Medical Physics Applications Research Articles

Attenuation coefficients of soy-lignin bonded Rhizophora spp. particleboard as a potential phantom material using Monte Carlo GATE

This work aimed to determine the linear and mass attenuation coefficients of soy-lignin bonded Rhizophora spp. particleboard intended for use as a phantom material using Monte Carlo GATE simulation. At a desired density of 1.0 gcm-3, particleboard constructed of Rhizophora spp. wood trunk bonded with soy flour and lignin was created. The sample’s elemental composition was identified using energy dispersive X-ray spectroscopy. The GATE software was used to simulate the setup with the histories of 1 × 107, and comparison was made between the experimental and simulation data. The disparities between the linear and mass attenuation coefficients of the samples experimentally measured and calculated using GATE at low energy photons were quite small. The result revealed a good agreement between the experimental and simulation data, and the attenuation coefficients were in close proximity with XCOM of water. The outcome revealed GATE adequacy for validation of attenuation coefficient measurement in bioresources phantom material for medical physics application.

Квантовые вычисления в медицинской физике: особенности алгоритмов и их перспективы

Background: Quantum computing represents a paradigm leap in computational capabilities, with potential applications across various scientific disciplines. The complicated computations required for imaging, radiation therapy, and molecular modeling in medical physics give novel prospects for quantum computing. Objective: This article investigates the role of quantum computing in medical physics research, with an emphasis on its potential to improve computational efficiency and accuracy and develop novel treatment approaches. Methods: A thorough literature analysis was undertaken to investigate recent advances in quantum computing and their implications in medical physics. Case studies were reviewed to demonstrate practical applications and possible advantages. Theoretical models were tested to forecast future developments. Statistical data from quantum computing implementations were gathered from many sources, particularly on improving processing speed and accuracy in medical physics applications. Results: The findings show that quantum computing can significantly improve the processing speed of complex simulations and imaging techniques, with some quantum algorithms outperforming classical algorithms by up to 100 times. In radiation therapy planning, quantum computing has exhibited a 25% boost in dose distribution calculation precision. Quantum algorithms have lowered calculation times in molecular modeling by about 40%, potentially boosting drug development and customized therapy by 30%. Conclusion: Quantum computing has the potential to alter medical physics by increasing computational capacity, which could lead to advancements in diagnostics, treatment planning, and medication development. The statistical results corroborate the promise of quantum computing in these domains, emphasizing the importance of ongoing interdisciplinary collaboration and research to fully achieve these benefits and address present hurdles in incorporating quantum computing into clinical practice.

Enhanced OSL emission from α- Al2O3 produced in the presence of halloysite nanocrystals

Aluminum oxide (Al2O3) compounds are extensively used in ionizing radiation dosimetry due to their high sensitivity when doped with carbon. However, their production is difficult and expensive, leading to much research on alternative ways to increase its sensitivity. This paper proposes a seed-mediated synthesis of α-Al2O3 by the combustion method with halloysite nanocrystals as seeds, which also have the ability to scavenge heavy metal ions. The dosimetric features were studied by radioluminescence (RL), thermoluminescence (TL), and optically stimulated luminescence (OSL). Scanning electron microscopy images and X-ray diffraction patterns pointed to the halloysite nanotubes (HNT) acting as heterogeneous nucleation seeds, and as adsorber centers for the chromium ions (Cr3+), as evidenced by the decreased crystallite size and Cr3+ RL emission. Decreased TL intensity upon increasing HNT content in addition to the RL data suggested that the Cr3+ ions strongly participate in the TL emission process as a luminescent center. Remarkable 6-fold enhanced OSL area intensity and 69-fold OSL initial intensity enhancement were registered from the samples seed-mediated by HNT, revealing that, by scavenging Cr3+, the HNT eliminated a luminescent center that competes with the OSL emission. Therefore, HNTs are promising nanomaterials to enhance the sensitivity of Al2O3 dosimeters with potential application in medical physics, where a decrease in the density of concurrent luminescent centers and an increase in OSL intensity were evidenced by the presence of HNT in Al2O3.

Investigating the optical and magnetic properties of engineered multifunctional graphene oxide and potential application in medical physics and nonlinear optics‏

Herein, the synthesis of multifunctional engineered GOs with the structure of GO@Fe3O4-ligands-CdTe quantum dots (QDs) by an environment-friendly aqueous method was reported. l-cystein (Cys), 3-trimethoxysilyl-propanethiol (TMSP), and glutathione (GSH) were selected as ligands. The as-prepared GO@Fe3O4-ligands-CdTe QDs hybrid nanostructures were characterized by different methods. The findings indicate that the nanocomposites of GO@Fe3O4–ligands–CdTe QDs demonstrate superparamagnetic properties at room temperature. The saturation magnetization values for GO@Fe3O4, GO@Fe3O4-Cys-CdTe, GO@Fe3O4-GSH-CdTe, and GO@Fe3O4-TMSP-CdTe, are 25, 14, 16, and 2 emu g−1, respectively. These nanocomposites show stable and strong luminescence at 580-600 nm. The magnetic nanostructures also reveal the absorption wavelength at 300-490 nm. Using TMSP ligand as a bridge between QDs and magnetic GOs, the luminescence of the nanostructure has not decreased much compared to CdTe QDs. The use of Cys ligand preserves the saturation magnetism of the nanocomposite more than magnetic GO, and the dispersed nanostructure is stable in water. Furthermore, the transverse and longitudinal optical (TO and LO) phonon modes of prepared GO@Fe3O4–ligands–CdTe QDs were obtained by Kramers-Kronig (KK) relations based on fourier-transform infrared (FTIR) spectroscopy. The Z-scan results show that the type of used ligand has a great effect on the nonlinear optical (NLO) properties of the final product. The largest NLO parameters are related to GO@Fe3O4- TMSP -CdTe QDs, and the values of nonlinear absorption coefficient and nonlinear refractive index were obtained as 2.17×10−3(cm/W) and10.27×10−8(cm2/W), respectively. As a result, GO@Fe3O4–ligands–CdTe QDs nanostructures can be considered as promising multifunctional nanostructures for various biomedical applications and NLO devices.

Simultaneous Double Dose Measurements Using TLD-100H

Thermoluminescent dosimeters (TLD) and optically stimulated luminescent dosimeters (OSLD) are practical, accurate, and precise tools for point dosimetry in medical physics applications. The objective of this study is to investigate the luminescence properties—both OSL and TL—of lithium fluoride (LiF) doped with magnesium (Mg), copper (Cu), and phosphorous (P) (LiF: Mg, Cu, P), commercially known as TLD-100H. The goal is to devise a methodological approach for dose measurement that allows for obtaining two independently measured dose values at each irradiation point, thereby improving accuracy and precision. The luminescence properties of TLD-100H were studied using a beta irradiation source (90Sr/90Y) integrated into the TL/OSL DA-15 automated Risø reader. This study identified the ideal experimental conditions for optimal dose evaluation and used them for dosimeter calibration across doses ranging from 0.5 to 4.0 Gy. The results demonstrated that, under optimal measurement parameters, the OSL and residual thermoluminescence (ResTL) signals—correlated to two trap systems within the dosimeter—exhibited high reproducibility, stability over multiple cycles, and high precision and accuracy (≤2%). Specifically, the OSL response showed good linear behavior across the investigated dose range, while the ResTL signal exhibited linear behavior between 0.5 and 2 Gy and sublinear behavior for doses >2 Gy.

Characterization of X-ray Beam for Half and Quarter Value Layers

Introduction: The aim of this work is to assess the penetrating ability of an X-ray beam through a specific material, in conditions of narrow-beam geometry. Materials and Methods: During the experiment, samples were switched with the X-ray tube turned off, and the primary intensity of the unshielded X-ray beam (fixed 2.5mm shielding) was measured. Parameters were kept constant throughout, and the electrometer was used to stabilize the readings. Subsequent measurements aimed to determine the Half-Value Layer (HVL) and Quarter-Value Layer (QVL) by interpolating various sample slices to achieve intensity values of I/2 and I/4, respectively. The data were used to plot and analyze HVL and QVL graphs, providing insights into the attenuation properties of the X-ray beam through different materials. Findings of the result: The primary findings indicated that the initial unshielded X-ray beam intensity, with parameters set to 37.5 kV and 40 mA, provided a stable baseline measurement. The results showed a consistent decrease in intensity with increased sample thickness, confirming the exponential attenuation of X-rays. The HVL was determined by identifying the sample thickness that reduced the initial intensity by half, and the QVL by the thickness reducing it to one-fourth. The experimental data closely followed theoretical predictions, with HVL and QVL values providing a quantitative measure of the material's attenuation properties. Conclusion: Graphical analysis of the results demonstrated clear linear relationships on a semi-logarithmic scale, validating the accuracy of the measurement process and the reliability of the electrometer readings. These findings contribute to a better understanding of X-ray attenuation in different materials, which is crucial for various applications in medical physics and radiography.

RADIOTHERAPY 3D ISODOSEZONES GRAPHICAL OPTIMIZATION FOR HYPERFRACTIONATED TREATMENT PLANNING DOSIMETRY IN LUNG AND HEAD-NECK TUMORS WITH BIOLOGICAL EFFECTIVE DOSE MODEL

In recent lung and prostate cancer-radiotherapy contributions, [101-5], 3D imaging-processing Isodosezones [ Casesnoves, 2022 ], delimited by 3D Isodoselines were explained in lung cancer and other tumor types, such as prostate or lung. The radiotherapy model applied was the classical BED one algorithm. Modern biological-model-based Treatment Planning Optimization can get objective improvements by using Isodosezones/lines when selecting the optimal dose delivery/schedule for any personalized treatment. Improved programming, from [ Casesnoves, May 7th, 2024 ], and engineered software is perfectioned-developed for numerical hyperfractionated 3D TPO lung and head-neck cancer imaging-processing with upgraded previous database. Mathematical algorithms are explained-detailed. Developed programming patters and arrays are briefed. A series of imaging-processing graphics results obtained with the 3D Isodosezones Pareto-Multiobjective Optimization programming database are shown and explained in detailed. Applications in radiotherapy-oncology medical physics are subsequently briefed.

Rhizophora-based particleboard bonded with soy flour and lignin as potential phantom

Rhizophora-based particleboard was evaluated for its suitability as phantom material, especially in medical physics applications. The elemental composition, effective atomic number, micrographic structures, computed tomography (CT), and attenuation properties of Rhizophora-based particleboards were examined. These investigations considered three different particle sizes and three distinct adhesive mixtures. Rhizophora sample at particle sizes of 0 to 103 µm, with 4.5% soy flour and 1.5% lignin (C6) presented with a homogenous compound with better uniformity compared with other samples, and Rhizophora sample at particle sizes of 104 to 210 µm, with 9% soy flour and 3% lignin (B12) demonstrated an effective atomic number of 8.15, which is similar to water. C6 also presented with a density distribution profile with close proximity to water. The measured attenuation coefficients of samples were aligned closely with those of water, as determined by XCOM. The results suggest that the formulation of soy flour and lignin as adhesives for Rhizophora-based particleboard is suitable for the fabricating of phantom material for medical physics applications, especially mainly due to its natural origin.

Exploring the impact of anode material on X-ray photon fluence and characteristics: A Monte Carlo simulation study

This study investigates the critical significance of anode material selection in defining the energy spectrum and properties of X-ray photons in medical physics applications. Using the GATE platform and Monte Carlo simulations, a direct relationship between anode material atomic number and photon fluence is demonstrated. As the atomic number increases from Z = 29 (Copper) to Z = 74 (Tungsten), photon fluence rises by 62 %, indicating a substantial impact on X-ray production. Furthermore, the X-ray spectrum is affected by this material-driven changes, revealing a noticeable shift towards higher energy values: the mean energy of the continuous spectrum rises from 46.97 keV for Copper to 49.0 keV for Tungsten. The thermal properties of the material affect the temperature increase at the focal point. Rhodium and Molybdenum have a higher temperature rise than Copper (Cu) and Tungsten (W), because Cu and W have a greater thermal diffusion compared to other materials. These findings underscore the significance of anode material choice in optimizing X-ray systems which may enhance diagnostic accuracy and efficiency in diverse applications.

Evaluation of a compact electron preinjector using a low beta (β) acceptance X-band accelerating structure

At the University of Melbourne X-LAB we are investigating the use of a low β acceptance X-band accelerating structure as part of the design of an all X-band RF electron preinjector optimised for the production of low emittance electron bunches for medical physics applications and compact light source development.In this work we will elaborate on the estimated performance, design issues, and optimisation methodology of the preinjector beamline.

Terahertz-driven positron acceleration assisted by ultra-intense lasers.

Generation and acceleration of energetic positrons based on laser plasma have attracted intense attention due to their potential applications in medical physics, high energy physics, astrophysics and nuclear physics. However, such compact positron sources face a series of challenges including the beam dispersion, dephasing and unstability. Here, we propose a scheme that couples the all-optical generation of electron-positron pairs and rapid acceleration of copious positrons in the terahertz (THz) field. In the scheme, nanocoulomb-scale electrons are first captured in the wakefield and accelerated to 2.5 GeV. Then these energetic electrons emit strong THz radiation when they go through an aluminum foil. Subsequently, abundant γ photons and positrons are generated during the collision of GeV electron beam and the scattering laser. Due to the strong longitudinal acceleration field and the transvers confining field of the emitted THz wave, the positrons can be efficiently accelerated to 800 MeV, with the peak beam brilliance of 2.26 × 1012s-1mm-2mrad-2eV-1. This can arouse potential research interests from PW-class laser facilities together with a GeV electron beamline.

Blinding of Residency Applications in Medical Physics: Promises and Pitfalls

The feasibility of blinding applications for a medical physics residency program has yet to be demonstrated in the literature. We explore the application of an automated approach with human review and intervention to blind applications during the annual medical physics residency review cycle. Applications were blinded using an automated process and used for the first phase of residency review in the program. We retrospectively compared self-reported demographic and gender data with blinded and nonblinded cohorts from 2 sequential years of review from a medical physics residency program. Demographic data were analyzed comparing applicants with candidates selected to move to the next phase of the review process. Interrater agreement was also evaluated from the applicant reviewers. We show the feasibility of blinding applications for a medical physics residency program. We observed no more than a 3% difference between the gender selection within the first phase of application review but greater differences when examining race and ethnicity between the 2 methods. The greatest difference was shown to be between Asian and White candidates, where there are statistical differences in the scores in the rubric categories of essay and overall impression. We suggest that each training program critically evaluate its selection criteria for potential sources of bias within the review process. We recommend further critical investigation of processes to promote equity and inclusion to ensure the methods and outcomes are aligned with the mission of the program. Finally, we recommend that the common application provide an option for blinding applications at the source so this can be an option to facilitate efforts for evaluating unconscious bias in the review process.

Semiconducting and scintillating glasses for x-ray detection

X-ray detectors are commonly used for medical, crystallography and space physics applications. Most of the current x-ray detectors use cadmium zinc telluride (CZT) as the active medium. This report investigates high density semiconducting and scintillating glasses as potential alternatives to CZT. For the semiconducting glasses, samples composed of xCuO–((1−x)/2)PbO–((1−x)/2)V2O5 and xFeO–((1−x)/2)PbO–((1−x)/2)V2O5, for the scintillating glasses, samples composed of xGd2O3+yWO3+(1−x−y)2H3BO3, doped with 1–6% Eu3+ or Tb3+, were investigated in this study. The glass-making conditions, density, Raman spectroscopy analysis, photoluminescence excitation and emission spectra, as well as conductivity measurements performed on various samples, are reported. The interaction of x-rays with all the glass samples was simulated using GATE software, and their mass attenuation coefficients were calculated and compared with CZT.

Reflections on a life with Monte Carlo in Medical Physics.

The author reminisces about some of his experiences working with Monte Carlo techniques for Medical Physics applications.

Potential of modular J-PET for applications in the field of particle and medical physics

Modular J-PET is the new prototype of the Jagiellonian Positron Emission Tomograph. The portability feature due to its modular design makes it a unique tomograph with a larger axial field of view of 50 cm. The complete ring is composed of 24 modules that can be configured as a diagnostic chamber with a diameter of approximately 76 cm or as a detection setup consisting of several modules for experimental studies where multiple photons are generated in a single event. The J-PET collaboration explicitly studies the decays of the positronium atom (Ps), which is a bound state of electron and positron that self-annihilate into multiple photons. The modular J-PET provides a significant phase space covrage for the registration of photons originating from the decays of Ps atoms. In this paper, we discuss the properties of the modular J-PET and its potential applications in medical and particle physics.

PyMedPhys: A community effort to develop an open, Python-based standard library for medical physics applications

Biggs et al., (2022). PyMedPhys: A community effort to develop an open, Python-based standard library for medical physics applications. Journal of Open Source Software, 7(78), 4555, https://doi.org/10.21105/joss.04555

Academic program recommendations for graduate degrees in medical physics: AAPM Report No. 365 (Revision of Report No. 197).

Academic program recommendations for graduate degrees in medical physics: AAPM Report No. 365 (Revision of Report No. 197).

Relative dose-response from solid-state and gel dosimeters through Monte Carlo simulations

The present work compared the relative absorbed dose of some dosimetric materials, for energies of 250 kV and 6 MV, using PENELOPE and MNCPX codes. The composition of each material GD-301, TLD-100, MAGIC, and MAGAT were simulated and disposed of in a phantom filled with water following reference conditions recommended by the TRS-398 protocol. Percentage depth dose was used as a parameter of comparison. Since the obtained results with both codes were found a maximum difference of up to 2 % when compared the water material with experimental data before 6cm were found to a maximum difference of up to 2.2% for 6 MV and 5.5 % for 250 kV. Ratios between simulated PPD and experimental PDD values showed a maximum difference in the build-up region, for 6 MV, due to highsensitivityive from the incident fluency in the simulated and experimental conditions. The ratios for 250 kV showed significant differences from the simulated solid-state rather than gel dosimeters, due to its low energy, depth angular dependence from the solid-state dosimeter, as corroborating by literature. Even the differences showed for both codes, especially for lower energy, due to cross-the section database that implied the interaction probability for each Monte Carlo code, this method has been widely used to model radiation transport in several applications in medical physics, especially in dosimetry.

Measurements of the Zr96(α,n)Mo99 cross section for astrophysics and applications

The reaction $^{96}\mathrm{Zr}(\ensuremath{\alpha},\mathrm{n})^{99}\mathrm{Mo}$ plays an important role in $\ensuremath{\nu}$-driven wind nucleosynthesis in core-collapse supernovae and is a possible avenue for medical isotope production. Cross-section measurements were performed using the activation technique at the Edwards Accelerator Laboratory. Results were analyzed along with world data on the $^{96}\mathrm{Zr}(\ensuremath{\alpha},n)$ cross section and $^{96}\mathrm{Zr}(\ensuremath{\alpha},\ensuremath{\alpha})$ differential cross section using large-scale Hauser-Feshbach calculations. We compare our data, previous measurements, and a statistical description of the reaction. We find a larger cross section at low energies compared to prior experimental results, allowing for a larger astrophysical reaction rate. This may impact results of core-collapse supernova $\ensuremath{\nu}$-driven wind nucleosynthesis calculations but does not significantly alter prior conclusions about $^{99}\mathrm{Mo}$ production for medical physics applications. The results from our large-scale Hauser-Feshbach calculations demonstrate that phenomenological optical potentials may yet be adequate to describe $(\ensuremath{\alpha},n)$ reactions of interest for $\ensuremath{\nu}$-driven wind nucleosynthesis, albeit with regionally adjusted model parameters.

An analytical model to calculate the primary and secondary acoustic forces acting on microbubbles due to a short pulsed laser excitation

This work presents a comprehensive analytical approach to describe photoacoustic waves resulting from a pulsed laser excitation. The spatial part of the laser is modeled by a zeroth-order Bessel function of the first kind, which has a wide range of applications in optics and medical physics, such as optical trapping and nonlinear effects resulting from the interaction of a pulsed laser with tissue in photoacoustic imaging. The temporal part of the laser is described by a Gaussian function, which is a pretty realistic approximation since the interaction of the laser with the medium is instantaneous. The photoacoustic wave equation is solved analytically using the Fourier transform and the Greens’ function methods. The solution of the photoacoustic wave equation depends explicitly on position, time, pulse duration, and beam-width of the pulsed laser. The effects of these dependencies on the photoacoustic wave are investigated. Later, the primary and secondary radiation forces acting on microbubbles Albunex and Quantison are calculated using the magnitude of the photoacoustic pressure wave. The primary and secondary radiation forces decrease considerably with the distance from the photoacoustic absorber. These forces increase as the beam-width increases while they decrease as the pulse duration gets longer. The primary radiation forces on the microbubbles are on the order of nanonewtons. The force at this scale can be used to manipulate microbubbles. The secondary radiation force between identical microbubbles is in the range of piconewtons. Hence, this force can be used to determine the viscoelastic properties of microbubbles even though it is very small compared to the primary radiation force. The radiation forces determined by this work are also compared with those calculated by another study describing the laser’s spatial profile with a Gaussian function. The forces obtained by this work are larger than the forces determined by the Gaussian function approximation at the positions near the source. The forces obtained by the two approaches show similar behaviors, and they decrease remarkably with the distance from the source. Thus, the model presented in this work can be used to study the nonlinear mechanism in photoacoustics, such as enhancing image contrast and determining the tissue temperature. It can also be helpful for the applications of microbubbles in medical imaging and drug delivery as carriers.