AUTOMATED ALIGNMENT AND SIZING OF MYOCARDIAL STRESS AND REST SCANS TO3-DIMENSIONAL NORMAL TEMPLATES USING AN IMAGE REGISTRATION ALGORITHM

To optimize the interpretation of myocardial SPECT, we developed an au tomated method for alignment, sizing and quantification of images usin g three-dimensional reference templates. Methods: Stress and rest refe rence templates were built using a hybrid three-dimensional image regi stration scheme based on principal-axes and simplex-minimization techn iques. Normal patient studies were correlated to a common orientation, position and size. Aligned volumes were added to each other to create amalgamated templates. Separate templates were built for normal stres s and rest SPECT Tc-99m-sestamibi scans of 23 men and 15 women, The sa me algorithm was used to correlate abnormal test-patient studies with respective normal templates, The robustness of the fitting algorithm w as evaluated by registering data with simulated defects and by repeate d registrations after arbitrary misalignment of images. To quantify re gional count distribution, 18 three-dimensional segments were outlined on the templates, and counts in the segment were evaluated for all te st patients. Results: Our technique provided accurate and reproducible alignment of the images and compensated for varying dimensions of the myocardium by adjusting scaling parameters. The algorithm successfull y registered both normal and abnormal studies. The mean registration e rrors caused by simulated defects were 1.5 mm for position, 1.3 degree s for tilt and 5.3% for sizing (stress images), and 1.4 mm, 2.0 degree s and 3.7% (rest images); these errors were below the limits of visual assessment. Conclusion: Automated three-dimensional image fitting to normal templates can be used for reproducible quantification of myocar dial SPECT, eliminating operator-dependence of the results.