Introduction: Diagnostic imaging techniques using fluoro‐deoxy‐glucose (FDG) — positron emission tomography (PET) and magnetic resonance imaging (MRI) offer tumor‐specific imaging capabilities for breast cancer imaging. Combining PET‐MRI systems may provide synergistic information on abnormal soft tissue processes useful for discriminating tumor from other soft tissue abnormalities that may mimic tumor. We propose a deformable image registration method able to align MRI series over an FDG‐PET dataset which may improve metastatic for breast cancer imaging. Method: To more precisely replicate presentation of FDG‐PET when analyzing FDG‐PET/MRI, a deformable registration method was devised to correct locally defined posture changes. To mathematically represent the deformations, we use a BSpline model whose coefficients are iteratively calculated in small steps using a gradient‐based optimization algorithm under the guidance of a mutual information metric. The deformable BSpline approach technique was evaluated using checkerboard views and compared to a rigid body registration. Results: Comparison of rigid versus deformable registration of checkerboard FDG‐PET and MRI images revealed superior results for deformable registration. The deformable registration was feasible and showed exact anatomical correlation between FDG‐PET and MR images in a checkerboard. Increased activity from the FDG‐PET scan clearly corresponded to anatomical structures on the MR images. Clinically, the deformable registration of FDG‐PET and MRI revealed the complimentary information. Regions of increased FDG activity on PET‐CT, which was initially rated as possible tumor disease, were evaluated based on the additional soft tissue information available from the MRI. In one patient case, MRI revealed a benign uterine fibroid which was not definitive on PET‐CT. Conclusion: Deformable image registration of PET‐CT and MRI using a BSpline algorithm is feasible for metastatic breast cancer detection.
ASJC Scopus subject areas
- Radiology Nuclear Medicine and imaging