The Application Of Coronary CT Angiography With ECG-controlled Tube Current Modulation

Application of coronary CT angiography with ECG- controlled tube current modulationObjective:At present, coronary heart disease is one of the most common threating factors to human health and quality of life.With improved living conditions,the incidence of coronary heart disease and associated mortality have increased.MSCT coronary artery angiography as a non-invasive examination method being efficient and associated with fewer complications,is widely used clinically.Usually in coronary CT angiography,retrospective ECG gating modulation is used.Retrospective ECG gating modulation uses high-resolution low-pitch scan overlap and radiation dose is quite high. Radiation dose can result in some potential radiation induced cancers.Many researches are aimed at how to reduce the radiation dose.Many methods can be used to reduce the dose of X-ray examination and one of most common method is by reducing the tube current.Tube current should be kept to a minimum but at the same time ensuring a good image quality and be clinically helpful.Reasonable tube current and improved use of X-rays are the focus in the radiation dose reduction research.Hence the use of ECG-controlled tube current modulation began to be investigated.This current work is focused on ECG-controlled tube current modulation during coronary CT angiography and then retrospectively compare image quality and radiation dose. The aim is to know whether ECG-controlled tube current modulation ensures a reasonable image quality meanwhile reducing the radiation dose.Method: At our institution from May 2010 to December 2010, 62 patients with suspected coronary atherosclerotic disease were chosen and have undergone coronary CT angiography using a 256 MSCT scanner.They were randomly divided into two groups with 31 patients in each. All patients had no severe liver and kidney dysfunction or a history of allergies iodine contrast agents.Group A was performed with the retrospective ECG gating modulation, group B was performed with the ECG-controlled tube current modulation. Image quality of both groups are compared in a subjective and objective way. Subjective evaluation mainly evaluation image quality score.Objective evaluation include the signal to noise ratio , contrast to noise ratio of the images obtained and associated radiation dose.Result:During subjective evaluation of image quality in both groups of patients,the mean image quality score was 3.25 points in group A and the mean image quality score was 3.05 points in group B.There was no significant difference between both groups(P = 0.61).During objective evaluation,in group A the mean image SNR was (14.41±1.05) and in group B the mean image SNR was (15.07±3.29).There was no significant difference between two groups(P=0.29).In the group A the mean image CNR was (12.03±0.98) while in the group B the mean image CNR was (12.64±3.02) and there was no significant difference between both groups(P=0.28).In the group A the average effective dose (ED) was (10.77±0.96)mSv and in the group B the average effective dose (8.59±2.50)mSv. There was significant difference between both groups (P<0.001).Conclusion:256-slice CT coronary angiography with ECG-controlled tube current modulation can reduce radiation dose about 20.2%, while maintaining image quality compared with retrospectively ECG gating modulation.