Prostate cancer(PCa) has the high incidence and is the second most common cause of cancer-related deaths in the male population¹. Detection of clinically significant PCa is a major challenge. MR imaging is a useful tool for PCa detection and staging, with a promising role in risk stratification². MR Elastography (MRE) is a method to probe the mechanical properties of tissue, and has been shown to be useful in many diagnostic applications³, and has potential to provide complementary information for improving the diagnosis of PCa. The aim of our study was to evaluate the technical feasibility and potential diagnostic value of MRE of the prostate gland, using a novel approach to generate shear waves in the prostate via mode conversion, using a conventional urinary catheter.This pilot study enrolled 19 patients (mean age: 71.47±9.43 years; range: 43–82 years;mean body mass index: 21.51±3.41 kg/m²; range: 14.98–27.55 kg/m2), including 16 patients with benign prostate hyperplasia (BPH) and 3 with prostatic cancer(PCa) proven by biopsy results and clinical follow up. Preoperative prostate-specific antigen(PSA, 0-5ng/ml) and free-PSA(F-PSA, 0-1 ng/ml) were retrospectively evaluated. MRE of the prostate gland was performed within one week prior to pathological examination. All patients had conventional rubber urethral catheters in place at the time of examination. An active MRE acoustic driver system with a passive drum driver (Resoundant Inc., Rochester, MN), normally used for liver MRE, was positioned over the lower abdominal wall partially overlapping the superior border of the symphysis pubis. MRE was performed on a 3.0T scanner (GE, Discovery MR750) with a free-breathing, multislice, single-shot, flow-compensated, spin-echo EPI, 2D-MRE sequence using 60-Hz vibrations (acquisition matrix = 80x80; parallel imaging factor of 2;TR/TE =1667/56.3ms; 4 time points; scan time = 40 sec; 24-cm FOV; 20 3-mm axial slices; through-plane motion encoding with bipolar, 6.45-ms, 50-mT/m motion-encoding gradients on each side of the refocusing pulse).The MRE magnitude and phase images were processed using the multi-model direct inversion algorithm (MMDI)to calculate the stiffness. Stiffness maps were automatically generated by the software on the MR scanner and displayed. The reliability of stiffness measurement was assessed by measuring the SNR of the magnitude images and the encoded amplitude of the acoustic waves. Regions of interest(ROIs) were drawn in the central zone(CZ), the peripheral zone(PZ) and in the PCa area, and were adjusted to exclude areas with the prostatic catheter, prostate edges, significant wave interference. Mean prostate stiffness (in kilopascals (kPa)) within the ROIs was recorded. The t-test was used to test for differences in the stiffness of the CZ and PZ in BPH, and to compare the stiffness between PCa and BPH. Statistical significance was defined as P<0.05.The PSA and F-PSA were 9.17 ng/ml (median, range: 0.77-179.02ng/ml) and 2.40 ng/ml(median, range: 0.23-159.52ng/ml ) in BPH patients, and 155.08 ng/ml( median, range: 36.48-306.88ng/ml) and 8.81ng/ml(median, range: 5.99-14.47ng/ml) in PCa patients, respectively. As illustrated in Figures 1b,1e and 1h, Mechanical waves were successfully propagated into the prostate gland in all patients, except for the regions near transurethral catheter. The mean stiffness values were 4.28±0.79 kPa (range: 3.05-5.29 kPa) in the CZ, and 3.11±0.69 kPa (range: 2.14-4.51 kPa) in the PZ in BPH group (Figures 1c and 1f). The difference between CZ and PZ was statistically significant (P<0.001). The mean stiffness value of regions of PCa was 6.10±1.72kPa (range: 4.20-7.52 kPa) (Figure 1i), which was higher than the mean PZ stiffness of patients with BPH (P<0.001), but was not significantly different from the mean CZ stiffness in regions with BPH (P=0.203).A number of approaches for illuminating shear waves into the prostate have been proposed, including abdominal, perineal, and endorectal drivers^3-7. We previously found that a vibration source attached to a conventional urinary catheter couldgenerate ideal cylindrical wave fields in the prostate, radiating from the urethral margin. This study demonstrated that similar results can be achieved using a conventional abdominal driver, when a urinary catheter is in place. The most likely explanation for the mechanism is that longitudinal waves from the abdominal driver are mode-converted to shear waves at the catheter-uretheral interface. Our preliminary measurements indicated that the CZ is significantly stiffer than the PZ in patients with BPH and that the stiffness of PCa was higher than that of the PZ in BPH. Further development of this technique is warranted.MRE has a potential role for providing additional information for improved diagnosis and localization of prostate diseases.