Delivery Parameters Research Articles

Determining the Relationship between Delivery Parameters and Ablation Distribution for Novel Gel Ethanol Percutaneous Therapy in Ex Vivo Swine Liver.

Ethyl cellulose-ethanol (ECE) is emerging as a promising formulation for ablative injections, with more controllable injection distributions than those from traditional liquid ethanol. This study evaluates the influence of salient injection parameters on forces needed for infusion, depot volume, retention, and shape in a large animal model relevant to human applications. Experiments were conducted to investigate how infusion volume (0.5 mL to 2.5 mL), ECE concentration (6% or 12%), needle gauge (22 G or 27 G), and infusion rate (10 mL/h) impacted the force of infusion into air using a load cell. These parameters, with the addition of manual infusion, were investigated to elucidate their influence on depot volume, retention, and shape (aspect ratio), measured using CT imaging, in an ex vivo swine liver model. Force during injection increased significantly for 12% compared to 6% ECE and for 27 G needles compared to 22 G. Force variability increased with higher ECE concentration and smaller needle diameter. As infusion volume increased, 12% ECE achieved superior depot volume compared to 6% ECE. For all infusion volumes, 12% ECE achieved superior retention compared to 6% ECE. Needle gauge and infusion rate had little influence on the observed depot volume or retention; however, the smaller needles resulted in higher variability in depot shape for 12% ECE. These results help us understand the multivariate nature of injection performance, informing injection protocol designs for ablations using gel ethanol and infusion, with volumes relevant to human applications.

Use of cervical traction for managing neck pain: A cross-sectional survey of physiotherapists in India

BackgroundNeck pain remains the fourth leading cause of disability and work loss, and a multimodal treatment approach is effective in reducing neck pain and disability. PurposeThe purpose of this study is to examine the use of cervical traction for managing neck pain by Physiotherapists in India, including how and when the traction is used, the modes and parameters of traction, any additional interventions given with traction, and the influence of professional demographic characteristics in decision making in traction usage. Study designA cross-sectional survey. MethodologyA random sample of approximately 2500 musculoskeletal physiotherapists was surveyed, and the data was presented in a descriptive form. Chi-square analyses were used to identify the association between responders’ qualifications and traction usage. ResultsFrom the total physiotherapist approached 18.52% (n = 463) responses were obtained, and 62% (n = 287) respondents reported that they would use traction in their clinical practice. Out of 92.3% of responders indicated using traction for radiculopathy, 78.7% of respondents used traction for patients with neck pain without radiculopathy. It is used as a combination therapy by 58.8% for radiculopathy and 52.2% for stiffness. There was no association between the responder's qualification and traction usage (χ2 = 0.707, p = 0.40). Traction is used in combination with other physiotherapeutic techniques. ConclusionTraction use was consistent with the proposed criteria identifying patients likely to benefit. However, disregarding current guidelines, physiotherapists also use traction for non-radicular neck pain. Various traction delivery modes and parameters were used within a comprehensive plan of care incorporating multiple interventions.

Prevalence of depression among pregnant women and its correlation with the choice of delivery method.

Caesarean section is usually limited to cases where natural vaginal delivery is not possible or poses a serious risk to the foetus and mother. Psychological health of mothers is likely to play an important role in the method of delivery. This study aims to investigate the prevalence of depression in pregnant women and its relationship with the choice of delivery method and other demographic parameters. In this descriptive cross-sectional study, 250 mothers referring to the hospitals of Shahid Beheshti University of Medical Sciences, Tehran, Iran, were selected, and their demographic information and level of depression was collected using a questionnaire. Statistical analysis was conducted to evaluate the correlation between depression, method of delivery and other associated parameters. Among 250 pregnant women, 225 (90%) had no depression, 25 (10%) had mild depression and no moderate or severe depression was reported in any pregnant mother. Also, 146 (58.4%) were willing to have a caesarean section and 104 (41.6%) wanted to have a normal delivery. The choice of delivery method was not significantly associated with depression. Analyzes showed that increasing maternal age is associated with a greater tendency to caesarean delivery. The incidence and higher depression scores of mothers showed a significant association with the history of previous abortions. Although in this study no significant association was observed between depression in pregnant mothers and the choice delivery, due to the high prevalence of caesarean section in the country and its progression to higher percentages, it seems that the design and implementation of effective programs and interventions is required.

PUBLIC-PRIVATE PARTNERSHIP PROCUREMENT TRANSPORT INFRASTRUCTURE DELIVERY: ASSESSING THE MANAGERIAL CAPABILITIES OF PUBLIC-SECTOR ORGANIZATIONS IN AFRICA

The lingering imbalance between infrastructural services demand and supply poses serious threats to the fiscal budget balance from contingent liabilities of African countries. Despite the increasing private investment commitments and adoption of public-private partnership procurement (PPP) options to address the widening infrastructure gaps in Africa, the failure in the delivery of public infrastructure projects is yet a common phenomenon. This study therefore examined the managerial capabilities of public-sector organizations (PSOs), who steer the provisions of public infrastructure, to investigate their readiness to achieve the value for money from private funding and the benefits of PPP options. The study conducted a self-study structured questionnaire survey on professionals in PSOs in Africa, particularly Nigeria, who have been directly involved in the delivery of public infrastructure projects via PPP. The professionals were purposively sampled and the primary data obtained was subjected to descriptive and inferential analysis. The study revealed that the PSOs have internalized about 41 PPP-capabilities for the delivery of public infrastructure projects. Up to 40 PPP-capabilities were exhibited on an average score (41-60%) level, with mean score (MS) value range of 3.13 ≤ MS ≤ 3.70, for the public projects procured. The study established the existence of significant interdependence of p < 0.001, which indicated sufficient correlation between 31 PPP-capabilities and explained the 10 main components of managerial capabilities possessed by the PSOs. Some of the components clustered around public infrastructure planning and adaptability to PPP programme, project delivery parameters and control, suitable public infrastructure procurement knowledge, public policy awareness and innovation, and governance. The study provides information crucial for public infrastructure delivery success towards sustainable national economic recovery and development.

Implementation of a Stereoscopic Camera System for Clinical Electron Simulation and Treatment Planning

PurposeA 3D stereoscopic camera system developed by .decimal was commissioned and implemented into the clinic to improve the efficiency of clinical electron simulations. Capabilities of the camera allowed simulations to be moved from the treatment vault into any room with a flat surface that could accommodate patient positioning devices, eliminating the need for clinical patient setup timeslots on the treatment machine. This work describes the process used for these simulations and compares the treatment parameters determined by the system to those used in delivery. MethodsThe Decimal3D scanner workflow consisted of: scanning the patient surface; contouring the treatment area; determining gantry, couch, collimator, and source-to-surface distance (SSD) parameters for en face entry of the beam with sufficient clearance at the machine; and ordering custom electron cutouts when needed. Transparencies showing the projection of in-house library cutouts at various clinical SSDs were created to assist in choosing an appropriate library cutout. Data from 73 treatment sites were analyzed to evaluate the accuracy of the scanner-determined beam parameters for each treatment delivery. ResultsClinical electron simulations for 73 treatment sites, predominately keloids, were transitioned out of the LINAC vault using the new workflow. For all patients, gantry, collimator, and couch parameters along with SSD and cone size were determined using the Decimal3D scanner with 57% of simulations using library cutouts. Tolerance tables for patient setup were updated to allow differences of 10, 20 and 5 degrees for gantry, collimator and couch, respectively. Approximately 7% of fractions (N=181 total fractions) were setup outside of the tolerance table based on physician-direction during treatment. This reflects physician preference to adjust the LINAC rather than patient position during treatment setup. No scanner-derived plan was untreatable due to cutout shape inaccuracy or clearance issues. ConclusionClinical electron simulations were successfully transitioned out of the LINAC vault using the Decimal3D scanner without loss of setup accuracy as measured through machine parameter determination and electron cutout shape.

FLASH radiotherapy sparing effect on the circulating lymphocytes in pencil beam scanning proton therapy: impact of hypofractionation and dose rate

Purpose. The sparing effect of ultra-high dose rate (FLASH) radiotherapy has been reported, but its potential to mitigate depletion of circulating blood and lymphocytes (CL) has not been investigated in pencil-beam scanning-based (PBS) proton therapy, which could potentially reduce the risk of radiation-induced lymphopenia. Material and methods. A time-dependent framework was used to score the dose to the CL during the course of radiotherapy. For brain patients, cerebral vasculatures were semi-automatic segmented from 3T MR-angiography data. A dynamic beam delivery system was developed capable of simulating spatially varying instantaneous dose rates of PBS treatment plans, and which is based on realistic beam delivery parameters that are available clinically. We simulated single and different hypofractionated PBS intensity modulated proton therapy (IMPT) FLASH schemes using 600 nA beam current along with conventionally fractionated IMPT treatment plan at 2 nA beam current. The dosimetric impact of treatment schemes on CL was quantified, and we also evaluated the depletion in subsets of CL based on their radiosensitivity. Results. The proton FLASH sparing effect on CL was observed. In single-fraction PBS FLASH, just 1.5% of peripheral blood was irradiated, whereas hypofractionated FLASH irradiated 7.3% of peripheral blood. In contrast, conventional fractionated IMPT exposed 42.4% of peripheral blood to radiation. PBS FLASH reduced the depletion rate of CL by 69.2% when compared to conventional fractionated IMPT. Conclusion. Our dosimetric blood flow model provides quantitative measures of the PBS FLASH sparing effect on the CL in radiotherapy for brain cancer. FLASH Single treatment fraction offers superior CL sparing when compared to hypofractionated FLASH and conventional IMPT, supporting assumptions about reducing risks of lymphopenia compared to proton therapy at conventional dose rates. The results also indicate that faster conformal FLASH delivery, such as passive patient-specific energy modulation, may further enhance the sparing of the immune system.

Feasibility study of multiple-energy Bragg peak proton FLASH on a superconducting gantry with large momentum acceptance.

While the Bragg peak proton beam (BP) is capable of superior target conformity and organs-at-risk sparing than the transmission proton beam (TB), its efficacy in FLASH-RT is hindered by both a slow energy switching process and the beam current. A universal range shifter (URS) can pull back the high-energy proton beam while preserving the beam current. Meanwhile, a superconducting gantry with large momentum acceptance (LMA-SC gantry) enables fast energy switching. This study explores the feasibility of multiple-energy BP FLASH-RT on the LMA-SC gantry. A simultaneous dose and spot map optimization algorithm was developed for BP FLASH-RT treatment planning to improve the dose delivery efficiency. The URS was designed to be 0-27cm thick, with 1cm per step. BP plans using the URS were optimized using single-field optimization (SFO) and multiple-field optimization (MFO) for ten prostate cancer patients and ten lung cancer patients. The plan delivery parameters, dose, and dose rate metrics of BP plans were compared to those of TB plans using the parameters of the LMA-SC gantry. Compared to TB plans, BP plans significantly reduced MUs by 42.7% (P<0.001) with SFO and 33.3% (P<0.001) with MFO for prostate cases. For lung cases, the reduction in MUs was 56.8% (P<0.001) with SFO and 36.4% (P<0.001) with MFO. BP plans also outperformed TB plans by reducing mean normal tissue doses. BP-SFO plans achieved a reduction of 56.7% (P<0.001) for prostate cases and 57.7% (P<0.001) for lung cases, while BP-MFO plans achieved a reduction of 54.2% (P<0.001) for the prostate case and 40.0% (P<0.001) for lung cases. For both TB and BP plans, normal tissues in prostate and lung cases received 100.0% FLASH dose rate coverage(>40Gy/s). By utilizing the URS and the LMA-SC gantry, it is possible to perform multiple-energy BP FLASH-RT, resulting in better normal tissue sparing, as compared to TB plans.

The predictive value of hemogram parameters for early preterm delivery in pregnant women undergoing cervical cerclage.

This study aims to investigate the predictive value of hemogram parameters in early preterm delivery (32 gestational weeks and below) among pregnant women who have undergone cervical cerclage, based on cervical changes determined before the cerclage procedure. Between 2010 and 2020, a total of 161 patients underwent cervical cerclage. The participants were divided into three groups. Group 1 (n=92) consisted of pregnant women who underwent prophylactic cerclage. Group 2 (n=31) included those with cervical shortening (<5 mm) and/or dilation (≤3 cm). Group 3 (n=38) comprised pregnant women with cervical dilation >3 cm. Each group was further divided based on delivery weeks, with a cutoff at 32 weeks. Demographic parameters and laboratory parameters were assessed. In Group 1, all hemogram parameters showed no significant differences between deliveries below and above 32 weeks. In Group 2, the neutrophil-to-lymphocyte ratio value before cerclage was higher in the early preterm delivery group (p=0.002), with a cutoff value of 4.75 in receiver operating characteristic analysis. In Group 3, the white blood cell value before cerclage was higher in the early preterm delivery group (p=0.005), with a cutoff value of 13.05×103/μL in receiver operating characteristic analysis. The use of hemogram parameters to predict early preterm delivery in pregnant women undergoing prophylactic cerclage is not appropriate. However, neutrophil-to-lymphocyte ratio value can predict early preterm delivery when cervical dilation is 3 cm or less and/or cervical shortening is 5 mm or less. When cervical dilation exceeds 3 cm, the white blood cell value is more appropriate for predicting early preterm delivery.

A Novel Educational Approach for Safe Endodontic Syringe Irrigation: A Randomized Controlled In Vitro Study.

Syringe irrigation, commonly used for delivering sodium hypochlorite (NaOCl) during root canal treatment, requires careful handling to prevent NaOCl extrusion into periapical tissues. This randomized controlled in vitro study aimed to quantify syringe plunger forces exerted by dental undergraduates and to assess the impact of an educational intervention on adherence to safe irrigant delivery parameters. Fifty-two undergraduates performed syringe irrigation at three intervals: baseline (T1), after two weeks (T2), and after 12 weeks (T3). At T1, irrigation was conducted without prior educational intervention, while at T2, it was preceded by an intervention. The educational intervention involved a short video highlighting safe irrigation practices, including plunger force and time recommendations for syringe irrigation. At T3, the undergraduates were randomly allocated to two groups: One received a repeated intervention, while the other did not. Syringe irrigation was performed on a 3D-printed tooth using two side-vented cannulas: one of 25 Gauge (G) and another of 30 G. A syringe equipped with a force sensor recorded the plunger forces. Based on earlier research, plunger forces exceeding 10 Newtons (N) for the 25 G cannula and 40 N for the 30 G cannula were deemed critical. The data were subjected to descriptive statistical analyses. Overall, the mean of maximum values of plunger forces remained under 10 N for the 25 G and below 20 N for the 30 G cannulas, with only few measurements exceeding 40 N. Instances of surpassing the critical plunger force threshold were more common with the 25 G side-vented cannula than with the 30 G variant. At T3, the group that received the repeated educational intervention exhibited lower average maximum plunger forces for both types of cannulas compared with the group that did not receive the intervention. Integrating plunger force measurements with targeted educational interventions presents an effective approach for instructing undergraduates in the proper techniques of syringe irrigation. The findings suggest that, generally, undergraduates do not apply excessive plunger forces that could risk apical irrigant extrusion. The implementation of repeated educational interventions has been shown to decrease the plunger forces exerted by undergraduates, underscoring its effectiveness in fostering safe endodontic irrigation.

MIDOS: a novel stochastic model towards a treatment planning system for microsphere dosimetry in liver tumors.

Transarterial radioembolization (TARE) procedures treat liver tumors by injecting radioactive microspheres into the hepatic artery. Currently, there is a critical need to optimize TARE towards a personalized dosimetry approach. To this aim, we present a novel microsphere dosimetry (MIDOS) stochastic model to estimate the activity delivered to the tumor(s), normal liver, and lung. MIDOS incorporates adult male/female liver computational phantoms with the hepatic arterial, hepatic portal venous, and hepatic venous vascular trees. Tumors can be placed in both models at user discretion. The perfusion of microspheres follows cluster patterns, and a Markov chain approach was applied to microsphere navigation, with the terminal location of microspheres determined to be in either normal hepatic parenchyma, hepatic tumor, or lung. A tumor uptake model was implemented to determine if microspheres get lodged in the tumor, and a probability was included in determining the shunt of microspheres to the lung. A sensitivity analysis of the model parameters was performed, and radiation segmentectomy/lobectomy procedures were simulated over a wide range of activity perfused. Then, the impact of using different microspheres, i.e., SIR-Sphere®, TheraSphere®, and QuiremSphere®, on the tumor-to-normal ratio (TNR), lung shunt fraction (LSF), and mean absorbed dose was analyzed. Highly vascularized tumors translated into increased TNR. Treatment results (TNR and LSF) were significantly more variable for microspheres with high particle load. In our scenarios with 1.5 GBq perfusion, TNR was maximum for TheraSphere® at calibration time in segmentectomy/lobar technique, for SIR-Sphere® at 1-3 days post-calibration, and regarding QuiremSphere® at 3 days post-calibration. This novel approach is a decisive step towards developing a personalized dosimetry framework for TARE. MIDOS assists in making clinical decisions in TARE treatment planning by assessing various delivery parameters and simulating different tumor uptakes. MIDOS offers evaluation of treatment outcomes, such as TNR and LSF, and quantitative scenario-specific decisions.

IMPLEMENTING GRIEF SERVICES FOR OLDER ADULTS: TRANSLATING SURVEY FINDINGS INTO TARGETED PROGRAMMING

Abstract This presentation will identify and describe the team’s ongoing efforts in actuating the Implementation phase of the EPIS Framework. Evidence-based strategies include formulating a multidisciplinary implementation team, organizing purveyor and intermediary support, and developing a Monitoring, Evaluation, and Learning (MEL) plan. We will highlight the ways in which survey findings were disseminated to the general public and organizational leaders, such as presenting result summaries at city council meetings and in local newspaper articles. The challenges of negotiating survey findings into cohesive program implementation will be discussed, as well as management strategies towards age-related gaps in the implementation process that had not been identified previously. Recent program launches and the ways in which survey results directly informed their delivery will also be reviewed, namely, a free educational guest-speaker event for which over 700 community members attended and a grief-support holiday vigil hosted at a local long-term care facility. This presentation will also review considerations for the project’s next steps as it continues to hone its program delivery parameters and eventually enters into the last EPIS phase, Sustainment. Specific foci will include deciding the long-term methods of quality assurance evaluation and program adaptations to revolving community bereavement needs.

Optimized gravity-driven intranasal drop administration delivers significant doses to the ostiomeatal complex and maxillary sinus.

Chronic and allergic rhinosinusitis impacts approximately 12% of the global population. Challenges in rhinosinusitis treatment include paranasal sinus inaccessibility and variability in delivery efficiency among individuals. This study addresses these challenges of drug delivery by developing a high-efficiency, low-variability protocol for nasal drop delivery to the ostiomeatal complex (OMC) and maxillary sinus. Patient-specific nasal casts were dissected to reveal the configurations of conchae and meatus, providing insights into anatomical features amendable for sinus delivery. Fluorescent dye-enhanced videos visualized the dynamic liquid translocation in transparent nasal casts, allowing real-time assessment and quick adjustment to delivery parameters. Dosimetry to the OMC and maxillary sinus were quantified as drop count and mass using a precision scale. Key delivery factors, including the device type, formulation, and head-chin orientation, were systematically investigated in a cohort of ten nasal casts. Results show that both the squeeze bottle and soft-mist nasal pump yielded notably low doses to the OMC with high variability, and no dose from these two devices was detected within the maxillary sinuses. In contrast, the proposed approach, which included a curved nozzle surpassing the nasal valve and leveraged gravity-driven liquid translocation along the lateral nasal wall, delivered significant doses to the OMC and maxillary sinus. Iterative experimentations identified the optimal head tilt to be 40° and chin tilt to be° from the lateral recumbent position. Statistical analyses established the drop count required for effective OMC/sinus delivery. The proposed delivery protocol holds the potential to enhance chronic rhinosinusitis treatment outcomes with low variability. The dual role of nasal anatomy in posing challenges and offering opportunities highlights the need for future investigations using diverse formulations in a larger cohort of nasal models.

Dosimetric Comparison of Commonly Used Volumetric Modulated Arc Therapy Field Arrangements Based on Flattening Filter-Free Beams for Synchronous Bilateral Breast Carcinoma Radiation Therapy

Dosimetric Comparison of Commonly Used Volumetric Modulated Arc Therapy Field Arrangements Based on Flattening Filter-Free Beams for Synchronous Bilateral Breast Carcinoma Radiation Therapy

Real-time motion-including dose estimation of simulated multi-leaf collimator-tracked magnetic resonance-guided radiotherapy.

Real-time dose estimation is a key-prerequisite to enable online intra-fraction treatment adaptation in magnetic resonance (MR)-guided radiotherapy (MRgRT). It is an essential component for the assessment of the dosimetric benefits and risks of online adaptive treatments, such as multi-leaf collimator (MLC)-tracking. We present a proof-of-concept for a software workflow for real-time dose estimation of MR-guided adaptive radiotherapy based on real-time data-streams of the linac delivery parameters and target positions. A software workflow, combining our in-house motion management software DynaTrack, a real-time dose calculation engine that connects to a research version of the treatment planning software (TPS) Monaco (v.6.09.00, Elekta AB, Stockholm, Sweden) was developed and evaluated. MR-guided treatment delivery on the Elekta Unity MR-linac was simulated with and without MLC-tracking for three prostate patients, previously treated on the Elekta Unity MR-linac (36.25Gy/five fractions). Three motion scenarios were used: no motion, regular motion, and erratic prostate motion. Accumulated monitor units (MUs), centre of mass target position and MLC-leaf positions, were forwarded from DynaTrack at a rate of 25Hz to a Monte Carlo (MC) based dose calculation engine which utilises the research GPUMCD-library (Elekta AB, Stockholm, Sweden). A rigid isocentre shift derived from the selected motion scenarios was applied to a bulk density-assigned session MR-image. The respective electron density used for treatment planning was accessed through the research Monaco TPS. The software workflow including the online dose reconstruction was validated against offline dose reconstructions. Our investigation showed that MC-based real-time dose calculations that account for all linac states (including MUs, MLC positions and target position) were infeasible, hence states were randomly sampled and used for calculation as follows; Once a new linac state was received, a dose calculation with 106 photons was started. Linac states that arrived during the time of the ongoing calculation were put into a queue. After completion of the ongoing calculation, one new linac state was randomly picked from the queue and assigned the MU accumulated from the previous state until the last sample in the queue. The queue was emptied, and the process repeated throughout treatment simulation. On average 27% (23%-30%) of received samples were used in the real-time calculation, corresponding to a calculation time for one linac state of 148ms. Median gamma pass rate (2%/3mm local) was 100.0% (99.9%-100%) within the PTV volume and 99.1% (90.1%-99.4.0%) with a 15% dose cut off. Differences in PTVDmean , CTVDmean , RectumD2% , and BladderD2% (offline-online, % of prescribed dose) were below 0.64%. Beam-by-beam comparisons showed deviations below 0.07Gy. Repeated simulations resulted in standard deviations below 0.31% and 0.12Gy for the investigated volume and dose criteria respectively. Real-time dose estimation was successfully performed using the developed software workflow for different prostate motion traces with and without MLC-tracking. Negligible dosimetric differences were seen when comparing online and offline reconstructed dose, enabling online intra-fraction treatment decisions based on estimates of the delivered dose.

Interplay Effect of Splenic Motion for Total Lymphoid Irradiation in Pediatric Proton Therapy.

(1) Background: The most significant cause of an unacceptable deviation from the planned dose during respiratory motion is the interplay effect. We examined the correlation between the magnitude of splenic motion and its impact on plan quality for total lymphoid irradiation (TLI); (2) Methods: Static and 4D CT images from ten patients were used for interplay effect simulations. Patients' original plans were optimized based on the average CT extracted from the 4D CT and planned with two posterior beams using scenario-based optimization (±3 mm of setup and ±3% of range uncertainty) and gradient matching at the level of mid-spleen. Dynamically accumulated 4D doses (interplay effect dose) were calculated based on the time-dependent delivery sequence of radiation fluence across all phases of the 4D CT. Dose volume parameters for each simulated treatment delivery were evaluated for plan quality; (3) Results: Peak-to-peak splenic motion (≤12 mm) was measured from the 4D CT of ten patients. Interplay effect simulations revealed that the ITV coverage of the spleen remained within the protocol tolerance for splenic motion, ≤8 mm. The D100% coverage for ITV spleen decreased from 95.0% (nominal plan) to 89.3% with 10 mm and 87.2% with 12 mm of splenic motion; (4) Conclusions: 4D plan evaluation and robust optimization may overcome problems associated with respiratory motion in proton TLI treatments. Patient-specific respiratory motion evaluations are essential to confirming adequate dosimetric coverage when proton therapy is utilized.

Quality assurance for mixed electron-photon beam radiation therapy using treatment log files and MapCHECK.

Mixed photon-electron beam radiotherapy (MBRT) is a technique that combines the use of both photons and electrons in one single treatment plan to exploit their advantageous and complimentary characteristics. Compared to other photon treatment modalities, it has been shown that the MBRT technique contributes to better target coverage and organ-at-risk (OAR) sparing. However, the use of combined photons and electrons in one delivery makes the technique more complex and a well-established quality assurance (QA) protocol for MBRT isessential. To investigate the feasibility of using MapCHECK and log file-dose reconstruction for MBRT plan verification and to recommend a patient-specific quality assurance (PSQA) protocol forMBRT. MBRT plans were robustly optimized for five soft-tissue sarcoma (STS) patients. Each plan comprised step-and-shoot deliveries of a six MV photon beam and a combination of five electron beam energies at an SAD of 100 cm. The plans were delivered to the MapCHECK device with collapsed gantry angle and the 2D dose distributions at the detector depth were measured. To simulate the expected dose distribution delivered to the MapCHECK, a MapCHECK computational phantom was modeled in EGSnrc based on vendor-supplied blueprint information. The dose to the detectors in the model was scored using the DOSXYZnrc user code. The agreement between the measured and the simulated dose distribution was evaluated using 2D gamma analysis with a gamma criterion of 3%/2 mm and a low dose threshold of 10%. One of the plans was selected and delivered with a rotating gantry angle for trajectory log file collection. To evaluate the potential interlinac and intralinac differences, the plan was delivered repeatedly on three linacs. From the collected log files, delivery parameters were retrieved to recalculate the 3D dose distributions in the patient's anatomy with DOSXYZnrc. The recalculated mean dose to the clinical target volume (CTV) and OARs from all deliveries were computed and compared with the planned dose in terms of percentage difference. To validate the accuracy of log file-based QA, the log file-recalculated dose was also compared with filmmeasurement. The agreement of the total dose distribution between the MapCHECK measurement and simulation showed gamma passing rates of above 97% for all five MBRT plans. In the log file-dose recalculation, the difference between the recalculated and the planned dose to the CTV and OARs was below 1% for all deliveries. No significant inter- or intralinac differences were observed. The log file-dose had a gamma passing rate of 98.6% compared to filmmeasurement. Both the MapCHECK measurements and log file-dose recalculations showed excellent agreement with the expected dose distribution. This study demonstrates the potential of using MapCHECK and log files as MBRT QAtools.

Optimal parameters for rapid (invisible) frequency tagging using MEG

Frequency tagging has been demonstrated to be a useful tool for identifying representational-specific neuronal activity in the auditory and visual domains. However, the slow flicker (<30 Hz) applied in conventional frequency tagging studies is highly visible and might entrain endogenous neuronal oscillations. Hence, stimulation at faster frequencies that is much less visible and does not interfere with endogenous brain oscillatory activity is a promising new tool. In this study, we set out to examine the optimal stimulation parameters of rapid frequency tagging (RFT/RIFT) with magnetoencephalography (MEG) by quantifying the effects of stimulation frequency, size and position of the flickering patch. Rapid frequency tagging using flickers above 50 Hz results in almost invisible stimulation which does not interfere with slower endogenous oscillations; however, the signal is weaker as compared to tagging at slower frequencies so certainty over the optimal parameters of stimulation delivery are crucial. The here presented results examining the frequency range between 60 Hz and 96 Hz suggest that RFT induces brain responses with decreasing strength up to about 84 Hz. In addition, even at the smallest flicker patch (2°) focally presented RFT induces a significant and measurable oscillatory brain signal (steady state visual evoked potential/field, SSVEP/F) at the stimulation frequency (66 Hz); however, the elicited response increases with patch size. While focal RFT presentation elicits the strongest response, off-centre presentations do generally mainly elicit a measureable response if presented below the horizontal midline. Importantly, the results also revealed considerable individual differences in the neuronal responses to RFT stimulation. Finally, we discuss the comparison of oscillatory measures (coherence and power) and sensor types (planar gradiometers and magnetometers) in order to achieve optimal outcomes. Based on our extensive findings we set forward concrete recommendations for using rapid frequency tagging in human cognitive neuroscience investigations.

Development and analysis of the loading characteristic of accumulate fuel injection system Common Rail of the engine 50 RT-flex

The object of research are hydrodynamical processes in fuel delivery system of marine diesel engine of type RT-flex with accumulate fuel injection system of type Common Rail. The problem, being solved, is maintenance of an effective operation of the specified diesel engines due to perfection work of their fuel equipment. The results of simulation modeling of the injection process by accumulator fuel delivery system Common Rail of the 50RT-flex engine are presented. On the basis of the functional diagram of system, a calculation model has been compiled that provides a description of the operation of the systems main blocks. The load characteristic of the fuel equipment is built in the traditional version – the dependence of the fuel delivery parameters from the engine load at a constant speed. For the system under consideration, the control element is the valve assembly connecting the injection control unit (ICU) with injectors. The parameters of the load characteristic in this study are modes with a constant engine speed n=124 rpm and a change in the opening angle of the control valve in the range – jv=6.6–14.4 °CA. The parameters of the devices that largely determine the characteristics of the fuel delivery and the quality of the working processes of a diesel engine are considered in more details. Such an element of the system is ICU, the working body of which is the dosing piston. The main parameters of its operation when delivering fuel are the magnitude and speed of the stroke. For the load characteristics in the accepted range of the valve control valve opening angle jv from 6.6 to 14.4 °CA (2.18 times), the piston stroke was hp=4.29–8.61 mm (2.0 more). In this case, the dependence of hp on jv is linear. Area of use of the data received during research, ship crews and the shore services providing operation of vessels are. A material is applied in process of high school and is already used in various educational forms. The given researches are useful to developers and builders of marine diesel engines of a considered class.

Modeling ultra-high dose rate electron and proton FLASH effect with the physicochemical approach

Objective. A physicochemical model built on the radiochemical kinetic theory was recently proposed in (Labarbe et al ) to explain the FLASH effect. We performed extensive simulations to scrutinize its applicability for oxygen depletion studies and FLASH-related experiments involving both proton and electron beams. Approach. Using the dose and beam delivery parameters for each FLASH experiment, we numerically solved the radiochemical rate equations comprised of a set of coupled nonlinear ordinary differential equations to obtain the area under the curve (AUC) of radical concentrations. Main results. The modeled differences in AUC induced by ultra-high dose rates appeared to correlate well with the FLASH effect. (i) For the whole brain irradiation of mice performed in (Montay-Gruel et al ), the threshold dose rate values for memory preservation coincided with those at which AUC started to decrease much less rapidly. (ii) For the proton pencil beam scanning FLASH of (Cunningham et al ), we found linear correlations between radicals’ AUC and the biological endpoints: TGF-β1, leg contracture and plasma level of cytokine IL-6. (iii) Compatible with the findings of the proton FLASH experiment in (Kim et al ), we found that radicals’ AUC at the entrance and mid-Spread-Out Bragg peak regions were highly similar. In addition, our model also predicted ratios of oxygen depletion G-values between normal and UHDR irradiation similar to those observed in (Cao et al ) and (El Khatib et al ). Significance. Collectively, our results suggest that the normal tissue sparing conferred by UHDR irradiation may be due to the lower degree of exposure to peroxyl and superoxide radicals. We also found that the differential effect of dose rate on the radicals’ AUC was less pronounced at lower initial oxygen levels, a trait that appears to align with the FLASH differential effect on normal versus tumor tissues.

Kadınlar Vajinal Doğumu Neden Tercih Etmez?: Türkiye Örneği

Objective: It was aimed to determine the reasons why women did not prefer Vaginal Delivery. &#x0D; Methods: This is research cross-sectional in descriptive type. The STROBE statement was used in the planning, implementation, and reporting of the study design. The research was carried out in a private hospital in Turkey, between April 2021-2022. It was conducted with 347 women aged 18-45 years who were not pregnant, and who wanted Caesarean section for their planned pregnancy. The data were obtained by "Obtaining Information Form" and the "The Vaginal Delivery Preference Inventory-TVDPI". &#x0D; Results: The TVDPI score was found to be correlated with education status, previous delivery, the effect of obtaining information about cesarean section, and the effect of witnessing vaginal delivery. It was determined that a one-unit increase in the age and number of the delivery parameters would lead to a decrease of 0.025 points in the probability of affecting TVDPI scores. Women's education level, previous delivery, and obtaining information about delivery patterns affect their delivery preferences. &#x0D; Conclusions: The education level of women, their previous births and their knowledge about the mode of delivery affect their birth preferences. In the choice of birth, the woman should be considered as a whole with her environment and the culture in which she lives.