Sebastian Tobias Schindera MD, Presenter: Research grant, Siemens AG

Rainer Raupach PhD, Abstract Co-Author: Employee, Siemens AG

Thomas Allmendinger, Abstract Co-Author: Employee, Siemens AG

Bernhard Schmidt PhD, Abstract Co-Author: Employee, Siemens AG

Peter Vock MD, Abstract Co-Author: Nothing to Disclose

Zsolt Szucs-Farkas MD, PhD, Abstract Co-Author: Nothing to Disclose

To assess the effect of automatic selection of tube voltage on reduction of the radiation dose for CT angiography in various body sizes in a phantom study.

An abdominal aortic phantom was placed into three different cylindrical water containers (diameters of 22, 30, and 40 cm, respectively) simulating a small, an intermediate-sized, and a large patient. The aortic phantom was filled with 1:30 dilution of iodinated contrast medium (iodine concentration, 300 mg/mL) and tap water. The phantom was scanned on a 64-MDCT scanner (Somatom Sensation Cardiac 64; Siemens Healthcare, Forchheim, Germany) using 120 kVp and a quality reference tube current–time product of 110 mAs (reference CT angiography protocol). Then, the optimal tube voltage and tube current, recommended by an automatic tube voltage tool (CARE kV, Siemens) to achieve best dose efficiency at a constant contrast-to-noise ratio (CNR), were used in all three phantom sizes. The attenuation of the aorta, of the background and the image noise was measured and the CNR was calculated. The radiation dose was assessed by the CTDIvol.

The CTDIvol measured for the simulated small, intermediate-sized, and large patient 3.53, 7.46, and 14.56 mGy at 120 kVp, respectively. The automatic tube voltage tool recommended 80 kVp for the simulated small and intermediate-sized patient and 100 kVp for the large patient. At these voltages, the CNR values were kept constant compared with the 120-kVp protocol (12.2, 7.0 and 3.8 for simulated small, intermediate-sized, and large patient, respectively). In comparison to the reference 120-kVp CT angiography protocol, the dose reduction measured 69% at 80 kVp for the small patient, 63% at 80 kVp for the intermediate-sized patient and 20% at 100 kVp for the large patient.

The automatic tube voltage tool may substantially reduce the radiation dose at constant CNR for CT angiography in different sized patients. For simulated small and intermediate-sized patients tube voltage of 80 kVp and for simulated large patient 100 kVp is automatically selected. The automatic tube voltage tool allows greater radiation dose reduction in smaller body sizes.

Automatic tube voltage selection may increase the use of low tube voltage settings for CT angiography resulting in a lower radiation dose to the patient.

Schindera, S, Raupach, R, Allmendinger, T, Schmidt, B, Vock, P, Szucs-Farkas, Z, Effect of Automatic Selection of Tube Voltage on Radiation Dose Reduction for CT Angiography in Various Body Sizes: A Phantom Study  .  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11010957.html