Shortening multiparametric prostate MRI protocols

The use of a single three-dimensional (3D) T2-weighted image of the prostate could significantly shorten the duration of a multiparametric prostate magnetic resonance imaging (MRI) examinations according to a study published in the April issue of European Radiology. Austrian researchers at the Medical University of Vienna determined that 3D T2-weighted image acquisitions showed equivalent image quality and lesion delineations compared with two-dimensional (2D) acquisitions.

The finding of this small study is significant because multiparametric MRI of the prostate is increasingly being used for the diagnosis of prostate cancer. Several studies have shown it enables both detection and risk stratification with respect to the biological aggressiveness of prostate cancer. However, the time required to perform this procedure and its cost deter more widespread use.

A multi-specialty team of radiologists, urologists, and pathologists conducted a prospective study of 150 consecutive patients who underwent a multiparametric MRI of the prostate due to elevated PSA level, a suspicious digital rectal examination, and/or local staging of diagnosed prostate cancer between November 2015 and February 2017. Their objective was to determine whether 3D t2-weighted image acquisitions achieved similar image quality, lesion delineation quality, and Prostate Imaging Reporting and Data System (PI-RADS) performance compared to standard 2D acquisitions in prostate MRI at 3T, without an endorectal coil. The authors had hypothesized that “a method to considerably shorten the imaging protocol without losing a diagnostic parameter would be to exchange several multiplanar 2D acquisitions of T2-weighted images by a single isotropic 3D acquisition that can be used for subsequent multiplanar reconstructions”.

PI-RADS v2 guidelines were followed for the imaging protocol. This included T2W images, diffusion weighted imaging (DWI), and dynamic contrast enhancement (DCE). The average image acquisition times were 11:14 minutes for 2D T2W, 2:29 minutes for DWI, and 5:02 minutes for DCE. The images were anonymized, then assessed for image quality and interpreted independently by two radiologists.

The radiologists both determined that image quality was comparable for both the 2D T2w and 3D T2w images. They both identified 67 lesions, 53 of which were further evaluated (40 cancerous and 13 benign). The diagnostic accuracy was not statistically different between the two acquisition methods.

Prostate MRI protocols routinely include a 2D T2-weighted sequence in three orthogonal planes and comprise more than one third of the overall protocol used by the Medical University of Vienna’s imaging department.  The acquisition for the sequence took more than 11 minutes, compared to approximately 4 minutes for the 3D acquisition, currently considered to be an adjunct to 2D image acquisition. The authors state that based on the estimated scanning time, two more patients could have a multiparametric MRI of the prostate per hour if a 3D t2w+DWI+DCE protocol was adopted.

The authors state that a larger comparative study of both 2D and 3D acquisitions needs to be undertaken with respect to image quality and diagnostic information before being clinically implemented.  They emphasized the need for “the rapid adoption of a standardized and as-short-as possible protocol to provide a multiparametric MRI imaging service to all men who might profit from it.”

REFERENCE

1. Polanec SH, Lazar M, Wengert GJ, et al. 3D T2-weighted imaging to shorten multiparametric prostate MRI protocols. Eur Radiol. 2018 28;4:1634-1641.