Development and experimental in vivo validation of mathematical modeling of laser coagulation

Most clinical procedures using the laser are based on thermal laser-tissue interactions. The treatment often consists of inducing damage of given degree and extent by heating the tissue. The aim of this study was to develop a model called HELIOS. The ability of HELIOS to predict thermal coagulation was evaluated by comparison with in vivo experimental results. Conversion of laser light in tissue was studied using the beam-broadening model. Temperature was described by the heat conduction equation solved using the finite difference method. The tissue dena-turation was modeled by the Henriques equation leading to the determination of the damage coefficient ω. For a given set of laser and tissue parameters, HELIOS makes a graphic representation of coagulation necrosis and temperature evolution in tissue. HELIOS was validated by experimental studies in vivo on rat liver using a CW Nd:YAG laser, a CO₂ laser, and an argon laser. For given sets of laser parameters, temperature measurements were performed using an infrared camera. Histological examinations were carried out on samples to quantify the depth of coagulation necrosis. Experimental data obtained in vivo were compared with those calculated using HELIOS and similar sets of parameters. The difference between the predicted temperature evolution on tissue surface and that measured by the infrared camera was < 5°C in all cases. The difference between the predicted coagulation necrosis depth and the corresponding experimental one was < 10%. In conclusion, HELIOS allows good prediction of tissue temperature and coagulation necrosis. © 1994 Wiley-Liss, inc.     

Boundary Ambiguity in Parents With Chronically Ill Children: Integrating Theory and Research

Abstract: This article integrates theory and research related to boundary ambiguity in parents of children with a chronic health condition. We propose that boundary ambiguity is a risk factor for psychological distress in these parents. Clinical applications and a case example highlight how boundary ambiguity can be assessed and managed in clinical settings by professionals working with parents with chronically ill children. Questions are provided for assessing boundary ambiguity in clinical and research settings, and implications for research are discussed.     

Controlling for occasion-specific effects when assessing the test–retest reliability of self-report health questionnaires

OBJECTIVE: This study proposes a method for self-report health questionnaires to adjust test-retest reliability for changes during the test-retest interval based on an external measure, and to distinguish such changes from random response errors. METHODS: In our application, eighty participants completed the Symptoms of Illness Checklist (SIC) on two occasions, two weeks apart, immediately before interviews given on each occasion by one of two physicians in a crossover design. The physician interview scores served as external measures, and structural equation modeling was used to estimate the parameters of a model that corrected for the occasion-specific effect of participants' responses using information from the interviews. RESULTS: Correcting for changes in symptoms during the test-retest interval increased SIC test-retest reliability from .744 to .804 and significantly improved model fit (chi2(diff)(1) = 30.78, p < .001). CONCLUSIONS: The results suggest methods that can improve the evaluation of self-report health questionnaire test-retest reliability by identifying changes using an external measure, and distinguishing these from random response errors; these increased the estimated SIC test-retest reliability and indicated that the SIC was indeed able to measure changes over the studied time interval. This method can be applied across a broad range of questionnaires.     

Effect of concomitant food intake on absorption kinetics of fenoldopam (SK&F 82526) in healthy volunteers

Summary Eight healthy volunteers participated in an open crossover study to assess the effect of a standardised meal on the systemic availability of a single oral dose of fenoldopam mesylate 100 mg. Subjects were studied on four separate occasions, twice fasting and twice fed in randomised, balanced order. Plasma and urine samples were obtained before and at regular intervals up to 25 h post dose. Measurement of fenoldopam (SK&F 82526) and its 8-sulphate metabolite (SK&F 87782) were by means of HPLC-EC analysis. Area under the plasma concentration time curve (AUC) and maximum detected plasma concentration (C_max) for fenoldopam and SK&F 87782 were significantly reduced whereas time to maximum concentration was significantly increased with food. Using AUC's for fenoldopam and SK&F 87782, mean relative bioavailabilities were 35% and 81% respectively under fed compared with fasting conditions. Twenty-four hour excretion of fenoldopam was significantly reduced with food, but excretion of SK&F 87782 was apparently unchanged. Mean relative bioavailabilities calculated from these data were 83% and 86% respectively. Relatively large inter-subject variability in AUC and C_max were seen, but intra-subject variability was not marked. Mild symptoms associated with vasodilation were reported on all study days.     

肿瘤潜隐期二阶段模型

从宫颈癌、大肠癌等病种的自然史抽象出一个具有时变伴随变量的潜隐期二阶段模型。潜隐期以正常状态为起点,疾病为终点;其前阶段可逆,后阶段不可逆;状态间转移速率因病人状况而异。用Markov过程描述并求解此模型,进而给出参数估计和假设检验方法。利用此模型基于江西省靖安县12年6轮宫颈癌筛查资料进行了自然史研究,并讨论了应用前景。     

Computation of Time-Constant Histograms from the Forced Expired Volume-Time Curves

An efficient BASIC program was established on Apple-Ⅱmicrocomputer with the CHESTAC-35F pulmonary function testing system tocalculate the time-constant histogram from the spirogram.By a set of analogousstudies,we confirmed that the recovered time-constant histogram was within onecompartment of the assumed one and that the root of mean square values of theresiduals between the experimental and model volume-time curves was 0.02.Infour healthy adult subjects,the mean value of time-constant histograms(TCx)hadthe variation coefficient 6.6％.The results show that our method is reliable andreproducible,and it can be used for clinical investigation.     

微波与X线联合辐射对人体血液系统的影响

本文调查了微波与X线同时接触工人49名(联合组)、单微波接触工人48名(微波组)以及两者均不接触的工人46名(对照组)。联合组和微波组工人的微波辐射剂量每日平均约300μw/cm~2,联合组工人接触的X线剂量,每年小于5rem。结果显示:联合组中性粒细胞ACP、AKP活性以及中性粒细胞核棘突出现率均较微波组和对照组明显增高(P<0.01),糖原含量则较其它两组明显下降(P<0.01)。调查表明,低强度微波与低剂量X线联合辐射比单独微波辐射对人体的潜在危害更大。因此,对雷达等发射设备周围的工作人员,除必要的微波防护外。同时需要对X线进行防护。     

脑动静脉畸形实验动物模型的建立

脑动静脉畸形是一种比较常见的严重威胁人们生命安全和生存质量的脑血管疾病，目前人们主要是通过尸体解剖以及CT、MRI等影像学的方法认识。近年来，学者们应用各种动物模型来研究脑动静脉畸形的血流动力学，病理生理学以及脑动静脉畸形栓塞材料的评估，栓塞后临床疗效评价，放射照射剂量对脑动静脉畸形的影响等。本文就脑动静脉畸形实验动物的常用种类，动物模型的建立方法以及动物模型的实际应用进行了综述。     

神经根慢性嵌压损伤的动物模型建立

目的：建立一种由自身骨性增生造成神经根慢性嵌压损伤的动物模型，为相关实验提供造模方法一方法：30只健康家猫，手术显露右侧C7、C8和L5、L6冲经根及其椎问孔内口，用牙髓钻破坏椎间孔周围骨皮质后，将“V”形松质骨块沿骨壁嵌于神经根通道的骨性管道内及侧隐窝后方，左侧做正常对照。在造模术前和术后第2、4、8、12、24周行磁刺激运动诱发电位(MEP)检测，每次随机选6只，4～5只行影像学检查，以确定神经根通道的狭窄程度和神经根受压状态，6只均做病理组织学检查和椎间孔截面积测量。结果：术后早期实验侧肢体出现行为异常：而后有不同程度肌萎缩；后期部分肢体远端出现溃疡。影像学检查随着嵌压时间延长．实验侧椎间孔骨痂增多，狭窄加重。神经根受压变形，椎间孔骨性截面积8周后明显减小，与对照侧比较有显著性差异。术后2周，神经根组织学检查主要表现为神经束膜、内膜的水肿。髓鞘肿胀；4周后发生节段性脱髓鞘：8周时神经轴突增粗、断裂，远端瓦勒氏变性；12周后变性冲经结构崩解、吸收，形成空洞：24周时整个神经干纤维化。术后4周时实验侧MEP开始出现潜伏期延长；8周时伴有波形分化不清；12周波幅明显下降：24周MEP的引出困难，部分电位消失。结论：采用椎问孔内自体松质骨植入，造成神经根慢性嵌压性损伤模型成功率高，操作简单，适用于脊柱各个节段，其损伤部位和形式与临床更为接近。     

从ECCE到Phaco的转变--核处理技术的实验研究

目的通过化学方法制成动物核性白内障模型,探讨相对能量复合指数(RECP)与角膜内皮细胞活性的关系。方法将5种化学物质注入晶状体,以透过黑白条纹的清晰程度判断晶状体混浊程度并分级。然后将实验眼球分为6组(Ⅰ组为对照组;Ⅱ-Ⅵ为实验组),行标准超声乳化白内障摘除手术。手术后立即取下角膜,作锥蓝-茜素红联合染色标本和扫描电镜标本。结果晶状体内注入甲醛、冰醋酸、无水乙醇、丙酮和苯扎溴铵均能形成晶状体混浊,其中:冰醋酸致晶状体混浊能力最弱,无水乙醇、丙酮次之,甲醛、苯扎溴铵最强。当RECP≤90时,锥蓝-茜素红双重染色和扫描电镜均表明角膜内皮细胞活性好,其形态和细胞联接均无改变。当RECP=120时,角膜内皮细胞形态尚正常,但是细胞联结和胞膜部分破坏。当RECP=150时,角膜内皮细胞严重损伤。结论用化学方法制作核性白内障模型供过渡训练使用是可行的。当RECP超过某一数值(>90)时,即与角膜内皮细胞的活性成负相关。