Focused Field of View Calcium Scoring Prior to Coronary CT Angiography

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

1. Facilities: Walter Reed National Military Medical Center

   1. Cardiology Clinic
   2. Cardiovascular Health and Interventional Radiology, Angiography and Recovery \[CVHIR\]
   3. Radiology Department (CT Section)
2. Duration of enrollment: 12 months
3. Budget: no additional budget is needed.

Subject Population

1. 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.
2. 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:

   1. Verbal admission of pregnant status; OR
   2. Positive urine pregnancy test performed within 7 days of CCTA in subjects not previously known to be pregnant.

Eligibility Criteria:
Inclusion Criteria:

1. Consenting adult patients ≥ 50 years of age;
2. 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
3. Scheduled for non-emergent clinically indicated coronary CT angiography

Exclusion Criteria:

1. Prior coronary bypass graft (CABG) surgery
2. Suspicion of acute coronary syndrome (MI or unstable angina)
3. Known complex congenital heart disease
4. 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
5. Atrial fibrillation
6. Abnormal renal function (GFR \< 60 ml/min; Creatinine \> 1.5 mg/dL)
7. Concomitant participation in another clinical trial in which patient is subject to investigation drug or device
8. Pregnancy or unknown pregnancy status
9. Allergy to iodinated contrast agent
10. Contraindications to nitroglycerin
11. Unwilling or unable to give consent
12. Inability to comply with study procedures
13. Prior coronary artery calcium score and/or coronary CT angiogram