Haptic Simulation of Prostate Cancer Based on Magnetic Resonance Elastography

Magnetic Resonance Elastography (MRE) has the potential to provide quantitative estimations of the mechanical properties of biological tissue, which may be linked to tumor malignancy. The goal of this project was to develop a virtual reality haptic simulation of a prostate phantom and human ex-vivo MRE data, providing 3D visual and tactile feedback. A haptic virtual 3D prostate model was created by scanning a plastic phantom (CIRS Tissue Simulation & Phantom Technology) with an ultra-high field 9.4 T Agilent horizontal bore preclinical MRI system (310/ASR). MRE data was processed by performing full 3D Helmholtz direct inversion to the noise-filtered 3D wave displacement data. ITK-SNAP was used to produce a semi-automatic volume segmentation of the MRI data, and generate 3D polygonal meshes of all phantom components (i.e., prostate, urethra, seminal vesicles, rectal wall, and tumors). The second study, consisted in the simulation of the MRE and the direct virtual interaction with the volumetric data. This approach was further implemented with the MRE data of 5 ex-vivo prostates. A haptic device (3DSystems Touch X) was used to explore the virtual prostate model. Haptic feedback was produced by: 1) detecting the contact between the haptic probe and the 3D polygonal meshes that represent the phantom components, and 2) computing a viscoelastic effect based on the real coefficients of the shear modulus map (SMM) provided by the MRE data and 3) a volume haptics rendering algorithm that defines a transfer function providing different stiffness, viscosity, different ranges of the SMM. The results of this preliminary study suggest the feasibility of using a novel combination of magnetic resonance imaging, elastography, and haptic technologies on prostates to better identify tumor locations and sizes, and more accurately perform cancer staging. This methodology tested with a plastic prostate phantom was also applied to MRI/MRE scanned in-vivo prostates of patients with prostate cancer for ultimately studying the potential of improving pre-surgical planning of radical prostatectomy.