PI-RADS-v2 was released for the same language between the radiologist and the clinicians that used for early recognition of PCa [1, 3]. PI-RADS-v2 has a remarkable role in diagnosing PCa and provides a uniform protocol of mp-MRI, allowing a good range of interobserver agreement [20,21,22]. One study reported that good interobserver agreement rates use the most appropriate analysis (AC1 = 0.71) and moderate use kappa analysis (kappa = 0.43) . Few studies reported good interobserver agreement using PI-RADS V2 with a remarkable effect on the radiologist’s prior experience [19,20,21,22,23,24]. In our work, we found an excellent interobserver agreement using PI-RADS-v2 in reporting MP-MRI for prostate lesions. The difference in the results from the other studies may be attributed to the image analysis in our study which was done by two uroradiologists with a long time of experience compared to other studies which used general radiologists with a variable degree of experience.
In this study, there is an excellent interobserver agreement of both readers as they have a long period of experience of 15 and 10 years, respectively. Previous studies reported that the readers’ experience has an effect on the diagnostic performance of PI-RADS v2. The expert radiologists could recognize significant prostate cancer using PI-RADS-v2 with good agreement overall , and the agreement tended to be better in PZ than TZ, although was weak for DCE in PZ . There is a moderate agreement of PI-RADS of all categories of PCa (k = 0.53) and clinically significant cancers (csPCa) (k = 0.47) . One study reported that the interobserver agreement of PI-RADS is (k = 0.71) for both zones: for PZ (0.72) and for TZ (0.44) . Another study added that the overall interobserver agreement is 0.41 for PI-RADS score 3–5 and 0.51 for PI-RADS score 4–5 . The third study reported that interobserver agreement in PI-RADS v2 ranges from fair to good among radiologists and improves with increasing experience . The last study added that radiologists across experience levels had an excellent agreement for detecting index lesions and moderate agreement for category assignment of lesions using PI-RADS .
One study confirmed mp-MRI ability uncovering clinically significant PC with variability among radiologists , and another study added that PI-RADS-v2 had a moderate inter-reader agreement, with PI-RADS scores linking well with the possibility of intermediate- and high-grade cancers . However, a prior study referred to that it is restricted by an at-best moderate degree of agreement between readers .
The PZ lesion assessment depends mainly on DWI with a minor role for DCE [1,2,3]. Our work showed an excellent interobserver agreement for PZ lesions. Another study concluded a better interobserver agreement according to categories of the PZ than the TZ lesion .
Our study revealed a good interobserver agreement for TZ lesions. TZ lesion assessment depends mainly on T2-WI with a secondary role for DWI [5,6,7,8,9,10,11,12,13,14,15,16]. In a previous study, lesions of the PZ show good agreement regarding extra-prostatic extension and invasive behavior on T2-WI. The TZ lesions showed good agreement regarding EPE and moderate/marked hypointensity on T2-WI, while the corresponding positive or negative early enhancement at DCE had fair agreement .
PI-RADS-v2 follows the conception of “dominant sequence” as T2 is the hallmark for TZ and DWI is the hallmark for the PZ, with a minor role of the DCE [1,2,3,4,5]. In our study, there is an overall good agreement for PI-RADS in both the PZ and TZ. In addition, our study is unique as it assessed the interobserver agreement for each sequence by itself.
In PI-RADS-v2, T2WI is the cornerstone in the assessment of TZ lesions, with a minor role of the PZ lesion only to depict the abnormal morphological patterns [1,2,3,4,5]. One study reported that the interobserver agreement for T2-WI is 0.47 and 0.15 in the PZ and 0.37 and 0.07 in the TZ . In our study, T2-WI features of TZ lesions have been reported with an excellent interobserver agreement.
In our study, the DWI score of the PZ lesions revealed good agreement and that of TZ lesions revealed excellent agreement. DWI is used for assessment of oncology all over the body. One study reported that in PZ, reproducibility was moderate on DWI (κ = 0.535–0.619), fair on DCE (κ = 0.266–0.439), and fair for extraprostatic extension on T2-WI (κ = 0.289). In TZ, reproducibility for lesion texture and margins on T2-WI ranged from 0.136 (moderately hypointense) to 0.529 (encapsulation) . Another study added that encapsulated lenticular shape on T2WI, focal on DWI, and marked hypointensity on ADC map had a moderate agreement (K = 0.45 to 0.60), whereas heterogeneous and circumscribed on T2-WI, marked hyperintensity on high b value DWI, and the presence or not of early enhancement in the lesion/region of the lesion had a fair agreement (K = 0.30 to 0.38) .
In PIRDAS-v2, DCE changed from 5 points scoring to be rather −ve or +ve denoting lesser role than it was having in PI-RADS-v1 and different regions of the body. DCE is currently recognized as a second sequence in diagnosing PZ lesions. One study reported that the interobserver agreement of DCE is fair (k = 0.48–0.41) . In our work, features related to DCE for the PZ lesions were reported with an excellent agreement.
Our study has a few limitations. First, the reference standard was a TRUS-guided biopsy with a sampling error. Second, although this study was focused on lesion characterization according to the PI-RADSv2 assessment categories, it limited its ability to evaluate the accuracy of this method for lesion detection. Further multicenter studies are needed upon a large number of patients with calculation accuracy of Pi-RADS V2 in the detection of prostate lesions. Third, we applied PIRADS-v2 for the analysis of prostate lesions. We are recommending further studies with application advanced diffusion modules such as diffusion tensor imaging, MR spectroscopy, arterial spin labeling with machine learning, and whole-body imaging for staging of PCa.