Radiation dose of cardiac dual-source CT: the effect of tailoring the protocol to patient-specific parameters

Abstract

Objective: To determine the radiation doses and image quality of different dual-source computed tomography coronary angiography (CTCA) protocols tailored to the heart rate (HR) and body mass index (BMI) of the patients.

Materials and methods: Two hundred consecutive patients (68 women; mean age 61+/-9 years) underwent either helical CTCA with retrospective ECG-gating or sequential CT with prospective ECG-triggering: 50 patients (any BMI, any HR) were examined with a standard, non-tailored protocol (helical CTCA, 120 kV, 330 mAs), whereas the other 150 patients were examined with a tailored protocol: 40 patients (group A, BMI<or=25 kg/sqm, HR<or=70 bpm) with sequential CTCA (100 kV, 190 mAs(ref)), 43 patients (group B, BMI</=25 kg/sqm, HR>70 bpm) with helical CTCA (100 kV, 220 mAs), 28 patients (group C, BMI>25 kg/sqm, HR<or=70 bpm) with sequential CTCA (120 kV, 330 mAs(ref)), and 39 patients (group D, BMI>25 kg/sqm, HR>70 bpm) with helical CTCA (120 kV, 330 mAs). The effective radiation dose estimates were calculated from the dose-length-product for each patient. Image quality was classified as being diagnostic or non-diagnostic in each coronary segment.

Results: Image quality was diagnostic in 2403/2460 (98%) and non-diagnostic in 57/2460 (2%) of all coronary segments. No significant differences in image quality were found among all five CTCA protocols (p=0.78). The non-tailored helical CTCA protocol was associated with a radiation dose of 9.0+/-1.0 mSv, being significantly higher compared to that using sequential CTCA (group A: 1.3+/-0.3 mSv, p<0.001; group C: 2.9+/-0.6 mSv, p<0.001), and helical CTCA at reduced tube voltage and tube current (group B: 4.2+/-0.6 mSv, p<0.01). No significant differences were found compared to the non-tailored CTCA protocol in patients with HR>70 bpm (group D: 8.5+/-0.9 mSv, p=0.51).

Conclusions: Dual-source CTCA is associated with radiation doses ranging between 1.3 and 9.0 mSv, depending on the protocol used. Tailoring of the CTCA protocol to the HR and BMI of the individual patient results in dose reductions of up to 86%, while maintaining a diagnostic image quality of the examination.