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相关概念视频

Computed Tomography01:10

Computed Tomography

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Tomography refers to imaging by sections. Computed tomography (CT) is a non-invasive imaging technique that uses computers to analyze several cross-sectional X-rays to reveal minute details about structures in the body.
The technique was invented in the 1970s and is based on the principle that as X-rays pass through the body, they are absorbed or reflected at different levels. In the technique, a patient lies on a motorized platform while a computerized axial tomography (CAT) scanner rotates...
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Constant Pressure Calorimetry03:02

Constant Pressure Calorimetry

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Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a substance. The heat is exchanged with a calibrated and insulated device called the calorimeter. Calorimetry experiments are based on the assumption that there is no heat exchange between the insulated calorimeter and the external environment. The well-insulated calorimeters prevent the transfer of heat between the calorimeter and its external...
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Calorimetry01:19

Calorimetry

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When objects at different temperatures are placed in contact with each other but isolated from everything else, they attain thermal equilibrium. A container that prevents heat transfer in or out is called a calorimeter, and the use of a calorimeter to make measurements is called calorimetry. Generally, these measurements involve heat or specific heat capacity. The term "calorimetry problem" is used for any problem where the specified objects are thermally isolated from their...
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Absorption of Radiation01:05

Absorption of Radiation

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The rate of heat transfer by emitted radiation is described by the Stefan-Boltzmann law of radiation:
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Constant Volume Calorimetry02:41

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Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant (atmospheric) pressure and are convenient to measure heat flow (or enthalpy change) accompanying processes that occur in solution at constant pressure. A different type of calorimeter that operates at constant volume, colloquially known as a bomb calorimeter, is used to measure the energy produced by reactions that yield large amounts of heat and...
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X-ray Imaging01:24

X-ray Imaging

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German physicist Wilhelm Röntgen (1845–1923) was experimenting with electrical current when he discovered that a mysterious and invisible "ray" would pass through his flesh but leave an outline of his bones on a screen coated with a metal compound. In 1895, Röntgen made the first durable record of the internal parts of a living human: an "X-ray" image (as it came to be called) of his wife’s hand. Scientists worldwide quickly began their own experiments with...
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相关实验视频

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计算断层扫描中的热量测量 束束

H Heather Chen-Mayer1, Ronald E Tosh1, Fred B Bateman1

  • 1National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.

Journal of research of the National Institute of Standards and Technology
|March 12, 2024
PubMed
概括

开发了一种新的便携式热量计,用于测量医学计算机断层扫描 (CT) 扫描中吸收的剂量. 虽然对高能X射线准确,但多余的热量使CT光束的测量变得复杂,未来的设计需要低原子数传感器.

科学领域:

  • 医学物理 医学物理
  • 放射性剂量测量 放射性剂量测量 放射性剂量测量
  • 仪器化 仪器化 仪器化

背景情况:

  • 精确的吸收剂量确定对于医学成像中的患者安全至关重要.
  • 计算机断层扫描 (CT) 程序需要专门的剂量测量方法,因为它们具有独特的光束特性.
  • 现有的剂量测量技术可能在直接实现CT吸收剂量方面存在局限性.

研究的目的:

  • 构建和评估便携式热量计,用于在CT手术中直接实现吸收剂量.
  • 在临床加速器和CT扫描仪光束中,将热量计测量与电离室读数进行比较.
  • 确定未来用于CT剂量计的热量计的设计考虑因素.

主要方法:

  • 一个带有聚烯芯和热敏电阻的便携式热量计被设计成可以插入高密度聚乙烯幻影中.
  • 热量计和校准的电离室被用于测量6MVX射线和120kVpCTX射线束中吸收的剂量.
  • 用各种剂量率进行测量,并分析频率和时间领域的数据,以评估热量计响应和多余热量.

主要成果:

  • 热量计显示与电离室对6MVX射线有很好的一致性,多余热量可以忽略不计.
  • 对于120kVp的CT光束,热度计响应受到多余热量的显著影响 (温度升高增加的15%的因素).
关键词:
剂量 CT CT 剂量吸收的剂量吸收的剂量热量计热量计.中等能量的X射线.聚乙烯是一种聚乙烯.热敏电阻是一个热敏电阻.

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  • 热敏电阻的高原子数组成在CT光束中主导了热量计的响应,表明需要使用不同的传感器材料.
  • 结论:

    • 开发的便携式热量计适用于高能X射线束中吸收剂量测量,但需要对CT应用进行修改.
    • 在热量计组件中产生的多余热量是CT剂量计的一个重大挑战.
    • 未来的CT兼容热度计应该使用低原子数温度传感器来提高准确性和可靠性.