Radiation Measurements最新文献

This paper presents a versatile and cost-effective system for the monitoring of X-ray exposure during dental cone beam computed tomography procedures based on silicon PIN photodiode detectors. The system, developed and implemented at the University of Pisa's School of Engineering, underwent characterization under a range of operational conditions focusing on full field-of-view 3D protocols used in adult patient examinations. This study was facilitated by the Azienda Ospedaliero Universitaria Pisana, which provided access to a Planmeca ProMax 3D Classic scanner for the research. During the investigation, photodiodes were placed both on the surface and inside an Alderson RANDO phantom head to assess the dose delivered to regions near radiation-sensitive areas such as the salivary glands, thyroid, eye lens, and laryngopharynx. The evaluation process spanned a spectrum of tube voltages, ranging from 60 to 90 kVp, and tube currents, extending up to 16 mA, to ensure a broad and thorough analysis. Furthermore, to reinforce the effectiveness of the silicon photodiodes' measurement capabilities, calibrated GR-200 A-type thermoluminescent dosimeters were positioned within the phantom head inserts to serve as a reference point. Complementing this setup, PCXMC Rotation 2.0 simulations were conducted to further the efficacy of the monitoring system, particularly tailored to the specific dental CBCT protocols being investigated. In conclusion, while the research revealed a generally consistent correlation across PCXMC simulations, photodiode readings, and thermoluminescent dosimeter measurements, it is important to note that a direct comparison was not exactly possible due to limitations in the size and positioning of the systems. Variations up to 20–35% were observed, primarily due to the different positioning of the dosimeters and the unique physical and operational traits of the different measurement methods employed. Nevertheless, the development of an affordable, easily deployable, and scalable dosimetry monitoring system may provide a substantial contribution to enhancing patient safety in dental radiology and aid in the optimization of diagnostic X-ray protocols.

This review explores current experimental methods for determining the radiation quality in ion beams. In this context, radiation quality is commonly evaluated using the averaged linear energy transfer (LET), a metric employed to assess the response of both biological and physical systems. Dose and averaged LET can be experimentally determined with passive detectors through various techniques that have seen recent improvements. Another metric related to the LET is the mean lineal energy, which is measurable using microdosimetric detectors. This review focuses on the available possibilities for evaluating the radiation quality using three microdosimeters (mini-TEPC, Silicon Telescope, and SOI Microplus), three passive luminescence detectors (based on optical, thermo-, and radiophoto-luminescence), three track-based detectors (track-etched detector, Timepix, fluorescent nuclear track detector), and a chemical detector based on alanine. A comparison of detector properties is provided along with an overview of the underlying mechanisms enabling LET assessment or measurements of the mean lineal energy with each detector type. Finally, this review summarizes the current possibilities of LET determination with respect to the needs for quality assurance in particle therapy. Areas for future research and development are suggested.

The challenge of saturation at the high dose rate employed in FLASH radiotherapy and the lack of real-time 2D and 3D dosimeters create an opportunity for the use of plastic scintillators. This study presents the development of an online dosimetric system designed for electron FLASH radiotherapy applications: an array of dosimeters, made by plastic scintillating fibers, each one coupled to an optical fiber, was evaluated as a proof-of-concept using a LINAC providing 9 MeV electrons, at the Centro Pisano Flash Radiotherapy. Signal linearity was established up to 10 Gy/pulse, with a pulse duration of $4\mu s$. We also measured the signal variation across the beam profile using different applicators (30 mm, 50 mm and 100 mm in diameters) and we developed a geometrical model that accounts for the different amount of dose absorbed by the plastic scintillating fibers and the optical fibers. By fitting this model to the data, we estimated both the inter-calibration factors of the dosimeters, as well as the intrinsic ratio (i.e. for equal irradiated volumes) of spurious light in the optical fiber respect to the scintillation, which is equal to (4.7$\pm 0.1_{stat.}\pm 1.0_{syst.}$) %.

Accurate real-time monitoring of neutron beams and distinguishing between thermal, epithermal and fast neutron components in the presence of a photon background is crucial for the effectiveness of accelerator-based boron neutron capture therapy (AB-BNCT). In this work, we propose an innovative quadruple metal–oxide–semiconductor field-effect transistor (MOSFET) device for real-time, cost-effective beam quality control; one detector is kept uncovered while the other three are covered with either a B${}_4$C, cadmium and B${}_4$C or polyethylene converter.

Individual MOSFET converter configurations were optimised via Monte Carlo simulations to maximise signal selectivity across neutron energy spectra. Results demonstrate the quad-MOSFET device’s efficacy in quantifying changes in neutron flux, underscoring its potential as a useful instrument in the AB-BNCT quality control process.

A high-performance oxygen terminated synthetic single crystal diamond (SCD) detector (4.5 × 4.5 × 0.5 mm³) is presented. The SCD detector exhibits an extremely low leakage current value of 0.29 pA/mm² with an electric field of 0.3 V/μm. The charge collection spectrum measured with a²³⁸Pu source (5.48 MeV α-particles) irradiation shows that the electron and hole charge collection efficiency (CCE) reach as high as 99.1% and 98.9%, with an energy resolution as low as 2.87% and 2.53%, respectively, compared to Si detector. The SCD detector shows excellent radiation hardness and stability under ⁶⁰Co γ-ray irradiation with a dose rate of 12.737 kGy/h at 150 V bias and is able to withstand a cumulative dose of up to at least 9.3 kGy. The detector output in current mode is linearly related to the dynamic dose rate (0.409 Gy/h-12.737 kGy/h). Similarly, the counting rate of the detector in counting mode exhibits a strong linear variation within the range of 2.6 mGy/h-1269.36 Gy/h. Our results fully indicate that our fabricated SCD detector can be potentially applied to harsh γ irradiation scenarios, which is of guiding significance on real-time dose monitoring.

The paper presents results of on-ground (pre-flight) calibrations and flight tests (cross-calibration and in situ measurements) of the new, Modified PILLE-ISS Dosimeters with reduced shielding, developed for the radiation monitoring of astronauts during their extravehicular activity (EVA) on board the International Space Station (ISS). The smaller dimensions and weight of the modified thermoluminescent dosimeter allows ergonomic and safe use during EVA, when the dosimeter kit is worn in the outer pocket of a spacesuit. The special design of the detector housing makes it possible to estimate the dose to the astronaut's skin during EVA more accurately. Both pre-flight calibration with high-energy protons and on-board cross-calibration at ISS showed that the variability of the relative sensitivities does not exceed (5–10)% for any of the Modified PILLE-ISS Dosimeters. The additional dose received by astronauts during ISS EVAs in 2023 was in the range (0.37–0.75) mGy (in water) based on the measurements. The corresponding dose rate outside ISS is consistent with the previous readings of other dosimetric equipment installed on the outer surface of space station.

In recent years, the infrared photoluminescence (PL) of feldspar has been explored for geological dating because it offers a great increase in signal intensity with increasing radiation dose. However, a comprehensive understanding of the PL emission spectra of different types of feldspar minerals remains poorly understood and the uncommonly available instruments have hindered its research. In this study, we investigated PL characteristics (e.g., emission spectra and the dependence of PL emission on irradiation dose) of single-crystal alkali and plagioclase feldspars using a commercial Raman microscope instrument configured to excite samples with 532 and 785 nm lasers. The results show that despite being sample-dependent, 2–3 PL bands peaking at ∼2.10 eV (590 nm), 1.75 eV (710 nm), and 1.43 eV (865 nm) under 532 nm laser excitation, and 0–2 peaks ranging from ∼1.44 eV (863 nm) to ∼1.34 eV (925 nm) under 785 nm laser excitation, are broadly observed. These variations in PL bands may be attributed to subtle differences in chemical composition and crystal structure among the feldspar minerals. The sensitivity of PL emission to irradiation dose varies greatly depending on feldspar types and peak positions. The PL intensities of the peaks at ∼1.43 eV (865 nm) are particularly sensitive in K-feldspar, demonstrating their potential applicability for dating applications. Additionally, solar bleaching experiments demonstrate that PL signals of these peaks can be effectively reset by 1.5 h of solar exposure. The dose-response curves obtained using 860–870 nm PL signals of K-feldspar conform to a relationship of a single saturating exponential function between the signal and irradiation dose. Furthermore, this study demonstrates that a commonly available Raman system can be utilized for PL measurements of single grains.

Radiophotoluminescence (RPL) FD-7 glass dosimeters find applications in low to high dose radiation environments. This work presents an experimental characterization of RPL glass dosimeter, irradiated with 100 kV X-ray tubes at room temperature at doses ranging from 1.3 kGy to 0.47 MGy, much higher of their common use range. In this study, a customized set-up has been developed, allowing the online investigation of the glass transmission changes with radiation, known as Radiation-Induced Attenuation (RIA), as well as the recovery and post-mortem characterizations up to 2 months after irradiation. Multi-wavelength analysis was performed, focusing on the range between 200 nm and 800 nm. At 700 nm and 800 nm, RIA increases progressively with dose up to about 5 kGy, and tends to approach saturation (2–3 dB/mm) for doses higher than 50 kGy. Higher attenuation is reported at lower wavelengths: 445-nm light transmission reduces to only about 1% of its initial value after 2 kGy. RIA recovery after irradiation was observed, up to 6% at 700 nm wavelength within 3 h from the irradiation conclusion and up to 26% 2 months after, especially at doses in the kGy range. Both online RIA and its recovery are highly dependent on the selected wavelength and on the total absorbed dose. This information is crucial for the extension of the use of these dosimeters up to high doses, complementary to the RPL signal, traditionally used alone for the determination of doses up to the Gy range.

The objective of this work was to assess the response of TLDs inserted in an anthropomorphic phantom for an OCD treatment considering the planning methodologies, dimensions of an isodose projection in a plan, detector dimensions, uncertainty of mechanical movement of the patient positioning system, dose calculation algorithms and dose rate in Gamma Knife Perfexion™ equipment. The doses to the brainstem were evaluated as well as the possibility of alopecia occurrence. Considering the dosimetry of the internal capsule region, differences seen were within the error of the method. The measured doses to the brainstem, due to the treatment of OCD, were lower than the limits considered relevant. However, for the scalp region, dose values, higher than the desirable limiting ones to determine alopecia were observed. Results showed that it is possible to establish a methodology that allows characterizing a treatment plan of OCD using TLDs.

In addition to the quality of the image, radiological protection of the patient must be considered to ensure an adequate diagnosis in dental radiology, especially in regard to those parts of the patient's body that are close to the radiation beam, such as the thyroid, salivary glands, and brain. In this work, the doses absorbed by the thyroid, salivary glands, eyes and brain of pediatric dental patients undergoing radiographic examinations are estimated using MCNP 6.2 coupled with virtual anthropomorphic phantoms, based on information from dental scenarios with a periapical X-ray unit. The absorbed doses were estimated for five- and 10-year-old male and female children. In the occlusal position, a higher absorbed dose to the thyroid was found for a five-year-old patient, whereas in the molar tube position, the brain was found to receive a higher absorbed dose for five- and 10-year-old patients. The results obtained here, expressed in terms of the absorbed dose, indicate that the beam direction and the use of different image acquisition techniques strongly influence the entrance dose values for the organs of interest in this study.