A New Proposal for Monitoring Patients in Nuclear Medicine

Abstract

The measurement of exposure rates is fundamentally important in the release of patients given radioactive materials and for keeping the exposures of others as low as reasonable achievable. Similar measurement methodologies have generally been used for point and extended sources, but this approach may lead to methodological errors in calculating radiation dose estimates. In this study, nuclear medicine patients who received high activities of Na131I for therapy were monitored using different measurement methodologies, and the results showed that the usual measurement performed at 1.0 m in front of the body resulted in a mean error of 40% between experimental and theoretical exposure rates. The best measurements were obtained when performed at 2.0 m in front of the patients. With this approach, the error was about 2% between experimental and theoretical values. These findings suggest a new methodology for patients' measurement in nuclear medicine and could be useful for personal monitoring in cases of radiological emergencies involving 131I ingestion.

Radiation Safety Issues in Y-90 Microsphere Selective Hepatic Radioembolization Therapy: Possible Radiation Exposure from the Patients

“…This wide variety of ratio seems to be partly due to variability of tumor location and measurement geometry. These results are contrary to the observation by Siegel et al [27] and Willegagnon et al [28], who dealt with gamma radiation and observed that measured TEDE is lower than theoretical TEDE. To our knowledge, this is the first report that compares the theoretical TEDE with measured TEDE in Y-90 microsphere RET.…”

“…So, the actual radiation dose may be different from the theoretically calculated TEDE based on administered activity. The 'measured' exposure dose equivalent calculated by actual measurement of ambient exposure rate can be different from estimated 'theoretical' exposure dose [28]. According to our observation, the 'measured' TEDEs are generally higher than those of 'theoretical' TEDEs as the ratio of 'measured' TEDE to 'theoretical' TEDE (Dm/Dt ratio) is from 1.28 to 65.99 (Table 3).…”

“…Calculation of radiation of the absorbed effective dose equivalent to other individuals is necessary for radiation safety concerns. Radioprotection precautions must consider the characteristics of administered radioisotopes [16,27,28]. Greater concerns should be exercised when dealing with therapeutic procedures.…”

“…Possible radiation exposure to other individuals from internally administered gamma-ray emitting radioisotopes is well recognized and there are ample reports [17,18,27,28]. For the gamma-emitting radioisotopes, the TEDE can be calculated using the specific gamma-ray exposure rate constants and physical half-lives for radionuclides typically used in nuclear medicine are given in the USNRC Regulatory Guide 8.39, Appendix A [17].…”

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“…The stay period of radioiodine administered patients solely depends upon the exposure rate measurement [4] by which the dose to others may be minimized [12,13]. If the administered radioiodine to the patient is more than 30 mCi, isolated hospitalization is necessary until the reduction of residual activity to 30 mCi or decline of the exposure rate to 50µSv/ hr (micro Sievert) at one meter from patient [14,15].…”