An investigation of dual-energy transmission measurements for more accurate non-uniform attenuation compensation in cardiac SPECT

In this study we investigate the use of dual energy transmission imaging, in simultaneous transmission-emission tomography. Transmission projection data are acquired using the two major photopeaks of ¹⁵³ Gd, at 44 keV and 99 keV. The degree of contamination of the data in the 44 keV window, by scattered 99 keV transmission photons, is investigated using Monte Carlo simulations. A new method is proposed to convert the two transmission maps measured at 44 keV and 99 keV to one appropriate for ^99mTc. This transmission map is compared with one produced by scaling the 99 keV map, for the attenuation correction of ^99mTc emission data. The use of dual energy transmission imaging is shown to improve the quantitative accuracy of the reconstructed emission maps. Dual energy transmission imaging is also shown to be more effective at visualizing areas of bone, particularly in truncated regions of the object