Figure 1.

(A) RL, (B) DV, and (C) VD radiographic views of the thorax in a healthy rhesus macaque without significant cardiac disease (control). Each view illustrates the measurements of long (point 1 to point 2) and short (point 3 to point 4) axes of the cardiac silhouette. Regardless of the radiographic view, both axes are aligned with the fourth thoracic vertebrae (T4) in the RL view. Vertebral bodies are counted for each axis dimension, and their sum is the VHS. RL, right lateral; DV, dorsoventral; VD, ventrodorsal; VHS, vertebral heart score.