Focused Field of View Calcium Scoring Prior to Coronary CT Angiography (FOCUS-CCTA)

Coronary computed tomography angiography (CCTA) is a frequently performed test for the diagnosis and/or exclusion of coronary artery disease (CAD) in appropriately selected patients. The performance of non-contrast computed tomography for the detection and quantification of coronary calcification is typically performed prior to CCTA in an effort to identify significant calcification which may influence subsequent data acquisition during the CCTA. However, performance of calcium scoring adds significant radiation and most coronary calcification is proximal in its location, potentially visualized using a focused non-contrast scan. The purpose of this study is to prospectively compare the usefulness of a modified non-contrast CT, using a significantly shorter scan length and lower radiation parameters, as compared to standard coronary artery calcium scanning for the detection of coronary calcification that may influence subsequent CCTA performance.

Prior to undergoing CCTA, non-contrast CT scanning of the entire heart is usually performed in adults over 50-years of age in order to assess for the presence and severity of coronary artery calcium. By providing a modified CT scan with a reduced length the same data can be obtained by the imager to ensure a high quality scan while decreasing the patient's overall radiation exposure. Our objectives and specific aims to validate our hypothesis include: To assess the impact on CCTA image quality using modified calcium score approach To determine the rate of changes in the coronary CT angiography acquisition parameters after evaluation of the modified versus standard calcium scoring scout series. Significant changes in CCTA acquisition include any of the following as compared to recommended CCTA parameters prior to scout CT performance: a change (increase or decrease) in tube current (mA) by 50, any change in tube potential (kV), change to/from retrospectively-gated CCTA, any change in padding (acquisition window), or changing to/from a high definition CT scan acquisition. To assess the difference in patient estimated effective radiation exposure (mSv) between the modified versus standard calcium scoring techniques. To assess the difference in patient estimated effective radiation exposure (mSv) of the entire CCTA study (plus calcium scoring) between groups. Study Design Prospective, randomized single-center cohort study. Anticipated Requirements Facilities: Walter Reed National Military Medical Center Cardiology Clinic Cardiovascular Health and Interventional Radiology, Angiography and Recovery [CVHIR] Radiology Department (CT Section) Duration of enrollment: 12 months Budget: no additional budget is needed. Subject Population One hundred seventy-five (175) male and female adult subjects (military health beneficiaries age greater than 50 years) who are clinically referred for CCTA will be eligible for participation. The Walter Reed National Military Medical Center Cardiology Department and Radiology Departments perform multiple clinically appropriate and indicated coronary CTA studies weekly (approximately 8-12), which will allow for ease of subject recruitment. Although there are other open studies using CCTA in our department there is not a lot of overlap in their requirements and should not prohibit enrollment in our study. This study will enroll both men and women of all ethnic origins aged ≥ 50 years. All subjects will consent for themselves. All patients' participation in this research and subsequent contribution to our medical knowledge notwithstanding, no intent to benefit patients from enrollment is implied or offered. Pregnant women will be excluded from enrollment based on: Verbal admission of pregnant status; OR Positive urine pregnancy test performed within 7 days of CCTA in subjects not previously known to be pregnant.

In patients randomized to undergo the modified non-contrast CT scan to assess coronary calcification burden, this study will be performed by a radiologist and cardiologist as follows: axial acquisition obtained at 70% of the R-R interval using the following parameters: rotation time 0.35 sec; collimation of 64 x 0.625mm; detector coverage of 20.0 mm; axial thickness 2.5; tube voltage 80kV and tube current 250mA. The scan length will be from 1 cm below the carina to the level beneath the proximal coronary vessels defined as the greatest diameter of the apex of the right atrium.

In patients randomized to standard coronary artery calcium scoring, this scan will be performed in usual axial fashion obtained at 70% of the R-R interval using the following parameters: rotation time 0.35 sec; collimation of 64 x 0.625mm; detector coverage of 20.0 mm; axial thickness 2.5; tube voltage, 120 kV and tube current 250mA. The scan length, in accordance with current protocol, will be from 1 cm below the carina through the diaphragms.

The measurement of quality in comparison of the modified versus non-modified CCTA using a qualitative (four point scale). = Nondiagnostic: Impaired image quality that precluded appropriate evaluation of the coronary arteries due to severe motion artifacts, extensive blooming artifact, severe image noise, or insufficient contrast. = Adequate: Reduced image quality because of artifacts due to motion, image noise or low contrast attenuation, but sufficient to rule-out significant stenosis. = Good: Presence of artifacts caused by motion, image noise, coronary calcifications or low contrast, but fully preserved ability to assess the presence of luminal stenosis as well as the presence of calcified and non-calcified coronary atherosclerotic plaque. = Excellent: Complete absence of motion artifacts, strong attenuation of vessel lumen and clear delineation of vessel walls, with the ability to assess stenosis and plaque characteristics.

Following completion of data acquisition (i.e. CT scans) for all patients (last patient scan was 2/26/18), each outcome measure was then assessed (this process spanned approximately 3 months from March to June 2018).

The measurement of quality in comparison of the modified versus non-modified CCTA using a quantitative score (CCTA signal, noise, signal to noise ratio): image signal and noise obtained during scan analysis by placing a circular region of interest (1 cm in diameter) within the proximal ascending aorta and there measuring Hounsfield Units (HU) which is the CCTA "signal" and standard deviation of the HU within that same region (which is the "noise"), the ratio of these signal/noise is also captured by this method.

Following completion of data acquisition (i.e. CT scans) for all patients (last patient scan was 2/26/18), each outcome measure was then assessed (this process spanned approximately 3 months from March to June 2018).

Any changes in the cardiac CT after evaluation of the modified or standard calcium scoring in a change in milliamps by 50.

Following completion of data acquisition (i.e. CT scans) for all patients (last patient scan was 2/26/18), each outcome measure was then assessed (this process spanned approximately 3 months from March to June 2018).

Any changes in the cardiac CT after evaluation of the modified or standard calcium scoring (i.e. increasing or decreasing the tube potential)

Following completion of data acquisition (i.e. CT scans) for all patients (last patient scan was 2/26/18), each outcome measure was then assessed (this process spanned approximately 3 months from March to June 2018).

Any use of of the "high definition" scanning parameter after evaluation of the calcium burden by modified or standard calcium scoring.

Following completion of data acquisition (i.e. CT scans) for all patients (last patient scan was 2/26/18), each outcome measure was then assessed (this process spanned approximately 3 months from March to June 2018).

Any changes in the cardiac CT after evaluation of the modified or standard calcium scoring in any changes in padding (milliseconds).

Following completion of data acquisition (i.e. CT scans) for all patients (last patient scan was 2/26/18), each outcome measure was then assessed (this process spanned approximately 3 months from March to June 2018).

The measurement of radiation exposure as DLP (measured in mSv/mGycm) in comparison of the modified versus standard calcium scoring.

Following completion of data acquisition (i.e. CT scans) for all patients (last patient scan was 2/26/18), each outcome measure was then assessed (this process spanned approximately 3 months from March to June 2018).

The measurement of radiation exposure difference measured as DLP/milli-sieverts of the entire CCTA study on the modified versus standard calcium scoring.

Following completion of data acquisition (i.e. CT scans) for all patients (last patient scan was 2/26/18), each outcome measure was then assessed (this process spanned approximately 3 months from March to June 2018).

Number of patients whose coronary CTA scan was canceled by the imaging provider due to extreme levels of calcium noted during the modified or standard calcium scoring scan.

Following completion of data acquisition (i.e. CT scans) for all patients (last patient scan was 2/26/18), each outcome measure was then assessed (this process spanned approximately 3 months from March to June 2018).

Inclusion Criteria: Consenting adult patients ≥ 50 years of age; Suspected but without known prior history of CAD. Prior CAD is defined as a history of myocardial infarction, coronary revascularization or ≥ 50% coronary lumen stenosis on prior coronary angiography Scheduled for non-emergent clinically indicated coronary CT angiography Exclusion Criteria: Prior coronary bypass graft (CABG) surgery Suspicion of acute coronary syndrome (MI or unstable angina) Known complex congenital heart disease Evidence of ongoing or active clinical instability, including chest pain (sudden onset); cardiogenic shock; unstable blood pressure with systolic blood pressure < 90 mmHg; and severe congestive heart failure (NYHA class III or IV); or acute pulmonary embolism Atrial fibrillation Abnormal renal function (GFR < 60 ml/min; Creatinine > 1.5 mg/dL) Concomitant participation in another clinical trial in which patient is subject to investigation drug or device Pregnancy or unknown pregnancy status Allergy to iodinated contrast agent Contraindications to nitroglycerin Unwilling or unable to give consent Inability to comply with study procedures Prior coronary artery calcium score and/or coronary CT angiogram

Crimm HA, Fergestrom NM, Dye C, Philip C, Nguyen BT, Villines TC. Focused, low tube potential, coronary calcium assessment prior to coronary CT angiography: A prospective, randomized clinical trial. J Cardiovasc Comput Tomogr. 2021 May-Jun;15(3):240-245. doi: 10.1016/j.jcct.2020.08.011. Epub 2020 Aug 22.