The use of delay tanks in the management of radioactive waste from thyroid therapy

Assessment of Radiation Exposure and Radioactivity from the Liquid Discharge in a Nuclear Medicine Facility

Aim

Radionuclide imaging and therapies produce radioactive liquid waste that may lead to significant radiation exposure to the general public. The study aims to assess the radiation exposure rate to public sewerage from a modified delay tank facility. We shall also evaluate the exposure rates and overall radioactivity at several points.

Materials and Methods

After having appropriate permission from the AERB, we measured the radiation exposure from the radionuclide therapy ward. Ward has three isolation beds and a single delay and decay tank of a capacity of 7500 liters. Effluents from the delay tank are processed at the filtration plant of the institute and subsequently released in the public sewerage. We obtained samples from several sites to determine discharged radioactivity.

Results

A total of 38 patients received 129.4 ± 42 mCi (Range 40- 200) radioiodine therapy during the study. Discharge of the tanks was done two times during the study. The radioactivity discharges into aeration plant were 89.2 and 71.2 mCi that correspond to 440.05 and 351 MBq/m3, respectively. This was diluted by the aeration tank (6 million liters). Finally, at the discharge time, the radioactivity in the discharge was 1.6 and 1.5 MBq/m3, respectively. The highest exposure rates were 14 μSv/h near the delay tank, which rapidly decreased on moving to the surrounding.

Conclusion

Our study indicates that the addition of the dilution method and close monitoring may significantly reduce the radiation exposure and overall radioactivity release from the facility. Old facilities that do not have space to add up the tank capacity may get a benefit from it. A small change in the practice, such as admitting patients alternate months or providing extra decay time for radioactive waste, may lead to a cost-effective alternative.

The effectiveness of wastewater treatment in nuclear medicine: Performance data and radioecological considerations

For planned and ongoing storage of liquid radioactive waste in a designated plant for a nuclear medicine therapy ward (decontamination system/decay system), detailed knowledge of basic parameters such as the amount of radioactivity and the necessary decay time in the plant is required. The design of the plant at the Department of Nuclear Medicine of the University of Cologne, built in 2001, was based on assumptions about the individual discharge of activity from patients, which we can now retrospectively validate. The decontamination factor of the plant is at present in the order of 10^-9 for ¹³¹I. The annual discharges have been continuously reduced over the period of operation and are now in the region of a few kilobecquerels. This work emphasizes the high efficacy of the decontamination plant to reduce the amount of radioactivity released from the nuclear medicine ward into the environment to almost negligible levels.

Medical health physics: a review

Medical health physics is the profession dedicated to the protection of healthcare providers, members of the public, and patients from unwarranted radiation exposure. Medical health physicists must be knowledgeable in the principles of health physics and in the applications of radiation in medicine. Advances in medical health physics require the definition of problems, testing of hypotheses, and gathering of evidence to defend changes in health physics practice and to assist medical practitioners in making changes in their practices as appropriate. Advances in radiation medicine have resulted in new modalities and procedures, some of which have significant potential to cause serious harm. Examples included in this review include radiologic procedures that require very long fluoroscopy times, radiolabeled monoclonal antibodies, and intravascular brachytherapy. This review summarizes evidence that supports changes in consensus recommendations, regulations, and health physics practices associated with recent advances in radiology, nuclear medicine, and radiation oncology. Medical health physicists must continue to gather evidence to support intelligent but practical methods for protection of personnel, the public, and patients as modalities and applications evolve in the practice of medicine.

Medical health physics: a review

Medical health physics is the profession dedicated to the protection of healthcare providers, members of the public, and patients from unwarranted radiation exposure. Medical health physicists must be knowledgeable in the principles of health physics and in the applications of radiation in medicine. Advances in medical health physics require the definition of problems, testing of hypotheses, and gathering of evidence to defend changes in health physics practice and to assist medical practitioners in making changes in their practices as appropriate. Advances in radiation medicine have resulted in new modalities and procedures, some of which have significant potential to cause serious harm. Examples included in this review include radiologic procedures that require very long fluoroscopy times, radiolabeled monoclonal antibodies, and intravascular brachytherapy. This review summarizes evidence that supports changes in consensus recommendations, regulations, and health physics practices associated with recent advances in radiology, nuclear medicine, and radiation oncology. Medical health physicists must continue to gather evidence to support intelligent but practical methods for protection of personnel, the public, and patients as modalities and applications evolve in the practice of medicine.

Relationship between orally administered dose, surface emission rate for gamma radiation, and urine radioactivity in radioiodine-treated hyperthyroid cats

OBJECTIVE

To determine the relationship between surface emission rate of gamma radiation and urine concentration of I131 (urine radioactivity) during the period 7 to 21 days after oral or SC administration of I131 to hyperthyroid cats.

ANIMALS

47 hyperthyroid cats administered I131 PO and 24 hyperthyroid cats administered I131 SC.

PROCEDURE

A dose of I131 (1.78 to 2.04 X 10(2) MBq [4.8 to 5.5 mCi]) was administered orally. Surface emission at the skin adjacent to the thyroid gland on days 7, 10, 14, 18, and 21 and number of counts/30 s in a urine sample (1 mL, obtained via cystocentesis) on days 7, 14, and 21 after oral administration were measured. Effective half-life (T1/2E) was derived for each point. Surface emission thresholds for maximum urine radioactivity values were established. A dose of I131 (1.48 X 10(2) MBq [4.0 mCi]) was administered SC. Urine radioactivity and surface emission rates for SC administration were compared with values for oral administration.

RESULTS

The T1/2E for surface emissions and urine radioactivity progressively increased toward values for physical T1/2 over time. The T1/2E for surface emissions was 2.19 to 4.70 days, and T1/2E for urine radioactivity was 2.16 to 3.67 days. Surface emission rates had a clinically useful threshold relationship to maximum urine concentrations of I131.

CONCLUSIONS AND CLINICAL RELEVANCE

Surface emission rates for cats administered I131 appeared useful in determining upper limits (threshold) of urine radioactivity and are a valid method to assess the time at which cats can be discharged after I131 administration.