Reduction of extremity dose in the radiopharmacy

Strategies for assessment of doses to the tips of the fingers in nuclear medicine

Staff manipulating radiopharmaceuticals in radiopharmacies and nuclear medicine departments can receive significant radiation doses to the tips of their fingers. However, dosemeters for monitoring the fingers are frequently attached to a ring worn at the base of the finger and the doses recorded are significantly lower. Therefore a correction factor is required to estimate the dose to the finger tip from that recorded by a ring dosemeter. A survey of practices in UK nuclear medicine departments has been undertaken via a questionnaire, results of studies in the literature reporting ratios of doses to the tip and base of the finger reviewed, and patterns of finger exposure studied using an electronic dosemeter. The survey indicates that UK staff use vial and syringe shields for the majority of manipulations. Ratios between doses to the tip and base of the index finger reported in the literature vary between 2 and 6. Higher ratios appear to be associated with poor protection practices including not using syringe shields and use of a finger to support a syringe needle. Staff are recommended to wear dosemeters on the palmar side of the index finger of each hand. Dosemeters worn at the finger tips are ideal, but doses to the tips can be estimated from ring dosemeters worn on the index fingers, and factors that can be used for this are proposed. For staff who always use vial and syringe shields and never touch the syringe needle or vial a factor of 3 is appropriate. For staff who mostly use syringe shields and may occasionally support a needle during an injection, a factor of 4 can be used, while for others a factor of 6 should be applied.

Radiation exposure to nuclear medicine personnel handling positron emitters from Ge-68/Ga-68 generator

Objective:

To measure the radiation exposure to nuclear medicine personnel during synthesis and injection to the patients of Ga-68 1,4,7,10-tetraazacyclododecane-N,N′,N″,N″′-tetraacetic acid (DOTA)-1-Nal³-octreotide (NOC)- (DOTA-NOC) using ring thermoluminescence dosimeters (TLDs).

Materials and Methods:

Synthesis of Ga-68 DOTA-NOC was done on a semi-automated system. Finger doses were measured during synthesis and injection of Ga-68 DOTA-NOC. The occupational workers wore TLDs at the base of ring finger of both hands. The finger doses of two radio chemists were measured during synthesis of Ga-68 DOTA-NOC while that of a physician during its injection to the patients.

Results:

Duration of the study was eight months and a total of 20 samples were prepared. During synthesis, the mean dose to base of left ring finger was 3.02 ± 1.01 mSv and to base of right ring finger was 1.96 ± 0.86 mSv. Mean dose to base of left ring finger was 1.26 ± 0.35 mSv while that to base of right ring finger was 1.03 ± 0.13 mSv during injection. The mean dose was observed to be higher during synthesis than injection. However, the difference was not significant (P = 0.27 and P = 0.18, respectively). Overall mean finger dose of left hand was 2.43 ± 1.21 mSv, whereas for the right hand the same was 1.65± 0.82 mSv.

Conclusion:

Finger doses to radio chemists during semi-automated synthesis of Ga-68 DOTA-NOC and that to the physician involved in injection of Ga-68 DOTA-NOC were found to be within permissible limits. Ring dosimeters must be worn for the safety of the nuclear medicine personnel involved in synthesis and injection of Ga-68 DOTA-NOC.

Extremity dosimetry for radiation workers handling unsealed radionuclides in nuclear medicine departments in India

In India, for the past five decades, whole body radiation dose of radiation workers has been monitored by means of film and thermoluminescent dosimeter (TLD) badges worn on the body. However, there are no provision/regulatory requirements to monitor doses received at the extremities, i.e., to fingers. Finger dose monitoring is essential for controlling the extremity dose limits for occupational personnel handling unsealed radioactive sources. In order to estimate the doses received in various types of procedures using unsealed sources, finger dose monitoring was carried out in 54 major institutions in the country using a specially designed plastic finger ring embedded with a TLD. The maximum finger dose of occupational workers involved in handling Tc in such activities as extraction and radiopharmacy work is 0.35 mSv GBq; during injection of radiopharmaceuticals and scintigraphy, the doses were observed to be 1 and 0.95 mSv GBq, respectively. Similarly, while handling F-FDG, the maximum doses received during dispensing, injection, and scintigraphy were 0.098, 0.324, and 0.56 mSv GBq, respectively. The maximum radiation dose received during Re/Re balloon angioplasty and while handling Sm was 3.92 and 6.5 mSv GBq, respectively. All the doses recorded were well within the prescribed limit. However, monitoring of these doses periodically would help in compiling the feedback regarding the work practices followed in institutions handling radioisotopes in the country and would also help in maintaining a record of safe work procedures while handling radioisotopes.

Feasibility study of an active extremity dosimetry prototype

In nuclear medicine departments, where radioactive sources are manipulated, the personnel can receive large radiation doses to the skin of their hands. For performing detailed characterisations and dose optimisations of these workplaces, active extremity dosemeters can be used as complementary tools to passive hand monitoring. Active extremity dosimetry is still a subject of research. In this context, IRSN has started a research and development programme. As a first step, a hospital workplace study has been performed using thermoluminescence dosemeters and has shown, in agreement with previous works, that the pads of the fingers, points that are very difficult to instrument, receive the largest doses. Numerical studies have now started, with the aim of calculating the dose equivalent gradients through the hands, in order to optimise the locations of the detectors.

Deficiencies of Product Labeling Directions for the Preparation of Radiopharmaceuticals

OBJECTIVE

To identify potential deficiencies in product labeling (package insert) instructions for the preparation of radiopharmaceuticals.

METHODS

Preparation instructions, which include both reconstitution and quality control (QC) directions, as stated in the package inserts were evaluated for all commercially available reconstituted radiopharmaceuticals. Reviews of the package inserts were initially performed by each author, and then all identified deficiencies were compiled and evaluated by all authors. The preparation scenario for each package insert evaluated was based on a centralized nuclear pharmacy operation assuming typical support personnel, standard operating equipment, and workload.

MAIN OUTCOME MEASURE

The instructions as stated in each package insert for the preparation (including QC) were rated as inadequate if a satisfactory preparation could not be prepared by a nuclear pharmacist or physician when instructions were followed exactly.

RESULTS

Identified deficiencies in package insert instructions for the preparation of radiopharmaceuticals fell into the following five categories: (1) absent or incomplete directions (especially with regard to QC procedures); (2) restrictive directions (e.g., specific requirement to use designated needles, chromatography solvents, counting devices), (3) inconsistent directions (e.g., different reconstituted volumes for the same final drug product, unworkable expiration times); (4) impractical directions (e.g., unrealistically low reconstituted activity limits, dangerously high number of radiolabeled particles); and (5) vague directions (e.g., use of the words "should," "may," "recommend").

CONCLUSION

Manufacturers' directions for the preparation of radiopharmaceuticals often contain deficiencies and should be viewed as standard guidance rather than as requirements. Just as physicians are permitted to use U.S. Food and Drug Administration (FDA)-approved drugs for off-label indications, nuclear pharmacists should be allowed to use alternative methods for preparing radiopharmaceuticals, provided those methods have been validated to be as good as the stated directions and that the nuclear pharmacists do not engage in activities that fall outside the normal practice of pharmacy. Manufacturers, FDA, nuclear pharmacists, and nuclear physicians should work together to address identified deficiencies in package insert directions.

A study of doses to the hands during dispensing of radiopharmaceuticals

Radiation doses to both the fingertip and finger base of staff preparing radiopharmaceuticals in a radionuclide dispensary have been monitored for more than 5 years. The records show a fall in dose thought to be due, largely, to the introduction of all-glass (lead) syringe shields. In 1998, the annual radiation dose (mean +/- standard deviation) to the fingertip had fallen to 83+/-11 mSv, which corresponded to 0.18 mSv per 10 GBq 99Tc(m) handled. There was less reduction in dose to the finger base, which, in 1998, was 70% of that to the fingertip. To study the effect of a syringe shield on the distribution of dose across the hands, model hands were constructed and a gamma extremity monitoring system (GEMS) was used to measure dose. When a radiopharmaceutical is dispensed, contributions to the dose from activity in the vial and syringe change during the procedure. As a result, relative doses to different fingers and the ratios of doses to the tip and base of each finger will fluctuate throughout dispensing. In the absence of a syringe shield, the front tip of the index finger received the greatest radiation dose. When a syringe shield was used, doses were lower and the dose distribution was completely different. These findings have important implications in terms of compliance with the new UK Ionizing Radiations Regulations, where the dose limit is applied to 'the dose averaged over any area of 1 cm2 regardless of the area exposed'.