Personalization of CM Injection Protocols in Coronary Computed Tomographic Angiography

Cardiac computed tomography (CCT) is one of the standard non-invasive imaging techniques allowing imaging of the heart and coronary arteries with a high temporal and spatial resolution. The high sensitivity and negative predictive value (NPV) of coronary CT angiography (CCTA) make it a valuable tool in the assessment of coronary artery disease (CAD) in patients with low to intermediate risk for CAD, especially to rule out CAD. This risk stratification can be done with help of multiple different risk-calculators (e.g. the updated Diamond-Forrester model by Genders et al. 2012). These calculators take different variables into account, e.g. advanced age, gender, blood pressure, diabetes mellitus (DM), lipid profile and smoking. The aim of CCTA is a high diagnostic accuracy, which depends on both optimal intravascular enhancement (in Hounsfield Units; minimal 325 HU) and contrast-to-noise ratio (CNR). Optimal intravascular enhancement and CNR depend on different factors such as scan technique (e.g. tube voltage, tube potential), parameters of the administered contrast material (CM) and patient related factors (e.g. cardiac output (CO), body weight (BW)). Patients with cardiac diseases often have multiple risk factors for developing contrast induced nephropathy (CIN), e.g. diabetes mellitus, advanced age, hypertension and chronic kidney disease. Although the relationship between CTA and CIN has recently come to discussion (AMACING trial; Nijssen et al. 2017), it is still desirable to minimise the CM volume used in these patients. One method to reduce the CM volume is to personalise the injection protocols. The personalisation of injection protocols to the individual patient is gaining more attention in the field of CT imaging. The goal is to individualise the injection protocols to a level, where the patient only receives the minimal amount of CM needed to acquire a diagnostic scan, while maintaining a diagnostic image quality. Many techniques are available and have been studied, e.g. adjustment of CM volume to scan protocol, CO, lean body weight (LBW) and BW. However, no data is available on which of these is the most beneficial method for the personalisation of CM injection protocols. Therefore, the aim of this study is to assess the performance of three different personalized injection protocols (based on CO, LBW and BW) in CCTA with regard to image quality in comparison to previously used protocols in our department. We hypothesize that the personalized injection protocols will be non-inferior, provide a homogenous coronary enhancement (less non-diagnostic scans) in patients, and will account for a reduction of CM volume in our department in comparison to the previously used protocols.