Chul hwan Park MD, Presenter: Nothing to Disclose

Hyung Min Kim, Abstract Co-Author: Nothing to Disclose

Donghyun Hong MS, Abstract Co-Author: Nothing to Disclose

Tae Hoon Kim MD, Abstract Co-Author: Nothing to Disclose

To evaluate the influence of quantitatively measured thoracic components on the image noise of low dose cardiac CT and compare with that of BMI.    

Ninety-three patients (M:F = 65: 28, mean age = 54.8 ± 8.4 years) who underwent low kVp prospective ECG-gated CTCA and low dose chest CT were enrolled and analyzed retrospectively. All CTCA was performed on a 128-slice CT scanner (Ingenuity Core 128, Philips Healthcare, The Netherlands) with an iterative reconstruction technique (iDose4). The scanning parameters were as follows: step-and-shoot axial scanning, 420-ms gantry rotation time, 100 kV, 150 mA, 64 x 0.625-mm slice collimation). The image noise of CTCA was determined by the standard deviation of the attenuation value in an ROI that was placed on the aortic root, just above the orifice of left main coronary artery. On the low dose chest CT, the areas of thoracic components were measured at the same level using auto-segmentation technique with various threshold levels as follows; Lung (Quantitatively Measured Area of Lung (QMAlung): -910 HU ~ -200 HU), Fat (QMAfat: -200 HU ~ 0 HU), Soft tissue (QMAsoft tissue: 0 HU ~ 300 HU), and Bone (QMAbone: 300 HU ~ 1000HU). The relationship between image noise and various parameters including body weight, BMI, and various QMAs were analyzed. The linear correlation coefficients between parameters and noise were compared as the indicator of the association strength.  

The mean image noise in the aorta root was 46.8±10.2 HU. In 93 patients, a linear correlation coefficient of BMI was 0.682 and that of QMA (Fat+Soft tissue) was 0.779. In men, the linear correlation of QMA (Fat+Soft tissue) (r=.745) was higher than that of BMI (r=0.659). In women, the correlation of QMA (Fat+Soft tissue) (r=.915) was higher than that of BMI (r=.860). The mean effective radiation dose of CTCA was 1.97 ± 0.2 mSv.

QMA (Fat+Soft tissue) shows a good correlation with image noise of cardiac CT, especially in women.

When cardiac CT with low kVp is performed, quantitative measurement of thoracic component could be a useful indicator for adequate patient selection.

Park, C, Kim, H, Hong, D, Kim, T, Predicting the Image Noise Level of the Low Kilovoltage Prospective ECG-gated CT Coronary Angiography: Quantitative Measurement of Thoracic Component versus Body Mass Index.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14017719.html