RESUMO

This paper presents a fast and automatic flow-based method to extract 131I from biological samples and hospital waste, previous to liquid scintillation detection. 131I is a radionuclide extensively used in Nuclear Medicine due to their beta and gamma disintegrations, whereby hospitals have to manage the associated waste generation. The automatic developed system is based on Lab-On-Valve (LOV) flow-technique exploiting Cl-resin (135 mg per extraction). This methodology allows performing sample extractions and measurements on the same day, since the extraction frequency takes 1.4-4 h-1, depending on the analysed sample volume, plus up to 2 h of measurement for each vial. 131I is retained as iodine ion and eluted with sodium sulphide 0.2 mol L-1. The maximum sample volume that can be preconcentrated is 20 mL, reaching an extraction efficiency of 85 ±â€¯5%. The minimum detectable activity (MDA) is 0.05 Bq, showing a precision of 7% RSD (n = 5). Both, biological samples (urine and saliva) and hospital waste samples can be satisfactorily analysed by the proposed system, obtaining recoveries between 90 and 110%. The developed method is then suitable to implement in hospitals, improving the surveillance of the 131I environmental release.

Assuntos

RESUMO

This study evaluated biokinetic behavior of radioiodine in the bodies of ten female adult patients, with well-differentiated thyroid cancer, treated with 131I post-near total thyroidectomy, for ablation of remnant thyroid. In vivo and in vitro bioassay analyses were performed from the first hour following radioiodine administration until minimum detection limits were reached. The retention of 131I in the body from day 1 to day 6 after the intake may be mathematically represented by an exponential decreasing curve, with an average biological half-life of approximately 0.81 d, with the exception of patients who presented thyroiditis. From day 6 to day 13, urinary excretion rates indicated an increased liberation of iodine. After 2 wk, the body retention of iodine followed an exponential decrease, with a half-life of about 15 d. The average whole-body dose for these patients was 0.27 Gy, as estimated through cytogenetic techniques.

Assuntos

RESUMO

A dose reconstruction study was performed for personnel occupationally exposed to 131I in radiopharmaceutical production, during the years 1981 to 1994, with the objective of estimating committed effective doses and critically reviewing the main causes of their exposures. The workers were selected from a group responsible for the production, labelling and distribution of all radiopharmaceutical material in Brazil. Best estimates of intakes and doses were derived from the examination of the individual monitoring records and the reports from the radiation protection supervisor, complemented by interviews with the workers and with radiation protection officers. Over this time period workers had chronic as well as acute intakes of 131I. Committed effective doses were found to be dependent on the task performed by the worker and the site of operation and inversely correlated with the amounts of iodine handled. Intakes in general were a consequence of inadequate radiation protection control.

Assuntos

RESUMO

A useful correlation between maximum thyroid uptake and radioiodine urine levels at different times after exposure was developed in order to determine when the intervention with an adequate blocking agent might still be effective. In an animal model (dog), six different doses were administered in the range of 100-600 kBq. The best correlation was found between the 125I uptake after 48 h (T-48) and urine radioactivity 4-6 h (U-4, U-5, U-6) after exposure. For the case of U-4, the equation Y(T-48) = 0.790 X(U-4) + 2.973 (r = 0.974 with a level of significance of p < 0.001) was obtained. An analogous study, carried out in humans (n = 20) to whom 1311 was administered, showed a similar correlation and level of significance: Y(T-24) = 1.162 X(U-4)+3.263 (r = 0.926; p < 0.001). The validity of this correlation was confirmed in four volunteers who received small doses of 125I(25-100 kBq), with good agreement between measured and extrapolated thyroid uptake and a mean difference of less than 10% (CV = 16.2%). Three different blocking agents were then tested in the same dog: potassium iodide, potassium perchlorate, and a thionamide (Tapazole). The blocking action of the first two compounds was about 90%, as opposed to only 48% for the third compound. Potassium iodide was chosen for its limited side effects and more universal utilization. The final study, carried out with four different doses, indicated that 25 mg of KI is the ideal amount to be administered to the dog. This corresponds to approximately 100 mg for a 70 kg human being (i.e., 1.4 mg kg(-1)). This dose, when administered to a volunteer 4 h after exposure, provided a thyroid blocking of 68%.

Assuntos

Assuntos

RESUMO

Radio-iodine urinary excretion tests were carried out in 12 infants suffering from protein malnutrition. A technique of iodide precipitation was used, involving a dosage of 0.01 æc. I131/kg. Changes in basal metabolic rate were observed in the same infants. In the initial phase of hospital admission radio-iodine excretion was essentially normal. During recovery some cases showed a decrease in excretion. This decrease, however, was unrelated to dramatic increases in oxygen uptake and body weight and tended to lag behind them. It is concluded that thyroid action may facilitate, but in no way initiates, the accelerated respiratory activity during recovery (AU)

Assuntos

RESUMO

Con el propósito de estudiar el metabolismo de la Gonadotrofina Coriónica Urinaria (G.C.U.), se seleccionó un grupo de pacientes mujeres en diferente situación endocrina, a las cuales se inyectó en forma rápida y por vía endovenosa, hormona G.C.U.-I131. A continuación y con distintos intervalos de tiempo, se tomaron muestras de sangre y orina, procediéndose a determinar la radiactividad. En pacientes que fueron sometidas a intervenciones quirúrgicas por afecciones ginecológicas, se tomaron muestras de tejidos de diferentes órganos, que también fueron medidos. Idéntico procedimiento se siguió en un lote de animales, que fueron sacrificados luego de la administración endovenosa de G.C.U.-I131. El análisis e interpretación de los resultados, se realizó asumiendo que en la distribución en el organismo de la G.C.U.-I131, puede aplicarse el modelo de compartimientos mamilares. (AU)

Assuntos

RESUMO

Con el propósito de estudiar el metabolismo de la Gonadotrofina Coriónica Urinaria (G.C.U.), se seleccionó un grupo de pacientes mujeres en diferente situación endocrina, a las cuales se inyectó en forma rápida y por vía endovenosa, hormona G.C.U.-I131. A continuación y con distintos intervalos de tiempo, se tomaron muestras de sangre y orina, procediéndose a determinar la radiactividad. En pacientes que fueron sometidas a intervenciones quirúrgicas por afecciones ginecológicas, se tomaron muestras de tejidos de diferentes órganos, que también fueron medidos. Idéntico procedimiento se siguió en un lote de animales, que fueron sacrificados luego de la administración endovenosa de G.C.U.-I131. El análisis e interpretación de los resultados, se realizó asumiendo que en la distribución en el organismo de la G.C.U.-I131, puede aplicarse el modelo de compartimientos mamilares.

Assuntos