LIMITATIONS OF DUAL-PHOTOPEAK WINDOW SCATTER CORRECTION FOR BRAIN IMAGING

A method for performing scatter corrections that would directly use th e photopeak information and would be straightforward for use in clinic al practice would be attractive in SPECT imaging. The dual-photopeak w indow method may be such a method. It relates the scatter fraction to the ratio of the lower to the total parts of a split-photopeak window, We investigated the use of this scatter correction method on a dedica ted brain camera. Methods: Calibration curves for the Ceraspect(TM), a dedicated brain imaging camera, were obtained for four split-window c ombinations using point sources in air and water. Simulations of the C eraspect(TM) calibration curves at several energy resolution values we re obtained using a Monte Carlo simulation of the instrument. Results: The calibration curves, experimental and simulated, revealed an ambig uous and unstable relationship between lower-to-total ratio and scatte r fraction. Conclusion: The unsatisfactory calibration curves can be a ttributed to the limited scatter produced in a brain-sized phantom dur ing the calibration process and inherent stability problems in the cal ibration process. The dual-photopeak window method is not usable for s mall-field imaging systems and may even be unstable for larger-field s ystems.