Radiation dose and image quality of 70 kVp functional cardiovascular computed tomography imaging in congenital heart disease

• Functional Ct datasets are often reconstructed in 6-8 mm slices for analysis.
• Higher noise levels are accepted for this indication.
• Lower kVp scans can be used for functional imaging without loss of image quality.

BackgroundThe use of cardiac computed tomography (CT) for quantification of ventricular function is limited by relatively high radiation dose.ObjectivesThe goal of this study was to describe the radiation exposure and image quality of 70 kVp functional cardiac CT in patients with congenital heart disease (CHD).MethodsA retrospective review of 70 kVp ECG gated functional CT scans using tube current modulation was performed in CHD patients at a single institution. Quantitative and qualitative (assessed by myocardial segment, 1 – 4; 1 = optimal) image quality was determined. Per segment image quality was compared between thin (1.5 mm) and thick (8 mm) reconstructions and by patient age and size. Scan DLP was used to estimate radiation dose.Results72 scans were performed during the time of review (7/2013-6/2015). Median patient age was 19.5 years (8.0, 27.1) and BMI was 20.1 (16.6, 24.5) kg/m2. Median functional scan DLP was 78.8 (45.5, 98) and unadjusted and adjusted procedural mSv were 1.10 (0.64, 1.37) and 1.13 (0.90, 1.37). Image quality of 1 was achieved in all myocardial segments in >75% of scans. Patients with a weight ≥75 kg were more likely to have a scan achieve optimal image when using thick reconstructions compared to thin (81.3% vs. 43.8%; p = 0.028).ConclusionsImaging of ventricular function with 70 kVp in CHD patients can be done with low radiation doses and provides diagnostic image quality, particularly for patients <75 kg. In larger patients, thicker slice reconstruction improved image quality.