Which patient is most likely to receive fewer particles during lung perfusion imaging?

In lung perfusion imaging, the distribution of radioactive particles can vary based on cardiac and pulmonary conditions. In the case of a patient with a right-to-left cardiac shunt, there is an abnormal pathway that allows blood to bypass the lungs and enter systemic circulation without being oxygenated. This means that fewer particles would reach the lung vasculature for imaging purposes, as some of the blood that should be going to the lungs instead flows directly into the left side of the heart and then to the remainder of the body.

Patients without such a shunt, such as those with a healthy heart or common respiratory conditions like asthma, would typically demonstrate more normal pulmonary perfusion patterns. In these individuals, the passage of particles through the pulmonary vasculature would be more complete, resulting in greater counts during imaging. Consequently, the presence of a right-to-left shunt directly leads to decreased particle reception in the lungs during the perfusion study, making the patient with this condition the most likely to receive fewer particles.