Image Quality and Radiation Dose Assessment in Different Cardiac CT Angiography Techniques

introduction:
Coronary artery disease(CAD) is the situation of narrowing or blockage of your heart supplying arteries lumen caused by fatty material build-up called plaque leading to impairment in oxygen delivery to the myocardium.
The standard diagnostic tool for CAD is still conventional coronary angiography which takes advantage of high resolution and identifies the presence and extent of CAD which is followed by risks and specific complications.
Computed tomography angiography(CTA) is a certified non-invasive imaging tool used as the main alternative to conventional coronary angiography for coronary artery disease assessment which is increasingly gaining importance. This procedure benefits from high sensitivity and specificity for CAD detection while, has the disadvantage of high radiation dose that due to potential cancer risk remains a non- negligible concern for physicians and radiologists so lots of strategies have been developed to reduce radiation dose-encompassing dose modulation techniques with retrospective and prospective ECG triggering and FLASH (a prospective ECG triggered data.
This study was intended to compare radiation dose and image quality across three groups of patients undergoing different CCTA methods, including prospective, retrospective, and FLASH.
Material and Method:
A dual-source scanner (384 slice, Siemens) was used for data acquisition in both FLASH and Pros/Retrospective CTA. The two major parameters of radiation dose assessment are CT dose index(CTDI) and Dose Length Product(DLP) which are used to calculate the SSDE (Size Specific Dose Estimation). A python-based software was developed by our team to read the required data including CTDI and DLP from the DICOM header and automatically calculate the effective diameter which can be used to determine the desired conversion factor and result in the geometrical measurement of SSDE.
Results:
Different parameters for radiation dose assessment, including wSSDE, gSSDE, effective dose, and exposure obtained for the three CCTA methods, including prospective, retrospective, and FLASH methods. A comparison of the CCTA methods for the same parameter reveals a significant difference in the radiation dose received by the patient.
The prospective protocol is known as the standard protocol for cardiac imaging and increasing pitch value is used to reduce radiation dose with good diagnostic accuracy. prospective ECG-triggered data acquisition with very high pitch values (FLASH) provides images with high image quality for patients with a heartbeat of less than 60 and also a sharp depreciation in radiation dose received by the patient. the Retrospective protocol offers a
high amount of radiation dose in comparison with others and also not a good image quality in compare with prospective which is probably due to severe motion artifact.
Conclusion:
384-slice CTA enables us to visualize the coronary arteries using 3 different protocols that are selected to be performed based on the patient’s heartbeats. Prospective ECG
Triggered data acquisition for heartbeats<60 offers an acceptable image quality with a sharp depreciation In radiation dose. For heartbeats, more than 60 to 75 prospective scannings represent the first choice. If the heartbeat goes over 75, the retrospective is considered as the final alternative, dose reduction using a relatively low tube voltage and using tube modulation would be necessary.