Dosimetry for the study of medical radiation workers with a focus on the mean absorbed dose to the lung, brain and other organs.

BACKGROUND: The reconstruction of lifetime radiation doses for medical workers presents special challenges not commonly encountered for the other worker cohorts comprising the Million Worker Study. METHODS: The selection of approximately 175,000 medical radiation workers relies on using estimates of lifetime and annual personal monitoring results collected since 1977. Approaches have been created to adjust the monitoring results so that mean organ absorbed doses can be estimated. RESULTS: Changes in medical technology and practices have altered the radiation exposure environments to which a worker may have been exposed during their career. Other temporal factors include shifts in regulatory requirements that influenced the conduct of radiation monitoring and the changes in the measured dose quantities. CONCLUSIONS: The use of leaded aprons during exposure to lower energy X rays encountered in fluoroscopically based radiology adds complexity to account for the shielding of the organs located in the torso when dosimeters were worn over leaded aprons. Estimating doses to unshielded tissues such as the brain and lens of the eye become less challenging when dosimeters are worn at the collar above the apron. The absence of leaded aprons in the higher energy photon settings lead to a more straightforward process of relating dosimeter results to mean organ doses.

Radiation dose reduction at a price: the effectiveness of a male gonadal shield during helical CT scans.

BACKGROUND: It is estimated that 60 million computed tomography (CT) scans were performed during 2006, with approximately 11% of those performed on children age 0-15 years. Various types of gonadal shielding have been evaluated for reducing exposure to the gonads. The purpose of this study was to quantify the radiation dose reduction to the gonads and its effect on image quality when a wrap-around male pediatric gonad shield was used during CT scanning. This information is obtained to assist the attending radiologist in the decision to utilize such male gonadal shields in pediatric imaging practice. METHODS: The dose reduction to the gonads was measured for both direct radiation and for indirect scattered radiation from the abdomen. A 6 cm3 ion chamber (Model 10X5-6, Radcal Corporation, Monrovia, CA) was placed on a Humanoid real bone pelvic phantom at a position of the male gonads. When exposure measurements with shielding were made, a 1 mm lead wrap-around gonadal shield was placed around the ion chamber sensitive volume. RESULTS: The use of the shields reduced scatter dose to the gonads by a factor of about 2 with no appreciable loss of image quality. The shields reduced the direct beam dose by a factor of about 35 at the expense of extremely poor CT image quality due to severe streak artifacts. CONCLUSION: Images in the direct exposure case are not useful due to these severe artifacts and the difficulties in positioning these shields on patients in the scatter exposure case may not be warranted by the small absolute reduction in scatter dose unless it is expected that the patient will be subjected to numerous future CT scans.

Radiation exposure of computed tomography and direct intracoronary angiography: risk has its reward.

A hallmark of noninvasive testing has been the identification of patients with coronary artery disease. Now, with multislice computed tomography (MSCT), information about coronary anatomy can be obtained without the need for catheterization. A major concern with the application of MSCT coronary angiography is the radiation exposure to the patient. Both MSCT and selective coronary angiography share the risks of procedure-related complications, such as allergic contrast reactions, and stochastic risks (i.e., cancer induction) of low-level radiation. There is a substantially higher radiation dose for MSCT angiography (effective dose [ED] 14 mSv) than for CCA (ED 6 mSv). These exposures yield lifetimes risks of 0.07% and 0.02%, respectively, of inducing a fatal cancer in the general (i.e., age- and gender-averaged) population. However, CCA poses additional serious risks associated with cardiac catheterization, yielding a non-radiogenic risk of mortality--excluding contrast reactions--of 0.11%. Combining the radiogenic and non-radiogenic risks (0.02% and 0.11%, respectively) yields a 0.13% overall risk of mortality from CCA--nearly two-fold higher than that for MSCT angiography (0.07%). If one were to use the lower, more age-appropriate risk factors for the older patient population in question, the radiogenic risks of both CCA and MSCT would be reduced by about one-half, further widening the overall safety ratio of MSCT relative to CCA. When weighing the relative risks of alternative medical procedures, therefore, it is imperative that one consider the overall risk of the respective procedures.