Real-time non-invasive control of ultrasound hyperthermia using high-frequency ultrasonic backscattered energy inex vivotissue andin vivoanimal studies.

Objective.A reliable, calibrated, non-invasive thermometry method is essential for thermal therapies to monitor and control the treatment. Ultrasound (US) is an effective thermometry modality due to its relatively high sensitivity to temperature changes, and fast data acquisition and processing capabilities.Approach.In this work, the change in backscattered energy (CBE) was used to control the tissue temperature non-invasively using a real-time proportional-integral-derivative (PID) controller. A clinical high-frequency US scanner was used to acquire radio-frequency echo data fromex vivoporcine tissue samples andin vivomice hind leg tissue while the tissue was treated with mild hyperthermia by a focused US applicator. The PID controller maintained the focal temperature at approximately 40 °C for about 4 min.Main results.The results show that the US thermometry based on CBE estimated by a high-frequency US scanner can produce 2D temperature maps of a localized heating region and to estimate the focal temperature during mild hyperthermia treatments. The CBE estimated temperature varied by an average of ±0.85 °C and ±0.97 °C, compared to a calibrated thermocouple, inex vivoandin vivostudies, respectively. The mean absolute deviations of CBE thermometry during the controlled hyperthermia treatment were ±0.45 °C and ±0.54 °C inex vivoandin vivo,respectively.Significance.It is concluded that non-invasive US thermometry via backscattered energies at high frequencies can be used for real-time monitoring and control of hyperthermia treatments with acceptable accuracy. This provides a foundation for an US mediated drug delivery system.

Scatter radiation levels in X-ray rooms during chest radiography.

This research focused on the determination of scatter radiation levels in x-ray rooms during chest radiography. 108 patients were examined. Four x-ray machines (A, B, C, and D) were used during the research from three centers. Three positions were considered in this study; position Q just beside the (Bucky stand), position R, which is 150 cm from the left of the Bucky stand towards the door and position T, 200 cm from the Bucky stand to the radiographer's protective screen respectively. Two machines (A and B) from center 1 and one machine from center 2 (C) and one machine from center 3 (D). The body mass index (BMI) of the participants ranged from 20 to 25 kgm-2 with mean value of 23.97 kgm-2. The background radiation level was read using Radalert 100 m before any exposure, and the mean background level was 0.298 mR/h. The mean of the scatter radiation doses obtained from positions Q with respect to the four machines A, B, C, and D, were 0.109, 0.201, 0.204, 0.200 mR/h (9.166, 16.903, 17.156, 16.819 mSv/yr) and their standard deviations were ±0.052, ±0.053, ±0.064, and ±0.081 respectively. The results were comparable with previous studies. The study recommends staff education and training in determination of radiation levels for enhanced work safety.

Evaluation of radiation protection effectivity in a cardiac angiography room using visualized scattered radiation distribution.

In this study, we devised a radiation protection tool specifically designed for healthcare professionals and students engaged in cardiac catheterization to easily monitor and evaluate scattered radiation distribution across diverse C-arm angles and arbitrary physician associated staff positions-scrub nurse and technologist positions. In this study, scattered radiation distributions in an angiography room were calculated using the Monte Carlo simulation of particle and heavy ion transport code system (PHITS) code. Four visualizations were performed under different C-arm angles with and without radiation protection: (1) a dose profile, (2) a 2D cross-section, (3) a 3D scattered radiation distribution, and (4) a 4D scattered radiation distribution. The simulation results detailing the scattered radiation distribution in PHITS were exported in Visualization Toolkit format and visualized through the open-source visualization application ParaView for analysis. Visualization of the scattered dose showed that dose distribution depends on the C-arm angle and the x-ray machine output parameters (kV, mAs s-1, beam filtration) which depend upon beam angulation to the patient body. When irradiating in the posterior-anterior direction, the protective curtain decreased the dose by 62% at a point 80 cm from the floor, where the physician's gonads are positioned. Placing the protection board close to the x-ray tube reduced the dose by 24% at a location 160 cm from the floor, where the lens of the eye is situated. Notably, positioning the protection board adjacent to the physician resulted in a 95.4% reduction in incident air kerma. These visualization displays can be combined to understand the spread and direction of the scattered radiation distribution and to determine where and how to operate and place radiation protection devices, accounting for the different beam angulations encountered in interventional cases. This study showed that scatter visualization could be a radiation protection teaching aid for students and medical staff in angiography rooms.

Analysis of dose distribution around a computed tomography scanner in terms of exposure to scattered ionizing radiation of caregivers of pediatric patients.

OBJECTIVES: During computed tomography (CT), a large amount of ionizing radiation is emitted to ensure high quality of the obtained radiological image. This study measured the dose distribution around the CT scanner and the exposure of people staying near the CT scanner during the examination. MATERIAL AND METHODS: The measurements used an anthropomorphic phantom to assess human exposure to ionizing radiation. The probability of inducing leukemia and other cancers as a result of absorbing doses recorded around the CT device was also calculated. RESULTS: The highest exposure to scattered radiation in the proximity of the CT scanner is recorded at the gantry of the tomograph, i.e., 55.7 µGy, and the lowest, below lower detection limit of 6 µGy at the end of the diagnostic table. The whole-body detector placed on the anthropomorphic phantom located at the diagnostic table right next to the CT gantry recorded 59.5 µSv and at the end of the table 1.5 µSv. The average doses to the lenses in these locations were: 32.1 µSv and 2.9 µSv, respectively. CONCLUSIONS: The probability of induction of leukemia or other types of cancer is low, but the need for people to stay in the examination room during a CT examination should be limited to the necessary minimum. Int J Occup Med Environ Health. 2024;37(3):326-34.

A rotating beam-blocker method for cone beam CT scatter correction.

BACKGROUND: Cone beam CT (CBCT) is widely utilized in clinics. However, the scatter artifact degrades the CBCT image quality, hampering the expansion of CBCT applications. Recently, beam-blocker methods have been used for CBCT scatter correction and proved their high cost-effectiveness. PURPOSE: A rotating beam-blocker (RBB) method for CBCT scatter correction was proposed to complete scatter correction and image reconstruction within a single scan in both full- and half-fan scan scenarios. METHODS: The RBB consisted of two open regions and two blocked regions, and was designed as a centrosymmetric structure. The open and blocked projections could be alternatively obtained within one single rotation. The open projections were corrected with the scatter signal calculated from the blocked projections, and then used to reconstruct the 3D image via the Feldkamp-Davis-Kress algorithm. The performance of the RBB method was evaluated on head and pelvis phantoms in scenarios with and without a bowtie filter. The images obtained from nine repeated scans in each scenario were used to calculate the evaluation metrics including the CT number error, spatial nonuniformity (SNU) and contrast-to-noise ratio (CNR). RESULTS: For the head phantom, the CT number error was decreased to <5 after scatter correction from >200 HU before correction when scanned without a bowtie filter, and to <4 from >160 HU when scanned with a full bowtie filter. For the pelvis phantom, the CT number error was reduced to <12 after scatter correction from >250 HU before correction when scanned without a bowtie filter, and to <10 from >190 HU when scanned with a half bowtie filter. After scatter correction, the uniformity and contrast were both improved, resulting in an SNU of >79% decrease and CNR of >2 times increase, respectively. CONCLUSIONS: High-quality CBCT images could be obtained in a single scan after using the proposed RBB method for scatter correction, enabling more accurate image guidance for surgery and radiation therapy applications. With almost no time delay between the successive open and blocked projections, the RBB method could eliminate the motion-induced anatomical mismatches between the corresponding open and blocked projections and could find particular usefulness in thoracic and abdominal imaging.

Extracellular vesicle isolation and counting system (EVics) based on simultaneous tandem tangential flow filtration and large field-of-view light scattering.

Although the isolation and counting of small extracellular vesicles (sEVs) are essential steps in sEV research, an integrated method with scalability and efficiency has not been developed. Here, we present a scalable and ready-to-use extracellular vesicle (EV) isolation and counting system (EVics) that simultaneously allows isolation and counting in one system. This novel system consists of (i) EVi, a simultaneous tandem tangential flow filtration (TFF)-based EV isolation component by applying two different pore-size TFF filters, and (ii) EVc, an EV counting component using light scattering that captures a large field-of-view (FOV). EVi efficiently isolated 50-200 nm-size sEVs from 15 µL to 2 L samples, outperforming the current state-of-the-art devices in purity and speed. EVc with a large FOV efficiently counted isolated sEVs. EVics enabled early observations of sEV secretion in various cell lines and reduced the cost of evaluating the inhibitory effect of sEV inhibitors by 20-fold. Using EVics, sEVs concentrations and sEV PD-L1 were monitored in a 23-day cancer mouse model, and 160 clinical samples were prepared and successfully applied to diagnosis. These results demonstrate that EVics could become an innovative system for novel findings in basic and applied studies in sEV research.

Particle tracking, recognition and LET evaluation of out-of-field proton therapy delivered to a phantom with implants.

Objective.This study aims to assess the composition of scattered particles generated in proton therapy for tumors situated proximal to some titanium (Ti) dental implants. The investigation involves decomposing the mixed field and recording Linear Energy Transfer (LET) spectra to quantify the influence of metallic dental inserts located behind the tumor.Approach.A therapeutic conformal proton beam was used to deliver the treatment plan to an anthropomorphic head phantom with two types of implants inserted in the target volume (made of Ti and plastic, respectively). The scattered radiation resulted during the irradiation was detected by a hybrid semiconductor pixel detector MiniPIX Timepix3 that was placed distal to the Spread-out Bragg peak. Visualization and field decomposition of stray radiation were generated using algorithms trained in particle recognition based on artificial intelligence neural networks (AI NN). Spectral sensitive aspects of the scattered radiation were collected using two angular positions of the detector relative to the beam direction: 0° and 60°.Results.Using AI NN, 3 classes of particles were identified: protons, electrons & photons, and ions & fast neutrons. Placing a Ti implant in the beam's path resulted in predominantly electrons and photons, contributing 52.2% of the total number of detected particles, whereas for plastic implants, the contribution was 65.4%. Scattered protons comprised 45.5% and 31.9% with and without metal inserts, respectively. The LET spectra were derived for each group of particles identified, with values ranging from 0.01 to 7.5 keVµm-1for Ti implants/plastic implants. The low-LET component was primarily composed of electrons and photons, while the high-LET component corresponded to protons and ions.Significance.This method, complemented by directional maps, holds the potential for evaluating and validating treatment plans involving stray radiation near organs at risk, offering precise discrimination of the mixed field, and enhancing in this way the LET calculation.

Modelling of RBE differences in selected points within similar spread-out Bragg-peaks (SOBP) placed at superficial and deep water phantom locations in passively scattered beams but not in scanned pencil beams: A hypothesis.

PURPOSE: To model relative biological effectiveness (RBE) differences found in two studies which used spread-out Bragg-peaks (SOBP) placed at (a) superficial depth and (b) at the maximum range depth. For pencil beam scanning (PBS), RBE at similar points within the SOBP did not change between the two extreme SOBP placement depths; in passively scattered beams (PSB), high RBE values (typically 1.2-1.3) were found within superficially- placed SOBP but reduced to lower values (1-1.07) at similar points within the extreme-depth positioned SOBP. The dose, LET (linear energy transfer) distributions along each SOBP were closely comparable regardless of placement depth, but significant changes in dose rate occurred with depth in the PSB beam. METHODS: The equations used allow α and ß changes with falling dose rate (the converse to FLASH studies) in PSB, resulting in reduced α/ß ratios, compatible with a reduction in micro-volumetric energy transfer (the product of Fluence and LET), with commensurate reductions in RBE. The experimental depth-distances, positions within SOBP, observed dose-rates and radiosensitivity ratios were used to estimate the changes in RBE. RESULTS: RBE values within a 5 % tolerance limit of the experimental results for PSB were found at the deepest SOBP placement. No RBE changes were predicted for PBS beams, as in the published results. CONCLUSIONS: Enhanced proton therapy toxicity might occur with PBS when compared with PSB for deeply positioned SOBP due to the maintenance of higher RBE. Scanned pencil beam users need to be vigilant about RBE and further research is indicated.

Depolarization diagrams for circularly polarized light scattering for biological particle monitoring.

Significance: The depolarization of circularly polarized light (CPL) caused by scattering in turbid media reveals structural information about the dispersed particles, such as their size, density, and distribution, which is useful for investigating the state of biological tissue. However, the correlation between depolarization strength and tissue parameters is unclear. Aim: We aimed to examine the generalized correlations of depolarization strength with the particle size and wavelength, yielding depolarization diagrams. Approach: The correlation between depolarization intensity and size parameter was examined for single and multiple scattering using the Monte Carlo simulation method. Expanding the wavelength width allows us to obtain depolarization distribution diagrams as functions of wavelength and particle diameter for reflection and transparent geometries. Results: CPL suffers intensive depolarization in a single scattering against particles of various specific sizes for its wavelength, which becomes more noticeable in the multiple scattering regime. Conclusions: The depolarization diagrams with particle size and wavelength as independent variables were obtained, which are particularly helpful for investigating the feasibility of various particle-monitoring methods. Based on the obtained diagrams, several applications have been proposed, including blood cell monitoring, early embryogenesis, and antigen-antibody interactions.

A scattering-foil free electron beam to increase dose rate for total skin electron therapy (TSET).

BACKGROUND: Electron beams are used at extended distances ranging between 300 to 700 cm to uniformly cover the entirety of the patient's skin for total skin electron therapy (TSET). Even with electron beams utilizing the high dose rate total skin electron (HDTSe) mode from the Varian 23iX or TrueBeam accelerators, the dose rate is only 2500 cGy/min at source-to-surface distance (SSD) = 100 cm. At extended distances, the decrease in dose rate leads to long beam delivery times that can limit or even prevent the use of the treatment for patients who, in their weakened condition, may be unable to stand on their own for extended periods of time. Previously, to increase dose rate, a customized 6 MeV electron beam was created by removing the x-ray target, flattening filter, beam monitor chamber, and so forth. from the beam path (Chen, et at IJROBP 59, 2004) for TSET. Using this scattering-foil free (SFF) electron beam requires the treatment distance be extended to 700 cm to achieve dose uniformity from the single beam. This room size requirement has limited the widespread use of the 6 MeV-SFF beam. PURPOSE: This study explores an application of a dual-field technique with a 6 MeV-SFF beam to provide broad and uniform electron fields to reduce the treatment distances in order to overcome treatment room size limitations. METHODS: The EGSnrc system was used to generate incident beams. Gantry angles between 6 MeV-SFF dual-fields were optimized to achieve the similar patient skin dose distribution resulting from a standard 6 MeV-HDTSe dual-field configuration. The patient skin dose comparisons were performed based on the patient treatment setup geometries using dose-volume-histograms. RESULTS: Similar dose coverage can be achieved between 6 MeV-SFF and 6 MeV-HDTSe beams by reducing gantry angles between dual-field geometries by 8° and 7° at treatment distances of 400 and 500 cm, respectively. To achieve 95% mean dose to the first 5 mm of skin depth in the torso area, the mean dose to depths of 5-10 mm and 10-15 mm below the skin surface was 74% (74%) and 49% (50%) of the prescribed dose when using 6 MeV-SFF (6 MeV-HDTSe) beam, respectively. CONCLUSIONS: The 6 MeV-SFF electron beam is feasible to provide similar TSET skin dose coverage at SSD ≥ 400 cm using a dual-field technique. The dose rate of the 6 MeV-SFF beam is about 4 times that of current available 6 MeV-HDTSe beams at treatment distances of 400-500 cm, which significantly shortens the treatment beam-on time and makes TSET available to patients in weakened conditions.

Evaluation of Scatterer Parameters From Ultrasound Scattering Models Taking Into Account Scattering From Nuclei and Cells of Cell-Pellet Biophantoms and Ex Vivo Tumors.

The Quantitative Ultrasound backscatter coefficient provides the capability to evaluate tissue microstructure parameters. Tissue-based scatterer parameters are extracted using ultrasound scattering models. It is challenging to correlate ultrasound scatterer parameters of tissue structures from optical-measured histology, possibly because of inappropriate scattering models or the presence of multiple scatterers. The objective of this study is to pursue the quantification of pertinent scatterer parameters with scattering models that consider ultrasound scattering from nuclei and cells. The concentric sphere model (CSM) and the structure factor model adapted for two types of scatterers (SFM2) are evaluated for cell-pellet biophantoms and ex vivo tumors of four cell lines: 4T1, JC, LMTK, and MAT. The structure factor model (SFM) was used for comparison. CSM and SFM2 provided scatterer parameters closer to histology (lower relative errors) for nucleus and cell radii and volume fractions than SFM but were not always accompanied by lower dispersion of the scatterer distribution (lower coefficient of variation). CSM and SFM2 quantified cell and nucleus radius and volume fraction parameters with lower relative error compared to SFM. For tumors, CSM provided better results than SFM2.

Tutorial on methods for estimation of optical absorption and scattering properties of tissue.

Significance: The estimation of tissue optical properties using diffuse optics has found a range of applications in disease detection, therapy monitoring, and general health care. Biomarkers derived from the estimated optical absorption and scattering coefficients can reflect the underlying progression of many biological processes in tissues. Aim: Complex light-tissue interactions make it challenging to disentangle the absorption and scattering coefficients, so dedicated measurement systems are required. We aim to help readers understand the measurement principles and practical considerations needed when choosing between different estimation methods based on diffuse optics. Approach: The estimation methods can be categorized as: steady state, time domain, time frequency domain (FD), spatial domain, and spatial FD. The experimental measurements are coupled with models of light-tissue interactions, which enable inverse solutions for the absorption and scattering coefficients from the measured tissue reflectance and/or transmittance. Results: The estimation of tissue optical properties has been applied to characterize a variety of ex vivo and in vivo tissues, as well as tissue-mimicking phantoms. Choosing a specific estimation method for a certain application has to trade-off its advantages and limitations. Conclusion: Optical absorption and scattering property estimation is an increasingly important and accessible approach for medical diagnosis and health monitoring.

[Determination of fatty acid composition after saponification of common oil pharmaceutical excipients by supercritical fluid-evaporative light scattering method and its application in oil identification].

Oils and fats are commonly used in the pharmaceutical industry as solvents, emulsifiers, wetting agents, and dispersants, and are an important category of pharmaceutical excipients. Fatty acids with unique compositions are important components of oil pharmaceutical excipients. The Chinese Pharmacopoeia provides clear descriptions of the fatty acid types and limits suitable for individual oil pharmaceutical excipient. An unqualified fatty acid composition or content may indicate adulteration or deterioration. The fatty acid composition, as a key indicator for the identification and adulteration evaluation of oil pharmaceutical excipients, can directly affect the quality and safety of oil pharmaceutical excipients and preparations. Gas chromatography is the most widely used technique for fatty acid analysis, but it generally requires derivatization, which affects quantitative accuracy. Supercritical fluid chromatography (SFC), an environmentally friendly technique with excellent separation capability, offers an efficient method for detecting fatty acids without derivatization. Unlike other chromatographic methods, SFC does not use nonvolatile solvents (e. g., water) as the mobile phase, rendering it compatible with an evaporative light-scattering detector (ELSD) for enhanced detection sensitivity. However, the fatty acids in oil pharmaceutical excipients exist in the free and bound forms, and the low content of free fatty acids in these oil pharmaceutical excipients not only poses challenges for their detection but also complicates the determination of characteristic fatty acid compositions and contents. Moreover, the compositions and ratios of fatty acids are influenced by environmental factors, leading to interconversion between their two forms. In this context, saponification provides a simpler and faster alternative to derivatization. Saponification degrades oils and fats by utilizing the reaction between esters and an alkaline solution, ultimately releasing the corresponding fatty acids. Because this method is more cost effective than derivatization, it is a suitable pretreatment method for the detection of fatty acids in oil pharmaceutical excipients using the SFC-ELSD approach. In this study, we employed SFC-ELSD to simultaneously determine six fatty acids, namely, myristic acid, palmitic acid, stearic acid, arachidic acid, docosanoic acid, and lignoceric acid, in oil pharmaceutical excipients. Saponification of the oil pharmaceutical excipients using sodium hydroxide methanol solution effectively avoided the bias in the determination of fatty acid species and contents caused by the interconversion of fatty acids and esters. The separation of the six fatty acids was achieved within 12 min, with good linearity within their respective mass concentration ranges. The limits of detection and quantification were 5-10 mg/L and 10-25 mg/L, respectively, and the spiked recoveries were 80.93%-111.66%. The method proved to be sensitive, reproducible, and stable, adequately meeting requirements for the analysis of fatty acids in oil pharmaceutical excipients. Finally, the analytical method was successfully applied to the determination of six fatty acids in five types of oil pharmaceutical excipients, namely, corn oil, soybean oil, coconut oil, olive oil, and peanut oil. It can be combined with principal component analysis to accurately differentiate different types of oil pharmaceutical excipients, providing technical support for the rapid identification and quality control of oil pharmaceutical excipients. Thus, the proposed method may potentially be applied to the analysis of complex systems adulterated with oil pharmaceutical excipients.

Effect of backscatter radiation on the occupational eye-lens dose.

We quantified the level of backscatter radiation generated from physicians' heads using a phantom. We also evaluated the shielding rate of the protective eyewear and optimal placement of the eye-dedicated dosimeter (skin surface or behind the Pb-eyewear). We performed diagnostic X-rays of two head phantoms: Styrofoam (negligible backscatter radiation) and anthropomorphic (included backscatter radiation). Radiophotoluminescence glass dosimeters were used to measure the eye-lens dose, with or without 0.07-mm Pb-equivalent protective eyewear. We used tube voltages of 50, 65 and 80 kV because the scattered radiation has a lower mean energy than the primary X-ray beam. The backscatter radiation accounted for 17.3-22.3% of the eye-lens dose, with the percentage increasing with increasing tube voltage. Furthermore, the shielding rate of the protective eyewear was overestimated, and the eye-lens dose was underestimated when the eye-dedicated dosimeter was placed behind the protective eyewear. We quantified the backscatter radiation generated from physicians' heads. To account for the effect of backscatter radiation, an anthropomorphic, rather than Styrofoam, phantom should be used. Close contact of the dosimeter with the skin surface is essential for accurate evaluation of backscatter radiation from physician's own heads. To assess the eye-lens dose accurately, the dosimeter should be placed near the eye. If the dosimeter is placed behind the lens of the protective eyewear, we recommend using a backscatter radiation calibration factor of 1.2-1.3.

Impact of scatter radiation on spectral quantification performance of first- and second-generation dual-layer spectral computed tomography.

OBJECTIVE: To assess the impact of scatter radiation on quantitative performance of first and second-generation dual-layer spectral computed tomography (DLCT) systems. METHOD: A phantom with two iodine inserts (1 and 2 mg/mL) configured to intentionally introduce high scattering conditions was scanned with a first- and second-generation DLCT. Collimation widths (maximum of 4 cm for first generation and 8 cm for second generation) and radiation dose levels were varied. To evaluate the performance of both systems, the mean CT numbers of virtual monoenergetic images (MonoEs) at different energies were calculated and compared to expected values. MonoEs at 50  versus 150 keV were plotted to assess material characterization of both DLCTs. Additionally, iodine concentrations were determined, plotted, and compared against expected values. For each experimental scenario, absolute errors were reported. RESULTS: An experimental setup, including a phantom design, was successfully implemented to simulate high scatter radiation imaging conditions. Both CT scanners illustrated high spectral accuracy for small collimation widths (1 and 2 cm). With increased collimation (4 cm), the second-generation DLCT outperformed the earlier DLCT system. Further, the spectral performance of the second-generation DLCT at an 8 cm collimation width was comparable to a 4 cm collimation on the first-generation DLCT. A comparison of the absolute errors between both systems at lower energy MonoEs illustrates that, for the same acquisition parameters, the second-generation DLCT generated results with decreased errors. Similarly, the maximum error in iodine quantification was less with second-generation DLCT (0.45  and 0.33 mg/mL for the first and second-generation DLCT, respectively). CONCLUSION: The implementation of a two-dimensional anti-scatter grid in the second-generation DLCT improves the spectral quantification performance. In the clinical routine, this improvement may enable additional clinical benefits, for example, in lung imaging.

The impact of X-ray scatter correction software on abdomen radiography in terms of image quality and radiation dose.

INTRODUCTION: The conventional anti-scatter grid is widely used in X-ray radiography to reduce scattered X-rays, but it increases patient dose. Scatter-correction software offers a dose-reducing alternative by correcting for scattered X-rays without a physical grid. Grids and software correction are necessary to reduce scatter radiation and improve image quality especially for the large body parts. The scatter correction can be beneficial in situations where the use of grid is challenging. The implementation of grids and advanced software correction techniques is imperative to ensure that radiographic images maintain high levels of clarity, contrast, and resolution, and ultimately facilitating more accurate diagnoses. This study compares image quality and radiation dose for abdomen exams using scatter correction software and physical grids. METHODS: An anthropomorphic phantom (abdomen) underwent imaging with varying fat and lean tissue layers and body mass index (BMI) configurations. Imaging parameters included 70 kVp tube voltage, 110 cm SID, and Automatic Exposure Control (AEC) both lateral and central chambers. AP abdomen X-ray projections were acquired with and without an anti-scatter grid, and scatter correction software was applied. Image quality was assessed using contrast to noise ratio (CNR) and signal to noise ratio (SNR) metrics. The tube current mAs was considered an exposure factor that affected radiation dose and was used to compare the VG software and physical grid. Radiation dose was measured using Dose Area Products (DAP). The effective dose was estimated using Monte Carlo simulation-PCXMC software. Paired t-tests were used to investigate the image quality difference between the Gridless and VG software, Gridless and PG, and VG software and PG approaches. For the DAP and effective dose, paired t-test was used to investigate the difference between VG software and PG. RESULTS: Images acquired with a grid had the highest mean CNR (71.3 ± 32) compared to Gridless (50 ± 33.8) and scatter correction software (59.3 ± 37.9). The mean SNR of the grid images was (82.7.3 ± 38.9), which is 18% higher than the scatter correction software images (70.4 ± 36.7) and 29% higher than in the Gridless images (62.9.3 ± 34). The mean DAP value was reduced by 81% when the scatter correction software was used compared to the grid (mean: 65.4 µGy.m2 and 338.2 µGy.m2, respectively) with a significant difference (p = 0.001). Scatter correction software resulted in a lower effective dose compared to physical grid use, (mean difference± SD = -0.3 ± 0.18 mSv) with a significant difference (P = 0.02). CONCLUSION: Scatter correction software reduced the radiation dose required but images employing a grid yielded higher CNR and SNR. However, the radiation dose reduction might affect the image quality to a level that impacts the diagnostic information available. Thus, further research needs to be conducted to optimise the use of the scatter correction software. IMPLICATION FOR PRACTICE: Objectively, X-ray scatter correction software might be promising in conditions where a grid cannot be applied.

Antibody-labeled gold nanoparticle based resonance Rayleigh scattering detection of S100B.

Traumatic brain injury (TBI) is a sudden brain injury due to an external force that causes a large number of deaths and permanent disabilities every year. S100B has been recognized as a potential objective quantitative biomarker for screening the prognosis of TBI and severe head injury. In this article, an anti-S100B monoclonal antibody was immobilized on cysteamine (Cy) functionalized gold nanoparticles (AuNPs) by EDC-NHS chemistry, which enabled S100B resonance Rayleigh scattering (RRS) detection based on antibody-labeled gold nanoparticles. The prepared conjugates were characterized by ultraviolet-visible spectroscopy (UV-vis), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Based on the specific binding of the antibody and antigen, the RRS intensities at 381 nm and 541 nm wavelengths were significantly enhanced, and thus a dual wavelength overlapping resonance Rayleigh scattering (DWO-RRS) method was established. The scattering intensity of the two overlapping peaks was proportional to the concentration of S100B in the range of 0.05-4.5 ng mL-1 with a detection limit of 0.002 ng mL-1. The proposed DWO-RRS method is time-saving, simple, sensitive, and can be used to determine the concentration of S100B in human serum with satisfactory results, which has a promising application in the early diagnosis of TBI.

Label-Free Light Scattering Imaging with Purified Brownian Motion Differentiates Small Extracellular Vesicles in Cell Microenvironments.

Small extracellular vesicles (sEVs) are heterogeneous biological nanoparticles (NPs) with wide biomedicine applications. Tracking individual nanoscale sEVs can reveal information that conventional microscopic methods may lack, especially in cellular microenvironments. This usually requires biolabeling to identify single sEVs. Here, we developed a light scattering imaging method based on dark-field technology for label-free nanoparticle diffusion analysis (NDA). Compared with nanoparticle tracking analysis (NTA), our method was shown to determine the diffusion probabilities of a single NP. It was demonstrated that accurate size determination of NPs of 41 and 120 nm in diameter is achieved by purified Brownian motion (pBM), without or within the cell microenvironments. Our pBM method was also shown to obtain a consistent size estimation of the normal and cancerous plasma-derived sEVs without and within cell microenvironments, while cancerous plasma-derived sEVs are statistically smaller than normal ones. Moreover, we showed that the velocity and diffusion coefficient are key parameters for determining the diffusion types of the NPs and sEVs in a cancerous cell microenvironment. Our light scattering-based NDA and pBM methods can be used for size determination of NPs, even in cell microenvironments, and also provide a tool that may be used to analyze sEVs for many biomedical applications.

The effect of electron backscatter and charge build up in media on beam current transformer signal for ultra-high dose rate (FLASH) electron beam monitoring.

Objective.Beam current transformers (BCT) are promising detectors for real-time beam monitoring in ultra-high dose rate (UHDR) electron radiotherapy. However, previous studies have reported a significant sensitivity of the BCT signal to changes in source-to-surface distance (SSD), field size, and phantom material which have until now been attributed to the fluctuating levels of electrons backscattered within the BCT. The purpose of this study is to evaluate this hypothesis, with the goal of understanding and mitigating the variations in BCT signal due to changes in irradiation conditions.Approach.Monte Carlo simulations and experimental measurements were conducted with a UHDR-capable intra-operative electron linear accelerator to analyze the impact of backscattered electrons on BCT signal. The potential influence of charge accumulation in media as a mechanism affecting BCT signal perturbation was further investigated by examining the effects of phantom conductivity and electrical grounding. Finally, the effectiveness of Faraday shielding to mitigate BCT signal variations is evaluated.Main Results.Monte Carlo simulations indicated that the fraction of electrons backscattered in water and on the collimator plastic at 6 and 9 MeV is lower than 1%, suggesting that backscattered electrons alone cannot account for the observed BCT signal variations. However, our experimental measurements confirmed previous findings of BCT response variation up to 15% for different field diameters. A significant impact of phantom type on BCT response was also observed, with variations in BCT signal as high as 14.1% when comparing measurements in water and solid water. The introduction of a Faraday shield to our applicators effectively mitigated the dependencies of BCT signal on SSD, field size, and phantom material.Significance.Our results indicate that variations in BCT signal as a function of SSD, field size, and phantom material are likely driven by an electric field originating in dielectric materials exposed to the UHDR electron beam. Strategies such as Faraday shielding were shown to effectively prevent these electric fields from affecting BCT signal, enabling reliable BCT-based electron UHDR beam monitoring.

In Vivo Validation of an In Situ Calibration Bead as a Reference for Backscatter Coefficient Calculation.

OBJECTIVE: The study described here was aimed at assessing the capability of quantitative ultrasound (QUS) based on the backscatter coefficient (BSC) for classifying disease states, such as breast cancer response to neoadjuvant chemotherapy and quantification of fatty liver disease. We evaluated the effectiveness of an in situ titanium (Ti) bead as a reference target in calibrating the system and mitigating attenuation and transmission loss effects on BSC estimation. METHODS: Traditional BSC estimation methods require external references for calibration, which do not account for ultrasound attenuation or transmission losses through tissues. To address this issue, we used an in situ Ti bead as a reference target, because it can be used to calibrate the system and mitigate the attenuation and transmission loss effects on estimation of the BSC. The capabilities of the in situ calibration approach were assessed by quantifying consistency of BSC estimates from rabbit mammary tumors (N = 21). Specifically, mammary tumors were grown in rabbits and when a tumor reached ≥1 cm in size, a 2 mm Ti bead was implanted in the tumor as a radiological marker and a calibration source for ultrasound. Three days later, the tumors were scanned with an L-14/5 38 array transducer connected to a SonixOne scanner with and without a slab of pork belly placed on top of the tumors. The pork belly acted as an additional source of attenuation and transmission loss. QUS parameters, specifically effective scatterer diameter (ESD) and effective acoustic concentration (EAC), were calculated using calibration spectra from both an external reference phantom and the Ti bead. RESULTS: For ESD estimation, the 95% confidence interval between measurements with and without the pork belly layer was 6.0, 27.4 using the in situ bead and 114, 135.1 with the external reference phantom. For EAC estimation, the 95% confidence intervals were -8.1, 0.5 for the bead and -41.5, -32.2 for the phantom. These results indicate that the in situ bead method has reduced bias in QUS estimates because of intervening tissue losses. CONCLUSION: The use of an in situ Ti bead as a radiological marker not only serves its traditional role but also effectively acts as a calibration target for QUS methods. This approach accounts for attenuation and transmission losses in tissue, resulting in more accurate QUS estimates and offering a promising method for enhanced disease state classification in clinical settings.