Room: Exhibit Hall
Purpose: As the use of MRI has become a standard practice to delineate the target volume inside intracranial area, it is of clinical significance to investigate CT/MR fusion process which could benefit the most for identifying the CTV without possible geometrical miss or distortion.
Methods: Distortion by image fusion progress could introduce the uncertainties of target registration. Correction for nonlinear image registration errors seems to be logical but in the intracranial CT/MR registration, the distortion from deformation process maybe measured and presented as geometrical distortion. The Velocityâ„¢ rigid and deformation image registration modules were executed in a standard brain tumor case using T1 FLAIR pulse sequence. Both methodologies were applied and contouring results were presented in Figures 1-6.
Results: With typical intracranial image fusion of CT/MR datasets, rigid transformation with scaling has less registration errors compared to the selected deformation process. Case study has shown that bony landmarks with cavities carried better registration results than soft tissue matching. During the deformation process, the soft tissues matching presented larger weight than bony or cavity structures. Though matching of the region of interest (ROI) could be optimized to encompass the CTV to avoid misalignment, the surrounding soft tissues outside the ROI may not deform the same way as landmarks. The calculated vectors were just focusing on the tissues but ignored the existing cavities or bony structures. Calculated vectors indicated the best fit with the minimum Jacobian matrix value; however, the mathematical outcome presented incorrect critical structure registrations. MR Rigid transformation helped to preserve the shapes of both CTV and normal tissues without deformation drawbacks.
Conclusion: Using rigid transformation with scaling should be the optimum methodology to fuse the CT and MRI images, properly defining the ROIs will help to preserve better image registration and eliminate the inaccurate geometrical distortion in intracranial cases.
Not Applicable / None Entered.