Arterial spin labelling as a contrast-free alternative to dynamic contrast enhancement for the evaluation of peripheral zone prostatic lesions on MRI.

PURPOSE: To assess the correlation between ASL-derived perfusion parameters and enhancement pattern on DCE in patients with histologically uncharacterized lesions of the peripheral prostatic zone.

MATERIALS AND

METHODS

Prospective study: informed consent was obtained. We included 52 patients with peripheral zone lesions ≥4 mm, PI-RADS ≥3. All patients underwent PI-RADS-recommended multiparametric MRI and ASL acquisition using a Flow-sensitive Alternating Inversion Recovery (FAIR) with True Fast Imaging with Steady-State Precession (True-FISP) pulse sequence at 3 T. DCE images were assessed for early focal enhancement (DCE+). Two radiologists independently measured prostatic blood flow (PBF) in the lesion and adjacent normal PZ tissue; the mean of the values was used for further analysis. The PBF ratio (lesion/healthy tissue) was calculated. Statistical analysis included Mann-Whitney U, Wilcoxon tests, and ROC curve analysis.

RESULTS

Fifty-two lesions with median diameter of 8 mm (IQR: 6-12 mm) were included. On DCE, 31/52 (60 %) were DCE+, and 21/52 (40 %) were DCE-. Interobserver agreement for PBF measurements was excellent (ICC 0.980-0.994). Median PBF was significantly higher in target lesions than in healthy tissue (28.03 vs. 15.76 ml/100 g/min, p = 0.0003). DCE+ lesions showed significantly higher PBF than DCE- ones (39.17 vs. 19.04 ml/100 g/min; p = 0.0001), as well as a significantly higher PBF ratio (2.6 vs. 1.09; p < 0.0001). On ROC analysis, PBF ratio showed an AUC of 0.97 (95 % CI: 0.87-0.99; p < 0.0001) in discriminating between DCE+ and DCE- lesions; a cut-off value of >1.66 provided 86 % sensitivity and 100 % specificity in identifying DCE+ lesions.

CONCLUSIONS

ASL may serve as a safe, contrast-free alternative for evaluating vascularization of peripheral prostatic zone lesions.