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Introduction: Image guided radiotherapy allows for particularly conformal tumour irradiation through precise patient positioning. Becoming the standard for radiotherapy, this increases imaging doses to the patient. The Halcyon 3.0 linear accelerator (Varian Medical Systems, Palo Alto, CA) requires daily imaging due to its geometry. For this reason, the accelerator is equipped with on-line kV and MV imaging. However, daily CBCT images required for irradiation apply additional radiation, which increases the dose to normal tissue and therefore can affect the patient's secondary cancer risk. In this study, actual organ doses were measured for the kV system, and a comparison of normal tissue doses for all available kV CBCT protocols was presented to demonstrate differences in imaging doses across entities and protocols. In addition, effective dose and secondary cancer risk from imaging are evaluated. Material and methods: Measurements were performed with thermoluminescent dosimeters in an anthropomorphic phantom positioned according to each entity (brain, head and neck, breast, lung, pelvis). CBCT images were obtained, using all available pre-set protocols without further adjustment of the parameters. Measured doses for each position and each protocol were then compared and secondary cancer risk of relevant and specifically radiosensitive organs was calculated. Results: It was found that imaging doses for protocols such as Pelvis and Head could be reduced by up to half using the corresponding Fast and Low Dose modes, respectively. On the other hand, larger field sizes or the Large mode yielded higher doses than their initial protocols. Image Gently was found to spare normal tissue best, however it is not suitable for certain entities due to low image quality or insufficient projection data. Discussion: By using appropriate kV-CBCT protocols, it is possible to reduce imaging doses to a significant extent and therefore spare healthy tissue. Combined with studies of image quality, the results of this study could lead to adjustments in workflow regarding the choice of protocols used in daily routine. This could prevent unnecessary radiation exposure and reduce secondary cancer risk.

Image guided radiotherapy allows for particularly conformal tumour irradiation through precise patient positioning. Becoming the standard for radiotherapy, this increases imaging doses to the patient. The Halcyon 3.0 linear accelerator (Varian Medical Systems, Palo Alto, CA) requires daily imaging due to its geometry. For this reason, the accelerator is equipped with on-line kV and MV imaging. However, daily CBCT images required for irradiation apply additional radiation, which increases the dose to normal tissue and therefore can affect the patient's secondary cancer risk. In this study, actual organ doses were measured for the kV system, and a comparison of normal tissue doses for all available kV CBCT protocols was presented to demonstrate differences in imaging doses across entities and protocols. In addition, effective dose and secondary cancer risk from imaging are evaluated. Measurements were performed with thermoluminescent dosimeters in an anthropomorphic phantom positioned according to each entity (brain, head and neck, breast, lung, pelvis). CBCT images were obtained, using all available pre-set protocols without further adjustment of the parameters. Measured doses for each position and each protocol were then compared and secondary cancer risk of relevant and specifically radiosensitive organs was calculated. It was found that imaging doses for protocols such as Pelvis and Head could be reduced by up to half using the corresponding Fast and Low Dose modes, respectively. On the other hand, larger field sizes or the Large mode yielded higher doses than their initial protocols. Image Gently was found to spare normal tissue best, however it is not suitable for certain entities due to low image quality or insufficient projection data. By using appropriate kV-CBCT protocols, it is possible to reduce imaging doses to a significant extent and therefore spare healthy tissue. Combined with studies of image quality, the results of this study could lead to adjustments in workflow regarding the choice of protocols used in daily routine. This could prevent unnecessary radiation exposure and reduce secondary cancer risk. [ABSTRACT FROM AUTHOR]

Detecting extremely low light signals is the basis of many scientific experiments and measurement techniques. For many years, a high-voltage photomultiplier has been the only practical device used in the visible and infrared spectral range. However, such a solution is subject to several inconveniences, including high production costs, the requirements of a supply voltage of several hundred volts, and a high susceptibility to mechanical damage. This paper presents two detection systems based on avalanche photodiodes, one cooled and the second operating at room temperature, in terms of their potential application in thermoluminescent dosimeter units. The results show that the detection system with an uncooled photodiode may successfully replace the photomultiplier tube commonly used in practice. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to assess patient dose and investigate the parameters affecting patient's dose during fluoroscopy guided procedures at a hospital for possible dose reduction. Methods: Standard quality control tests were performed prior to the data collection. Twelve (12) thermoluminescent dosimeters TLDs were arranged on a Perspex phantom for skin dose measurement. Skin dose (SD) and Kerma Area Product (KAP) were recorded for varying radiation field size at fix phantom thickness and vice versa. Doses were assessed on one-hundred and one (101) patients undergoing barium swallow (BaS), retrograde (Rtr) and hysterosalpingoraphy (HSG). Results and discussion: The mean fluoroscopy time (FT) for Rtr, BaS and HSG procedures were 1 ± 0.67 min, 2.12 ± 1.30 min and 0.66 ± 0.5 min respectively. The mean KAP values were 8.21 ± 6.05 Gy.cm2, 87.33 ± 31.2 Gy.cm2 and 6.01 ± 3.25 Gy.cm2 for Rtr, BaS and HSG. The mean skin dose (SD) values for the cited procedures were 11.64 ± 1.25 mGy, 121.80 ± 40.87 mGy and 7.55 ± 2.58 mGy. It was found that patient skin dose increase rapidly with the phantom thickness (factor ≈ 2) as compared with the field size (factor ≈ 1). The SD variation with field size for the same thickness was negligible but the KAP values increase considerably with field size. The mean KAP value obtained was found to be higher with average factors of 2 and 2.5 for Rtr and HSG respectively. The regression analysis shows that there is a poor correlation (R2 =0.33) between ESD and KAP but a significant statistical significance (P-value = 0.003). It also shows that the SD in this study can be predictable with known fluoroscopy time for HSG and retrograde procedures at 77% and 52% accuracy respectively. Conclusion: The main contributor of patient's dose (i.e. SD) was patient thickness which cannot be regulated by the staff. Other factors that can be regulated by the staff to reduce patient's dose were the fluoroscopy time for HSG and Rtr procedures and the use of smaller field size as possible without compromising the clinical outcome. [ABSTRACT FROM AUTHOR]

The eye lens is recently classified as one of the most radiosensitive tissues by the International Commission on Radiological Protection (ICRP), and it has been suggested that the eye lens receives radiation dose during mammography due to scatter radiation. The aim of this study was to investigate the radiation dose received by the lens of the clients' eye from Full Field Digital Mammography (FFDM) and Digital Breast Tomosynthesis (DBT) screening. The eye radiation dose received by ATOM dosimetry phantom was estimated with thermo-luminescent dosemeters (TLDs). One TLD was utilised for each eye. A breast phantom was exposed for four-view screening mammography using 16 FFDM machines and one DBT machine. The breast phantom was exposed three times for each mammographic position and an average TLD dose reading was considered to minimise random error. For four-view FFDM screening, the phantom eye radiation dose ranges from 0.013 mGy to 0.029 mGy with a mean±sd of 0.019 ± 0.005 mGy. A higher eye radiation dose of 0.041 mGy was recorded from four-view DBT screening. The statistical analysis demonstrated that the eye lens radiation dose is strongly and significantly correlated to breast organ dose and X-ray tube voltage. The phantom eye lens was exposed to scatter radiation from FFDM and DBT screening. The measured dose via the four-view DBT screening was higher than the four-view FFDM screening, but sits below the internationally acceptable ranges. If the findings of our paper hold true in practice, then the risk to the lens of the eyes for women attending breast screening is acceptable. The new lens radiation dose levels recommended by the ICRP necessitate the reevaluation of eye radiation dose from different radiographic examinations, especially those used for screening purpose where healthy individuals involved. [ABSTRACT FROM AUTHOR]

The paper explores the application of Steiner's most-frequent-value (MFV) statistical method in sensor data analysis. The MFV is introduced as a powerful tool to identify the most-common value in a dataset, even when data points are scattered, unlike traditional mode calculations. Furthermore, the paper underscores the MFV method's versatility in estimating environmental gamma background blue (the natural level of gamma radiation present in the environment, typically originating from natural sources such as rocks, soil, and cosmic rays), making it useful in scenarios where traditional statistical methods are challenging. It presents the MFV approach as a reliable technique for characterizing ambient radiation levels around large-scale experiments, such as the DEAP-3600 dark matter detector. Using the MFV alongside passive sensors such as thermoluminescent detectors and employing a bootstrapping approach, this study showcases its effectiveness in evaluating background radiation and its aptness for estimating confidence intervals. In summary, this paper underscores the importance of the MFV and bootstrapping as valuable statistical tools in various scientific fields that involve the analysis of sensor data. These tools help in estimating the most-common values and make data analysis easier, especially in complex situations, where we need to be reasonably confident about our estimated ranges. Our calculations based on MFV statistics and bootstrapping indicate that the ambient radiation level in Cube Hall at SNOLAB is 35.19 μ Gy for 1342 h of exposure, with an uncertainty range of + 3.41 to − 3.59 μ Gy, corresponding to a 68.27% confidence level. In the vicinity of the DEAP-3600 water shielding, the ambient radiation level is approximately 34.80 μ Gy, with an uncertainty range of + 3.58 to − 3.48 μ Gy, also at a 68.27% confidence level. These findings offer crucial guidance for experimental design at SNOLAB, especially in the context of dark matter research. [ABSTRACT FROM AUTHOR]

In the present age, marked by data-driven advancements in various fields, the importance of machine learning (ML) holds a prominent position. The ability of ML algorithms to resolve complex patterns and extract insights from large datasets has solidified its transformative potential in various scientific domains. This paper introduces an innovative application of ML techniques in the domain of radiation dosimetry. Specifically, it shows the applicability of ML in estimating the radiation dose received by occupational workers. This estimation is expressed in terms of personal dose equivalent, and it involves the utilization of thermoluminescence signals emitted by CaSO _4 :Dy-based personnel monitoring badges. To estimate personal dose equivalent, three-stage algorithm driven by ML models is proposed. This algorithm systematically identifies the photon energy ranges, calculates the average photon energy, and determines personal dose equivalent. By implementing this approach to the conventional three-element dosimeter, the study overcomes existing limitations and enhances accuracy in dose estimation. The algorithm demonstrates 97.8% classification accuracy in discerning photon energy ranges and achieves a coefficient of determination of 0.988 for estimating average photon energy. Importantly, it also reduces the coefficient of variation of relative deviations by up to 6% for estimated personal dose equivalent, compared to existing algorithms. The study improves accuracy and establishes a new methodology for evaluating radiation exposure to occupational workers using conventional thermoluminescent dosimeter badge.

Purpose: Radiotherapy (RT), which is considered one of the critical treatments for cancer patients is also known as adjuvant therapy and palliative care, and can be attempted alone or concurrent with chemotherapy. Although RT reduces the risk of recurrence, the scattered dose may enhance the risk of secondary cancer induction; this is raising some challenges in clinical practice. To the best of our knowledge, few studies to date have assessed such effects of brain cancer adjuvant radiotherapy. Materials and Methods: We estimated the RT-induced risk of secondary cancer for a 45-year-old patient who had undergone radiotherapy of the head and pelvis with a 6 MV photon beam in 15 and 10 sessions, respectively. The absorbed dose by the thyroid, breast, eye lenses, region overlying ovaries, and parotids was measured using Thermoluminescent Dosimeters (TLD). Since the patient was scanned before radiotherapy, it was decided to calculate their risk as well. To evaluate the cancer risk, radiobiological models for Excess Absolute Risk (EAR), as well as Excess Relative Risk (ERR) published by the Committee on the Biological Effects of Ionizing Radiation (BEIR) in report VII, were implemented. This study thus aimed to estimate the Risk of Exposure-Induced Death (REID) and assess the radiation dose delivered to patients from Computed Tomography (CT) scans and common diagnostic nuclear medicine examinations. Results: The mean risk of secondary cancer for sensitive organs was calculated 3 years after radiotherapy. The highest estimated ERR was related to the region overlying right and left ovaries for pelvic radiotherapy (47.82) and (51.17), and the next highest EAR followed by right and left eye lenses for brain radiotherapy (18.09) and (15.43), respectively. In addition, other cancers arising from CT scans had the highest REID values for solid cancer (0.0015) and bone scans revealed the highest REID values for other cancers (0.00121). Conclusion: Calculating the corresponding risks of RT is of great significance for the patients in procedural change. Choosing proper field sizes and adapted techniques to avoid excessive doses to healthy organs can thus be a great assistance in this regard.

The paper describes a system and experimental procedure that use integrating passive detectors, such as thermoluminescent dosimeters (TLDs), for the measurement of ultra-low-level ambient dose equivalent rate values at the underground SNOLAB facility located in Sudbury, Ontario, Canada. Because these detectors are passive and can be exposed for relatively long periods of time, they can provide better sensitivity for measuring ultra-low activity levels. The final characterization of ultra-low-level ambient dose around water shielding for ongoing direct dark matter search experiments in Cube Hall at SNOLAB underground laboratory is given. The conclusion is that TLDs provide reliable results in the measurement of the ultra-low-level environmental radiation background. [ABSTRACT FROM AUTHOR]

OBJECTIVE In total body irradiations (TBI), it becomes hard getting homogenous dose distribution due to inhomogeneous body shape and tissue density variations. The main goal of the radiotherapy is saving critic organs while achieving a homogeneous dose distribution at target volume. Tomotherapy is a new and one of the most effective technologies used for TBIs. In this study, it was aimed to investigate TBI planned target volume coverage and organ doses using helical tomotherapy. METHODS To simulate rando phantom geometrically, arms and legs created by rice are added to rando phantom and were immobilized by a vacuum bed. The computer tomography images of the lower and upper region of the phantom with a slice thickness of 3 mm were acquired. Thermoluminescent dosimeters (TLDs) were placed entrance-exit, midpoint doses of lens, lungs, and kidneys onto a rando phantom. The treatment plans were prepared and irradiated with helical tomotherapy technique. Results of the measurements and treatment planning system (TPS) doses were compared. All procedures were repeated 3 times and averaged. TPS and TLD doses were evaluated by Wilcoxon test. RESULTS In the plans prepared with the TPS, a homogeneous dose distribution was obtained with a homogeneity index of 0.16 for the upper body and 0.04 for the lower body. When the calculated critical organ doses were compared with the measured organ doses, there was no statistically significant difference between them. CONCLUSION It was seen that saving critical organs and achieving desired dose distribution are possible without blocks in tomotherapy. Doses calculated from TPS and measured by TLD matched. [ABSTRACT FROM AUTHOR]

A ‘Cyclotron’ is a proton particle accelerator, broadly used for short-lived isotopes (like F-18) production for imaging in radiation oncology. In Pakistan, Fluorine (F-18) is being produced by the cyclotrons installed in various hospitals. F-18 emits two gamma photons through the annihilation phenomenon, having 511 keV energy each. F-18 has converted into (18F) Fluorodeoxyglucose (FDG) through the synthesis process. This high-intensity gamma photon may be dangerous to radiation workers if radiation safety regulations are not followed. A study was conducted for the measurement of ambient radiation levels in the controlled areas and supervised areas of cyclotron facilities using Thermoluminescent Dosimeters (TLDs). The results obtained from TLDs were formulated and evaluated. All measured values were meeting the criteria of classification of areas i.e., the radiation doses will receive greater than 6mSv/year in a Controlled area and the radiation dose will receive greater than 1mSv/year in a Supervised area as mentioned in Pakistan Nuclear Regulatory Authority (PNRA’s) Regulations on Radiation Protection (PAK/904). It is concluded that all workers received radiation doses within limits and the facilities had implemented clause 26 of PNRA Regulations through effective shielding in the design of the cyclotron facilities, and dose monitoring. The effective implementation of PNRA regulations is verified through regulatory oversight and through such type of cross-verification in the country. [ABSTRACT FROM AUTHOR]

This retrospective study provides an insight into the levels of radiation exposure of six nuclear medicine (NM) staff (four technologists and two nurses) performing routine diagnostic 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET/CT) at the University Clinical Centre of the Republic of Srpska, Department of Nuclear Medicine and Thyroid Disorders, Banja Luka, Bosnia and Herzegovina. Data analysis included monthly staff exposure measured with personal thermoluminescent dosimeters (TLD) between June and December 2018, quantified in terms of normalised dose for the whole body [Hp(10)] and dominant hand [Hp(0.07)] and their comparison between each staff member and between the two groups (technologists and nurses). The study goal was to establish how our Department compared with reports from other PET/CT centres worldwide in terms of annual number of procedures and exposure limits and whether there could be room for further improvements in radiation protection. The number of procedures rose considerably from 208 in 2016 to 876 in 2019 and was 423 in the observed seven-month period. Mean individual whole-body exposure dose per GBq of injected 18F-FDG activity, [Hp(10)/A] was 18.55 μSv/GBq for the four technologists and 15.61 μSv/GBq for the two nurses. Mean dominant-hand exposure dose per GBq of injected 18F-FDG activity [Hp(0.07)/A] was 16.99 μSv/GBq and 25.44 μSv/GBq for the two groups, respectively. The average annual cumulative dose for all staff was (1.06±0.29) mSv for Hp(10) and (1.15±0.32) mSv for Hp(0.07). These results are comparable with those of similar studies. Staff doses were well below the annual limits. Nurses received slightly higher extremity doses than technologists. In view of the increasing trends in the number of PET/CT procedures, dose monitoring should be continued to identify exposure hotspots and maintain doses as low as possible.

Purpose: Computational dosimetry software is routinely used to evaluate the organ and effective doses from computed tomography (CT) examinations. Studies have shown a significant variation in dose estimates between software in adult cohorts, and few studies have evaluated software for pediatric dose estimates. This study aims to compare the primary organ and effective doses estimated by four commercially available CT dosimetry software to thermoluminescent dosimeter (TLD) measurements in a 1‐year‐old phantom. Methods: One hundred fifteen calibrated LiF (Mg, Cu, P)‐TLD 100‐H chips were embedded within an anthropomorphic phantom representing a 1‐year‐old child at positions that matched the approximate location of organs within an infant. The phantom was scanned under three protocols, each with whole‐body coverage. The mean absorbed doses from 25 radiosensitive organs and skeletal tissues were determined from the TLD readings. Effective doses for each of the protocols were subsequently calculated using ICRP 103 formalism. Dose estimates by the four Monte Carlo–based dose calculation systems were determined and compared to the directly measured doses. Results: Most organ doses determined by computation dosimetry software aligned to phantom measurements within 20%. Additionally, comparisons between effective doses are calculated using computational and direct measurement methods aligned within 20% across the three protocols. Significant variances were found in bone surface dose estimations among dosimetry methods, likely caused by differences in bone tissue modeling. Conclusion: All four‐dosimetry software evaluated in this study provide adequate primary organ and effective dose estimations. Users should be aware, however, of the possible estimated uncertainty associated with each of the programs. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to evaluate the thyroid glands' radiation dose and the risk of thyroid cancer induction from head or neck computed tomography (CT) examinations. Methods: In a prospective study, we evaluated all participants of all ages and sex referred for Head or Neck CT Scan at the University College Hospital, Ibadan and Me Cure Healthcare Limited, Ibadan, Oyo State, Nigeria. Thyroid radiation dose was estimated with impact scan calculator, and real-time dose measurement with thermoluminescent badge dosimeters (TLDs). Data were analysed and P < 0.05 was considered statistically significant. Results: One hundred and sixty-three participants (128 adults and 35 children) participated in the study. In most participants (74%), the tube voltage was 120 kVp. The estimated median thyroid gland dose by the imPACT scan calculator was 4.95 mGy (range = 1.20–30.0 mGy) and 4.40 mGy (range = 3.0–5.10 mGy), while the real-time dose measured by the TLD was 4.79 mGy (range = 1.73–96.7 mGy) and 2.33 mGy (range = 1.20–3.73 mGy) at Centre A and B, respectively. The estimated median thyroid cancer risk was 2.88 × 10−6 (maximum range of 52 × 10−6) at centre A and a median value of 3.20 × 10−6 with a cancer risk estimate that may reach 17.9 × 10−6 recorded at centre B, compared to a cumulative thyroid cancer risk of 0.12 × 10−5 among the general Nigerian population. Conclusions: Scanner specifications and technique may significantly contribute to variations seen in thyroid radiation doses. There may be a need to optimise centre protocols and apply dose reference levels for head and neck CT examinations to reduce thyroid cancer risk in Nigeria.

Objective: The objective of this study was to evaluate the thyroid glands' radiation dose and the risk of thyroid cancer induction from head or neck computed tomography (CT) examinations. Methods: In a prospective study, we evaluated all participants of all ages and sex referred for Head or Neck CT Scan at the University College Hospital, Ibadan and Me Cure Healthcare Limited, Ibadan, Oyo State, Nigeria. Thyroid radiation dose was estimated with impact scan calculator, and real-time dose measurement with thermoluminescent badge dosimeters (TLDs). Data were analysed and P < 0.05 was considered statistically significant. Results: One hundred and sixty-three participants (128 adults and 35 children) participated in the study. In most participants (74%), the tube voltage was 120 kVp. The estimated median thyroid gland dose by the imPACT scan calculator was 4.95 mGy (range = 1.20-30.0 mGy) and 4.40 mGy (range = 3.0-5.10 mGy), while the real-time dose measured by the TLD was 4.79 mGy (range = 1.73-96.7 mGy) and 2.33 mGy (range = 1.20-3.73 mGy) at Centre A and B, respectively. The estimated median thyroid cancer risk was 2.88 × 10-6 (maximum range of 52 × 10-6) at centre A and a median value of 3.20 × 10-6 with a cancer risk estimate that may reach 17.9 × 10-6 recorded at centre B, compared to a cumulative thyroid cancer risk of 0.12 × 10-5 among the general Nigerian population. Conclusions: Scanner specifications and technique may significantly contribute to variations seen in thyroid radiation doses. There may be a need to optimise centre protocols and apply dose reference levels for head and neck CT examinations to reduce thyroid cancer risk in Nigeria. [ABSTRACT FROM AUTHOR]

This study aims to verify the dose delivery of prostate radiotherapy treatments in an adult pelvic phantom with two metallic hip and femur prosthesis using a four‐field box technique. The prostate planned target volume (PTV) tridimensional (3D) dose distribution was evaluated using gel dosimetry, and thermoluminescent dosimeters (TLD) were used for point‐dose measurements outside it. Both results were compared to the treatment planning system (TPS) dose calculation without using heterogeneity corrections to evaluate the influence of the metal in the dose distribution. MAGIC‐f gel dosimeter (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper with Formaldehyde) associated with magnetic resonance imaging was used. TLD were positioned at several points at the bone metal interface and the sacrum region. The comparison of the gel measured and the TPS calculated dose distributions were done using gamma analysis (3%/3 mm), and a pass rate of 93% was achieved. The TLD dose values at the bone‐metal interface showed variations from the planned dose. However, at the sacrum region, where the beams did not intercept the prosthesis, there was a good agreement between TPS planning and TLD measurements. Our results show how the combination of 3D dosimetry and measurements at specific points in the phantom allowed a comprehensive view of the dose distribution and identified that care must also be paid to regions outside the PTV. [ABSTRACT FROM AUTHOR]

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Background: Studies have shown that protective aprons are carelessly handled after working hours. This, in turn, leads to crack, tear, hole, and creases on the apron, which may lead to distortion in the attenuating property and hence reduction in efficiency. Aim and Objective: The aim of the study was to carry out the radiographic assessment of four protective aprons (denoted A–D), to check for tear, crack, or pressure marks and to simulate what the equivalent dose rate, dose/procedure, percentage absorbance, and transmission factor (TF) would be if a physician is to perform hysterosalpingogram (HSG), for which he/she will be averagely exposed twice/procedure. Materials and Methods: This study used a functional mobile X-ray unit, four protective aprons, a measuring tape, an electronic dosimeter and a locally designed phantom as materials. The first phase involved the radiographic exposure of the protective aprons. The second phase involved the use of a plastic phantom to produce scatter, a wooden T-stand to hold the apron, which was positioned 1.6 m diagonally from the X-ray collimator. This position was assumed to be where a physician would stand during the procedure. Results: Two out of the four aprons were defective (50%). One out of the four aprons was rejected because it exceeded the 670 mm[2] criteria for acceptance. The mean estimated dose/procedure was 65.69–347.56 μSv, and the estimated mean dose per year for 0.25, 0.35, and 0.50 mm protective aprons was 35,592, 9689, and 7900 μSv/year, respectively. TF for 0.25, 0.35, and 0.50 mm protective aprons was 20.4–23.2, 5.3–6.9, and 3.7%–6.3%, respectively. Absorbance for 0.35 and 0.50 mm protective aprons was ≥94%. There was no statistically significant difference in mean percentage absorbance for 0.25 mm protective aprons, compared to other studies (P = 0.981). Conclusion: Estimated equivalent skin dose per year to a physician with 0.25, 0.35, and 0.50 mm protective aprons was below 500 mSv/year, and the mean percentage absorbance for 0.25 mm protective aprons was seen to be below 90%.

In this work, lithium triborate (LiB3 O5) nanophosphor was synthesised by precipitation assisted high‐temperature solid‐state method followed by heating at different sintering temperatures. Then, its crystal structure and morphology were fully characterised. LiB3 O5 was doped with different concentrations of different dopants. To determine the thermoluminescence (TL) properties and structural specifications of doped lithium triborate, the sample was irradiated by photons and then, its TL glow curve was obtained using a TL dosimeter‐reader system. To study the effect of heating rate (HR) on TL characterisation of this nanophosphor, TL measurements were done at different HRs. The results showed that, sintering temperature can affect the morphology and structural properties of lithium triborate and consequently its TL intensity. The findings also showed that the LiB3 O5 :Al nanophosphor with the dopant concentration of 2 wt.% has the highest sensitivity and the best peak position among the studied activators. The results of the HR method showed that this method may be provided accurate calculations of the physical parameters of the TL process. These results may be helpful in the development of tissue equivalent TL nanocrystalline detectors usable in medical and personnel dosimetry. [ABSTRACT FROM AUTHOR]

Purpose: To verify dose delivery and quality assurance of volumetric-modulated arc therapy (VMAT) for head and neck (H&N) cancer. Method: The Imaging and Radiation Oncology Core Houston (IROC-H) H&N phantom with thermoluminescent dosimeters (TLDs) and films, were imaged with computed tomography scan and the reconstructed image was transferred to pinnacle treatment planning system (TPS). On TPS, the planning target volume (PTV), secondary target volume (STV) and organ at risk (OAR) were delineated manually and a treatment plan was made. The dose constraints were determined for the concerned organs according to IROC-H prescription. The treatment plan was optimised using adoptive convolution algorithm to improve dose homogeneity and conformity. The dose calculation was performed using C.C Convolution algorithm and a Varian True Beam linear accelerator was used to deliver the treatment plan to the H&N phantom. The delivered radiation dose to the phantom was measured through TLDs and GafChromic external beam radiotherapy 2 (EBT2) films. The dosimetric performance of the VMAT delivery was studied by analysing percent dose difference, isodose line profile and gamma analysis of the TPS-computed dose and linac-delivered doses. Result: The percent dose difference of 3.8% was observed between the planned and measured doses of TLDs and a 1.5-mm distance to agreement (DTA) was observed by comparing isodose line profiles. Passed the gamma criteria of 3%/3 mm was with good percentages. Conclusion: The dosimetric performance of VMAT delivery for a challenging H&N radiotherapy can be verified using TLDs and films embedded in an anthropomorphic H&N phantom. [ABSTRACT FROM AUTHOR]

The effective dose (HE) and organ or tissue equivalent dose (HT) for use in brain computed tomography (CT) examinations with various body weights were evaluated. Thermoluminescent dosimeters (TLD-100H) were inserted into Rando and five anthropomorphic phantoms. These phantoms were made of polymethylmethacrylate (PMMA), according to the specifications of ICRU 48, with masses from 10 to 90 kg. Brain CT examinations were conducted, scanning the maxillae from the external auditory meatus to the parietal bone using a 128-slice multi-detector CT (MDCT) scanner. To reduce errors, three independent trials were conducted. Calculated HE,TLD, based on the weighting factor recommended by ICRP 103, was 1.72 ± 0.28 mSv, which slightly exceeds the HE,DLP of 1.70 mSv, that was calculated from the dose–length product (DLP) of the Rando phantom. This experiment yielded HE,TLD values of ICRP 103 from the highest 1.85 ± 0.28 (90 kg) to the lowest 1.47 ± 0.22 (10 kg) mSv. HE,TLD (mSv) = 5.45×10−3 W(kg) + 1.361, with an R 2 of 0.87667. Using the DLP protocol, HE,DLP was estimated from CTDIvol that was recorded directly from the console display of the CT unit and multiplied by the conversion coefficient (k) recommended by the ICRP 103. Finally, the experimental results obtained herein are compared with those in the literature. Physicians should choose and adjust protocols to prevent the exposure of patients to unnecessary radiation, satisfying the as low as reasonably achievable (ALARA) principle. These findings will be valuable to patients, physicians, radiologists and the public. [ABSTRACT FROM AUTHOR]

The treatment of head and neck (H&N) cancer presents formidable challenges due to the involvement of normal tissue and organs at risk (OARs) in the close vicinity. Ensuring the precise administration of the prescribed dose demands prior dose verification. Considering contour irregularity and heterogeneity in the H&N region, an anthropomorphic and heterogeneous H&N phantom was developed and fabricated locally for conducting the dosimetry audit in advanced radiotherapy treatments. This specialized phantom emulates human anatomy and incorporates a removable cylindrical insert housing a C-shaped planning target volume (PTV) alongside key OARs including the spinal cord, oral cavity, and bilateral parotid glands. Acrylonitrile Butadiene Styrene (ABS) was chosen for PTV and parotid fabrication, while Delrin was adopted for spinal cord fabrication. A pivotal feature of this phantom is the incorporation of thermoluminescent dosimeters (TLDs) within the PTV and OARs, enabling the measurement of delivered dose. To execute the dosimetry audit, the phantom, accompanied by dosimeters and comprehensive guidelines, was disseminated to multiple radiotherapy centers. Subsequently, hospital physicists acquired computed tomography (CT) scans to generate treatment plans for phantom irradiation. The treatment planning system (TPS) computed the anticipated dose distribution within the phantom, and post-irradiation TLD readings yielded actual dose measurements. The TPS calculated and TLD measured dose values at most of the locations inside the PTV were found comparable within ± 4%. The outcomes affirm the suitability of the developed anthropomorphic H&N phantom for precise dosimetry audits of advanced radiotherapy treatments., (© 2024 IOP Publishing Ltd.)

Purpose: To report in-vivo dosimetry in the infraclavicular region, a potential site of a cardiac implantable electronic device (CIED) and to evaluate the absorbed dose from intraoperative radiotherapy with electrons (ELIOT).Methods: 27 non-cardiopathic breast cancer (BC) patients without CIED received quadrantectomy and ELIOT as partial breast irradiation. Before delivering ELIOT, two catheters, each containing eight thermoluminescent dosimeters (TLDs), were positioned in the infraclavicular region. TLDs internal catheter was located deep in the tumor bed while the external catheter was placed on patient’s skin.Results: Data were available for 24/27 patients. The absorbed doses were referred to the dose of 21 Gy. Values measured by the external catheter were low, although statistically significant higher doses were found close to the applicator (mean values 0.26-0.49 Gy). External TLD doses in proximity of the applicator were lower than those detected by their internal counterparts. Values measured by the internal catheter TLDs varied according to the distance from the applicator while no correlation with tumor site and beam energy was found. The distance from the applicator to deliver < 2 Gy to a CIED was 2 cm, while from 2.5 cm the dose measured in all the patients became negligible.Conclusions: This dosimetric study provided data to support the clinical use of ELIOT in BC patients having CIEDs as long as the suggested minimum safe distance of 2.5 cm is taken from the RT field in case of ELIOT single dose of 21 Gy, in the energy range of 6-10 MeV. [ABSTRACT FROM AUTHOR]

Background: Determination of the exposure levels in the computerized tomography (CT) practices is necessary to define the respected national reference levels, quality control of CT centers and the risk assessment for radiation induced cancers. Material and Methods: On the basis of this necessity, the radiation exposure distribution due to common CT practices has been investigated at Razi Hospital CT center in Rasht using tissue-equivalent phantoms and the thermoluminescent dosimeters (TLD). The Head and Thorax phantoms were used with the standard dimensions incorporating holes at the center and edges for TLD placement. Dosimetry was carried out using LiF Mg, Cu, P small chips due to their relatively tissue equivalence, high sensitivity convenient annealing procedure and the non-complex glow curve. Results: Results showed that CTDI for Head is 52.85 mGy and for Body is 68.15mGy. CTDLW for Head is 13.67 mGy and for Body is 16.94mGy . Conclusion: In comparison with other radiographical procedures, patient absorbed doses in CT imaging are usually very high. Content of dose is increased by increase of mAs.

Aim and Objectives: To estimate the annual cumulative radiation dose received by a dentist in a ′less than an ideally sized clinic′ in Chennai. The objective of the study is to estimate the annual cumulative radiation dose received by the dentist at various distances and various angulations from the x-ray tube. Study Design: The head of a mannequin model was mounted on the dental chair to simulate a patient′s head and three thermoluminescent dosimeter (TLD) chips were kept at various distances and various angulations, at a constant height. The standard conventional intraoral dental radiographic unit was used, which was kept stationary, with a constant voltage of 70 Kv, 8 mA current, and a constant exposure time of 0.3 seconds. Ninety-two TLD chips were exposed 20 times a day with constant horizontal angulations for a period of one year. The reading from the TLD chips was obtained on a computer through a TLD Badge Reader. Statistical Analysis: Post Hoc tests and One-way analysis of variance (ANOVA) were used. Results and Conclusion: A decreasing trend was obtained in the average radiation doses, as the distance increased from the x-ray source, and a highly significant difference in doses (P < 0.001%) was found between 4 and 5.5 feet (ft). We found a minimum average radiation dose at an angle of 60° to 80° and behind the tube. The purpose of this study was to create awareness among dental professionals, who had ′less than an ideally sized clinic′. We recommend that the dentist follow guidelines suggested by the National Council on Radiation Protection and Measurements (NCRP), USA. From this study, it is clear that most clinics are of sizes that do not permit this distance (6 ft), and hence, it is recommended that they use suitable barriers.

Purpose To investigate the dosimetric characteristics of the new GMS BT-125-1 125I radioactive seed, including dose rate constant, radial dose functions, and anisotropy functions. Methods Dosimetric parameters of GMS BT-125-1 125I seed including dose rate constant, radial dose functions, and anisotropy functions were calculated using the Monte Carlo code of MCNP5, and measured with thermoluminescent dosimeters ( TLDs). The results were compared with those of PharmaSeed BT-125-1, PharmaSeed BT-125-2 125I, and model 6711 125I seeds. Results The dose rate constant of GMS BT-125-1 125I seed was 0.959 [ABSTRACT FROM AUTHOR]

Purpose: To analyze the most recent results of the Imaging and Radiation Oncology Core Houston Quality Assurance Center's (IROC-H) anthropomorphic head and neck (H&N) phantom to determine the nature of failing irradiations and the feasibility of altering credentialing criteria. Methods: IROC-H's H&N phantom, used for intensity-modulated radiation therapy credentialing for National Cancer Institute-sponsored clinical trials, requires that an institution's treatment plan agrees within ±7% of measured thermoluminescent dosimeter (TLD) doses; it also requires that ≥85% of pixels pass ±4 mm distance to agreement (7%/4 mm gamma analysis for film). The authors re-evaluated 156 phantom irradiations (November 1, 2014-October 31, 2015) according to the following tighter criteria: (1) 5% TLD and 5%/4 mm, (2) 5% TLD and 5%/3 mm, (3) 4% TLD and 4%/4 mm, and (4) 3% TLD and 3%/3 mm. Failure rates were evaluated with respect to individual film and TLD performance by location in the phantom. Overall poor phantom results were characterized qualitatively as systematic errors (correct shape and position but wrong magnitude of dose), setup errors/positional shifts, global but nonsystematic errors, and errors affecting only a local region. Results: The pass rate for these phantoms using current criteria was 90%. Substituting criteria 1-4 reduced the overall pass rate to 77%, 70%, 63%, and 37%, respectively. Statistical analyses indicated that the probability of noise-induced TLD failure, even at the 5% criterion, was <0.5%. Phantom failures were generally identified by TLD (≥66% failed TLD, whereas ≥55% failed film), with most failures occurring in the primary planning target volume (≥77% of cases). Results failing current criteria or criteria 1 were primarily diagnosed as systematic >58% of the time (11/16 and 21/36 cases, respectively), with a greater extent due to underdosing. Setup/positioning errors were seen in 11%-13% of all failing cases (2/16 and 4/36 cases, respectively). Local errors (8/36 cases) could only be demonstrated at criteria 1. Only three cases of global errors were identified in these analyses. For current criteria and criteria 1, irradiations that failed from film only were overwhelmingly associated with phantom shifts/setup errors (≥80% of cases). Conclusions: This study highlighted that the majority of phantom failures are the result of systematic dosimetric discrepancies between the treatment planning system and the delivered dose. Further work is necessary to diagnose and resolve such dosimetric inaccuracy. In addition, the authors found that 5% TLD and 5%/4 mm gamma criteria may be both practically and theoretically achievable as an alternative to current criteria. [ABSTRACT FROM AUTHOR]

Purpose: Radiation dose to patients undergoing examinations with Multislice Computed Tomography (MSCT) as well as Cone Beam Computed Tomography (CBCT) is a matter of concern. Risk management could benefit from efficient replace rational dose calculation tools. The paper aims to verify MSCT dose calculations using a Treatment Planning System (TPS) for radiotherapy and to evaluate four different variations of bow-tie filter characterizations for the beam model used in the dose calculations. Methods: A TPS (RayStation™, RaySearch Laboratories, Stockholm, Sweden) was configured to calculate dose from a MSCT (GE Healthcare, Wauwatosa, WI, USA). The x-ray beam was characterized in a stationary position the by measurements of the Half-Value Layer (HVL) in aluminum and kerma along the principal axes of the isocenter plane perpendicular to the beam. A Monte Carlo source model for the dose calculation was applied with four different variations on the beam-shaping bow-tie filter, taking into account the different degrees of HVL information but reconstructing the measured kerma distribution after the bow-tie filter by adjusting the photon sampling function. The resulting dose calculations were verified by comparison with measurements in solid water as well as in an anthropomorphic phantom. Results: The calculated depth dose in solid water as well as the relative dose profiles was in agreement with the corresponding measured values. Doses calculated in the anthropomorphic phantom in the range 26-55 mGy agreed with the corresponding thermo luminescence dosimeter (TLD) measurements. Deviations between measurements and calculations were of the order of the measurement uncertainties. There was no significant difference between the different variations on the bow-tie filter modeling. Conclusions: Under the assumption that the calculated kerma after the bow-tie filter replicates the measured kerma, the central specification of the HVL of the x-ray beam together with the kerma distribution can be used to characterize the beam. Thus, within the limits of the study, a flat bow-tie filter with an HVL specified by the vendor suffices to calculate the dose distribution. The TPS could be successfully configured to replicate the beam movement and intensity modulation of a spiral scan with dose modulation, on the basis of the specifications available in the metadata of the digital images and the log file of the CT. [ABSTRACT FROM AUTHOR]

Purpose: A dose calculation tool, which combines the accuracy of the dose planning method (DPM) Monte Carlo code and the versatility of a practical analytical multisource model, which was previously reported has been improved and validated for the Varian 6 and 10 MV linear accelerators (linacs). The calculation tool can be used to calculate doses in advanced clinical application studies. One shortcoming of current clinical trials that report dose from patient plans is the lack of a standardized dose calculation methodology. Because commercial treatment planning systems (TPSs) have their own dose calculation algorithms and the clinical trial participant who uses these systems is responsible for commissioning the beam model, variation exists in the reported calculated dose distributions. Today's modern linac is manufactured to tight specifications so that variability within a linac model is quite low. The expectation is that a single dose calculation tool for a specific linac model can be used to accurately recalculate dose from patient plans that have been submitted to the clinical trial community from any institution. The calculation tool would provide for a more meaningful outcome analysis. Methods: The analytical source model was described by a primary point source, a secondary extra-focal source, and a contaminant electron source. Off-axis energy softening and fluence effects were also included. The additions of hyperbolic functions have been incorporated into the model to correct for the changes in output and in electron contamination with field size. A multileaf collimator (MLC) model is included to facilitate phantom and patient dose calculations. An offset to the MLC leaf positions was used to correct for the rudimentary assumed primary point source. Results: Dose calculations of the depth dose and profiles for field sizes 4?4 to 40?40 cm agree with measurement within 2% of the maximum dose or 2 mm distance to agreement (DTA) for 95% of the data points tested. The model was capable of predicting the depth of the maximum dose within 1 mm. Anthropomorphic phantom benchmark testing of modulated and patterned MLCs treatment plans showed agreement to measurement within 3% in target regions using thermoluminescent dosimeters (TLD). Using radiochromic film normalized to TLD, a gamma criteria of 3% of maximum dose and 2 mm DTA was applied with a pass rate of least 85% in the high dose, high gradient, and low dose regions. Finally, recalculations of patient plans using DPM showed good agreement relative to a commercial TPS when comparing dose volume histograms and 2D dose distributions. Conclusions: A unique analytical source model coupled to the dose planning method Monte Carlo dose calculation code has been modified and validated using basic beam data and anthropomorphic phantom measurement. While this tool can be applied in general use for a particular linac model, specifically it was developed to provide a singular methodology to independently assess treatment plan dose distributions from those clinical institutions participating in National Cancer Institute trials. [ABSTRACT FROM AUTHOR]

Purpose: To provide data for estimation of fetal radiation dose (DF) from prophylactic hypogastric artery balloon occlusion (HABO) procedures. Methods: The Monte-Carlo-N-particle (MCNP)transport code and mathematical phantoms representing a pregnant patient at the ninth month of gestation were employed.PA,RAO20° andLAO20° fluoroscopy projections of left and right internal iliac arteries were simulated. Projection-specific normalized fetal dose (NFD) data were produced for various beam qualities. The effects of projection angle, x-ray field location relative to the fetus, field size, maternal body size, and fetal size onNFDwere investigated. Presented NFD values were compared to corresponding values derived using a physical anthropomorphic phantom simulating pregnancy at the third trimester and thermoluminescence dosimeters. Results: NFDdid not considerably vary when projection anglewas altered by±5°, whereas itwas found to markedly depend on tube voltage, filtration, x-ray field location and size, and maternal body size. Differences in NFD < 7.5% were observed for naturally expected variations in fetal size. A difference of less than 13.5% was observed between NFD values estimated by MCNP and direct measurements. Conclusions: Data and methods provided allow for reliable estimation of radiation burden to the fetus from HABO. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate various approaches for assessing patient organ doses resulting from radiotherapy cone-beam CT (CBCT), by the use of thermoluminescent dosimeter (TLD) measurements in anthropomorphic phantoms, a Monte Carlo based dose calculation software, and different dose indicators as presently defined. Methods: Dose evaluations were performed on a CBCT Elekta XVI (Elekta, Crawley, UK) for different protocols and anatomical regions. The first part of the study focuses on using PCXMC software (PCXMC 2.0, STUK, Helsinki, Finland) for calculating organ doses, adapting the input parameters to simulate the exposure geometry, and beam dose distribution in an appropriate way. The calculated doses were compared to readouts of TLDs placed in an anthropomorphic Rando phantom. After this validation, the software was used for analyzing organ dose variability associated with patients'differences in size and gender. At the same time, various dose indicators were evaluated: kerma area product (KAP), cumulative air-kerma at the isocenter (Kair), cone-beam dose index, and central cumulative dose. The latter was evaluated in a single phantom and in a stack of three adjacent computed tomography dose index phantoms. Based on the different dose indicators, a set of coefficients was calculated to estimate organ doses for a range of patient morphologies, using their equivalent diameters. Results: Maximum organ doses were about 1 mGy for head and neck and 25 mGy for chest and pelvis protocols. The differences between PCXMC and TLDs doses were generally below 10% for organs within the field of view and approximately 15% for organs at the boundaries of the radiation beam. When considering patient size and gender variability, differences in organ doses up to 40% were observed especially in the pelvic region; for the organs in the thorax, the maximum differences ranged between 20% and 30%. Phantom dose indexes provided better correlation with organ doses than Kair and KAP, with average ratios ranging between 0.9 and 1.1 and variations for different organs and protocols below 20%. The triple phantom setup allowed us to take into account scatter dose contributions, but nonetheless, the correlation with the evaluated organ doses was not improved with this method. Conclusions: The simulation of rotational geometry and of asymmetric beam distribution by means of PCXMC 2.0 enabled us to determine patient organ doses depending on weight, height and gender. Alternatively, the measurement of an in phantom dose indicator combined with proper correction coefficients can be a useful tool for a first dose estimation of in-field organs. The data and coefficients provided in this study can be applied to any patient undergoing a scan by an Elekta XVI equipment. [ABSTRACT FROM AUTHOR]

Purpose: In vivo radiobiology experiments involving partial body irradiation (PBI) of mice are of major importance because they allow for the evaluation of individual organ tolerance; overcoming current limitations of experiments using lower dose, whole body irradiation. In the current study, the authors characterize and validate an effective and efficient apparatus for multiple animal PBI, directed to the head, thorax, or abdomen of mice. Methods: The apparatus is made of polymethylmethacrylate and consists of a rectangular parallelepiped prism (40 cm×16 cm×8 cm), in which five holes were drilled to accommodate standard 60 ml syringes, each housing an unanesthetized, fully immobilized mouse. Following CT-scanning and radiotherapy treatment planning, radiation fields were designed to irradiate the head, thorax, or abdomen of the animal. Thermoluminescent dosimeters (TLDs) were used to confirm the treatment planning dosimetry for primary beam and scattered radiation. Results: Mice are efficiently placed into 60 ml syringes and immobilized, without the use of anesthetics. Although partial rotational movement around the longitudinal axis and a minor 2 mm forward/backward movement are permitted, this does not compromise the irradiation of the chosen body area. TLDs confirmed the dose values predicted by the treatment planning dosimetry, both for primary beam and scattered radiation. Conclusions: The customized PMMA apparatus described and validated is cost-effective, convenient to use, and efficient in performing PBI without the use of anesthesia. The developed apparatus permits the isolated irradiation of the mouse head, thorax, and abdomen. Importantly, the apparatus allows the delivery of PBI to five mice, simultaneously, representing an efficient way to effectively expose a large number of animals to PBI through multiple daily fractions, simulating clinical radiotherapy treatment schedules. [ABSTRACT FROM AUTHOR]

Purpose: There is an increasing number of cancer survivors who are at risk of developing late effects caused by ionizing radiation such as induction of second tumors. Hence, the determination of out-of-field dose for a particular treatment plan in the patient's anatomy is of great importance. The purpose of this study was to analytically model the stray dose according to its three major components. Methods: For patient scatter, a mechanistic model was developed. For collimatorscatter and head leakage, an empirical approach was used. The models utilize a nominal beam energy of 6 MeV to describe two linear accelerator types of a single vendor. The parameters of the models were adjusted using ionization chamber measurements registering total absorbed dose in simple geometries. Whole-body dose measurements using thermoluminescent dosimeters in an anthropomorphic phantom for static and intensity-modulated treatment plans were compared to the 3D out-of-field dose distributions calculated by a combined model. Results: The absolute mean difference between the whole-body predicted and the measured out-of-field dose of four different plans was 11% with a maximum difference below 44%. Computation time of 36?000 dose points for one field was around 30 s. By combining the model-calculated stray dose with the treatment planning system dose, the whole-body dose distribution can be viewed in the treatment planning system. Conclusions: The results suggest that the model is accurate, fast and can be used for a wide range of treatment modalities to calculate the whole-body dose distribution for clinical analysis. For similar energy spectra, the mechanistic patient scattermodel can be used independently of treatment machine or beam orientation. [ABSTRACT FROM AUTHOR]

Voxel-level dosimetry based on nuclear medicine images offers patient-specific personalization of radiopharmaceutical therapy (RPT) treatments. Clinical evidence is emerging demonstrating improvements in treatment precision in patients when voxel-level dosimetry is used compared to MIRD. Voxel-level dosimetry requires absolute quantification of activity concentrations in the patient, but images from SPECT/CT scanners are not quantitative and require calibration using nuclear medicine phantoms. While phantom studies can validate a scanner's ability to recover activity concentrations, these studies provide only a surrogate for the true metric of interest: absorbed doses. Measurements using thermoluminescent dosimeters (TLDs) are a versatile and accurate method of measuring absorbed dose. In this work, a TLD probe was manufactured that can fit into currently available nuclear medicine phantoms for the measurement of absorbed dose of RPT agents. Next, 748 MBq of I-131 was administered to a 16 ml hollow source sphere placed in a 6.4 L Jaszczak phantom in addition to six TLD probes, each holding 4 TLD-100 1 × 1 × 1 mm TLD-100 (LiF:Mg,Ti) microcubes. The phantom then underwent a SPECT/CT scan in accordance with a standard SPECT/CT imaging protocol for I-131. The SPECT/CT images were then input into a Monte Carlo based RPT dosimetry platform named RAPID and a three dimensional dose distribution in the phantom was estimated. Additionally, a GEANT4 benchmarking scenario (denoted 'idealized') was created using a stylized representation of the phantom. There was good agreement for all six probes, the differences between measurement and RAPID ranged between -5.5% and 0.9%. The difference between the measured and the idealized GEANT4 scenario was calculated and ranged from -4.3% and -20.5%. This work demonstrates good agreement between TLD measurements and RAPID. In addition, it introduces a novel TLD probe that can be easily introduced into clinical nuclear medicine workflows to provide QA of image-based dosimetry for RPT treatments., (Creative Commons Attribution license.)

Purpose: A method was developed utilizing Cherenkov imaging for rapid and thorough determination of the two gantry angles that produce the most uniform treatment plane during dual-field total skin electron beam therapy (TSET). Methods: Cherenkov imaging was implemented to gather 2D measurements of relative surface dose from 6 MeV electron beams on a white polyethylene sheet. An intensified charge-coupled device camera time-gated to the Linac was used for Cherenkov emission imaging at sixty-two different gantry angles (1° increments, from 239.5° to 300.5°). Following a modified Stanford TSET technique, which uses two fields per patient position for full body coverage, composite images were created as the sum of two beam images on the sheet; each angle pair was evaluated for minimum variation across the patient region of interest. Cherenkov versus dose correlation was verified with ionization chamber measurements. The process was repeated at source to surface distance (SSD) = 441, 370.5, and 300 cm to determine optimal angle spread for varying room geometries. In addition, three patients receiving TSET using a modified Stanford six-dual field technique with 6 MeV electron beams at SSD = 441 cm were imaged during treatment. Results: As in previous studies, Cherenkov intensity was shown to directly correlate with dose for homogenous flat phantoms (R² = 0.93), making Cherenkov imaging an appropriate candidate to assess and optimize TSET setup geometry. This method provided dense 2D images allowing 1891 possible treatment geometries to be comprehensively analyzed from one data set of 62 single images. Gantry angles historically used for TSET at their institution were 255.5° and 284.5° at SSD = 441 cm; however, the angles optimized for maximum homogeneity were found to be 252.5° and 287.5° (+6° increase in angle spread). Ionization chamber measurements confirmed improvement in dose homogeneity across the treatment field from a range of 24.4% at the initial angles, to only 9.8% with the angles optimized. A linear relationship between angle spread and SSD was observed, ranging from 35° at 441 cm, to 39° at 300 cm, with no significant variation in percent-depth dose at midline (R² = 0.998). For patient studies, factors influencing in vivo correlation between Cherenkov intensity and measured surface dose are still being investigated. Conclusions: Cherenkov intensity correlates to relative dose measured at depth of maximum dose in a uniform, flat phantom. Imaging of phantoms can thus be used to analyze and optimize TSET treatment geometry more extensively and rapidly than thermoluminescent dosimeters or ionization chambers. This work suggests that there could be an expanded role for Cherenkov imaging as a tool to efficiently improve treatment protocols and as a potential verification tool for routine monitoring of unique patient treatments. [ABSTRACT FROM AUTHOR]

Environment radiations in vault rooms resulting from Axesse linac use was assessed at Medical University Hospital using Thermoluminescent dosimeters (TLDs) during the use of the new radiation treatment known as volumetric modulated arc therapy (VMAT) in the treatment of nasopharyngeal cancer (NPC). The TLD-100H was calibrated using linac 6 MV photons. A total of 75 measurement points of the TLD-100H were utilized for environmental monitoring. The measured environment radiations were then visualized as three-dimensional graphical representations. Environment radiations were visualized using colored three-dimentional graphical representations. The radiations in NPC treatment of Rando phantom was found to reach levels up to 370 mSv/treatment. Many researchers consider TLD, which is the most cost-effective method to environment radiations. The minimum detectable dose (MDD) was also identified to demonstrate the reliability of the TLD approach. Quantitative results that provide practical guidance with regarded radiation protections. Potentially hazardous of secondary radiations from the operating linac is evaluated with regard to its potential health effects on both patients and the public.KEY POINTSThis work tried to evaluate the environment radiation and minimal detectable limit of TLD inside the LINAC maze. [ABSTRACT FROM PUBLISHER]

Background: The use of in vivo dosimetry with thermolumiscent dosimeters (TLDs) as a veritable means of quality control in conventional radiotherapy procedures was determined in this work. Aim: The objective of this study was to determine the role of in vivo dosimetry with thermoluminescent dosimeters (TLDs) as part of quality control and audit in conventional radiotherapy procedures delivered with Co-60 teletherapy machine. Subjects and Methods: Fifty-seven patients with cancers of the breast, pelvis, head and neck were admitted for this study. TLD system at the Radiation Monitoring and Protection Centre, Lagos State University, Ojo, Lagos-Nigeria was used for the in vivo entrance dose readings. All patients were treated with Co-60 (T780c) teletherapy machine at 80 cm source to surface distance located at Eko Hospitals, Lagos. Two TLDs were placed on the patient surface within 1 cm from the center of the field of treatment. Build-up material made of paraffin wax with a density of 0.939 g/cm³ and a thickness 0.5 cm was placed on top of the TLDs. A RADOS RE 200 TLD reader was used to read out the TLDs over 12 s and at a temperature of 300℃. Results: The results showed that there was no significant difference between the expected dose and measured dose of breast (P = 0.11), H and N (P = 0.52), and pelvis (P = 0.31) patients. Furthermore, percentage difference between expected dose and measured dose of the three treatment sites were not significantly different (P = 0.11). More so, 88.9% (16/18) treated breast, 91.3% (21/23) pelvis, and 86.7% (13/15) H and N patients had percentage deviation difference less than 5%. In general, 89.3% (50/56) patients admitted for this study had their percentage deviation difference below 5% recommended standard limit. Conclusion: The values obtained establish that there are no major differences from similar studies reported in literature. This study was also part of quality control and audit of the radiotherapy procedures in the center as expected by national and international regulatory bodies. [ABSTRACT FROM AUTHOR]

Concave eye applicators with 90 Sr/ 90 Y and 106 Ru/ 106 Rh beta ray sources are usually used in brachytherapy for the treatment of superficial intraocular tumors as uveal melanoma with thickness up to 5 mm. The calculation of the dose delivered to the eye is carried out based on the data present in the beta source calibration certificate. Therefore, it would be interesting to have a system that could evaluate that dose. In this work, an eye phantom to be used with 106 Ru/ 106 Rh betatherapy applicators was developed in solid water. This phantom can hold nine micro-cube thermoluminescent (TL) dosimeters, TLD-100. The characteristics of the TL response of the dosimeters, namely reproducibility and individual sensitivity, were determined for a 60 Co source. Using Monte Carlo code MCNPX, the dose to a water eye was determined at different depths. Exposing the eye phantom with TL dosimeters to the 106 Ru/ 106 Rh applicator, it is possible to assess calibration factors using the dose values obtained by Monte Carlo simulation to each depth. Using mean calibration factors, dose values obtained by TL dosimetry were compared to the data present in the applicators certificate. Mean differences for both applicators were lower than ±10%, maximum value 17% and minimum value 0.08%. Considering that the certificate values present an uncertainty of ±20%, the calibration procedure and the developed phantom are validated and can be applied. [ABSTRACT FROM AUTHOR]

Purpose: Microbeam radiation therapy (MRT) is a still preclinical tumor therapy approach that uses arrays of a few tens of micrometer wide parallel beams separated by a few 100 μm. The production, measurement, and planning of such radiation fields are a challenge up to now. Here, the authors investigate the feasibility of radiochromic film dosimetry in combination with a microscopic readout as a tool to validate peak and valley doses in MRT, which is an important requirement for a future clinical application of the therapy. Methods: Gafchromic® HD-810 and HD-V2 films are exposed to MRT fields at the biomedical beamline ID17 of the European Synchrotron Radiation Facility (ESRF) and are afterward scanned with a microscope. The measured dose is compared with Monte Carlo calculations. Image analysis tools and film handling protocols are developed that allow accurate and reproducible dosimetry. The performance of HD-810 and HD-V2 films is compared and a detailed analysis of the resolution, noise, and energy dependence is carried out. Measurement uncertainties are identified and analyzed. Results: The dose was measured with a resolution of 5×1000 μm² and an accuracy of 5% in the peak and between 10% and 15% in the valley region. As main causes for dosimetry uncertainties, statistical noise, film inhomogeneities, and calibration errors were identified. Calibration errors strongly increase at low doses and exceeded 3% for doses below 50 and 70 Gy for HD-V2 and HD-810 films, respectively. While the grain size of both film types is approximately 2 μm, the statistical noise in HD-V2 is much higher than in HD-810 films. However, HD-810 films show a higher energy dependence at low photon energies. Conclusions: Both film types are appropriate for dosimetry in MRT and the microscope is superior to the microdensitometer used before at the ESRF with respect to resolution and reproducibility. However, a very careful analysis of the image data is required. Dosimetry at low photon energies should be performed with great caution due to the energy sensitivity of the films. In this respect, HD-V2 films showed to have an advantage over HD-810 films. However, HD-810 films have a lower statistical noise level. When a higher resolution is required, e.g., for the dosimetry of pencil beam irradiations, noise may render HD-V2 films inapplicable. [ABSTRACT FROM AUTHOR]

The automated Risø TL/OSL Reader Model DA-20, often used in dating and retrospective dosimetry, was examined for possible applications in thermoluminescent dosimetry related to radiation protection. The investigations revealed that performance of the DA-20 is comparable with that of the Harshaw 3500 manual reader, which was used as a reference instrument. All studied parameters, like stability, reproducibility, low-dose measuring capabilities, were at the same level or only somewhat inferior to those of Harshaw 3500. In particular, using the highly-sensitive LiF:Mg,Cu,P dosimeters, it is possible to measure doses at the microgray level. The DA-20 reader possesses built-in alpha and beta sources, which cause an increased radiation background. At positions just under the closed sources the dose-rate rises to about 50 μGy/h. When the 90 Sr/ 90 Y source is open a quite high dose-rate of 100 mGy/h was measured at the position adjacent to the one being irradiated. Additionally the TLD response to the background radiation significantly depends on the TLD type (atomic number), as the radiation leaking through shielding is composed of low-energy photons. The dose-rate under the closed 241 Am source was over 10 times higher, when measured with CaF 2 dosimeters, than with LiF. In spite of these problems, the DA-20 reader due to its good stability, reproducibility and sensitivity, combined with such obvious benefits as a 48-dosimeter carousel, temperatures up to 700 °C and full automatics of measurements control, encourages the opinion that the DA-20 Risø reader can be successfully used in practical dosimetric measurements. [ABSTRACT FROM AUTHOR]