IR Source Research Articles

A new insight on the effects of Schiff Base Iron (III) complexes in breast cancer cells for clinical radiotherapy

PurposeBreast cancer is a significant global health concern, and researchers strive to enhance radiotherapy outcomes while minimizing the side effects. Schiff Base Iron (III) Complexes are one of the prospective elements that can be used as radiosensitizer or radioprotective agents in cancer radiotherapy. This study investigates the potential effects of Schiff base (ligand 2; L2) with Fe(III) in MCF-7 breast cancer cells under clinical radiotherapy treatment. MethodsThe effects of the Schiff Base Iron (III) Complexes were measured using clonogenic assay with MCF-7 breast cancer cells. The cells were irradiated with megavoltage 6 MV photon, 6 MeV electron and high dose rate (HDR) brachytherapy with 192Ir source at different doses. Intercellular localization of Fe(III)-L2 complexes and antioxidant activities were also investigated. ResultsThe Fe(III)-L2 complexes were observed to be internalized by cellular nuclei without any effects on the cells. Interestingly, the Fe(III)-L2 complexes indicate radioprotective effects which provide intriguing insight towards application of metal ions complexes as radioprotector in cancer radiotherapy. The Fe(III)-L2 complexes also exhibit scavenging activities of free radical which further proved the antioxidative properties and radioprotective effects. ConclusionThe Fe(III)-L2 complexes show the radioprotective effects and antioxidant properties in MCF-7 cells, particularly for HDR brachytherapy. The findings suggest potential applications of the Fe(III)-L2 complexes as radioprotector agents in clinical radiotherapy.

Study on Characteristics of Epoxy Resin-Based Plastic Scintillators for Detectors with Simulation Using Monte Carlo Code

Abstract To determine the presence of radioactive materials emitting gamma rays entering or exiting nuclear facilities, ports, airports, international borders, or other strategic locations, radiation portal monitors (RPMs) capable of detecting such gamma radiation need to be installed in these places. National Research and Innovation Agency of Indonesia (BRIN) is currently developing RPMs with detector components made of plastic scintillator based on epoxy resin and augmented with aromatic fluorescent materials to produce visible light, which is the working range of the photomultiplier tube (PMT) or silicon photomultiplier (SiPM). This research aims to study the characteristics of the gamma photon radiation energy spectrum from Co-60, Cs-137, and Ir-192 sources in an epoxy resin plastic scintillator and study the absorbed dose of the scintillator to gamma photon radiation energy from Co-60, Cs-137, and Ir-192 sources as a function of source distance and incidence angle of gamma rays with simulations using the MCNPX code. The scintillator is modeled in the form of a cylinder with a diameter of 5 cm and a height of 5 cm. To simulate the gamma photon radiation energy spectrum in the scintillator, the F4 tally was used and to simulate the scintillator absorbed dose, the F6 tally was used. This simulation used gamma sources of Co-60, Cs-137, and Ir-192 of 1 mCi each. These characteristics of the epoxy resin plastic scintillator have been successfully simulated. Data on the characteristics of epoxy resin plastic scintillators is important to know and study as supporting data in making plastic detectors as part of the manufacture and development of RPM.

Monte Carlo simulated correction factors for high dose rate brachytherapy postal dosimetry audit methodology

Background and PurposeFull-scatter conditions in water are impractical for postal dosimetry audits in brachytherapy. This work presents a method to obtain correction factors that account for deviations from full-scatter water-equivalent conditions for a small plastic phantom Material and MethodsA 16 × 8 × 3 cm phantom (PMMA) with a radiophotoluminescent dosimeter (RPLD) at the centre and two catheters on either side was simulated using Monte Carlo (MC) to calculate correction factors accounting for the lack of scatter, non-water equivalence of the RPLD and phantom, source model and backscatter for HDR 60Co and 192Ir sources. ResultsThe correction factors for non-water equivalence, lack of full scatter, and the use of PMMA were 1.062 ± 0.013, 1.059 ± 0.008 and 0.993 ± 0.009 for 192Ir and 1.129 ± 0.005, 1.009 ± 0.005 and 1.005 ± 0.005 for 60Co respectively. Water-equivalent backscatter thickness of 5 cm was found to be adequate and increasing thickness of backscatter did not have an influence on the RPLD dose. The mean photon energy in the RPLD for four HDR 192Ir sources was 279 ± 2 keV in full scatter conditions and 295 ± 1 keV in the audit conditions. For 60Co source the corresponding mean energies were 989 ± 1 keV and 1022 ± 1 keV respectively. ConclusionsCorrection factors were obtained through the MC simulations for conditions deviating from TG-43, including the amount of back scatter, and the optimum audit set up. Additionally, the influence of different source models on the correction factors was negligible and demonstrates their generic applicability.

Development and international multicentre pilot testing of a postal dosimetry audit methodology for high dose rate brachytherapy

Background and PurposeDosimetry audits are essential for reducing errors in brachytherapy. A postal dosimetry audit methodology was developed and tested in an international multicentre pilot, to assess the accuracy of the Reference Air Kerma Rate of 192Ir and 60Co brachytherapy sources Materials and MethodsA compact phantom made of polymethyl methacrylate was developed to accommodate two catheters, a radiophotoluminescence dosimeter (RPLD) for dose measurements and a Gafchromic (RTQA2) film strip for source position verification. Deviations of the audit setup from TG-43 conditions were quantified experimentally and compared to previous Monte Carlo (MC) simulations. A measurement uncertainty budget was estimated for the RPLD analysis. The methodology was tested in an international pilot study consisting of 59 dosimeter sets among 48 centres from 11 countries. ResultsThe experimental correction factors showed good agreement with previous MC simulations, and the total correction factor accounting for non-water equivalence, lack of scatter and beam quality was found to be 1.029 ± 0.009 for 192Ir and 1.059 ± 0.007 for 60Co sources, to be employed in audit measurement. The total uncertainty budget was estimated to be 2.24 % (k = 1). In the multicentre study, the ratio between measured and reported user dose ranged from 0.968 to 1.049, with all irradiated dosimeter sets within ± 5 %, and 54 out of 59 within ± 3 %. ConclusionsThe methodology was tested in an international multicentre pilot study and has shown good performance validating the uncertainty budget.

Multi-Junction Solar Module and Supercapacitor Self-Powering Miniaturized Environmental Wireless Sensor Nodes

A novel prototype based on the combination of a multi-junction, high-efficiency photovoltaic (PV) module and a supercapacitor (SC) able to self-power a wireless sensor node (WSN) for outdoor air quality monitoring has been developed and tested. A PV module with about an 8 cm2 active area made of eight GaAs-based triple-junction solar cells with a nominal 29% efficiency was assembled and characterized under terrestrial clear-sky conditions. Energy is stored in a 4000 F/4.2 V supercapacitor with high energy capacity and a virtually infinite lifetime (104 cycles). The node power consumption was tailored to the typical power consumption of miniaturized, low-consumption NDIR CO2 sensors relying on an LED as the IR source. The charge/discharge cycles of the supercapacitor connected to the triple-junction PV module were measured under illumination with a Sun Simulator device at selected radiation intensities and different node duty cycles. Tests of the miniaturized prototype in different illumination conditions outdoors were carried out. A model was developed from the test outcomes to predict the maximum number of sensor samplings and data transmissions tolerated by the node, thus optimizing the WSN operating conditions to ensure its self-powering for years of outdoor deployment. The results show the self-powering ability of the WSN node over different insolation periods throughout the year, demonstrating its operation for a virtually unlimited lifetime without the need for battery substitution.

Monte Carlo dosimetry study of newly designed shielded applicators for intensity modulated brachytherapy of cervical and vaginal cancers

IntroductionThe utilization of metal shields in intensity-modulated brachytherapy (IMBT) enables the modulation of the dose, resulting in improved conformance to the tumor while simultaneously reducing the doses to organs at risk (OARs). Utilizing higher-energy sources like 60Co in IMBT for cervical and vaginal cancers has consistently posed challenges. This study evaluates the dosimetric aspects of modified applicators designed for IMBT using 60Co and 192Ir sources.Materials and MethodsGATE, a Geant4-based simulation code, was utilized to model and simulate four distinct applicators. The clinical applicators were redesigned to place the structure of the source tube and the shield while keeping the general characteristics unchanged. These shields were evaluated by calculating transmission factors (TFs) and the dose homogeneities were also determined.ResultTransmission factors for the IMBT technique in redesigned intrauterine applicators and tungsten shields for iridium and cobalt sources were at least 12.8 and 65.4%, and these values were obtained for the intravaginal applicator at 0.2 and 7.0%, respectively. The dose homogeneities for all combinations of radionuclide-shield were within a 15% range of the non-IMBT applicators.ConclusionThis study has quantitatively evaluated the dosimetric effect of tungsten shields in the IMBT technique for cervical and vaginal cancer using cobalt sources. 192Ir compared to 60Co resulted in higher effectiveness for the designed intrauterine and intravaginal shields. while implementing tungsten shields in the redesigned applicators against the 60Co source may not offer complete protection, it does show promising results in reducing the dose to organs at risk.

Self-illuminated third-harmonic image upconversion.

We demonstrate third-harmonic upconversion imaging to visualize real time infrared images in the visible with standard CCD or CMOS silicon-based cameras operating at room temperature. Different from the usual sum-frequency mixing image upconversion, our third-harmonic image upconversion approach does not require an auxiliary IR source to illuminate a target. The upconversion system uses a passively Q-switched Nd3+:YVO4 laser operating at 1342 nm with two intracavity KTP crystals, obtaining a 447 nm upconverted image by a cascaded process where an upconverted image at 671 nm is also obtained as an intermediate step.

HDR brachytherapy afterloader quality assurance optimization using monolithic silicon strip detectors.

There currently exists no widespread high dose-rate (HDR) brachytherapy afterloader quality assurance (QA) tool for simultaneously assessing the afterloader's positional, temporal, transit velocity and air kerma strength accuracy. The purpose of this study was to develop a precise and rigorous technique for performing daily QA of HDR brachytherapy afterloaders, incorporating QA of: dwell position accuracy, dwell time accuracy, transit velocity consistency and relative air kerma strength (AKS) of an Ir-192 source. A Sharp ProGuide 240mm catheter (Elekta Brachytherapy, Veenendaal, The Netherlands) was fixed 5mm above a 256 channel epitaxial diode array 'dose magnifying glass' (DMG256) (Centre for Medical and Radiation Physics, University of Wollongong). Three dwell positions, each of 5.0s dwell times, were spaced 13.0mm apart along the array with the Flexitron HDR afterloader (Elekta Brachytherapy, Veenendaal, The Netherlands). The DMG256 was connected to a data acquisition system (DAQ) and a computer via USB2.0 link for live readout and post-processing. The outputted data files were analyzed using a Python script to provide positional and temporal localization of the Ir-192 source by tracking the centroid of the detected response. Measurements were repeated on a weekly basis, for a period of 5weeks to determine the consistency of the measured parameters over an extended period. Using the DMG256 for relative AKS measurements resulted in measured values within 0.6%-3.0% of the expected activity over a 7-week period. The sub-millisecond temporal accuracy of the device allowed for measurements of the transit velocity with an average of (10.88±1.01) cm/s for 13mm steps. The dwell position localization for 1, 2, 3, 5, and 10mm steps had an accuracy between 0.1 and 0.3mm (3σ), with a fixed temporal accuracy of 10ms. The DMG256 silicon strip detector allows for clinics to perform rigorous daily QA of HDR afterloader dwell position and dwell time accuracy with greater precision than the current standard methodology using closed circuit television and a stopwatch. Additionally, DMG256 unlocks the ability to perform measurements of transit velocity/time and relative AKS, which are not possible using current standard techniques.

Calibration system correction factor for measuring the reference air kerma rate (RAKR) applied to high dose rate 192Ir sources (HDR)

The aim of this study was to use computer simulation to analyze the impact of the aluminum fixing support on the Reference Air Kerma (RAK), a physical quantity obtained in a calibration system that was experimentally developed in the Laboratory of Radiological Sciences of the University of the State of Rio de Janeiro (LCR-UERJ). Correction factors due to scattered radiation and the geometry of the 192Ir sources were also sought to be determined. The computational simulation was validated by comparing some parameters of the experimental results with the computational results. These parameters were: verification of the inverse square law of distance, determination of (RAKR), analysis of the source spectrum with and without encapsulation, and the sensitivity curve of the Sourcecheck 4PI ionization chamber response, as a function of the distance from the source along the axial axis, using the microSelectron-v2 (mSv2) and GammaMedplus (GMp) sources. Kerma was determined by activity in the Reference air, with calculated values of 1.725 × 10−3 U. Bq−1 and 1.710 × 10−3 U. Bq−1 for the ionization chamber NE 2571 and TN 30001, respectively. The expanded uncertainty for these values was 0.932% and 0.919%, respectively, for a coverage factor (k = 2). The correction factor due to the influence of the aluminum fixing support for measurements at 1 cm and 10 cm from the source was 0.978 and 0.969, respectively. The geometric correction factor of the sources was ksg = 1.005 with an expanded uncertainty of 0.7% for a coverage factor (k = 2). This value has a difference of approximately 0.2% compared to the experimental values.

Application of unmanned aerial vehicles in emergency radiation monitoring

The paper is based on experiments within a project to prepare tutorial tasks on a training centre for testing radiation detectors fixed on unmanned aerial vehicles (UAVs) and in unmanned ground vehicles. The paper reports on a small UAV with NaI(Tl) 2“ x 2” detector for radiation monitoring in an emergency event and for radioactive source chasing and detection. The paper is focused on some special cases with the possibility to determine local air kerma rates and the activities of point sources. The detector was calibrated for air kerma rates from 5 nGy h−1 to 20 μGy h−1. The verified model of the NaI(Tl) 2″ x 2″ detector including the electronic module assembled on a UAV was designed in a Monte Carlo simulation. The model was used for calculating the air kerma rates at various altitudes above the ground both for a natural background and for selected point sources. The response functions for 137Cs, 131I, 192Ir, 60Co and 99Mo point sources were calculated by the Monte Carlo simulation to estimate their activities. Experiments were carried out with an NaI(Tl) 2“ x 2” detector fixed on a Robodrone UAV and flying over 60Co and 137Cs point sources over the airfield area and the local air kerma rates and the activities of the point sources were calculated with the AGAMA post-processing program. In addition, the response functions for 137Cs distributed uniformly on the surface were calculated by Monte Carlo simulation for future emergency purposes. The detection limits of selected man-made nuclides (point sources) were calculated.

New Herbig–Haro objects associated with embedded sources

ABSTRACT We continue to present the results of the Byurakan Narrow Band Imaging Survey (BNBIS). The main goal of this survey is to search for Herbig–Haro (HH) objects and jets in Galactic dark clouds. In this work we present the results of the search in the vicinity of infrared sources that are bright in the WISE survey and embedded in the dark clouds. The survey is performed with the 1-m Schmidt telescope of Byurakan Observatory, lately equipped with a new CCD detector, which allows to obtain one square degree images of the sky in various filters. Narrow-band filters were used to obtain H α and [S ii] images, and a medium-width filter was used for the continuum imaging. New HH flows and knots were found near six embedded IR sources, which constitutes a significant proportion of the objects observed. At least two of the newly found HH flows (HH 1226 and HH 1227) lie in isolated dark clouds, thus pointing to active star formation in these regions. Other flows are also located in detached and dense globules or filaments. The length of the HH 1228 flow is about 1 pc; it has also a molecular hydrogen counterpart of the same extension. Coordinates, charts, detailed descriptions and distance estimates are provided. The lower limits of bolometric luminosities of the source stars are typical for low-mass young stellar objects.

Assessing Heterogeneity Effects on Points A, B, and Organs at Risk Doses in High-dose-Rate Brachytherapy for Cervical Cancer - A Comparison of 192Ir and 60Co Sources Using Monte Carlo N-Particle 5.

The present article deals with investigating the effects of tissue heterogeneity consideration on the dose distribution of 192Ir and 60Co sources in high-dose-rate brachytherapy (HDR-BT). A Monte Carlo N-Particle 5 (MCNP5) code was developed for the simulation of the dose distribution in homogeneous and heterogeneous phantoms for cervical cancer patients. The phantoms represented water-equivalent and human body-equivalent tissues. Treatment data for a patient undergoing HDR-BT with a 192Ir source were used as a reference for validation, and for 60Co, AAPM Task Group 43 methodology was also applied. The dose values were calculated for both source types in the phantoms. The results showed a good agreement between the calculated dose in the homogeneous phantom and the real patient's treatment data, with a relative difference of less than 5% for both sources. However, when comparing the absorbed doses at critical points such as Point A right, Point A left, Point B right, Point B left, bladder International Commission on Radiation Units and Measurement (ICRU) point, and recto-vaginal ICRU point, the study revealed significant percentage differences (approximately 5.85% to 12.02%) between the homogeneous and heterogeneous setups for both 192Ir and 60Co sources. The analysis of dose-volume histograms (DVH) indicated that organs at risk, notably the rectum and bladder, still received doses within recommended limits. The study concludes that 60Co and 192Ir sources can be effectively used in HDR-BT, provided that careful consideration is given to tissue heterogeneity effects during treatment planning to ensure optimal therapeutic outcomes.

Feasibility study of real-time imaging of an Ir-192 source using compact gamma camera with curved diverging collimator for brachytherapy

Brachytherapy is a treatment method that requires the accurate positioning of a radioactive source to deliver high doses to a tumor while minimizing exposure to surrounding tissues. Herein, we propose a compact gamma camera system based on a diverging collimator for real-time source positioning during brachytherapy. In the process of developing and fabricating such a gamma camera system, Monte Carlo simulations for diverging and pinhole collimators are performed under conditions that are similar to the actual detection environment, with the camera-to-source distance set at 50 cm to verify the feasibility of the gamma camera. Full width at half maximum (FWHM) and signal-to-noise ratio (SNR) values are analyzed based on the horizontal and vertical profiles at each location as the source shifts stepwise from the center to the right and diagonal direction. On average, the diverging collimator had FWHM values of 18 and 13 mm and SNR values of 30 and 31, while the pinhole collimator had FWHM values of 26 and 25 mm and SNR values of 47 and 46 when profiled horizontally and vertically. The diverging collimator has a lower SNR than pinhole collimator but performs better in terms of spatial resolution. Additionally, to test the performance of the manufactured gamma camera, the distance between the camera and the source was set to 100 cm and an experiment was conducted. The experimental results exhibit a trend similar to the simulation. Numerically, the average FWHM value were 39 mm in the vertical direction and 71 mm in the horizontal direction. Additionally, the average SNR values were 27 for the vertical direction and 17 for the horizontal direction. Based on these results, we confirm the possibility of Ir-192 source imaging.

Monte Carlo simulation study of an in vivo four-dimensional tracking system with a diverging collimator for monitoring radiation source (Ir-192) location during brachytherapy: proof of concept and feasibility.

Introduction: The aim of this study was to demonstrate the potential of an in vivo four-dimensional (4D) tracking system to accurately localize the radiation source, Iridium-192 (Ir-192) in high-dose rate brachytherapy. Methods: To achieve time-dependent 3D positioning of the Ir-192 source, we devised a 4D tracking system employing multiple compact detectors. During the system's design phase, we conducted comprehensive optimization and analytical evaluations of the diverging collimator employed for detection purposes. Subsequently, we executed 3D reconstruction and positioning procedures based on the 2D images obtained by six detectors, each equipped with an optimized diverging collimator. All simulations for designing and evaluating the 4D tracking system were performed using the open-source GATE (v9.1) Monte Carlo platform based on the GEANT4 (v10.7) toolkit. In addition, to evaluate the accuracy of the proposed 4D tracking system, we conducted simulations and 3D positioning using a solid phantom and patient data. Finally, the error between the reconstructed position coordinates determined by the tracking system and the original coordinates of the Ir-192 radiation source was analyzed. Results: The parameters for the optimized diverging collimator were a septal thickness of 0.3mm and a collimator height of 30mm. A tracking system comprising 6 compact detectors was designed and implemented utilizing this collimator. Analysis of the accuracy of the proposed Ir-192 source tracking system found that the average of the absolute values of the error between the 3D reconstructed and original positions for the simulation with the solid phantom were 0.440mm for the x coordinate, 0.423mm for the y coordinate, and 0.764mm for the z coordinate, and the average Euclidean distance was 1.146mm. Finally, in a simulation based on data from a patient who underwent brachytherapy, the average Euclidean distance between the original and reconstructed source position was 0.586mm. Discussion: These results indicated that the newly designed in vivo 4D tracking system for monitoring the Ir-192 source during brachytherapy could determine the 3D position of the radiation source in real time during treatment. We conclude that the proposed positioning system has the potential to make brachytherapy more accurate and reliable.

Tracing Magma Migration at Mt. Etna Volcano during 2006–2020, Coupling Remote Sensing of Crater Gas Emissions and Ground Measurement of Soil Gases

The geochemical monitoring of volcanic activity today relies largely on remote sensing, but the combination of this approach together with soil gas monitoring, using the appropriate parameters, is still not widely used. The main purpose of this study was to correlate data from crater gas emissions with flank emissions of soil gases at Mt. Etna volcano from June 2006 to December 2020. Crater SO2 fluxes were measured from fixed stations around the volcano using the DOAS technique and applying a modeled clear-sky spectrum. The SO2/HCl ratio in the crater plume was measured with the OP-FTIR technique from a transportable instrument, using the sun as an IR source. Soil CO2 efflux coupled with the 220Rn/222Rn activity ratio in soil gases (named SGDI) were measured at a fixed monitoring site on the east flank of Etna. All signals acquired were subject both to spectral analysis and to filtering of the periodic signals discovered. All filtered signals revealed changes that were nicely correlated both with other geophysical signals and with volcanic eruptions during the study period. Time lags between parameters were explained in terms of different modes of magma migration and storage inside the volcano before eruptions. A comprehensive dynamic degassing model is presented that allows for a better understanding of magma dynamics in an open-conduit volcano.

Dosimetry of Large Field Valencia applicators for Cobalt-60-based brachytherapy.

Non-melanoma skin cancer is one of the most common types of cancer and one of the main approaches is brachytherapy. For small lesions, the treatment of this cancer with brachytherapy can be done with two commercial applicators, one of these is the Large Field Valencia Applicators (LFVA). The aim of this study is to test the capabilities of the LFVA to use clinically 60Co sources instead of the 192Ir ones. This study was designed for the same dwell positions and weights for both sources. The Penelope Monte Carlo code was used to evaluate dose distribution in a water phantom when a 60Co source is considered. The LFVA design and the optimized dwell weights reported for the case of 192Ir are maintained with the only exception of the dwell weight of the central position, that was increased. 2D dose distributions, field flatness, symmetry and the leakage dose distribution around the applicator were calculated. When comparing the dose distributions of both sources, field flatness and symmetry remain unchanged. The only evident difference is an increase of the penumbra regions for all depths when using the 60Co source. Regarding leakage, the maximum dose within the air volume surrounding the applicator is in the order of 20% of the prescription dose for the 60Co source, but it decreases to less than 5% at about 1cm distance. Flatness and symmetry remains unaltered as compared with 192Ir sources, while an increase in leakage has been observed. This proves the feasibility of using the LFVA in a larger range of clinical applications.

Development of LTCC IR-Emitter and Its Packaging

In this paper, thick film-based IR source is fabricated using multilayer Low Temperature Co-fired Ceramic (LTCC) Technology. The proposed emitter is developed using screen printing of platinum material on LTCC substrates. The highly uniform meander shaped structure is fabricated with the size of 3.5 mm × 3.5 mm. Electrical, optical and thermal characterization of the fabricated device are carried out. Device temperature reaches 600 °C at 6.5 V. Optical characterization of the developed device shows the spectral range in the mid-IR region with power consumption of ∼3 W. In-house indigenised package is developed using glass-metal seal technique for packaging of developed IR source. Different windows viz., quartz, LiF and CaF2 are used for packaging. Developed IR source demonstrate the potential to meet the performance, size and cost requirements for various applications. The developed LTCC based IR source has planar and simple structure with high temperature stable lead-free interconnects.

Design and development of additivemanufactured multi-channel brachytherapy applicators for cancer treatment

Additive manufacturing (AM) is emerging as an effective manufacturing technology that benefits the medical field with its ease of quickly realizing complex designs. Brachytherapy is a process to cure cancer patients through a high dose rate of gamma radiation. This work aimed at AM-based development of multi-channel vaginal and penile brachytherapy applicators for selectively treating cancer cells in a direction sideways to the applicator rather than the uniform radiation dose possible around the conventional applicator used in cancer treatment. An analytical model was proposed to predict the maximum surface temperature on applicators during Ir-192 source radiation. Also, the predicted values of multi-physics-based finite element method simulation were experimentally validated using a thermal imaging camera. Thermal imaging is a non-contact measurement that is found superior to the brachytherapy scale to position radioactive sources inside the applicator. Experimentally examined multi-channel applicator shows dosimetry advantage in effective radiation control and shows promise of curing cancerous cells with minimal effects on normal cells.

Использование явления термостимулированной радиационно- обусловленной люминесценции микрокристаллов морской соли для внутриполостной «ин виво» дозиметрии при брахитерапии рака предстательной железы источником Ir192: оценка потенциала

Aim of the study – use of the phenomenon of thermo stimulated luminescence in natural microcrystals of sea salt (NaCl) in the range of therapeutic doses in order to develop a method for off line intracavitary «in vivo» dosimetry of patients at high dose-rate brachytherapy of prostate cancer with a 192Ir source. Samples of aliquots with natural microcrystals (a fraction with a size of about 100 m) of sea salt were used in the study. Measurements were carried out using a Harshaw 3500 device, which is a thermoluminescent reader. Irradiation of samples to construct the calibration dependences was carried out by a standard 90Sr/90Y source providing the dose rate of 2.99 mGy/s. It was established, that: (1) there is a linear dose dependence of luminescence intensity from studied microcrystals in the range of therapeutic absorbed doses from 1 to 20 Gy with an error in measuring the luminescence intensity of the studied microcrystal samples of less than 5%; (2) it was revealed that fading (decrease in microdosimeter readings over time) does not exceed 5% 5 days after irradiation; (3) clinical testing of «in vivo» dosimetry method using sea salt microcrystals for high dose-rate brachytherapy of prostate cancer shows that the results of measurements of absorbed doses in the organ at risk (rectum) using studied natural NaCl crystals are consistent, within the limits of error, with the results of measurements by synthetic LiF:Mg,Ti crystals (with intracavitary placement in the organ at risk and simultaneous irradiation both assemblies of these microcrystals). It was concluded that the use of the studied sea salt microcrystals is promising for «in vivo» dosimetry in application to 192Ir high dose-rate brachytherapy of prostate cancer.

Effect of model-based dose-calculation algorithms in high dose rate brachytherapy of cervical carcinoma.

Task Group 43 (TG-43) formalism does not consider the tissue and applicator heterogeneities. This study is to compare the effect of model-based dose calculation algorithms, like Advanced Collapsed Cone Engine (ACE), on dose calculation with the TG-43 dose calculation formalism in patients with cervical carcinoma. 20 patients of cervical carcinoma treated with a high dose rate of intracavitary brachytherapy were prospectively studied. The target volume and organs at risk (OARs) were contoured in the Oncentra treatment planning system (Elekta, Veenendaal, The Netherlands). All patients were planned with cobalt-60 (Co-60) and iridium-192 (Ir-192) sources with doses of 21 Gy in 3 fractions. These plans were calculated with TG-43 formalism and a model-based dose calculation algorithm ACE. The dosimetric parameters of TG-43 and ACE-based plans were compared in terms of target coverage and OAR doses. For Co-60-based plans, the percentage differences in the D90 and V100 values for high-risk clinical target volume (HR-CTV) were 0.36 ± 0.43% and 0.17 ± 0.31%, respectively. For the bladder, rectum and sigmoid, the percentage differences for D2cc volumes were -0.50 ± 0.51%, -0.16 ± 0.53% and -0.37 ± 1.21%, respectively. For Ir-192-based plans, the percentage difference in the D90 for HR-CTV was 0.54 ± 0.79%, while V100 was 0.24 ± 0.29%. For the bladder, rectum and sigmoid, the doses to 2cc volume were 0.35 ± 1.06%, 0.99 ± 0.74% and 0.74 ± 1.92%, respectively. No significant differences were found in the dosimetric parameters calculated with ACE and TG-43. The ACE algorithm reduced doses to OARs and targets. However, ACE and TG-43 did not show significant differences in the dosimetric parameters of the target and OARs with both sources.