Anatomical References to Evaluate Thoracic Aorta Calcium by Computed Tomography

Thoracic aortic calcium (TAC) has received some interest in recent studies as an important subclinical marker of atherosclerosis. Besides that, using computed tomography (CT) scans performed with cardiac or chest protocols, ECG-gated, or non-gated, TAC can be easily evaluated with no addition in radiation dose. This review discusses the particularities of the aortic wall calcium formation, as well as the differences between the aortic segments and summarizes the current status of TAC evaluation, mainly concerning the anatomical references used in the studies.

The studies have evaluated TAC considering different anatomical references. It was identified two different study groups. In the first one, researchers have analyzed the aorta as the sum of calcium in the ascending aorta (ATAC), aortic arch (AAC), and descending thoracic aorta (DTAC). The second group has used cardiac CT scans to assess TAC; therefore, they did not include AAC; however, the aortic root calcium (ARC) was added in the analysis. So, caution is advisable when interpreting and comparing studies that used different TAC anatomical references. The broad methodological variability, in addition to the variations in the population characteristics of the studies on TAC, may be in part contributing to the differences between results of different studies. Currently TAC does not have a role in clinical decisions, so it is necessary to create a standard protocol for the aortic calcium research as well as exists for the coronary artery calcium evaluation.