Combination of liquid scintillation counting and passive sampling strategy for the determination of¹³¹I in air and application to estimate the inhalation dose to the staff of a nuclear medicine service

Abstract

(131)I, commonly used in nuclear medicine, can be incorporated into the human body in a variety of chemical and physical forms. This study describes a sensitive method for the determination of (131)I concentration and its application to the estimation of the amount of airborne (131)I inhaled by staff workers of a Nuclear Medicine Department. Our method uses passive sampling with charcoal canisters followed by liquid scintillation counting, a very sensitive technique for the determination of low concentrations of airborne (131)I. We have studied the effects caused on the measured (131)I concentration in air by both, the doses administered to the patients and the distance of sampling canisters to the patient. We have found a direct relationship between the amount of (131)I activity administered and the airborne (131)I activity concentration. We have estimated the contribution of inhaled (131)I to the effective dose received by staff, finding differences between physicians and non-physician personnel. However, the measured exposure was quite low in both cases, thus suggesting that there is no need to introduce additional safety measures to the current ones.

Medical activated charcoal tablets as a cheap tool for passive monitoring of gaseous 131I activity in air of nuclear medicine departments

“…Due to these results, measurements of airborne 131 I activity were performed at the Department of Endocrynology and Nuclear Medicine Holycross Cancer Centre (E&M HCC Kielce, Poland) where the previously measured medical staff is worked. Results showed, that the activity of 131 I in the work space ranged from 28 ± 1 to 492 ± 4 Bq m −3 depending on location (nurses station or hot room) which was similar to results obtained by other authors [ 2 , 5 ]. With this levels of 131 I concentration in the workplace the annual inhalation effective dose can range from 0.47 mSv (female nurse) to 1.3 mSv (male technician) [ 6 ].…”

“…with KI or Ag salts) some modification of tablets to compare them with non-treated tablets were performed. This study is similar to that presented by Jimènez et al [ 2 ] but the activity of 131 I is measured directly, without the chemical treatment, that is necessary for LSC measurements. It is a practical approach, because nuclear medicine departments are equipped with counting systems, and therefore facilities can make measurements independently.…”

“…Therefore transport of highly radioactive Na 131 I (commercially available) is not necessary. 222 Rn trapping efficiency can also be used for calibration, where the standard equation used for calibration of activated charcoal detectors in a chamber is [ 2 ]: where C a (Bq m −3 ) is concentration inside glovebox during calibration, V (m 3 ) is the chamber volume, N is the count rate of the calibrated sample (cps), f a is the trapping efficiency (Bq m −3 cps −1 ), f γ is the germanium spectrometer efficiency for the gamma line (364 keV for 131 I or 666 keV for 126 I), t is the charcoal exposure time in the chamber (s) and k is the correction factor for radioactive decay during calibration and counting (s −1 ) calculated as: where λ is the decay constant of 131 I or 126 I (depending on the isotope used for calibration). The issue with this is that there may be only small amounts of charcoal used in a single container, which may only provide a weak signal in small HPGe detectors.…”

“…In modern nuclear medicine, 131 I is still one of the most widely used radionuclides as a short-lived ( T 1/2 = 8.03 d, where it’s effective half-life time in organisms is nearly equivalent to the physical half-live [ 1 ]) beta emitter for therapy and diagnostics of the thyroid gland. It can be used in many chemical forms, of which Na 131 I is the most popular, but other compounds such as 131 I-metaiodobenzoguanidine and 131 I-norcholesterol are also used [ 2 ]. Because activities of 131 I used in medicine are very high (up to several dozen GBq), there is an enhanced risk of releasing 131 I into the air and also to septic tanks systems [ 3 ].…”