Original article
Occupational radiation dose associated with Rb-82 myocardial perfusion positron emission tomography imaging

https://doi.org/10.1016/j.nuclcard.2006.03.001Get rights and content

Background

We determined staff radiation dose during rest and stress rubidium 82 myocardial perfusion positron emission tomography (PET) imaging.

Methods and Results

Patients received 1587 ± 163 MBq (42.9 ± 4.4 mCi) Rb-82 during rest or pharmacologic stress. A pressurized ion chamber was used to monitor radiation exposure in 50 examinations. For comparison, staff exposure during pharmacologic stress in 20 other patients receiving 1204 ± 55.5 MBq (32.54 ± 1.5 mCi) technetium 99m 2-methoxy isobutyl isonitrile (MIBI) was measured. For Rb-82 infusion and PET acquisition, the mean dose was 0.45 ± 0.25 μSv (0.045 ± 0.025 mrem). Exposure for routine stress testing at variable distances from the patient was equivalent to background. Similar exposure for pharmacologic stress testing through 7 minutes after injection of Tc-99m MIBI at variable distances was 1.075 ± 0.32 μSv (0.108 ± 0.03 mrem). However, exposure for stress tests starting 7 minutes after Rb-82 infusion at 0.5 m was estimated at 0.4 μSv (0.04 mrem). To determine the potential radiation dose for those responding to a medical emergency or otherwise in close proximity to a patient, we measured the mean cumulative dose at 0.5 m from 0 to 7 minutes of Rb-82 infusion, which resulted in 19.1 ± 5.8 μSv (1.9 ± 0.58 mrem).

Conclusions

Radiation doses for all tasks during routine Rb-82 stress-rest PET are lower than measured Tc-99m MIBI values. However, the radiation dose in close proximity to the patient during or immediately after Rb-82 infusion can be considerably higher, underscoring the need for strict attention to source distance and contact times.

Section snippets

Materials and methods

This study was reviewed and approved by our hospital’s institutional review board. For the Rb-82 measurements, we obtained 50 rest or stress scan measurements in 41 patients undergoing clinically indicated stress-rest myocardial perfusion scans. Similar Rb-82 doses were administered to all patients. The Rb-82–associated exposure measurements were carried out in the shielded PET–computed tomography (CT) scan room during the use of a GE Discovery ST PET-CT system with a 16-slice multidetector CT

Background Radiation Exposure in PET Room

Room background radiation ranged from 0.02 to 0.07 μSv/h (0.002-0.007 mrem/h). At 0.5 m from the Sr-82/Rb-82 generator, the dose rate approximated 0.3 to 0.4 μSv/h (0.03-0.040 mrem/h). In 8 cases the injection tubing registered a mean of 20.3 μSv/h (2.03 mrem/h) at 7.5 minutes after Rb-82 injection.

Rb-82 Exposure During Generator Change

Exposure was measured at one generator change, which involved removing the old generator after 4 weeks of use, purging of tubing lines, placement of the new generator into the cabinet, and running a

Discussion

The International Commission on Radiation Protection (ICRP) recommends an occupational effective dose constraint of 20 mSv (2000 mrem) per year, averaged over a period of 5 years.12 In contrast, in the United States the annual maximum permissible effective dose for occupational radiation workers is set at 50 mSv (5000 mrem) per year.13 At our institution, As Low As Reasonably Achievable (ALARA) violation notices are distributed and investigated when any worker receives more than 10% (ALARA I)

Acknowledgment

We thank the following technical and exercise physiology staff of the Brigham and Women’s Hospital PET-CT Laboratory, who graciously facilitated this study: Erica Calcagno, MS, Sharon Crugnale, MS, Christine Edwards, CNMT, Patricia Farago, CNMT, Jolene Meserve, CNMT, Scott Thomas, CNMT, and David Yang, MS.

Dr Castronovo has indicated he has no financial conflicts of interest. Dr Dorbala is on the Speakers’ Bureau of Bracco Diagnostics. Dr Di Carli is on the Speakers’ Bureau and is a grant

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AR Schleipman is a recipient of a research grant funded by the Society of Nuclear Medicine Technologist Section Professional Development and Education Fund (SNM-PDEF), which partially supported this work.

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