Total Effective Dose Equivalent to Caregivers from Hospitalized Patients Treated with High Dose Radioiodine for Thyroid Carcinoma.
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Thyroid cancer patients treated with high-dose radioactive iodine (3.7-7.4 GBq) are different from other people because after the administration, the radionuclide I-131 is excreted via urine, feces, saliva and breathing, and also via exposure to other patients. Caregivers of the patient may receive higher radiation doses than normal. The purposes of this study were to estimate the total effective dose equivalent from internal and external exposure to caregivers of patients treated with high dose I-131 admitted at Siriraj Hospital, and to compare the estimated dose with the dose constraint of 5 mSv per annum for caregivers. Thirteen caregivers of 13 patients who underwent radioiodine therapy for thyroid cancers following a standard protocol were given specific instructions with regard to radiation safety and were attached to an electronic personal dosimeter and a personal air sampler pump continuously to measure received radiation dose on a daily basis over three days in the hospital. On discharge day, caregivers were asked to perform an in vivo bioassay by the thyroid uptake instrument. The results from the thirteen caregivers were divided into 3 groups. The total effective dose equivalent to caregivers of patients administered 3.7 GBq (n = 1), 5.55 GBq (n = 9), and 7.4 GBq (n = 3) were 0.159 mSv, 0.123 to 0.629 mSv, and 0.631 to 0.718 mSv, respectively. There values were well below 5 mSv per episode as proposed in the IAEA Safety Reports Series No. 63 and the ICRP Publication 103.Keywords:
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Radioiodine therapy
Dose rate
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Radiation exposure to the patient’s family members is one of the major concerns during thyroid cancer radionuclide therapy. The aim of this study was to measure the total effective dose of the family members by means of thermoluminescence personal dosimeter, and compare with those calculated by analytical methods. Eighty five adult family members of fifty one patients volunteered to participate in this research study. Considering the minimum and maximum range of dose rate from 15 μsv/h to 120 μsv/h at patient s’ release time, the calculated mean and median dose values of family members were 0.45 mSv and 0.28 mSv, respectively. Moreover, almost all the family members doses were measured to be less than the dose constraint of 5 mSv recommended by Basic Safety Standards. Considering the influence parameters such as patient dose rate and administrated activity, the total effective dose of family members were calculated by TEDE and NRC formulas and compared with those of experimental results. The results indicated that, it is fruitful to use the quantitative calculations for releasing patients treated with I-131 and correct estimation of patient s’ family doses.
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Effective dose is used as a reference limit to measure the total health risk from the radiation exposure to the body. Over exceeding the limit of effective dose could result in a high possibility of developing radiation-induced cancer. The aim of this research is to measure the effective dose to patients and workers during the diagnostic X-ray procedure in UTHM Health Centre. Effective dose to radiation workers is estimated by calculating the radiation dose in the controlled and supervised area. Pen dosimeter is used for dose measurement. The pen was placed at numerous spots inside the radiation facility to study the effective dose with respect to distance and shielding materials present. An ANSI patient-equivalent phantom was developed to simulate the real patient absorption and scattering during X-ray diagnostic examination for extremity, chest, skull, and lumbar. Results show that the lowest annual effective dose is measured by the door leaf which is 3.83 mSv per year while the highest is on the erect bucky stand that is 48.10 mSv per year. The annual effective dose in the supervised area and the ESE values of ANSI patient-equivalent phantoms (in mR per projection) is found to be under the reference dose limit. This finding suggested that the radiation protection principles are obeyed, with the effective dose to the radiation workers as well as patients is in the range of reference dose limit.
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Absorbed doses to family members of patients treated with (131)I were measured using thermoluminescent dosimeters worn on the chest. Twenty-two patients with thyroid cancer were hospitalized for 2 d for treatment with 3,700-7,400 MBq, and 18 hyperthyroid patients were treated on an outpatient basis with 200-600 MBq. Doses were measured over periods of 15-21 d following the administration of radioiodine in 35 partners and 38 children, aged 4 mo to 25 y. These results were correlated with dose rate measurements performed with an ionization chamber, and residual thyroid uptake was assessed by scintigraphy over the same period. In the cancer group, the residual activity in thyroid remnants was less than 50 MBq in all cases at day 4 following treatment and decayed with a mean half-life of 2.2 (SD: 0.8) d. The dose measured with thermoluminescent dosimeters was lower than 0.5 mSv in all partners and children. In the hyperthyroid group, the effective half-life averaged 6.2 (SD: 1.2) d. The median of the doses measured in partners and children were 1.04 mSv (range: 0.05-5.2) and 0.13 mSv (range: 0.04-3.1), respectively. Fifteen children (88%) received less than the dose constraint of 0.5 mSv. The ICRP recommend an annual limit of 1 mSv for the members of the public. In addition, dose constraints (for example: 0.5 mSv) should be complied with whenever possible. The recommended dose limits are generally well met among family members of patients treated with 1311 for cancer. The higher doses measured in hyperthyroid patients, compared to thyroid cancer patients, relate to a higher (131)I retention by the gland and justify more extended and stringent restriction periods, based on residual thyroid activity.
Radioiodine therapy
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1701 Objectives The objectives of this study are to measure the ambient radiation and patient dose during whole body bone scintigraphy, thyroid and renal scan procedures. Methods Staff radiation exposure personnel were calculated as a function of administered dose distance from the patient and at different times after the administration and workload. A calibrated survey meter and thermoluminancent dosimeters (TLDs- GR200A) were used to measure the ambient dose and staff dose, respectively. Prior to measurements, all TLD were calibrated in terms of air kerma free-in-air under reproducible reference condition using 99m Tc with activity 10 mCi (370 MBq). Quality control performed before administration of the radiopharmaceutical and doses are carefully calculated. All scan procedures were performed using MiE single head gamma camera (Orbiter 37 Gamma camera) after administration of 20 mCi, 4 mCi and 5 mCi of 99mTc. Results The average ambient dose equivalent rate equal to about 12, 25 and 10 μSv/h was obtained at distance of 1 m, at 1.3 m from patient during bone, renal and thyroid scan respectively. Injection room and hot lab has ambient dose equivalent rates of 1.0 and 30 μSv/h at the same order. The maximum dose were recorded at the reception area equal to 180 μSv/h. Staff may exposed to a dose range from 8.0 to 12.5 mSv annually. Knowledge of ambient dose values is crucial in order to determine exposure personnel who may limit the time spent at high dose areas. The dose values are within the safety limit in the light of the current practice. Conclusions Although, the ambient dose is high compared to previous studies, the staff exposure was below the annual dose limits in the light of the current workload. Appropriate isolation of the patients, training of staff and a strict compliance with the established radiation safety standards are crucial in order to avoid unnecessary radiation exposure. Research Support College of Applied Medical Sciences Research Centre and Deanship of Scientific Research at King Saud University
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Kerma
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Occupational radiation doses in interventional radiology can potentially be high. Therefore, reliable methods to assess the effective dose are needed. In the present work, the relationship between the personal dose equivalent, H(p)(10), the reading of a personal dosimeter and the effective dose of the radiologist were studied using Monte Carlo simulations. In particular, the protection provided by a lead apron was investigated. Emphasis was placed on sensitivity of the results to changes in irradiation conditions. In our simulations a 0.35 mm thick lead apron and thyroid shield reduced the effective dose, on average, by a factor of 27 (the range of these data was 15-41). Without the thyroid shield the average reduction factor was 15 (range 6-22). The reduction sensitively depended on the projection and the X-ray tube voltage. The dosimeter reading, when the dosimeter was worn above the apron and a thyroid shield was used, overestimated the effective dose on average by a factor of 130 (range 44-258) when the dosimeter was located on the breast closest to the primary X-ray beam. Without the thyroid shield the average overestimation was 69 (range 32-127). If the dosimeter was worn under the apron its reading generally underestimated the effective dose (on average by 20% with the thyroid shield). Our study indicates that, even though large variations are present, the often used conversion coefficient from the dosimeter reading above the apron to the effective dose, around 1/30, generally overestimates the effective dose by a factor of two or more.
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Purpose: The precise determination of organ mass (mth) and total number of disintegrations within the thyroid gland () are essential for thyroid absorbed-dose calculations for radioiodine therapy. Nevertheless, these parameters may vary according to the method employed for their estimation, thus introducing uncertainty in the estimated thyroid absorbed dose and in any dose–response relationship derived using such estimates. In consideration of these points, thyroid absorbed doses for Graves’ disease (GD) treatment planning were calculated using different approaches to estimating the mth and the . Methods: Fifty patients were included in the study. Thyroid131I uptake measurements were performed at 2, 6, 24, 48, 96, and 220 h postadministration of a tracer activity in order to estimate the effective half-time (Teff) of 131I in the thyroid; the thyroid cumulated activity was then estimated using the Teff thus determined or, alternatively, calculated by numeric integration of the measured time-activity data. Thyroid mass was estimated by ultrasonography (USG) and scintigraphy (SCTG). Absorbed doses were calculated with the OLINDA/EXM software. The relationships between thyroid absorbed dose and therapy response were evaluated at 3 months and 1 year after therapy. Results: The average ratio (±1 standard deviation) betweenmth estimated by SCTG and USG was 1.74 (±0.64) and that between obtained by Teff and the integration of measured activity in the gland was 1.71 (±0.14). These differences affect the calculated absorbed dose. Overall, therapeutic success, corresponding to induction of durable hypothyroidism or euthyroidism, was achieved in 72% of all patients at 3 months and in 90% at 1 year. A therapeutic success rate of at least 95% was found in the group of patients receiving doses of 200 Gy (p = 0.0483) and 330 Gy (p = 0.0131) when mth was measured by either USG or SCTG and was determined by the integration of measured 131I activity in the thyroid gland and based on Teff, respectively. No statistically significant relationship was found between therapeutic response and patients’ age, administered 131I activity (MBq), 24-h thyroid 131I uptake (%) or Teff (p ≥ 0.064); nonetheless, a good relationship was found between the therapeutic response and mth (p ≤ 0.035). Conclusions: According to the results of this study, the most effective thyroid absorbed dose to be targeted in GD therapy should not be based on a fixed dose but rather should be individualized based on the patient'smth and . To achieve a therapeutic success (i.e., durable euthyroidism or hypothyroidism) rate of at least 95%, a thyroid absorbed dose of 200 or 330 Gy is required depending on the methodology used for estimating mth and .
Radioiodine therapy
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Presented paper describes the results of the individual doses measurements for ionizing radiation, carried out by the Laboratory of Individual and Environmental Doses Monitoring (PDIS) of the Central Laboratory for Radiological Protection in Warsaw (CLOR) for the medical staff employees in several nuclear medicine (NM) departments across Poland. In total there are48 NM departments in operation in Poland [1] (consultation in Nuclear Atomic Agency). Presented results were collected over the period from January 2011 to December 2011 at eight NM departments located in Krakow, Warszawa (two departments), Rzeszow (two departments), Opole, Przemysl and Gorzow Wielkopolski. For radiation monitoring three kinds of thermo luminescence dosimeters (TLD) were used. The first TLD h collected information about whole body (C) effective dose, the second dosimeter was mounted in the ring (P) meanwhile the third on the wrist (N) of the tested person. Reading of TLDs was performed in quarterly periods. As a good approximation of effective and equivalent dose assessment of operational quantities both the individual dose equivalent Hp(10) and the Hp(0.07) were used. The analysis of the data was performed using two methods The first method was based on quarterly estimations of Hp(10)q and Hp(0.07)q while the second measured cumulative annual doses Hp(10)a and Hp(0.07)a. The highest recorded value of the radiation dose for quarterly assessments reached 24.4 mSv and was recorded by the wrist type dosimeter worn by a worker involved in source preparation procedure. The mean values of Hp(10)q(C type dosimeter) and Hp(0.07)q (P and N type dosimeter) for all monitored departments were respectively 0.46 mSv and 3.29 mSv. There was a strong correlation between the performed job and the value of the received dose. The highest doses always were absorbed by those staff members who were involved in sources preparation. The highest annual cumulative dose for a particular worker in the considered time period was 4.22 mSv for Hp(10)a and 67.7 mSv for Hp(0.07)a. In 2011 no case of exceeding the allowed dose limits was noted.
Optically stimulated luminescence
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