The x- and y- axes of a circumferential profile curve are, respectively:

In the context of a circumferential profile curve, the x-axis typically represents segments of the myocardium, while the y-axis indicates the maximum counts detected from a nuclear imaging study. This setup allows for a clear visualization of the perfusion characteristics across different regions of the myocardium. By plotting the data in this manner, healthcare professionals can evaluate areas of reduced blood flow or perfusion abnormalities, which are crucial for diagnosing and assessing various cardiac conditions.

The distribution of counts across the myocardium segments gives valuable insight into the heart's functional status, particularly during stress or rest conditions, and aids in identifying regions with potential ischemia or infarction. Thus, this format effectively communicates the key information needed to assess myocardial perfusion comprehensively.