To determine the feasibility of prospective electrocardiogram (ECG)-gating to achieve low-dose computed tomography coronary angiography (CTCA). Forty-one consecutive patients with suspected (n = 35) or known coronary artery disease (n = 6) underwent 64-slice CTCA using prospective ECG-gating. Individual radiation dose exposure was estimated from the dose-length product. Two independent readers semi-quantitatively assessed the overall image quality on a five-point scale and measured vessel attenuation in each coronary segment. One patient was excluded for atrial fibrillation. Mean effective radiation dose was 2.1 ± 0.6 mSv (range, 1.1–3.0 mSv). Image quality was inversely related to heart rate (HR) (57.3 ± 6.2, range 39–66 b.p.m.; r = 0.58, P < 0.001), vessel attenuation (346 ± 104, range 110–780 HU; r = 0.56, P < 0.001), and body mass index (26.1 ± 4.0, range 19.1–36.3 kg/m²; r = 0.45, P < 0.001), but not to HR variability (1.5 ± 1.0, range 0.2–5.1 b.p.m.; r = 0.28, P = 0.069). Non-diagnostic CTCA image quality was found in 5.0% of coronary segments. However, below a HR of 63 b.p.m. (n = 28), as determined by receiver operator characteristic curve, only 1.1% of coronary segments were non-diagnostic compared with 14.8% with HR of >63 b.p.m. (P < 0.001). This first experience documents the feasibility of prospective ECG-gating for CTCA with diagnostic image quality at a low radiation dose (1.1–3.0 mSv), favouring HR <63 b.p.m.

Purpose: To prospectively determine the accuracy of 64-section computed tomographic (CT) angiography for the depiction of coronary artery disease (CAD) that induces perfusion defects at myocardial perfusion imaging with single photon emission computed tomography (SPECT), by using myocardial perfusion imaging as the reference standard. Materials and Methods: All patients gave written informed consent after the study details, including radiation exposure, were explained. The study protocol was approved by the local institutional review board. In patients referred for elective conventional coronary angiography, an additional 64-section CT angiography study and a myocardial perfusion imaging study (1-day adenosine stress-rest protocol) with technetium 99m–tetrofosmin SPECT were performed before conventional angiography. Coronary artery diameter narrowing of 50% or greater at CT angiography was defined as stenosis and was compared with the myocardial perfusion imaging findings. Quantitative coronary angiograph...

Recent advances in SPECT technology including cadmium–zinc–telluride (CZT) semiconductor detector material may pave the way for absolute myocardial blood flow (MBF) measurements by SPECT. The aim of the present study was to compare K₁ uptake rate constants as surrogates of absolute MBF and myocardial flow reserve index (MFRi) in humans as assessed with a CZT SPECT camera versus PET. Methods: Absolute MBF was assessed in 28 consecutive patients undergoing adenosine stress–rest myocardial perfusion imaging (MPI) by ^99mTc-tetrofosmin CZT SPECT and ¹³N-ammonia PET, and MFR was calculated as a ratio of hyperemic over resting MBF. Results from both MPI methods were compared, and correlation coefficients were calculated. The diagnostic accuracy of CZT MFRi to predict an abnormal MFR defined as PET MFR less than 2 was assessed using a receiver-operator-characteristic curve. Results: Median MBF at rest was comparable between CZT and PET (0.89 [interquartile range (IQR), 0.77–1.00] vs. 0.92 [IQR, 0.78–1.06] mL/g/min; P = not significant) whereas it was significantly lower at stress in CZT than PET (1.11 [IQR, 1.00–1.26] vs. 2.06 [IQR, 1.48–2.56] mL/g/min; P < 0.001). This resulted in median MFRi values of 1.32 (IQR, 1.13–1.52) by CZT and 2.36 (IQR, 1.57–2.71) by PET (P < 0.001). The receiver-operator-characteristic curve revealed a cutoff for CZT MFRi at 1.26 to predict an abnormal PET MFR yielding an accuracy of 75%. Conclusion: The estimation of absolute MBF index values by CZT SPECT MPI with ^99mTc-tetrofosmin is technically feasible, although hyperemic values are significantly lower than from PET with ¹³N-ammonia, resulting in a substantial underestimation of MFR. Nevertheless, CZT MFRi may confer diagnostic value.