Worldwide, prostate cancer is the second leading cause of death due to cancer in men, accounting for between 2.1% and 15.2% of all cancer deaths. In Canada, about 18,200 new prostate cancer cases will be diagnosed and about 4,300 men will die from this disease in 2002. When diagnosed at this early stage, the disease is curable, and even at later stages treatment can be effective. The prostate-specific antigen (PSA) blood test is well established for early detection of prostate cancer, and for monitoring of prostate cancer after treatment. The wide availability of the PSA test, the public's increased awareness about prostate cancer, and the growing number of men approaching the age of 50, have all combined to increase the proportion of prostate cancer diagnosed at an early-stage. In the past decade improvements in imaging technology (trans-rectal ultrasound (TRUS), computer aided dosimetry, and new treatment options have stimulated investigators to search for minimally invasive therapies for localized prostate cancer. Ultrasound-guided brachytherapy is the most advanced and is now considered to be one of the definitive treatment option for early stage prostate cancer.
Although brachytherapy is now widely used, the procedure is still susceptible to variability and inaccuracy due to factors such as the patient's anatomy (pubic arch interference), dosimetry optimization (parallel and rigid spacing of needle insertion), precision of needle placement (out-of-plane uncertainty in 2D TRUS), anatomical changes during the procedure (swelling due to edema), non-optimal post-plan (not carried out intra-operatively immediately after the implantation). In this proposal, we propose to overcome these limitations by developing an dynamic prostate brachytherapy approach, allowing adjustments to the procedure intra-operatively. This will be accomplished through the introduction of robotic aids and real-time image processing and integrating these with our 3D US guided prostate brachytherapy developments. Our ultimate goal is to develop and validate an accurate, precise and adjustable prostate brachytherapy system, in which all aspects of the procedure are carried out intra-operatively including planning, monitoring of prostate changes, dynamic re-planning and optimal needle implantation including oblique trajectories.
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Figure 1 (above).
(a) Schematic diagram showing the conventional TRUS guided brachytherapy procedure with the rectilinear template guiding needles in parallel trajectories. Note that the anterior portion of the prostate is not reached by the needles.
(b) A 2D TRUS prostate image post implantation.
(c) 3D TRUS image of the same patient as in 1b. The 3D image has been sliced in the transverse and longitudinal directions showing the seeds.
(d) The same image sliced in the coronal plane, showing the seeds.
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Figure 2 (right). Display of a typical dose plan using the 3D TRUS system. Our 3D visualization approach allows display of a texture-mapped 3D view of the prostate, extracted planes, and graphical overlays of surfaces and contours.
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Our efforts are based on our long-term hypothesis, which is that by combining 3D TRUS imaging with robotic aids and novel software tools, a dynamic intra-operative prostate brachytherapy procedure will be developed that will be more accurate, consistent and efficient than the current procedure. We intend to test this long-term hypothesis as part of the collaborative efforts between our Imaging Research Laboratory at the Robarts Research Institute, Radiology and Urology at the London Health Sciences Centre and Radiation Oncology at the London Regional Cancer Centre. Our specific technical objectives are:
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To develop and integrate all the hardware and software tools for robotic aided 3D TRUS prostate brachytherapy system, allowing needle insertion in oblique trajectories using a virtual template under the control of the robot.
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To validate needle placement and trajectory accuracy with the following specifications: (a) needle tip placement at the patientÕs skin with an error <+1mm; (b) needle trajectory error ±2°; and (c) needle tip placement at a targeted location in 3D with an error <±2mm.
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To develop and validate a method to track the brachytherapy needle during oblique insertion with an error ±1mm and display the calculated oblique insertion US plane in near real-time.
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To develop a segmentation algorithm to localize the seeds in the prostate intra-operatively as they are being implanted with an accuracy of ±2mm and in real-time (1 US frame time).
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To determine the true positive and false positive rates of the real-time brachytherapy seed localization as the seeds are being implanted. 6. To develop an algorithm to monitor changes (due to swelling) in the prostate during the implantation procedure with an accuracy of ±2mm and in less than 5s.
Investigators: Fenster A, Downey D, Chin J., Vekatesan, V.
Programmers: Gardi, L.
Graduate Students: Gang W., Wei, Z.
Technicians: Blake C.
Support: CIHR , ORDCF
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E-mail: afenster@imaging.robarts.ca
Phone: (519) 663-3833 Fax: (519) 663-3900
Copyright 2005 © All rights reserved.
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