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.

Keywords: Rectum, Brachytherapy, HDR, Thermoluminescent dosimetry, Uterine cervix cancer

OBJECTIVE: To calculate spectra of cobalt-60 beam at water depth and correction factors for absorbed dose measurements obtained with lithium fluoride thermoluminescent dosimeters using Monte Carlo simulation. MATERIALS AND METHODS: The simulations of secondary spectra of clinical cobalt-60 sources were performed with the PENELOPE Monte Carlo code at different water depths. Experimental measurements of deep doses were obtained with thermoluminescent dosimeters and ionization chamber under reference conditions for radiotherapy. Correction factors for the thermoluminescent dosimeters detectors were obtained through the ratio between the relative energy absorption for the low energy spectrum and the total spectrum. RESULTS: Deep spectral analysis has demonstrated the presence of secondary low-energy spectra responsible for a significant portion of the dose deposition. Discrepancies of 3.2% were observed among the doses measured with ionization chamber and thermoluminescent dosimeters. The adoption of correction factors has allowed a reduction in the discrepancy among absorbed doses to a maximum of 0.3%. CONCLUSION: Simulated spectra allow the calculation of correction factors for reading of thermoluminescent dosimeters utilized in the measurement of deep doses, contributing for the reduction of uncertainties associated with quality control of clinical beams in radiotherapy.

Keywords: Monte Carlo simulation, Radiotherapy, Spectrometry, Quality control, Thermoluminescent dosimetry, TLD

OBJECTIVE: Evaluation of equipment conditions and dosimetry in computed tomography services utilizing protocols for head, abdomen, and lumbar spine in adult patients (in three different units) and pediatric patients up to 18 months of age (in one of the units evaluated). MATERIALS AND METHODS: Computed tomography dose index and multiple-scan average dose were estimated in studies of adult patients with three different units. Additionally, entrance surface doses as well as absorbed dose were estimated in head studies for both adult and pediatric patients in a single computed tomography unit. RESULTS: Mechanical quality control tests were performed, demonstrating that computed tomography units comply with the equipment-use specifications established by the current standards. Dosimetry results have demonstrated that the multiple-scan average dose values were in excess of up to 109.0% the reference levels, presenting considerable variation amongst the computed tomography units evaluated in the present study. Absorbed doses obtained with pediatric protocols are lower than those with adult patients, presenting a reduction of up to 51.0% in the thyroid gland. CONCLUSION: The present study has analyzed the operational conditions of three computed tomography units, establishing which parameters should be set for the deployment of a quality control program in the institutions where this study was developed.

Keywords: Computed tomography equipment, Quality control, Dosimetry, Dose reduction

OBJECTIVE: The present study evaluates the dose distribution received by physicians involved in hemodynamic procedures of coronary angiography and coronariography. The influence of some factors such as pulsed or continuous fluoroscopy mode and vein and/or artery access site was investigated. MATERIALS AND METHODS: Measurements have been performed with LiF:Mg,Ti thermoluminescent dosimeters placed on seven different sites of the practitioners' bodies: hands, left knee, neck, forehead and chest, under and over the lead apron. Radiation doses for each procedure were evaluated in physicians who had performed 60 coronariography and 30 angioplasty procedures. The thermoluminescent dosimeters were calibrated in the operational quantity personal dose equivalent, Hp(d), at depths of 0.07, 3 and 10 mm. RESULTS: The results of the present study demonstrate the significant role played by thyroid protectors and lead aprons for reducing radiation doses received by practitioners. Occupational doses in continuous mode fluoroscopy through brachial access were higher than with pulsed mode fluoroscopy through femoral access. CONCLUSION: The present study has demonstrated the necessity of implementing additional protective measures as well as a mechanism of training in radiation protection for physicians involved in interventional cardiological procedures.

Keywords: Interventional radiology, Fluoroscopy, Hemodynamic procedures, Radiation protection, Thermoluminescent dosimetry

OBJECTIVE: Entrance skin dose, effective dose, and imaging quality in chest radiographs of adult patients have been evaluated. MATERIALS AND METHODS: The study has been developed in eight institutions - seven public hospitals (two of them philanthropic institutions) and one private - in the cities of Agra dos Reis, Cabo Frio, Campos dos Goytacazes, Itaperuna, Niterói, Recife and Rio de Janeiro. Entrance skin dose and effective dose have been evaluated in 735 chest radiographs obtained in posteroanterior/anteroposterior and lateral projections. As regards imaging criteria, 44 radiographs have been evaluated. RESULTS: Variations of up to nine times in entrance skin dose, and six times in effective dose have been detected for a same type of projection. Also, significant discrepancies have been found in values resulting from radiographic techniques employed. Besides, imaging quality has not been good since the rate of compliance with imaging criteria was only 55%. CONCLUSION: There is a pressing need for improvement/standardization of procedures in conventional radiology; this can be achieved by implementing a quality control and assurance program in the department of radiology, including training of technicians, x-ray equipment calibration, and sensitometric control of films processors.

Keywords: Chest x-ray, Quality control, Dosimetry

Energy and angular dependences of different thermoluminescent materials were studied with the objective to verify which type of detector would be the most appropriate for beta monitoring of workers. Three types of CaSO4:Dy + teflon pellets were studied. The energy dependence was evaluated using standard beta radiation sources (147Pm, 204Tl and 90Sr+90Y). For the angular dependence study, the pellets were exposed to beta radiation of the 90Sr+90Y source, varying the incidence angle between 0° and 90°. In relation to the studied characteristics, the CaSO4:Dy + 10% C dosimeters were the most adequate for use in beta monitoring of workers.

Keywords: Thermoluminescent dosimetry, Beta radiation, Angular dependence, Energetic dependence

OBJECTIVE: To present the solidly established traceability structure for ionometric standards and for thermoluminescent dosimetry system that ensures reliability of the Dosimetry Quality Assurance Program and is aimed to certify the highest level of accuracy of the measurements. MATERIALS AND METHODS: Thermoluminescent powder dosimeters (DTL 937) placed into plastic capsules and packed in specific kits for each intended application were mailed to the participant centers. RESULTS: The results of the intercomparisons performed between "Laboratório de Ciências Radiológicas da Universidade do Estado do Rio de Janeiro" and EQUAL-ESTRO for the beam of 60Co gamma rays, expressed for (1sigma), and the results of the dose absorbed measurements obtained with the chambers of the Program EQUAL and the chambers of the Dosimetry Quality Assurance Program were lower than 0.5%. CONCLUSION: Based on these results we concluded that the Dosimetry Quality Assurance Program reached the desired level of reliability to allow its implementation.

Keywords: Quality assurance, Radiotherapy, Dosimetric intercomparison, Thermoluminescent dosimetry, TLD

OBJECTIVE: To evaluate the precision of the absorbed radiation doses in bone marrow transplant therapy during whole body irradiation. MATERIALS AND METHODS: Two-hundred CaSO4:Dy + teflon tablets were calibrated in air and in "phantom". These tablets were randomly selected and divided in groups of five in the patients' body. The dosimetric readings were obtained using a Harshaw 4000A reader. Nine patients had their entire bodies irradiated in parallel and opposite laterals in a cobalt-60 Alcion II model, with a dose rate of 0.80 Gy/min at 80.5 cm, {(10 × 10) cm² field}. The dosimetry of this unit was performed using a Victoreen 500 dosimeter. For the determination of the mean dose at each point evaluated, the individual values of the tablets calibrated in air or "phantom" were used, resulting in a build up of 2 mm to superficialize the dose at a distance of 300 cm. RESULTS: In 70% of the patients a variation of less than 5% in the dose was obtained. In 30% of the patients this variation was less than 10%, when values obtained were compared to the values calculated at each point. A mean absorption of 14% was seen in the head, and an increase of 2% of the administered dose was seen in the lungs. In patients with latero-lateral distance greater than 35 cm the variation between the calculated doses and the measured doses reached 30% of the desired dose, without the use of compensation filters. CONCLUSION: The measured values of the absorbed doses at the various anatomic points compared to the desired doses (theoretic) presented a tolerance of ± 10%, considering the existent anatomical differences and when using the individual calibration factors of the tablets.

Keywords: Whole body irradiation, Dosimetry, Thermoluminescent dosimeters, Doses, Bone marrow transplantation

An occupational monitoring program in diagnostic radiology was implemented at the "Hospital Universitário Clementino Fraga Filho - UFRJ", Rio de Janeiro, Brazil, in accordance with the Brazilian legislation. Previously, a survey of all personnel involved with ionizing radiation was performed. Many problems were observed: the great majority of the workers were not properly monitored; only three departments of the hospital kept an independent survey of the occupational doses; there was not a follow-up control of the high doses. With the implementation of the program, a new laboratory was chosen to read the dosemeters and this initiative resulted in reduction of the hospital costs. The inclusion of seven more departments in the program represented an increase of 60% in the number of monitored workers. The program also provided a system to control the high doses, especially in the Hemodynamics department, which presented the highest mean dose value (0.32 mSv/month). An area survey program was performed during different periods in places considered of high risk for the workers and for the public as well. At the same time, a software was used to build a database with the aim of controlling all personnel data. The implementation of the program provided all personnel involved a better knowledge of the risks associated with ionizing radiation and of radioprotection, and also awareness of the need of correct use of the personal dose monitors.

Keywords: Radiological protection, Occupational exposure, Quality control, Radiation dosimetry, Radiology

High dose rate brachytherapy has been increasingly recognized in most countries, and radiotherapy services using this equipment are encouraged to have a very efficient quality assurance program to ensure protection for patients, workers and other personnel involved. The objective of this paper was to determine the types of tests for high dose rate equipment required by official protocols (TG40, TG56 and ARCAL XXX) and to compare them with the types of tests utilized by some radiotherapy services. We concluded that: a) the protocol TG56 is more extensive and complete than the other official protocols (TG40 and ARCAL XXX); b) the protocols used by the services evaluated on this study were based on the protocol TG56, and were concordant with the other official protocols. In these protocols annual tests were frequently replaced by tests performed quarterly or twice a year. This study established the types of test used and their frequency of utilization, and permitted the design of an optimized protocol that may help in the implementation of basic and indispensable tests in order to ensure patient adequate treatment and safety to personnel involved, and consequently improve high dose rate brachytherapy quality assurance

Keywords: Dosimetry. Brachytherapy. High dose rate brachytherapy (HDR). Quality control

Technetium-99m labeled radiopharmaceuticals are currently the main diagnostic agents used in nuclear medicine. Radiopharmaceuticals are prepared locally through a reaction between a complexant agent (pharmaceutical) and technetium-99m. These reactions may generate impurities resulting into the production of radiopharmaceuticals with substandard quality or with different characteristics from those considered ideal. In this article we discuss some of the factors that may interfere with the preparation of radiopharmaceuticals and the quality control tests that can be used to ensure the quality of the agents.

Keywords: Radiopharmaceuticals. Generators. Technetium-99m. Quality controls.

OBJECTIVE: Aiming at contributing to the knowledge on doses in computed tomography (CT), this study has the objective of determining dosimetric quantities associated with pediatric abdominal CT scans, comparing the data with diagnostic reference levels (DRL). MATERIALS AND METHODS: The study was developed with a Toshiba Asteion single-slice CT scanner and a GE BrightSpeed multi-slice CT unit in two hospitals. Measurements were performed with a pencil-type ionization chamber and a 16 cm-diameter polymethylmethacrylate trunk phantom. RESULTS: No significant difference was observed in the values for weighted air kerma index (C_W), but the differences were relevant in values for volumetric air kerma index (C_VOL), air kerma-length product (P_KL,CT) and effective dose. CONCLUSION: Only the C_W values were lower than the DRL, suggesting that dose optimization might not be necessary. However, P_KL,CT and effective dose values stressed that there still is room for reducing pediatric radiation doses. The present study emphasizes the importance of determining all dosimetric quantities associated with CT scans.

Keywords: Pediatric computed tomography scans; Dosimetric quantities; Weighted dose index; Volumetric air kerma index; Air kermalength product.

OBJECTIVE: This article presents a way to obtain estimates of dose in patients submitted to radiotherapy with basis on the analysis of regions of interest on nuclear medicine images. MATERIALS AND METHODS: A software called DoRadIo (Dosimetria das Radiações Ionizantes [Ionizing Radiation Dosimetry]) was developed to receive information about source organs and target organs, generating graphical and numerical results. The nuclear medicine images utilized in the present study were obtained from catalogs provided by medical physicists. The simulations were performed with computational exposure models consisting of voxel phantoms coupled with the Monte Carlo EGSnrc code. The software was developed with the Microsoft Visual Studio 2010 Service Pack and the project template Windows Presentation Foundation for C# programming language. RESULTS: With the mentioned tools, the authors obtained the file for optimization of Monte Carlo simulations using the EGSnrc; organization and compaction of dosimetry results with all radioactive sources; selection of regions of interest; evaluation of grayscale intensity in regions of interest; the file of weighted sources; and, finally, all the charts and numerical results. CONCLUSION: The user interface may be adapted for use in clinical nuclear medicine as a computer-aided tool to estimate the administered activity.

Keywords: Nuclear medicine; Biokinetic distribution; Dosimetric evaluations; Administered activity.

OBJECTIVE: To evaluate the level of ambient radiation in a PET/CT center. MATERIALS AND METHODS: Previously selected and calibrated TLD-100H thermoluminescent dosimeters were utilized to measure room radiation levels. During 32 days, the detectors were placed in several strategically selected points inside the PET/CT center and in adjacent buildings. After the exposure period the dosimeters were collected and processed to determine the radiation level. RESULTS: In none of the points selected for measurements the values exceeded the radiation dose threshold for controlled area (5 mSv/year) or free area (0.5 mSv/year) as recommended by the Brazilian regulations. CONCLUSION: In the present study the authors demonstrated that the whole shielding system is appropriate and, consequently, the workers are exposed to doses below the threshold established by Brazilian standards, provided the radiation protection standards are followed.

Keywords: Dosimetry; Thermoluminescence dosimetry; PET/CT.

OBJECTIVE: To estimate the entrance surface air kerma (K_a,e) and air kerma in the region of radiosensitive organs in radiographs of pediatric paranasal sinuses. MATERIALS AND METHODS: Patient data and irradiation parameters were collected in examinations of the paranasal sinuses in children from 0 to 15 years of age at two children's hospitals in the city of Recife, PE, Brazil. We estimated the K_a,e using the X-ray tube outputs and selected parameters. To estimate the air kerma values in the regions of the eyes and thyroid, we used thermoluminescent dosimeters. RESULTS: The K_a,e values ranged from 0.065 to 1.446 mGy in cavum radiographs, from 0.104 to 7.298 mGy in Caldwell views, and from 0.113 to 7.824 mGy in Waters views. Air kerma values in the region of the eyes ranged from 0.001 to 0.968 mGy in cavum radiographs and from 0.011 to 0.422 mGy in Caldwell and Waters views . In the thyroid region, air kerma values ranged from 0.005 to 0.932 mGy in cavum radiographs and from 0.002 to 0.972 mGy in Caldwell and Waters views. CONCLUSION: The radiation levels used at the institutions under study were higher than those recommended in international protocols. We recommend that interventions be initiated in order to reduce patient exposure to radiation and therefore the risks associated with radiological examination of the paranasal sinuses.

Keywords: Radiometry; Radiography; Paranasal sinuses; Pediatrics; Thermoluminescent dosimetry..