Are short magnetic resonance imaging protocols the future of prostate imaging?

With great interest, we read the recently published work by van der Leest et al. (1) on European Urology. The authors conducted a multi-reader, prospective study to investigate the diagnostic performance of standard multiparametricMRI (mp-MRI) versus unenhanced biparametric-MRI (bpMRI) in three planes and in one plane (“fast” bp-MRI) to detect high-grade prostatic carcinoma (PCa), in biopsynaïve men. The authors demonstrated that all protocols present a similar diagnostic performance in ruling out highgrade PCa. In particular, a “fast” bp-MRI protocol, only including axial T2w, ADC map, and high b-value images (three image sets), did not result in decreased detection of high-grade PCa. Table 1 summarizes the imaging sequences included in each of the protocols. Even though the negative predictive value (NPV) of “fast” bp-MRI was lower than that of bp-MRI and mp-MRI, the difference in NPV was clinically negligible (0.15%), and the NPV of “fast” bp-MRI remained high (97%). More details regarding diagnostic performance metrics reported using the three different protocols are shown in Table 2. The authors conclude that “fast” unenhanced bp-MRI can double prostate MRI capacity and reduce its costs, without impairing the detection of high-grade PCa. It is interesting to note that the imaging protocol used by the Authors is not completely in line with current Prostate Imaging Reporting and Data System (PI-RADS) guidelines. The main issues are the use of a gap in T2w and diffusion weighted imaging (DWI) sequences and the in-plane resolution of T2w images. This represents a potential limitation of the study, although reported results and accuracy of PI-RADS scoring does not seem negatively affected. Furthermore, recent publications highlighted the low adherence to PI-RADS acquisition guidelines both in the clinical and academic settings (2-4). Mp-MRI is considered the technique of choice to evaluate patients with suspicion of PCa, however, the long imaging acquisition time have contributed to a strong interest in reducing the length of mp-MRI. Several papers have demonstrated that bp-MRI protocols represent a valid alternative to mp-MRI (5-7). This is mainly due to the limited added value of dynamic contrast enhanced (DCE) over T2w imaging and DWI when using PI-RADS, for diagnosis of clinically significant PCa (8,9). In this study, van der Leest et al. clearly confirm the high diagnostic accuracy of shortening prostatic MR imaging, in biopsynaïve men with suspicion of PCa. The authors introduce an additional protocol modification and novelty, to further decrease the length of bp-MRI protocols, by eliminating coronal and sagittal T2w planes, thus reducing the overall acquisition time to 8 minutes. Additional strengths of the manuscript are the multireader evaluation, and a direct cost analysis confirming the benefits in terms of cost reduction (10). This paper nicely demonstrates the value of a “fast” bp-MRI protocol, without the administration of contrast Editorial Commentary