Radiation Safety Implications of 131i Treatment in a Patient With Grave???s Disease Undergoing Home Hemodialysis

Abstract

The radiation safety implications following the administration of 131I for the treatment of Grave's disease to a patient undergoing home-based renal dialysis was investigated. External dose-rate measurements from the patient revealed a peak value at around day 2, post administration. The effective half-life was determined as 6.5 d. From day 3, the clearance of 131I was observed to be fairly constant and equated to 2.7% per day or 5.4% per dialysis session. From this the biological half-life was determined as 15 d. Radiation monitoring of the dialysis unit, disposables, and bed linen found no detectable contamination. For the purpose of useful protection, at a distance of 1 m from the patient, the average dose rate over the effective treatment duration was determined to be 8 microSv h(-1) and at 2 m distance, 2.6 microSv h(-1). Thus, in order to keep below a level of dose constraint of 3 mSv the total allowable time spent at 1 m would be 375 h or 15 h per day. To comply with a 1-mSv constraint, the average daily exposure allowable at 1 m would be 5 h per day. Neither of these time limits would be difficult to achieve for the majority of situations with fairly modest behavioral constraints. Initial discharge concentration rates into the waste water system are estimated at 200 MBq m(-3) and therefore might need to be considered depending upon the regulatory environment.

Radioyodo como tratamiento de hipertiroidismo en un paciente en hemodiálisis: Caso clínico

“…Estudios han mostrado que la actividad máxima del 131-I se produce al segundo día post administración 3,[6][7][8] . La tasa de eliminación después de cada sesión de HD es menor en hipertiroidismo que en CDT (2,7-5,5% versus 50-70%, respectivamente) 3,11,12 , determinando tiempos de vida media efectiva en pacientes hipertiroideos de 6,5-7,1 días 3,11,12 . En este caso se utilizó una dosis estándar de 131-I para hipertiroidismo, teniendo en consideración que, a diferencia de lo que ocurre en pacientes tiroidectomizados por CDT, la dosis requerida para tratamiento del hipertiroidismo es significativamente menor, además de que esta dosis sería captada en su gran mayoría por el tejido tiroideo sin exponer a exceso de radiación a otros órganos; por otra parte, se estimó una dosis suficiente para tratar en forma definitiva el hipertiroidismo y evitar la necesidad de una segunda dosis de 131-I.…”

“…La tasa de exposición a distancia evidenció una curva descendente con una pendiente poco pronunciada (Figura 1), lo que refleja una tasa de eliminación menor, con registros de exposición a radiación de 0,013 mSv/Hr a 1 metro y 69% de disminución de radioactividad al décimo día de la administración, comparable con las series de Homer et al y Simpson et al 11,12 . La baja actividad de 131-I medida en sangre y líquido de dializado antes, durante y después de las sesiones de HD refleja la baja tasa de exposición de los tejidos extratiroideos y la baja tasa de eliminación en líquido de dializado, respectivamente, esto también se explica por la mayor captación del 131-I por el tejido tiroideo, lo que determina menor blindado cuando no estaba en contacto directo con la paciente.…”

Characteristics of Graves’ Disease in Haemodialysis Patients

“…Treatment of Graves' disease is efficient and resolves cardiac symptoms of the disease [9,14]. Treatment of Graves' disease in these patients is initially antithyroid agent propylthiouracil [9,15] and then iodine-131 therapy [15,37]. The risk of the antithyroid agent propylthiouracil treatment is neutropenia.…”

“…However, the daily dose for haemodialysed patients can be the same with patients having normal renal function since almost all the doses of tratment are eliminated by dialysis through diffusion because of the weak proteic liaison of the radioiodine [41]. The peak value is around the second day post administration [37]. More than 70% of the radioactivity is eliminatd after the first haemodialysis session [38,42].…”

“…More than 70% of the radioactivity is eliminatd after the first haemodialysis session [38,42]. The effective half-life is 6.5 days [37]. From the third day, the clearance of 131iodine was observed to be fairly constant and equated to 2.7% per day or 5.4% per dialysis session [37].…”