Journal of Medical Physics最新文献

Aim: This study aims to investigate the influence of voxel size and postfiltering on the quantification of standardized uptake value (SUV) in positron emission tomography/computed tomography (PET/CT) images.

Materials and methods: National Electrical Manufacturers Association phantom with the spheres of different sizes were utilized to simulate the lesions. The phantom was scanned using a PET/CT scanner, and the acquired images were reconstructed using two different matrix sizes, (192 × 192) and (256 × 256), and a wide range of postfiltering values.

Results: The findings demonstrated that postfiltering significantly affected SUV measurements. The changes in postfiltering values can result in overestimation or underestimation of SUV values, highlighting the importance of carefully selecting appropriate filters. Increasing the matrix size improved SUVmax and SUVmean values, particularly for small-sized spheres. Smaller voxel reconstructions slightly reduced partial volume effects and partially enhanced SUV quantification.

Conclusions: Careful consideration of postfiltering values and matrix size selection can lead to better SUV quantification. These findings emphasize the need to optimize the reconstruction parameters to enhance the clinical utility of PET/CT in detecting and evaluating malignant lesions.

Aim: Magnetic-mediated hyperthermia has emerged as a promising therapeutic approach for treating cancer. This technique employs the heat dissipated by the magnetic nanoparticles when subjected to an external varying magnetic field, to bring about localized hyperthermia in tumor tissues. Owing to their conducive and tuneable "physical, chemical, and magnetic" characteristics, cobalt ferrite (CoFe₂O₄) nanoparticles are recognized as emerging contenders. The aim of the present work was to enhance the magnetic characteristics and guarantee the efficacy of CoFe2 O4 nanoparticles in targeting and eliminating cancer cells.

Methods: CoFe₂O₄ nanoparticles were synthesized using the chemical co-precipitation route and underwent rigorous structural, morphological, and magnetic characterization techniques. The synthesized particles were then subjected to in vitro studies to evaluate their cytotoxicity and antimicrobial susceptibility.

Results: The characterization techniques confirmed the cubic structure, ferrite phase, and spherical and magnetic nature of CoFe₂O₄ nanoparticles. The zeta potential was found to be - 0.0048V (4.8 mV). Cytotoxicity analysis exhibited decreased cell viability with increasing concentrations of CoFe₂O₄ nanoparticles. Antimicrobial studies displayed good inhibiting properties.

Conclusion: The zeta potential of the synthesized CoFe₂O₄ nanoparticles was found to be higher than that of the breast cancer cells (MCF-7) which proves the synthesized drug to be effective. The in vitro studies also disclose the efficacy of the drug over cancer cells.

Purpose: This study aims to quantify the secondary radiation dose caused by photoneutrons during prostate cancer treatment using an 18 MV medical linear accelerator (LINAC) through Monte Carlo simulations and experimental validation.

Methods: Monte Carlo simulations were performed using G4Linac_MT to model the 18 MV photon beam of an Elekta LINAC. The simulation results were validated against experimental measurements. Neutron characteristics, including penetration, cross-section interactions, Linear Energy Transfer (LET), and dose contributions, were analyzed using an adult male ICRP phantom. Prostate treatment scenarios involved 3D-CRT plans with 4-fields, 5-fields, and 7-fields. Specific absorbed fractions (SAFs) in various organs were also evaluated.

Results: Simulation and experimental measurements showed strong agreement, with a dose error of approximately 0.74%, and 97% of dose points passed a 2%/2 mm gamma index. Intermediate neutrons constituted 87.05%, while 12.95% were fast neutrons. Neutron dose contributions were 0.63%, 0.33%, and 0.77% for the 3D-CRT 4-field, 5-field, and 7-field plans, respectively. SAF values decreased as neutron energy increased, highlighting reduced neutron interaction efficiency at higher energies.

Conclusions: Monte Carlo simulation is a reliable approach for evaluating neutron dose contributions in high-energy X-ray LINACs. Optimization of treatment plans is essential to minimize neutron-induced dose contributions.

The study aims to assess the fluence distribution and point dosage between two phantoms for patient-specific quality assurance on the Tomotherapy system. This was a retrospective study conducted on 15 patients who had radiation using the Helical Tomotherapy Machine (Radixact, Accuray Inc.). We used two phantoms to quantify the fluence produced by the treatment planning system (TPS) and recorded from the machine. The ArcCHECK (Sun-Nuclear) has 1386 diodes placed in a cylindrical configuration. The minimal resolution for this was 7 mm. The second was Delta⁴, supplied by ScandiDos. It has 1069 diode detectors arrayed in a crossed orthogonal configuration with a minimum resolution of 5 mm. All patient plans were transferred to these phantoms to validate the accuracy of treatment plan delivery. We used SunCHECK and ScandiDos Delta⁴ software to compare the fluence produced by the TPS with the fluence measured by the equipment. In ArcCHECK, we used an external ionization chamber, cc13 (IBA dosimetry), whereas in Delta⁴,we employed a central diode detector to quantify point dosage. The mean and standard deviation of the gamma pass percentage with ArcCHECK were 98.3 ± 0.8%, with an average point dose deviation of ± 0.94%. The mean and standard deviation of the gamma pass percentage using Delta⁴ was 99.1 ± 1.6%, while the average point dose deviation was ± 0.60%, both of which were well within the 3% tolerance employing the two phantoms.

Purpose: This study investigated the effect of Hounsfield units (HU)-relative electron density (RED) calibration curves obtained with devices from three different Computed Tomography (CT) manufacturers on dose distribution in Accuray Precision planning of patients with lung cancer.

Methods: All CT data required for treatment planning system (TPS) were obtained using the Tomotherapy "cheese" phantom. HU RED calibration curves were created with images obtained from Siemens Somatom, GE Optima, and Toshiba Aquilion devices. The obtained calibration curve was extrapolated. CT images of lung cancer patients were acquired on a single device and treatment plans were created. The existing plans were recalculated using three calibration curves and the effect of the HU RED calibration curve on dose distribution was analyzed.

Results: The results showed that different CTs did not produce significant dose differences in organ doses and PTV for Accuray TPS.

Conclusions: Based on clinical judgment, images from different CT devices can be used in treatment planning.

Background: Recently, the green synthesis process has been utilized to manufacture a large quantity of metal nanocrystallites due to its low cost and the availability of numerous natural resources and the find the activity of bacteria and viruses that in the body of humans.

Aims and objectives: In this study, nanocrystallites of selenium oxide were produced utilizing Hibiscus sabdariffa. Researchers have analyzed the antibacterial properties and nanostructure characteristics of selenium oxide nanocrystallites using various techniques methods, such as imaging microscopy, scanning electron microscopy, ultraviolet‒visible spectroscopy (UV‒VIS), transmission electron microscopy, atomic force microscopy, and X-ray diffraction (XRD) spectroscopy.

Results: According to the results, the films are discovered to have a nanocrystalline structure in a cubic spinel configuration. The crystallites are semispherical in shape and are both uniform and easily distributed. The XRD data were recorded on card number 22-1314, and the 2 θ (hkl) value was 38.351 (311). The UV‒VIS spectrum of the material exhibited a plasmon resonance peak at 272 nm, confirming the presence here of selenium oxide. This study also investigated the response of four distinct strains of pathogenic bacteria to biosynthesized selenium oxide nanoparticles (NPs). The data indicate that the biosynthesized selenium oxide NPs were highly effective against Klebsiella spp. and had the lowest effectiveness against Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli.

Conclusions: The utilization of selenium oxide nanocrystals as antibacterial agents has yielded diverse outcomes, demonstrating their remarkable efficacy in combatting Klebsiella spp.

Background: The usage of a semiconductor detector with a pinhole collimator can provide high spatial resolution due to its high intrinsic resolution. However, the collimator system has low sensitivity due to the hole's small diameter. Therefore, the optimization between the spatial resolution and sensitivity is critical for determining the image quality in the gamma camera system.

Aims and objectives: A pinhole collimator was designed and simulated to achieve the desired level of resolution and sensitivity in a gamma camera by utilizing a CdTe semiconductor detector.

Materials and methods: To conduct this objective, a simulation toolkit based on the Geant4 Application for Tomographic Emission (GATE) was employed. The imaging capabilities of the proposed system were assessed by varying the magnification factor and pinhole diameter to estimate spatial resolution and sensitivity. Moreover, a hot rod phantom was designed to evaluate the system's overall imaging functionality.

Results: Results revealed that an increase in the pinhole diameter was correlated with an increase in sensitivity, while the spatial resolution was decreasing. There were distinct variations in sensitivity and spatial resolution depending on changes in the magnification factor as well. Finally, by analyzing trade-off curves, 1.38±0.081 mm was approximately the optimal pinhole diameter for our proposed system.

Conclusion: The optimum position for a pinhole collimator with a CdTe semiconductor detector was demonstrated.

Context: This article introduces a new cloud-based point-of-care system to monitor heart rate variability (HRV).

Aims: Medical investigations carried out at dispensaries or hospitals impose substantial physiological and psychological stress (white coat effect), disrupting cardiovascular homeostasis, which can be taken care by point-of-care cloud computing system to facilitate secure patient monitoring.

Settings and design: The device employs MAX30102 sensor to collect peripheral pulse signal using photoplethysmography technique. The non-invasive design ensures patient compliance while delivering critical insights into Autonomic Nervous System activity. Preliminary validations indicate the system's potential to enhance clinical outcomes by supporting timely, data-driven therapeutic adjustments based on HRV metrics.

Subjects and methods: This article explores the system's development, functionality, and reliability. System designed is validated with peripheral pulse analyzer (PPA), a research product of electronics division, Bhabha Atomic Research Centre.

Statistical analysis used: The output of developed HRV monitor (HRVM) is compared using Pearson's correlation and Mann-Whitney U-test with output of PPA. Peak positions and spectrum values are validated using Pearson's correlation, mean error, standard deviation (SD) of error, and range of error. HRV parameters such as total power, mean, peak amplitude, and power in very low frequency, low frequency, and high frequency bands are validated using Mann-Whitney U-test.

Results: Pearson's correlation for spectrum values has been found to be more than 0.97 in all the subjects. Mean error, SD of error, and range of error are found to be in acceptable range.

Conclusions: Statistical results validate the new HRVM system against PPA for use in cloud computing and point-of-care testing.

Purpose: Medical physics professional development is limited in parts of the globe and can be aided by virtual mentoring. A global online perception survey was conducted to elucidate the characteristics of the preferred virtual mentoring program.

Methods: Informed by a literature review and pilot testing by focus groups, the survey was electronically disseminated to multiple medical physics organizations, list servers, and professional contacts. It addressed issues including factors and barriers influencing successful mentoring; mentors'/mentees' matching preferences; frequency and length of meetings; importance of defining expectations; formal agreement; and assessment of the mentoring process. Descriptive statistics were used to characterize responses including comparisons by country income level.

Results: The 396 responders (68% male and 32% female) were from 76 countries with 66% from high-income countries (HICs) and 34% from low- and middle-income countries (L&MICs). Data were provided on experience level as mentors (43% "little [occasional]", 38% "lot [regular or ongoing]") and mentees (53% "little [occasional]", and 23% "lot [regular or ongoing]"), and interest in participating in mentorship program (83% as mentor, mentee, or both). L&MIC responders were generally younger with less work experience (55% <10 years versus 28% for HIC responders). Differences between L&MIC and HIC responses occurred when considering the perceived limitations and barriers to virtual mentoring. Preferences were given to mentoring logistics (formal agreement, frequency, length, and format of meetings).

Conclusions: Factors to consider in developing a virtual mentorship program are informed by the survey results and are applicable to both HIC and L&MIC contexts, to medical physicists, and to other related professions.

Background: The response to radiation varies widely among people. Despite recent advances to conform the dose distribution to the tumor volume, it is still impossible to perform radiotherapy based on the biological characteristics of each individual. In this case, identifying a biomarker can be a step toward personalizing treatment. This research was carried out to evaluate the predictive value of dose-volume parameters and vascular endothelial growth factor (VEGF) expression on rectal proctitis toxicity in prostate cancer patients.

Materials and methods: Eighteen patients with prostate cancer who underwent helical tomotherapy were included in the study. VEGF serum level before and after treatment was obtained. Furthermore, dosimetric parameters, including rectal volume, maximum dose, V50, V60, V65, V70, and V75 were extracted. Spearman's correlation coefficient of VEGF-related and dosimetric parameters with the grade ≥1 rectal proctitis was calculated.

Results: In the rectal toxicity group, the mean value of VEGF increased significantly after treatment compared to before (P = 0.008). Despite lower values of pre- and post-treatment VEGF in the toxicity group, this difference was not statistically significant (P > 0.05). Among the dosimetric parameters, only V65 had a significantly higher value in the toxicity group (P = 0.033). The highest correlation coefficients were obtained for pretreatment VEGF values and V65 (-0.446 and 0.450).

Conclusion: The results of the study confirm the correlation of VEGF expression with the pathobiology process of rectal radiation proctitis. However, the pathobiology process of radiation proctitis is complicated. More research is needed to prove the involvement of VEGF expression in the early detection of proctitis.