Three-dimensional contrast-ultrasound dispersion imaging for prostate cancer localization, a feasibility study

Prostate cancer (PCa) is the type of cancer with the highest incidence in men in Western countries. To date, reliable tools for PCa localization are lacking. Recently, contrast-ultrasound dispersion imaging (CUDI) by spatiotemporal analysis performed on transrectal dynamic contrast-enhanced ultrasound (DCE-US) has been proposed as a promising option for PCa localization. This technique evaluates the spatial similarity between indicator dilution curves in a ring-shaped kernel and its center pixel. Until now, CUDI has been performed in 2D only. Hence, each imaged plane requires a separate bolus injection of contrast agent, motion compensation is limited, and out-of-plane contrast flow cannot be observed. 3D DCE-US can potentially solve the aforementioned issues, permitting the analysis of the entire prostate with a single bolus injection. In this work, we implemented a full 4D spatiotemporal similarity analysis. Its feasibility to localize PCa was evaluated in 2 patients by qualitatively comparing similarity maps obtained by 3D CUDI with those obtained by 2D CUDI in the corresponding planes and with histopathologic results from 12-core systematic biopsies. All results showed good agreement, confirming the feasibility of 3D CUDI for PCa localization and encouraging extension of the study to a larger dataset. Additionally, the characteristics - and in particular the spatial and temporal resolution - of 3D DCE-US were analyzed with respect to the requirements for CUDI. Both the spatial and temporal resolution were considered to be sufficient for CUDI.