DETECT - DUAL-ENERGY TRANSMISSION ESTIMATION CT - FOR IMPROVED ATTENUATION CORRECTION IN SPECT AND PET

Accurate attenuation correction is a vital component of any quantitati ve Emission CT (ECT) study, especially I-131-mIBG SPECT where accurate activity concentration measurements are required for dosimetry calcul ations. Conventional CT is often used to obtain an attenuation map, wh ich is then scaled to the I-131 emission energy (364, KeV). Scaling in accuracies due to the increased photoelectric component of the attenua tion coefficients of bone af: CT energies lead to an overestimate of a ctivity. Dual Energy CT is more accurate but must be justified against increased cost, scan time and dose to the patient. We propose a metho d (DETECT) of obtaining two attenuation maps from a single CT scan usi ng a conventional CT scanner operating at 120 and 140 kVp for alternat e slices. Each map's missing slices are reconstructed using weighted l inear interpolation. The effect of the x-ray beam spectrum has been in vestigated by simulated scaling using the CT spectra and by a phantom study. Assuming a perfect emission detector, segmented abdominal CT da ta predicts a mean activity overestimate of 2+/-3% for DETECT compared to 12+/-5% for the standard single energy (120 kVp) CT method when sc aled to 364 keV, suggesting that DETECT can offer reliable attenuation correction with no dose or user penalty.