Limitations of dual-photopeak window scatter correction for brain imaging.

Unlabelled: A method for performing scatter corrections that would directly use the photopeak information and would be straightforward for use in clinical practice would be attractive in SPECT imaging. The dual-photopeak window 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 dedicated brain camera.
Methods: Calibration curves for the Ceraspect, a dedicated brain imaging camera, were obtained for four split-window combinations using point sources in air and water. Simulations of the Ceraspect calibration curves at several energy resolution values were obtained using a Monte Carlo simulation of the instrument.
Results: The calibration curves, experimental and simulated, revealed an ambiguous and unstable relationship between lower-to-total ratio and scatter fraction.
Conclusion: The unsatisfactory calibration curves can be attributed to the limited scatter produced in a brain-sized phantom during the calibration process and inherent stability problems in the calibration process. The dual-photopeak window method is not usable for small-field imaging systems and may even be unstable for larger-field systems.