Contrast agent volume in coronary computer tomography angiography-where are the limits?

Quant Imaging Med Surg 2021 | http://dx.doi. org/10.21037/qims-21-488 Coronary artery disease (CAD) is still a major public health problem, remaining the most common cause of death and disability globally and being associated with relevant costs for our health care system (1,2). It can present in chronic or stable forms, currently named chronic coronary syndromes but also in acute forms ranging from unstable angina to myocardial infarction with cardiogenic shock or sudden cardiac death. The work-up of patients with known or suspected CAD is complex and usually involves a stepwise approach that includes clinical and demographic data, non-invasive tests and if required invasive coronary angiography (3). Recent data have revealed a lower pre-test probability in patients with CAD than previously anticipated (4). In parallel, a paradigm shift occurred in the evaluation of patients with suspected CAD, with the focus moving to non-invasive imaging techniques. Currently, the clinician can choose between imaging tests that aim at identifying myocardial ischemia such as stress-echocardiography, stress cardiac magnetic resonance imaging or myocardial scintigraphy and direct non-invasive anatomical imaging of the coronary tree using coronary computer tomography angiography (CCTA) (5). In the last decades, an abundance of studies was published, which cemented the central role of CCTA in the diagnostic approach of patients with known and suspected CAD. In this regard, CCTA was shown to provide (I) excellent negative predictive value and very good specificity for identifying relevant CAD, (II) in depth evaluation of the various stages and severity of the coronary atherosclerotic process, (III) functional information related to the hemodynamic significance of the coronary stenosis using FFRCT and, most importantly, (IV) definite improvement of clinical outcomes (6). Clinicians need however, to be aware of two relevant risks associated with a CCTA examination, which are (I) radiation exposure and (II) complications related to the administration of iodine contrast agent. Regarding radiation exposure, technological advancements within the last decades allowed for a significant reduction of the radiation exposure for the patients. Thus, the radiation exposure normally seen with spiral acquisitions (9-22 mSv) can be significantly reduced using prospective step and shoot protocols (2-4 mSv) and further minimized to <1 mSv by employing high-pitch spiral protocols using modern dual source machines in selected patients (7-9). Studies have proven the diagnostic feasibility of the high-pitch spiral technology and, although this type of acquisition cannot be applied in all scenarios, it already entered the clinical routine (10). The exceptionally low radiation exposure opens the door for performing longitudinal CCTA studies and thus for providing important information related to the evolution of the atherosclerotic process and its response to specific lipid-lowering or anti-inflammatory therapies. The administration of contrast agent, on the other hand, is related to possible allergic reactions, hyperthyroidism Letter to the Editor