American College of Radiology initiatives on prostate magnetic resonance imaging quality

Abstract

Magnetic resonance imaging (MRI) has become integral to diagnosing and managing patients with suspected or confirmed prostate cancer. However, the benefits of utilizing MRI can be hindered by quality issues during imaging acquisition, interpretation, and reporting. As the utilization of prostate MRI continues to increase in clinical practice, the variability in MRI quality and how it can negatively impact patient care have become apparent. The American College of Radiology (ACR) has recognized this challenge and developed several initiatives to address the issue of inconsistent MRI quality and ensure that imaging centers deliver high-quality patient care. These initiatives include the Prostate Imaging Reporting and Data System (PI-RADS), developed in collaboration with an international panel of experts and members of the European Society of Urogenital Radiology (ESUR), the Prostate MR Image Quality Improvement Collaborative, which is part of the ACR Learning Network, the ACR Prostate Cancer MRI Center Designation, and the ACR Appropriateness Criteria. In this article, we will discuss the importance of these initiatives in establishing quality assurance and quality control programs for prostate MRI and how they can improve patient outcomes.

Fig 1.

66-year-old man with elevated PSA (10 ng/mL) on active surveillance for a Grade Group 1 prostate cancer found on a prior systematic biopsy. A-D: PI-RADS-compliant multiparametric prostate MRI exam with adequate resolution and SNR, with no artifacts affecting the interpretation of the images (PI-QUAL score 5). Axial T2-W image show a 1.8 cm focal lesion with low signal intensity on the left posterolateral peripheral zone at the mid gland and apex with a broad capsular contact (arrow, a). The lesion demonstrates markedly hyperintense signal on high b-value (1,400 sec/mm²) DWI (arrow, b), markedly hypointense signal on ADC map (arrow, c), and early arterial enhancement on T1-weighted DCE images (arrow, d)*. The PI-RADS assessment category of the lesion is 5. MRI-guided biopsy of the lesion revealed prostate cancer Grade Group 2. This case illustrates how high-quality prostate MRI and MRI-guided biopsy can be helpful for the detection of clinically significant prostate cancer. * PI-RADS guidelines recommend T1-weighted DCE images with fat suppression and/or subtractions. The subtraction images performed in this case are not shown. PSA: prostate-specific antigen; PI-RADS: prostate image reporting and data system; SNR: signal-to-noise ratio; T2-W: T2-weighted; DWI: diffusion-weighted imaging; ADC: apparent diffusion coefficient; DCE: dynamic contrast-enhanced. PI-QUAL: prostate imaging quality.

Figure 2.

Primer for using PI-RADS v2.1 for Prostate MRI. The primer contains six modules that can be done nonlinearly and a page with links to additional educational resources. At the end of each module, a short quiz highlights important teaching points. The module is freely available on the ACR website, and no membership is required.

Figure 3.

A. Facade of the ACR Education Center in Reston, VA. B. In the classroom, participants have individual workstations equipped with diagnostic grade monitors and access to the ACR case engine containing over 150 full prostate MRI datasets with radiology-pathology correlation. The ACR designates this live activity for a maximum of 20.5 American Medical Association Physician Recognition Award (AMA PRA) Category 1 Credits.

Figure 4.

A3 Template used by the ACR Learning Network Prostate MR Image Quality Improvement Collaborative. Adapted from Larson DB, Mickelsen LJ, Garcia K. Realizing Improvement through Team Empowerment (RITE): A Team-based, Project-based Multidisciplinary Improvement Program. Radiographics. 2016 Nov-Dec;36(7):2170–2183.

Figure 5.

A 71-year-old man with an elevated PSA of 7.29 ng/mL and no prior prostate biopsy. A. Axial T2-W image obtained in compliance with PI-RADS technical standards shows poor SNR and blurring artifact from rectal peristalsis resulting in a poor delineation of the prostate capsule and of the zonal anatomy. B-C: Axial high b value (1,500 sec/mm²) DWI and ADC map show susceptibility artifacts from rectal gas, distorting the signal on the prostate. D: T1-weighted DCE image obtained with a temporal resolution of 30 sec, which exceeds the 15-sec upper threshold recommended in PI-RADS. It was possible to identify a focal lesion with markedly restricted diffusion in the anterior transition zone, but it was not possible to rule in and rule out focal lesions in other regions of the prostate on DWI. Furthermore, adequate characterization of the focal lesion was not possible on T2-W images and DCE. Because none of the sequences had sufficient diagnostic quality, the overall PI-QUAL score of this exam is 1, and a PI-RADS score should not be assigned for the focal lesion identified in this setting. PSA: prostate-specific antigen; T2-W: T2-weighted; PI-RADS: prostate image reporting and data system; SNR: signal-to-noise ratio; DWI: diffusion-weighted imaging; ADC: apparent diffusion coefficient; DCE: dynamic contrast-enhanced. PI-QUAL: prostate imaging quality.

Figure 6.

A 77-year-old man with an elevated PSA of 6.95 ng/mL, gland volume 99 cc, and no prior prostate biopsy, underwent a biparametric prostate MRI. A. Axial T2-W image obtained with a PI-RADS-compliant technical parameters shows blurring of the prostate due to motion artifacts. A focal lesion with hypointense signal is noted on the left posterior peripheral zone (arrow). B-C. Axial calculated high b-value (b 1,400 sec/mm²) DWI and ADC map have low SNR and susceptibility artifacts from rectal gas, resulting in distortion of peripheral zone signal. D-E. The technologist recognized the limitations of DWI/ADC images and obtained the DWI and ADC map using the RESOLVE technique, which improved the SNR and decreased the geometric distortion of the prostate, making it more apparent the presence of a focal lesion with markedly hyperintense signal on calculated high b-value (1,400 sec/mm²) DWI (arrow, d) and markedly hypointense signal on ADC map (arrow, d) in the left apex/mid posterior peripheral zone. Since DWI/ADC and T2W images taken together were considered to have sufficient diagnostic quality, the exam was rated as PI-QUAL 3. The original interpretation of the images by a novice reader with 9 months of post-fellowship experience was PI-RADS score 2. Before the biopsy, the images were reviewed by a radiologist with 10 years of post-fellowship training who detected the left peripheral zone lesion and scored as PI-RADS 5 based on the DWI/ADC appearance. An MRI-guided biopsy of the lesion revealed Grade Group 3 prostate cancer with intraductal carcinoma features. Biopsy results were shared with the novice reader. This case highlights the role experienced technologists and radiologists play in quality assurance for prostate MRI and how poor image quality may impact inter-reader variability. PSA: prostate-specific antigen; T2-W: T2-weighted; DWI: diffusion-weighted imaging; ADC: apparent diffusion coefficient; SNR: signal-to-noise ratio; Resolve: readout segmentation of long variable echo-trains. PI-QUAL: prostate Imaging quality.