Lifeng Yu PhD, Presenter: Nothing to Disclose

Cynthia H. McCollough PhD, Abstract Co-Author: Research grant, Siemens AG

Joel Garland Fletcher MD, Abstract Co-Author: Research grant, Siemens AG

Hua Li PhD, Abstract Co-Author: Nothing to Disclose

Katharine Grant PhD, Abstract Co-Author: Employee, Siemens AG

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

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

Thomas G. Flohr PhD, Abstract Co-Author: Employee, Siemens AG

Terri Jo Vrtiska MD, Abstract Co-Author: Nothing to Disclose

Eric E. Williamson MD, Abstract Co-Author: Consultant, Siemens AG

Optimal kV selection in CT is dependent on both patient size and diagnostic task. The purpose of this study is to quantify the dose reduction and demonstrate the workflow of a newly developed quantitative tool, which allows for automatic selection of the most dose-efficient kV for thoracic and abdominal CT angiography (CTA).

We developed a novel strategy that allows automatic adaptation of kV as a function of patient size and diagnostic task. This strategy was implemented on the scanner with a parameter setting freely adjustable for different diagnostic tasks. The optimal kV is selected based on both this parameter and the patient attenuation level determined from the topogram. The tube current system limit is also considered. With a parameter setting for CTA exams, two experimental studies, one using 4 semi-anthropomorphic thoracic phantoms (30, 35, 40, and 45 cm) and the other with 7 abdomen phantoms (25, 30, 35, 40, 45, 50, and 55 cm), were performed to quantify the radiation dose reduction achievable using this tool and to demonstrate the workflow of optimal kV selection for both thoracic and abdominal CTA exams. Two iodine samples (3.5 and 6.9 mg/cc) were placed inside the phantoms to allow measurement of iodine contrast to noise ratio (CNR). The relative radiation dose at each kV to achieve the same iodine CNR as in the reference 120 kV was calculated.

The automatic kV selection tool provides a flexible and quantitative way to select the optimal kV based on the patient size, diagnostic task, and tube current limits. For the 4 thoracic phantoms in the experiment, the optimal kVs were 80, 80, 100, 100, respectively, with corresponding relative doses of 37.6, 44.4, 60.8, and 89.5%. For the 7 abdomen phantoms, the most dose-efficient kVs were 80, 80, 100, 100, 100, 120, and 140, respectively. The corresponding radiation dose relative to 120 kV scans of the same phantom were 57.8, 66.6, 73.9, 75.9, 79.3, 100, and 87.2%.

An automatic kV selection tool was developed to provide a quantitative way to select the most dose-efficient kV in thoracic and abdominal CTA. Dependent on the patient size, the optimal kV settings suggest dose reductions of up to 62.4%.

Optimal kV selection for thoracic and abdominal CTA requires consideration of patient size. The developed quantitative tool automates this process to achieve dose reductions up to 62.4%.

Yu, L, McCollough, C, Fletcher, J, Li, H, Grant, K, Raupach, R, Schmidt, B, Flohr, T, Vrtiska, T, Williamson, E, Potential for Radiation Dose Reduction in Thoracic and Abdominal CT Angiography Using an Automatic kV Selection Tool: A Phantom Study.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9012070.html