Prostate cancer is the second leading cause of cancer mortality in men. A widely used curative therapy for prostate cancer is prostate brachytherapy. This treatment involves the permanent placement of radioactive capsules (seeds) in the prostate, in a pattern that delivers a sufficient radiation dose to kill the cancer while maintaining a tolerable dose to the urethra and rectum. The seeds are loaded into hollow needles which are then inserted into the prostate through the perineum using a marked insertion template. The insertion is performed by a Radiation Oncologist or Urologist according to a plan generated by a Medical Physicist. Image guidance is provided during the procedures by B-mode trans-rectal ultrasound (TRUS) imaging. At present, there is no reliable method for determining the prostate within TRUS images - the apex and the base of the gland are not generally discernable. As well, there is no reliable method for determining the distribution of implanted seeds and therefore the delivered dose by TRUS imaging. The applicants plan to develop enabling technology to reliably image the prostate gland and the implanted seeds based on two novel ultrasound imaging methods they have developed - ultrasound vibro-elastography or VE and seed detection based on average reflected power of raw echo 'radio frequency"""""""" (RF) TRUS images. VE differs from conventional ultrasound imaging in that the RF data is processed while the tissue is vibrated, and reliably yields mechanical properties of tissue such stiffness and viscosity.
The specific aims of the project are to (1) develop a TRUS VE imaging system, (2) to develop and validate a VE-based method to determine the prostate boundary based on TRUS VE, and (3) to develop and validate seed detection based on VE and RF TRUS image processing. In order to achieve these objectives, a TRUS-VE system will be constructed to move a bi-plane trans-rectal probe inside the rectum. VE, fluoroscopic, and magnetic resonance images will be acquired from patients undergoing brachytherapy, and VE excitation signals and imaging parameters will be optimized to achieve high contrast of the prostate gland and seed localization. RF US -based seed localization algorithms will be optimized and compared to proven fluoroscopy-based localization. VE-based prostate boundary segmentation will be compared to B-mode images outlined by experts and to magnetic resonance images. ? ? ?
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