Three-dimensional ultrasound-guided minimally invasive therapy of the prostate

Prostate cancer is the most commonly diagnosed cancer in men in North America. Although 2D transrectal ultrasound imaging is widely used for the evaluation of prostate disease it suffers from limitations that limit its use in diagnosis and therapy of prostate cancer. The outcome of a 2D-ultrasound guided minimally invasive procedure depends on the skill and expertise of the operator in manipulating the transducer and in forming a correct mental impression of the 3D anatomy and pathology. In addition, the process of quantifying and monitoring small changes during the therapeutic procedure is also severely limited by using a spatially variable 2D imaging technique. We have developed a 3D ultrasound imaging approach that overcomes these problems. In this paper, we describe a 3D ultrasound imaging system for use in prostate imaging and report on its performance. The system consists of a conventional ultrasound machine, a microcomputer with an video frame grabber, and a custom-built assembly for rotating the ultrasound transducer. A typical scan of 100 2D B-mode images takes 7 seconds. These images can then be reconstructed into a 3D image, which can be displayed and interactively manipulated using 3D visualization software. We also show that the process of reconstruction does not distort the geometry, and that the 3D system can be used to localize brachytherapy seeds in phantoms with a precision (SEM) of better than 0.4 mm. We also show that the 3D system can be used to image brachytherapy seeds in patients post-implantation.