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1.
《Zeitschrift für medizinische Physik》2022,32(4):392-402
The aim of this study is to investigate the feasibility of manufacturing thin real-time relative dosimeters for clinical radiotherapy (RT) with potential applications for transmission monitoring in vivo dosimetry and pre-treatment dose verifications. Thin (≈1 μm) layers of a high sensitivity, wide bandgap semiconductor, the inorganic perovskite CsPbCl3, have been grown for the first time by magnetron sputtering on plastic substrates equipped with electrode arrays. Prototype devices have been tested in real-time configuration to evaluate the dose delivered by a 6 MV photon beam from a linear accelerator. Linearity of the charge with the dose has been verified over three order of magnitudes, linearity of the current signal with the dose rate has been also successfully tested in the range 0.5-4.3 Gy/min. The combination of high sensitivity per unit volume and wide bandgap provides high signal-to-noise ratios, up to 70, even at moderate applied voltages. The Schottky diode configuration allows the detector to operate without bias voltage (null bias).The blocking-barrier structure allows to confine the active volume within sub-millimetric sizes, a quite attractive feature in view to increase granularity and achieve the high spatial resolutions required in modern RT techniques. All the above-mentioned features indeed pave the way to a novel generation of flexible, transmission, real time dosimeters for clinical radiotherapy. 相似文献
2.
3.
Michael J. Root 《Calcified tissue international》1990,47(2):112-116
Summary The induction time for amorphous calcium phosphate (ACP) phase transformation was monitored at pH 7.4 and T=25°C with [Ca2+]0=[PO4]0=4.0×10−3 M, as a function of added crystal growth inhibitors Mg2+, Sr2+, Zn2+, pyrophosphate (PP), and tripolyphosphate (TPP). Metal ions increase the induction time for the initiation of the phase change
reaction in the order Zn2+<Sr2+<Mg2+. For polyphosphates it was observed that both PP and TPP are potent inhibitors with TPP more effective than PP as expected.
The combination of Mg2+ or Sr2+ and PP or TPP leads to a synergistic delay in the onset of the phase conversion. The greatest inhibition was observed for
Mg2+ and TPP. Reaction solutions containing 2.0×10−4 M Mg2+ and 4.0×10−5 M TPP resulted in a 90% increase in the induction time over what would be anticipated from an additive effect from these
species. 相似文献
4.
中药中金属元素的生化作用机理 总被引:3,自引:0,他引:3
机体内环境是一个多层次纵横交错的大系统 ,有一套复杂的调控体系 ,金属元素与此调控体系有密切联系。机体内所有复杂的生化反应都离不开酶 ,而金属元素有的是酶的辅助因子参与酶的组成 ,有的是酶的激活剂 ,是酶活性的主要调节者。深入研究中药中金属元素对酶活性的影响 ,将有利于提高药效。此外肾虚病人血清中金属元素与正常人相比有显著差异 ,若能比较准确地测得肾虚不同阶段的金属元素图谱 ,并结合中药中各金属元素含量的不同加以针对性地治疗 ,将对提高药物对疾病的治疗效果及延缓衰老有重要意义。 相似文献
5.
Computed tomography (CT) scans are often used for postoperative imaging in orthopedics. In the presence of metallic hardware, artifacts are generated, which can hamper visualization of the CT images, and also render the study ineffective for 3-D printing. Various solutions are available to minimize metal artifacts, and radiologists can employ these before or after processing the CT study. However, the orthopedic surgeon may be faced with situations where the metal artifacts were not addressed. To counter such problems, we present three do-it-yourself (DIY) techniques that can be used to manage metal artifacts. 相似文献
6.
根据超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性结构相似原理,作者首次提出金属卟啉化合物可作为SOD和CAT双功能模拟酶,并对合成的4 种金属卟啉[四-(对磺酸基苯基)卟啉铁、四-(对磺酸基苯基)卟啉铜、四-(对磺酸基苯基)卟啉锰、四-(对磺酸基苯基)卟啉钴]进行了仿SOD和CAT的部分生物学功能检测 .结果显示:核黄素-蛋氨酸光明法证实它们在10-5~10-6mol/L浓度范围内有清除O(*2)-的作用;分光光度法证实它们能催化H2O2 的分解,且分解率随浓度增大而增大;用小鼠肝匀浆法测定4种金属卟啉、SOD和CAT,均表明有良好抗脂质过氧化作用;大鼠心脏缺血再灌注实验表明四-(对-磺酸基苯基)卟啉锰能降低活性氧对心肌的损伤程度, 对再灌注损伤心肌有保护作用. 相似文献
7.
Lander F Kristiansen J Lauritsen JM 《International archives of occupational and environmental health》1999,72(8):546-550
Objectives: Cast iron products are alloyed with small quantities of manganese, and foundry furnacemen are potentially exposed to manganese
during tapping and handling of smelts. Manganese is a neurotoxic substance that accumulates in the central nervous system,
where it may cause a neurological disorder that bears many similarities to Parkinson's disease. The aim of the study was to
investigate the sources and levels of manganese exposure in foundry furnacemen by a combined measuring of blood-manganese
(B-Mn) and manganese in ambient air (air-Mn). Methods: During a period of 16 months, Air-Mn and B-Mn (denoted `exposure values') were measured involving 24 furnacemen employed
in three small size foundries and 21 scrap recycling workers from one plant. In the study period, 18 furnacemen had B-Mn measured
3–4 weeks after decreasing or stopping exposure (denoted `post-exposure values'). The reference group for the B-Mn measurements
consisted of 90 Danish male subjects. Results: Furnacemen who work in insufficiently ventilated smelting departments inhale, absorb, and retain significant amounts of manganese
in their blood (approx. 2.5–5 μg/l above reference values) despite a generally low measured airborne level of manganese fumes
(0.002–0.064 mg/m3). The `exposure values' compared with `post-exposure values' revealed a significant decrease in the B-Mn (on average 3.7 μg/l)
level of the most exposed furnacemen. Two persons in our study were suspected of suffering clinically subacute manganese intoxication
as both had B-Mn levels beyond the normal limit (25 and 29 μg/l, respectively). The potential problem disappeared completely
after cessation of exposure, and the B-Mn levels decreased to 9.4 and 14.1 μg/l, respectively. Conclusions: Risk assessment based on combined measurements of B-Mn and air-Mn seems to be valid in the interpretation of workers' hazard.
Our study indicates that B-Mn may be a valuable parameter for estimating recent exposure (within 1–2 weeks). However, more
knowledge is needed about the B-Mn level and its relation to neurological symptoms.
Received: 20 January 1999 / Accepted: 14 June 1999 相似文献
8.
目的 建立测定骨折挫伤胶囊中铅(Pb)、镉(Cd)、铜(Cu)、砷(As)、汞(Hg)元素含量的电感耦合等离子体-质谱(ICP-MS)法。方法 样品经人工胃液提取,以锗(Ge)、铟(In)、铋(Bi)为内标,采用ICP-MS法同时测定5种元素。结果 5种元素质量浓度在线性范围内与响应强度线性关系良好,平均回收率97.4%~102.7%,RSD均小于3.5%(n=6)。结论 该方法准确,灵敏,无干扰,可用于骨折挫伤胶囊中5种重金属及有害元素的测定。 相似文献
9.
目的比较石英纤维桩与金属铸造桩在残冠残根修复中的临床效果。方法选择残冠、残根患者145例,合计181颗患牙。经完善的根管治疗后,根据患者意愿,分为A组(纤维桩)和B组(铸造金属桩),此:较二组患者6~24个月临床复诊疗效情况。结果A组1例桩折,1例桩核松动、脱落,1例根尖周炎,成功率96.94%;B组5例根折,1例桩折,2例桩核松动、脱落,1例根尖周炎,2例牙龈晦暗,成功率86.75%,组间差异有统计学意义(P〈0.05)。结论石英纤维桩应用于残根残冠修复的临床效果优于铸造金属桩。 相似文献
10.
树脂基托、钛基托全口义齿戴用前后语音效果的对比研究 总被引:3,自引:0,他引:3
目的对全口义齿初戴前后的临床语音适应效果做出主观评价。方法以患者自评和语音专业人员共同评价汉语语音清晰度的方法,分析30例全牙列缺失患者在义齿初戴前、初戴时、初戴后1、2、4、8周的语音变化规律。结果全口义齿初戴时,两实验组均感觉发音不适,初戴1周后,金属基托组已感觉能适应义齿,塑料基托组需2周以上时间。语音清晰度测评显示,义齿初戴后1周,两组之间有显著性差异(P<0.05),此时金属基托组已显示与初戴前有非常显著差异(P<0.01),塑料基托组需2周以上时间。结论减少全口义齿基托厚度,重建腭皱形态,有助于牙列缺失患者语音功能的恢复,其语音清晰度值较高。 相似文献