ABSTRACT
In nuclear medicine departments, where radioactive sources are manipulated, the personnel can receive large radiation doses to the skin of their hands. For performing detailed characterisations and dose optimisations of these workplaces, active extremity dosemeters can be used as complementary tools to passive hand monitoring. Active extremity dosimetry is still a subject of research. In this context, IRSN has started a research and development programme. As a first step, a hospital workplace study has been performed using thermoluminescence dosemeters and has shown, in agreement with previous works, that the pads of the fingers, points that are very difficult to instrument, receive the largest doses. Numerical studies have now started, with the aim of calculating the dose equivalent gradients through the hands, in order to optimise the locations of the detectors.
Subject(s)
Arm/physiology , Models, Biological , Occupational Exposure/analysis , Radiation Monitoring/instrumentation , Radiation Monitoring/methods , Radiation Protection/instrumentation , Radiation Protection/methods , Arm/radiation effects , Feasibility Studies , Humans , Models, Statistical , Monte Carlo Method , Personnel, Hospital , Radiation Dosage , Risk Assessment/methods , Risk Factors , Skin/radiation effects , Skin Physiological PhenomenaABSTRACT
Physical and biological dosimetry were investigated in 45 rheumatoid arthritis patients treated by radiosynoviorthesis (RSO) with 186Re-sulphide (medium-sized joints) and 169Er-citrate (digital joints). Biological dosimetry involved scoring dicentrics in lymphocytes, cultured from blood samples withdrawn just before and 6 h, 24 h and 7 days after treatment. Physical methods included repeated blood sample counts and scintigraphy data. For erbium-169 (pure beta emitter), only bremsstrahlung could be measured and solely in the injection area. For rhenium-186 (both beta and gamma emitter), whole body scans and static images of joints and locoregional lymph nodes were performed. Dosimetry calculations were in accordance with the MIRDOSE 3 software and tables. For erbium-169 (21 patients), either metacarpophalangeal (30 MBq) or proximal interphalangeal (20 MBq) joints of the hands were treated (one joint per patient); 18 patients (out of 21) were interpretable for biological dosimetry, 10 (out of 11) for physical dosimetry and six (out of 10) for both. For rhenium-186, 23 wrists, nine elbows, three shoulders and two ankles were injected in 24 patients, with a maximum of three joints per patient (70 MBq per joint); 20 patients (out of 24) and 10 (out of 10) were interpretable for biological and physical dosimetry, respectively, and eight (out of 10) for both methods. Erbium-169 biological dosimetry was negative in all interpretable patients, and physical dosimetry gave a blood dose of 15 +/- 29 microGy and an effective dose lower than 1 mSv/30 MBq. For rhenium-186, biological results were negative in 16 patients (out of 20), but showed a blood irradiation around 200 mGy in the last four. A significant cumulative increase of dicentrics 7 days after injection (16/10,000 instead of 5/10,000 prior to treatment; p < 0.04) was also noted. Gamma counts gave a blood dose of 23.9 +/- 19.8 mGy/70 MBq and the effective dose was found to be 26.7 +/- 5.1 mGy/70 MBq, i.e. about 380 microGy.MBq-1. Erbium-169 RSO is very safe from both physical and biological dosimetry standpoints. Rhenium-186 leak is greater, as demonstrated by the higher blood activity and the measurable, although limited, dicentrics induction in blood lymphocytes. However, the effective dose remains moderate, i.e. 30 times lower than in 131I therapy in benign thyroid diseases.
