Experimental determination of the recombination correction factor kS for SNC 125c,SNC 350p and SNC 600c ionization chambers in pulsed photon beams

Accurate ionization chamber measurements of the absorbed dose to water require the correction of incomplete collection of charges created within the chamber volume. According to current dosimetry protocols such as the TRS-398 or the DIN 6800-2, incomplete charge collection is accounted for by the correction factor k_s, which can be determined numerically or experimentally. The method proposed by Burns & McEwen (Phys. Med. Biol., 1998) was used in this study to determine the coefficients γ and δ used for the calculation of the correction factor k_s of three ionization chambers, the SNC 125c, the SNC 600c and the SNC 350p (all Sun Nuclear Corp., Melbourne, Florida) for an absorbed dose to water range of 0.2 mGy to 1.6 mGy per pulse in pulsed photon beams. The shift of the effective point of measurement from the reference point Δz and the correction factor k_r were determined for the SNC 350p according to the draft DIN 6800-2:2019-07.     

Instrument-based Tests for Measuring Anterior Chamber Cells in Uveitis: A Systematic Review

ABSTRACT

Purpose

New instrument-based techniques for anterior chamber (AC) cell counting can offer automation and objectivity above clinician assessment. This review aims to identify such instruments and its correlation with clinician estimates.     

Carboxylesterase catalyzed 18O-labeling of carboxylic acid and its potential application in LC-MS/MS based quantification of drug metabolites

LC-MS quantification of drug metabolites is sometimes impeded by the availability of internal standards that often requires customized synthesis and/or extensive purification. Although isotopically labeled internal standards are considered ideal for LC-MS/MS based quantification, de novo synthesis using costly isotope-enriched starting materials makes it impractical for early stage of drug discovery. Therefore, quick access to these isotope-enriched compounds without chemical derivatization and purification will greatly facilitate LC-MS/MS based quantification. Herein, we report a novel ¹⁸O-labeling technique using metabolizing enzyme carboxylesterase (CES) and its potential application in metabolites quantification study. Substrates of CES typically undergo a two-step oxygen exchange with H₂¹⁸O in the presence of the enzyme, generating singly- and doubly-¹⁸O-labeled carboxylic acids; however, unexpected hydrolytic behavior was observed for three of the test compounds – indomethacin, piperacillin and clopidogrel. These unusual observations led to the discovery of several novel hydrolytic mechanisms. Finally, when used as internal standard for LC-MS/MS based quantification, these in situ labeled compounds generated accurate quantitation comparable to the conventional standard curve method. The preliminary results suggest that this method has potential to eliminate laborious chemical synthesis of isotope-labeled internal standards for carboxylic acid-containing compounds, and can be developed to facilitate quantitative analysis in early-stage drug discovery.     

学龄期儿童前房深度发育状况分析

目的了解7~14岁学龄期儿童前房深度发育情况。探索其与屈光度数间的关系。方法收集2012年6月至2014年6月眼科门诊7~14岁儿童为研究对象，共计521例（1042只眼）。采用IOLMaster人工晶状体生物测量仪测量各屈光参数，同时测量身高、体重。散瞳后验光测得静态屈光度。分析前房深度发育情况及不同屈光状态的学龄期儿童前房深度发育情况。结果（1）随着年龄的增长，7~14岁学龄期的儿童前房深度随之增长，差异具有统计学意义（P＜0.01）。同一年龄段儿童的左右眼之间的均值相近，且生长发育趋势相近（均P＞0.05）。（2）随着年龄的增长，男女的前房深度均逐渐增大，同一年龄段男性前房深度大于女性前房深度（均P＜0.01）。（3）儿童前房深度与身高正相关（P＜0.01）。（4）前房深度随近视度数增高而增大，低度近视组与中度近视组及高度近视组差异有统计学意义（P＜0.05）。结论学龄期儿童的前房深度的发育受到身高、性别及屈光度数的影响，与身高呈正相关，同一年龄段，男性前房深度大于女性。双眼前房深度发育同步。低中度近视的儿童前房深度增大。     

Platinum levels in various tissues of a patient who died 181 days after cisplatin overdosing determined by electrospray ionization mass spectrometry

Platinum (Pt) levels were determined in various tissues and body fluids obtained from a patient who died 181 days after cisplatin overdosing. The symptoms of cisplatin overdose, however, might have almost disappeared by day 40, and the patient’s death was ascribed to the recurrence of malignant lymphoma. Determination of Pt derived from cisplatin was performed by electrospray ionization mass spectrometry (ESI-MS) using silver (Ag) as internal standard. Pt and Ag complexed with diethyldithiocarbamate (DDC) in wetashed blood, and tissue solutions were extracted into isoamyl alcohol, and then acidified with oxalic acid. By injecting an aliquot of the isoamyl alcohol layer into a mass spectrometer in the direct flow injection mode, the quantitation was performed using the signals of Pt(DDC)₃ ⁺ and Ag(DDC)₂ ⁺ at m/z 639 and 403, respectively. The Pt levels ranged from 25ng/ml in blood to 2050ng/g wet weight in the liver of the patient, indicating that Pt remained at high levels in tissues, even after a period as long as 181 days after cisplatin overdosing.     

环境电离辐射体源表面剂量率的MC模拟计算及实验比较

目的　对核工业地质勘查计量站的 8个圆柱型环境电离辐射体源和两个本底模型上方不同高度处的空气吸收剂量率进行较为准确的定值。方法　采用蒙特卡罗软件MCNP ,对上述环境电离辐射体源和本底模型上方的空气吸收剂量率进行了模拟计算 ,采用 1台高气压电离室剂量率仪对各环境电离辐射体源和本底模型上方不同高度处的空气吸收剂量率进行了实测 ,模拟计算结果与实测结果以及其他工作者过去所作的剂量率测量和计算结果进行了比较。结果　MC模拟计算值与其他工作者得到的空气吸收剂量率理论值吻合较好 ,最大偏差小于 10 % ,一般偏差小于±5 %。结论　只要各种输入参数准确 ,采用MC模拟计算 ,可以得到辐射体源和本底模型上方不同高度处较准确 (3%不确定度 )的空气吸收剂量率模拟计算值。     

出血性玻璃体混浊行玻璃体切除术后假性前房积脓分析

目的介绍一种发生于玻璃体切除术后的非感染性前房积脓现象，即假性前房积脓。方法收集我中心收治的需行玻璃体切除术的连续病例１２５０例，其中各种原因引起的玻璃体积血４１８例。术后发生假性前房积脓者７例，均为玻璃体积血者。主要治疗方法是前房冲洗及其自然吸收。结果假性前房积脓发生于术后３～５天，呈泥沙样沉积，局部抗生素及激素加强治疗无效。眼内穿刺行涂片、细菌和真菌培养未发现病原体。患者无疼痛等自觉症状及刺激征。随访时３例视力在０．０５以上。结论玻璃体积血行玻璃体切除术后可能出现假性前房积脓，须与眼内感染相鉴别。     

人子宫内膜植入兔眼前房模型的研究

本实验成功地将人子宫内膜植入到１５只去卵巢新西兰雌兔的眼前房，并给每只兔外源补充雌二醇（Ｅ２）１００μｇ／ｄ和孕酮（Ｐ）８ｍｇ／ｄ。在内膜植入期间每只兔皮下注射总量为９ｍｇ的霉酚酸（ｍｙ－ｃｏｐｈｅｎｏｌｉｃａｃｉｄ）以防免疫排斥反应。在眼前房的人子宫内膜存活了２８．４４±８．６５天，兔血清Ｅ２和Ｐ的平均值分别为１６１．７１±１５．１３和３８．８８±７．４５ｐｍｏｌ／Ｌ。前房液中Ｅ２和Ｐ浓度在植入人子宫内膜前后分别为２４．８０±１６．５３和１７０９．２５±４７５．１０ｐｍｏｌ／Ｌ，２．００±０．５３和１２．２２±３．８１ｎｍｏｌ／Ｌ。树脂切片验证人子宫内膜植入兔眼前房第５天就能与虹膜附贴并有血管发生。来自巩膜的血管分布在子宫内膜周围。扫描电镜观察人子宫内膜分化成分泌细胞和纤毛细胞。植入人子宫内膜后，前房液的蛋白浓度高于植入前。可以证明该模型可用来研究人子宫内膜对药物的反应和通过对前房液的测量研究子宫内膜的分泌功能。