The imperative to assess physical function among all patients undergoing stress myocardial perfusion imaging

Stress rest myocardial perfusion imaging (MPI) can be performed using either single-photon emission computed tomography (SPECT) or positron emission tomography (PET). However, PET imaging offers important advantages, including higher spatial resolution and shorter imaging protocols due to the higher photon sensitivity of PET scanners and more rapid clearance of PET radiotracers from the background, and the routine use of attenuation correction. In addition, PET-MPI allows for the absolute quantification of myocardial blood flow and assessment of coronary flow reserve. But unlike SPECT-MPI, PET-MPI is not performed in conjunction with exercise testing due to the limitations poised by current PET radiotracers. ⁸²Rubidium, the most commonly used PET-MPI radiotracer, has a half-life of only 76 seconds. Thus, its use mandates that patients be in the PET scanner at the time of stress imaging, performed using vasodilator agents such as adenosine or regadenoson. By using ¹³N-ammonia with its half-life of 9.8 minutes, it is possible to use it in conjunction with exercise testing.1,2 However, exercise PET with ¹³N-ammonia is uncommonly performed because until now, this tracer has required an on-site cyclotron for its production and use. To-date, such on-site cyclotrons have been limited to a very small percentage of clinical imaging centers. …