Target localization in MRI-guided prostate biopsy
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Prostate cancer is a worldwide health concern for men. Needle biopsy is the most definitive form of cancer diagnosis. Target-specific biopsies can be performed under magnetic resonance imaging (MRI) guidance. However, needle placements are often inaccurate due to intra-operative prostate motion and the lack of motion compensation techniques. As a result, malignant tumors can be missed, which in turn will lead to an increased number of repeated biopsies and delaying of treatment. To increase the needle targeting accuracy, intra-operative prostate motion and deformation need to be studied so that motion compensation techniques can be developed accordingly. This thesis intends to make three main contributions: 1. A comprehensive survey of the state-of-art in image-guided prostate needle placement interventions. 2. Retrospective clinical accuracy validation of a MRI-guided robotic prostate biopsy system that was used in the U.S. National Cancer Institute for over 6 years. A 3D-3D registration algorithm consists of an initial two-step rigid alignment followed by a B-spline deformable transform was developed to align the pre- and post-needle insertion images. A total of 90 biopsies from 24 patients were studied. The mean target displacement, needle placement error, and clinical biopsy error were 5.2, 2.5, and 4.3 mm, respectively. 3. Development of a multi-slice-to-volume registration for intra-operative target localization. The algorithm aligns the planning volume with three orthogonal image slices of the prostate acquired immediately before needle insertion. It consists of a rigid registration followed by a deformable step using only the prostate region. The algorithm was validated on 14 clinical images sets from Brigham and Women's Hospital in Boston, Massachusetts. All registration errors were well below the radius of a clinically significant tumour (5 mm), and are considered clinically acceptable. The results show that there was a substantial amount of biopsy error caused by prostate motion and deformation during MRI-guided biopsy. This error can be reduced by using quantitative imaging techniques for prostate registration and motion compensation. In particular, the multi-slice-to-volume registration algorithm demonstrated the feasibility of intra-operative target localization and motion compensation; which in turn may improve the quality of MRI-guided prostate interventions.