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

BACKGROUND: We determined staff radiation dose during rest and stress rubidium 82 myocardial perfusion positron emission tomography (PET) imaging. METHODS AND RESULTS: Patients received 1,587 +/- 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 1,204 +/- 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 microSv (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 microSv (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 microSv (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 microSv (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.

Lowering the thyroid dose in screening examinations of the cervical spine.

The first objective of this study was to test the hypothesis that a lower-dose (14.1 mGy thyroid dose) protocol for helical computed tomography (CT) of the entire cervical spine demonstrates equivalent technical adequacy and diagnostic accuracy as the standard-dose protocol (26.0 mGy thyroid dose) used at our institution. The second objective was to estimate the excess thyroid cancer mortality for three cervical spine screening protocols. Eight patients underwent two helical CT acquisitions of the entire cervical spine (standard and lower dose); from these acquisitions, a database of 128 randomized images (64 standard dose and 64 lower dose) was constructed. Three radiologists evaluated each of the 128 images for technical adequacy and, if the image was technically adequate, diagnostic accuracy. Historical data of excess thyroid cancer mortality stratified by age and sex were used to estimate the impact of lowering the thyroid dose in cervical spine screening. Estimates used a linear extrapolation of mortality data. The lower-dose protocol for helical CT of the entire cervical spine demonstrates equivalent technical adequacy and diagnostic accuracy as the standard protocol. The excess thyroid cancer mortality is a function of patient age and sex; for 25-year-old men, the excess mortality per 100,000 patients is 96.7 (standard-dose CT), 52.4 (lower-dose CT), and 6.7 (radiographs alone, 1.8 mGy thyroid dose). The equivalent technical adequacy and diagnostic accuracy of a lower-dose protocol for helical CT of the entire cervical spine support its implementation in routine screening. The excess thyroid mortality emphasizes the need to maintain an open dialogue with our referring clinicians with respect to the mechanism of injury, clinical findings, and radiation risks.

Radiation-absorbed dose from 201Tl-thallous chloride.

UNLABELLED: Revised radiation dosimetry estimates for 201Tl-thallous chloride have been developed using new data specifically acquired to address the issue of testicular uptake of this agent and through reevaluation of extant data for biodistribution in other organs. METHODS: Quantitative testicular scintigraphy data of sequestered testes (body-background shielded) were obtained from 28 patients (56 studies) injected with 201Tl-thallous chloride at peak exercise. Previously published data for 15 patients injected at maximal exercise were reanalyzed to obtain updated biodistribution parameters for designated organs. Radiation dose was calculated according to the MIRD schema. Radiation dose to testes as a function of age was determined. Comparisons are made between organ dose estimates derived in this study and those previously published. The dose contributions of possible contaminants (200Tl, 202Tl, 203Pb) have been included. Estimates are provided of the dose component from these contaminants if injected at the time of the maximum recommended 5-d shelf life (as opposed to at the designated calibration time). RESULTS: The radiation dose per unit administered activity to adult testes calculated in this study of 0.21 mGy/MBq (0.77 rad/mCi) is approximately a factor of 2 less than the value of 0.45 mGy/MBq (1.7 rad/mCi) previously accepted. The revised dose estimates for other organs show less variation from published values. The effective dose determined in this work is approximately 0.16 mSv/MBq (0.60 rem/mCi). Under the assumption of similar biokinetics as for the adult, the testes dose for children increases significantly as age decreases with a value of 7.5 mGy/MBq (28 rad/mCi) for a newborn. Contributions from radiocontaminants that may be encountered in the preparation of 201Tl-thallous chloride are shown to range from a fraction of a percent up to approximately 20% of the total dose for some organs, with the higher values arising from the long half-life contaminant 202Tl after a 5-d shelf life. CONCLUSION: It is recommended that the dose values determined in this study be used when estimating the radiation dose to the adult testes from intravenous administration of 201Tl-thallous chloride. The potential for increased radiation dose per administered activity to the testes at younger ages should be evaluated before performing procedures on children. The presence of radiocontaminants in the product should be considered when estimating radiation dose and may add a significant contribution to dose dependent on the specific radionuclide and concentration at the time of administration.

A fluoroscopic credentialing/safety program at a large research hospital.

The Brigham and Women's Hospital is an approximately 700 bed broad-scope licensed facility with a vigorous fluoroscopy service. Concomitant with this service is an equally robust quality management program to safeguard both patient and personnel from excessive radiation doses. The FDA, in an attempt to avoid serious skin injury for certain fluoroscopically guided procedures, issued a Public Health Advisory in 1994. Four years later the institutional Radiation Safety Committee voted to expand an existing fluoroscopic safety course to include a more formal credentialing/safety requirement. The specific parameters associated with this program follow.

Radiation disaster response: preparation and simulation experience at an academic medical center.

OBJECTIVES: A mass casualty disaster drill involving the simulated explosion of a radiation dispersal device (dirty bomb) was performed with the participation of multiple hospitals, emergency responders, and governmental agencies. The exercise was designed to stress trauma service capacities, communications, safety, and logistic functions. We report our experience and critique of the planning, training, and execution of the exercise, with special attention to the integrated response of the Departments of Nuclear Medicine, Health Physics, and Emergency Medicine. METHODS: The Health Physics Department presented multiple training sessions to the Emergency Medicine Department, Operating Room, and ancillary staff; reviewing basics of radiation biology and risk, protection standards, and detection of radiocontamination. Competency-based simulations using Geiger-Müller detectors and sealed sources were performed. Two nuclear medicine technologists played an important role in radiation discrimination-that is, assessment of radioactive contamination with survey meters and radionuclide identification based on gamma-spectroscopy of wipe smears from patients' clothing, skin, and orifices. Three Health Physics personnel and one senior Nuclear Medicine staff member were designated the radiation control officers for assigned teams triaging or treating patients. Patients were triaged and, when indicated, decontaminated. RESULTS: Within a 2-h period, 21 simulated victims arrived at our institution's Emergency Room. Of these, 11 were randomized as noncontaminated, with 10 as contaminated. Decontamination procedures were implemented in a hazardous materials (HAZMAT) decontamination trailer and, for the 5 patients with simulated serious injuries, in a designated trauma room. A full debriefing took place at the conclusion of the exercise. Staff largely complied with appropriate radiation protection protocols, although decontamination areas were not effectively controlled. The encountered limitations included significant lapses in communications and logistics, lack of coordination in the flow of patients through the HAZMAT trailer, insufficient staff to treat acute patients in a radiation control area, additional personnel needed for transport, and insufficient radiation safety personnel to control each decontamination room. CONCLUSION: Nuclear Medicine personnel are particularly well qualified to assist Health Physics and Emergency Medicine personnel in the preparation for, and management of, mass casualty radiation emergencies. Simulation exercises, though resource intensive, are essential to an institution's determination of response capability, performance, and coordination with outside agencies.

A Fluoroscopic Credentialing/Safety Program at a Large Research Hospital.

The Brigham and Women's Hospital is an ~700 bed broad-scope licensed facility with a vigorous fluoroscopy service. Concomitant with this service is an equally robust quality management program to safeguard both patient and personnel from excessive radiation doses. The FDA, in an attempt to avoid serious skin injury for certain fluoroscopically guided procedures, issued a Public Health Advisory in 1994. Four years later the institutional Radiation Safety Committee voted to expand an existing fluoroscopic safety course to include a more formal credentialing/safety requirement. The specific parameters associated with this program follow.