Guisheng Wang MD, Abstract Co-Author: Nothing to Disclose

Jianhua Gao, Presenter: Nothing to Disclose

Shuai Zhao BA, Abstract Co-Author: Nothing to Disclose

To evaluate the clinical value of an analytic mA and kV selection method based on patient BMI for consistent image quality and dose optimization in coronary CT angiography (CCTA).

We retrospectively analyzed two sets of CCTA images (group A) that were obtained with fixed scan protocols (100 patients with BMI≤26 at 100kV, 192.5mAs, and 100 patients with BMI>26 at 120kV, 175mAs). Image standard deviation (SD) on the ascending aorta was measured. The correlation between SD and BMI was used to establish a BMI-based formula to determine the required mA for obtaining a consistent CCTA image noise. Another 100 patients (group B) were scanned using the formula-determined mA/kV with the target image noise (IN) of 33HU and 28HU for BMI≤26 and >26, respectively. Image quality (IQ) and the effective dose (ED) from the two groups were measured and statistically analyzed using Mann-Whitney and Student t-test, respectively.

In the new scan parameter selection scheme, tube voltages of 100kVp and 120kVp were used for BMI≤26 and >26, respectively. The required mA for obtaining consistent image noise could be expressed analytically using BMI value and the desired image noise (desire-IN): mA=(a*(b*BMI-c)/desire-IN)2, where a, b and c are constants. Groups A and B had similar BMI distribution (25.97 vs. 25.18) (p=0.06). CCTA images in group B were 32.89HU and 28.53HU for the subgroups of BMI≤26 and >26, respectively, within 2% of the desired setting. There was no scan failure due to image noise and no statistical difference between IQ scores for groups A and B (4.61 vs. 4.58, p=0.55). The average effective dose for group B with adjusted mA was 1.82mSv, 20% less than the 2.26mSv for group A with statistical significance (p<0.001).

The BMI-based analytic mA/kV selection method for CCTA provides individualized protocol to obtain consistent image quality and to optimize dose delivery to patients of various BMI values.

Tube current and voltage selection based on BMI value can be used in CCTA to obtain consistent image quality and provides dose optimization for cardiac patients of various BMI values.

Wang, G, Gao, J, Zhao, S, BMI-based Analytic mA and kV Selection Method for Consistent Image Quality and Dose Optimization in Coronary CT Angiography.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043641.html