Table 1.

Summary of recommendations Listed by section heading or subheading containing relevant text within the document

Radiation dose standards and measurements

The volume CT dose index (CTDIvol) [expressed in units of mGy] should be used for optimizing cardiovascular CT protocols.

The dose-length-product (DLP) [expressed in units of mGy-cm] should be used for comparing radiation doses and characterizing radiation dose from a cardiovascular CT study.

Radiation risk

Estimations of stochastic risk from radiation delivered during medical imaging examinations should be interpreted cautiously, considering the uncertain relationship between dose and risk at low levels of radiation dose.

Potential risk of future stochastic events must be balanced with the potential benefits of the examination and potential risks of forgoing the examination or obtaining a nondiagnostic examination because of excessive dose reduction.

General methods for radiation dose reduction

Appropriate use criteria

Cardiovascular CT should only be performed if indicated by best available evidence and published guidelines, appropriate use criteria, or certain clinical scenarios or patient-specific clinical factors/comorbidities that support testing for a given patient.

The cardiovascular CT imaging protocol should be tailored to the clinical question and patient characteristics.

Scan modes

Retrospective ECG-gated helical techniques may be used in patients who do not qualify for prospective ECG-triggered scanning because of irregular heart rhythm or high heart rates or both (specific value depends on specific scanner characteristics and cardiovascular indication).

Prospective ECG-triggered axial techniques should be used in patients who have stable sinus rhythm and low heart rates (typically <60-65 beats/min, but specific values depend on specific scanner characteristics and cardiovascular indication).

For prospective ECG-triggered axial techniques, the width of the data acquisition window should be kept at a minimum.

Tube potential

A tube potential of 100 kV could be considered for patients weighing ≤90 kg or with a BMI ≤ 30 kg/m2; a tube potential of 120 kV is usually indicated for patients weighing >90 kg and with a BMI > 30 kg/m2. Higher tube potential may be indicated for severely obese patients.

Tube current

If retrospective ECG-gated helical data acquisition is indicated, ECG-based tube current modulation should be used except in patients with highly irregular heart rhythm.

The scanner default tube current values should be adjusted, based on each individual patient's size and clinical indication, to the lowest setting that achieves acceptable image noise.

Scan length

The scan length should be set at the minimum length clinically necessary.

Reconstruction slice thickness

Images should be reconstructed with the greatest possible slice thickness for the given cardiovascular CT indication, and the tube current should be adjusted with the understanding that a lower tube current can be used with the reconstruction of thicker slices.

Predictors of radiation dose with cardiac CT

Use of breast shields is not recommended for cardiovascular CT.

Imaging centers (especially those initiating coronary CT angiography and those with lower case volumes) may participate in collaborative quality improvement programs.

Applying algorithms for dose optimization in clinical practice

Individual sites should consider developing site-specific algorithms for radiation dose optimization, which should be reviewed and revised if needed at least annually.

Considerations for coronary calcium scoring

Coronary calcium scans should be performed with prospective ECG-triggered axial or prospective ECG-triggered helical techniques, a 120-kV tube potential, a patient size-adjusted tube current, and the widest beam collimation that allows for reconstruction of 3-mm slices.

Considerations for coronary CT angiography

If coronary calcium scans can only be performed with retrospective ECG-gated helical scanning, ECG-based tube current modulation should be used along with a 120-kV tube potential, a patient size-adjusted nominal tube current, and the widest beam collimation that allows for reconstruction of 3-mm slices.

If possible, the patient's heart rate during scanning should be <65 beats/min and ideally <60 beats/min for coronary CT angiography (specific values depend on specific scanner characteristics and cardiovascular indication) to provide the best image quality and allow use of lower-dose acquisition modes.

Considerations for noncoronary cardiovascular CT

For some noncoronary cardiovascular CT studies, lower-dose settings can be used and thicker slices reconstructed to achieve acceptable image noise.

Pulmonary vein anatomic mapping CT studies may be best performed with non-ECG-referenced or single heartbeat techniques for patients with atrial fibrillation.

Dose monitoring

CTDIvol [expressed in mGy] and DLP [expressed in mGy-cm] should be recorded for each patient.

Review of sites’ radiation levels and adherence to institutional algorithms for radiation dose optimization should be performed at least twice per year.