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

Radiation safety measures in diagnostic nuclear medicine, based on the potential radiation dose emitted by radioactive patients

Objective

To measure the potential radiation dose emitted by patients who have recently undergone diagnostic nuclear medicine procedures, in order to establish optimal radiation safety measures for such procedures.

Materials and Methods

We evaluated the radiation doses emitted by 175 adult patients in whom technetium-99m, iodine-131, and fluorine-18 radionuclides were administered for bone, kidney, heart, brain, and whole-body scans, as measured with a radiation detector. Those values served as the basis for evaluating whole-body radiopharmaceutical clearance, as well as the risk for the exposure of others to radiation, depending on the time elapsed since administration of the radiopharmaceutical.

Results

The mean time to clearance of the radiopharmaceuticals administered, expressed as the effective half-life, ranged from 1.18 ± 0.30 h to 11.41 ± 0.02 h, and the mean maximum cumulative radiation dose at 1.0 m from the patients was 149.74 ± 56.72 µSv. Even at a distance of 0.5 m, the cumulative dose was found to be only half and one tenth of the limits established for exposure of the general public and family members/caregivers (1.0 mSv and 5.0 mSv per episode, respectively).

Conclusion

Cumulative radiation doses emitted by patients immediately after diagnostic nuclear medicine procedures are considerably lower than the limits established by the International Commission on Radiological Protection and the International Atomic Energy Agency, and precautionary measures to avoid radiation exposure are therefore not required after such procedures.

The Nuclear Medicine Patient as a Line Source: The Source Length Is Certainly Not the Patient Height, But It Is a Reasonable Approximation

ABSTRACT

Nuclear medicine patients are a source of exposure and should receive instructions to restrict contact time with different categories of people. The calculation of the restriction time requires that the dose rate at a given distance, known from an initial measurement and a whole-body retention function, can be extrapolated at other distances. As a basis for this extrapolation, it has been suggested to consider the patient as a line source. However, the validity of this suggestion is based on a few studies and limited measurement distances. We collected from the literature dose rates of nuclear medicine patients measured at different distances and investigated the robustness of the line source model. The cases of 18 F-FDG exams, 99m Tc bone scan exams, and 131 I for hyperthyroidism treatment and remnants ablation were considered. The data were pooled, different cases of measurement time after administration were considered, and the data were fitted according to the line source model in which the half patient thickness was introduced. It was found that the line source model fits well the data put with a source length that is radionuclide-specific and significantly different from the standard adult height. However, considering a standard source length of 176 cm and neglecting the patient thickness induced at maximum an overestimation by a factor of 2.5 when extrapolating from 1 m to 10 cm. Such an overestimation is not of considerable importance in the calculation of contact restriction times.

Radiation Dose to Medical Staff in 177Lu-PSMA-DKFZ-617 therapy And Estimation of Annual Dose

Radioligand therapy applications for metastatic castration-resistant prostate cancer have been continuously rising in most nuclear medicine departments in Iran, but to our knowledge, no one has studied the doses of staff who perform treatment procedures. The current study aimed to determine the external radiation dose received by the staff of patients treated with ¹⁷⁷Lu- prostate-specific membrane antigen therapy with and without a lead shield. This study used a dose ionization chamber to measure dose rates to the staff at various distances from patients and determined the average time spent by staff at these distances using an ionization chamber. Deep-dose equivalent to staff was obtained. The measured deep-dose equivalent to staff per patient was whitening the range of 1.8 to 5.2 mSv using a lead shield and 3.3 to 8.1 mSv without a lead shield. This study showed that a 2-mm lead shield markedly reduced the external dose to staff.It was indicated that the skill, accuracy, and speed of action of staff can directly affect their received dose.

MEASUREMENT OF EXTREMITY DOSES OF NUCLEAR ENERGY WORKER BY USING RING DOSIMETER

Finger doses can serve as a guide to suggest any needed modification in work practice to minimise radiation doses to the extremities. In the present study, radiation doses at the base of the middle finger of both hands of 20 nuclear energy workers handling 99mTc-labelled compounds,125I and131I during various diagnostic and therapeutic procedures in nuclear medicine were measured. The laboratory assessments were carried out by means of thermoluminescence ring dosimetry in Health Physics Division, Atomic Energy Center, Dhaka. The recorded extremity doses were then compared to their routinely monitored whole-body doses. The average annual finger doses recorded in this study were found to be 10.7 ± 8.2 and 12.7 ± 12.9 mSv, respectively, for the left- and right-hand fingers, which are at least 12-fold higher than the average whole-body dose. There was, however, no extreme case found of health hazard to the workers' hand, which exceeds maximum dose limit 500 mSv/year given by the International Commission on Radiological Protection. On comparing the average annual finger doses at different labs, significantly higher average dose was recorded at isotope-dispensing lab (19.6 ± 12.6 mSv/year) and then followed by gamma camera lab (13.2 ± 12.1 mSv/year) and radioimmunoassay lab (7.0 ± 5.5 mSv/year). These observations are fairly in good agreement with the reported results. The observations of the present study, therefore, may be implemented for the betterment of safety for the occupational workers in nuclear medicine facilities.

An assessment of nursing staffs' knowledge of radiation protection and practice

Although the exposure to nursing staff is generally lower than the allowable radiation worker dose limits, awareness and overcoming fears of radiation exposure is essential in order to perform routine activities in certain departments. Furthermore, the nursing staff, whether they are defined as radiation workers or not, must be able to respond to any radiological emergencies and provide care to any patient affected by radiation. This study aims to gauge the awareness of radiation safety among the nursing staff at a major hospital in different departments and recommend if further radiation safety training is required. A prospective multiple choice questionnaire was distributed to 200 nurses in 9 different departments. The questionnaire tested knowledge that would be taught at a basic radiation safety course. 147 nurses (74%) completed the survey with the average score of 40%. Furthermore, 85% of nurses surveyed felt there was a need for radiation safety training in their respective departments to assist with day to day work in the department. An increase in radiation safety materials that are specific to each department is recommended to assist with daily work involving radiation. Moreover, nursing staff that interact with radiation on a regular basis should undertake radiation safety courses before beginning employment and regular refresher courses should be made available thereafter.

Importance of bladder radioactivity for radiation safety in nuclear medicine

Objective: Most of the radiopharmaceuticals used in nuclear medicine are excreted via the urinary system. This study evaluated the importance of a reduction in bladder radioactivity for radiation safety.

Methods: The study group of 135 patients underwent several organ scintigraphies [40/135; thyroid scintigraphy (TS), 30/135; whole body bone scintigraphy (WBS), 35/135; myocardial perfusion scintigraphy (MPS) and 30/135; renal scintigraphy (RS)] by a technologist within 1 month. In full and empty conditions, static bladder images and external dose rate measurements at 0.25, 0.50, 1, 1.5 and 2 m distances were obtained and decline ratios were calculated from these two data sets.

Results: External radiation dose rates were highest in patients undergoing MPS. External dose rates at 0.25 m distance for TS, TKS, MPS and BS were measured to be 56, 106, 191 and 72 μSv h-1 for full bladder and 29, 55, 103 and 37 μSv h-1 for empty bladder, respectively. For TS, WBS, MPS and RS, respectively, average decline ratios were calculated to be 52%, 55%, 53% and 54% in the scintigraphic assessment and 49%, 51%, 49%, 50% and 50% in the assessment with Geiger counter.

Conclusion: Decline in bladder radioactivity is important in terms of radiation safety. Patients should be encouraged for micturition after each scintigraphic test. Spending time together with radioactive patients at distances less than 1 m should be kept to a minimum where possible.

Conflict of interest:None declared.

Estimated dose from diagnostic nuclear medicine patients to people outside the Nuclear Medicine department

Patients undergoing nuclear medicine scans can be a source of radiation exposure for staff, family and the public. In this paper, 12 common nuclear medicine scans are considered. Doses are estimated for a range of scenarios, to hospital staff, to the public and to the patients' co-workers and family. Estimates are based on dose rates measured as patients left the Nuclear Medicine department. Radiopharmaceutical clearance is calculated from biokinetic models described in International Commission on Radiological Protection publications 53, 80 and 106. For all scan types, and all scenarios, doses are estimated to be substantially less than the trigger level of 300 µSv. Within the hospital, Intensive Care Unit staff receive the highest dose (up to 80 µSv) from patients who have had a myocardial scan or a positron emission tomography scan. For out-patients, the highest doses (up to 100 µSv) are associated with travel on public transport (for 4 h) on the same day as the scan.

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.