In a left-to-right cardiac shunt study, the regions of interest are drawn around which structures?

In a left-to-right cardiac shunt study, the primary focus is on assessing the flow of blood from the left side of the heart to the right side, typically resulting from conditions such as atrial septal defects or ventricular septal defects. By drawing regions of interest around the lungs, practitioners can evaluate the distribution and enhancement patterns of the radiotracer in the pulmonary circulation.

When a shunt occurs, more blood flows into the right side of the heart and subsequently into the pulmonary arteries, causing changes in the appearance of the lungs on a nuclear medicine scan. Analyzing the regions of interest around the lungs enables the evaluation of pulmonary over-circulation and the potential consequences of increased blood flow, such as pulmonary edema or altered lung perfusion. The assessment of both or one lung is crucial, as it provides insights into the severity and implications of the shunt on pulmonary function.

In contrast, while other heart structures, such as the right atrium, aorta, or left ventricle, play important roles in cardiac function and may indirectly relate to shunts, they are not the primary areas of interest for determining the effects of a left-to-right shunt. Focusing on the lungs allows for a more direct measurement of the physiological