Numerical Methods for Balance Laws with Space Dependent Flux: Application to Radiotherapy Dose Calculation

The present work is concerned with the derivation of numerical methods to approximate the radiation dose in external beam radiotherapy. To address this issue, we consider a moment approximation of radiative transfer, closed by an entropy minimization principle. The model under consideration is governed by a system of hyperbolic equations in conservation form supplemented by source terms. The main difficulty coming from the numerical approximation of this system is an explicit space dependence in the flux function. Indeed, this dependence will be seen to be stiff and specific numerical strategies must be derived in order to obtain the needed accuracy. A first approach is developed considering the 1D case, where a judicious change of variables allows to eliminate the space dependence in the flux function. This is not possible in multi-D. We therefore reinterpret the 1D scheme as a scheme on two meshes, and generalize this to 2D by alternating transformations between separate meshes. We call this procedure projection method. Several numerical experiments, coming from medical physics, illustrate the potential applicability of the developed method.     

Vectorial Kinetic Relaxation Model with Central Velocity. Application to Implicit Relaxations Schemes

We apply flux vector splitting (FVS) strategy to the implicit kinetic schemesfor hyperbolic systems. It enables to increase the accuracy of the method compared toclassical kinetic schemes while still using large time steps compared to the characteristic speeds of the problem. The method also allows to tackle multi-scale problems, suchas the low Mach number limit, for which wave speeds with large ratio are involved. Wepresent several possible kinetic relaxation schemes based on FVS and compare themon one-dimensional test-cases. We discuss stability issues for this kind of method.     

Photon Dose Calculation Method Based on Monte Carlo Finite-Size Pencil Beam Model in Accurate Radiotherapy

This study mainly focused on the key technologies, the photon dose calculation based on the Monte Carlo Finite-Size Pencil Beam (MCFSPB) model in the Accurate Radiotherapy System (ARTS). In the MCFSPB model, the acquisition of pencil beam kernel is one of the most important technologies. In this study, by analyzing the demerits of the clinical pencil beam dose calculation methods, a new pencil beam kernel model was developed based on the Monte Carlo (MC) simulation and the technology of medical accelerator energy spectrum reconstruction, which greatly improved the accuracy of calculated result. According to the axial symmetry principle, only part of simulation results were used for the data of pencil beam kernel, which greatly reduced the data quantity of the pencil beam and reduced calculated time. Based on the above studies, the MCFSPB method was designed and implemented by the Visual C++ development tool. With several tests including the comparisons among the American Association of Physicists in Medicine (AAPM) No. 55 Report sample and the ion chamber measurement of lung-simulating inhomogeneous phantom in clinical treatment plan, the results showed that the maximum error of most calculated point was less than 0.5% in the homogeneous phantom and less than 3% in the heterogeneous phantom. This method met the clinical criteria, and would be expected to be used as a fast and accurate dose engine for clinic TPS.     

杂交瘤细胞代谢流分析模型及其在批式培养中的应用

通过物料衡算和线性规划方法建立了进行代谢流分析的数学模型，并首次应用于批式培养过程.分析结果表明，细胞对葡萄糖等底物的代谢效率很低，细胞对谷氨酰胺等氨基酸浓度的变化响应迟缓，在底物充裕的迟滞期及谷氨酰胺限制条件下的代谢效率高于对数生长期.另外限制谷氨酰胺等氨基酸进入能量代谢，既可减少氨的积累，也会减少乳酸的生成.     

Animal Model for Evaluating Bone Repair with and without Adjunctive Hyperbaric Oxygen Therapy (HBO): Comparing Dose Schedules

The effect of hyperbaric oxygen (HBO) on the healing of standardized metaphyseal defects in the cortices of rat femurs was studied. The question was whether a known total amount of HBO given twice a day (BID) would have a different effect than once a day (QD) treatments. A microvascular casting technique was developed whereby vessel ingrowth at the repair site could be monitored using scanning electron microscopy (SEM). Bone repair morphology was evaluated by light microscopy (LM) and various tissue components were quantified by histomorphometry (HM). Animals were sacrificed I, 2, 3, or 5 weeks postoperatively. SEM revealed that endosteal bone ingrowth was totally responsible for the repair of the cortical defects. Moreover, endosteal vessel ingrowth did not differ between controls and either group of HBO treated animals. LM displayed enchondral ossification in controls and BID treated animals and a pronounced osteoclastic activity in the latter group throughout the repair process. By contrast the QD treated group healed by primary ossification. Judged by the HM data, QD treatment appeared to accelerate bone repair and vessel ingrowth compared to controls, while BID treatment seemed to retard these processes.     

Rapid Tracheal Intubation with Rocuronium: A probability Approach to Determining Dose

Background: Rapid tracheal intubation with rocuronium has not been studied using a probability-based approach. The authors aimed to predict doses of rocuronium giving 90% and 95% probability of intubation within 60 s and to estimate their durations of action.

Methods: After premedication with midazolam, 2 mg, anesthesia was induced in 80 subjects with fentanyl, 2 [micro sign]g/kg, followed 3 min later by propofol, 2 mg/kg. Patients received randomly rocuronium, 0.0, 0.4, 0.8, or 1.2 mg/kg (n = 20/dose). Laryngoscopy began 40 s later, aiming for intubation at 60 s, and conditions were graded perfect, acceptable, or unacceptable, with the first two conditions being successful intubation. Anesthesia was maintained with isoflurane 0.5-1.0% (end-tidal) and fentanyl. Duration of action was time until reappearance of the first tactile train-of-four response. The dose versus fraction of patients with successful intubation was analyzed by logistic regression. Doses giving 90% and 95% (D (90) and D95) probability of successful intubation were calculated.

Results: Intubation was successful in 7, 11, 18, and 19 patients in the 0.0, 0.4, 0.8, and 1.2 mg/kg groups, respectively. The D90 and D95 doses (95% confidence limits in parentheses) were 0.83 (0.59-1.03) and 1.04 (0.76-1.36) mg/kg, respectively. Estimated time until first tactile train-of-four response after D90 and D95 doses was 32 and 46 min, respectively.     

Assessment of Heat Flux Prediction Capabilities of Residual Distribution Method: Application to Atmospheric Entry Problems

In the present contribution we evaluate the heat flux prediction capabilities of second-order accurate Residual Distribution (RD ) methods in the context of atmospheric (re-)entry problems around blunt bodies. Our departing point is the computation of subsonic air flows (with air modeled either as an inert ideal gas or as chemically reacting and possibly out of thermal equilibrium gas mixture) around probe-like geometries, as those typically employed into high enthalpy wind tunnels. We confirm the agreement between the solutions obtained with the RD method and the solutions computed with other Finite Volume (FV ) based codes.However, a straightforward application of the same numerical technique to hypersonic cases involving strong shocks exhibits severe deficiencies even on a geometry as simple as a 2D cylinder. In an attempt to mitigate this problem, we derive new variants of RD schemes. A comparison of these alternative strategies against established ones allows us to derive a diagnose for the shortcomings observed in the traditional RD schemes.     

Radiotherapy for nonfunctioning pituitary adenomas: from conventional to modern stereotactic radiation techniques

The initial management of nonfunctioning pituitary macroadenomas (NFAs) is usually surgery; however, a significant proportion of NFAs may require further treatment. Radiotherapy is currently used in patients with residual tumour and achieves excellent long-term control, but there are concerns about potential late toxicity. Stereotactic radiotherapy, both in the form of radiosurgery or fractionated stereotactic radiotherapy, has been developed as a more accurate technique of irradiation with more precise tumour localization and consequently a reduction in the volume of normal tissue, particularly the brain, irradiated to high radiation doses. A review of the literature suggests that new radiation techniques offer safe and effective treatment for recurrent or residual pituitary adenomas; however longer follow-up is necessary to confirm the excellent tumour control and the potential reduction of long-term radiation toxicity. Currently, radiotherapy has an important role in patients with residual or progressive disease after surgery. Patients with small or no residual tumours after surgery may generally continue on a policy of surveillance without immediate irradiation, in order to avoid the potential toxicity of treatment.     

健康信念模式在尿路造口患者行为改变中的应用研究

目的探讨健康信念模式在尿路造口患者健康教育中的实施效果。方法将84例尿路造口患者随机分为两组各42例。干预组以健康信念模式为指导进行为期4个月的干预,对照组给予常规健康教育与随访。结果干预后3、6个月干预组并发症发生率显著低于对照组(均P0.01),干预组健康知识、自我效能评分显著优于对照组(均P0.01)。结论健康信念模式用于健康教育,加深患者对造口护理知识的认识和领悟,主动改变不良生活习惯,自觉提高对治疗的依从性,有效控制危险因素,提高患者自我管理能力及降低造口相关并发症。     

Coping with Technological Disaster: An Application of the Conservation of Resources Model to the Exxon Valdez Oil Spill

One hundred twenty-five commercial fishers in Cordova, Alaska, completed a mailed survey regarding current mental health functioning 6 years after the Exxon Valdez oil spill. Economic and social impacts of the oil spill and coping and psychological functioning (modified Coping Strategies Scales, Symptom Checklist 90-R) were measured. Multiple regression was used to test the utility of the Conservation of Resources stress model for explaining observed psychological symptoms. Current symptoms of depression, anxiety, and Posttraumatic Stress Disorder were associated with conditions resource loss and avoidant coping strategies. The Conservation of Resources model provided a framework for explaining psychological impacts of the oil spill. Future research is needed to identify factors related to recovery.     

Prometheus Payment Model: Application to Hip and Knee Replacement Surgery

The Prometheus Payment Model offers a potential solution to the failings of the current fee-for-service system and various forms of capitation. At the core of the Prometheus model are evidence-informed case rates (ECRs), which include a bundle of typical services that are informed by evidence and/or expert opinion as well as empirical data analysis, payment based on the severity of patients, and allowances for potentially avoidable complications (PACs) and other provider-specific variations in payer costs. We outline the methods and findings of the hip and knee arthroplasty ECRs with an emphasis on PACs. Of the 2076 commercially insured patients undergoing hip arthroplasty in our study, PAC costs totaled $7.8 million (14% of total costs; n = 699 index PAC stays). Similarly, PAC costs were $7.8 million (14% of total costs; n = 699 index PAC stays). Similarly, PAC costs were 12.7 million (14% of total costs; n = 897 index PAC stays) for 3403 patients undergoing knee arthroplasty. By holding the providers clinically and financially responsible for PACs, and by segmenting and quantifying the type of PACs generated during and after the procedure, the Prometheus model creates an opportunity for providers to focus on the reduction of PACs, including readmissions, making the data actionable and turn the waste related to PAC costs into potential savings.     

Directional $mathcal{H}^2$ Compression Algorithm: Optimisations and Application to a Discontinuous Galerkin BEM for the Helmholtz Equation

This study aimed to specialise a directional $mathcal{H}^2(mathcal{D}mathcal{H}^2)$ compression to matrices arising from the discontinuous Galerkin (DG) discretisation of the hypersingularequation in acoustics. The significant finding is an algorithm that takes a DG stiffness matrix and finds a near-optimal $mathcal{D}mathcal{H}^2$ approximation for low and high-frequencyproblems. We introduced the necessary special optimisations to make this algorithmmore efficient in the case of a DG stiffness matrix. Moreover, an automatic parametertuning strategy makes it easy to use and versatile. Numerical comparisons with a classical Boundary Element Method (BEM) show that a DG scheme combined with a $mathcal{D}mathcal{H}^2$ gives better computational efficiency than a classical BEM in the case of high-order finite elements and $hp$ heterogeneous meshes. The results indicate that DG is suitablefor an auto-adaptive context in integral equations.     

针对性护理在早期乳腺癌保乳术后调强放疗患者中的应用效果

探讨给予早期乳腺癌保乳术后调强放疗患者针对性护理的效果。方法 选取2022年2月- 12月于我院行早期乳腺癌保乳术后调强放疗的102例患者为研究对象,采用随机数字表法分为对照组和观 察组,每组51例。对照组给予常规护理,观察组在对照组基础上给予针对性护理,比较两组生命质量及护 理满意度。结果 观察组干预后身体健康、社会/家庭状况、情感状况、功能状况、附加关注评分均高于对 照组（P ＜0.05）;观察组护理满意度为88.24%,高于对照组的66.67%（P ＜0.05）。结论 针对性护理在早 期乳腺癌保乳术后调强放疗患者中的应用效果确切,可有效提升乳腺癌患者的生命质量,有利于提高护理 满意度。