Long-term prognostic performance of low-dose coronary computed tomography angiography with prospective electrocardiogram triggering
To evaluate the use of CT attenuation maps, generated from coronary calcium scoring (CCS) scans at in- and expiration with a 64-slice CT scanner, for attenuation correction (AC) of myocardial perfusion SPECT images. Thirty-two consecutive patients underwent 99mTc-tetrofosmin gated adenosine stress/rest SPECT scan on an Infinia Hawkeye SPECT-CT device (GE Medical Systems) followed by CCS and CT angiography on a 64-slice CT. AC of the iteratively reconstructed images was performed with AC maps obtained: (a) from the “Hawkeye” low-resolution X-ray CT facility attached to the Infinia camera (IRAC); (b) from the CCS scan acquired on a 64-slice CT scanner during maximal inspiration (ACINSP) and (c) during normal expiration (ACEXP). Automatically determined uptake values of stress scans (QPS, Cedars Medical Sinai) from ACINSP and ACEXP were compared with IRAC. Agatston score (AS) values using ACINSPversus ACEXP were also compared. ACINSP and ACEXP resulted in identical findings versus IRAC by visual analysis. A good correlation for uptake values between IRAC and ACINSP was found (apex, r=0.92; anterior, r=0.85; septal, r=0.91; lateral, r=0.86; inferior, r=0.90; all p<0.0001). The correlation was even closer between IRAC and ACEXP (apex, r=0.97; anterior, r=0.91; septal, r=0.94; lateral, r=0.92; inferior, r=0.97; all p<0.0001). The mean AS during inspiration (319±737) and expiration(317±778) was comparable (p=NS). Attenuation maps from CCS allow accurate AC of SPECT MPI images. ACEXP proved superior to ACINSP, suggesting that in hybrid scans CCS may be performed during normal expiration to allow its additional use for AC of SPECT MPI.