Bhoj Raj Sharma MBBS, MD, Presenter: Nothing to Disclose

Madhu Gupta MBBS, Abstract Co-Author: Nothing to Disclose

Yuan Qing Hai MD, PhD, Abstract Co-Author: Nothing to Disclose

The protocol of low tube voltage CCTA using 100 kV/1000mAs retrospective ECG-gated shows significant reduction of the radiation dose without disturbing the subjective image quality of CCTA.

To evaluate the image quality and radiation dose of 100kv with 1000mAs retrospectively electrocardiography (ECG)-gated CTCA protocol, compared to the standard protocol of 120kV with 800 mAs retrospective ECg-gated CTCA.

Although the objective image quality of the 100-kV with 1000 mAs was significantly better than the 120-kV with 800 mAs (mean SNR, 36.65 ± 2.95 vs. 33.47 ± 3.86, P < 0.0001; mean CNR, 34.27 ±2.92 vs. 30.62 ±3.90, P < 0.0001). There was no significant variation in the subjective image quality between two groups of patients with normal body mass index (mean image score, 4.54 ± 0.37 vs. 4.56 ± 0.25 for radiologist 1, P = 0.781; 4.52 ± 0.25 vs. 4.56 ± 0.25 for radiologist 2, P = 0.486). The radiation dose was found to be reduced by 28 % with the 100-kV/1000mAs protocol than with the standard protocol of 120-kV/800mAs retrospective ECG-gated CCTA (7.87 ± 0.59 vs. 10.95 ± 1.67 mSv, P <0.0001).

We evaluated the CCTA images of 70 patients with normal body mass index (18.5 kg/m2 and 25 kg/m2). We divided 70 patients into two, a reduced dose group with 35 patients (18 M, 17 F; Mean age 56.94 ± 11.51 years) were examined by 100-kV with 1000 mAs retrospective ECG-gated CCTA, and another as a standard group with 35 patients (21 , 14 F; Mean age 54.03 ± 9.81 years) were examined by 120-kV with 800 mAs retrospective ECG-gated CCTA. The two blinded radiologists analyzed the image quality of the coronary arteries independently. They performed a subjective and an objective image quality. The subjective image quality was assessed according to 5-point scoring scale. The objective image quality was measured in terms of a signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR].The radiation dose was also measured as effective radiation dose [ED] and was calculated using CT dose volume index [CTDIvol.], dose-length product [DLP] and conversion coefficient for chest (conversion factor k=0.014 mSv mGy-1cm-1).

Sharma, B, Gupta, M, Hai, Y, 256-slice Coronary Computed Tomography Angiography Using Low Voltage 100kV.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14013716.html