Tomoelastography of the prostate using multifrequency MR elastography and externally placed pressurized‐air drivers
Several challenges exist for the advancement of prostate magnetic resonance elastography (MRE) 6. The most relevant are shear wave damping due to the central location of the prostate in the pelvis, and resolution of stiffness details due to the high heterogeneity in small tissue volumes. To overcome these challenges, different techniques have been proposed including transurethral 7, endorectal 8, and transperineal 10 drivers. The transurethral approach has not been demonstrated in humans so far, whereas the endorectal approach allows application of mechanical vibrations at higher frequencies but is more invasive than approaches with externally placed drivers. The transperineal approach uses an externally placed driver and is thus better suited for screening examinations but requires specialized driver hardware dedicated to prostate examinations with installation times of 8 to 10 min before each MRE scan 11.
Our study has three main objectives: (i) Demonstrate the technical feasibility of prostate MRE using robust externally placed pressurized‐air drivers, which have been used in previous investigations of other organs including the liver, spleen, pancreas, and kidneys 12; (ii) propose a multifrequency MRE protocol with a short scan time of less than 10 min, including full 3D wave field acquisition and tomoelastography wave‐speed reconstruction 14: and (iii) use the new method to analyze regional prostatic stiffness in healthy volunteers and patients.
Although reproducibility and reference values are measured in healthy volunteers, a case study of five subjects with benign and malignant alterations of the prostate is presented for demonstrating the clinical feasibility of the protocol.