Low-energy X-ray Source Research Articles

Design and characterization of a new high-count wide-range fission chamber based on GEM

As one of the main detectors for monitoring neutron flux rate in a nuclear reactor, the fission chamber (FC) suffers from issues such as low sensitivity, limited counting rate dynamic range, and system mode switching is cumbersome. This study utilizes the advantages of gas electron multipliers (GEM), which are easy to fabricate in large areas and have high counting rates, to design a novel fission chamber. By conducting Monte Carlo simulations on parameters such as the thickness of the 235U coating, the drift distance, and the operating electric field strength, a wide-range fission chamber design that combines high sensitivity and a counting rate range based on GEM has been obtained. The simulation results demonstrated that using a GEM detector to build a fission chamber can significantly improve sensitivity and extend the counting rate range. Subsequently we built a proof-of-concept GEM-based fission chamber and tested it with a 55Fe low-energy X-ray source and an Am-Be neutron source. The results showed that the proof-of-concept detector had a good signal-to-noise ratio and energy linearity, as well as clear discrimination between alpha background and neutron pulse amplitudes.

Fabrication, Structural Characterization, and Photon Attenuation Efficiency Investigation of Polymer-Based Composites.

Experiments have assessed various polymer composites for radiation shielding in diverse applications. These composites are lighter and non-toxic when compared to lead (Pb), making them particularly effective in diagnostic imaging for shielding against low-energy photons. This study demonstrates the fabrication of four composites by combining a base material, specifically a high-density polyethylene (HDPE) polymer, with 10% and 20% silicon (Si) and silicon carbide (SiC), respectively. Additionally, 5% molybdenum (Mo) was incorporated into the composites as a heavy metal element. The composites obtained were fabricated into 20 disks with a uniform thickness of 2 mm each. Discs were exposed to radiation from a low-energy X-ray source (32.5-64.5 keV). The chemical and physical properties of composites were assessed. The shielding ability of samples was evaluated by determining the linear and mass attenuation coefficients (μ and μm), radiation protection efficiency (RPE), half-value layer (HVL), and mean free path (MFP). According to our findings, supplementing HDPE with additives improved the attenuation of beams. The μm values showed that composite X-ray shielding characteristics were enhanced with filler concentration for both Si and SiC. Polymer composites with micro-molecule fillers shelter X-rays better than polymers, especially at low energy. The HVL and MFB values of the filler are lower than those of the pure HDPE sample, indicating that less thickness is needed to shield at the appropriate energy. HC-20 blocked 92% of the incident beam at 32.5 keV. This study found that increasing the composite sample thickness or polymer filler percentage could shield against low-energy radiation.

Intraoperative radiotherapy for resectable pancreatic cancer using a low-energy X-ray source: Follow-up outcomes

Intraoperative radiotherapy for resectable pancreatic cancer using a low-energy X-ray source: Follow-up outcomes

Absolute light yield of the EJ-204 plastic scintillator

The absolute light yield of a scintillator, defined as the number of scintillation photons produced per unit energy deposited, is a useful quantity for scintillator development, research, and applications. Yet, literature data on the absolute light yield of organic scintillators are limited. The goal of this work is to assess the suitability of the EJ-204 plastic scintillator from Eljen Technology to serve as a reference standard for measurements of the absolute light yield of organic scintillators. Four EJ-204 samples were examined: two manufactured approximately four months prior and stored in high-purity nitrogen, and two aged approximately eleven years and stored in ambient air. The scintillator response was measured using a large-area avalanche photodiode calibrated using low energy γ-ray and X-ray sources. The product of the quantum efficiency of the photodetector and light collection efficiency of the housing was characterized using an experimentally-benchmarked optical photon simulation. The average absolute light yield of the fresh samples, 9100 ± 400 photons per MeV, is lower than the manufacturer-reported value of 10400 photons per MeV. Moreover, the aged samples demonstrated significantly lower light yields, deviating from the manufacturer specification by as much as 26%. These results are consistent with recent work showcasing environmental aging in plastic scintillators and suggest that experimenters should use caution when deploying plastic scintillators in photon counting applications.

Biological Characterization of the Effects of Filtration on the Xoft Axxent® Electronic Brachytherapy Source for Cervical Cancer Applications.

Low-energy X-ray sources that operate in the kilovoltage energy range have been shown to induce more cellular damage when compared to their megavoltage counterparts. However, low-energy X-ray sources are more susceptible to the effects of filtration on the beam spectrum. This work sought to characterize the biological effects of the Xoft Axxent® source, a low-energy therapeutic X-ray source, both with and without the titanium vaginal applicator in place. It was hypothesized that there would be an increase in relative biological effectiveness (RBE) of the Axxent® source compared to 60Co and that the source in the titanium vaginal applicator (SIA) would have decreased biological effects compared to the bare source (BS). This hypothesis was drawn from linear energy transfer (LET) simulations performed using the TOPAS Monte Carlo user code as well a reduction in dose rate of the SIA compared to the BS. A HeLa cell line was maintained and used to evaluate these effects. Clonogenic survival assays were performed to evaluate differences in the RBE between the BS and SIA using 60Co as the reference beam quality. Neutral comet assay was used to assess induction of DNA strand damage by each beam to estimate differences in RBE. Quantification of mitotic errors was used to evaluate differences in chromosomal instability (CIN) induced by the three beam qualities. The BS was responsible for the greatest quantity of cell death due to a greater number of DNA double strand breaks (DSB) and CIN observed in the cells. The differences observed in the BS and SIA surviving fractions and RBE values were consistent with the 13% difference in LET as well as the factor of 3.5 reduction in dose rate of the SIA. Results from the comet and CIN assays were consistent with these results as well. The use of the titanium applicator results in a reduction in the biological effects observed with these sources, but still provides an advantage over megavoltage beam qualities. © 2023 by Radiation Research Society.

Alanine response to low energy synchrotron x-ray radiation

Objective. The radiation response of alanine is very well characterized in the MV photon energy range where it can be used to determine the dose delivered with an accuracy better than 1%, making it suitable as a secondary standard detector in cancer radiation therapy. This is not the case in the very low energy keV x-ray range where the alanine response is affected by large uncertainties and is strongly dependent on the x-ray beam energy. This motivated the study undertaken here. Approach. Alanine pellets with a nominal thickness of 0.5 mm and diameter of 5 mm were irradiated with monoenergetic x-rays at the Diamond Light Source synchrotron, to quantify their response in the 8–20 keV range relative to 60Co radiation. The absorbed dose to graphite was measured with a small portable graphite calorimeter, and the DOSRZnrc code in the EGSnrc Monte Carlo package was used to calculate conversion factors between the measured dose to graphite and the absorbed dose to water delivered to the alanine pellets. GafChromic EBT3 films were used to measure the beam profile for modelling in the MC simulations. Main results. The relative responses measured in this energy range were found to range from 0.616 to 0.643, with a combined relative expanded uncertainty of 3.4%–3.5% (k = 2), where the majority of the uncertainty originated from the uncertainty in the alanine readout, due to the small size of the pellets used. Significance. The measured values were in good agreement with previously published data in the overlapping region of x-ray energies, while this work extended the dataset to lower energies. By measuring the response to monoenergetic x-rays, the response to a more complex broad-spectrum x-ray source can be inferred if the spectrum is known, meaning that this work supports the establishment of alanine as a secondary standard dosimeter for low-energy x-ray sources.

Intraoperative Radiotherapy for Resectable Pancreatic Cancer Using a Low-energy X-ray Source: Follow-up Outcomes

Intraoperative Radiotherapy for Resectable Pancreatic Cancer Using a Low-energy X-ray Source: Follow-up Outcomes

Long-Term Results Following Use of Vaginal Electronic Brachytherapy in the Management of Endometrial Cancer

<h3>Purpose/Objective(s)</h3> We evaluated long-term vaginal toxicity and disease outcomes in women treated with vaginal electronic brachytherapy (EBT) following surgical management of endometrial cancer. <h3>Materials/Methods</h3> Women with endometrial cancer treated with adjuvant EBT were included in this study. Women diagnosed with uterine cancer of high-risk histology or advanced stage received EBT following completion of adjuvant chemotherapy. EBT was performed using a miniature low-energy (50-kV peak) X-ray source with a single-channel vaginal cylinder applicator to deliver radiation to the vagina along a specified length of the cylinder. EBT was delivered either as monotherapy or as a sequential boost following completion of pelvic external beam radiation (EBRT). EBT was delivered to 4 cm treatment length prescribed as 7 Gy to 5 mm depth x 3 fractions in the EBT alone group or 6 Gy to vaginal surface x 3 fractions in the EBT boost group. Following completion of EBT, patients were evaluated for all toxicities and recurrences. In this study, we evaluated for treatment related vaginal toxicity (stenosis) which was scored according to the Common Terminology Criteria for Adverse Events version 5.0. Multivariable analysis (MVA) of prognostic factors was performed using Cox Proportional-Hazards Model, and disease-free survival (DFS) and overall survival (OS) were estimated from date of surgery with Kaplan-Meier Method using data management and decision management software. <h3>Results</h3> 70 women were treated from 12/2017-6/2020 with EBT following hysterectomy. Median age of the cohort was 68 years (range, 51-85 years). 37 presented with endometrioid histologies. 32 received adjuvant chemotherapy prior to EBT. 21 presented with stage II or greater disease, and 20 received EBRT prior to EBT boost. EBT was delivered over a median interval of 1.3 weeks (range, 0.3-3.1 weeks). At a median follow-up of 25.0 months (range, 7.2-47.4 months), no patients were found to have ≥ grade 3 vaginal toxicity. The cumulative risk of developing gr 1 and 2 vaginal toxicity at 30 months was 25%. Prescription to 5 mm depth was the only factor associated with development of vaginal toxicity (p<0.05). One vaginal cuff recurrence, one locoregional recurrence, and ten distant recurrences were observed. Advanced tumor stage, high-risk histology, cervical stroma involvement, treatment with chemotherapy, and treatment with EBRT were significantly associated with inferior DFS/OS on MVA. DFS and OS in this group at 12 and 36 months were 94.2%/69.4% and 95.7%/88.3%, respectively. <h3>Conclusion</h3> EBT appears to be a safe, well-tolerated, and a promising alternative treatment option to traditional vaginal brachytherapy using a radioactive source. On MVA, prescription of EBT to 5 mm depth was associated with vaginal stenosis. One local recurrence was observed at 25 months follow-up. Risk of developing vaginal toxicity, DFS, and OS, following treatment with EBT in this heterogeneous population appear to be acceptable and comparable to historical controls (PORTEC 2 PMID 20206777).

Characterization of a low-pressure Micro-Megas-like gaseous detector with low energy x-ray sources

Within the family of the Micro Strip Gas Detectors (MSGD), the intrinsic characteristics of the bulk Micro-Megas (MM) device represent the most promising features for the construction of a new instrument to be operated as a TPC gas chamber in a low-pressure regime. In this study, we present the main properties of a low-pressure bulk MM detector in which the amplification gap was slightly increased to improve the gas gain. Two configurations have been deeply studied: the first one with a gap of 128μm and a second one with a 192μm gap, both filled and operated with a gas mixture (Ar-CO2) at pressures below 100 mbar. The dependence of the gain and the energy resolution on the amplification field, gas pressure and drift field have been evaluated. The reliability of the measured performance, combined with the simple and robust structure of the detector even with an increased length of amplification gap, make it an attractive choice for applications where the track length of low energy particles is detected by using a low-pressure filling gas.

Low-energy X-ray irradiation: A novel non-thermal microbial inactivation technology.

Over the last several decades, food irradiation technology has been proven neither to reduce the nutritional value of foods more than other preservation technologies, nor to make foods radioactive or dangerous to eat. Furthermore, food irradiation is a non-thermal food processing technology that helps preserve more heat sensitive nutrients than those found in thermally processed foods. Conventional food irradiation technologies, including γ-ray, electron beam and high energy X-ray, have certain limitations and drawbacks, such as involving radioactive isotopes, low penetration ability, and economical unfeasibility, respectively. Owing to the recent developments in instrumentation technology, more compact and cheaper tabletop low-energy X-ray sources have become available. The generation of low-energy X-ray, unlike γ-ray, does not involve radioactive isotopes and the cost is lower than high energy X-ray. Furthermore, low-energy X-ray possesses unique advantages, i.e., high linear energy transfer (LET) value and high relative biological effect (RBE) value. The advantages allow low-energy X-ray irradiation to provide a higher microbial inactivation efficacy than γ-ray and high energy X-ray irradiation. In the last few years, various applications reported in the literature indicate that low-energy X-ray irradiation has a great potential to become an alternative food preservation technique. This chapter discusses the technical advances of low-energy X-ray irradiation, microbial inactivation mechanism, factors influencing its efficiency, current applications, consumer acceptance, and limitations.

Response of the Ti and Al electron spin resonance signals in quartz to X-ray irradiation

Equivalent dose determination with electron spin resonance (ESR) involves laboratory irradiation of samples using a calibrated source. In this study, we investigated the response of the quartz ESR signals to irradiations from 50 kV or 200 kV X-ray sources by inter-comparison with 60Co gamma irradiation using seven quartz samples of different origins. For each sample, the equivalent X-ray irradiation time required to create the same concentration of defects as a known dose of 60Co gamma-ray was calculated. The effective dose rate was obtained from the given gamma dose (188 Gy) divided by the equivalent X-ray irradiation time; this is referred to as the ‘X-ray dose rate’ in this study. The X-ray dose rate estimates from different samples were relatively uniform. However, the dose rate calculated from the Al centre was on average ∼10% higher than that of the Ti centre, and more scattered among different samples especially for the low-energy X-ray source. The ratio of the dose rates, obtained from the two centres (Al/Ti) varied significantly between the samples; four sediment samples from Tajikistan, China, Chile and Greece yielded consistent dose rates from both centres for both sources, whereas the remaining three samples from Japan and Taiwan showed a dose rate up to 26% higher from the Al centre compared to the Ti centre. The cause of the higher effective dose rate for the Al centre for these three samples requires further investigations.

Computational simulation of low energy x-ray source for photodynamic therapy: a preliminary study

Photodynamic therapy is a therapeutic modality capable of selectively inducing cytotoxic effects in malignant cells. Such effects are obtained by using a laser or a lamp as a light source to irradiate a previously-delivered photosensitizer into the tumoral cells. Since clinical application of photodynamic therapy depends on light penetration, lasers and lamps can only be used for shallow tissue treatment. To overcome this limitation, x-ray induced photodynamic therapy has been recently proposed. The goal of this work is to investigate the x-ray interactions in a medium containing a homogeneous concentration of distinct photosensitizers. This is achieved by evaluating the relative doses and energy spectra, obtained at distinct depths by means of Monte Carlo simulations. Preliminary results for the relative dose showed a minor dose increase, of approximately 0.15%, when photosensitizers are used. In addition, x-ray interactions with the investigated photosensitizers mostly occur from photons with energies below 60 keV.

X-ray photons produced from a plasma-cathode electron beam for radiation biology applications

A compact low-energy and high-intensity x-ray source for radiation biology applications is presented. A laser-induced plasma moves inside a 30 kV diode and produces a beam of 1014 electrons at the anode location. An aluminum foil converts a part of the energy of these electrons into x-ray photons, which are characterized using filtered imaging plates. The dose that would be deposited by these x-ray photons in C. elegans larvae is calculated from Geant4 simulations. It can be set to a value ranging between 10 μGy and 10 mGy per laser shot by simply changing the aluminum foil thickness and the diode voltage. Therefore, this versatile and compact x-ray source opens a new path to explore the radiation effects induced by dose rates varying over several orders of magnitude.

Dosimetric Evaluation of Electronic Brachytherapy for Postsurgical Vaginal Cuff Irradiation in Endometrial Cancer

We evaluated dosimetric parameters associated with acute toxicity in women with endometrial cancer treated with electronic brachytherapy (EBT) to the vaginal cuff. This dosimetric study included women with endometrial cancer treated with EBT following surgery. The EBT system uses a miniature low-energy (50-kV peak) X-ray source with a single-channel vaginal cylinder applicator to deliver radiation to the vaginal target along a specified length of the cylinder. EBT was delivered either as monotherapy or as a sequential boost following completion of pelvic external beam radiation (EBRT). EBT was delivered using either a 2.5 cm, 3.0 cm, or 3.5 cm diameter vaginal cylinder. EBT was generally delivered to 4 cm treatment length, prescribed as 7 Gy to 5 mm depth x 3 fractions in the monotherapy group or 6 Gy to vaginal surface x 3 fractions in the boost group. Dosimetric evaluation of EBT plans included measurement of maximum vaginal mucosal surface dose, minimum dose in the most irradiated 2 cc volume (D2cc) of bladder, rectum, and bowel structures. Patients were followed by their treating physician to evaluate treatment response and toxicity. EBT plans were evaluated in 50 consecutive patients treated between 2017-2019. Median time to completion of EBT was 1.3 weeks (range, 0.3-2.3 weeks). Dosimetric treatment parameters were as follows (mean, standard deviation): maximum mucosal dose relative to prescription dose (156.6%, 35.3%), bladder D2cc (3.8 Gy, 1.3 Gy), rectum D2cc (4.4 Gy, 1.6 Gy), bowel D2cc (1.6 Gy, 1.2 Gy). At a median follow-up of 1.6 months (range, 0.4-4.1 months), 9 (18%) patients presented with acute grade 1 GI toxicity, 7 (14%) presented with acute grade 1 GU toxicity, and 7 (14%) presented with acute grade 1-2 GYN toxicity. On univariate analysis, smaller EBT cylinder diameter size (p<0.01), but not maximum vaginal mucosal surface dose (p = 0.11) was associated with vaginal stenosis. There was no significant association between bowel or rectum D2cc with GI toxicity, and bladder D2cc with GU toxicity. EBT is an alternative form of vaginal brachytherapy designed to reduce radiation safety shielding requirements, potentially improving patient access to brachytherapy. EBT dose to organs at risk and vaginal surface mucosa appear comparable to those generated on high dose rate source-based brachytherapy systems. Smaller EBT cylinder diameter was associated with vaginal stenosis. Further evaluation is warranted to characterize late toxicity and tumor control outcomes.

A prospective, single-arm, phase II clinical trial of intraoperative radiotherapy using a low-energy X-ray source for local advanced Laryngocarcinoma (ILAL): a study protocol

BackgroundLaryngocarcinoma (LC), in most cases a squamous cell carcinoma, accounts for 1 ~ 5% of the incidence of all tumors. At present, laryngocarcinoma is mainly managed with the integration of surgery and radio- and chemo-therapies. The current development trend of treatment is to improve the local control rate of tumor and the quality of life of patients. Intraoperative radiation therapy (IORT) is a radiotherapy that delivers single high dose irradiation at a close range to the tumor bed during the surgical operation process. It has particular radiobiological advantages in protecting normal surrounding tissues by directly applying the irradiation dose to the high-risk tumor bed area.Two forms of IORT, i.e., high dose rate (HDR) brachytherapy and external beam radiotherapy (EBRT, including electron and photono IORT), had been studied before the treatment of head and neck tumors (including laryngocarcinoma). However, no relevant assessment had been carried out on 50KV low-energy X-ray. We are convinced by certain arguments that the application of low-energy X-ray for intraoperative local radiotherapy of laryngocarcinoma can not only achieve the therapeutic effect of IORT but also reduce the incidence of high-energy irradiation related toxic and side effects. The purpose of this study is to observe the safety and short-term efficacy of IORT when used in conjunction with standard of care for the treatment of local advanced laryngocarcinoma (LAL).Methods/designIn consideration of the applications of precise targeted IORT in oncosurgery and in line with the application range and reference clinical medical guidances approved by SFDA (ZEISS radiosurgical operation system has been used for the treatment of solid tumors since 31 December, 2013 with an approval from SFDA), we have preliminarily planned the tumors suitable for IORT, determined the members of MDT in our hospital, improved the MDT diagnosis and treatment processes for the tumors, established the standards, indications and contraindications for the application of IORT, determined the indicators to be observed after the treatment of tumors with surgical operations plus IORT, and carried out follow-up visits and statistical analysis.This is a single-arm, prospective Phase II clinical trial of the treatment of LAL patients with IORT + EBRT. The study subjects are followed up for statistics and information of their acute/chronic toxic reactions and local control rate, DFS, and OS etc. The safety and short-term efficacy of the application of IORT as SIB for the treatment of LAL. The sample size of the study is 125 subjects.DiscussionThe safety and efficacy of IORT for the treatment of head and neck cancers have been proven in studies by multiple institutions (1–3). The purpose of this study is to investigate the maximum safe dose and short-term efficacy of IORT for providing a theoretical basis for clinical trials.Trial registrationTrial registration: Clinicaltrials.gov, NCT04278638. Registered 18 February 2020 - prospectively registered, https://clinicaltrials.gov/ct2/show/NCT04278638

Experimental determination of the gadolinium dose enhancement in phantom irradiated with low energy X-ray sources by a spectrophotometer -Gafchromic-EBT3 dosimetry system

This work reports the experimental determination of dose enhancement produced in phantoms containing target volumes doped with Gadolinium and irradiated with low-energy X-ray beams. EBT3 Gafchromic films were immersed into 5 ml target volumes to simulate tumor filling with 100% ultra-pure water (blank sample) and ultra-pure water infused with Gd solution (Omniscan®) in different concentration (9–24 mg/ml). The dose enhancement due to excitation of Gd K-edge (50.2 keV) was evaluated in terms of the increment in optical density, obtained by a Spectrophotometer-Gafchromic-EBT3 dosimetry system calibrated in terms of the dose-response for 1–8 Gy range. The dose enhancement was evaluated in two condition: a beam quality with spectrum above the absorption edge in a medium with and without Gd; and two beam qualities (above and below the absorption edge) in a medium with a fixed Gd concentration (18 mg/ml). The obtained results confirmed increments in relative dose enhancement according to Gd concentrations up to 18 mg/ml, with a dose enhancement of 1.1 Gy and an average percentage enhancement of 28.4%. For higher values of concentration, the attenuation interaction of the primary beam is more relevant instead of dose enhancement process. On the other hand, the dose enhancement obtained to comparison the spectra above and below the absorption edge, shown results up to 3.3 Gy of enhancement and average percentage enhancement of 88%.

High beam-current density of a 10-keV nano-focus X-ray source

Abstract The electron beam-current density at a target greatly affects imaging intensity and contrast when using a low-energy nano-focus X-ray source. This paper proposes a new electron gun comprising a 10-keV nano-focus X-ray source with a single-pole magnetic lens to improve its effective brightness and beam-current density. After analyzing the effect of the electric field on the extended Schottky emission, we first optimized the anode with high effective brightness and a fine virtual spot with enough intensity for nano-focus X-ray imaging. High effective beam-current density was then obtained by optimizing the position, geometry and electrical supplies of the single-pole magnetic lens. The effective brightness of this electron gun is 1.70 × 108 A•cm−2•sr−1, and the nano-focus X-ray source has a spot size of 41 nm when its tube current is 2 μ A. This electron gun achieves higher beam current density (1.6 × 105A•cm−2), and its collimated landing beam efficiently transports the beam current in the X-ray source.

A phase II study of intraoperative radiotherapy using a low-energy x-ray source for resectable pancreatic cancer: a study protocol

BackgroundThe current standard treatment for resectable pancreatic cancer is surgical resection followed by adjuvant chemotherapy. Local recurrence rates are high even after curative resection; thus, the long-term outcome of locally advanced pancreatic cancer remains poor. Intraoperative radiotherapy (IORT) uses a low-energy x-ray source to deliver a single fraction of high-dose radiation to the tumor bed during a surgical procedure, while effectively sparing the surrounding normal tissues. IORT has the potential to improve the efficacy of radiation therapy for pancreatic cancer.Methods/designThis prospective, one-armed, phase II study will investigate the role of IORT in improving local control in patients with resectable pancreatic adenocarcinoma. The patients will receive surgery and IORT of 10 Gy prescribed at a 5-mm depth of the tumor bed, followed by adjuvant gemcitabine chemotherapy according to the current standard of care. The aim is to enroll 42 patients.DiscussionThe primary endpoint of this trial is to evaluate the feasibility of IORT and the local recurrence rate after one year. The secondary endpoints include the acute and late toxicities, and disease-free survival and overall survival rates.Trial registrationThe trial was prospectively registered at Clinicaltrials.gov NCT03273374 on September 6, 2017.

Synthesis and Characterization of Titanium Dioxide Nanoparticles with a Dosimetry Study of their Ability to Enhance Radiation Therapy using a Low Energy X-ray Source

Objective: This study was undertaken to synthesize and characterize TiO2 NPs and to study the interaction of TiO2 NPs with radiation and then estimate the Dose-enhancement Factor (DEF) at different concentrations of NPs under low-energy excitation (14-35 kV). Methods: Titanium dioxide (TiO2 ) Nanoparticles (NPs) were synthesized by the sol-gel method. The structure, particle size and crystal phase were evaluated by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). Findings: The XRD pattern exhibited peaks that were assigned to analyse crystals with particle sizes from 2-10 nm. The X-ray absorption of TiO2 NP solutions and pure water were investigated. Solutions with 0, 3.33, 6.66 and 20% of the TiO2 NPs were used to study the X-ray absorption of the samples and the Dose Enhancement Factor (DEF) is evaluated. The experimental results showed that the X-ray absorption for solutions with 0, 3.33, 6.66 and 20% of the TiO2 NPs increased with increasing concentration for generated beams from 14 kV to 35 kV. Additionally, a Dose-enhancement Factor (DEF) was observed for low-energy beams between 14 kV and 35 kV. TiO2 NPs at very low energies (14-35 kV) able to display significantly enhanced X-ray absorption, resulting in a higher absorbed dose. Application/Improvements: Many scientists have focused on nanoparticles, such as TiO2 NPs, due to their numerous functions that enhance the nature of their antibacterial properties. Cancer is one of the reasons for human mortality. The main concept of cancer radiotherapy is the enhance radiation dose absorption at the targeted site by using high-Z materials. Keywords: Dosimetry, Low Energy Source, Nanoparticles, Radiation Therapy, Titanium Dioxide

An investigation into the INTRABEAM miniature x-ray source dosimetry using ionization chamber and radiochromic film measurements.

Intraoperative radiotherapy using The INTRABEAM System (Carl Zeiss Meditec AG, Jena, Germany), a miniature low-energy x-ray source, has proven to be an effective modality in the treatment of breast cancer. However, some uncertainties remain in its dosimetry. In this work, we investigated the INTRABEAM system dosimetry by performing ionization chamber and radiochromic film measurements of absorbed dose in a water phantom. Ionization chamber measurements were performed with a PTW 34013 parallel-plate soft x-ray chamber at source to detector distances of 5 to 30 mm calculated using (a) the dose formula consistent with the TARGIT breast protocol (TARGIT), (b) the formula recommended by the manufacturer (Zeiss), and (c) the recently proposed CQ formalism of Watson et al. (Physics in Medicine & Biology, 2018;63:015016) EBT3 Gafchromic film measurements were made at the same depths in water. To account for the energy dependence of EBT3 film, multiple dose response calibration curves were employed across a range of photon beam qualities relevant to the INTRABEAM spectrum in water. At all depths investigated, the TARGIT dose was significantly lower than that measured by the Zeiss and CQ methods, as well as film. These dose differences ranged from 14% to as large as 80%. In general, the doses measured by film, and the Zeiss and CQ methods were in good agreement to within measurement uncertainties (5-6%). These results suggest that the TARGIT dose underestimates the physical dose to water from the INTRABEAM source. Understanding the correlation between the TARGIT and physical dose is important for any studies wishing to make dosimetric comparisons between the INTRABEAM and other radiation emitting devices.