Lost workdays due to employee injuries were reduced 96% after Methodist Rehabilitation Center installed ceiling lifts to transfer patients. Credit: Methodist Rehabilitation Center Mississippi,U.S. Radiation Safety Technician at Mount Sinai Hospital checks for contamination after inpatient therapy procedure.

Recently introduced high-efficiency SPECT cameras have demonstrated the ability to reduce radiation exposure to patients undergoing myocardial perfusion imaging studies, especially when combined with stress-only imaging protocols. To date there have been no relevant studies examining the reduced occupational radiation exposure to medical staff. We sought to determine whether changes in stress myocardial perfusion imaging protocols and camera technology can reduce the occupational radiation exposure to the staff of a nuclear cardiology laboratory. Methods: Monthly radiation dosimeter readings from 4 nuclear technologists, 4 nurses, and 2 administrative employees were analyzed from two 12-mo periods: October 2007-September 2008 (period 1), before the use of high-efficiency SPECT, and October 2010-September 2011 (period 2), after high-efficiency SPECT was introduced. The average monthly dose equivalent in millirems (1 mrem 5 0.01 mSv) was recorded from personal dosimeters worn on laboratory coats. The total activity of 99m Tc used per month, mean 99m Tc administered activity per patient, average number of patients per month, patient time spent in the laboratory, and proportion of stress-only studies were determined. Results: There were 3,539 patients in period 1 and 3,898 in period 2. An approximately 40% reduction in the dose equivalent across all staff members occurred during this time (216.9 and 216.2 mrem for nuclear technologists and nurses, respectively; P , 0.0001). During period 2, the total activity of 99m Tc used per month decreased (10,746 vs. 7,174 mCi [1 mCi 5 37 MBq], P , 0.0001), as did the mean 99m Tc administered activity per patient (36.5 vs. 23.8 mCi, P , 0.0001). The percentage of patients having stress-only imaging increased (35% vs. 56%, P , 0.0001), and the total patient time spent in the laboratory decreased. Radiation dose equivalent levels were reduced in period 2 to 1%-7% of the allowed annual occupational dose equivalent. The combination of the use of high-efficiency SPECT technology and stress-only protocols resulted in a 34.7% reduction in mean total 99m Tc administered activity between time periods, with camera technology being responsible for 39.2% of the reduction and stress-only protocols for 60.8%. Conclusion: A combination of high-efficiency SPECT technology and selective use of stress-only protocols significantly reduces the occupational radiation dose equivalent to the staff of a nuclear cardiology laboratory.Key Words: radiation exposure; myocardial perfusion imaging; high-efficiency SPECT; stress-only imaging Radi ation exposure to patients from diagnostic imaging has recently been a prominent topic in the cardiac imaging literature (1), and myocardial perfusion imaging (MPI) has been suggested as one of the larger contributors to a patient's cumulative radiation exposure (2). Much recent effort has been directed toward reducing exposure to the patient (3); however, little attention has been paid to exposure of the medical staff to radiation. There is scant literature on medi...

This paper summarizes about 9 years of effort by Mount Sinai to successfully migrate completely from radioactive irradiators to x-ray irradiators without compromising patient care or research studies. All the effort by Mount Sinai to permanently remove the risk of malicious use of radioactive materials as Radiological Dispersal Device or dirty bomb is reviewed. Due to the unique characteristics of the cesium chloride (137CsCl) used in irradiators, it is especially susceptible to be used as a dirty bombs. Mount Sinai originally had four of such irradiators. To reduce and eventually remove the risk of malicious use of radioactive materials, Mount Sinai in New York City has taken several steps. One of such measures was to harden the radioactive irradiators to make the radioactive materials harder to be stolen for malicious purposes. By increasing the delay time, the local law enforcement agency (LLEA) will have more time to stop the intruder. Another measure taken was to implement enhanced security in facilities having radioactive materials. We collaborated with the National Nuclear Security Administration and used state-of-the-art security equipment such as Biometric Access Control and 24/7 video monitoring. In addition, a remote monitoring system with alarms was installed and connected to LLEA for constant monitoring and possible intervention, if necessary, in a timely manner. The other measure taken was to limit the number of people who have access to such radioactive materials. We adopted a single person operator method and reduced the number of people having access from 145 people to only a few people. The adoption of such measures has reduced the risk significantly; however, the best way to remove the permanent risk of these radioactive materials that may be used for a dirty bomb is to use alternative technology to replace these high-activity radioactive sources. In 2013, Mount Sinai purchased its first x-ray irradiator to investigate the feasibility of using x-ray irradiators instead of cesium irradiators for research purposes for cells and small mice. The results from comparison studies were promising, which led to the decision of permanent migration of all cesium irradiators to x-ray irradiators. As of January 2018, Mount Sinai successfully disposed all its 137Cs irradiators. At this time, Mount Sinai, as one of the largest health care institutions in NY with about 50,000 employees, has migrated completely to alternative technology and removed the risk of malicious use of radioactive materials permanently.

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