Dose Measurements Research Articles

Assessment of tissue-air ratios in epoxy resin and PMMA phantoms for radiation dosimetry: findings from experimental measurements and Monte Carlo simulations.

This study assesses radiation doses in multi-slice computed tomography (CT) using epoxy resin and PMMA phantoms, focusing on the relationship between TAR (tissue air ratio) and kilovoltage peak (kVp). The research was conducted using a Hitachi Supria 16-slice CT scanner. An epoxy resin phantom was fabricated from commercially available materials, to simulate human tissue. The phantom contained four peripheral inserts and one central insert for dose measurement, with optically stimulated luminescent dosimeters positioned at various depths (2 to 10cm). Monte Carlo simulations were executed using the Geant4 Application for Tomographic Emission toolkit (GATE) to model photon transport, with the x-ray spectrum generated using SpekPy software. A non-linear fitting model was developed to describe the TAR-kVp relationship across different depths for epoxy resin and PMMA. Results indicated that TAR values were higher at low depths (2cm) and decreased with increasing depth, reflecting the x-ray beam's attenuation. For instance, at 80 kVp and 2cm depth, the experimental TAR for PMMA was 1.102 ± 0.011, closely matching the MC simulation value of 1.110 ± 0.036, resulting in a small difference of 0.7%. At a depth of 10cm, the experimental TAR for PMMA decreased to 0.245 ± 0.006, while the MC TAR was 0.248 ± 0.016, with a relative difference of 1.2%. Similar trends were observed for epoxy resin, where the experimental TAR ranged from 1.070 ± 0.014 at 2cm to 0.235 ± 0.009 at 10cm, while MC simulation values ranged from 1.080 ± 0.038 to 0.238 ± 0.017. Bland-Altman analysis confirmed these results, with mean differences of 0.008 for PMMA and 0.006 for epoxy resin, indicating high agreement between the experimental and simulated TAR values. This study highlights the importance of phantom material selection in dose assessment and the implications of TAR in dose correction within the context of diagnostic radiology.

Modelling and Validation of a 6 MV Compact Linear Accelerator via Monte Carlo Simulation using Geant4 Application for Tomographic Emission (GATE).

To accurately model and validate the 6 MV Elekta CompactTMlinear accelerator using the Geant4 Application for Tomographic Emission (GATE). In particular, this study focuses on the precise calibration and validation of critical parameters, including jaw collimator positioning, electron source nominal energy, flattening filter geometry, and electron source spot size, which are often not provided in technical documentation.
Methods: Simulation of the Elekta CompactTM6 MV linear accelerator was performed using the Geant4 Application for Tomographic Emission (GATE) v.9.1. A 50 cm x 50 cm x 50 cm water phantom was irradiated with a source-to-surface distance of 100 cm. Percentage Depth Dose Profile (PDD) and Lateral Dose Profile (Crossplane and Inplane) were assessed as reference dose measurements. The half-length field difference (FHLD) method was introduced to optimize the jaw collimator setup. Gamma index analysis was used to quantitatively assess the accuracy of the simulated dosimetry data in relation to the actual dose measurements.
Results: Crucial parameters of the Linac Head have been successfully optimized. The validation achieved Gamma-Index acceptance rates of 97.93% for the Depth Dose profile, 100% for the Crossplane (X) Dose Profile, and 93.98% for the Inplane (Y) Dose Profile, all meeting the 1%/1mm Gamma-Index criteria.
Conclusion: The simulation and calibration of the Elekta CompactTMLinac have achieved a reliable model with high fidelity in dosimetry calculations which could pave the way for the future development and application of new techniques using Elekta CompactTMLinear Accelerator.

Real-time dose measurement in minibeam radiotherapy using radioluminescence imaging.

Minibeam radiotherapy (MBRT) uses small parallel beams of radiation to create a highly modulated dose pattern. The aim of this study is to develop an optical radioluminescence imaging (RLI) approach to perform real-time dose measurement for MBRT. MBRT was delivered using an image-guided small animal irradiator equipped with a custom collimator. Five slabs of plastic scintillators with a thicknesses of 0.5, 1, 2, 3 and 10 mm were placed on top of a mouse phantom, to localize and measure the delivered dose. A thin radioluminescence film (Gd2O2S:Tb) was used to obtain the mini beam dose profile that was compared against GafChromic (GC) films measurements. The RLI signal was detected with a CMOS camera placed at 90 deg with respect to the beam axis. Monte Carlo (MC) simulations were also performed using TOPAS for comparison with the experimental results. The measured peak to valley dose ratio (PVDR) obtained with RLI was 16.7 in line with GC films measurements. The differences between peak and valley dimension were less that 3% with respect to GC measurements. Using RLI performed with the scintillator slabs, it was possible to localize and measure in real-time MBRT delivery on the mouse phantom. We proposed a novel method for MBRT dose localization and measurement in real-time based on RLI. The results we obtained are in good agreement with GC film measurements.

Influence of spatial redistribution of heterogeneities in proton beam characteristics.

The purpose of this study was to investigate the fundamental properties of spot-scanning proton beams and compare them to Monte Carlo (MC) simulations, both with and without CT calibration, using spatially diverse combinations of materials. A heterogeneous phantom was created by spatially distributing titanium, wax, and thermocol to generate six scenarios of heterogeneous combinations. Proton pencil beams ranging in energy from 100 to 226.2MeV were directed perpendicular to each heterogeneous combination, and the exit proton was measured using a Lynx scintillation detector and a Zebra Multi-Layer-Ionization-Chamber for depth dose and spot profile measurements, respectively. The identical measurement configuration was duplicated in the RayStation-TPS. The measured and simulated RayStation-MC beam characteristics were compared. The results showed that at 100MeV, the mean standard deviation of spot size was 5.66±0.27mm, while at 226.2MeV, it rapidly decreased to 3.37±0.07mm. The physical phantom showed a larger perturbation difference between measurement and MC simulation than the virtual phantom. MC overestimates ranges up to 1.5% in virtual phantoms, but underestimates ranges up to 5% in physical phantoms. Range perturbations over 1mm occurred in 35.7% of virtual phantom measurements and in 85.7% of physical phantom measurements. Despite using a CT artefact reduction approach and an accurate Monte-Carlo dose calculation algorithm, perturbations in proton characteristics were still observed. It is essential to be aware of the limits of the TPS in managing such heterogeneous combinations. It is recommended to perform more validation checks on heterogeneous combinations than on individual materials.

A novel analytic procedure for accurate patient surface dose measurement during computed tomography examination: systematic uncertainty correction related to incident X-ray direction

A novel analytic procedure for accurate patient surface dose measurement during computed tomography examination: systematic uncertainty correction related to incident X-ray direction

Evaluation of long axial field-of-view (LAFOV) PET/CT for post-treatment dosimetry in Yttrium-90 radioembolization of liver tumors: a comparative study with conventional SPECT imaging.

Long axial field-of-view (LAFOV) positron emission tomography/computed tomography (PET/CT) scanners enable high sensitivity and wide anatomical coverage. Therefore, they seem ideal to perform post-selective internal radiation therapy (SIRT) 90Y scans, which are needed, to confirm that the dose is delivered to the tumors and that healthy organs are spared. However, it is unclear to what extent the use of LAFOV PET is feasible and which dosimetry approaches results in accurate measurements. In this retrospective analysis, a total number of 32 patients was included (median age 71, IQR 14), which had hepatocellular carcinoma, cholangiocarcinoma, or liver metastases. All patients underwent SIRT, and the post-therapy scan was acquired on a single photon emission computed tomography/computed tomography (SPECT/CT) and a LAFOV Biograph Quadra PET/CT with a 20-minute acquisition time. Post-treatment dosimetry, regarding the tumor, whole-liver and lung (LMD) absorbed dose was done using an organ-wise (Simplicit90Y) and a voxel-wise approach (HERMIA Dosimetry) which used a semi-Monte Carlo algorithm. The lung shunt fraction (LSF) was also measured using the voxel-wise approach and compared to the planned. The planning, post-treatment SPECT and PET (SPECTpre, SPECTpost, PETpost) median tumor doses based on the organ-wise dosimetry were 276.0Gy (200.0-330.0Gy), 232.0Gy (158.5-303.5Gy) and 267.5Gy (182.5-370.8Gy). In contrast, the median voxel-wise PETpost dose was significantly smaller than the planned SPECTpre (152.5Gy (94.8-223.8Gy); p < 0.00001). Moreover, the median tumor absorbed dose at 90% (D90) of the tumor volume was significantly higher in SPECTpost compared with PETpost (123.5Gy; 81.5-180.0 vs. 30.5Gy; 11.3-106.3; p < 0.00001). The PETpost measured LSF was significantly lower compared to the planned SPECTpre (0.89%; 0.4-1.3% vs. 2.3%; 1.5-3.6%; p < 0.0001). Similarly, the measured PETpost median LMD was considerably lower to the planned SPECTpre (1.2Gy; 0.6-2.3 vs. 2.5Gy; 1.4-4.7; p < 0.0001). LAFOV PET enabled the direct measurement of post therapy lung dose and tumor doses that correlated well with the planned treatment doses. However, current voxel-wise-based tumor dosimetry seems to be inaccurate for LAFOV PET. In addition, dose volume histogram-based metrics also significantly underestimate the delivered dose. Therefore, improved dosimetry tools are needed for reliable voxel-wise 90Y dosimetry to leverage the sensitivity and spatial resolution of LAFOV PET scanners.

Study of the uncertainty of measurements of gamma radiation from Cesium-137 and Cobalt-60 sources

Radiation dosimetry is a key element in medical, industrial, and scientific activities involving the use of ionizing radiation. Accurate measurements of radiation doses ensure the safety and effectiveness of radiological practices, which is critically important for protecting patients during medical procedures, adhering to industrial safety standards, and conducting scientific research. International studies are carried out to achieve this high measurement accuracy. The National Scientific Centre “Institute of Metrology” (NSC “Institute of Metrology”) actively participates in international projects aimed at improving the accuracy and consistency of radiation dosimetry. These projects unite National Metrology Institutes (NMIs) to standardize measurement and calibration methods, thereby enhancing the systems of ionizing radiation dosimetry. The relevance of such projects is driven by the widespread use of ionizing radiation in medicine and industry. In medicine, particularly in radiotherapy, accurate dosimetry ensures effective treatment with minimal impact on healthy tissues. In industrial radiography, high-precision dosimetry guarantees compliance with safety standards, reducing the risk of excessive exposure to the radiation for workers. Within the framework of this international project, involving the Physikalisch-Technische Bundesanstalt (PTB) and the Central Office of Measures (GUM), new calibration protocols for various types of radiation are being developed, traceability chains to ensure measurement accuracy are being established, and best practices are being shared among participants. To achieve these objectives, preliminary comparisons were conducted among NMIs, with two Institutes acting as reference laboratories. This approach allowed the participants to compare their results with control data and make all necessary adjustments. Such collaboration has fostered knowledge exchange and stimulated the development of new dosimetry techniques, which, in the long term, will enhance the precision and reliability of measurements. The NSC “Institute of Metrology” participated in the project as Ukraine’s leading institution in the field of ionizing radiation. The results of this collaboration are presented in the paper, specifically focusing on comparisons of ionizing radiation using the 137Cs and 60Co sources. Additionally, within the framework of the project, the comparisons of X-ray beams with radiation qualities N-40, N-100, and N-200 were conducted.

Automated Measurement of Effective Radiation Dose by 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography.

Calculating the radiation dose from CT in 18F-PET/CT examinations poses a significant challenge. The objective of this study is to develop a deep learning-based automated program that standardizes the measurement of radiation doses. The torso CT was segmented into six distinct regions using TotalSegmentator. An automated program was employed to extract the necessary information and calculate the effective dose (ED) of PET/CT. The accuracy of our automated program was verified by comparing the EDs calculated by the program with those determined by a nuclear medicine physician (n = 30). Additionally, we compared the EDs obtained from an older PET/CT scanner with those from a newer PET/CT scanner (n = 42). The CT ED calculated by the automated program was not significantly different from that calculated by the nuclear medicine physician (3.67 ± 0.61 mSv and 3.62 ± 0.60 mSv, respectively, p = 0.7623). Similarly, the total ED showed no significant difference between the two calculation methods (8.10 ± 1.40 mSv and 8.05 ± 1.39 mSv, respectively, p = 0.8957). A very strong correlation was observed in both the CT ED and total ED between the two measurements (r2 = 0.9981 and 0.9996, respectively). The automated program showed excellent repeatability and reproducibility. When comparing the older and newer PET/CT scanners, the PET ED was significantly lower in the newer scanner than in the older scanner (4.39 ± 0.91 mSv and 6.00 ± 1.17 mSv, respectively, p < 0.0001). Consequently, the total ED was significantly lower in the newer scanner than in the older scanner (8.22 ± 1.53 mSv and 9.65 ± 1.34 mSv, respectively, p < 0.0001). We successfully developed an automated program for calculating the ED of torso 18F-PET/CT. By integrating a deep learning model, the program effectively eliminated inter-operator variability.

Investigation of organs dosimetry precision using ATOM phantom and optically stimulated luminescence detectors in computed tomography

The primary objective of this study was to compare organ doses measured using optically stimulated luminescent dosimeters (OSLDs) with those estimated by the CT-EXPO software for common CT protocols. An anthropomorphic ATOM phantom was employed to measure organ doses across head, chest, and abdominal CT scans performed on a Hitachi Supria 16-slice CT scanner. These OSLD measurements were then compared to the estimates provided by the widely used CT-EXPO software. Organ doses were assessed using OSLDs placed in an adult anthropomorphic phantom, with calibration performed through a comprehensive process involving multiple tube potentials and sensitivity corrections. Results from three CT acquisitions per protocol were compared to estimates provided by CT-EXPO software. Findings reveal significant discrepancies between measured and estimated organ doses, with p-values consistently below 0.05 across all organs. For head CT, measured eye lens doses averaged 33.51 mGy, 6.0% lower than the estimated 35.65 mGy. In chest CT, the thyroid dose was 9.82 mGy, 13.5% higher than the estimated 8.65 mGy. For abdominal CT, the liver dose measured 12.11 mGy, 9.6% higher than the estimated 11.05 mGy. Measured doses for the rest of organs were generally lower than those predicted by CT-EXPO, showing some limitations in current estimation models and the importance of precise dosimetry. This study highlights the potential of OSLD measurements as a complementary method for organ dose assessment in CT imaging, emphasizing the need for more accurate organ dose measurement to optimize patient care.

Efficacy and safety of switching to insulin glargine 300 U/mL in people with type 2 diabetes uncontrolled on basal insulin in China: A post hoc subpopulation analysis of the INITIATION study.

To evaluate the efficacy and safety of insulin glargine 300 U/mL (Gla-300) in people with uncontrolled type 2 diabetes (T2D) switching from another basal insulin (BI). INITIATION was an interventional, single-arm, phase IV study conducted in China. In this post hoc subpopulation analysis, the efficacy and safety of switching to Gla-300 was investigated in individuals with uncontrolled T2D (HbA1c 7.5%-11.0% [58-97 mmol/mol]) with previous BI. The primary endpoint was HbA1c change at week 24. Other measures of glycaemia, hypoglycaemia, insulin dose and weight change were assessed. Three hundred and two participants switched to Gla-300 from another BI, including 232 from insulin glargine 100 U/mL (Gla-100) and 55 from insulin degludec (IDeg). At week 24, the mean ± standard error (SE) HbA1c change from baseline was -0.87% ± 0.06% (-9.5 ± 0.7 mmol/mol; p <0.001). Significant reductions in fasting plasma glucose (least-squares mean [LSM] change -1.13 mmol/L) and fasting self-measured blood glucose (LSM change -1.36 mmol/L) were also observed (both p <0.001). The mean daily BI dose increased from 18.86 U (0.27 U/kg) at baseline to 28.83 U (0.41 U/kg) at week 24. During the 24-week treatment period, the incidence of any hypoglycaemia was 43.8% for all hypoglycaemia and 15.1% for nocturnal hypoglycaemia; the incidence of severe hypoglycaemia was low (0.7%). Minimal body weight change was documented. Gla-300 improved glycaemic control with a relatively low hypoglycaemia risk and minimal weight gain in Chinese people with T2D uncontrolled on previous BI.

Correction method for ionization chamber dosimetry in flattening filter free radiotherapy based on Monte Carlo simulation.

The clinical use of flattening filter free (FFF) radiotherapy has significantly increased in recent years due to its effective enhancement of dose rates and reduction of scatter dose. A proposal has been made to adjust the incident electron angle of the accelerator to expand the application of FFF beams in areas such as large planning target volumes (PTVs). However, the inherent softening characteristics and non-uniformity of lateral dose distribution in FFF beams inevitably lead to increased dosimetry errors, especially for ionization chambers widely used in clinical practice, which may result in serious accidents during FFF radiotherapy. This study constructs a comprehensive Monte Carlo model that encompasses not only conventional FFF beams but also incorporates FFF beams with varying incident electron angles, to investigate dosimetry errors and correction methods in FFF radiotherapy. We have innovatively introduced a FFF output correction factor ( ) to address dosimetry errors in various ionization chambers under different incident electron angle conditions in FFF beams. The primary variations in were analytically determined to result from changes in and the perturbation correction terms of the ionization chamber. Ionization chambers with smaller sensitive volumes typically exhibit reduced dosimetry errors. Our findings indicate that for ionization chambers with sensitive volumes ranging from 0.016 to 0.125cm3, the dosimetry error under various FFF beam conditions consistently remains below 1.15%. This study provides crucial guidance for selecting appropriate ionization chambers in FFF radiotherapy. A correlation was established between the absorbed dose to water in beams with a flattening filter (WFF) and those without (FFF), defined by the FFF output factor ( ). Using the proposed Monte Carlo model, the can be derived and applied to theoretically calculate the absorbed dose to water in FFF beams at varying incident electron angles, with a relative standard uncertainty of 0.2. This study provides a valuable reference for clinical dose measurements and crucial support for establishing dose calibration standards in FFF radiotherapy.

Design of Moderator Assemblies for Fast, Epithermal, or Thermal Neutron–Dominated n-γ Mixed Fields Using a D-D Neutron Source

The treatment field of boron neutron capture therapy (BNCT) is a n-γ mixed field. In the Osaka University BNCT project, a material-filtered radio-photoluminescence glass dosimeter (RPLGD) was proposed for the simultaneous measurement of neutron and gamma-ray doses. In this study, to validate the material-filtered RPLGD, various types of n-γ mixed fields are designed by irradiating different moderator assemblies with a D-D neutron source at the OKTAVIAN facility, Osaka University, Japan. The n-γ mixed fields are classified into fast neutron–, epithermal neutron–, or thermal neutron–dominated fields and a gamma-ray-only field with the specific characteristics as follows: (1) the dose ratios of gamma ray to neutron are 1.0% to 977.0% for the fast neutron–dominated field, 5.0% to 921.1% for the epithermal neutron–dominated field, 0.7% to 946.3% for the thermal neutron–dominated field, and 11880.6% for the gamma-ray-only field; (2) the proportions of fast, epithermal, and thermal neutron doses to total neutron dose are 98.4% to 100.0% for the fast neutron–dominated field, 74.0% to 85.4% for the epithermal neutron–dominated field, and 90.1% to 90.8% for the thermal neutron–dominated field, respectively; and (3) the maximum gamma-ray energy is up to 12 MeV.

Investigating LETd optimization strategies in carbon ion radiotherapy for pancreatic cancer: a dosimetric study using an anthropomorphic phantom.

Clinical carbon ion beams offer the potential to overcome hypoxia-induced radioresistance in pancreatic tumors, due to their high dose-averaged Linear Energy Transfer (LETd), as previous studies have linked a minimum LETd within the tumor to improved local control. Current clinical practices at the Heidelberg Ion-Beam Therapy Center (HIT), which use two posterior beams, do not fully exploit the LETd advantage of carbon ions, as the high LETd is primarily focused on the beams' distal edges. Different LETd-boosting strategies, such as Spot-scanning Hadron Arc (SHArc), could enhance LETd distribution by concentrating high-LETd values in potential hypoxic tumor cores while sparing organs at risk. This study aims to investigate and verify different LETd-boosting strategies using an anthropomorphic pancreas phantom. Various LETd-boosting strategies were investigated for a cylindrical and a pancreas-shaped target in an anthropomorphic pancreas phantom. Treatment plans were optimized using single field optimization (SFO) or multi field optimization (MFO), with objective functions based on either physical dose (Phys), relative biological effectiveness(RBE)-weighted dose, or a combination of RBE and LETd-based objectives (LETopt). The LETd-boosting planning strategies were optimized with the goal of increasing the minimum LETd in the tumor without compromising its homogeneous dose coverage. Beam configurations investigated included the two-beam in-house clinical standard (2-SFOPhys, 2-SFORBE and 2-MFORBE-LETopt), a three-beam configuration (3-MFORBE and 3-MFORBE-LETopt) and SHArc (SHArcPhys, SHArcRBE and SHArcRBE-LETopt) using step-and-shoot delivery. The different plans were verified using an anthropomorphic pancreas phantom at HIT and compared to treatment planning system (TPS) predictions. All investigated LETd-boosting strategies altered the LETd distribution while meeting optimization goals and constraints, resulting in varying degrees of LETd enhancement. For the cylindrical volume, the SHArc plan resulted in the highest LETd concentration in the tumor core, with the minimum LETd in the GTV scaling up to 91keV/µm. For the pancreas-shaped volume, however, the 3-MFORBE-LETopt achieved a higher minimum LETd in the GTV than SHArcRBE (75.6 and 62.3keV/µm, respectively). When combining SHArc with LETd optimization, a minimum LETd of 76.3keV/µm was achieved, suggesting a potential benefit from this combined approach. Most dosimetric verifications showed dose deviations to the TPS within a 5% range, for both beam-per-beam and total dose. LETd-optimized and SHArc plans exhibited slightly higher mean dose deviations (2.0%-4.6%) compared to the standard RBE-based plans (<1.5%). This study demonstrated the feasibility of enhancing LETd in pancreatic tumors using carbon ion arc delivery coupled with LETd optimization. The possibility of delivering these plans was verified through irradiation of an anthropomorphic pancreas phantom, which showed agreement between dose measurements and predictions.

Measurement Of Radiation Dose Due To Indoor 222Rn And 220Rn Concentration In Some Selected Dwellings Of Thirthahalli Taluk

Measurement Of Radiation Dose Due To Indoor 222Rn And 220Rn Concentration In Some Selected Dwellings Of Thirthahalli Taluk

Dosimetric Evaluation of Different Algorithms on Heterogeneous Slab Phantom Using CMS XiO and MONACO Treatment Planning System for 4MV, 6MV and 15MV Beam Energy: An Institutional Study.

To study the dosimetric behavior of dose computational algorithms in inhomogeneous medium using CMS XiO and MONACO treatment planning system (TPS) for 4 megavoltage (MV), 6 MV and 15 MV photon beam energies. Styrofoam blocks of thickness 1.90 cm, 3.8 cm and 5.70 cm was used to introduce inhomogeneity in a slab phantom. Wipro GE computed tomography (CT) scanner was used to scan the phantom. Doses were computed on the central axis of the beam using convolution (C), superposition (S), fast superposition (FS), collapsed cone convolution (CCC) and monte carlo (MC) algorithms for field geometries of 5x5 cm2 and 10x10 cm2 for above said photon beam energies, respectively. An Ion chamber (IC) of 0.6 cc volume was used for the dose measurements. The deviation between measured and TPS computed doses were recorded. The PDD (Percentage depth dose) data obtained from the TPS (calculated data) and LINAC (measured data) was used for comparison based on different algorithms in order to calculate the percentage of maximum deviation (PMD). The PMD in MC algorithm were calculated for field sizes of 5x5 cm2 and 10x10 cm2 are found to be in ranging from 0.73% to -4.49% for 4MV, 1.62% to -2.42% for 6MV and 4.53% to -1.47% for 15 MV for 1.90 cm air gap, 2.21% to -3.75% for 4MV, 3.87% to -2.88% for 6 MV and 4.87% to -3.46% for 15 MV for 3.80 cm air gap, 2.77% to -4.66% for 4MV, 3.87% to -2.86% for 6 MV and 5.66% to -4.92% for 15 MV for 5.70cm air gap which is less as compared to CCC, C, FS, and S algorithms. The comparison of C, S, FS, CCC and MC algorithms demonstrated that MC having better agreement with IC measurements. In conclusion, MC is a superior option for dose computation, particularly in the presence of low-density heterogeneities.

Characterization of natural soda ash for dosimetry using thermoluminescence technique

Soda ash, due to its various use for industrial applications, is a phosphor likely to be found in the vicinities of radiation facilities where retrospective dosimetry may be required in the unlikely events of radiation accidents/incidents. The ash is therefore a potential material for retrospective dosimetry using luminescence techniques. In this report, the thermoluminescence characteristics of soda ash from Suan pan, Botswana are presented. The thermoluminescence glow curve of the soda ash consists three peaks near 79, 175 and 329 oC with a shoulder around 221oC. The peak intensities of the peaks and the whole glow curve integrated intensity are linear with dose. Tm-Tstop analysis reveals soda ash contains four peaks near 82, 211, 235 and 335 oC. The four peaks are affected by thermal quenching with activation energy of thermal quenching 0.64 eV, 0.29 eV, 0.66 eV and 0.29 eV respectively. The intensities of the peaks decrease with optical stimulation. The minimum dose the phosphor can measure is evaluated to be 0.34 Gy. The thermoluminescence from soda ash is suitable for dosimetry, especially for high dose measurement. The peak near 335oC with mean lifetime greater than 250 years is the most suitable for dosimetry. The phosphor may be able to produce phototransfer thermoluminescence.

Enhancing low radio-dosage thyroid imaging using deep learning and Monte Carlo-based absorbed dose measurement in nuclear medicine

The acquisition of improved quality via the administration of low radioactivity is an important challenge in the field of nuclear medicine. Thus, we evaluated the image quality generated under low radioactivity using deep-learning algorithms. In addition, internal dosimetry for various organs was measured based on Monte Carlo simulation. The dataset comprised 500 slices of thyroid nuclear medicine images acquired at 370 MBq as high radioactivity and 18.5 MBq as low radioactivity. The residual neural network (ResNet) with 16 residual blocks and a U-Net model were used with various hyperparameters for learning. In addition, we measured the internal dosimetry in peripheral organs based on a Monte Carlo simulation. The peak signal-to-noise ratio (PSNR) results were 18.24 for the ResNet model and 18.85 for the U-Net model on average. The structural similarity index measurement (SSIM) results were also 0.995 and 0.994 for the ResNet and U-Net models, respectively. The average absorbed dose for radionuclides with 37 MBq was 3.98 times higher than that of the radionuclide with 18.5 MBq. In conclusion, it is possible to make a diagnosis based on the administration of low radioactivity when scanning thyroid nuclear medicine images.

Clinical use of Gafchromic EBT4 film for in vivo dosimetry for total body irradiation.

In vivo dosimetry is a common requirement to validate dose accuracy/uniformity in total body irradiation (TBI). Several detectors can be used for in vivo dosimetry, including thermoluminescent dosimeters (TLDs), diodes, ion chambers, optically stimulated luminescent dosimeters (OSLDs), and film. TLDs are well established for use in vivo but required expertise and clinical system availability may make them impractical for multifractionated TBI. OSLDs offer quick readout, but recalls have restricted their use. The purpose of this work was to validate the newly available Gafchromic EBT4 film for TBI in vivo dosimetry. Film calibration curves were created under standard conditions (6MV/15MV, 1.5/3.0cm depth, 100cm source-to-surface distance (SSD), 10 × 10 cm2 field), and films were scanned at several time points (0.5-24h) to determine the shortest development time that yielded accurate dose measurements. 4 × 4 cm2 films were placed under 1.5cm thick bolus on the anterior and posterior sides of a solid water phantom to measure entrance and exit dose under TBI conditions (∼600cm SSD, 39.5 × 39.5 cm2 field, 6 MV/15 MV). These measurements were compared to ion chamber and diode readings for validation. Film measurements were also compared to OSLD measurements for three TBI patients. The shortest development time that resulted in accurate dosimetry and allowed for adequate physician review time was 4h (±4% dose accuracy). Film entrance and exit dose measurements were within±3.8% of ion chamber and diode readings for 6MV and 15MV beams. Patient film measurements were within ∼±5% for the majority of anatomical measurement locations; however, film and OSLD readings for some anatomic locations deviated by>10%. These results indicate that EBT4 film can be utilized for accurate in vivo dosimetry for TBI patients and shows good agreement with diode and ion chamber measurements. Further investigation into film and OSLD differences was not possible due to OSLD recalls.

Bilosome as a potential carrier for improving poor oral drug bioavailability

Solid oral dosage forms are widely used in the management of chronic diseases. They are preferred due to their ease of administration, affordability, stability, and accuracy in dose measurement. However, there are challenges with oral delivery due to a number of physiological and metabolic barriers that may impair therapeutic efficacy. Difficulties such as limited water solubility and biological membrane translocation can have a major impact on how well a drug is absorbed. The complexity of developing an oral dosage form is further compounded by considerations such as the drug stability, the impact of gastrointestinal pH, and interactions with metabolic enzymes and biological efflux mechanisms. One of the most important pharmacokinetic indicators of a drug's ability to achieve systemic availability after absorption is bioavailability. It is controlled by how well the drug dissolves and how well it passes through physiological barriers. The purpose of bilosomes, vesicular carriers composed of bile salts and nonionic surfactants, is to improve the administration of vaccinations and drugs. The gastrointestinal tract (GIT) can efficiently transport a range of pharmacological drugs, such as those with antibacterial, antifungal, and antiparasitic capabilities, as well as vaccines and bioactive molecules that target infectious organisms, due to their stability and malleability. For oral medications, bilosomal formulations exhibit higher delivery efficacy due to the complex and hostile environment of the GIT. This research evaluates the potential of bilosomes as a delivery system and highlights how they could be used to administer medications for diseases and viruses that affect the GIT.

Beam quality correction factors for dose measurements around 192Ir brachytherapy sources.

To provide beam quality correction factors ( ) for detectors used in 192Ir brachytherapy dosimetry measurements. Ten detectors were studied, including the PTW 30013 and Exrading12 Farmer large cavity chambers, seven medium (0.1-0.3cm3) and small(<0.1cm3) cavity chambers, and a synthetic microdiamond detector. The kQ,Qo correction factors were calculated at distances from 1 to 10cm away from an 192Ir source, using the EGSnrc Monte Carlo (MC) code. All detectors were calibrated in a 60Co 10×10cm2 reference field provided by standard calibration laboratories. The impact of the central electrode, stem and wall on the detectors' responses in 192Ir photon energies was investigated. An experimental procedure was additionally applied for dose measurements around a microSelectron-v2 192Ir high dose rate (HDR) brachytherapy source using a motorized water phantom. Farmer chambers underestimated the dose near the source due to signal volume averaging effects, resulting in kQ,Qo values ranging from 1.177 and 1.317 at 1cm, decreasing with distance to between 0.980 and 1.005 at 10cm. Small cavity volume detectors should be used close to the source. The kQ,Qo for the studied small and medium cavity volume detectors were found to be close to unity (within 1.3%), showing also a small dependence on source-to-detector distance, except for ion chambers containing high-Z materials in their construction. The presence of high-Z materials caused an overresponse in these detectors, resulting in kQ,Qo values ranging from 0.950 at 1cm to 0.729 at 10cm away from the source. A dose rate constant of (1.114±0.023)cGyh-1U-1 was found in agreement with the literature (within 0.5%). kQ,Qo values were calculated for dose measurements around 192Ir brachytherapy sources. Farmer chambers should be preferred for measurements at increased distances, whereas small or medium cavity volume detectors, not containing high-Z materials, should be used close to the source.