Low dose 320-row CT for left atrium and pulmonary veins imaging—the feasibility study

Abstract

To evaluate the feasibility of low dose target-CTA volume scan for left atrium and pulmonary veins imaging using 320-row CT. Forty-two patients (females 12, males 30; mean age 55.2 years; mean body mass index (BMI) 25.7 kg/m(2)) with persistent or intermittent atrial fibrillation before catheter ablation were enrolled in this study. Scan protocol was target-CTA volume scan under prospective ECG-gating. The target of the exposure was only set at 40% of the R-R interval (which was at the left atrium maximal volume). The exposure time was minimal setting (350 ms). Tube voltage 100 kV (BMI ≤ 25 kg/m(2)) or 120 kV (BMI>25 kg/m(2)), tube current 350-420 mA, and field of view of 180 mm × 180 mm-200 mm × 200 mm were used. The scanning range was from the level of the tracheal bifurcation to the diaphragm, and enabled to cover the left atrium and central pulmonary veins (120-140 mm). All of patients were divided into two groups according kV setting (100 kV and 120 kV). The image quality (good, moderate and poor) was evaluated by two reviewers. The CT-attenuation, image noise and contrast to noise ratio (CNR) of left atrium and every pulmonary vein branch were evaluated, respectively. The effective dose (ED) was calculated using a conversion coefficient for the chest 0.017. Of 42 patients, the image quality was good in 26 cases (62%) and moderate in 16 cases (38%). There was no statistical difference in the CT-attenuation and CNR of left atrium and central pulmonary veins between the two groups (P>0.05). The mean ED was 1.90 ± 0.19 mSv (range 1.57-2.25 mSv) in 100 kV group, and 3.83 ± 0.31 mSv (range 3.39-4.54 mSv) in 120 kV group. The low dose target-CTA volume scan is feasible in pulmonary veins and left atrium imaging using 320-row CT. Slim patients can be scanned at 100 kV setting without loss of image quality.