Approaches to Reducing Radiation Dose from Radionuclide Myocardial Perfusion Imaging

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FIGURE 1.
Increasing radiation burden in United States and contributions from medical imaging. Collective dose from medical imaging increased 6-fold in 2006 compared with early 1980s. (Reprinted with permission of (2).)
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FIGURE 2.
Practical ways to implement reduced-radiation-dose MPI program.
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FIGURE 3.
Patient-centered protocols for low-radiation-dose MPI: traditional SPECT (orange), traditional SPECT with novel software (purple), and novel SPECT scanners (green). Most MPI procedures that use novel protocols or novel technologies provide <9-mSv radiation dose from rest–stress ^99mTc protocols. To achieve 50% of laboratory volume with <9-mSv dose, practices can implement several of the above options into their practice. LD = low dose; HD = high dose; 1 mCi = 37 MBq.

TABLE 1

Five Things Physicians and Patients Need to Know (15,16)

Source	Point
SNMMI	Do not perform routine annual stress testing after coronary artery revascularization.
ASNC	Do not perform stress cardiac imaging or coronary angiography in patients without cardiac symptoms unless high-risk markers are present.
	Do not perform cardiac imaging in patients who are at low risk.
	Do not perform radionuclide imaging as part of routine follow-up in asymptomatic patients.
	Do not perform cardiac imaging as preoperative assessment in patients scheduled to undergo low- or intermediate-risk noncardiac surgery.
	Use methods to reduce radiation exposure in cardiac imaging whenever possible, including not performing such tests when the benefits will likely be limited.

TABLE 2

Steps to Create Protocol Plan for MPI

Step	Description
1	Review electronic medical records to define clinical question.
2	Check for recently performed cardiac evaluations to avoid duplicate testing and layered testing for similar clinical symptoms.
3	If clinical question is not clear or if test ordered is not the most appropriate test, discuss with referring physician for clarification.
4	Plan appropriate stress technique.
5	Plan appropriate imaging technique.

TABLE 3

Estimation of Effective Radiation Dose from Various Myocardial Perfusion Radiotracers (13)

Recommended MPI radiotracer doses for conventional scanners are 8–12 mCi of ^99mTc-sestamibi for rest imaging and 24–36 mCi for stress imaging, 40–60 mCi of ⁸²Rb for 2D imaging and 20 mCi for 3D imaging (58), 20 mCi of ¹³N-ammonia for 2D imaging and 10 mCi for 3D imaging (58), and 2.5–4 mCi for ²⁰¹Tl imaging (59) (1 mCi = 37 MBq). New estimates of ⁸²Rb dose are significantly lower (0.00126 mSv/MBq) (60). Full-dose PET radiotracer is used for 2D imaging and half-dose for 3D imaging; typically, equal dose of radiotracer is administered for rest and for stress PET MPI. Average activities are listed. Estimated dose is effective dose multiplied by administered activity. Dose is calculated for rest and stress scans separately, and if attenuation correction is used, 0.3–0.7 mSv is added for CT and 0.3 mSv for radionuclide transmission scanning (13).

TABLE 4

Radiation Dose from Low-Dose Protocols for Novel SPECT Scanners

↵* Data are megabecquerels followed by millicuries in parentheses (range or mean).
LD = low dose; HD = high dose; BMI = body mass index (kg/m²; range, mean ± SD, or upper limit); NA = not applicable.
Variable scan times were used for count-based acquisition. The scanner was a Discovery NM/CT 570c (GE Healthcare) (62), D-SPECT (Spectrum Dynamics) (48), or Discovery NM530c (GE Healthcare) (24,51,52,61).