BERKELEY, CA (UroToday.com) - The topic of prostate segmentation using MRI might have been of little interest to urologists several years ago. Now, with the rise of MRI-US fusion biopsy systems as a means of guiding prostate biopsies, the topic is far more relevant. To review, an MRI-US fusion biopsy system begins with a diagnostic multiparametric prostate MRI. This image is reviewed by radiologists and suspicious lesions are identified. If these are deemed clinically worthy of a biopsy, then the prostate gland must be segmented electronically and this segmentation, along with the locations of the suspicious lesions, are electronically transmitted to the US device, typically located in an office or procedure room remote from the MRI. When the patient returns for the actual biopsy, he undergoes a 3D ultrasound whereupon an US segmentation of the prostate is also obtained. The US segmentation is then electronically fused to the MRI segmentation either manually or using deformable registration in order to guide the biopsy -- which is performed under US. After all this is performed, then the patient is finally ready for his biopsy. Thus, an MR-US fusion biopsy system, requires a close working relationship between radiologists and urologists. One concern for the long-term sustainability of MR-US fusion biopsy is ensuring that the needed work flow is not overly burdensome to either side.
The significance of this article is that it describes a totally automatic method of performing prostate segmentation executed equivalently to manual segmentation obtained by painstakingly drawing the contours of the prostate on each section of the MRI. The task of manually demarcating each section of a prostate MRI is both time-consuming and tedious and likely to be met with resistance. On the other hand, if a fully automated system could perform just as well, it would require merely the press of a button followed by a few seconds of calculation. The fact that these two methods of segmentation are equivalent is excellent news for the adoption of MRI-US fusion biopsy systems as it relieves a significant bottleneck from the process of preparing the MRI for fusion with ultrasound.
Parenthetically, this study also revealed that the ellipsoid method of prostate volume determination (length x width x height x 0.52) which has been used for many years, was much less accurate than either the manual or automatic system of prostate volume determination, based on mRI. With the increasing use of MRIs for prostate cancer, hopefully more accurate prostate volume determinations will result in the future.
Thus, a fully automated system of prostate volume segmentation from MRI data is available and has been implemented on several commercial platforms. It is accurate and fast and should remove at least one of the barriers to the ultimate successful implementation of MR-US fusion biopsy of the prostate.
Peter Choyke, MD as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
Molecular Imaging Program, National Cancer Institute, National Institutes of Health, 10 Center Dr, MSC 1182, Bldg 10, Rm B69, Bethesda, MD 20892-1088 USA