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Recommendations for reducing radiation exposure in myocardial perfusion imaging

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Introduction

Radionuclide myocardial perfusion imaging (MPI) using single photon emission computed tomography (SPECT) or positron emission tomography (PET) for the detection of ischemia in patients with known or suspected coronary artery disease (CAD) has widespread clinical utilization and has been shown to have high accuracy and incremental prognostic value.1, 2, 3 Amidst the recent publicity regarding the increasing use of all types of ionizing radiation in the United States, patients and medical professionals are scrutinizing the need for diagnostic testing and how radiation exposure can be reduced.4,5 There are three critical questions that physicians must consider and answer with regard to radiation exposure and performing MPI in a particular patient:

  • Is MPI testing appropriate and necessary in this patient?

  • How can the MPI protocol be optimized to give the lowest possible radiation dose while maintaining diagnostic accuracy?

  • How can new technologies be utilized to provide the lowest possible radiation dose while maintaining diagnostic accuracy?

Lowering the radiation dose while maintaining or improving image quality should be considered an improvement in quality of care; the lower the radiation and the higher the image quality, the greater the improvement in the quality of patient care. In general, all MPI studies should be performed in appropriate patients using relatively short-lived radionuclides, and using all possible measures to minimize radiation exposure. Under such circumstances, the benefits of the diagnostic and prognostic information outweigh the risks of radiation exposure.

This document identifies the best practice methods to optimize the benefits of MPI testing by obtaining the highest quality diagnostic images while minimizing radiation exposure. The focus will be on the appropriate selection of patients, the use of protocols that lessen total radiation exposure, and the use of equipment and processing methods that achieve the best image quality at the lowest possible radiation dose.

Section snippets

Appropriate Patient Selection

Diagnostic radionuclide tracers are distributed over the entire body and are not associated with deterministic radiation effects which include skin burns, cataracts, and permanent sterility. They are related directly to the total dose received, have a latency of weeks to months, and there is a threshold below which effects will not occur. Theoretically, radionuclide tracers add a very small risk due to the stochastic effects of radiation, which are based on probability of chromosomal damage,

Protocols, Radiotracers, and Imaging Systems

SPECT and PET MPI can be performed using several different protocols and radionuclide tracers.12, 13, 14 Patient radiation exposure depends on the type and dose of injected radiotracer. Table 2 lists the effective dose estimates using tissue dose coefficients, E1, or effective dose coefficients, E2, for standard myocardial perfusion imaging protocols. Administered radiation dose may vary considerably based on patient weight and characteristics of the imaging system. There are a number of

Technology

Once the appropriate patient, radiotracer, and protocol have been selected, technological considerations can further reduce radiation exposure. The various hardware and software options are discussed below, and the recommendations that can be made based on the existing data are listed in Table 3.

Summary

Figure 1 illustrates the patient flow resulting from the above discussion. It is consistent with the concept of lowering the radiation dose while maintaining or improving image quality which should be considered an improvement in quality of care. The lower the radiation and the higher the image quality the greater the improvement in the quality of patient care. This approach combines the radiation reduction factors, which if implemented correctly, will provide the highest quality MPI studies at

Acknowledgments

Dr. Nichols serves as a consultant for IEAE and receives royalties from Syntermed, Inc. The authors have no conflicts of interest to disclose except as noted above.

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