Medical Physics: Key Revision Notes for IB and CIE Physics | IB CIE 物理：医疗物理 考点精讲

📚 Medical Physics: Key Revision Notes for IB and CIE Physics | IB CIE 物理：医疗物理 考点精讲

Medical physics applies principles of physics to healthcare, enabling diagnosis and treatment through imaging, radiation, and nuclear techniques. This guide covers essential topics for IB and CIE A-Level Physics students, including X-rays, ultrasound, endoscopy, nuclear medicine, MRI, and radiotherapy. Understand key concepts, equations, and clinical applications to excel in your exams.

医疗物理将物理学原理应用于医疗保健，通过成像、辐射和核技术实现诊断和治疗。本指南涵盖 IB 和 CIE A-Level 物理学生的基本主题，包括 X 射线、超声、内窥镜、核医学、核磁共振 (MRI) 与放射治疗。理解关键概念、公式和临床应用，助你在考试中脱颖而出。

1. X-ray Production | X 射线的产生

X-rays are produced in a vacuum tube containing a cathode (filament) and an anode (metal target). When the filament is heated, electrons are emitted by thermionic emission. A high voltage (typically 50–150 kV) applied between the cathode and anode accelerates these electrons to high speeds. The kinetic energy gained is Eₖ = eV, where e is the elementary charge and V is the tube voltage.

X 射线在包含阴极（灯丝）和阳极（金属靶）的真空管中产生。灯丝加热时，通过热电子发射释放电子。施加在阴极和阳极之间的高压（通常 50–150 kV）将这些电子加速到高速。获得的动能为 Eₖ = eV，其中 e 为基本电荷，V 为管电压。

When the fast electrons strike the target, they are decelerated, releasing energy as X-ray photons. About 99% of the electron kinetic energy converts to heat; hence the target must be cooled and often rotated to dissipate heat. The X-ray spectrum consists of a continuous bremsstrahlung component and characteristic lines.

当快速电子撞击靶时，它们被减速，以 X 射线光子形式释放能量。约 99% 的电子动能转化为热量；因此靶必须冷却，通常旋转以散热。X 射线谱由连续轫致辐射成分和特征线组成。

The efficiency of X-ray production increases with the atomic number Z of the target and the tube voltage. In medical tubes, tungsten (Z = 74) is commonly used for its high melting point and efficient X-ray production. The focal spot size affects image sharpness – smaller spots give finer detail but require better heat dissipation.

X 射线产生效率随靶材原子序数 Z 和管电压的增加而提高。在医用管中，常使用钨 (Z = 74)，因其熔点高且 X 射线产生效率高。焦点尺寸影响图像清晰度——小焦点提供更精细的细节，但要求更好的散热。

2. X-ray Spectra | X 射线谱

The continuous spectrum has a minimum wavelength λₘᵢₙ determined by the accelerating voltage: λₘᵢₙ = hc / eV. This represents the case where an electron loses all its kinetic energy in a single collision, producing one maximum-energy photon. As tube voltage V increases, λₘᵢₙ decreases, and the total X-ray output increases because more higher-energy photons are produced.

连续谱的最小波长 λₘᵢₙ 由加速电压决定：λₘᵢₙ = hc / eV。这代表电子在单次碰撞中损失全部动能，产生一个最大能量光子的情况。随着管电压 V 增加，λₘᵢₙ 减小，总 X 射线输出增加，因为产生了更多高能光子。

λₘᵢₙ = hc / eV

Characteristic X-rays are produced when an incoming electron knocks out a bound inner-shell electron. The vacancy is filled by an outer electron, emitting a photon

Published by TutorHao | IB Physics Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）