The radiation dose to accompanying nurses, relatives and other patients in a nuclear medicine department waiting room

Time-related study on external exposure dose of 2-deoxy-2-[F-18]fluoro-D-glucose PET for workers' safety

Time-course study of individual dose equivalents of 2-deoxy-2-[F-18]fluoro-D-glucose positron emission tomography (¹⁸F-FDG PET) was conducted in different hospital workers, and the daily work duties were analyzed. For the measurements, a semiconductor dosimeter was used. The values at intervals of 1 min and 1 h, the monthly cumulative and daily cumulative doses, and trend graphs were acquired with dedicated software and displayed on the reader. The following radiation workers with duties involving maximum external exposure work were included: doctors making diagnoses (4.8 μSv/procedure), nurses removing injection needles (3.1 μSv/procedure), pharmacists performing quality control tests (2.9 μSv/procedure), nuclear medicine technologists assisting patient positioning (6.5 μSv/procedure), and cyclotron engineers performing daily checks (13.4 μSv/procedure). The results of analysis of daily work duties revealed the influencing factors of external exposure dose. To reduce the external exposure dose, investigators should shorten the patient's contact time with the ¹⁸F-FDG source or patient tracer.

Operator eye doses during computed tomography fluoroscopic lung biopsy

The aim of this work was to examine the peak entrance surface air kerma (peak ESAK) to the eyes during CT fluoroscopy lung biopsy, and the impact of lead glasses, exposure parameters, head rotation, and height on peak ESAK to the eyes. Two phantoms simulating the patient and radiologist were used, and 108 exposures were made using a 16-slice Toshiba Alexion CT scanner (Toshiba Medical Systems, Nasu, Japan). ESAK to the phantom radiologist's right eye was measured using an Unfors Xi dosimeter (RaySafe, Billdal, Sweden) with and without lead glasses at two kilovoltages (120 kVp and 135 kVp) and three milliampere settings (10 mA, 20 mA, and 30 mA. A paired t test was used to compare peak ESAK to the eye at different angles, heights, and kVp and mA with and without lead glasses. Peak ESAK was higher without compared to with lead glasses (p  ⩽  0.001). The peak ESAK to the eyes increased as the phantom radiologist rotated toward the gantry without lead glasses, from 2.42 μGy at 120° to 10.54 μGy at 30° (p  =  0.001). No significant difference was noted in peak ESAK with change in phantom radiologist height (p  >  0.05). An increase from 120 kVp to 135 kVp resulted in 23% and 26% increases in peak ESAK with and without lead glasses respectively (p  =  0.001). An increase of tube current from 10 mA to 20 mA almost doubled peak ESAK (p  =  0.005). Findings demonstrate that lead glasses reduce ESAK to the eyes, and that increased kVp, mA, and eye rotation to the gantry increase ESAK to the eyes.

Determining Waiting Room Occupancy at an Outpatient Clinic Using Simulated Observations and Probability-Duration Curves

Adequate allocation of physical resources in hospitals has become increasingly important with the rise of health care costs. Seat utilization in outpatient clinic waiting rooms is one resource that is particularly important to monitor, to not only ensure patient satisfaction but also accommodate patient flow. Currently, very few studies are available on seat occupancy and patient flow in standard waiting rooms, and studies often neglect important factors, such as hourly patterns of patient influx and occupancy duration. These factors were taken into consideration in our study of visitor occupancy and patient flow in an imaging-facility waiting room. This paper discusses the simulated observation approach that we have developed, which coupled in-person observations with RIS data analysis. Using RIS data to guide our initial in-person observations, we built a model for simulated observations, based on the merged RIS and observation data. To determine the appropriate number of seats needed to accommodate patients and their companions, simulated observation results were analyzed using a probability-duration curve. This curve considers maximum room occupancies as temporal events, with certain probabilities and durations. We demonstrated how simulated observations and probability-duration curves can provide hospital managers with an efficient and pragmatic way to determine waiting room occupancy.

On the safety of persons accompanying nuclear medicine patients

The presence of caretakers/comforters during nuclear medicine examinations is relatively common. These caretakers receive higher doses than the general public, who receive only environmental/background exposure. The aim of this research was to know about the doses received by two significant groups of caretakers: comforters of cancer patients (Group I) and mothers of small children (Group II). The patients were scheduled to undergo two different diagnostic studies: Inmuno-Scintigraphy using a monoclonal antibody bound to (99m)Tc (for adults) and Renal Scintigraphy using (99m)Tc-dimercaptosuccinic acid (for children). The average effective doses were 0.27 and 0.29 mSv for Groups I and II, respectively. Additionally, environmental monitoring was performed in the waiting room for injected patients (Room I) and inside the procedure room (Room II). Equivalent environmental doses of 0.28 and 0.24 mSv for Rooms 1 and II, respectively, were found, which are similar to values reported by other authors.

Radiation doses in the surroundings of patients undergoing nuclear medicine diagnostic studies

Dose rate measurements were performed at 0, 0.5, and 1 m from the external surface of 79 patients corresponding to the most frequent studies: 99mTc-cardiac with reinjection, 99mTc-cardiac single injection, 99mTc-bone scan, 99mTc-lung studies, and cardiac studies using 201Tl. Doses to staff, nearby patients, and the collective effective doses were estimated for the different working shifts and hospital areas. The estimated dose for nurses for 1 y was 518 microSv in the cardiology section and 338 microSv in the short stay section. For patients, the mean dose per stay was calculated to be 8.5 microSv in the cardiology section. The maximum dose that a patient could receive from a radioactive patient is 499 microSv for a double injection cardiac patient study. The maximum collective effective dose for the whole hospital was calculated to be 0.063 person-Sv. The probability of staff receiving doses higher than the limits for a working day is negligible. Maximum doses for staff and patients are far below dose limits for the public and therefore no additional radiological protection is needed.

Exposure of critical groups to nuclear medicine patients

When a radiopharmaceutical has been administered to a patient, assessment of the risk to critical groups from emitted photon radiation is by measurement of the integral dose received by an individual, or by measurements of the dose rate external to the patient coupled with appropriate occupancy factors. Estimations have been made from the available data of the dose to critical groups exposed to patients who have undergone diagnostic or therapeutic procedures. These dose estimations can be used to assess the impact of the proposed changes in statutory requirements, and to allow appropriate recommendations to be formulated. Two areas for consideration are that pregnant staff exposed to nuclear medicine patients will require an abdominal surface dose limit lower than 2 mSv to restrict their foetal dose to 1 mSv, and the current UK restrictions for the behaviour of patients who have undergone 131I treatment are either already adequate or can even be relaxed in order to restrict the exposure of members of the public to the proposed lower dose limits. Agreement is needed on the value (e.g. 95th percentile) from a study of the dose to a number of individuals which should serve as the basis for radiation protection recommendations.

Risk assessment of the nuclear medicine patient

Two types of risk are identified following the administration of a radiopharmaceutical to a patient: the risk to the patient, and the risk to critical groups exposed to the patient. The method for quantifying the risk to the patient is described in terms of estimating the effective dose. The main limitations in these estimates for adult and paediatric patients are uncertainties in the biokinetic data, and the assumption of a uniform distribution of activity in each organ. Effective doses from most nuclear medicine procedures will not exceed twice the annual dose from natural background radiation in the UK. Lack of human placental transfer data is now the main limitation to estimating fetal doses. The characteristics of two methods which can be used to derive the dose to critical groups exposed to nuclear medicine patients are reviewed. It is shown that studies using either method have indicated that the current recommendations in the UK for restricting the exposure of these groups and the recommendation recently proposed for restricting the exposure of pregnant members of staff are not appropriate. Revised recommendations for restricting the behaviour of patients administered iodine-131 should await the results of a current multicentre trial. The method to estimate the dose to a breast-fed infant from a mother administered a radiopharmaceutical is outlined, and the recently revised guidance for interrupting breast feeding is summarised. When a recommendation for controlling risk is to be derived from dosimetry data obtained from a number of individuals, an outstanding issue to be resolved is the value (e.g. 95% upper confidence limit) on which it should be based.