Monitoring Individual Occupational Radiation Exposure at Multiple Institutions.

Within a few years of its' discovery, ionizing radiation demonstrated adverse effects on biological systems. Since that time great strides were made in both radiation protection, detection, and personnel monitoring. Monitoring occupational radiation dose to individuals is enforced by several regulatory agencies in the United States (U.S.) and is referenced in numerous sections of the Code of Federal Regulations (CFR). A literature review with an examination of regulatory guidelines and a Radiation Safety Officers (RSO) survey was conducted to evaluate how often radiation dose exposure is monitored when an individual receives occupational radiation dose at more than one facility. The length of time an RSO has overseen the radiation safety program at his/her institution can impact if dosimetry reports are requested for individuals that work at multiple places. Despite having safer equipment and occupational radiation exposure standards, there is no universal mechanism to track and record exposure for individuals working at more than one institution.

Added Value of Digital over Analog PET/CT: More Significant as Image Field of View and Body Mass Index Increase.

The digital PET/CT scanner with digital photon-counting technique promises a shorter scan time, improved small-lesion detectability, and reduced radiation dose for the PET and CT portions of the exam while improving image quality. Methods: In this single-institution retrospective review study, 84 participants who had undergone PET/CT on both analog and digital scanners were analyzed. The aim was to evaluate the impact of image field of view (FOV) and body mass index (BMI) on the digital compared with the analog PET/CT scanners. The participants were categorized into different groups based on their BMI. Total scan times, 18F-FDG doses, and dose-length products (DLP) were collected and compared. Image quality was also assessed by certified nuclear medicine physicians and graded on a scale from 1 to 5. Results: In the skull-to-mid-thigh FOVs, the digital scanner had a scan time shorter by 37% (P < 0.001), a 18F-FDG dose lower by 16% (P < 0.001), but only an 8% reduction in DLP (P = 0.2). In the head-to-toe FOV cases, the digital scanner showed reductions in scan time (33%; P < 0.001), 18F-FDG dose (13%; P < 0.001), and DLP (19%; P < 0.001). When BMI was accounted for, the digital scanner had a scan time shorter by 33% (P < 0.001), as well as a reduced DLP (P < 0.001) and 18F-FDG dose (P < 0.001), with the most prominent changes being in the overweight and obese participants. Image quality was also improved by the digital scanner, with a score of 4.5, versus 4.0 for the analog scanner. Conclusion: The digital scanner has a shorter scan time and lower DLP, requires a lower 18F-FDG dose, and provides improved image quality when compared with the analog scanner. The most impactful difference in scan time, DLP, and 18F-FDG dose were observed in obese and overweight participants.

Do Gadolinium-Based Contrast Agents Affect 18F-FDG PET/CT Uptake in the Dentate Nucleus and the Globus Pallidus? A Pilot Study.

Gadolinium is toxic and to avoid its deposition in tissues, it must be chemically bonded with nonmetal ions to facilitate its excretion by the kidneys. High signal intensity in the dentate nucleus (DN) and globus pallidus (GP) on unenhanced T1-weighted MR images has been both morphologically and pathologically linked to gadolinium-based contrast agent (GBCA) retention in the brain. The purpose of this study was to determine whether repeated administrations of GBCA would affect the uptake of 18F-FDG in the DN and GP on PET/CT. Methods: Three hundred seventy-six patients who underwent both contrast-enhanced MR (CE MR) of the brain and PET/CT from January 2004 to October 2015 were identified. Patients with a history of brain irradiation or hepatic or renal disease were excluded. The SUVmax was measured in the DN and GP on the PET/CT scan in patients who had 3-6 successive CE MR brain studies. The SUVmax of the corresponding areas in the control group of patients who had not undergone previous CE MR and who had a normal, unenhanced MR finding of the brain was also measured. A Wilcoxon 2-sample test was used for statistical analysis. Results: Fifteen of 376 (4%) patients (mean age ± SD, 54 ± 18 y; 10 men and 5 women) were included in the subject group, and 15 patients (mean age ± SD, 36 ± 9 y; 11 men and 4 women) were included in the control group. The median DN SUVmax was significantly lower in the subject group than in the control group (5.4 vs. 6.4, respectively; P = 0.021). Similarly, the median GP SUVmax was significantly lower in the subject group than in the control group (8.8 vs. 12.1, respectively; P = 0.003). Conclusion: The median SUVmax in the DN and GP was 16% and 27% lower, respectively, in patients who received GBCAs than in those who had not received GBCAs, possibly related to gadolinium deposition in these areas.

Prevalence, challenges, and solutions for (18)F-FDG PET studies of obese patients: a technologist's perspective.

UNLABELLED: Obesity has reached epidemic proportions in the United States; hence, it is frequently encountered in patients undergoing (18)F-FDG PET studies. The purpose of the current study was to present a technologist's perspective on the prevalence of obesity and the challenges and solutions in imaging obese patients in our PET facility. METHODS: From October 2002 to October 2003, whole-body (18)F-FDG PET was performed on 1,164 patients with a known or suspected malignancy. Images were acquired 45-60 min after (18)F-FDG injection (7.4 MBq [0.2 mCi]/kg, with a maximum of 925 MBq [25 mCi]) on a PET scanner using a 4-min emission and 3-min transmission time per bed position. A database was maintained of patient height and weight, and body mass index (BMI) was calculated. Patient obesity was classified as overweight (BMI > or = 25 kg/m(2)), obese (BMI > or = 30 kg/m(2)), or malignantly obese (BMI > or = 40 kg/m(2)). In addition, PET technologists recorded any problems and attempted solutions related to the patient weight. RESULTS: BMI calculations showed that 528 patients (45.4%) were overweight or obese (322 men and 206 women; mean age, 55 y). Of those, 201 (38%) were overweight, 270 (51%) were obese, and 57 (11%) were malignantly obese. Problems encountered in these patients included difficult intravenous access (15%), difficult patient positioning (10%), patient motion (7%), an incomplete study (emission only) (1%), and potentially higher radiation exposure to the technologist because of extra time spent near the patient. Attempted solutions included adjusting the schedule to allow more time per patient, adjusting the dose based on body weight, using varied positioning techniques, dividing the study to allow a respite between different image combinations, and dividing time spent with obese patients among the technologists involved. CONCLUSION: Excessive body weight and related problems have commonly been encountered in our PET facility. (18)F-FDG PET studies of obese patients represent an ongoing challenge, which requires patient-tailored solutions to avoid compromising image quality and risking higher radiation exposure to the technologists.