Original articles

Cardiac imaging and non-invasive testing

First head-to-head comparison of effective radiation dose from low-dose 64-slice CT with prospective ECG-triggering versus invasive coronary angiography

B A Herzog¹, C A Wyss¹, L Husmann¹, O Gaemperli¹, I Valenta¹, V Treyer¹, U Landmesser¹, P A Kaufmann^1,2

¹ Nuclear Cardiology, Ramistrasse 100, University Hospital Zurich, 8091 Zurich, Switzerland
² Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Switzerland

^{Correspondence to} Professor Philipp A Kaufmann, Nuclear Cardiology, University Hospital Zurich, Ramistrasse 100, CH-8091 Zurich, Switzerland; pak{at}usz.ch

Background: Reduction of radiation burden of multidetector computed tomography coronary angiography (CTCA) has remained an important task.

Objective: To compare effective radiation dose of low-dose 64-slice CTCA using prospective ECG-triggering versus diagnostic invasive coronary angiography (CA).

Methods: 42 patients referred for elective invasive CA owing to suspected coronary artery disease (CAD) were prospectively enrolled to undergo a low-dose CTCA without calcium scoring within the same day before CA. Dose-area product of diagnostic invasive CA and dose-length product of CTCA were measured, converted into effective radiation dose and compared using Mann-Whitney U tests. In addition, accuracy of CTCA to detect CAD (coronary artery narrowing 50%) was assessed using invasive CA as standard of reference. On an intention-to-diagnose basis all non-evaluative vessels were included in the analysis and censored as positive.

Results: The estimated mean effective radiation dose was 8.5 (4.4) mSv (range 1.4–20.5 mSv) for diagnostic invasive CA, and 2.1 (0.7) mSv (range 1.0–3.3 mSv) for CTCA (p<0.001). 19 patients (42.9%) had no CAD by invasive CA. 40 (95.2%) patients have been correctly classified as having CAD (23/23) or no CAD (17/19). Over 97% (551/567) of segments were evaluable. Vessel-based analysis revealed sensitivity, specificity, positive and negative predictive value of 94.2% (CI 0.8% to 1.0%), 94.8% (CI 09% to 1.0%), 89.0% (CI 0.8% to 1.0%), 97.4% (CI 09% to 1.0%) and an accuracy of 94.6%.

Conclusions: Low dose CTCA allows evaluation of CAD with high accuracy, but delivers a significantly less effective radiation dose to patients compared to diagnostic invasive CA.

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