Ultra-low-dose CACS in a Large Population

Study Overview
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Brief Summary
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Radiation exposure to patients from CT for CAC scoring has steadily decreased in recent years. This is mainly achieved through lowering tube currents alongside with the introduction of iterative reconstruction algorithms which allow compensating for increased image noise. However, the greatest radiation dose reduction can be obtained by reducing peak tube voltage. Yet lowering peak tube voltage remains challenging because tissue attenuation is closely related to photon energy, thus rendering the established thresholds for calculating CAC scores (i.e. Agatston scores) incomparable if peak tube voltages other than the standard 120 kilovolt peak (kVp) are applied. The investigators have developed novel tube-adapted thresholds for CAC scoring by CT at 80 kVp and 70-kVp tube voltage and have shown that these novel thresholds are valid, yielding results closely comparable to the standard 120-kVp protocol. The present study aims to optimize application of such low-dose scans in a general population through assessment of the impact of physiological patient parameters on image parameters such as image noise which per se may impact the accuracy and feasibility of ultra-low-dose CAC scoring with reduced tube voltage. Furthermore, the prognostic performance of such low-dose CAC scoring will be elucidated.

Official Title
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Ultra-low-dose Coronary Artery Calcium Scoring: Evaluation of Prognostic Performance and Impact of Physiological Factors on Quantification in a Large Population

Conditions
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Coronary Artery Disease

Intervention / Treatment
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* Diagnostic Test: Ultra low-dose CTAC


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patients referred for a non-contrast enhanced CT scan for CAC scoring Male and Female subjects ≥18 years of age, Written informed consent Exclusion Criteria: Pregnancy or breast-feeding CACS of 0 after inclusion of 50 patients with CACS 0 (as assessed visually after the first CT scan, prior to performing the 3 additional study scans) History of coronary artery stenting, coronary artery bypass grafting, of implantation of cardiac devices (e.g. valve prosthesis, pacemaker, implantable cardioverter defibrillator etc.) Enrolment of the investigator, his/her family members, employees and other dependent persons

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Sequential Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Standard and ultra-low-dose CAC scoring<br> | Diagnostic Test: Ultra low-dose CTAC<br>* All patients undergo two non-contrast enhanced CT scans with standard dose (i.e. 120 kVp), one with 80 kVp and one with 70 kVp.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Impact of BMI on CAC scores derived from low-dose versus standard-dose CT | Assessment of deviation of CAC scores derived from low-dose CT versus standard-dose CT (i.e. standard of reference) by calculating bias and Bland-Altmann limits of agreement as well as intraclass correlation in different subgroups of patients, stratified by body mass index. | 2 years | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Prognostic value of CAC scores derived from CT scans with varying tube voltages | Assessment of sensitivity and specificity CAC scores derived from low-dose CT versus standard-dose CT (i.e. standard of reference) to predict future cardiovascular events (i.e. myocardial infarction, revascularisation, death) over a short to mid-term follow-up period (i.e. 2 years). | 2 years |