Demonstrating Compliance With Proposed Reduced Lens of Eye Dose Limits in Nuclear Medicine Settings.

Based on ongoing research on ionizing radiation thresholds for cataracts, the International Commission on Radiological Protection has proposed new guidelines lowering the annual occupational lens of eye dose limit from 150 mSv to 20 mSv. The International Atomic Energy Agency has operationalized these new guidelines. Subsequently, national/regional radiation protection regulators are reviewing their lens of eye dose limits with an aim of moving towards the proposed new limits, resulting in licensees having to demonstrate compliance. In health care settings, fluoroscopic interventional practices generally have higher lens of eye doses and nuclear medicine settings generally have lower doses. A prospective cohort (n = 19) of nuclear medicine technologists wore dedicated lens of eye dosimeters for a 3 mo period synchronized with their body dosimeter schedules. The lens of eye dosimeters were validated to have a linear response in the anticipated dose ranges. The participants worked in a relatively high-volume nuclear medicine practice, which included general and cardiac, positron emission tomography/computed tomography, radiopharmacy, and cyclotron operations. The annualized dose ranges were 0.0-3.68 mSv (lens of eye) and 0.48-4.72 mSv (whole body). There was a good correlation between lens of eye and body dosimeter readings (R = 0.67). There were no significant differences in lens of eye dose by work type, worker sex, or side on which the dosimeter was worn. The findings should be generalizable to other similar practices, especially in North America, and should be sufficient to demonstrate regulatory compliance in nuclear medicine settings with the proposed new lens of eye dose limits.

Altered [99mTc]Tc-MDP biodistribution from neutron activation sourced 99Mo.

Given potential worldwide shortages of fission sourced 99Mo/99mTc medical isotopes there is increasing interest in alternate production strategies. A neutron activated 99Mo source was utilized in a single center phase III open label study comparing 99mTc, as 99mTc Methylene Diphosphonate ([99mTc]Tc-MDP), obtained from solvent generator separation of neutron activation produced 99Mo, versus nuclear reactor produced 99Mo (e.g., fission sourced) in oncology patients for which an [99mTc]Tc-MDP bone scan would normally have been indicated. Despite the investigational [99mTc]Tc-MDP passing all standard, and above standard of care, quality assurance tests, which would normally be sufficient to allow human administration, there was altered biodistribution which could lead to erroneous clinical interpretation. The cause of the altered biodistribution remains unknown and requires further research.

The effect of furosemide dose timing on bladder activity in oncology imaging with 18F-fluorodeoxyglucose PET/CT.

OBJECTIVE: To compare the effects of two furosemide administration protocols on bladder activity during 18F-fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) imaging. METHODS: A total of 109 consecutive patients with known or suspected malignancy, meeting our inclusion criteria, were chosen over a discrete time period. Group 1 (n=39) received furosemide 20 mg intravenous 15 min before PET/CT imaging (i.e. approximately 45 min after 18F-FDG administration). Group 2 (n=45) received furosemide 20 mg intravenous 15 min after 18F-FDG. Group 3 (n=25) did not receive furosemide and served as controls. Bladder standard uptake values (SUVs) and volume, and liver SUV data were collected. RESULTS: Relative to the control group, both furosemide groups showed significantly lower mean and maximum SUV bladder activities (P<0.001), lower mean bladder-to-liver SUV ratios (P<0.001), larger mean bladder volumes (P<0.001) and higher proportions of bladder PET/CT image mis-registration. Patients tolerated earlier administration of furosemide (group 2) better relative to urinary urgency during imaging. CONCLUSION: The use of a relatively simple diuretic protocol can significantly lower bladder FDG activity and potentially improve image quality by reducing bladder activity artifacts and avoid invasive bladder catheterization. Administering furosemide earlier after FDG injection (i.e. 15 min) versus later (i.e. 15 min before imaging) appears to be better tolerated by patients.

Practical Aspects of 18F-FDG PET When Receiving 18F-FDG from a Distant Supplier.

UNLABELLED: With PET becoming more widely used, there is an increase in the number of imaging centers being forced to rely on distant suppliers of (18)F-FDG. Because of the large distances between major urban centers, this is particularly true for PET centers in Canada. METHODS: Our PET center, located in Winnipeg, Manitoba, Canada, currently purchases (18)F-FDG from a commercial vendor located more than 1,000 km from Winnipeg, necessitating transport by commercial airline cargo. This dependence on air transport and a distant supplier creates a situation in which our (18)F-FDG supply is less reliable than it would be with onsite production. In this article, we offer insight into the obstacles we have encountered in imaging with a distant supplier of (18)F-FDG and the solutions we have implemented to minimize the disruption to our patients and maximize the number of scans performed each year. RESULTS: The development of contingency plans and protocols designed to suit our operating environment has allowed us to increase the number of patient scans obtained from 659 in year 1 to 993 in year 3, an increase of 51%, despite an increase in our actual number of scan days of only 24%. (18)F-FDG injection timetables are presented for a variety of scenarios including normal delivery, low shipped activity, and delayed delivery. CONCLUSION: Through the careful establishment of contingency protocols and management of (18)F-FDG shipments, patient throughput can be increased and disruptions minimized.