Automated attenuation-based selection of tube voltage and tube current for coronary CT angiography: reduction of radiation exposure versus a BMI-based strategy with an expert investigator

Christian Layritz, Gerd Muschiol, Thomas Flohr, Christian Bietau, Mohamed Marwan, Annika Schuhbaeck, Jasmin Schmid, Dieter Ropers, Stephan Achenbach, Tobias Pflederer
Journal of Cardiovascular Computed Tomography 2013, 7 (5): 303-10

BACKGROUND: Recently developed automated algorithms use the topogram and the corresponding attenuation information before coronary CT angiography (CTA) to allow for an individualized anatomic-based selection of tube current (mAs) and voltage (kV).

OBJECTIVES: The value of these algorithms in reducing the associated radiation exposure was evaluated.

METHODS: One hundred patients underwent coronary CTA with dual-source CT with prospectively electrocardiogram-triggered axial data acquisition. In all patients, tube parameters (current and voltage) were suggested by both an experienced investigator according to the patient's body mass index (BMI; calculated as weight divided by height squared; kg/m(2)) and by an automated software according to attenuation values of the initial topogram. The first 50 consecutive patients (group 1) underwent coronary CTA with dual-source CT with tube parameters suggested by the experienced investigator (BMI-based tube parameters), whereas in another 50 consecutive patients (group 2) CT data acquisition was performed with tube settings of the automated software. Subsequently, subjective image quality (4-point rating score from 0 = nondiagnostic to 3 = excellent image quality), image noise (SD of CT number within the aortic root), as well as signal- and contrast-to-noise ratios and mean effective radiation doses, were compared between both groups.

RESULTS: Both groups showed comparable image quality parameters (group 1 vs 2: noise, 28.1 ± 6.0 HU vs 29.9 ± 5.4 HU, P = .12; signal-to-noise ratio, 16.4 ± 3.9 vs 16.8 ± 4.1, P = .54; contrast-to-noise ratio, 18.6 ± 4.1 vs 19.2 ± 4.3, P = .49; 4-point rating score, 2.8 ± 0.3 vs 2.9 ± 0.3, P = .81). Tube voltage, current, and mean effective radiation dose for groups 1 and 2 were 111 ± 12 kV and 108 ± 12 kV (P = .18), 361 ± 32 mAs and 320 ± 48 mAs (P < .001), and 2.3 mSv (25th; 75th percentile, 1.5; 2.8 mSv) and 1.4 mSv (25th; 75th percentile, 1.1; 1.9 mSv) (P < .001), respectively.

CONCLUSIONS: Automated attenuation-based selections of individualized tube parameters are superior to BMI-based selections with expert oversight and show a potential for reduction of radiation exposure in coronary CTA, and image quality is maintained.

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