利用Barracuda系统测量医用CT剂量指数量值不确定度评定

目的为保证医用CT剂量指数量值的准确性,评定其不确定度。方法建立Barracuda系统10 cm长杆电离室测量CT剂量指数数学模型,分析不确定度来源,通过计算给出不确定度。结果相对扩展不确定度为6.5%。结论利用Bar-racuda系统测量医用CT剂量指数量值不确定度主要受测量系统不确定度、校准因子、层厚偏差等分量的影响。     

DR的应用质量检测

简要介绍了DR（digital radiology,数字化X射线摄影系统）的工作原理和性能特点,重点阐述了DR质量检测中几项主要技术指标的检测步骤和数据处理方法,并对检测中的常见问题进行了重点说明。     

Organochlorine pesticides in the tissues of the great barracuda (Sphyraena barracuda) (Waldbaum)

The abdominal fat of adult barracuda caught in Florida waters was analyzed for organochlorine pesticides. Of a total of 281 fish, 63 % had 5 to 760 g abdominal fat. The fat of 96 % of these fish contained DDT or one of its isomers or metabolites. Except for the smallest and largest fish, the ratio of total DDT in fat to kg body weight remained constant (0.08 to 0.11 mg/kg). During the spawning season, in addition to fat, certain organs and tissues of these fish were also analyzed. The highest pesticide concentrations were found in the fat. Assigning to the concentration of total DDT in abdominal fat a value of 10, the rating for the concentration of total DDT in the liver becomes approximately 1.1, in the pyloric cecum 1, in flesh 0.7, and for the fully developed gonads 0.5. It seems unlikely that larval barracuda are affected unfavorably by these low concentrations of DDT unless they are exceedingly sensitive to this compound. Since the quantity of abdominal fat and tissue pesticide concentrations were highest at the beginning and lowest during the height and end of the spawning season (and if this should apply to other fish species), then it can be concluded that spot-checking fish tissues for pesticides once or twice a year, more likely than not, provides misleading information with regard to pollution. Tissues and flesh of all barracuda were fed to cats, with no symptoms of ciguatera.This investigation was supported by U.S. Public Health Service grant No. 3 P01 ES00052-07 and 07S1/9001908 and Dept. of Commerce NOAA Sea Grant No. 2-35147.     

CT-SD16探测器辐射剂量测量原理和参数设定

目的 介绍了一种用半导体电离室测量多排CT辐射剂量的原理和方法,为完善我国现有医疗CT检测规范提供技术信息.方法 通过介绍X射线辐射剂量计Barracuda的测量原理和多排CT辐射剂量测量的参数设置依据,并结合在Philip Brilliance iCT 256机器上的应用实例,阐述了用半导体电离室的探测器测量多排CT辐射剂量的关键技术.结果 基于CT扫描参数合理设置探测器参数后,多排CT辐射剂量空间分布情况得以较好展示.100 mm长杆空气电离室的测量范围远小于多排CT线束覆盖范围,需要对多排CT辐射剂量测量方法和技术进行更新.结论 新型探测器有利于揭示多排CT辐射剂量的特性规律.     

Identification of slow and fast-acting toxins in a highly ciguatoxic barracuda (Sphyraena barracuda) by HPLC/MS and radiolabelled ligand binding.

A barracuda implicated in ciguatera fish poisoning in Guadeloupe was estimated to have an overall flesh toxicity of 15 MUg/g using mouse bioassay. A lipid soluble extract was separated into two toxic fractions, FrA and FrB, on a LH20 Sephadex column eluted with dichloromethane/methanol (1:1). When intraperitoneal injected into mice, FrA provoked symptoms characteristic of slow-acting ciguatoxins, whereas FrB produced symptoms indicative of fast-acting toxins (FAT). High performance liquid chromatography/mass spectrometry/radio-ligand binding (HPLC/MS/RLB) analysis confirmed the two fractions were distinct, because only a weak overlap of some compounds was observed. HPLC/MS/RLB analysis revealed C-CTX-1 as the potent toxin present in FrA, and two coeluting active compounds at m/z 809.43 and 857.42 in FrB, all displaying the characteristic pattern of ion formation for hydroxy-polyethers. Other C-CTX congeners and putative hydroxy-polyether-like compounds were detected in both fractions, however, the RLB found them inactive. C-CTX-1 accounted for > 90% of total toxicity in this barracuda and was confirmed to be a competitive inhibitor of brevetoxin binding to voltage-sensitive sodium channels (VSSCs) with a potency two-times lower than P-CTX-1. However, FAT active on VSSCs and < 900 Da were suspected to contribute to the overall toxicity.     

Use of two detection methods to discriminate ciguatoxins from brevetoxins: application to great barracuda from Florida Keys.

In Florida (USA), numerous cases of human ciguatera fish poisoning, as well as neurotoxic shellfish poisoning following consumption of local seafood products, have been reported. By using in parallel, the sodium channel receptor binding assay (RBA), and the ouabain/veratridine-dependent cytotoxicity assay (N2A assay), we established criteria to identify, detect, and quantify ciguatoxins in fish extracts, with a brevetoxin as internal standard. Results showed that the Caribbean ciguatoxin C-CTX-1 exhibited an 8-fold higher potency in the RBA than brevetoxins and, a 440 and 2300-fold higher potency in the N2A assay than PbTx-1 and PbTx-3, respectively. Moreover, a sensitivity comparison between assays revealed that the N2A assay was more sensitive (12-fold) for ciguatoxin analysis, whereas the RBA was more sensitive (3-24-fold) for brevetoxins analysis. Based on the relative potency between toxins and the opposite sensitivity of both assays we have used the RBA and the N2A assay to screen great barracuda (Sphyraena barracuda) collected from the Florida Keys for ciguatoxins and brevetoxins. Fish extract analysis showed a sodium channel-dependent activity consistent with the presence of ciguatoxins, and not brevetoxins. Among 40 barracudas analyzed, 60% contained ciguatoxin levels in their liver measurable by the N2A assay with the most toxic fish containing 2.1ppb C-CTX-1 equivalents.     

DR的应用质量检测

简要介绍了DR(digital radiology,数字化X射线摄影系统)的工作原理和性能特点,重点阐述了DR质量检测中几项主要技术指标的检测步骤和数据处理方法,并对检测中的常见问题进行了重点说明.