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Background: Radiation therapy using beta particles is an interesting treatment for very superficial skin lesions. Due to their low penetration in tissue and rapid dose fall‐off, beta particles can protect underlying bony structures and surrounding healthy tissue while irradiating the skin tumor. In the current work, a simple method for the fabrication of a radioactive patch for use in skin cancer therapy based on a beta‐emitting isotope is presented. Materials and methods: The beta radiation sources were Y‐90 microspheres currently used for catheter‐based radioembolization of unresectable liver tumors. The microspheres were filtered through a syringe filter to trap them on the cellulose nitrate paper of the filter and create a radioactive patch. In the current study, to avoid the need for a hot laboratory, the experiment was done using nonradioactive microspheres. An optical microscope was used to verify the distribution of the particles on the filter paper. Results: Visual evaluation of the patches showed that using the proposed method, therapeutic skin patches with a fairly uniform distribution of microspheres can be created. Conclusion: The proposed simple method may be used in creating radiotherapeutic patches using Y‐90 microspheres for radiation therapy of thin skin lesions located close to sensitive structures. [ABSTRACT FROM AUTHOR]

Nonmelanoma skin cancer (NMSC) is a major health concern due to its high incidence rate, its negative impact on the quality of life of patients as well as the associated economic burden to the healthcare system. Surgery is currently the primary treatment offered for skin cancer patients but not applicable or available in all cases. Radiation therapy (RT), with its long successful history in the management of cancer, has shown to be an effective alternative or complementary method in cutaneous oncology. Specifically, for dermatology applications, RT is very often the preferred option due to its favorable cosmetic results, besides the excellent control rate of the tumor. During the last 120 years since the introduction of treatments based on ionizing radiation, several techniques in this area have been developed. Radionuclide brachytherapy, electronic brachytherapy, X-ray therapies with kilovolt (kV) to megavolt (MV) photons and electron beam therapy are the established methods that are currently used on skin cancer patients. The purpose of this article is to overview these techniques and discuss the pros and cons of these methods in dermatology practices. Additionally, a new approach of beta RT of superficial skin tumors is discussed, which may offer exciting features in the management of NMSC. [ABSTRACT FROM AUTHOR]

Abstract Ce doped (Gd , La) 2 Si 2 O 7 (LaGPS) is a new scintillator which has high light output and is a promising candidate for high resolution radiation imaging detectors. Thus we developed a radiation imaging detector using a LaGPS plate combined with a position sensitive photomultiplier tube (PSPMT) and evaluated the performance. We found that the decay times of LaGPS were different with the types of radiations and the separations of the images of the different types of radiations were possible using pulse shape discrimination. The spatial resolution for Am-241 alpha particles (5.5 MeV) was better than 0.31 mm FWHM and the energy resolution was 11 % FWHM. The spatial resolution for Sr–Y-90 beta particles was ∼ 0.6 mm FWHM and those for Co-57 gamma photons (122 keV) and Cs-137 X-ray (∼ 35 keV) were better than 0.6 mm FWHM and ∼ 0.8 mm FWHM, respectively. The decay times for alpha particles, beta particles, and gamma photons were 143 ns, 124 ns, and 119 ns, respectively. With these different decay times, the separation of alpha particles and gamma photons or beta particles was possible using the pulse shape discrimination. We conclude that the developed LaGPS imaging detector has high resolution for all types of radiations and is also capable of the simultaneous imaging and separating the different types of radiations. [ABSTRACT FROM AUTHOR]

Abstract The effect of beta particles (β−) on the structure and adsorption properties of the synthetic MCM–41 silica with rice husk MCM–41/RH composite was investigated for the first time. Based on XRD, SEM, and zeta potential results, the energy of β–radiation was sufficient to produce a morphs composite (β–MCM–41/RH) with negative surface charge and irregular internal porous structure. The adsorption of malachite green (MG) by the β–MCM–41/RH composite was performed under different conditions of solution pH, shaking time, initial MG concentration, adsorbent dose, and temperature. Modification of the MCM–41/RH composite by radiation process enhanced its maximum uptake efficiency for MG from 29.68 to 97.11%. The pseudo-second-order model with a correlation coefficient (R 2 = 0.999) fitted well the MG adsorption kinetic. Linear and non-linear forms of the traditional isotherm models showed that Freundlich equation described well the MG adsorption data. Different statistical physics models on the basis of the grand canonical ensemble were also applied for a deeper interpretation of the MG adsorption mechanism. Based on the fitting experimental results, monolayer with two energy sites was found to be the best model in describing the MG adsorption phenomena. Through this model, the number of adsorbed MG molecules per site, the density of receptor sites, the removed amount of MG at saturation, the concentration at half saturation, and the adsorption energy were determined. The measured adsorption energies (E 1 = −18.345 and E 2 = −15.43 kJ/mol) suggested that electrostatic attraction and hydrogen bond interactions were involved in adsorption process. The parameters of thermodynamic functions including the configurational entropy, free enthalpy, and internal energy indicated that the MG adsorption onto the β–MCM–41/RH composite was exothermic and spontaneous in nature. Graphical abstract Unlabelled Image Highlights • A composite of MCM-41 with rice husk was modified by beta particles. • Adsorption properties of the radiated composite for malachite green were studied. • Modification of the composite by beta-rays enhanced its uptake efficiency for MG. • Statistical physics models were applied in evaluation of the adsorption mechanism. [ABSTRACT FROM AUTHOR]

Abstract Gd 3 (GaAl) 5 O 12 :Ce (GGAG) is a ceramic scintillator originally developed for X-ray CT, and it was also an excellent material for the development of an event-by-event-based radiation imaging detector when it was combined with a position sensitive photomultiplier (PSPMT). With the developed GGAG imaging detector, we found that the decay times for alpha particles and gamma photons were different. Also, we found that the decay times for alpha particles and beta particles were different. These characteristics are advantageous for developing an imaging detector for the simultaneous imaging of different types of radiation using pulse shape discrimination. Thus, we tested the separation of the images of the alpha particles and gamma photons using pulse shape discrimination. Also, we evaluated the separation of the alpha and beta particle images. In the pulse shape spectra, we could separate the peaks of Am-241 alpha particles and Cs-137 gamma photons with a peak-to-valley ratio (P/V) of 3.5. We obtained clearly separated images for Am-241 alpha particles and Cs-137 gamma photons using pulse shape discrimination. We could also separate the peaks of Am-241 alpha particles and Sr–Y-90 beta particles with a P/V of 1.5 in the pulse shape spectrum. We obtained separated images for Am-241 alpha particles and Sr–Y-90 beta particles using pulse shape discrimination. In addition, we could separate electrostatically collected natural alpha particles, Po-218 and Po-214, from the environmental beta particles and gamma photons using pulse shape discrimination. We conclude that the GGAG imaging detector is promising for simultaneous imaging and separating the images of different types of radiation using pulse shape discrimination. [ABSTRACT FROM AUTHOR]

Purpose: Genomic profiling of biopsied tissue is the basis for precision cancer therapy. However, biopsied materials may not contain sufficient amounts of tumor deoxyribonucleonic acid needed for the analysis. We propose a method to determine the adequacy of specimens for performing genomic profiling by quantifying their metabolic activity. Methods: We estimated the average density of tumor cells in biopsy specimens needed to successfully perform genomic analysis following the Memorial Sloan Kettering Integrated Mutation Profiling of Actionable Cancer Targets (MSK‐IMPACT) protocol from the minimum amount of deoxyribonucleonic acid needed and the volume of tissue typically used for analysis. The average 18F‐FDG uptake per cell was assessed by incubating HT‐29 adenocarcinoma tumor cells in 18F‐FDG containing solution and then measuring their activity with a scintillation well counter. Consequently, we evaluated the response of two devices around the minimum expected activities which would indicate genomic profiling adequacy of biopsy specimens obtained under 18F‐FDG PET/CT guidance. Surrogate samples obtained using 18G core needle biopsies of gels containing either 18F‐FDG‐loaded cells in the expected concentrations or the corresponding activity were measured using autoradiography and a scintillation well counter. Autoradiography was performed using a CCD‐based device with real‐time image display as well as with digital autoradiography imaging plates following a 30‐min off‐line protocol for specimen activity determination against previously established calibration. Results: Cell incubation experiments and estimates obtained from quantitative autoradiography of biopsy specimens (QABS) indicate that specimens acquired under 18F‐FDG PET/CT guidance that contained the minimum amount of cells needed for genomic profiling would have an average activity concentration in the range of about 3 to about 9 kBq/mL. When exposed to specimens with similar activity concentration, both a CCD‐based autoradiography device and a scintillation well counter produced signals with sufficient signal‐to‐background ratio for specimen genomic adequacy identification in less than 10 min, which is short enough to allow procedure guidance. Conclusion: Scintillation well counter measurements and CCD‐based autoradiography have adequate sensitivity to detect the tumor burden needed for genomic profiling during 18F‐FDG PET/CT‐guided 18G core needle biopsies of liver adenocarcinoma metastases. [ABSTRACT FROM AUTHOR]

Here the geometries that maximise detection efficiency of heterogeneous scintillators used to detect beta particles in aqueous solutions by maximising energy deposition are described. The determination of the geometry was achieved with the Monte Carlo code Geant4 using CaF 2 :Eu scintillator as a pertinent case study, and validated with experimental data using single crystal CaF 2 :Eu and heterogeneous CaF 2 :Eu scintillators. Both 2D and 3D structures composed of arrays of primitive unit cells of packed spheres were examined to find the optimal geometry to maximise detection of volumetric sources of tritium and aqueous Carbon 14 and Lead 210. The 2D structures were evaluated relative to a single crystal scintillator and results show the detection efficiency of the 2D structures is maximised when the sphere radius is c.a. 0.46x the maximum track length of the beta particle in the scintillator. Data for the 3D structures show that the efficiency is maximised when the sphere radius is minimised, but it is further shown that practical issues limit the minimum radius that can be used for transient radiological contamination monitoring. [ABSTRACT FROM AUTHOR]

Total bremsstrahlung spectral photon distribution generated in thick targets of lead compounds Pb(CH 3 COO) 2 ·3H 2 O, Pb(NO 3 ) 2 and PbCl 2 by 90 Sr beta particles has been investigated theoretically and experimentally in the photon energy region 1–10 keV. The experimental results are compared with the theoretical models describing ordinary bremsstrahlung and the theoretical model which includes polarization bremsstrahlung into ordinary bremsstrahlung, in stripped approximation. It is observed that the experimental results show better agreement with the model which describes bremsstrahlung in stripped approximation in the energy range 3–10 keV. However, the results show positive deviation in the photon energy region of 1–3 keV. Further, it has been found that there is a continuous decrease of polarization bremsstrahlung contribution into ordinary bremsstrahlung in the formation of total bremsstrahlung spectra with increase in photon energy. The suppression of polarization bremsstrahlung has been observed due to the presence of large fraction of low Z elements in the compounds. The results clearly indicate that polarization bremsstrahlung plays an important role in the formation of total bremsstrahlung spectra in compounds in the studied energy region. [ABSTRACT FROM AUTHOR]

Background: Positron probes can accurately localize malignant tumors by directly detecting positrons emitted from positron-emitting radiopharmaceuticals that accumulate in malignant tumors. In the conventional method for direct positron detection, multilayer scintillator detection and pulse shape discrimination techniques are used. However, some γ-rays cannot be distinguished by conventional methods. Accordingly, these γ-rays are misidentified as positrons, which may increase the error rate of positron detection., Purpose: To analyze the energy distribution in each scintillator of the multilayer scintillator detector to distinguish true positrons and γ-rays and to improve the positron detection algorithm by discriminating true and false positrons., Methods: We used Autoencoder, an unsupervised deep learning architecture, to obtain the energy distribution data in each scintillator of the multilayer scintillator detector. The Autoencoder was trained to separate the combined signals generated from the multilayer scintillator detector into two signals of each scintillator. An energy window was then applied to the energy distribution obtained using the trained Autoencoder to distinguish true positrons from false positrons. Finally, the performance of the proposed method and conventional positron detection algorithm was evaluated in terms of the sensitivity and error rate for positron detection., Results: The energy distribution map obtained using the trained Autoencoder was proven to be similar to that of the simulated results. Furthermore, the proposed method demonstrated a 29.79% (+0.42%p) increase in positron detection sensitivity compared to the conventional method, both having an equal error rate of 0.48%. However, when both methods were set to have the same sensitivity of 1.83%, the proposed method had an error rate that was 25.0% (-0.16%p) lower than that of the conventional method., Conclusions: We proposed and developed an Autoencoder-based positron detection algorithm that can discriminate between true and false positrons with a smaller error rate than conventional methods. We verified that the proposed method could increase the positron detection sensitivity while maintaining a low error rate compared to the conventional method. If the proposed algorithm is implemented in handheld positron detection probes or cameras, diseases such as cancers can be more accurately localized in a shorter time compared with using traditional methods., (© 2023 American Association of Physicists in Medicine.)

Trans-arterial radioembolization (TARE) is an intra-arterial treatment method for liver malignancies. In this procedure, the therapeutic tumor dose is significant for predicting the treatment effectiveness while the dose absorbed in an organ at risk provides an understanding of its tolerance to radiation. This study proposes a Monte Carlo (MC) approach for determining absorbed organ doses for patients undergoing TARE treatment. The technique is based on the use of a voxel-based partial body model generated for each patient from his/her anatomical image data to represent the critical body structures more realistically. These structures are first segmented from image slices to create an image block which is then incorporated into a radiation transport package (MCNP6.2) to perform MC simulations. When used along with the parameters specific to a patient's treatment, such as lung-shunt factor, tumor-to-normal liver ratio, fractional uptakes, and administered activity, this approach allowed more accurate simulation of radiation interactions and hence provided absorbed doses specific to a TARE patient. The MC method also calculated the absorbed doses in organs or tissues that were close to target tissues for which the Medical Internal Radiation Dose Committee (MIRD) formalism makes no predictions. MIRD calculations were found to overestimate the absorbed doses by as much as 11% in lungs, 5% in liver, and 20% in tumor volumes. This raises concerns about the treatment's efficacy when estimating the correct activity to be administered to a patient. When each patient simulation was repeated with a 90 Y source spectrum to reflect the distribution of varying beta energies, the liver and the lungs were observed to receive relatively lower doses than those obtained with monoenergetic beta particles. Thus, it can be stated that the approach adopted in this study offers a more precise model of the patient's critical tissues and serves as a personalized dosimetric tool for TARE treatment planning., (© 2023 Institute of Physics and Engineering in Medicine.)

Prostate-specific membrane antigen (PSMA)-based low-molecular-weight agents using beta(β)-particle-emitting radiopharmaceuticals is a new treatment paradigm for patients with metastatic castration-resistant prostate cancer. Although results have been encouraging, there is a need to improve the tumor residence time of current PSMA-based radiotherapeutics. Albumin-binding moieties have been used strategically to enhance the tumor uptake and retention of existing PSMA-based investigational agents. Previously, we developed a series of PSMA-based, β-particle-emitting, low-molecular-weight compounds. From this series, 177 Lu-L1 was selected as the lead agent because of its reduced off-target radiotoxicity in preclinical studies. The ligand L1 contains a PSMA-targeting Lys-Glu urea moiety with an N-bromobenzyl substituent in the ε-amino group of Lys. Here, we structurally modified 177 Lu-L1 to improve tumor targeting using two known albumin-binding moieties, 4-( p -iodophenyl) butyric acid moiety (IPBA) and ibuprofen (IBU), and evaluated the effects of linker length and composition. Six structurally related PSMA-targeting ligands (Alb-L1-Alb-L6) were synthesized based on the structure of 177 Lu-L1. The ligands were assessed for in vitro binding affinity and were radiolabeled with 177 Lu following standard protocols. All 177 Lu-labeled analogs were studied in cell uptake and selected cell efficacy studies. In vivo pharmacokinetics were investigated by conducting tissue biodistribution studies for 177 Lu-Alb-L2- 177 Lu-Alb-L6 (2 h, 24 h, 72 h, and 192 h) in male NSG mice bearing human PSMA+ PC3 PIP and PSMA- PC3 flu xenografts. Preliminary therapeutic ratios of the agents were estimated from the area under the curve (AUC 0-192h ) of the tumors, blood, and kidney uptake values. Compounds were obtained in >98% radiochemical yields and >99% purity. PSMA inhibition constants ( K i s) of the ligands were in the ≤10 nM range. The long-linker-based agents, 177 Lu-Alb-L4 and 177 Lu-Alb-L5, displayed significantly higher tumor uptake and retention ( p < 0.001) than the short-linker-bearing 177 Lu-Alb-L2 and 177 Lu-Alb-L3 and a long polyethylene glycol (PEG) linker-bearing agent, 177 Lu-Alb-L6. The area under the curve (AUC 0-192h ) of the PSMA+ PC3 PIP tumor uptake of 177 Lu-Alb-L4 and 177 Lu-Alb-L5 were >4-fold higher than 177 Lu-Alb-L2, 177 Lu-Alb-L3, and 177 Lu-Alb-L6, respectively. Also, the PSMA+ PIP tumor uptake (AUC 0-192h ) of 177 Lu-Alb-L2 and 177 Lu-Alb-L3 was ~1.5-fold higher than 177 Lu-Alb-L6. However, the lowest blood AUC 0-192h and kidney AUC 0-192h were associated with 177 Lu-Alb-L6 from the series. Consequently, 177 Lu-Alb-L6 displayed the highest ratios of AUC(tumor)-to-AUC(blood) and AUC(tumor)-to-AUC(kidney) values from the series. Among the other agents, 177 Lu-Alb-L4 demonstrated a nearly similar ratio of AUC(tumor)-to-AUC(blood) as 177 Lu-Alb-L6. The tumor-to-blood ratio was the dose-limiting therapeutic ratio for all of the compounds. Conclusions: 177 Lu-Alb-L4 and 177 Lu-Alb-L6 showed high tumor uptake in PSMA+ tumors and tumor-to-blood ratios. The data suggest that linker length and composition can be modulated to generate an optimized therapeutic agent.

The mass attenuation coefficient of lead nitrate (Pb(NO3)2)-filled polycarbonate (PC) composite films were determined both computationally (using Baltakmen's and Thummel empirical formulae) and experimentally using 204Tl and 90Sr-90Y radio-isotopes for films at different filler levels 0, 5, 15, 25, 35 and 50 weight percent (Wt.%). In comparison with Thummel empirical formula, the values obtained from Baltakmen's empirical formula is in good agreement with the experiment. The percentage decrease of half value layer values were (52 ± 8) and (60 ± 10)% for 204Tl and 90Sr-90Y, on comparing the values for 0 and 50 Wt.% films, and so the prepared composite films shield the beta particles effectively. The PC that used to shield the low-energy beta particles of 90Sr-90Y can also moderate the higher energy beta particles; the plot of end point energy of 90Sr-90Y versus thickness of PC exhibits a decreasing trend, which confirms that PC acts as an electron moderator., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)