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.

Evaluating medical radiation doses is very important because an estimated 80% of man-made radiation doses comes from medical applications. This study evaluated X ray doses from lung and abdomen examinations. An ionisation chamber was extensively used to standardise X ray doses. This investigation evaluated the deep equivalent dose, the shallow equivalent dose, the effective dose, and the effective dose equivalent, by using TLD LiF:Mg,Ti placed in a male RANDO phantom. The experiments were performed according to the parameters (kV p , mA.s) and procedures used in actual clinical examinations. In addition, this study estimated the population dose due to diagnostic X ray treatments using nationwide statistics for annual cases of X ray diagnostic examinations, in cooperation with the Central Health Insurance Agency in Taiwan. Finally, risk analyses were performed to elucidate the stochastic effects.