13 March 2006 A hybrid deformable model for simulating prostate brachytherapy
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Abstract
Ultrasound (US) guided prostate brachytherapy is a minimally invasive form of cancer treatment during which a needle is used to insert radioactive seeds into the prostate at pre-planned positions. Interaction with the needle can cause the prostate to deform and this can lead to inaccuracy in seed placement. Virtual reality (VR) simulation could provide a way for surgical residents to practice compensating for these deformations. To facilitate such a tool, we have developed a hybrid deformable model that combines ChainMail distance constraints with mass-spring physics to provide realistic, yet customizable deformations. Displacements generated by the model were used to warp a baseline US image to simulate an acquired US sequence. The algorithm was evaluated using a gelatin phantom with a Young's modulus approximately equal to that of the prostate (60 kPa). A 2D US movie was acquired while the phantom underwent needle insertion and inter-frame displacements were calculated using normalized cross correlation. The hybrid model was used to simulate the same needle insertion and the two sets of displacements were compared on a frame-by-frame basis. The average perpixel displacement error was 0.210 mm. A simulation rate of 100 frames per second was achieved using a 1000 element triangular mesh while warping a 300x400 pixel US image on an AMD Athlon 1.1 Ghz computer with 1 GB of RAM and an ATI Radeon 9800 Pro graphics card. These results show that this new deformable model can provide an accurate solution to the problem of simulating real-time prostate brachytherapy.
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David Levin, Aaron Fenster, Hanif M. Ladak, "A hybrid deformable model for simulating prostate brachytherapy", Proc. SPIE 6141, Medical Imaging 2006: Visualization, Image-Guided Procedures, and Display, 61410Q (13 March 2006); doi: 10.1117/12.651913; https://doi.org/10.1117/12.651913
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