Objective.In this work, we aim to propose an accurate and robust spectrum estimation method by synergistically combining x-ray imaging physics with a convolutional neural network (CNN).Approach.The approach relies on transmission measurements, and the estimated spectrum is formulated as a convolutional summation of a few model spectra generated using Monte Carlo simulation. The difference between the actual and estimated projections is utilized as the loss function to train the network. We contrasted this approach with the weighted sums of model spectra approach previously proposed. Comprehensive studies were performed to demonstrate the robustness and accuracy of the proposed approach in various scenarios.Main results.The results show the desirable accuracy of the CNN-based method for spectrum estimation. The ME and NRMSE were -0.021 keV and 3.04% for 80 kVp, and 0.006 keV and 4.44% for 100 kVp, superior to the previous approach. The robustness test and experimental study also demonstrated superior performances. The CNN-based approach yielded remarkably consistent results in phantoms with various material combinations, and the CNN-based approach was robust concerning spectrum generators and calibration phantoms.Significance. We proposed a method for estimating the real spectrum by integrating a deep learning model with real imaging physics. The results demonstrated that this method was accurate and robust in estimating the spectrum, and it is potentially helpful for broad x-ray imaging tasks.

Knowledge of the photon spectrum emitted from an x-ray tube is frequently needed in imaging and dosimetry contexts. As the spectrum characteristics are influenced by several parameters and routine measurement of a spectrum is often impractical, a variety of software programs have been developed over the decades for convenient calculations. SpekPy is a state-of-the-art software package containing several spectrum models, and was created to estimate photon spectra originating from x-ray tubes using a small set of input parameters (e.g., anode material, anode angle, tube potential, filtration, etc.). SpekPy is distributed as a Python toolkit and is available free of charge. The toolkit does, however, lack a graphical user interface and a user is required to write a Python script to make use of it. In this work this limitation is addressed by introducing a web application called SpekPy Web: a graphical user interface together with an application programmable interface (API). These developments both make the SpekPy spectrum models accessible to a broader set of users and increases the ease of use for existing users. SpekPy Web is hosted at: https://spekpy.smile.ki.se. The functionality of the software is demonstrated, using its API, by estimating first half-value layers (HVLs) for 15 standard beam qualities from the International Bureau of Weights and Measures (BIPM). The estimated HVLs were found to all be within 3.5% agreement when compared to experimental values, with an average calculation time of 2.5 s per spectrum. half-value-layer, software, x-ray spectrum.

Ultrashort pulse laser processing can result in the secondary generation of unwanted X-rays if a critical laser irradiance of about 1013 W cm-2 is exceeded. Spectral X-ray emissions were investigated during the processing of tungsten and steel using three complementary spectrometers (based on CdTe and silicon drift detectors) simultaneously for the identification of a worst-case spectral scenario. Therefore, maximum X-ray photon energies were determined, and corresponding dose equivalent rates were calculated. An ultrashort pulse laser workstation with a pulse duration of 274 fs, a center wavelength of 1030 nm, pulse repetition rates between 50 kHz and 200 kHz, and a Gaussian laser beam focused to a spot diameter of 33 μm was employed in a single pulse and burst laser operation mode. Different combinations of laser pulse energy and repetition rate were utilized, keeping the average laser power constant close to the maximum power of 20 W. Peak irradiances I0 ranging from 7.3 × 1013 W cm-2 up to 3.0 × 1014 W cm-2 were used. The X-ray dose equivalent rate increases for lower repetition rates and higher pulse energy if a constant average power is used. Laser processing with burst mode significantly increases the dose rates and the X-ray photon energies. A maximum X-ray photon energy of about 40 keV was observed for burst mode processing of tungsten with a repetition rate of 50 kHz and a peak irradiance of 3 × 1014 W cm-2.

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.

The potential of the pyroelectric crystal surface has been estimated using experimental data. The temperature of the pyroelectric crystal, the electron current from the crystal surface to the target, and the X-ray spectrum were simultaneously measured. The potential calculated from the temperature and the electron current was compared with the experimental endpoint energy of the X-ray spectrum. The calculated potential reasonably agreed with the experimental endpoint energy.

Interactions between ultrashort laser pulses with intensities larger than 1013 W/cm2 and solids during material processing can lead to the emission of X-rays with photon energies above 5 keV, causing radiation hazards to operators. A framework for inspecting X-ray emission hazards during laser material processing has yet to be developed. One requirement for conducting radiation protection inspections is using a reference scenario, i.e., laser settings and process parameters that will lead to an almost constant and high level of X-ray emissions. To study the feasibility of setting up a reference scenario in practice, ambient dose rates and photon energies were measured using traceable measurement equipment in an industrial setting at SCHOTT AG. Ultrashort pulsed (USP) lasers with a maximum average power of 220 W provided the opportunity to measure X-ray emissions at laser peak intensities of up to 3.3 × 1015 W/cm2 at pulse durations of ~1 ps. The results indicate that increasing the laser peak intensity is insufficient to generate high dose rates. The investigations were affected by various constraints which prevented measuring high ambient dose rates. In this work, a list of issues which may be encountered when performing measurements at USP-laser machines in industrial settings is identified.

OBJECTIVE: The objective of this article is to introduce a simplified and swift method to satisfactorily estimate the half-value layers (HVL), quarter-value layer (QVL), and tenth-value layer (TVL) from the x-ray spectra emitted by any diagnostic radiology or kV radiotherapy x-ray tubes.
METHODS: A CdTe x-ray and Gamma detector (X-123 CdTe, AmpTek Inc.) is used to measure the x-ray spectra at four different x-ray energies (low, mid, high energy x-rays) with different external filtering. The software \"SpekCalc GUI\" (Developed in McGill University, Montreal, Canada) is also used to obtain the simulated x-ray spectra. Both measured and simulated spectra are used to compute the HVL thicknesses of Aluminum by a mathematical method presented in this article. Next, the HVL thicknesses for corresponding tube potentials are also measured by calibrated ionization chamber and varying thicknesses of aluminum plates. Finally, the computed and measured HVL, QVL, and TVL thicknesses are compared to evaluate the efficacy of the presented method.
RESULTS: The results show acceptable concordance between computed and measured quantities. The disagreement rates between measured HVL and the values derived mathematically from the x-ray spectra are 10 to 90 micrometers of Aluminum at tube potentials of 31 kV to 120 kV. As it is shown, a negligible discrepancy is observed between the analytical estimation and the experimental assessments.
CONCLUSIONS: The HVL is an essential component in the evaluation of the quality of an x-ray beam. However, its measurement could occasionally be challenging, time-consuming, or uncertain due to some technical difficulties. Although the scope of this study is not to undermine the value of conventional and widely accepted practice to determine the HVL thickness, the introduced method provides the fast, more convenient, and comparably reliable technique to estimate the HVL, QVL, and TVL by employing the given x-ray spectrum.

Ultrashort pulse laser machining is subject to increase the processing speeds by scaling average power and pulse repetition rate, accompanied with higher dose rates of X-ray emission generated during laser-matter interaction. In particular, the X-ray energy range below 10 keV is rarely studied in a quantitative approach. We present measurements with a novel calibrated X-ray detector in the detection range of 2-20 keV and show the dependence of X-ray radiation dose rates and the spectral emissions for different laser parameters from frequently used metals, alloys, and ceramics for ultrafast laser machining. Our investigations include the dose rate dependence on various laser parameters available in ultrafast laser laboratories as well as on industrial laser systems. The measured X-ray dose rates for high repetition rate lasers with different materials definitely exceed the legal limitations in the absence of radiation shielding.

Lab-based X-ray computed tomography (XCT) systems use X-ray sources that emit a polychromatic X-ray spectrum and detectors that do not detect all X-ray photons with the same efficiency. A consequence of using a polychromatic X-ray source is that beam hardening artefacts may be present in the reconstructed data, and the presence of such artefacts can degrade XCT image quality and affect quantitative analysis. If the product of the X-ray spectrum and the quantum detection efficiency (QDE) of the detector are known, alongside the material of the scanned object, then beam hardening artefacts can be corrected algorithmically. In this work, a method for estimating the product of the X-ray spectrum and the detector\'s QDE is offered. The method approximates the product of the X-ray spectrum and the QDE as a Bézier curve, which requires only eight fitting parameters to be estimated. It is shown experimentally and through simulation that Bézier curves can be used to accurately simulate polychromatic attenuation and hence be used to correct beam hardening artefacts. The proposed method is tested using measured attenuation data and then used to calculate a beam hardening correction for an aluminium workpiece; the beam hardening correction leads to an increase in the contrast-to-noise ratio of the XCT data by 41% and the removal of cupping artefacts. Deriving beam hardening corrections in this manner is more versatile than using conventional material-specific step wedges.

UNASSIGNED: Thanks to its lack of allergic reactions and renal toxicity, CO2 represents an alternative to iodine as a contrast medium for peripheral subtraction angiography. Since CO2 has a lower and negative contrast than iodine, postprocessing DSA and stacking are mandatory. So, it seems that higher doses than traditional iodine angiography are required. We addressed the dosimetric aspects of CO2 angiography for two different commercial DSA-apparatus.
UNASSIGNED: Two different radiological suites were analyzed by recreating the same setup on all the apparatuses: we used a PMMA slabs phantom with a MPD Barracuda dosimeter on its side to collect all radiological parameters.
UNASSIGNED: Results show that the irradiation parameters were left completely unchanged between the traditional and CO2 angiographic programs.
UNASSIGNED: This leads to thinking that these CO2 protocols do not operate on the X-ray emission, but only differ on image manipulation. The possibility of improvements by changing radiological parameters are still not explored and really promising.