Applications of Advanced Ultrasound in Prostate Cancer

Prostate Cancer (PCa) is one of the most commonly diagnosed malignancy in men. In case of abnormal/rising Prostate Specific Antigen (PSA) levels or abnormal digital rectal examination (DRE), transrectal ultrasound (TRUS) is used to detect suspicious areas. If biopsy is required, a preliminary multiparametric magnetic resonance imaging (mpMRI) is recommended. However, mpMRI can miss a significant number of tumours.

Conventional TRUS B-mode imaging has limited sensitivity with a specificity below 50%, and the use of Color/Power Doppler does not significantly improve diagnostic performance. TRUS as a multiparametric imaging technique TRUS becomes a multiparametric imaging technique through the development of advanced techniques such as: Micro-Doppler imaging increases slow flow detection which can be helpful for prostate nodule characterization. It can be performed without or after ultrasound contrast agent intravenous injection. High frequency micro-US imaging provides high-resolution, real-time prostate imaging resulting in higher spatial resolution.

TR-CEUS improves PCa detection but faces technical limitations due to the transient hypervascular enhancement of PCa. As most PCa are stiffer than normal prostate tissue, elastography can be used to improve PCa detection rate. Two different techniques can be used: Strain analysis and shear wave elastography (SWE). In strain analysis, soft tissues will exhibit a higher strain (deformation) than stiffer areas which improves the identification of abnormal stiff areas. Limitations of this technique include if a patient has a large prostate, operator dependency and lack of true quantitative information. In SWE, PCa appears as a stiff hypoechoic lesion with correlation between stiffness and PCa aggressiveness. However, all stiff lesions are not cancers (such as nodules with micro calcifications) and all cancers are not stiff. To obtain precise PCa diagnosis, mpTRUS should be used. These provide complementary information that when fused, improve biopsy guidance and staging that are mandatory for further development of focal therapy.