Miniature X-ray Tube Research Articles

Dose voxel resolution determination for Monte Carlo electron beam simulation in thin targets.

Monte Carlo particle simulation has become the primary tool for designing low-energy miniature x-ray tubes due to the difficulties of physically prototyping these devices and characterizing their radiation fields. Accurate simulation of electronic interactions within their targets is necessary for modelling both photon production and heat transfer. Voxel-averaging can conceal hot spots in the target heat deposition profile that can threaten the integrity of the tube. This research seeks a computationally-efficient method of estimating voxel-averaging error in energy deposition simulations of electron beams penetrating thin targets to inform the appropriate scoring resolution for a desired accuracy level. An analytical model to estimate voxel-averaging along the target depth was developed and compared to results from Geant4 via its wrapper, TOPAS. A 200 keV planar electron beam was simulated to impinge tungsten targets of thicknesses between 1.5- and 12.5- . For each target, the model was used to calculate the energy deposition ratio between voxels of varying sizes centered on the longitudinal midpoint of the target. Model-calculated ratios were compared to simulation outputs to gauge the model's accuracy. Then, the model was used to approximate the error between the point value of electron energy deposition and a voxel-based measurement. The model underestimates error to within 5% for targets less than 7.5- in thickness with increasing error for greater thicknesses. For the 1.5- target, calculations of the point-vs.-voxel energy deposition show an 11% averaging effect between the midpoint and a 1.5- voxel. Energy deposition profiles along the target depth were also calculated in the Monte Carlo for reference. A simple analytical model was developed with reasonable accuracy to guide Monte Carlo users in estimating the appropriate depth-voxel size for thin-target x-ray tube simulations. This methodology can be adapted for other radiological contexts to increase robustness in point-value estimations. This article is protected by copyright. All rights reserved.

A miniature filamentless X-ray tube for the on-board calibration of space-borne X-ray detectors

The on-orbit calibration of the space X-ray detectors is important to obtain the accurate science data. Radioactive isotopes such as 241Am and 55Fe are generally used to implement calibration for space X-ray mission. However, the radioactive source is potential risk for the health safety and also causes a persistent radiation background during X-ray detector operation in space. On-orbit calibration of X-ray detectors has always been a difficult problem for space missions. This paper presents a miniature filamentless X-ray tube (MFXT) with tungsten target which can be used to calibrate X-ray detector on-orbit. At −12 kV high-voltage applied on MFXT, the strong L-series of characteristic X-ray of tungsten target is produced, so the gain and offset parameters of detector can be easily determined by the energy peaks of characteristic X-rays of tungsten. And after about 24 h of cumulative experiment, at least two characteristic ray peaks that can be used for calibration are formed with 5 minutes cumulative time after turning on it again with 5.2E+3 counts/s/sr radiation intensity by MFXT. As of the miniature, low power consumption and high reliability, this MFXT is an alternative to replace the radioactive source for on-orbit detector calibration in space missions.

Characterization of soils around a former chemical plant in Braila, SE Romania, using high performance atomic techniques (EDXRF, AAS, ICP-MS)

This paper presents the problem of soil pollution in the vicinity of a former chemical plant, given that production activity was stopped for more than thirty years ago. The old chemical plant was located in the southern part of Braila town, SE Romania, just a few kilometers from the left bank of the Danube River. Prior to 1990, there was a significant production of industrial chemical goods, such as sulfuric acid, carbon dioxide for synthetic fibers, chlorine gas and hydrochloric acid obtained by electrolysis processes with mercury electrodes and heavy metal catalysts (Cd, Ni, Zn), sodium sulfide and sulphate, etc. For the good development of the experimental program, a number of 10 soil samples were collected from the north, northwest, west, southwest and south of the former chemical plant. The multi-element analysis method used to determine the trace elements in the soil samples was energy-dispersive X-ray fluorescence spectrometry (EDXRF), using a Genius XRF portable spectrometer manufactured by Skyray Instruments Inc., equipped with a large surface Si with a Be window and a 40 kV/100 µA miniature X-ray tube excitation source with Ag target. The spectrometric system has an energy resolution up to 139 eV, and the detection limits of the order of ppm. A total of 21 chemical elements were identified in the target soil samples, such as: K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Hg, Rb, Sr, Y, Zr, Nb, Mo, Sn, Sb, Pb. The compositional analyses of contaminated industrial soils were completed by using the AAS and ICP-MS high performance and selectivity techniques.

Potentially Toxic Elements (PTEs) in Surface Soils of Gemstones and Lead Mining Communities: Differential Mineral Phases and Exposure Risks

Proper human health risk assessments are rarely conducted for mining communities, consequently when there is need for remediation to be conducted and compensation to be paid to impacted population they are typically done, assuming equal exposure risks from varying mining activities. This study was conducted to compare the distribution of potentially toxic elements in surfaces soils of gemstone and lead mining towns in Nigeria, and their anticipated exposure risks. To achieve this thirty-two surface soil samples were collected from Eggon, a gemstone mining town in Nasarawa State and Enyigba, a lead mining town in Ebonyi State. The samples were air dried, disaggregated and sieved through a 2000 μm mesh with the <2000 fraction retained for aqua regia digestion. Potentially toxic elements bound in the samples were quantified with Agilent Technologies 4210 (MP-AES). Mineral phases were identified and quantified using using a inXitu’s portable transmission XRD/XRF instrument (Terra) with a miniature X-ray tube and a CCD detector for collection both XRD signatures. The PTEs, As, Cd, Mn, Pb and Zn were higher in surface soils of lead mining town. At the gemstone mining town most the PTEs indicated similar concentrations at both mine site and residential areas, while at the lead mining town of the PTEs indicated higher concentrations at mine sites and mine road. At the lead mining town the estimated daily exposure doses for Pb were above threshold values irrespective of the exposure scenario. Mineralogy data indicated most of the PTEs in mineralized phases.

Development of a high resolution x-ray inspection system using a carbon nanotube based miniature x-ray tube.

A new concept for a non-destructive testing device using a novel carbon nanotube (CNT) based miniature x-ray tube is proposed. The device can be used for small-scale internal inspection of objects. To investigate the effectiveness of the proposed concept, the device was fabricated and its performance was systematically analyzed. The non-destructive testing device consists of a CNT based miniature x-ray tube, a scintillator, an optical lens, and a detector. The size of the focal spot needed to identify objects as small as 5 µm was calculated through simulation. An electron optics simulation software, E-GUN, was used to optimize the geometries of both the focusing cup and the x-ray target to achieve the desired focal spot size of the x-ray tube. The CNT based miniature x-ray tube was fabricated using the brazing process, and an NdFeB focusing lens was used to further reduce the focal spot size. XR images were obtained using the fabricated device and the spatial resolutions of the images were evaluated using the modulation transfer function (MTF). The fields of view (FOVs) per probe are 7.1 mm2 and 1.8 mm2 when using a 5× optical lens and a 10× optical lens, respectively. The FOV can be increased by increasing the number of probes incorporated into the device. MTF10 values were determined to be 105 lp/mm and 230 lp/mm when using the 5× optical lens and 10× optical lens, respectively. By using an optical lens to enlarge the XR images, the effect of focal spot was minimized and clear XR images were obtained.

Miniature x-ray tubes with field emission cathode from carbon materials

Miniature x-ray tubes with field emission cathode from carbon materials

SmART_scan: A method to produce composition maps using any elemental, molecular and image data

Abstract XRF scanners recently have become the most effective tools for analyzing the distribution of pigments on paintings. They are noninvasive and portable and can be used on flat surfaces of notable dimensions. Powerful miniaturized X-Ray tubes combined with more sensitive detectors make it possible to mount instruments on sturdy motorized X,Y devices, and reduce time needed for a scan. The high-resolution results obtained are of the utmost interest for conservators, art historians and conservation scientists. Drawbacks of XRF scanners are the elevated cost and the bulk of the X,Y devices, which makes them more difficult to transport. It is our opinion that the amount of information collected by a scanner is somewhat redundant. Uniform portions of the painting may be treated as a unity. Following this basic idea, a procedure is proposed to combine a high-resolution visible image with compositional measurement carried out on a grid with a much smaller number of points. Different types of images, spatially registered with respect to the visible one, can be used to increase the amount of information available. A computer program, named SmART_scan, statistically combines all available data, and generates false color maps that show the distribution of elements (XRF), or of compounds [XRD or Raman (Tracey et al., 2006)] over the surface. Even so, the collected information still seemed overabundant. For this reason, the program was adapted to work with a limited number of representative points selected by the user. The measuring time was enormously reduced, and the results were reasonably good. The program can be applied retroactively to previously collected data, provided that a good image, the accurate position of the measurements and their numerical results are available. Examples of maps relative to mockups, real paintings, cross sections and three-dimensional objects are shown.

Brachytherapy utilising miniaturised X-ray tubes – clinical implementation and future applications

Electronic brachytherapy is an advanced radiation treatment technique specifically designed to deliver high doses of radiation inside or very close to the tumor-bearing tissues. Unlike the traditional radionuclide-based brachytherapy, electronic brachytherapy uses a miniaturised x-ray tube that can produce radiation when energised. Most of the electronic brachytherapy systems operate at 50 kVp, therefore posing less radiation exposure to both patients and staff when compared to the standard Cobalt-60 or Iridium-192 based brachytherapy systems. Electronic brachytherapy systems have broader applications that include the treatment of skin, brain, breast, spinal metastasis, endometrium, and cervix. The Axxent Xoft brachytherapy system is a unique system which houses a miniature X-ray tube of 2.25 mm diameter at the tip of a flexible catheter. As a mobile unit, the Xoft system requires less shielding and can be operated in remote centres with minimal radiation shielding facilities. The dose fall-off characteristics mimic those of the low energy isotopes, yet the unit still maintains the high dose rate property of an Ir-192 source. This study details the implementation and commissioning aspects of the Axxent system for intra-operative radiotherapy in Breast Cancer and future applications. Electronic brachytherapy systems have the potential to replace conventional radionuclide-based brachytherapy sources and systems.

Three-dimensional-printed vaginal applicators for electronic brachytherapy of endometrial cancers.

Vaginal applicators for a novel miniature x-ray tube were developed using three-dimensional (3D) printing to be used in brachytherapy of endometrial cancers. Cylindrical vaginal applicators with various diameters, lengths, and infill percentages (IFPs) were fabricated using a 3D printer. X-ray dose distributions and depth-dose profiles were calculated using a Monte Carlo simulation. The performances of the applicators were evaluated by measuring and analyzing the dosimetric characteristics of x rays generated from the miniature x-ray tube equipped with the applicators. Quite uniform dose distributions around the applicators were achieved by optimizing the dwell positions and the dwell times of the miniature x-ray tube inside the applicators. In addition, identical absolute dose and depth-dose profiles were obtained through the control of the IFP values even though different-sized applicators are used. The presented 3D printing technique provides an efficient approach to provide vaginal applicators with optimal IFPs that allow consistent treatment time for patients of varying vaginal canal size.

On-ground calibration of the ART-XC/SRG mirror system and detector unit at IKI. Part II

From October 2016 to September 2017, we performed tests of the ART-XC /SRG spare mirror system and detector unit at the 60-m-long IKI X-ray test facility. We describe some technical features of this test facility. We also present a brief description of the ART-XC mirror system and focal detectors. The nominal focal length of the ART-XC optics is 2700 mm. The field of view is determined by the combination of the mirror system and the detector unit and is equal to ∼0.31 square degrees. The declared operating energy range is 5–30 keV. During the tests, we illuminated the detector with a 55Fe+241 Am calibration source and also with a quasi-parallel X-ray beam. The calibration source is integrated into the detector’s collimator. The X-ray beam was generated by a set of Oxford Instruments X-ray tubes with Cr, Cu and Mo targets and an Amptek miniature X-ray tube (Mini-X) with Ag transmission target. The detector was exposed to the X-ray beam either directly or through the mirror system. We present the obtained results on the detector’s energy resolution, the muon on-ground background level and the energy dependence of the W90 value. The accuracy of a mathematical model of the ART-XC mirror system, based on ray-tracing simulations, proves to be within 3.5% in the main energy range of 4–20 keV and 5.4% in the “hard” energy range of 20–40 keV.

Flexible interventional imaging system based on miniaturized X-ray tubes (FlexScan)

Abstract In orthopedic hand surgeries C-arms are the standard imaging modalities for procedure and tool guidance. However, the currently used systems have a large footprint and high weight, which can lead to workspace restrictions and difficult positioning of the device at the desired imaging position. The aim of this paper is to present a prototype of a new, flexible, lightweight and small footprint X-ray system, which is capable to create 2D projection images from different orientations. The new design includes a miniaturized Xray tube covered in a custom-made case mounted on a flexible holding arm attached to the standard OR table rail. With that, fast positioning and fixation for the subsequent image acquisition is achieved. A flat panel detector is placed in an adjustable metal sheet construction below the table. For safety aspects an overlay of the X-ray cone beam with an integrated light source visualizes the irradiation area. The acquired images are visualized on a 2-in-1 netbook. A foot pedal initiates the imaging process. A prototype of the free movable miniaturized X-ray system FlexScan was build. Workspace restriction, usability and general imaging needs were simulated and tested. FlexScan has the potential to improve X-ray guided interventions on extremities especially for small private surgery centers. It fulfills the general imaging needs and is capable of producing 2D projection images from different orientations within a small and lightweight setup.

P172] Establishment and transfer of a primary dosimetry standard for breast cancer IORT using the INTRABEAM(R) system

Purpose Intraoperative radiation therapy (IORT) using low-energy X-rays (⩽50 keV) delivers a concentrated dose by placing, during surgery, a miniaturized X-ray tube in contact with the treated tumor bed. In France, the most used IORT treatment system is the INTRABEAM one, manufactured by the Zeiss Company, which is delivered with a database used to assess the absolute dose distribution. This work aims at establishing traceability to a dosimetry reference independent from the manufacturer, as recommended in the report published in 2016 by the French National Authority for Health on the evaluation of such treatment. Methods Several types of IORT low-energy photon sources are commercially available and any metrology laboratory cannot afford to be equipped with all of them. So a multi-step methodology, applicable to any of these sources, was developed both to establish and transfer a dosimetry reference. This methodology removes the requirement to bring together, within the same laboratory, the source and the dedicated, but non-transportable, primary standard Free-Air-Chamber (FAC). Firstly, the photon energy spectrum of the commercial source is characterized at the hospital, then the spectrum is reproduced at the primary laboratory using a conventional X-ray generator. The reproduced beam is then characterized, in terms of air kerma rate, using a primary FAC and also used to calibrate a transfer cavity ionization chamber, which is in turn used to calibrate the INTRABEAM® system. Finally, a Monte Carlo model of the source is developed to calculate a conversion factor, from air kerma to absorbed dose to water under reference conditions. Results This methodology was applied to the INTRABEAM® system of a hospital associated with a 4 cm spherical applicator. The absorbed dose to water was established at a depth of 1 cm in water. The Zeiss Company recently changed its dosimetry procedure, going from the TARGIT method to the non-TARGIT one. Our value is higher by 33% and 16% respectively than those given by the TARGIT and non-TARGIT methods. Conclusions The present study shows, for IORT X-ray sources, the importance of making available to end-users independent dosimetry measurements traceable to national standards.

Evaluation of the Effect of Source Geometry on the Output of Miniature X-ray Tube for Electronic Brachytherapy through Simulation.

The use of miniature X-ray source in electronic brachytherapy is on the rise so there is an urgent need to acquire more knowledge on X-ray spectrum production and distribution by a dose. The aim of this research was to investigate the influence of target thickness and geometry at the source of miniature X-ray tube on tube output. Five sources were simulated based on problems each with a specific geometric structure and conditions using MCNPX code. Tallies proportional to the output were used to calculate the results for the influence of source geometry on output. The results of this work include the size of the optimal thickness of 5 miniature sources, energy spectrum of the sources per 50 kev and also the axial and transverse dose of simulated sources were calculated based on these thicknesses. The miniature source geometric was affected on the output x-ray tube. The result of this study demonstrates that hemispherical-conical, hemispherical and truncated-conical miniature sources were determined as the most suitable tools.

Evaluation of the Effect of Source Geometry on the Output of Miniature X-ray Tube for Electronic Brachytherapy through Simulation

Objective: The use of miniature X-ray source in electronic brachytherapy is on the rise so there is an urgent need to acquire more knowledge on X-ray spectrum production and distribution by a dose. The aim of this research was to investigate the influence of target thickness and geometry at the source of miniature X-ray tube on tube output.Method: Five sources were simulated based on problems each with a specific geometric structure and conditions using MCNPX code. Tallies proportional to the output were used to calculate the results for the influence of source geometry on output.Results: The results of this work include the size of the optimal thickness of 5 miniature sources, energy spectrum of the sources per 50 kev and also the axial and transverse dose of simulated sources were calculated based on these thicknesses. The miniature source geometric was affected on the output x-ray tube.Conclusion: The result of this study demonstrates that hemispherical-conical, hemispherical and truncated-conical miniature sources were determined as the most suitable tools.

Surface applicator of a miniature X-ray tube for superficial electronic brachytherapy of skin cancer.

We designed and fabricated a surface applicator of a novel carbon nanotube (CNT)-based miniature X-ray tube for the use in superficial electronic brachytherapy of skin cancer. To investigate the effectiveness of the surface applicator, the performance of the applicator was numerically and experimentally analyzed. The surface applicator consists of a graphite flattening filter and an X-ray shield. A Monte Carlo radiation transport code, MCNP6, was used to optimize the geometries of both the flattening filter and the shield so that X-rays are generated uniformly over the desired region. The performance of the graphite filter was compared with that of conventional aluminum (Al) filters of different geometries using the numerical simulations. After fabricating a surface applicator, the X-ray spatial distribution was measured to evaluate the performance of the applicator. The graphite filter shows better spatial dose uniformity and less dose distortion than Al filters. Moreover, graphite allows easy fabrication of the flattening filter due to its low X-ray attenuation property, which is particularly important for low-energy electronic brachytherapy. The applicator also shows that no further X-ray shielding is required for the application because unwanted X-rays are completely protected. As a result, highly uniform X-ray dose distribution was achieved from the miniature X-ray tube mounted with the surface applicators. The measured values of both flatness and symmetry were less than 5% and the measured penumbra values were less than 1 mm. All these values satisfy the currently accepted tolerance criteria for radiation therapy. The surface applicator exhibits sufficient performance capability for their application in electronic brachytherapy of skin cancers.

Abstract ID: 87 Brachytherapy source and applicator models for diverse Monte Carlo simulations with egs_brachy

Purpose To describe the development and benchmarking of a library of brachytherapy sources and applicators for use with egs_brachy, a new open-source code for brachytherapy calculations. Methods egs_brachy is a modern EGSnrc application employing the EGSnrc C++ class library (egs++) [1] . The extended egs++ framework (new geometry and shape classes developed with egs_brachy) is used to construct detailed models of sources and applicators. Source models are constructed for 52 photon brachytherapy sources (radionuclides Pd-103, I-125, Cs-131, Cs-137, Ir-192, Yb-169, and Co-60). A generic miniature X-ray tube source is modeled. Eye plaque applicators include 10–24 mm diameter Collaborative Ocular Melanoma Study (COMS) plaques (containing I-125 or Pd-103 seeds) and BEBIG Ru-106 beta-emitting plaques (diameters 11.6–25.4 mm). The generic high-dose rate (HDR) Ir-192 shielded applicator of the AAPM-ESTRO-ABG Working Group on Dose Calculation Algorithms for Brachytherapy (WG-DCAB) is modeled. Dose distributions and TG-43 parameters (photon sources only) computed with egs_brachy are compared with published values. Results For photon (radionuclide) sources, dose-rate constant, radial dose function, and anisotropy function values are generally in excellent agreement with published values [2] . Miniature X-ray tube results for egs_brachy agree with BrachyDose results within statistical uncertainties. Ocular plaque dose distributions show excellent agreement with published values. For COMS plaques, egs_brachy results agree with BrachyDose and MCNP5 published values within uncertainties [3] . For Ru-106 beta-emitting plaques, egs_brachy results agree within sub-2% uncertainties with PENELOPE results [4] , and this agreement is notable due to the historically poor agreement between results from different publications. Dose distributions about the WG-DCAB applicator agree with results from other MC codes. Conclusions egs_brachy can model diverse source and applicator models and dose distributions are in excellent agreement with published values, demonstrating the code’s versatility and accuracy. Source and applicator models will be included in future egs_brachy distributions.

Miniature CNT-based X-ray tube: assessment for use in intraoperative radiation therapy

Abstract Carbon nanotube (CNT) is a new technology used to generate gamma photons in X-ray tubes. CNTs, in comparison to other small X-ray sources, produce high X-ray intensities and as they are not based on a thermionic principle they considered cold electron sources with a very high conversion of electrical to photon energy. Their small size and other interesting properties could make them feasible for use in intraoperative radiation therapy applications. In this study, physical characteristics of the photon beam generated by the CNT-based X-ray source were assessed. A soft X-ray ionization chamber and a flat panel detector was used to measure dose and photon counts, respectively. The repetitively produced pulses had almost the same photon intensities with differences of less than 1% between them. For a typical selected pulse, the variation in the pulse amplitude was also insignificant, which shows a stable radiation exposure of the tube during the ON-mode. When moving from the center of the beam profile to the lateral distance of 25 mm, both intensity profile and dose profile showed a falling trend by a factor of almost 3 in the measured values. We also tested the miniature tube with our novel radiation beam shaping collimator designed for a possible application to treat larynx tumor, which showed the possibility of interventional radiation therapy using this miniature source. An endoscopic camera attached to the system can also make it possible to optically visualize the radiation exposed area. In conclusion, CNT-based X-ray source with suitable attached collimator to shape the beam of the source, seems to provide an opportunity to deliver radiation to a desired tumor area in minimally invasive image guided medical procedures mainly in the normal cavities of the body.

Trans-oral miniature X-ray radiation delivery system with endoscopic optical feedback

PurposeSurgery, chemo- and/or external radiation therapy are the standard therapy options for the treatment of laryngeal cancer. Trans-oral access for the surgery reduces traumata and hospitalization time. A new trend in treatment is organ-preserving surgery. To avoid regrowth of cancer, this type of surgery can be combined with radiation therapy. Since external radiation includes healthy tissue surrounding the cancerous zone, a local and direct intraoral radiation delivery would be beneficial.MethodsA general concept for a trans-oral radiation system was designed, based on clinical need identification with a medical user. A miniaturized X-ray tube was used as the radiation source for the intraoperative radiation delivery. To reduce dose distribution on healthy areas, the X-ray source was collimated by a newly designed adjustable shielding system as part of the housing. For direct optical visualization of the radiation zone, a miniature flexible endoscope was integrated into the system. The endoscopic light cone and the field of view were aligned with the zone of the collimated radiation. The intraoperative radiation system was mounted on a semi-automatic medical holder that was combined with a frontal actuator for rotational and translational movement using piezoelectric motors to provide precise placement.ResultsThe entire technical set-up was tested in a simulated environment. The shielding of the X-ray source was verified by performing conventional detector-based dose measurements. The delivered dose was estimated by an ionization chamber. The adjustment of the radiation zone was performed by a manual controlling mechanism integrated into the hand piece of the device. An endoscopic fibre was also added to offer visualization and illumination of the radiation zone. The combination of the radiation system with the semi-automatic holder and actuator offered precise and stable positioning of the device in range of micrometres and will allow for future combination with a radiation planning system.ConclusionsThe presented system was designed for radiation therapy of the oral cavity and the larynx. This first set-up tried to cover all clinical aspects that are necessary for a later use in surgery. The miniaturized X-ray tube offers the size and the power for intraoperative radiation therapy. The adjustable shielding system in combination with the holder and actuator provides a precise placement. The visualization of radiation zone allows a targeting and observation of the radiation zone.

An update on carbon nanotube-enabled X-ray sources for biomedical imaging.

A new imaging technology has emerged that uses carbon nanotubes (CNT) as the electron emitter (cathode) for the X-ray tube. Since the performance of the CNT cathode is controlled by simple voltage manipulation, CNT-enabled X-ray sources are ideal for the repetitive imaging steps needed to capture three-dimensional information. As such, they have allowed the development of a gated micro-computed tomography (CT) scanner for small animal research as well as stationary tomosynthesis, an experimental technology for large field-of-view human imaging. The small animal CT can acquire images at specific points in the respiratory and cardiac cycles. Longitudinal imaging therefore becomes possible and has been applied to many research questions, ranging from tumor response to the noninvasive assessment of cardiac output. Digital tomosynthesis (DT) is a low-dose and low-cost human imaging tool that captures some depth information. Known as three-dimensional mammography, DT is now used clinically for breast imaging. However, the resolution of currently-approved DT is limited by the need to swing the X-ray source through space to collect a series of projection views. An array of fixed and distributed CNT-enabled sources provides the solution and has been used to construct stationary DT devices for breast, lung, and dental imaging. To date, over 100 patients have been imaged on Institutional Review Board-approved study protocols. Early experience is promising, showing an excellent conspicuity of soft-tissue features, while also highlighting technical and post-acquisition processing limitations that are guiding continued research and development. Additionally, CNT-enabled sources are being tested in miniature X-ray tubes that are capable of generating adequate photon energies and tube currents for clinical imaging. Although there are many potential applications for these small field-of-view devices, initial experience has been with an X-ray source that can be inserted into the mouth for dental imaging. Conceived less than 20 years ago, CNT-enabled X-ray sources are now being manufactured on a commercial scale and are powering both research tools and experimental human imaging devices. WIREs Nanomed Nanobiotechnol 2018, 10:e1475. doi: 10.1002/wnan.1475 This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

TU-AB-BRC-08: Egs_brachy, a Fast and Versatile Monte Carlo Code for Brachytherapy Applications

Purpose: To introduce egs_brachy, a new, fast, and versatile Monte Carlo code for brachytherapy applications. Methods: egs_brachy is an EGSnrc user-code based on the EGSnrc C++ class library (egs++). Complex phantom, applicator, and source model geometries are built using the egs++ geometry module. egs_brachy uses a tracklength estimator to score collision kerma in voxels. Interaction, spectrum, energy fluence, and phase space scoring are also implemented. Phase space sources and particle recycling may be used to improve simulation efficiency. HDR treatments (e.g. stepping source through dwell positions) can be simulated. Standard brachytherapy seeds, as well as electron and miniature x-ray tube sources are fully modelled. Variance reduction techniques for electron source simulations are implemented (Bremsstrahlung cross section enhancement, uniform Bremsstrahlung splitting, and Russian Roulette). TG-43 parameters of seeds are computed and compared to published values. Example simulations of various treatments are carried out on a single 2.5 GHz Intel Xeon E5-2680 v3 processor core. Results: TG-43 parameters calculated with egs_brachy show excellent agreement with published values. Using a phase space source, 2% average statistical uncertainty in the PTV ((2mm)3 voxels) can be achieved in 10 s for 100 125I or 103Pd seeds in a 36.2 cm3 prostate PTV, 31 s for 64 103Pd seeds in a 64 cm3 breast PTV, and 56 s for a miniature x-ray tube in a 27 cm3 breast PTV. Comparable uncertainty is reached in 12 s in a (1 mm)3 water voxel 5 mm away from a COMS 16mm eye plaque with 13 103Pd seeds. Conclusion: The accuracy of egs_brachy has been demonstrated through benchmarking calculations. Calculation times are sufficiently fast to allow full MC simulations for routine treatment planning for diverse brachytherapy treatments (LDR, HDR, miniature x-ray tube). egs_brachy will be available as free and open-source software to the medical physics research community. This work is partially funded by the Canada Research Chairs program, the Natural Sciences and Engineering Research Council of Canada, and the Ontario Ministry of Research and Innovation (Ontario Early Researcher Award).