Abstract 5804: Validation of a Body Mass Index Adapted Scanning Protocol for Low-Dose 64-Slice CT Coronary Angiography with Prospective ECG-Triggering
As an increase in body mass index (BMI) confers a higher image noise in computed tomography coronary angiography (CTCA), we have validated a BMI-adapted scanning protocol for low-dose 64-slice CTCA with prospective electrocardiogram (ECG)-triggering. One-hundred-one consecutive patients underwent CTCA with prospective ECG-triggering, using a fixed contrast material protocol (80mL iodixanol, 50mL saline chaser, flow rate of 5mL/sec). Tube voltage and current were adapted to BMI (table⇓). Attenuation (Houndsfield units, HU) was measured and contrast-to-noise ratio (CNR) calculated for the proximal right coronary artery (RCA) and left main artery (LMA). Image noise was determined as the standard deviation of attenuation in the ascending aorta. Mean BMI was 25.7±4.3kg/m2 (range 18.2–38.8kg/m2) the mean effective radiation dose was 2.1±0.7mSv (range 1.0 –3.2mSv). There was no significant correlation between BMI and image noise (r= 0.11, P = 0.284), indicating optimal protocol adjustment. However, BMI was inversely correlated to vessel attenuation (RCA: r=−0.45, P<0.001; LMA: r=−0.47, P<0.001), and CNR (RCA: r=−0.39, P<0.001; LMA: r=−0.37, P<0.001). The proposed BMI-adapted scanning parameters results in similar image noise regardless of BMI. Increased bolus dilution due to larger blood volume may have contributed to a decrease in CNR and vessel attenuation in higher BMI as a fixed contrast material bolus was used.