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INTRODUCTION

KEY POINTS

  • Single-photon emission computerized tomographic myocardial perfusion imaging (MPI) is the most common noninvasive modality used to evaluate patients with known or suspected coronary artery disease (CAD) in the United States.

  • Technetium-99m (Tc-99m) and thallium-201 (Tl-201) distribute in the myocardium in proportion to regional blood flow; hence, the presence of a perfusion defect on imaging signals abnormal myocardial perfusion.

  • Protocols involve rest and/or stress imaging, using physical (e.g., treadmill) or pharmacological (e.g., vasodilator or dobutamine) stress agents, over 1 or 2 days.

  • MPI is believed to account for up to 20% of the total patient radiation exposure from medical imaging in the United States and thus efforts to reduce radiation doses from MPI are important.

  • Advancements in camera technology and post-processing have enabled more time-efficient studies with better image quality and lower administered radiation doses.

  • A normal stress study obviates the need for subsequent rest imaging, thus guidelines now encourage the use of stress-first protocols to reduce radiation exposure, reduce cost, and increase laboratory efficiency.

Single-photon emission computerized tomographic (SPECT) myocardial perfusion imaging (MPI) remains the dominant noninvasive functional imaging perfusion method for the diagnosis, as well as prognosis of epicardial coronary artery disease (CAD). The advent and advances of other methods used for similar purposes (cardiac positron emission tomography [PET], stress echocardiography, coronary computerized tomography [CTA], and cardiac magnetic resonance [CMR]) have all contributed to recent re-examination of traditional MPI protocols to optimize its use.1 This task was facilitated by introduction of high-efficiency cadmium zinc telluride (CZT) nuclear cameras and innovative software. With changes in society and concern of radiation exposure, emphasis has shifted from “one size fits all” to patient-centered imaging with individualized approach to each patient’s unique constellation of reasons and urgency of testing, comorbidities, age, body habitus, physical ability, and results of previous tests and procedures.2 In-depth knowledge of the advantages and disadvantages of available radionuclide tracers and stressors by those who perform stress testing and imaging is paramount. Patient participation in decision making becomes desirable as well.

With an acknowledgment of possibly harmful effects of low radiation doses used at times frequently over an extended period of time due to the chronic nature of CAD, attention has shifted to dose reduction3 and potentially mandatory tracking of all received radiation doses.4

In view of competing noninvasive imaging modalities, cost effectiveness has also been addressed. The length of “traditional” MPI is almost half a day, which poorly compares to on average 1 hour to completion and diagnosis using CTA, stress echocardiography, or PET. Many of the newer imaging protocols therefore address the need for increased throughput and reduced patient radiation exposure for a nuclear cardiology laboratory. This chapter will describe protocols for SPECT MPI for the three primary imaging agents, (1) technetium-99m sestamibi, (2) technetium-99m tetrofosmin, and (3) thallium-201, as well as described suggestions for reducing time and radiation exposure of the procedures.

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