Radiochromic Films for the Two-Dimensional Dose Distribution Assessment

Reading of gafchromic EBT-3 film using an overhead scanner

Gafchromic film, a commercially available radiochromic film, has been developed and widely used as an effective tool for radiation dose verification and quality assurance in radiotherapy. However, the orientation effect in scanning a film remains a concern for practical application in beam profile monitoring. To resolve this issue, the authors introduced a novel method using an overhead scanner (OHS) coupled with a tracing light board instead of a conventional flatbed scanner (FBS) to read Gafchromic EBT3 films. We investigated the orientation effect of the EBT3 film with a regular hexagonal shape after irradiation with 5 Gy x-rays (160 kV, 6.3 mA) and compared the digitized images acquired using a commercially available OHS (CZUR Aura) and a conventional FBS (EPSON GT-X980). As a result, RGB color intensities acquired from the OHS showed significantly lower orientation effect of the color intensities of RGB components than those from FBS. This finding indicates the high potential of the proposed method for achieving more precise two-dimensional dosimetry. Further studies are required to confirm the effectiveness of this method under different irradiation conditions over a wider dose range.

Post-Irradiation Behavior of Colored PVA-Based Films Containing Ag Nanoparticles as Radiation Detectors/Exposure Indicators

Ionizing radiation covers a broad spectrum of applications. Since radioactive/radiation pollution is directly related to radiation risk, radiation levels should be strictly controlled. Different detection methods can be applied for radiation registration and monitoring. In this paper, radiation-induced variations in the optical properties of silver-enriched PVA-based hydrogel films with and without azo dye (Toluidine blue O, TBO, and Methyl red, MR) additives were investigated, and the feasibility of these free-standing films to serve as radiation detectors/exposure indicators was assessed. AgNO3 admixed with PVA gel was used as a source for the radiation-induced synthesis of silver nanoparticles (AgNPs) in irradiated gel films. Three types of sensors were prepared: silver-enriched PVA films containing a small amount of glycerol (AgPVAGly); silver-enriched PVA films with toluidine blue adducts (AgPVAGlyTBO); and silver-enriched PVA films with methyl red additives (AgPVAGlyMR). The selection of TBO and MR was based on their sensitivity to irradiation. The irradiation of the samples was performed in TrueBeam2.1 (VARIAN) using 6 MeV photons. Different doses up to 10 Gy were delivered to the films. The sensitivity of the films was assessed by analyzing the characteristic UV-Vis absorbance peaks on the same day as irradiation and 7, 30, 45, 90, and 180 days after irradiation. It was found that the addition of azo dyes led to an enhanced radiation sensitivity of the AgNPs containing films (0.6 Gy-1 for AgPVAGlyTBO and 0.4 Gy-1 for AgPVAGlyMR) irradiated with <2 Gy doses, indicating their applicability as low-dose exposure indicators. The irradiated films were less sensitive to higher doses. Almost no dose fading was detected between the 7th and 45th day after irradiation. Based on the obtained results, competing AgNP formation and color-bleaching effects in the AgPVAGly films with dye additives are discussed.

Comparative study on measurements of radiochromic films using portable colorimeters

The recently proposed method for on-site radiation dosimetry by a combination of radiochromic film and portable colorimeter was tested for six combinations of two popular Gafchromic films (EBT3 and EBT-XD) and three commercially available portable colorimeters (nix pro2, nix spectro2 and Spectro1 Pro; abbreviated to "NixP", "NixS" and "SpoP", respectively). EBT3 and EBT-XD were irradiated with X-rays (160 kV, 6.3 mA) up to 40 Gy and 80 Gy, respectively, and the radiation-induced color levels of RGB and CMYK components were measured with the three colorimeters. Angle dependence was examined by reading at 15° intervals. As a result, it was judged that all combinations would work effectively under certain irradiation conditions. NixP and NixS were applicable to a wider dose range for both films, while SpoP fit a lower dose range. On the other hand, SpoP showed an advantageous feature of no angular dependence in reading films, while NixP and NixS showed significant angle-dependent changes. These differences are considered to be attributable to the different geometries of LED light emission, which came from all directions (360°) in SpoP, 4 directions in NixP, and 8 directions in NixS. These findings are expected to expand the applicability of the novel method to various occasions of on-site dosimetry.

Optimized production of 67Cu based on cross section measurements of 67Cu and 64Cu using an 18 MeV medical cyclotron

RadioNuclide Therapy (RNT) in nuclear medicine is a cancer treatment based on the administration of radioactive substances that specifically target cancer cells in the patient. These radiopharmaceuticals consist of tumor-targeting vectors labeled with β^-, α, or Auger electron-emitting radionuclides. In this framework, ⁶⁷Cu is receiving increasing interest as it provides β^--particles accompanied by low-energy γ radiation. The latter allows to perform Single Photon Emission Tomography (SPECT) imaging for detecting the radiotracer distribution for an optimized treatment plan and follow-up. Furthermore, ⁶⁷Cu could be used as therapeutic partner of the β⁺-emitters ⁶¹Cu and ⁶⁴Cu, both currently under study for Positron Emission Tomography (PET) imaging, paving the way to the concept of theranostics. The major barrier to a wider use of ⁶⁷Cu-based radiopharmaceutical is its lack of availability in quantities and qualities suitable for clinical applications. A possible but challenging solution is the proton irradiation of enriched ⁷⁰Zn targets, using medical cyclotrons equipped with a solid target station. This route was investigated at the Bern medical cyclotron, where an 18 MeV cyclotron is in operation together with a solid target station and a 6-m-long beam transfer line. The cross section of the involved nuclear reactions were accurately measured to optimize the production yield and the radionuclidic purity. Several production tests were performed to confirm the obtained results.

Innovative Photonic Sensors for Safety and Security, Part III: Environment, Agriculture and Soil Monitoring

In order to complete this set of three companion papers, in this last, we focus our attention on environmental monitoring by taking advantage of photonic technologies. After reporting on some configurations useful for high precision agriculture, we explore the problems connected with soil water content measurement and landslide early warning. Then, we concentrate on a new generation of seismic sensors useful in both terrestrial and under water contests. Finally, we discuss a number of optical fiber sensors for use in radiation environments.

Cross-section measurement for an optimized 61Cu production at an 18 MeV medical cyclotron from natural Zn and enriched 64Zn solid targets

The availability of novel medical radionuclides is a key point in the development of personalised nuclear medicine. In particular, copper radioisotopes are attracting considerable interest as they can be used to label various molecules of medical interest, such as proteins and peptides, and offer two of the most promising true theranostic pairs, namely ⁶¹Cu/⁶⁷Cu and ⁶⁴Cu/⁶⁷Cu. Although ⁶⁴Cu (t_1/2 = 12.7006 h, β⁺: 17.6%, β^-: 38.5%) is nowadays the most commonly used as a diagnostic radionuclide, ⁶¹Cu (t_1/2 = 3.339 h, β⁺: 61%) features more favourable nuclear properties, such as a higher positron decay fraction and the absence of β^- emissions. To date, the production of ⁶¹Cu has been carried out irradiating highly enriched ⁶¹Ni targets with a low energy proton beam. However, the use of the very expensive ⁶¹Ni targets requires an efficient recovery of the target material and makes this method quite inconvenient. Another promising production route is the proton irradiation of natural Zn or enriched ⁶⁴Zn targets, exploiting the (p,α) nuclear reaction. Along this line, a research program is ongoing at the Bern medical cyclotron, equipped with an external beam transfer line and a solid target station. In this paper, we report on cross-section measurements of the ⁶⁴Zn(p,α)⁶¹Cu nuclear reaction using natural Zn and enriched ⁶⁴Zn material, which served as the basis to perform optimized ⁶¹Cu production tests with solid targets.

A Review of PRESAGE Radiochromic Polymer and the Compositions for Application in Radiotherapy Dosimetry

Recent advances in radiotherapy technology and techniques have allowed a highly conformal radiation to be delivered to the tumour target inside the body for cancer treatment. A three-dimensional (3D) dosimetry system is required to verify the accuracy of the complex treatment delivery. A 3D dosimeter based on the radiochromic response of a polymer towards ionising radiation has been introduced as the PRESAGE dosimeter. The polyurethane dosimeter matrix is combined with a leuco-dye and a free radical initiator, whose colour changes in proportion to the radiation dose. In the previous decade, PRESAGE gained improvement and enhancement as a 3D dosimeter. Notably, PRESAGE overcomes the limitations of its predecessors, the Fricke gel and the polymer gel dosimeters, which are challenging to fabricate and read out, sensitive to oxygen, and sensitive to diffusion. This article aims to review the characteristics of the radiochromic dosimeter and its clinical applications. The formulation of PRESAGE shows a delicate balance between the number of radical initiators, metal compounds, and catalysts to achieve stability, optimal sensitivity, and water equivalency. The applications of PRESAGE in advanced radiotherapy treatment verifications are also discussed.

An Innovative Real-Time Dosimeter for Radiation Hardness Assurance Tests

The study of the effects of the radiation dose on devices and materials is a topic of high interest in several fields, including radiobiology, space missions, microelectronics, and high energy physics. In this paper, a new method, based on radiochromic film dosimetry, is proposed for real-time dose assessment in radiation hardness assurance tests. This method allows for correlating the radiation dose at which devices are exposed to the radiation effects (malfunctioning and/or breakdown). In previous studies, it has already been demonstrated that a system, based on optical fibers and a spectrometer, allows for the real-time dose assessment of radiochromic films. The current study not only validates our previous results, but shows that it is possible to apply the new method to an actual radiation environment for the real-time measurement of the dose delivered to a device in radiation hardness assurance tests. This new dosimeter can be used in different radiation environments for a wide dose range, from a few Gy to a few MGy. This high sensitivity can be reached by changing the radiochromic film type and/or the parameters used for the analysis.