Low-energy X-ray Research Articles

Synchrotron light source X-ray detection with Low-Gain Avalanche Diodes

Low Gain Avalanche Diodes (LGADs) represent the state-of-the-art in timing measurements and will instrument the future Timing Detectors of ATLAS and CMS for the High-Luminosity LHC. While initially conceived as a sensor for charged particles, the intrinsic gain of LGADs makes it possible to detect low-energy X-rays with good energy resolution and excellent time resolution (tens of picoseconds). Using the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC, several LGADs designs were characterized with energies from 5 to 70 keV. The SSRL provides 10 ps pulsed X-ray bunches separated by 2 ns intervals with an energy dispersion (ΔE/E) of 10-4. LGADs from Hamamatsu Photonics (HPK) and Brookhaven National Laboratory (BNL) with different thicknesses ranging from 20 μm to 50 μm and different gain layer designs were read out using fast amplification boards and digitized with a high bandwidth and high sampling rate oscilloscope. PIN devices from HPK and AC-LGADs from BNL were characterized as well. A systematic and detailed characterization of the devices' energy linearity, resolution, and time resolution as a function of X-ray energy was performed for different biasing voltages at room temperature and are reported in this work. The charge collection and multiplication mechanism were simulated using Geant4 and TCAD Sentaurus, providing an important handle for interpreting the data.

Development of a silicone-based radio-fluorogenic dosimeter using dihydrorhodamine 6G

A silicon-based three-dimensional dosimeter can be formed in a free shape without a container and deformed because of its flexibility. Several studies have focused on enhancing its radiological characteristics and assessing its applicability as a quality assurance tool for image-guided and adaptive radiation therapy, considering motion and deformation. Here, we applied a fluorescence probe (dihydrorhodamine 6G, DHR6G) to a silicon elastomer as a new radiosensitive compound that converts nonfluorescent into fluorescent dyes using irradiation, and its fluorescence intensity increases linearly with the absorbed dose. In this study, we demonstrated a cost-effective synthesis method and optimized the composition conditions. The results showed that the DHR6G-SE prepared from 2.2 × 10−3 wt% DHR6G, 0.024 wt% pyridine, and a silicone elastomer (SE) (SILPOT TM 184, base/curing agent = 10/1) exhibited a linear increase in fluorescence with radiation exposure within a dose range of 0–8 Gy and a highly stable sensitivity for as long as 64 h. To demonstrate its container-less characteristics, the possibility of dosimetry for low-energy X-rays using DHR6G-SE was investigated.

Intra-Operative Radiotherapy (IORT) in Breast Conserving Therapy in Early-Stage Breast Cancer and DCIS

Initial breast intra-operative radiotherapy (IORT) results in clinical trials were encouraging though with longer follow up, increased local recurrences have been reported compared with whole breast radiation or other partial breast radiation including accelerated partial breast irradiation (APBI) methods. The goal of the study is to report our prospective single institution IORT breast study outcomes of local recurrence (LR) including true recurrence and breast elsewhere failures, breast cancer specific survival (BCSS), and overall survival (OS) with low energy x-ray IORT in early-stage breast cancer or ductal carcinoma in situ. A total of 480 patients with early-stage breast cancer or DCIS were prospectively enrolled in an IRB approved single institution trial and treated with low energy X-ray IORT 20 Gy at time of breast-conserving surgery. Eligibility criteria included ≥ 45 years of age with unifocal tumors < 3 cm deemed candidates for partial mastectomy. Supplemental external beam radiation was recommended for patients with high-risk surgical pathology including multifocal disease, positive nodes, close margins < 2 mm, or lymphovascular invasion. Ipsilateral breast tumor recurrences were classified as true recurrence versus elsewhere failure by location and histology: same/different quadrant and similar/different histology. Kaplan-Meier methods were used to estimate survival probabilities across time. Median age of enrolled patients was 64 years with the majority of patients having favorable phenotype with 94% ER+ and 93% Her-2 - disease. 110 patients (23%) had supplemental EBRT delivered; 103 to the whole breast and 7 to the breast and regional nodes. At a median follow up of 73 months (range 17 - 131 months), there were 23 (4.8%) ipsilateral breast tumor recurrences, of which 9 were true recurrences (1.9%) and 14 elsewhere failures (2.9%). One patient with true recurrence and 3 patients with elsewhere breast failures synchronously presented with clinical or radiographic regional node involvement. Seven patient developed contralateral breast cancer and 8 patients developed distant metastases during the follow-up period. There were 2 breast cancer related deaths. At 6-years, overall survival rate was 96.8% and breast cancer specific survival was 98.7%. Our study outcomes reflect similar outcomes as other reported IORT studies with electron or low energy X-ray in breast cancer, with higher risk of local failure than historical whole breast and other partial breast radiation techniques. This supports current radiation society guidelines for IORT monotherapy for breast cancer to be optimally considered in the context of prospective clinical trials.

A Phase II Trial of Intraoperative Radiotherapy after Surgical Resection of Brain Metastases: Feasibility and Efficacy NCT04847284

Intraoperative radiation therapy (IORT) is an alternative to local radiation therapy for brain metastases, reducing total treatment time, and improving patient comfort, but the most effective dose is unknown. The objective of this study is to evaluate the efficacy and safety of IORT in patients with surgical excision of brain metastases at a dose of 20 Gy. This trial is a single-institution, open-label, prospective, non-randomized study for intraoperative radiotherapy immediately after resection of brain metastases. Registered in January 2021, currently ongoing, planned to enroll 25 patients with IK ≥70, brain damage newly diagnosed by MRI, without dural contact and at least 1 cm to the optic nerve, chiasm and brainstem. In the baseline visit, the General Cognitive State will be carried out: Minimum Mental State Exams. Specific cognitive study: 1- Processing speed (SYmbol digit modalities test), 2- Executive function (TMT, back and forward digit span test, phonological and semantic verbal fluency test, Stroop color-word test), 3- Verbal memory (FCSRT). Quality of life will be monitored by completing the EORTC QL-C30 and BN20 questionnaires. Intraoperative radiation therapy will be performed with a 50 kV low energy X-ray portable linear accelerator using spherical applicators ranging from 1.5 to 4 cm kV to deliver 20 Gy to the surface. During IORT a maximum dose (DMax) of 8 Gy will be allowed to the optic nerve/chiasm and brainstem structures. MRI will be performed 72 hours after IORT. Neurocognitive Test and MRI after 6 weeks and every 3 months. The primary endpoint will be local progression free survival (PFS). Secondary endpoints will be overall survival, time to save cancer therapy, cognitive performance and quality of life, as well as IORT-related neurotoxicity complications will be evaluated according to the scale of the CTACAE version 4. The analysis of the median local progression free survival, overall survival will be analyzed using the Kaplan-Meier curve (long range test). All results will be considered statistically significant with a p value < 0.05. The statistical analysis will be carried out with statistical software. The trial is open and ongoing to recruitment; we have included 7 patients. The 85.7% were male, mean age was 61.4 years range (43-74). The 57.1% were lung cancer metastases. For now, no tumor recurrence or neurocognitive complications have been observed and then once you have the results ready, we will publish them. The limited current literature on the use of IORT in brain metastases appears to show efficacy and safety, but the most effective dose is unknown as well as whether it is as effective as other radiotherapy alternatives. Our study is ongoing and needs to be completed and evaluated with more follow-up in order to reach definitive conclusions.

X-ray spectroscopy with a photon-counting SiPM-based scintillation detector

A new low-energy X-ray detector was built and operated, using a plastic scintillator coupled to a large area SiPM.The signal is amplified with a low-noise, high gain, custom circuit providing excellent photon-counting capabilities and allowing a quasi-digital measurement.The detector was tested using X-rays coming from molybdenum K lines (17.4 and 19.6 keV), and an energy resolution of 28% is obtained with 20 photoelectrons per X-ray photon on average.

Major complications after intraoperative radiotherapy with low-energy x-rays in early breast cancer.

To describe and analyze major local complications after intraoperative radiotherapy (IORT) with low-energy x‑rays during breast-conserving surgery (BCS) in early breast cancer. Ten women out of 408 who were treated with IORT between 2002 and 2017 and subsequently developed asevere local complication requiring surgical intervention were retrospectively identified and analyzed. Demographic, clinical, and surgical parameters as well as complication characteristics and treatment methods were evaluated. At initial presentation, eight patients (80%) showed redness, six (60%) seroma, six (60%) wound infection, six (60%) suture dehiscence, and four (40%) induration of the former surgical area. Hematoma and necrosis were observed in one case (10%) each. Time interval until appearance of the first symptoms ranged from directly postoperative until 15years postoperatively (median 3.1months). Initial treatment modalities comprised antibiotic therapy (n = 8/80%) and transcutaneous aspiration of seroma (n = 3/30%). In the majority of patients, smaller surgical interventions (excision of anecrotic area/fistula [n = 6/60%] or secondary suture [n = 5/50%]) were sufficient to overcome the complication, yet larger interventions such as complex flap surgery and mastectomy were necessary in one patient each. IORT is an efficient and safe treatment method as < 2.5% of all IORT patients experienced major local complications. However, it seems to pose the risk of causing severe local complications that may require lengthy and burdensome treatment. Thorough preoperative counseling, implementation of recommended intraoperative precautions, and high vigilance for first symptoms of complications during follow-up appointments are necessary measures.

Thermal Instability of Gold Thin Films

The disintegration of a continuous metallic thin film leads to the formation of isolated islands, which can be used for the preparation of plasmonic structures. The transformation mechanism is driven by a thermally accelerated diffusion that leads to the minimalization of surface free energy in the system. In this paper, we report the results of our study on the disintegration of gold thin film and the formation of nanoislands on silicon substrates, both pure and with native silicon dioxide film. To study the processes leading to the formation of gold nanostructures and to investigate the effect of the oxide layer on silicon diffusion, metallic film with a thickness of 3 nm was deposited by molecular beam epitaxy (MBE) technique on both pure and oxidized silicon substrates. Transformation of the thin film was observed by low-energy electron microscopy (LEEM) and a scanning electron microscope (SEM), while the nanostructures formed were observed by atomic force microscope (AFM) method. Structural investigations were performed by low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS) methods. Our experiments confirmed a strong correlation between the formation of nanoislands and the presence of native oxide on silicon substrates.

低エネルギーX線によるタマネギおよびジャガイモ発芽防止のための効果的照射方法

The sprout inhibition of onion and potato by low energy X-rays was investigated using a 160 kV X-ray irradiation system to determine optimal irradiation conditions. The sprouting of onion was effectively suppressed by irradiating 20 Gy at a depth of 3.2 mm from root side for small onion and at 8.0 mm depth for large onion, respectively. For potato, double-sided irradiation was necessary to irradiate the entire potato because the buds were distributed throughout the entire potato. Irradiation on double-sided at a depth of 8.0 mm with 50 Gy (60 Gy at 5.4 mm) effectively inhibited the sprouting. The throughput calculated to be 80.9 kg/h for large onion, 34.1 kg/h for small onion, and 9.9 kg/h for potato at a distance of 350 mm from the focal point of source. Dose uniformity (Dmax at surface/Dmin at 8.0 mm depth) of potato in case of double-sided irradiation was improved from 3.6 (182 Gy/50 Gy) to 1.2 (58 Gy/50 Gy) by using an aluminum 1.0 mm filter (F1) to cut off low energy X-rays, whereas the throughput capacity decreased from 9.9 kg/h to 7.4 kg/h.

Gain measurements on NLGAD detectors

In the last few years, Low Gain Avalanche Detectors (LGAD) have demonstrated their outstanding performance when detecting high-energy charged particles. However, due to the difference in the multiplication mechanism for holes and electrons, the detection performance for low penetrating particles (e.g low-energy protons or soft x-rays) is significantly reduced. A novel design of an LGAD detector, the NLGAD, was designed and fabricated at CNM to overcome this drawback. A qualitative description of the NLGAD concept is presented in this work, along with gain response measurements of the first prototypes under visible light of 660 nm and 15 keV x-rays. Additionally, a review of the gain response under visible light of 404 nm and IR light of 1064 nm, previously studied, is also evaluated in this work. The results demonstrate that the NLGAD concept has the potential to detect low penetrating particles.

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

A multiscale Monte Carlo simulation of irradiating a typical-size apple by low-energy X-rays and electron beams

Irradiation of foods and fruits by ionizing radiation effectively eliminates pathogenic microorganisms primarily present on the surface. Recently, much attention has been paid to the use of low-energy X-rays and electron beams for food irradiation. Dosimetric investigation of foods with complex shapes is experimentally challenging. In this study, a multiscale Monte Carlo simulation was performed to compare the dose distributions of low-energy X-rays and electrons in a typical-size apple as well as to calculate the DNA damages induced by secondary electrons in a bacterial cell model. Several energies up to 500 keV and tube voltages up to 200 kV were considered for incident electrons and X-rays, respectively. The results indicate that on a microscopic scale, the yields of single- and double-stranded DNA breaks induced by X-rays and electrons of different energies are nearly identical. In a macroscopic scale, a two-sided electron beam configuration plus a 90-degree rotation of the apple (or the beam) provides an appropriate dose uniformity on the apple surface up to a depth of 40 μm. In the case of low-energy X-rays, apple rotation is not required when a two-sided irradiation is applied. Generally, X-rays are superior to electrons for the surface treatment of apples due to their lower dose uniformity ratios on the surface.

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.

INTRAMET: Results of a prospective, single-arm, open-label phase II trial of intraoperative radiotherapy after resection of brain metastases.

2031 Background: Brain metastases (BM) occur in about 10-20% of all cancer patients during the course of their disease. The current standard of care for lesions that cause mass effects is neurosurgical resection followed by adjuvant radiotherapy of the resection cavity. We here report efficacy data of the INTRAMET trial (NCT03226483), which tested intraoperative radiation therapy (IORT) using a high-dose, single fraction to the tumor bed. Methods: Patients ≥18 years and Karnofsky (KPS) ≥50 with suspected BM were included. A frozen-section confirmed metastasis and technically applicable IORT were mandatory. Exclusion criteria were surgical or MRI contraindications, meningeal infiltration, or IORT Dmax doses exceeding 8 Gy at risk structures. IORT was performed after tumor resection in the operating room with a mobile low energy X-ray device emitting a spherical radiation field with a sharp dose gradient. A dose of 30Gy was prescribed to the surface of the resection cavity. The primary endpoint was cumulative local control rate (LCR). Secondary endpoints were incidence of other (distant) BM (RCR), overall survival (OS), time to the next systemic treatment and adverse event rates (AE). Results: In total, 35 of the originally 50 planned patients were recruited. After a pre-specified interim analysis, the study was prematurely halted due to good safety and outcomes profiles. 54.3% were men, the mean age was 64 (45-85) years. The mean follow-up was 25.7 (0.8-64.5) month. At the time of this report, 51.4% of patients were alive. 68.6% primary histologies corresponded to lung primaries. The LCR was 94.3% (95% CI 82.9-98.8%) and RCR was 57.1% (95% CI 40.7-72.4%,). 8.6% patients or lesions developed out of field leptomeningeal progression. The mean OS was 37.4 months (95% CI 28.9-46.9). For those patients undergoing salvage whole brain RT (WBRT), the median initiation time was 147 (20-601) days with a significant survival benefit for those not requiring WBRT (p = 0.027). No significant survival differences were identified according to primary histology (p = 0.618), immunotherapy (p = 0.928), seizures at baseline (p = 0.169), KPS (p = 0.056) or radionecrosis appearance (p = 0.214). Mean time to next systemic treatment was 45.0 (95% CI 35.1-54.8) days. No G4-5 AE related to IORT occurred. The overall radionecrosis (RN) rate was 20% (n = 5 G1, n = 1 G2, n = 1 G3). No risk factors could be associated to RN. Post-surgical seizures were present in 28.6% patients, with eloquent localizations as the only predictive factor (p = 0.008). Conclusions: IORT for resected BM yields excellent local control rates and has a toxicity profile similar to those reported in post-operative SRS trials. By easing a prompt initiation of subsequent systemic treatments, IORT might shorten the overall treatment courses of many cancer patients. Clinical trial information: NCT03226483 .

X-ray imaging with Micromegas detectors with optical readout

In the last years, optical readout of Micromegas gaseous detectors has been achieved by implementing a Micromegas detector on a glass anode coupled to a CMOS camera. Effective X-ray radiography was demonstrated using integrated imaging approach. High granularity values have been reached for low-energy X-rays from radioactive sources and X-ray generators.Detector characterization with X-ray radiography has led to two applications: neutron imaging for non-destructive examination of highly gamma-ray emitting objects and beta imaging for the single cell activity tagging in the field of oncology drug studies.First measurements investigating the achievable spatial resolution of the glass Micromegas detector at the SOLEIL synchrotron facility with a high-intensity and flat irradiation field will be shown in this article.

Hybrid imaging of prompt x-rays and induced positrons using a pinhole gamma camera during and after irradiation of protons

Objective. Prompt x-ray imaging using a low-energy x-ray camera is a promising method for observing a proton beam’s shape from outside the subject. Furthermore, imaging of positrons produced by nuclear reactions with protons is a possible method for observing the beam shape. However, it has not been possible to measure these two types of images with a single imaging system due to the limited imaging capability of existing systems. Imaging of both prompt x-rays and the distribution of positrons may compensate for the shortcomings of each method. Approach. We conducted imaging of the prompt x-ray using a pinhole x-ray camera during irradiation with protons in list mode. Then, after irradiation with protons, imaging of annihilation radiations from the produced positrons was conducted using the same pinhole x-ray camera in list mode. After this imaging, list-mode data were sorted to obtain prompt x-ray images and positron images. Main results. With the proposed procedure, we could measure both prompt x-ray images and induced positron images with a single irradiation by a proton beam. From the prompt x-ray images, ranges and widths of the proton beams could be estimated. The distributions of positrons were slightly wider than those of the prompt x-rays. From the time sequential positron images, we could derive the time activity curves of the produced positrons. Significance. Hybrid imaging of prompt x-rays and induced positrons using a pinhole x-ray camera was achieved. The proposed procedure would be useful for measuring prompt x-ray images during irradiation to estimate the beam structures as well as for measuring the induced positron images after irradiation to estimate the distributions and time activity curves of the induced positrons.

Observation of Histone H2AX Phosphorylation by Radiation-Induced Bystander Response Using Titanium Characteristic X-ray Microbeam.

Radiation-induced bystander response (RIBR) is a response induced in non-irradiated cells that receive bystander signals from directly irradiated cells. X-ray microbeams are useful tools for elucidating the mechanisms underlying RIBR. However, previous X-ray microbeams used low-energy soft X-rays with higher biological effects, such as aluminum characteristic X-rays, and the difference from conventional X-rays and γ-rays has often been discussed. The microbeam X-ray cell irradiation system at the Central Research Institute of Electric Power Industry has been upgraded to generate higher energy titanium characteristic X-rays (TiK X-rays), which have a longer penetration distance sufficient to irradiate 3D cultured tissues. Using this system, we irradiated the nuclei of HeLa cells with high precision and found that the pan-nuclear induction of phosphorylated histone H2AX on serine 139 (γ-H2AX) in the non-irradiated cells increased 180 and 360 min after irradiation. We established a new method to quantitatively evaluate bystander cells, using the fluorescence intensity of γ-H2AX as an indicator. The percentage of bystander cells increased significantly to 23.2% ± 3.2% and 29.3% ± 3.5% at 180 and 360 min after irradiation, respectively. Our irradiation system and the obtained results may be useful for studies of cell competition as well as non-targeted effects.

SSRMP Recommendations No 9: Reference dosimetry in low and medium energy x-ray beams

The SSRMP recommendations on reference dosimetry in kilovolt beams as used in radiation therapy were revised to establish current practice in Switzerland.The recommendations specify the dosimetry formalism, reference class dosimeter systems and conditions used for the calibration of low and medium energy x-ray beams. Practical guidance is provided on the determination of the beam quality specifier and all corrections required for converting instrument readings to absorbed dose to water. Guidance is also provided on the determination of relative dose under non-reference conditions and on the cross calibration of instruments.The effect of lack of electron equilibrium and influence of contaminant electrons when using thin window plane parallel chambers at x-ray tube potentials higher than 50kV is elaborated in an appendix. In Switzerland the calibration of the reference system used for dosimetry is regulated by law. METAS and IRA are the authorities providing this calibration service to the radiotherapy departments. The last appendix of these recommendations summarise this calibration chain.

Soft X-ray spectro-ptychography of boron nitride nanobamboos, carbon nanotubes and permalloy nanorods.

Spectro-ptychography offers improved spatial resolution and additional phase spectral information relative to that provided by scanning transmission X-ray microscopes. However, carrying out ptychography at the lower range of soft X-ray energies (e.g. below 200 eV to 600 eV) on samples with weakly scattering signals can be challenging. Here, results of soft X-ray spectro-ptychography at energies as low as 180 eV are presented, and its capabilities are illustrated with results from permalloy nanorods (Fe 2p), carbon nanotubes (C 1s) and boron nitride bamboo nanostructures (B 1s, N 1s). The optimization of low-energy X-ray spectro-ptychography is described and important challenges associated with measurement approaches, reconstruction algorithms and their effects on the reconstructed images are discussed. A method for evaluating the increase in radiation dose when using overlapping sampling is presented.

Relationship between Internal Stress Distribution and Microstructure in a Suspension-Sprayed Thermal Barrier Coating with a Columnar Structure

The suspension plasma spray (SPS) method is expected to become a novel coating method because it can achieve various microstructures using a suspension with submicron spray particles. Thermal barrier coatings (TBCs) with a columnar structure, which might achieve high strain tolerance, can be obtained using the SPS technique. This study evaluated the internal stress distribution of the suspension-plasma-sprayed thermal barrier coating (SPS-TBC) with different columnar structures using hybrid measurement using high-energy synchrotron X-ray diffraction analysis and laboratory low-energy X-rays. The relationship between the microstructure and the internal stress distribution of the SPS-TBC was discussed on the basis of the experimental results. In addition, the in-plane internal stress was decreased by decreasing the column diameter. The thin columnar microstructure of the SPS-TBC has superior strain tolerance. The internal stresses in the SPS-TBC are periodic decrements caused by stress relaxation in porous layers in its column.

PO-2206 Radiopathological consequences of low energy X-rays overexposures: a dose effect study

PO-2206 Radiopathological consequences of low energy X-rays overexposures: a dose effect study