Passive Dosimeters Research Articles

On the acceptance, commissioning, and quality assurance of electron FLASH units.

FLASH or ultra-high dose rate (UHDR) radiation therapy (RT) has gained attention in recent years for its ability to spare normal tissues relative to conventional dose rate (CDR) RT in various preclinical trials. However, clinical implementation of this promising treatment option has been limited because of the lack of availability of accelerators capable of delivering UHDR RT. Commercial options are finally reaching the market that produce electron beams with average dose rates of up to 1000Gy/s. We established a framework for the acceptance, commissioning, and periodic quality assurance (QA) of electron FLASH units and present an example of commissioning. A protocol for acceptance, commissioning, and QA of UHDR linear accelerators was established by combining and adapting standards and professional recommendations for standard linear accelerators based on the experience with UHDR at four clinical centers that use different UHDR devices. Non-standard dosimetric beam parameters considered included pulse width, pulse repetition frequency, dose per pulse, and instantaneous dose rate, together with recommendations on how to acquire these measurements. The 6- and 9-MeV beams of an UHDR electron device were commissioned by using this developed protocol. Measurements were acquired with a combination of ion chambers, beam current transformers (BCTs), and dose-rate-independent passive dosimeters. The unit was calibrated according to the concept of redundant dosimetry using a reference setup. This study provides detailed recommendations for the acceptance testing, commissioning, and routine QA of low-energy electron UHDR linear accelerators. The proposed framework is not limited to any specific unit, making it applicable to all existing eFLASH units in the market. Through practical insights and theoretical discourse, this document establishes a benchmark for the commissioning of UHDR devices for clinical use.

Thermoluminescence characteristics of gamma-irradiated Gd:Mg doped silica glass

This study explores the characteristics of thermoluminescence (TL) yield of silica glass doped with Gd2O3 and MgO for dosimetry via sol-gel route, with varying concentrations of rare earth metal oxides, ranging from 0.1 to 0.8 mol%. Gamma irradiation was delivered using 1.25 MeV 60Co, with entrance doses of 2–10 Gy. The characterization of Gd:Mg-doped SiO2 included assessing TL dose response, sensitivity, linearity index, glow curve, and fading. It has been found that 0.2 mol% Gd:Mg-doped SiO2 shows promising TL dosimetric properties due to its high linearity, high sensitivity, and low thermal fading. In addition, it demonstrated exceptional dosimetric response across the entire dose range studied, with a coefficient of determination R2 exceeding 91%. A computerized glow curve deconvolution method was conducted to determine the kinetic parameters by using Glowfit software. The glow curves include five peaks associated with activation energies and frequency factors with values 0.88–2.42 eV and 5.58 × 106–7.22 × 1026 s−1, respectively. The 0.2 mol% Gd:Mg-doped SiO2 demonstrates minimal fading effects, retaining a significant portion of the TL signal with ∼33% of the initial signal lost over 28 days post-irradiation. The results indicate that the Gd:Mg-doped SiO2 offers a promising performance as a low-cost passive radiation dosimeters.

A modular, high dynamic range passive neutron dosimeter and imaging diagnostic.

The multi-decade neutron dosimeter and imaging diagnostic (MDND) is a passive diagnostic that utilizes the polyethylene (n, p) nuclear reaction to enhance the diagnostic's sensitivity for time and energy integrated neutron measurements in the range of 2.45-14.1MeV. The MDND utilizes a combination of radiochromic film, phosphor image plates, and solid-state nuclear track detectors, with the goal of providing several orders of magnitude of dynamic range in terms of measured neutron fluence. The diagnostic design was guided by simulations in the Monte Carlo N-Particle (MCNP) transport code to determine the optimum thickness of the polyethylene convertor for maximum proton fluence incident on the detection medium as a function of incident neutron energy. In addition, the simulation results of complete diagnostic assemblies, or "stacks," were used to determine the total dynamic range of an MDND in terms of measured neutron source yield, which was found to be between around 107 and 1015 emitted into 4π with the detector located 1m away from the source. Complimentary to these simulations, individual detectors within a stack were simulated and analyzed to determine response as a function of neutron energy and yield. This work presents the diagnostic design, MCNP simulation results, and analysis of expected signals for varying neutron sources.

Passive Dosimeters for Radiation Dosimetry: Materials, Mechanisms, and Applications

AbstractPassive dosimeters enabling accurate measurement of doses from gamma rays to visible light are necessary to ensure efficient utilization of electromagnetic radiation in numerous fields like medical diagnostics and industrial manufacturing. The specific requirements for dosimeters in terms of dosimetry range, sensitivity, accuracy, and stability for each application have led to the development of various dosimeters based on new materials and new mechanisms. Here, a comprehensive review of different types of dosimeters classified according to the response signal, namely electron paramagnetic resonance, electrical, and optical, is provided. This review starts with a general introduction to dosimetry, a classification of dosimeters, and an elucidation of the necessity of dosimeters in various ranges of the electromagnetic spectrum. This is followed by an overview of the fundamental requirements of dosimeters, an explanation of the general dosimetry procedure, and the dosimetric quantities. Emphasis is given to the working mechanism, the design concept, and applications of each type of dosimeter as well as their respective strengths and drawbacks. Challenges and prospects are presented at the end of the review. This review provides an insightful overview of the material‐mechanism‐characteristics‐application relationship of different types of dosimeters that hopefully can serve as inspiration for the development of new devices.

Comparison of experimental measurements and fast Monte Carlo simulations for typical set-ups in fluoroscopically-guided interventional procedures

PyMCGPU-IR is an application based on the Monte Carlo code MCGPU-IR that automatically retrieves procedure information from X-ray systems and medical worker positions from a tracking camera system. PyMCGPU-IR calculates personal dose equivalent values, doses in organs and effective dose values for both patient and medical staff in interventional radiology procedures and displays them visually. The code's main advantage lies in its time efficiency, enabling simulations in under 2 min with statistical uncertainties below 5% (k = 2).This study involved testing in a hospital room using an interventional X-ray system. A RANDO phantom simulated the patient, with passive dosimeters affixed to the back for measuring skin dose values. A PMMA slab phantom represented the operator, with passive and active dosimeters affixed to its front surface to measure Hp(10). The irradiation conditions were simulated with PyMCGPU-IR using voxelized geometries to represent both phantoms. Results demonstrate good agreement between PyMCGPU-IR simulations and measured patient skin dose values, with differences of up to 5% for mean skin dose and up to 14% for the peak skin dose. Concerning Hp(10) values on the operator phantom, PyMCGPU-IR calculated values fall within the uncertainty ranges of dosimeter measurements for most points. The highest Hp(10) discrepancy is 42%, which is acceptable when compared with the typical variability observed between active and passive personal dosimeters measurements in interventional radiology. The results demonstrate PyMCGPU-IR's satisfactory performance for patient and personal dosimetry, compared to existing solutions like commercial skin dose calculation software and personal physical dosimeters.

Radiophotoluminescence response of LiF:Mg,Ti pellets irradiated with clinical proton beams in the 70–200 MeV energy range

Lithium fluoride doped with Mg and Ti (LiF:Mg,Ti) has been used for several decades as thermoluminescent dosimeter material, but recently also its radiophotoluminescence has been investigated for applications in dosimetry. In this work, LiF:Mg,Ti pellets (TLD-100) were irradiated in a water phantom at CNAO (Pavia, Italy) with therapeutic proton beams at five energies from 70 to 200 MeV in the dose range from 2 to 20 Gy. After irradiation, their visible radiophotoluminescence spectra were measured in controlled conditions and the spectrally-integrated red emission response of radiation-induced color centers has been investigated. The radiophotoluminescence signal, excited by a 445 nm continuous wave laser, was integrated within a 50 nm-wide band around the emission peak of the F2 color centers, located around 670 nm in LiF. The spectrally-integrated signal of the samples irradiated at the energy of 147.7 MeV exhibited a linear dependence with dose. Moreover, this radiophotoluminescence response appears independent from Linear Energy Transfer in the range from 0.8 to 1.6 keV/μm in all the samples irradiated at the dose of 5 Gy. Such independence was found up to 10.3 keV/μm in samples irradiated within two spread out Bragg peaks made of 36 energy components in the entire investigated proton energy range. The radiophotoluminescence response of the TLD-100 pellets was compared to that of nominally-pure LiF crystals irradiated in the same conditions, which show a similar behavior. The results are encouraging for the exploitation of TLD-100 pellets as passive solid-state radiophotoluminescent dosimeters for proton therapy.

The shape of the TLD-300 glow curve as a function of the energy for photons below 30 keV: Application to triboluminescence X-rays from peeling adhesive tape

The thermoluminescent material CaF2(Tm), known as TLD-300 (Harshaw/Bicron), shows a remarkable dependence of its glow curve shape on the quality of the radiation field. The quotient of high-temperature (maximum at about 265 °C) and low-temperature peaks (maximum at about 175 °C) depends strongly on LET (ions) and photon energy. The shape of the glow curve is parameterized by the high-to-low-temperature ratio, HLTR, a decreasing function of photon energy.Our goal has been to investigate the TLD-300 glow curve shape for six photon energies between 6 and 28 keV, and to apply this extended HLTR calibration to determine the effective energy of triboluminescence-generated X-rays (TGXs) produced when peeling adhesive tape in vacuum.For calibration, TLD-300 chips were exposed to X-rays from a W-anode tube (9.7–27.7 keV effective energies), X-rays from a Cu-anode tube (8.0 keV) and a 55Fe radioactive source (5.9 keV). The chips were subjected to an annealing protocol designed to improve the stability of the low-temperature peaks. Doses were low and deconvolution into 7 peaks was performed with custom-made software. For the TGXs investigation, TLD-300 chips and TLD-100 microcubes were exposed inside a vacuum chamber to radiation generated by the peeling of adhesive tape from its own backing. The dosimeters, located at different angular positions with respect to the tape, were covered with a 21-μm thick layer of Mylar (Dupont Tejjin Films) to eliminate stray radiation and block any UV light that may be emitted along with the TGXs. TLD-300 were thermally handled as in calibration, and the HLTR indicated the effective energy. Microcubes were used as monitors of a controlled exposure.The new calibration data confirmed the previous trend and showed consistency with existing HLTR measurements above 30 keV (after correcting by the different annealing procedures). The TGXs TLD-300 glow curves showed the presence of a low-temperature peak below those included in the usual deconvolution. The measured HLTR indicated effective energies close to 7 keV and constant over a wide range of observation angles.The extended calibration validates the use of this technique to evaluate photon energies below the limits investigated previously. For the investigation of TGXs, TLDs have been used as passive dosimeters, offering new possibilities in cases where pileup would be a limiting factor for active solid-state active detectors. The difference in glow curve shapes between the TGXs and the calibration photons offers a tool for further investigation of processes induced by surface electrification.

MR compatible detectors assessment for a 0.35 T MR-linac commissioning

PurposeTo assess a large panel of MR compatible detectors on the full range of measurements required for a 0.35 T MR-linac commissioning by using a specific statistical method represented as a continuum of comparison with the Monte Carlo (MC) TPS calculations. This study also describes the commissioning tests and the secondary MC dose calculation validation.Material and methodsPlans were created on the Viewray TPS to generate MC reference data. Absolute dose points, PDD, profiles and output factors were extracted and compared to measurements performed with ten different detectors: PTW 31010, 31021, 31022, Markus 34045 and Exradin A28 MR ionization chambers, SN Edge shielded diode, PTW 60019 microdiamond, PTW 60023 unshielded diode, EBT3 radiochromic films and LiF µcubes. Three commissioning steps consisted in comparison between calculated and measured dose: the beam model validation, the output calibration verification in four different phantoms and the commissioning tests recommended by the IAEA-TECDOC-1583.Main resultsThe symmetry for the high resolution detectors was higher than the TPS data of about 1%. The angular responses of the PTW 60023 and the SN Edge were − 6.6 and − 11.9% compared to the PTW 31010 at 60°. The X/Y-left and the Y-right penumbras measured by the high resolution detectors were in good agreement with the TPS values except for the PTW 60023 for large field sizes. For the 0.84 × 0.83 cm2 field size, the mean deviation to the TPS of the uncorrected OF was − 1.7 ± 1.6% against − 4.0 ± 0.6% for the corrected OF whereas we found − 4.8 ± 0.8% for passive dosimeters. The mean absolute dose deviations to the TPS in different phantoms were 0 ± 0.4%, − 1.2 ± 0.6% and 0.5 ± 1.1% for the PTW 31010, PTW 31021 and Exradin A28 MR respectively.ConclusionsThe magnetic field effects on the measurements are considerably reduced at low magnetic field. The PTW 31010 ionization chamber can be used with confidence in different phantoms for commissioning and QA tests requiring absolute dose verifications. For relative measurements, the PTW 60019 presented the best agreement for the full range of field size. For the profile assessment, shielded diodes had a behaviour similar to the PTW 60019 and 60023 while the ionization chambers were the most suitable detectors for the symmetry. The output correction factors published by the IAEA TRS 483 seem to be applicable at low magnetic field pending the publication of new MR specific values.

An Italian InterLaboratory comparison on personal dose equivalent for dosimetry services: promoting measurements reliability and addressing new digital challenges

An InterLaboratory Comparison on personal dose equivalent, Hp(10), a fundamental part of radiation protection dosimetry measurements, was organized aiming at evaluating the measurement capability of dosimetry services across Italy, in order to ensure the reliability of the measurements. For the intercomparison, each participant sent their own passive dosimeters, which were exposed to gamma radiation beams emitted from a S-Cs source and to medium-energy filtered X-ray beams of the wide spectrum series, at the ISO 4037-1 W-80 quality. Results were evaluated by applying the statistical estimator R, which compares the communicated dose equivalent values and the reference, assigned values, and then evaluated using trumpet curves. Data were acquired using web forms, collected in internal databases, and processed using statistical software, aiming at the automation of analysis and preparation of technical reporting. Results indicate a good level of maturity in the measurement capabilities in radiation protection dosimetry in the italian dosimetry services who participated. The intercomparison was an opportunity for mutual improvement between the participating dosimetric services and the organizing institute: the former were able to compare themselves and have their capabilities assessed from an external provider; while, the latter had the chance to improve their management and organization skills for a large, multi-lateral intercomparison.

Investigation of the dose-response linearity of guar gum for gamma-ray dosimetry at radiation processing levels using Raman spectroscopy

Abstract In this experimental work, guar gum powder was exposed to gamma radiation from a 60Co source at absorbed doses of 0, 10, 30, 50, 80, 100, 150 kGy at dose rate of 1.62 Gy/s. Raman spectroscopy was applied to measure the intensity of the samples ranging from of 500–4600 cm−1. The intensity versus Raman shift was evaluated at 3800–4000 cm−1. Then the curve was fitted linearly. The slope of the lines was determined in each absorbed dose. Results indicated that the absolute values of the slope of each line were enhanced with increasing the absorbed dose. This trend was linear within the absorbed dose ranging from of 0–50 kGy, in which was saturated after 80 kGy. Results showed that guar gum can be applied as a passive dosimeter at radiation processing level.

Performance evaluation of radon active sensors and passive dosimeters at low and high radon concentrations

Radon is a naturally occurring radioactive gas that has the potential to accumulate in buildings and over time, causes lung cancer in humans. Present methods for radon measurements are disparate, which pose challenges to benchmark radon concentrations and to accurately assess the population's received dose. This paper presents a comprehensive performance evaluation of radon dosimeters and three grades of active radon sensors: consumer-, medium- and research-grade. The measurements were performed at relatively low (300 Bq/m3) and high (2′000–3′000 Bq/m3) radon levels. Tests were conducted in an atomic shelter, with stable temperature and humidity conditions. The active sensors differed in absolute accuracy and dynamic performance (time-dependent correlations) according to their grade. Research-grade sensors performed marginally better than medium-grade sensors, and significantly better than consumer-grade sensors. Relative to the reference, the error (percentage difference between the reference and the sensors) was below 5 % for research- and medium-grade sensors, and nearly 10 % for consumer-grade sensors at high radon levels. Performance of sensors diminished at low radon levels, except for research-grade sensors. Passive dosimeters generally performed better at high radon levels than at low ones. Their longer exposure time was associated with increased measurement reliability. These results highlight the need for understanding the purpose of measurements in order to select an adequate radon detector, and ultimately, reduce measurement and interpretation errors. This study raises awareness among researchers, radon professionals and the general public regarding the performances of different active radon sensors and passive dosimeters. It also sheds light on their respective scope of application.

Alpha radioactivity in Iraqi market foodstuff: Assessing annual effective dose and lifetime cancer risk

In this study, integrated passive radon dosimeters with solid-state nuclear trace detectors (CR-39 and CN-85) were used to determine the annual effective dose and excess cancer risk for 25 different food samples in the Iraqi market. The dosimeters were deployed after four weeks of the required radiological equilibrium between radon and radium in the samples stored in sealed beakers. These caps were then quickly replaced with other caps equipped with detectors and stored for 70 days. After the detectors were removed from the samples, an electrochemical etching process was performed in a water bath and sodium hydroxide solution to reveal the traces of alpha particles on the detector surface. Microscopic observations were performed using an optical microscope to quantify the traces present on the detector surface. The results showed that the average radon concentrations for the CR-39 detectors ranged from 3.80 to 7.32 Bq/kg, with an average of 5.51 Bq/m3, and for the CN-85 detectors ranged from 1.23 to 4.51 Bq/kg, with an average of 2.79 Bq/kg. The radium and uranium concentrations for the CR-39 detector ranged from 0.299 to 0.577 Bq/kg, with an average of 0.434 Bq/kg, and from 3.72 to 7.17 Bq/kg, with an average of 5.40 Bq/kg. Comparing all the results between the two detectors, it was found that the values recorded with the CR-39 were approximately twice those recorded with the CN-85. It is important to note that all recorded values are within internationally permissible limits and do not pose a threat to human health.

Radiation exposure assessment of nuclear medicine staff administering [177Lu]Lu-DOTA-TATE with active and passive dosimetry

BackgroundThe use of lutetium-177 (177Lu)-based radiopharmaceuticals in peptide receptor nuclear therapy is increasing, but so is the number of nuclear medicine workers exposed to higher levels of radiation. In recent years, [177Lu]Lu-DOTA-TATE has begun to be widely used for the treatment of neuroendocrine tumours. However, there are few studies evaluating the occupational radiation exposure during its administration, and there are still some challenges that can result in higher doses to the staff, such as a lack of trained personnel or fully standardised procedures. In response, this study aims to provide a comprehensive analysis of occupational doses to the staff involved in the administration of [177Lu]Lu-DOTA-TATE.ResultsA total of 32 administrations of [177Lu]Lu-DOTA-TATE (7.4 GBq/session) carried out by a physician and a nurse, were studied. In total, two physicians and four nurses were independently monitored with cumulative (passive) and/or real-time (active) dosemeters. Extremity, eye lens and whole-body doses were evaluated in terms of the dosimetric quantities Hp(0.07), Hp(3) and Hp(10), respectively. It was obtained that lead aprons reduced dose rates and whole-body doses by 71% and 69% for the physicians, respectively, and by 56% and 68% for the nurses. On average, normalised Hp(10) values of 0.65 ± 0.18 µSv/GBq were obtained with active dosimetry, which is generally consistent with passive dosemeters. For physicians, the median of the maximum normalised Hp(0.07) values was 41.5 µSv/GBq on the non-dominant hand and 45.2 µSv/GBq on the dominant hand. For nurses 15.4 µSv/GBq on the non-dominant and 13.9 µSv/GBq on the dominant hand. The ratio or correction factor between the maximum dose measured on the hand and the dose measured on the base of the middle/ring finger of the non-dominant hand resulted in a factor of 5/6 for the physicians and 3/4 for the nurses. Finally, maximum normalised Hp(3) doses resulted in 2.02 µSv/GBq for physicians and 1.76 µSv/GBq for nurses.ConclusionsIf appropriate safety measures are taken, the administration of [177Lu]Lu-DOTA-TATE is a safe procedure for workers. However, regular monitoring is recommended to ensure that the annual dose limits are not exceeded.

Neuroanatomical differences in Latinx children from rural farmworker families and urban non-farmworker families and related associations with pesticide exposure

Exposure to pesticides in humans may lead to changes in brain structure and function and increase the likelihood of experiencing neurodevelopmental disorders. Despite the potential risks, there is limited neuroimaging research on the effects of pesticide exposure on children, particularly during the critical period of brain development. Here we used voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) from magnetic resonance images (MRI) to investigate neuroanatomical differences between Latinx children (n = 71) from rural, farmworker families (FW; n = 48) and urban, non-farmworker families (NFW; n = 23). Data presented here serves as a baseline for our ongoing study examining the longitudinal effects of living in a rural environment on neurodevelopment and cognition in children. The VBM analysis revealed that NFW children had higher volume in several distinct regions of white matter compared to FW children. Tract-based spatial statistics (TBSS) of DTI data also indicated NFW children had higher fractional anisotropy (FA) in several key white matter tracts. Although the difference was not as pronounced as white matter, the VBM analysis also found higher gray matter volume in selected regions of the frontal lobe in NFW children. Notably, white matter and gray matter findings demonstrated a high degree of overlap in the medial frontal lobe, a brain region predominantly linked to decision-making, error processing, and attention functions. To gain further insights into the underlying causes of the observed differences in brain structure between the two groups, we examined the association of organochlorine (OC) and organophosphate (OP) exposure collected from passive dosimeter wristbands with brain structure. Based on our previous findings within this data set, demonstrating higher OC exposure in children from non-farmworker families, we hypothesized OC might play a critical role in structural differences between NFW and FW children. We discovered a significant positive correlation between the number of types of OC exposure and the structure of white matter. The regions with significant association with OC exposure were in agreement with the findings from the FW-NFW groups comparison analysis. In contrast, OPs did not have a statistically significant association with brain structure. This study is among the first multimodal neuroimaging studies examining the brain structure of children exposed to agricultural pesticides, specifically OC. These findings suggest OC pesticide exposure may disrupt normal brain development in children, highlighting the need for further neuroimaging studies within this vulnerable population.

FLASH radiotherapy using high-energy X-rays: Current status of PARTER platform in FLASH research

PurposeRecent studies indicated that ultrahigh dose rate (FLASH) radiation can reduce damage to normal tissue while maintaining anti-tumour activity compared to conventional dose rate (CONV) radiation. This paper provides a comprehensive description of the current status of the Platform for Advanced Radiotherapy Research (PARTER), which serves as the first experimental FLASH platform utilizing megavoltage X-rays and has facilitated numerous experiments. Methods and MaterialsPARTER was established in 2019 based on a superconducting linac to support experimental FLASH studies using megavoltage X-rays. Continuous upgrades have been made to the accelerator, collimators, flattening filters, monitors, other auxiliary devices, and irradiation process in order to achieve optimal results. Passive and active dosimeters are employed for measuring dose distribution and to ensure traceability of radiation doses. ResultsThe dose monitors and dosimeters demonstrate reliable performance with acceptable stability. At PARTER, the maximum mean dose rate is approximately 400 Gy/s at a surface-source distance of 20 cm (over 1000 Gy/s at smaller distances), with an instantaneous dose rate of approximately 8E5 Gy/s. Both passive and active dosimeters exhibit good linearity and agreement during FLASH X-ray irradiation. The monitors show good linearity to dose rate, with short-term fluctuations within 1.5 % for the diamond monitor. The discrepancy between measured absorbed dose and dose protocol is typically less than 4 %. The X-ray energy spectra on PARTER are comparable to those for megavoltage CONV linacs operating in flattening filter-free mode. The maximum field size of the FLASH beam is 4.5 cm × 4.5 cm. The FLASH dose profile demonstrates satisfactory flatness (1.04) and similar penumbra compared to clinical CONV linac, while the percentage depth dose curve of FLASH X-rays is steeper than that of the clinical megavoltage CONV X-ray. ConclusionsPARTER represents a pioneering platform for conducting megavolts FLASH X-ray irradiation in biological experiments. It effectively fulfills the requirements of preclinical research on megavoltage X-ray FLASH and undergoes continuous upgrades to meet increasingly demanding performance criteria.

PENDEKATAN ALGORITMA UNTUK EVALUASI DOSIS RADIASI DENGAN TLD-900 BARC PADA PENGUKURAN RADIASI ENERGI RENDAH

Accurate radiation dose evaluation for radiation workers is crucial to determine the radiation dose received from exposure. Using passive dosimeters such as TLD-900 can assist in monitoring and controlling radiation exposure by evaluating accumulated dose readings over a specific period. Due to its utilization in diverse radiation fields, the dose evaluation method should be able to differentiate the energy range employed. Energy dependence can pose a challenge in reading the received dose, particularly in the case of low-energy X-ray usage. Therefore, this study aims to develop an algorithm for individual equivalent dose evaluation Hp(10) in low-energy (<20 KeV) usage. The data will be obtained from the Nuclear Agency of Malaysia's Secondary Standard Dosimetry Laboratory (SSDL), including various ISO narrow series X-ray sources and several radioactive sources such as Cs-137, Co-60, Sr-90, Kr-85, and Pm-147. The evaluation method will involve a trumpet curve and ANSI bias plot, enabling an assessment of the performance of the developed algorithm. Ultimately, the algorithm will be used for long-term dose evaluation intercomparisons in low-dose reviews. The low-energy energy evaluation algorithm for equivalent doses has successfully been conducted. The algorithm performs very well in distinguishing energy types using the parameter r12. In contrast, the low-energy dose evaluation algorithm encounters difficulties due to the low-energy characteristics in energy deposition, which are similar for each element D. Keywords: Algorithm,radiation dose evaluation, TLD, Low Energy.

Prospective observational analysis of intraoperative radiation exposure with a mini C-arm intensifier in percutaneous forefoot surgery

IntroductionPercutaneous forefoot surgery has been associated with higher radiation exposure than the conventional approach. However, there is little data on forefoot surgery using a mini C-arm intensifier. We, therefore, conducted a prospective study to (1) evaluate the intraoperative radiation received by the surgeon during percutaneous forefoot surgery with a mini C-arm; (2) compare the radiation received by the surgeon with the guidelines for occupational exposure issued by the International Commission on Radiological Protection (ICRP) (20 millisieverts per year [mSv/year] for the whole body, 500mSv/year for the hands, and 20mSv/year for the lens of the eye); and (3) compare the radiation received during percutaneous forefoot surgery with that of the open approach, which has already been reported in the literature. HypothesisThe radiation received by the surgeon during percutaneous forefoot surgery with a mini C-arm is lower than the ICRP guidelines, and the findings reported in the literature. Materials and methodsThis prospective single-center study was conducted from September 2020 to May 2021. A total of 639 feet (i.e., 435 patients) were included. Of these 639 feet, 336 (52%) were hallux valgus repairs, 49 (8%) were stand-alone procedures of the lateral rays, and 124 (19%) were a combination of both. The radiation dose data was retrieved from the mini C-arm daily: dose-area product (DAP) in centigray per square centimeter (cGy/cm2) and radiation exposure duration in seconds. The doses received by the surgeon were collected every month by 4 passive dosimeters (hand, eye lens, and chest [on and under the lead apron]) and 2 active dosimeters (on and under the lead apron). ResultsThe DAP emitted by the mini C-arm during an operating day was 0.10±0.01cGy/cm2 (range, 0.0–3.9), and the mean daily radiation duration was 34.7±19.3seconds (range, 0.7–226.8). There was a mean of 8±8 (range, 1–18) elective procedures per operating day. The daily reading on the active dosimeter worn on the lead apron was 0.002±0 microSv (range, 0–0.04), while the one worn under the apron was 0.001±0 microSv (range, 0–0.03). The equivalent doses over the 7-month study period for the hand, eye lens, and chest (over and under the apron) were 0.14mSv, 0mSv, 0.22mSv, and 0mSv, respectively. Discussion/ConclusionThe radiation exposure in percutaneous forefoot surgery with a mini C-arm intensifier observed in our study was lower than the ICRP recommendations and literature findings during open surgery. Level of evidenceIV; prospective study without a control group.

Alanine/EPR dosimetry for mailed intercomparison at ocular proton therapy facilities-preliminary results for three centres for irradaitions at CCB IFJ PAN eyeline.

Quality control of therapeutic photon beams in the form of postal dose audits based on passive dosemeters is widely used in photon radiotherapy. On the other hand, no standardised dosimetry audit programme for proton centres has been established in Europe so far. We evaluated alanine/EPR dosimetry systems developed at the Istituto Superiore di Sanità (Italy), the Hasselt Universiteit (Belgium) and the Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences (Poland) for their applicability as a potential tool for routine mailed dose audits of passively scattered therapeutic proton beams. The evaluation was carried out in the form of an intercomparison. Dosemeters were irradiated in the 70MeV proton beam at ocular proton therapy facility in the Cyclotron Centre Bronowice at the Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences in Krakow. A very good agreement was found between the dose measured by three laboratories and the delivered dose determined with an ionisation chamber. This, together with the inherent properties of alanine, such as non-destructive readout, tissue equivalence, weak energy dependence, dose rate independence and insignificant fading, makes alanine a good candidate for a dosemeter used in postal auditing in proton ocular radiotherapy.

Monte Carlo Dosimetry Validation for X-Ray Guided Endovascular Procedures

Endovascular treatment is continuously gaining ground in vascular surgery procedures. However, current patient radiation dose estimation does not take into account the exact patient morphology and organs' composition. Monte Carlo (MC) simulation can accurately estimate the dose by recreating the irradiation process generated during X-ray-guided interventions. This study aimed to validate the MC simulation models by comparing simulated and measured dose distributions in endovascular aortic aneurysm repair (EVAR) procedures. We conducted a clinical study in patients treated for EVAR. Patient dose measurements were taken with passive dosimeters using Optically Stimulated Luminescence technology in 4 specific anatomical points on the skin: xiphoid process, pubic symphysis, right and left iliac crest. Dose measurements were compared to the corresponding simulated doses with the Geant4 Application for Emission Tomography (GATE) and GPU Geant4-based Monte Carlo Simulations (GGEMS) MC simulations softwares. The MC simulation took as input the computed tomography scan of the patient and the parameters of the imaging system (orientation angles, tube voltage, and aluminum filtration) and gives as output the three-dimensional (3D) dose map for each patient and angulation. A good agreement with real doses was found for doses simulated by the MC GATE method (P<0.0001; r=0.97; 95% confidence interval [CI] [0.96-0.98]), as well as for doses simulated by the GGEMS method (P<0.0001; r=0.96; 95% CI [0.94-0.97]). The mean relative error for all measurements was 5±5% in the MC GATE group and 6±5% in the GGEMS group. Process execution on GGEMS (6sec) was faster than the GATE MC simulation (5hr). Considering the current imaging settings, this study shows the potential of using the GATE and GGEMS MC simulations platforms to model the 3D dose distributions during EVAR procedures.

Dosimetry of the PIM1 Pion Beam at the Paul Scherrer Institute for Radiobiological Studies of Mice.

Significant past work has identified unexpected risks of central nervous system (CNS) exposure to the space radiation environment, where long-lasting functional decrements have been associated with multiple ion species delivered at low doses and dose rates. As shielding is the only established intervention capable of limiting exposure to the dangerous radiation fields in space, the recent discovery that pions, emanating from regions of enhanced shielding, can contribute significantly to the total absorbed dose on a deep space mission poses additional concerns. As a prerequisite to biological studies evaluating pion dose equivalents for various CNS exposure scenarios of mice, a careful dosimetric validation study is required. Within our ultimate goal of evaluating the functional consequences of defined pion exposures to CNS functionality, we report in this article the detailed dosimetry of the PiMI pion beam line at the Paul Scherrer Institute, which was developed in support of radiobiological experiments. Beam profiles and contamination of the beam by protons, electrons, positrons and muons were characterized prior to the mice irradiations. The dose to the back and top of the mice was measured using thermoluminescent dosimeters (TLD) and optically simulated luminescence (OSL) to cross-validate the dosimetry results. Geant4 Monte Carlo simulations of radiation exposure of a mouse phantom in water by charged pions were also performed to quantify the difference between the absorbed dose from the OSL and TLD and the absorbed dose to water, using a simple model of the mouse brain. The absorbed dose measured by the OSL dosimeters and TLDs agreed within 5-10%. A 30% difference between the measured absorbed dose and the dose calculated by Geant4 in the dosimeters was obtained, probably due to the approximated Monte Carlo configuration compared to the experiment. A difference of 15-20% between the calculated absorbed dose to water at a 5 mm depth and in the passive dosimeters was obtained, suggesting the need for a correction factor of the measured dose to obtain the absorbed dose in the mouse brain. Finally, based on the comparison of the experimental data and the Monte Carlo calculations, we consider the dose measurement to be accurate to within 15-20%.