tumor using both image sets. Reconstructed whole-mount histopathology (E) reveals a 4 + 3 tumor (approximately 25 mm²) on the postero-lateral aspect of the peripheral zone, at the level of the right midgland (E, green ROI). Both readers correctly identified the tumor by attributing a PI-RADS score of 4 to the corresponding quadrant, using the mpMRI_ERC and the mpMRI_PPA image set.