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Background: The present study is aimed at calculating relative absorbed-dose energy response correction (R) of commonly used thermoluminescent dosimeters (TLDs) such as LiF, Li2B4O7, and Al2O3 as a function of depth in water for protons (50-250 MeV/n) and carbon ion (80-480 MeV/n) beams using Monte Carlo-based FLUKA code. Materials and Methods: On-axis depth-dose profiles in water are calculated for protons (50-250 MeV/n) and carbon ion (80-480 MeV/n) beams using FLUKA code. For the calculation of R, selective depths are chosen based on the depth-dose profiles. In the simulations, the TLDs of dimensions 1 mm × 1 mm × 1 mm are positioned at the flat, dose gradient, and Bragg peak regions of the depth-dose profile. Absorbed dose to detector was calculated within the TLD material. In the second step, TLD voxels were replaced by water voxel of similar dimension and absorbed dose to water was scored. Results: The study reveals that for both proton and carbon ion beams, the value of R differs from unity significantly at the Bragg peak position and is close to unity at the flat region for the investigated TLDs. The calculated R value is sensitive to depth in water, beam energy, type of ion beam, and type of TLD. Discussion: For accurate dosimetry of protons and carbon ion beams using TLDs, the response of the TLD should be corrected to account for its absorbed-dose energy dependence.
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The health risk of staying in space is a well-known fact, and the radiation doses to the astronauts must be monitored. The Pille-ISS thermoluminescent dosimeter system is present on the International Space Station (ISS) since 2003. We present an analysis of 60000 data points over 19 years from the 90 min automatic measurements and show a 4-day-long segment of 15 min measurements. In the case of the 15 min we show that the mapping of the radiation environment for the orbit of the ISS is possible with the Pille system. From our results the dose rates inside the South Atlantic Anomaly (SAA) are at least 1 magnitude higher than outside. From the 90 min data, we select orbits passing through the SAA. A statistical correlation in the SAA between the ISS altitude and monthly mean dose rate is presented with the Spearman correlation value of ρSAA=0.56. The dose rate and the sunspot number show strong inverse Pearson correlation (R2=-0.90) at a given altitude.
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Astronautas , Nave Espacial , Dosimetría Termoluminiscente , Nave Espacial/instrumentación , Dosimetría Termoluminiscente/instrumentación , Dosimetría Termoluminiscente/métodos , Humanos , Dosis de Radiación , Monitoreo de Radiación/instrumentación , Monitoreo de Radiación/métodos , Radiación Cósmica , Vuelo EspacialRESUMEN
Objective To compare Hp(3) calibration with a homemade (A) thermoluminescent dosimeter (TLD) and an imported (B) TLD in a standard X-ray RQR radiation field, to explore the different responses of A and B, and to provide foundation for the calibration of Hp(3). Methods A column mode was selected. Hp(3) calibration was performed using A and B in a standard X-ray RQR radiation field in the Secondary Standard Dosimetry Laboratory, National Institute for Radiological Protection, China Center for Disease Control and Prevention. Angle response, energy response, and linear response were calibrated with RQR4 (60 kV), RQR7 (90 kV), and RQR9 (120 kV), respectively. Results In terms of angle response, the calibration results of A were relatively high, while the calibration results of B were relatively low. In terms of energy response, the calibration results showed a similar pattern to angle response. In terms of linear response, the calibration results of both A and B were satisfactory. Conclusion Both A and B can be used for normal calibration of Hp(3) in a standard X-ray RQR radiation field. However, in actual monitoring, attention should be paid to the energy and angle response values of TLDs.
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Background: Positron emission tomography/computed tomography (PET/CT) is an imaging modality that combines images from high-energy gamma rays emitted by a positron emitting radiopharmaceutical and those from the CT component. The images are then used in the diagnosis of severe diseases. Procedures with PET radiopharmaceuticals introduce a risk of high occupational radiation exposure to staff handling them. 18Fluorine-Fluorodeoxyglucose ([18F]FDG) is the most commonly used PET radiopharmaceutical. Aim: To determine the radiation exposure of staff working at the PET/CT facility. Setting: Academic hospital in Gauteng. Methods: The study was quantitative and descriptive. The radiation exposure data of participants were collected using Polimaster®electronic pocket dosimeters, ring dosimeters and thermoluminescent dosimeters. The participants' workflow was tracked and the tasks that led to the highest radiation exposure were identified. Results: Radiopharmacists had 129 dispensing days with the resultant daily radiation exposure ranging between 0.01 µSv and 0.32 µSv. The radiographers' daily radiation exposure ranged between 7.08 µSv and 19.14 µSv. Radiographers received the highest radiation dose during radiopharmaceutical injection (average = 1.86 µSv). Conclusion: The study found that staff working at a new PET/CT facility in Gauteng were not at risk of radiation exposure above the accepted annual limits, which are 20 mSv per annum, averaged over 5 years, and with no more than 50 mSv in 1 year. Contribution: The findings revealed the need for continuous training in radiation protection measures for all staff working in the PET/CT facility.
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Surface brachytherapy (BT) lacks standard quality assurance (QA) protocols. Commercially available treatment planning systems (TPSs) are based on a dose calculation formalism that assumes the patient is made of water, resulting in potential deviations between planned and delivered doses. Here, a method for treatment plan verification for skin surface BT is reported. Chips of thermoluminescent dosimeters (TLDs) were used for dose point measurements. High-dose-rate treatments were simulated and delivered through a custom-flap applicator provided with four fixed catheters to guide the Iridium-192 (Ir-192) source by way of a remote afterloading system. A flat water-equivalent phantom was used to simulate patient skin. Elekta TPS Oncentra Brachy was used for planning. TLDs were calibrated to Ir-192 through an indirect method of linear interpolation between calibration factors (CFs) measured for 250 kV X-rays, Cesium-137, and Cobalt-60. Subsequently, plans were designed and delivered to test the reproducibility of the irradiation set-up and to make comparisons between planned and delivered dose. The obtained CF for Ir-192 was (4.96 ± 0.25) µC/Gy. Deviations between measured and TPS calculated doses for multi-catheter treatment configuration ranged from -8.4% to 13.3% with an average of 0.6%. TLDs could be included in clinical practice for QA in skin BT with a customized flap applicator.
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Braquiterapia , Humanos , Braquiterapia/métodos , Reproducibilidad de los Resultados , Radioisótopos de Iridio/uso terapéutico , Dosificación Radioterapéutica , Dosimetría Termoluminiscente , Agua , RadiometríaRESUMEN
Background: Radiation protection plays a key role in medicine, due to the considerable usage of radiation in diagnosis and treatment. The protection against radiation exposure with inappropriate equipment is concerning. Objective: The current study aimed to investigate the efficiency and quality of the radiation protection gowns with multi-layered nanoparticles compositions of Bismuth, Tungsten, Barium, and Copper, and light non-lead commercial gowns in angiography departments for approval of the manufacturers' declarations and improve the quality of gowns. Material and Methods: In this case study, physicians, physician assistants, radiology technologists, and nurses were asked to wear two commercial and proposed gowns in the angiography departments. Dosimetry of personnel was conducted using a Thermoluminescent Dosimeter (TLD) (GR-200), and the radiation dose received by personnel was compared in both cases. The participants were asked to fill out a questionnaire about the quality and comfort of two radiation protection gowns. Results: However, both gowns provide the necessary radiation protection; the multi-layer proposed gown has better radiation protection than the commercial sample (2 to 14 percent reduction in effective dose). The proposed gown has higher flexibility and efficiency than the commercial sample due to the use of nanoparticles and multi-layers (2.3 percent increase in personnel satisfaction according to the questionnaires). Conclusion: However, the multi-layer gown containing nanoparticles of Bismuth, Tungsten, Barium, and Copper has no significant difference from the non-lead commercial sample in terms of radiation protection, it has higher flexibility and comfort with more satisfaction for the personnel.
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In a brachytherapy room irradiated with an Iridium-192 (192Ir) source, the spatial distributions of photon dose rates were measured and calculated for the dose distribution both inside and outside the room. The spatial distributions were measured using a thermoluminescent dosimeter (LiF-100) on the surfaces of the concrete walls and barriers of the irradiation room. The calculations were performed using the particle and heavy ion transport code system (PHITS) by considering the detailed model of the brachytherapy room and the radiation source used in the measurements. The measured and calculated doses exhibited a similar distribution pattern within and outside the brachytherapy room. To reduce the edge effect at the entrance door, the addition of a 3-mm thick lead layer on the surface of the concrete wall on the left doorstop is recommended. For the 60Co source, with the existing walls and lead door thickness, the dose at the control console and in front of the entrance maze increased by a factor of approximately 60.
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Braquiterapia , Dosimetría Termoluminiscente , Dosificación Radioterapéutica , Fotones/uso terapéutico , Método de MontecarloRESUMEN
Abdominal colic pain or hematuria is suspected to be caused by urinary tract stones. Commonly used X-ray examinations include kidney-ureter-bladder plain radiography (KUB), intravenous urography (IVU), and abdominal computed tomography (CT). In this study, a high-sensitivity thermoluminescent dosimeter (TLD) was embedded in a Rando phantom to directly measure organ dose and evaluate effective dose. During each experiment, 139 TLD measurement points that cover almost all organs (as recommended by the ICRP 103 report) were examined. Red bone-marrow and remainder tissues have a high tissue weighting factor (0.12), and they are widely distributed. In the phantom, 34 TLDs and 31 TLDs were embedded in the red bone-marrow and remainder tissues to improve the accuracy and representativeness of organ doses. The detailed organ dose distributions for KUB, IVU, and abdominal CT are presented. The effective doses for KUB and IVU were 0.22 and 1.51 mSv, respectively, and those for two abdominal CTs were 8.21 and 9.27 mSv. This experiment presents a conversion factor of 0.0177 mSv·mGy-1 cm-1 for the abdominal CT examination, which differs from most of the conversion factors obtained through the Monte Carlo simulation method.
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Uréter , Riñón/diagnóstico por imagen , Fantasmas de Imagen , Dosis de Radiación , Radiografía , Tomografía Computarizada por Rayos X/métodos , Uréter/diagnóstico por imagen , Vejiga Urinaria/diagnóstico por imagen , Urografía/métodosRESUMEN
Nuclear medicine technicians would receive unavoidable exposures during the preparation and administration of radiopharmaceuticals. Based on the staff dose monitoring, the dose reduction efficiencies of the radiation protection shields and the need to implement additional strategies to reduce the staff doses could be evaluated. In this study, medical staff doses during the preparation and administration of Tc-99 m, I-131, and Kr-81 radiopharmaceuticals were evaluated. The dose reduction efficiencies of the lead apron and thyroid shield were also investigated. GR-207 thermoluminescent dosimeter (TLD) chips were used for quantifying the medical staff doses. The occupational dose magnitudes were determined in five organs at risk including eye lens, thyroid, fingers, chest, and gonads. TLDs were located under and over the protective shields for evaluating the dose reduction efficiencies of the lead apron and thyroid shield. The occupational doses were normalized to the activities used in the working shifts. During preparation and injection of Tc-99 m radiopharmaceutical, the average annual doses were higher in the chest (4.49 mGy) and eye lenses (4 mGy). For I-131 radiopharmaceutical, the average annual doses of the point-finger (15.8 mGy) and eye lenses (1.23 mGy) were significantly higher than other organs. During the preparation and administration of Kr-81, the average annual doses of the point-finger (0.65 mGy) and chest (0.44 mGy) were higher. The significant dose reductions were achieved using the lead apron and thyroid shield. The radiation protection shields and minimum contact with the radioactive sources, including patients, are recommended to reduce the staff doses.
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Background and objective Every dose of radiation has the potential to cause biological harm. Quantitative assessment of radiation doses to radiosensitive organs can aid dental professionals in taking the appropriate protective measures against radiation. This data may also be used among the general public to alleviate fears of radiation exposure in dental radiography. This study aimed to estimate the surface radiation dose at the level of the thyroid and lower abdomen during intraoral periapical radiography (IOPAR). Materials and methods A total of 80 calcium sulfate (CaSO4) discs were utilized in this cross-sectional in vitro study to estimate the surface radiation dose at the level of thyroid and lower abdomen on a phantom model while using an IOPAR. After exposure, the discs were submitted to the Radiation Laboratory's "Personnel Monitoring Service" to measure the surface radiation dose. Mean and standard deviations were calculated using descriptive statistics for continuous variables. The Mann-Whitney U test was used to compare bi-variate samples of independent groups. All statistical analyses were performed using SPSS Statistics version 21.0 (IBM, Armonk, NY). Results The results showed a statistically significant difference in radiation exposure between the maxillary anterior and mandibular anterior regions when the thermoluminescent dosimeter (TLD) was placed in the lower abdomen (p=0.000). When the maxillary and mandibular posterior regions were compared, there was a statistically significant difference in radiation exposure when the TLD was placed in the lower abdomen (p=0.000). Conclusion When the cone was positioned in the maxillary region, there was an increase in surface radiation dosage to the lower abdomen and thyroid.
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PURPOSE: This study aimed to evaluate the dosimetric properties of a newly developed thermoluminescent sheet-type dosimeter (TLD-sheet) for clinical proton beams. MATERIALS AND METHODS: The TLD-sheet is composed mainly of manganese doped lithium triborate, with a physical size and thickness of 150 mm × 150 mm and 0.15 mm respectively. It is flexible and can be cut freely for usage. The TLD-sheet has an effective atomic number of 7.3 and tissue-equivalent properties. We tested the reproducibility, fading effect, dose linearity, homogeneity, energy dependence, and water equivalent thickness (WET) of the TLD-sheet for clinical proton beams. We conducted tests with both unmodulated and modulated proton beams at energies of 150 and 210 MeV. RESULTS: The measurement reproducibility was within 4%, which included the inhomogeneity of the TLD-sheet. The fading rates were approximately 20% and 30% after 2 and 7 days respectively. The TLD-sheet showed notable energy dependence in the Bragg peak and distal end of the spread-out Bragg peak regions. However, the dose-response characteristics of the TLD-sheet remained linear up to a physical dose of 10 Gy in this study. This linearity was highly superior to those of commonly used radiochromic film. The thin WET of the TLD-sheet had little effect on the range. CONCLUSION: Although notable energy dependences were observed in Bragg peak region, the response characteristics examined in this study, such as reproducibility, fading effects, dose linearity, dose homogeneity and WET, showed that the TLD-sheet can be a useful and effective dosimetry tool. With its flexible and reusable characteristics, it may also be an excellent in vivo skin dosimetry tool for proton therapy.
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Protones , Dosímetros de Radiación , Humanos , Radiometría , Reproducibilidad de los Resultados , Dosimetría TermoluminiscenteRESUMEN
AIMS: In central nervous system (CNS) tumors, surgery combined with radiotherapy may cure many tumors. The basic technique in conventional radiotherapy is craniospinal radiotherapy; in this technique, spinal cord can be treated with electron or photon beams. This study was aimed to compare two radiotherapy techniques in craniospinal radiotherapy, (a) treatment of spine with a single photon beam and (b) with a combination of photon and electron beams. MATERIALS AND METHODS: The two techniques were planned. In the first technique, both brain and spine were irradiated with 6 MV photon beams. In the second technique, brain was irradiated with 6 MV photon and spine with 18 MeV electron beams. To compensate the dose deficiency in lumbar area, an anterior field of 15 MV photon beam was also applied in the second technique. The dose to target volume and organ at risks (OARs) were measured by thermoluminescent dosimeter and compared with the corresponding values calculated by Isogray treatment planning system. RESULTS: OARs including heart, mandible, thyroid, and lungs received lower dose from technique 2 compared with technique 1; kidneys were exceptions which received higher dose in the technique 2. CONCLUSIONS: The dose to thyroid, mandible, heart, and lungs were lower in technique 2, while kidneys received higher dose in technique 2. This was caused by using the anterior 15 MV photon beam. Based on these results, for children, instead of photon beam for treatment of spinal cord, it is wiser to use electron beam.
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Neoplasias Encefálicas/terapia , Electrones/uso terapéutico , Fotones/uso terapéutico , Planificación de la Radioterapia Asistida por Computador/métodos , Neoplasias de la Médula Espinal/terapia , Encéfalo/patología , Encéfalo/efectos de la radiación , Encéfalo/cirugía , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/patología , Niño , Corazón/efectos de la radiación , Humanos , Riñón/efectos de la radiación , Pulmón/efectos de la radiación , Mandíbula/efectos de la radiación , Procedimientos Neuroquirúrgicos , Órganos en Riesgo/efectos de la radiación , Radiometría/estadística & datos numéricos , Dosificación Radioterapéutica , Planificación de la Radioterapia Asistida por Computador/estadística & datos numéricos , Radioterapia Adyuvante/métodos , Médula Espinal/patología , Médula Espinal/efectos de la radiación , Médula Espinal/cirugía , Neoplasias de la Médula Espinal/diagnóstico por imagen , Neoplasias de la Médula Espinal/patología , Glándula Tiroides/efectos de la radiaciónRESUMEN
Our purpose was to evaluate whether the position of a thermoluminescent dosimeter (TLD) crystal results in different exposure readings. Methods: Nine subjects wore 2 TLD badges (one facing inward, toward the palm, and one facing outward) for 2 mo. Both TLDs were worn on the middle finger of the dominant hand, with the inward-facing TLD placed at the bottom and the outward-facing TLD at the top. At the end of the first month, these TLDs were replaced with new ones for another month. Combined results from the badges for the 2 mo were recorded in millisieverts. A paired t test with 2-sample means was performed to compare the 2 positions in general nuclear medicine and PET/CT subjects, with an α of 0.05. Results: For all subjects and for the general nuclear medicine and PET/CT groups, mean exposure was greater for the inward-facing TLD. Conclusion: For a TLD worn on the dominant hand, extremity-exposure readings are maximized when the TLD faces inward.
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Dosimetría Termoluminiscente/instrumentación , Humanos , Tomografía Computarizada por Tomografía de Emisión de PositronesRESUMEN
PURPOSE: The thermoluminescence dosimeter (TLD) has desirable features including low cost, reusability, small size, and relatively low energy dependence. However, the commonly available poly-crystal TLDs (e.g., TLD-100) exhibit high interdetector variability that requires individual calibration for high detection accuracy. To improve individual TLD tracking robustness, we developed an optical fingerprinting method to identify the TLD-100 chips. METHODS: Seven hundred and fifty-two images were initially captured using a digital microscope camera to build a feature library for both facets of 376 TLD-100 chips. A median intensity thresholding method was used to segment images into foreground and background. The affine transformation was used to register the segmented images to the same position. The fingerprint of each image was calculated from its registered image. All fingerprints were then recorded in an Elasticsearch® search database. The TLD fingerprint match was tested three times when the library was established and repeated once 20 months later. All chips were irradiated at 0, 1, 4, and 8 Gy on a calibrated clinical MV linac to establish the individual calibration curve. RESULTS: The true positive rate of identifying TLDs based on their optical fingerprints was 100% at initialization of the inventory. After 20 months and multiple deployments for characterization, calibration, and dose measurement, the true positive match rate dropped to 99% with zero false-positive matches. The TLDs exhibited high self-consistency in the dose-response test with R2 between 0.988 and 1 with linear regression. CONCLUSIONS: The TLD-100 chips surface textures are unique and sufficient to support accurate identification based on the optical fingerprinting. This method provides inexpensive and robust management of the TLDs for individual calibration and dosimetry.
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Fenómenos Ópticos , Dosimetría Termoluminiscente/instrumentación , CalibraciónRESUMEN
Objective To compare the calibration result of standard X-ray RQR radiation field between SSDL (NIRP) and CEA LIST LNHB (France),and to explore the feasibility of calibrating Hp (3) in standard X-ray RQR radiation field of SSDL (NIRP).Methods Using a column model with a diameter and high of 20 cm,TLD was calibrated in SSDL (NIRP) and CEA LIST LNHB (France) to measure the personal dose equivalent eye lens dose Hp (3),X-ray RQR radiation field included RQR4 (60 kV),RQR7 (90 kV),RQR9 (120 kV),with energy response,angle response and linear response.Results In terms of energy response,the calibration results of TLD in both SSDL (NIRP) and CEA LIST LNHB (France) were in good agreement.The difference between exposure value and response value was less than 10％.In terms of angle response,the calibration result of TLD in CEA LIST LNHB (France) was better in SSDL (NIRP).The difference between exposure value and response value in CEA LIST LNHB (France) was less than 6％,while the difference between exposure value and response value in SSDI (NIRP) was more than 10％ at angle of 20°.In terms of linear response,both calibration result of SSDL (NIRP) and CEA LIST LNHB (France) were in good agreement.Conclusions The standard X-ray RQR field in SSDL (NIRP) can be used for the calibration of Hp (3).
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Objective@#To compare the calibration result of standard X-ray RQR radiation field between SSDL (NIRP) and CEA LIST LNHB(France), and to explore the feasibility of calibrating Hp(3) in standard X-ray RQR radiation field of SSDL(NIRP).@*Methods@#Using a column model with a diameter and high of 20 cm, TLD was calibrated in SSDL (NIRP) and CEA LIST LNHB (France) to measure the personal dose equivalent eye lens dose Hp(3), X-ray RQR radiation field included RQR4(60 kV), RQR7(90 kV), RQR9(120 kV), with energy response, angle response and linear response.@*Results@#In terms of energy response, the calibration results of TLD in both SSDL (NIRP) and CEA LIST LNHB (France) were in good agreement. The difference between exposure value and response value was less than 10%. In terms of angle response, the calibration result of TLD in CEA LIST LNHB (France) was better in SSDL(NIRP). The difference between exposure value and response value in CEA LIST LNHB (France) was less than 6%, while the difference between exposure value and response value in SSDL(NIRP) was more than 10% at angle of 20°. In terms of linear response, both calibration result of SSDL (NIRP) and CEA LIST LNHB (France) were in good agreement.@*Conclusions@#The standard X-ray RQR field in SSDL (NIRP) can be used for the calibration of Hp(3).
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AIM: Liver volume measurement is a mandatory test before measure liver surgeries and transplantation. We aimed a study on the difference in volume measurement and radiation dose to an anthropomorphic liver phantom using high-dose and low-dose diagnostic computed tomography (CT). MATERIALS AND METHODS: Several measurements of the manual total volume measurement done on an anthropomorphic liver phantom mounted with thermoluminescent dosimeter. We exposed the phantom with diagnostic CT, low-dose CT, and a low-dose CT with copper filter. RESULTS: Phantom underwent ten scanning for each exposure. There was no significant difference in the total volume measurement in comparison to the phantom volume. The volume of phantom measured by low-dose CT, low-dose CT with copper phantom, and high-dose CT were 1869 ± 18 cm3, 1852 ± 24 cm3, and 1908 ± 12 cm3, (P = 0.3), respectively. However, the radiation dose delivered was significantly different (1.54 mGy, 0.77 mGy, and 5.84 mGy [P = 0.001], respectively). CONCLUSION: Total liver volume measurement provides essential clinical information in several clinical conditions. We recommended that the volume measured by a low-dose CT has an excellent correlation with the diagnostic quality CT and should be a routine in the routine clinical practice. CT volumetry achieves the same result while using very less radiation exposure. It may also be used with functional imaging to give complete information.
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AIM: In the present study, surface doses within the target area and contralateral breast (CLB) received during conventional treatment of carcinoma breast are evaluate and compared for treatment on two different beam energies, i.e., Co-60 γ-ray and 6 MV X-ray beams with thermoluminescent dosimeter, LiF:Mg, Ti (TLD-100). MATERIALS AND METHODS: The study includes a group of 23 patients comprising 11 patients treated with Co-60 γ-ray beam and 12 patients by 6 MV X-ray beam. RESULTS AND DISCUSSION: The treatment using Co-60 γ-ray and 6 MV X-ray beams contributes an average percentage dose of 8.15% ± 0.56% and 4.73% ± 0.94%, respectively, to CLB in mastectomy patients. The contribution of tangential fields (mastectomy) to the CLB doses ranges between 12.71 and 16.40 cGy (5.45%-7.03%) for treatment with Co-60 γ-ray beam and 6.33-10.95 cGy (1.86-4.69%) for treatment with 6 MV X-ray beam. The supraclavicular field (SCF) contributes 1.45%-1.93% and 1.02%-1.43% for treatment with Co-60 γ-ray and 6 MV X-ray beams, respectively. The average surface dose (normalized with breast dose) 89.1% ± 8.5% for Co-60 beam in the SCF region differs significantly from the 60.2% ± 13.0% value for 6 MV X-ray beam. CONCLUSION: The CLB doses for mastectomy patients are higher for Co-60 beam as compared to 6 MV X-ray beam, and better dose homogeneity is achieved within the irradiated breast from 6 MV X-ray beam. The CLB doses are slightly higher for patients treated with breast conservative radiotherapy or lumpectomy. The average surface dose to SCF decreases by ~30% of treated breast dose for treatment with 6 MV X-ray beam.
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Neoplasias de la Mama/radioterapia , Radioisótopos de Cobalto/uso terapéutico , Mama/efectos de la radiación , Mama/cirugía , Neoplasias de la Mama/cirugía , Femenino , Humanos , Mastectomía/métodos , Mastectomía Segmentaria/métodos , Fantasmas de Imagen , Dosificación Radioterapéutica , Planificación de la Radioterapia Asistida por Computador/métodosRESUMEN
Thyroid exposure to radiation in brain computed tomography (CT) scan is of great value since it is considered as a vital organ. This study aimed to investigate the absorbed dose of thyroid by various protocols of head CT in patients referring to 64-slice CT scan center and to compare the values with the calculated dose by imaging performance and assessment of CT (ImPACT) method. Also, the values of CT scan dose index (CTDI) were calculated with semiconductor detector. In this cross-sectional study, 120 outpatients including three groups of forty individuals over 40 years old referring to the hospital radiology centers in Tehran for head CT were chosen and 3 thermo-luminescence dosimeter (TLD-GR200) were applied on thyroid gland of each patient. For brain CT, Absorbed and effective doses of thyroid gland were calculated by ImPACT software. In addition, semiconductor detector in head CTDI phantom calculated CTDI for the applied protocols. Mean effective dose of thyroid gland in brain scan group was calculated by TLD and ImPACT software which showed no significant difference (P < 0.001). Mean effective dose of thyroid gland in unidirectional and bi-directional sinus scan by TLD and ImPACT software were different significantly (P < 0.001). Also, the differences between CTDI values shown by brain and sinus scan protocol with semiconductor detector and those CTDI were significant (P < 0.001). The calculated values of absorbed dose and effective doses of thyroid by TLD and ImPACT software were not significantly different. Mean effective dose calculated for thyroid gland in head scans by TLD and ImPACT was less than the annual permissive level for thyroid gland suggested by International Committee on Radiological Protection. In this study, calculated values of thyroid effective dose in brain scan with 64-slice scanner were less than the calculated values in a similar study.
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A total body irradiation (TBI) protocol was developed to support a bone marrow transplant (BMT) program for the treatment of canine hematologic malignancies. The purpose of this prospective study is to describe implementation of the protocol and resultant dosimetry. Nongraphic manual treatment planning using 6 MV photons, isocentric delivery, 40 × 40 cm field size, wall-mounted lasers to verify positioning, a lucite beam spoiler (without use of bolus material), a dose rate of 8.75 cGy/min at patient isocenter, and a source-to-axis distance of 338 cm were used for TBI. A monitor unit calculation formula was derived using ion chamber measurements and a solid water phantom. Five thermoluminescent dosimeters (TLDs) were used at various anatomic locations in each of four cadaver dogs, to verify fidelity of the monitor unit formula prior to clinical implementation. In vivo dosimetric data were then collected with five TLDs at various anatomic locations in six patients treated with TBI. A total dose of 10 Gy divided into two 5 Gy fractions was delivered approximately 16 h apart, immediately followed by autologous stem cell transplant. The mean difference between prescribed and delivered doses ranged from 99% to 109% for various sites in cadavers, and from 83% to 121% in clinical patients. The mean total body dose in cadavers and clinical patients when whole body dose was estimated by averaging doses measured by variably placed TLDs ranged from 98% to 108% and 93% to 102% of the prescribed dose, respectively, which was considered acceptable. This protocol could be used for institutional implementation of TBI.