Hyun Woo Goo MD, Presenter: Nothing to Disclose

Dong Soo Suh BS, Abstract Co-Author: Nothing to Disclose

To evaluate the dose reduction in non-electrocardiography (ECG)-gated heart CT by automatic online tube current modulation in children, and the effects of body weight, age, sex, and scan techniques on dose reduction.

From September 2004 to January 2005, non-ECG-gated heart CT examinations were performed with automatic online tube current modulation in 50 children (median age: 1 year, range 1 month – 16 years; M:F = 29:21) with congenital heart disease. Sixteen-slice spiral CT studies were obtained with weight-based low dose protocol (80 kVp, 50 – 160 effective mAs). CT scans were obtained along craniocaudal direction when leg veins (n = 36) were used for intravenous injection of contrast agent. In contrast, CT scans were obtained along caudocranial direction when arm veins (n = 13) were used. In one child who underwent Fontan operation, both arm and leg veins were used. We calculated dose reduction in non-ECG-gated heart CT by automatic online tube current modulation. In addition, we evaluated the effects of body weight, age, sex, and scan techniques on dose reduction.

The dose reduction by automatic online tube current modulation was 15.8±11.1%. The degrees of dose reduction for each body weight group were variable (9.3±7.9% for 0–4.9 kg, 14.3±9.3% for 5–9.9 kg, 16.4±12.5% for 10–19.9kg, 25.8±9.8% for 20–39.9 kg, 15.9±12.7% for 40–59.9 kg). When eight children in 40 – 59.9 kg group were excluded, the age showed a significant positive correlation with the dose reduction (γ = 0.4, P = 0.003). There was no significant difference in the dose reduction between boys and girls. The dose reduction was significantly greater in caudocranial scan direction (21.2±9.2%) than in craniocaudal scan direction (14.2±11.3%) (P = 0.049).

The average dose reduction by automatic online tube current modulation is 15.8% in non-ECG-gated heart CT. With our CT protocol, the age up to 39.9 kg in the body weight shows a significant positive correlation with the dose reduction and the dose reduction is significantly greater in caudocranial scan direction than in craniocaudal scan direction.

Goo, H, Suh, D, Dose Reduction in Non-electrocardiography-gated Heart CT by Automatic Online Tube Current Modulation in Children.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4409004.html