Leak and Scattering Assessment by Optically Stimulated Luminescence Dosimetry in a Helical Linear Accelerator / Valoración de Fuga y Dispersión por medio de Dosimetría de Luminiscencia Estimulada Ópticamente (OSL) en un Acelerador Lineal Helicoidal

Radiation absorbed doses to organs outside the radiation therapy treatment beam can be significant and therefore of clinical interest. Two sets of out-of-beam measurements were performed measuring the leak dose and the scattered dose, at 5 points within the accelerator components (accelerator tube and collimator) and at 21 points on the equipment and surroundings based on a positioning scheme. For this purpose, 52 Optically Stimulated Luminescence (OSL) dosimeters were used in a latest generation helical linear accelerator. Of the 200 cGy fired at a cheese-like phantom, 0.332% of the out-of-beam dose contribution was found to come from the leak and 0.784% was transformed into scattering. For these dose values, estimates of the risk of second tumors in long-term survivors indicate a reduced probability of acquiring a second secondary radiation malignancy, based on information from the 1990 BEIR Committee report.

La dosis absorbida de radiación a órganos fuera del haz de tratamiento de radioterapia puede ser significativa y, por lo tanto, de interés clínico. Se realizaron dos sets de mediciones fuera del haz para determinar la dosis de fuga y la dosis dispersa, en 5 puntos dentro de los componentes del acelerador (tubo de aceleración y colimador) y 21 puntos en el equipo y alrededores basado en un esquema de posicionamiento. Para este fin se utilizaron 52 dosímetros de luminiscencia estimulada ópticamente (OSL, Optically Stimulated Luminescence), en un acelerador lineal helicoidal de última generación. De los 200 cGy disparados a un maniquí tipo queso, se encontró que el 0.332% de la contribución de dosis fuera del haz provenía de la fuga y 0.784% se transforma en dispersión. Para estos valores de dosis, las estimaciones del riesgo de segundos tumores en los supervivientes a largo plazo indican una reducida probabilidad de contraer una segunda malignidad por radiación secundaria, según la información del informe del Comité BEIR de 1990.

Dosimetry in CBCT with Different Protocols: Emphasis on Small FOVs Including Exams for TMJ

Abstract This study aimed to estimate the absorbed dose in cone beam computed tomography (CBCT) exams according to different exposure parameters and size and position of the field of view (FOV). In addition was compared the absorbed dose of two smaller FOV scans with that of a larger FOV scan for evaluation of temporomandibular joint (TMJ), as it is a bilateral structure. CBCT scans were obtained on OP300 Maxio unit varying scanning mode (standard, high and endo) as well as size (5x5, 6x8 and 8x15 cm) and positioning of FOV. With a small FOV, different areas were scanned (maxilla or mandible, anterior or posterior and TMJ). Absorbed doses were determined using thermoluminescent dosimeters on the skin surface of sensitive organs of an anthropomorphic phantom. Endo mode showed the highest dose, followed by the high and standard modes in all FOV positions. With small FOV, doses were higher in the posterior region, especially in the mandible. Dose reduction occurred when small FOVs were used, but it was not proportional to FOV size reduction. For TMJ, the dose in a single acquisition with large FOV was greater than two acquisitions with small FOV, but lower than two acquisitions with medium FOV (6x8 cm). In conclusion, scanning mode, size and FOV position have great influence on the absorbed dose. Small FOV decreases the dose, but there is no linear relation between FOV size and dose. For bilateral exams of TMJ, double acquisition with small FOVs produces decrease in absorbed dose relative to a large FOV.

Resumo O objetivo deste estudo foi estimar a dose absorvida em exames de tomografia computorizada de feixe cônico (TCFC) de acordo com diferentes parâmetros de exposição, tamanho e posição do campo de visão (FOV, do inglês field of view). Além disso, comparou-se a dose absorvida em uma única aquisição com FOV grande com aquela em duas aquisições com FOVs menores para avaliação de estruturas bilaterais como a articulação temporomandibular (ATM). As aquisições de TCFC foram obtidas no aparelho OP300 Maxio, variando o modo de aquisição (standard, high e endo), bem como o tamanho (5x5, 6x8 e 8x15 cm) e o posicionamento do FOV. Com o FOV pequeno, foram escaneadas diferentes áreas (maxila ou mandíbula, anterior ou posterior e ATM). As doses absorvidas foram determinadas por meio da utilização de dosímetros termoluminescentes na superfície da pele em órgãos sensíveis de um phantom antropomórfico. O modo endo mostrou a dose mais alta, seguido pelos modos high e standard em todas as posições dos FOVs. Com um FOV pequeno, as doses foram maiores na região posterior, especialmente na mandíbula. A redução da dose ocorreu quando foram utilizados pequenos FOVs; contudo, essa redução não foi proporcional à redução do tamanho do FOV. Para a ATM, a dose em uma única aquisição com FOV grande foi maior que duas aquisições com FOV pequeno, porém inferior à dose de duas aquisições com FOV médio (6x8 cm). Em conclusão, o modo de aquisição, o tamanho e a posição do FOV têm grande influência na dose absorvida. FOVs pequenos apresentaram doses mais baixas em relação aos FOVs grandes, entretanto não há uma relação linear entre o tamanho do FOV e a dose absorvida. Para estruturas bilaterais como a ATM, a dupla aquisição com FOV pequeno representa uma diminuição na dose absorvida em relação a uma aquisição com FOV grande.

Radiation dose to the thyroid, eyes and parotid glands of patients undergoing intra-oral radiographic procedures in a teaching hospital in Ibadan, Oyo state Nigeria

Background: Intraoral radiographs are believed to deliver low doses to patients, thus little work has been done in this regards. Considering the increment in the number of patients reporting for the examination and the probability of delayed somatic effects for accumulated low doses of X-irradiation, it is expedient to determine the doses to three critical organs eye, thyroid and parotid that are at risk during exposure

Materials and Methods: Thermoluminescent dosimeters was used to measure Entrance Surfaces Doses [ESDs] to the thyroid, eye and parotids salivary gland of 40 adult patients undergoing intra-oral radiographic examination at University College Hospital, [UCH] Ibadan, Oyo state

Results: Results indicated entrance surface doses [ESD] ranged between 0.0447 mGy to 0.3898 mGy to the thyroid, 0.0742 mGy to 0.3989 mGy to eye and 0.0467 mGy to 0.4164 mGy to the parotids for the period of study. The mean ESD +/- SD to the thyroid, parotids and eyes for male were 0.179810.081, 0.215510.109 and 0.219710.081 mGy with the female patients 0.195710.084, 0.209110.081 and 0.228010.113 mGy respectively. No statistically significant difference was found between these means

Conclusion: The doses obtained in this study were lower than the documented threshold that could cause significant damage in the various organs, not undermining stochastic effect of radiation. This study will assist in setting Diagnostic Reference Level [DRL] for intraoral radiographic imaging in Nigeria

Dosimetric Study of Biliary Stent Loaded with RadioactiveI Seeds / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>A novel radioactive 125I seed-loaded biliary stent has been used for patients with malignant biliary obstruction. However, the dosimetric characteristics of the stents remain unclear. Therefore, we aimed to describe the dosimetry of the stents of different lengths - with different number as well as activities of 125I seeds.</p><p><b>METHODS</b>The radiation dosimetry of three representative radioactive stent models was evaluated using a treatment planning system (TPS), thermoluminescent dosimeter (TLD) measurements, and Monte Carlo (MC) simulations. In the process of TPS calculation and TLD measurement, two different water-equivalent phantoms were designed to obtain cumulative radial dose distribution. Calibration procedures using TLD in the designed phantom were also conducted. MC simulations were performed using the Monte Carlo N-Particle eXtended version 2.5 general purpose code to calculate the radioactive stent's three-dimensional dose rate distribution in liquid water. Analysis of covariance was used to examine the factors influencing radial dose distribution of the radioactive stent.</p><p><b>RESULTS</b>The maximum reduction in cumulative radial dose was 26% when the seed activity changed from 0.5 mCi to 0.4 mCi for the same length of radioactive stents. The TLD's dose response in the range of 0-10 mGy irradiation by 137Cs γ-ray was linear: y = 182225x - 6651.9 (R2=0.99152; y is the irradiation dose in mGy, x is the TLDs' reading in nC). When TLDs were irradiated by different energy radiation sources to a dose of 1 mGy, reading of TLDs was different. Doses at a distance of 0.1 cm from the three stents' surface simulated by MC were 79, 93, and 97 Gy.</p><p><b>CONCLUSIONS</b>TPS calculation, TLD measurement, and MC simulation were performed and were found to be in good agreement. Although the whole experiment was conducted in water-equivalent phantom, data in our evaluation may provide a theoretical basis for dosimetry for the clinical application.</p>

Staff dose assessment from coronary angiography

Interventional cardiology procedures such as coronary angiography [CA] and percutaneous transluminal coronary angiography [PTCA] has been increased recent years. The purpose of this study was to measurement of effective dose to cardiology staffs who operate near the patient and are exposed to non-uniform radiation field due to patient scattered radiation. This study was performed in angiography department of Fatemeh Zahra Hospital as specialized hospital of heart in Sari, the Northern city of Iran for two months and 687 interventional cardiology procedures were studied. Doses were recorded with thermoluminescence dosimeter [TLD] for 10 cardiologists, 10 nurses and 1 radiology technologist and the effective dose were estimate using the Niklason algorithm. Mean annual effective dose [microSv] to cardiologist and nurses and radiology technologist from interventional cardiology procedures were 535.57 [68.6 - 1984.8] microSv and 153.7 [59.5 - 277.2] microSv respectively. Mean effective dose [microSv] per interventional cardiology procedure for cardiologist and nurses and radiology technologist were 2.123 and 0.274 microSv respectively. The results indicate large variation in radiation exposure between staffs. No correlation was found between the number of procedures and effective dose. None of the annual effective dose appear to exceed the annual effective dose limit of 20 mSv

Design of homogeneous and heterogeneous human equivalent thorax phantom for tissue inhomogeneity dose correction using TLD and TPS measurements

The purpose of this study is to fabricate inexpensive in-house low cost homogeneous and heterogeneous human equivalent thorax phantom and assess the dose accuracy of the Treatment Planning Systems [TPS] calculated values for different lung treatment dosimetery. It is compared with Thermoluminescent Dosimeter [TLD] measurement. Homogeneous and heterogeneous thorax human equivalent phantoms were fabricated using bee's wax [density=0.99 g/cm[3]] as a tissue simulating material, with inserts of cork [density=0.2 g/cm[3]] and Teflon [density=2 g/cm[3]] as lung and spine simulating material respectively. Lithium fluoride [LiF] TLD capsules were irradiated for different thoracic tumor treatment techniques using the locally fabricated homogeneous and heterogeneous phantoms. The 3D TPS calculated values of homogeneous and heterogeneous phantoms were compared with TLD measured values. Experiments were carried out for different thoracic tumour treatment techniques for small and larger field sizes and also with and without wedge for Cobalt - 60 photon beams. Plato TPS were used to calculate the inhomogeneity for the homogeneous and heterogeneous phantoms. TLD and 3D TPS calculated values were found to have deviation of +/- 5%. Both the homogeneous and heterogeneous phantoms has proved to be a valuable tools in the development and implementation of external beam radiotherapy [EBRT] in the clinical thorax region and in the verification of absolute dose and dose distributions in the regions of clinical and dosimetric interest

Dosimetric characterization of a high dose rate 192I source for brachytherapy application using Monte Carlo simulation and benchmarking with thermoluminescent dosimetry

The purpose of this project was to derive the brachytherapy dosimetric functions described by American Association of Physicists in Medicine [AAPM] TG-43 U1 based on high dose rate [192]I sources. The method utilized included both simulation of the designed Polymethyl methacrylate [PMMA] phantom using the Monte Carlo of MCNP4C and benchmarking of the simulation with thermoluminescent [TL] dosimeters. The obtained results for the radial dose function and anisotropy function showed nominal errors of less than 3% between TL measurements and the MCNP4C results. It may be concluded that due to small observed errors and the large uncertainty associated with the high dose gradients near the source point the simulation results can be used for dose estimation

Comparison of effective dose for imaging of mandible between multi-detector CT and cone-beam CT

PURPOSE: The aim of this study was to compare the effective dose for imaging of mandible between multi-detector computed tomography (MDCT) and cone-beam computed tomography (CBCT). An MDCT with low dose technique was also compared with them. MATERIALS AND METHODS: Thermoluminescent dosimeter (TLD) chips were placed at 25 organ sites of an anthropomorphic phantom. The mandible of the phantom was exposed using 2 different types of MDCT units (Somatom Sensation 10 for standard-dose MDCT, Somatom Emotion 6 for low-dose MDCT) and 3 different CBCT units (AZ3000CT, Implagraphy, and Kavo 3D eXaM). The radiation absorbed dose was measured and the effective dose was calculated according to the ICRP 2007 report. RESULTS: The effective dose was the highest for Somatom Sensation 10 (425.84 microSv), followed by AZ3000CT (332.4 microSv), Somatom Emotion 6 (199.38 microSv), and 3D eXaM (111.6 microSv); it was the lowest for Implagraphy (83.09 microSv). The CBCT showed significant variation in dose level with different device. CONCLUSION: The effective doses of MDCTs were not significantly different from those of CBCTs for imaging of mandible. The effective dose of MDCT could be markedly decreased by using the low-dose technique.

Niveles de dosis en radiología convencional / Radiation doses in conventional radiology

Se ha medido la dosis en la superficie de entrada de ojos, tiroides y gónadas en pacientes sometidos a estudio de radiografía de tele de tórax mediante dosimetría termoluminiscente. Se usaron 5 dosímetros en cada una de las exploraciones; encontrándose los siguientes rangos de dosis: 20 mGy a 350 mGy. En el caso de los pacientes pediátricos se propone incluir la información de las dosis recibidas en su cartilla de vacunación con el fin de hacer un seguimiento de los posibles efectos nocivos en su salud.

Doses have been measured at the entrance surface of eyes, thyroid and gonads in patients undergoing chest x-ray studies, using thermo-luminiscent dosimetry. Five dosimeters were used in each investigation, and doses ranged from 20 mGy to 350 mGy. In the case of pediatric patients, it is proposed that dose information from diagnostic examinations is included in the vaccination chart in order to correlate with findings at follow-up.

[Evaluation of radiation dose received by operating room personnel during radiological procedures]

Utilization of ionizing radiation in some surgery operations [especially orthopedic operations] is inevitable. One of the main occupational hazards of physicians and other personnel could be radiation exposure risks. This study aimed to evaluate the exposure doses received by operating room personnel in such surgery operations. 30 personnel of operation room in university affiliated hospitals of Hamadan city [excluding physicians and nurses] were studied as they received radiation doses. 3 TLD [thermoluminescent dosimet ers] chips were fixed on the apron of each staff member. To estimate the high risk examinations, staff members also completed a questionnaire about the type and number of the radiological examinations that they had participated. Minimum and maximum level of doses received by the participants were between 0.24 and 0.56 mSv in a four month period. Therefore, amount of annual doses received by the personnel would be between 0.73 and 1.7 mSv, respectively [without reduction of background radiation]. As the accuracy of TL dosimeters is normally about 0.1 mSv; therefore, it can be claimed that the received doses by the personnel was very low and comparable with background radiation. The results indicated that the radiation doses received by operating room personnel were very low. They were less than maximum predicted doses reported by the International Commission of Radiation Protection. However, the use of dose recording systems for awareness about absorbed doses beyond permitted limits is necessary

Shielding property of different prosthetic materials to shield radiation of (125)I seed / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigation the shielding property to (125)I of several different prosthetic materials used in clinical when prostheses are used as carriers of (125)I seed in tumor treatment.</p><p><b>METHODS</b>(125)I seeds were taken as the radiation sources to establish a model in vitro and the radiation doses were measured by thermoluminescent dosemeters (TLD). The shielding property of titanium plate, cochrome plate, and poly methyl methacrylate (PMMA) plate were detected, calculated and compared with that of plumbum plate in the control group.</p><p><b>RESULTS</b>The radiation doses of the radiation source at 10 mm distance through the following materials were measured, and the results are 2.805 mGy (0.09 mm thick titanium plate), 1.082 mGy (0.48 thick titanium plate), 0.390 mGy (0.41 mm thick cochrome plate), and 0.261 mGy (0.67 mm's cochrome plate), and 2.885 mGy (1.685 mm thick PMMA plate).</p><p><b>CONCLUSIONS</b>The shield property of cochrome is optimal. The poly methyl methacrylate behaves to some extend as a shield to the (125)I seed which can shield the radiation as the effects of plumbum when adopted together with the 0.557 mm's (or more) titanium plate.</p>

Comparative dosimetry of dental cone-beam computed tomography and multi-slice computed tomography for oral and maxillofacial radiology / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To compare the effective radiation dose levels of cone beam computed tomography (CBCT) with those of multi-slice computed tomography (MSCT) when scanning the same maxillofacial regions.</p><p><b>METHODS</b>The effective doses of 2 CBCT (NewTom 9000 and DCT Pro) and 1 MSCT (bright speed edge select 8 slice) scanners were calculated using thermoluminescent dosimeters (TLD) that were placed in a head and neck phantom, and expressed according to the International Commission on Radiation Protection (ICRP) 2007 guidelines.</p><p><b>RESULTS</b>Effective dose values ranged from 41.8 to 249.1 µSv for CBCT. The doses of MSCT scanning for maxilla, mandible and maxilla + mandible were 506.7, 829.9 and 1066.1 µSv, respectively. Dose levels of scanning only for maxilla or mandible were significantly lower than those for maxilla + mandible.</p><p><b>CONCLUSIONS</b>When scanning the same maxillofacial regions, the dose levels for NewTom 9000 and DCT Pro CBCT images were lower than those for Bright speed edge select 8 slice MSCT images. Dose levels reduction could be obtained when smaller regions were scanned.</p>

Influência da dependência energética de dosímetros termoluminescentes na medida da dose na entrada da pele em procedimentos radiográficos / Influence of thermoluminescent dosimeters energy dependence on the measurement of entrance skin dose in radiographic procedures

OBJETIVO: O objetivo do presente trabalho foi avaliar a influência da dependência energética de materiais termoluminescentes na determinação da dose na entrada da pele de pacientes submetidos a exames radiográficos (radiologia geral, mamografia e radiologia odontológica). MATERIAIS E MÉTODOS: Três diferentes materiais termoluminescentes foram utilizados: LiF:Mg,Ti, LiF:Mg,Cu,P e CaSO4:Dy. Estes materiais foram expostos a fontes padronizadas de radiação X e gama, e a feixes clínicos de raios X. RESULTADOS: As curvas de calibração e de dependência energética foram obtidas. Todos os materiais apresentaram resposta linear em função do kerma no ar. Com relação à dependência energética, as amostras de CaSO4:Dy e LiF:Mg,Ti mostraram maior variação da resposta termoluminescente em função da energia efetiva do feixe de radiação. CONCLUSÃO: Os materiais testados mostraram desempenho adequado para a detecção da radiação X em feixes padronizados e clínicos. Embora as amostras de CaSO4:Dy e LiF:Mg,Ti apresentem dependência energética significativa no intervalo de energia considerado, este materiais podem ser utilizados para medição da dose de entrada na pele se fatores de correção apropriados forem utilizados.

OBJECTIVE: This study was aimed at evaluating the influence of the energy dependence of thermoluminescent materials on the determination of entrance skin dose in patients submitted to conventional radiographic studies (general radiology, mammography and dental radiology). MATERIALS AND METHODS: Three different thermoluminescent materials were utilized: LiF:Mg,Ti, LiF:Mg,Cu,P and CaSO4:Dy. These materials were exposed to standardized sources of X and gamma radiation and clinical X-ray beams. RESULTS: Calibration and energy dependence curves were obtained. All the materials showed a linear response as a function of the air kerma. As far as energy dependence is concerned, the CaSO4:Dy and LiF:Mg,Ti samples showed the greatest variation on thermoluminescent responses as a function of the effective radiation beam. CONCLUSION: The tested materials showed an appropriate performance for detecting X radiation on standard and clinical X-ray beams. Although CaSO4:Dy and LiF:Mg,Ti samples present a significant energy dependence in the considered energy range, these materials can be utilized for measuring entrance skin doses, provided appropriate correction factors are applied.

Clay as Thermoluminescence Dosemeter in Diagnostic Radiology Applications

As part of efforts to isolate and utilize local and naturally occurring materials for development of thermoluminescece dosemeters and other technologies; an earlier report had shown that Nigerian clay showed prospects of utility as a thermoluminescence dosemeter (TLD). This paper reports the investigation of the basic thermoluminescence properties of clay at x-rays in the diagnostic radiology range; including dose monitoring in abdominal radiography. Clay sourced from Calabar; Nigeria; was tested for thermoluminescence response after irradiation at diagnostic radiology doses; including application in abdominal radiography dose monitoring in a clinical setting. Results show that thermoluminescence (TL) output in natural clay is very low; but demonstrates enhanced performance with the addition of common salt. Specific TL characteristics of good repeatability for individual and batched pellets (variability index of 3.08) and a high degree of trap emptying were observed. It had a glow curve peak at 275 C; with traces of spurious thermoluminescence emission at the reader anneal temperature. There was evidence of good batch homogeneity ( 30) and a similar pattern of dose absorption in abdominal radiography with commercial Lithium Fluoride (LiF TLD-100). A high fading rate (over 30in twelve hours) and low sensitivity (12 times less than LiF TLD-100) however; signal the unacceptability of clay as aTLD in diagnostic radiology in the forms studied. Clay demonstrates poor TL response at diagnostic radiology doses. However; it's water absorbing property offers a means of overcoming the hygroscopic nature of common salt. This could be explored to improve the use of sodium chloride as a radiation detector

Avaliação da dose no reto em pacientes submetidas a braquiterapia de alta taxa de dose para o tratamento do câncer do colo uterino / Rectal dose assessment in patients submitted to high-dose-rate brachytherapy for uterine cervix cancer

OBJETIVO: O objetivo deste trabalho foi desenvolver um sistema dosimétrico termoluminescente capaz de avaliar as doses administradas ao reto de pacientes submetidas a braquiterapia de alta taxa de dose para o tratamento do câncer do colo uterino. MATERIAIS E MÉTODOS: O material termoluminescente utilizado para a avaliação da dose no reto foi o LiF:Mg,Ti,Na na forma de pó. O pó foi separado em pequenas porções de 34 mg, que foram acomodadas em um tubo capilar. Este tubo foi colocado em uma sonda retal, que era introduzida no reto da paciente. RESULTADOS: As doses administradas ao reto de seis pacientes submetidas a braquiterapia de alta taxa de dose para o tratamento do câncer do colo uterino foram avaliadas com dosímetros termoluminescentes e apresentaram boa concordância com os valores planejados, com base em duas radiografias ortogonais da paciente, imagens ântero-posterior e lateral. CONCLUSÃO: O sistema de dosimetria termoluminescente utilizado no presente trabalho é simples e de fácil utilização quando comparado a outros métodos de dosimetria do reto. Ele mostrou-se eficiente na avaliação da dose no reto de pacientes submetidas a braquiterapia de alta taxa de dose para o tratamento do câncer do colo uterino.

OBJECTIVE: The present study was aimed at developing a thermoluminescent dosimetric system capable of assessing the doses delivered to the rectum of patients submitted to high-dose-rate brachytherapy for uterine cervix cancer. MATERIALS AND METHODS: LiF:Mg,Ti,Na powder was the thermoluminescent material utilized for evaluating the rectal dose. The powder was divided into small portions (34 mg) which were accommodated in a capillary tube. This tube was placed into a rectal probe that was introduced into the patient's rectum. RESULTS: The doses delivered to the rectum of six patients submitted to high-dose-rate brachytherapy for uterine cervix cancer evaluated by means of thermoluminescent dosimeters presented a good agreement with the planned values based on two orthogonal (anteroposterior and lateral) radiographic images of the patients. CONCLUSION: The thermoluminescent dosimetric system developed in the present study is simple and easy to be utilized as compared to other rectal dosimetry methods. The system has shown to be effective in the evaluation of rectal doses in patients submitted to high-dose-rate brachytherapy for uterine cervix cancer.

Radioiodoterapia do carcinoma diferenciado da tireoide: impacto radiológico da liberação hospitalar de pacientes com atividades entre 100 e 150 mCi de iodo-131 / Radioiodine therapy of differentiated thyroid cancer: radiologic impact of out-patient treatment with 100 to 150 mCi Iodine-131 activities

OBJETIVO: Determinar exposições decorrentes da radioiodoterapia ambulatorial do carcinoma diferenciado da tireoide (CDT) sobre os familiares dos pacientes e o meio ambiente. MÉTODOS: Administraram-se 100 a 150 mCi de (131I)NaI para tratamento ambulatorial de 20 pacientes com CDT. Monitorizaram-se com dosímetros termoluminescentes as doses de radiação recebidas por familiares (n = 27) e potenciais de dose nas residências. Também foram monitorizadas contaminação de superfície e rejeitos radioativos. RESULTADOS: Registraram-se doses < 1,0 mSv em 26 acompanhantes e 2,8 mSv em um caso, inferiores ao aceitável para exposições médicas (5,0 mSv/procedimento). Excetuando-se o quarto dos pacientes (média = 0,69 mSv), determinou-se potencial de dose nas residências < 0,25 mSv. A contaminação de superfícies (4,2 Bq.cm-2) não ultrapassou níveis de liberação, sem representar riscos mesmo em simulações do pior cenário. Os rejeitos radioativos tiveram volume de 2,5 litros e atividade estimada em 90 µCi (média = 4,5 µCi/paciente). CONCLUSÕES: Não foi constatado impacto radiológico ao meio ambiente ou aos familiares de pacientes tratados ambulatorialmente com 100 a 150 mCi de iodo-131 e acompanhados por profissionais qualificados.

PURPOSE:To evaluate exposure and dosimetry to family members and environment due to outpatient radioiodine therapy of differentiated thyroid carcinoma. METHODS: Twenty patients were treated with 100-150mCi of iodine-131 on an out-patient basis. Family members dosimetry (n = 27) and potential doses inside the house were measured with thermoluminescent dosimeters. Surface contamination and radioactive wastes were also monitored. RESULTS: Less than 1.0 mSv doses were found in 26 co-habitants and 2.8 mSv in a single case (inferior to the acceptable value of 5.0 mSv/procedure). Potential doses in the houses were inferior to 0.25 mSv, excluding the patients bedroom (mean value = 0.69 mSv). Surface contamination (mean = 4.2 Bq.cm-2) were below clearance levels. Radioactive wastes generated had a volume of 2.5 liters and a total activity estimated in 90 µCi, with a calculated exposure close to the background radiation levels. CONCLUSIONS: No radiological impact was detected after iodine therapy with 100-150 mCi on an out-patient basis followed by experienced professionals.

Determination of absorbed dose of organs [thyroid, sternum, cervical vertebra] in thyroid cancer patients following radioiodine therapy

In patients with thyroid carcinoma, radiation absorbed doses of the thyroid and surrounding tissues is important to weigh risk and benefit considerations. In nuclear medicine, the accuracy of absorbed dose of internally distributed radionuclides is estimated by different methods such as MIRD and direct method using TLD. The aim of this study is using TLD and a phantom to determine the amount of cumulated activity in thyroid and surrounding tissues. Thermoluminescent dosimeter [TLD] measurements were performed on 27 patients on the skin over the thyroid, sternum and cervical vertebra. There were 5 TLDs for each organ which they were taken after 4, 8, 12, 20 and 24 hr. To calculate the amount of activity in the thyroid a head and neck phantom with a source of 10 mCi of [131] I was used. Several TLDs were placed putted on the surface of thyroid on phantom [similar to patients] for 24 hr and then compared the dose of phantom and patients followed by calculation of the activity in patient's thyroid. TLD measurements showed cumulated radiation absorbed doses [cGy] of 315.6, 348.1 and 361.9 for thyroid with administration of 100, 150 and 175 mCi of [131] I, respectively. For sternum the values found to be 201.5 cGy, 275.2 cGy and 242.6 cGy. For cervical vertebra results were 311.5 cGy, 184.1 cGy and 325.9 cGy. The average of measurements was 33.3 cGy using of TLDs on phantom and absorbed activity in thyroid were 94.9, 104.6 and 108.8 mCi in 24 hr for mentioned doses administration. In this work a method to obtain the absorbed activity in the thyroid and other surrounding tissues is described. By this method, the amount of [131] I needed for each patient also could be determined. The results of this work can be used in estimation of absorbed dose in thyroid and other organs using of MIRD method

Radiation doses to contralateral breast during irradiation of breast cancer

External beam radiotherapy is being used regularly to treat the breast malignancy postoperatively. The contribution of collimator leakage and scatter radiation the dose, as well as the dose of the treatment fields, to contralateral breast is of concern because of high radio sensitivity of breast tissue for carcinogenesis. This becomes more important when the treated cancer breast patient is younger than 45 years and therefore the contralateral breast must be treated as organ at risk. Quantification of contralateral dose during primary breast irradiation is helpful to estimate the risk and reduce scatter se to the contralateral breast. In present study contralateral breast dose was measured in 30 cancer breast patients undergoing extenal beam therapy. Postoperative radiotherapy was delivered by medial and lateral tangential fields daily, in addition to supraclavicle field with 200cGy/F to a total dose of 5000cGy in 25 fractions. A themoluminescence dosimeter chips were employed for these measurements. TLD chips were put on the surface of skin of contralateral breast, on the level of nipple, with and without shield, TLD chips were removed and measured for dose after 2h on Harshaw reader 5500. The dose at the contralateral breast nipple mea sured by TLD chips and it was between 4.5 and 17% of the totaI primary breast dose which is 5000cGy in 25 fractions. Further it was observed that the maximum contribution of contralateral breast dose was due to medial tangential half blocked field [in Kds2]. Dose was reduced to one third of the scatter dose to the contralateral breast using 2mm of lead shield and some modifications in the treatment technique. Thermoluminescence dosimetry is quite easy, accurate and convenient method to measure the contralateral breast dose. Reduction in unwanted scatter dose to the trilateral breast is in accord with the philosophy of keeping radiation exposure as low as reasonably achievable and might be of most benefit for young patients

Radiation exposure levels in family members of Omani patients with thyrotoxicosis treated with radioiodine [[131]I] as outpatients

This study was conducted to assess whether the radiation exposure levels of Omani family members of thyrotoxic patients, if treated with radioiodine therapy as outpatients, are within the international and local radiation dose limits in order to allow them to be treated as outpatients. The study included 86 family members of 22 self-dependent thyrotoxic patients [29 children

Study of Acute Myelocytic Leukemia Patient Treatment That Used Total Skin Electron Beam / 의학물리

Total Skin Electron Beam Therapy (TSEBT) of linear accelerator has become use so as to be useful, 2~9 MeV of energy territories came to be used with mycosis fungoides and cutaneous lymphomas in the superficial lesion treatment which covers the major portion of the body. I treat a patient to Stanford technique in this study, and it is 60 degrees around the patients whom Stanford technique irradiated electronic beam to a linear accelerator in horizontal directions and there is a way a standard of TSEBT treat it to six located field (anterior, posterior, and four obliques) becoming. An each field does horizontally it and consist to beam of the two component which fitted the center to a suitable angle. a patient treats it to three dual field a day in order to make short treatment time. when a first day, we treat one dual field at anterior position and two dual field at posterior position. when the second day, treat one dual field at posterior position and two dual field at anterior position. Therefore, six dual field is finished in perfect periodic two days. we made cylindrical acrylic phantom, and I inserted a dosimeter film between phantom. in order to measure a dose distribution calculation before treat a patient, and a patient checked it in six field directions that got from a treatment. It is after that thermoluminescent dosimetry (TLD) as it uses Rando phantom and then measurement dose distribution in six field directions after attaching at chest, the right and left flank, a back after irradiation.