📚 Computerised Axial Tomography | 计算机轴向断层扫描
1. Introduction | 引言
Computerised Axial Tomography (CAT), also known as Computed Tomography (CT), is a medical imaging technique that combines X-ray measurements taken from multiple angles around the body and uses computer processing to create cross-sectional images. The term “axial” refers to the fact that the images produced are typically in the axial plane — that is, horizontal slices through the body.
计算机轴向断层扫描（CAT），又称计算机断层扫描（CT），是一种医学成像技术。它结合了从身体周围多个角度采集的X射线测量数据，并利用计算机处理生成身体的横截面图像。”轴向”一词指的是所生成的图像通常位于轴向平面，即通过身体的水平切片。
A British engineer named Godfrey Hounsfield invented the first commercial CT scanner in the early 1970s at EMI Central Research Laboratories. He shared the 1979 Nobel Prize in Physiology or Medicine with Allan Cormack, who had independently developed the mathematical foundations for the technique.
英国工程师戈弗雷·豪斯菲尔德于20世纪70年代初在EMI中央研究实验室发明了第一台商用CT扫描仪。他与独立奠定该技术数学基础的艾伦·科马克分享了1979年诺贝尔生理学或医学奖。
2. Principles of X-ray Attenuation | X射线衰减原理
When X-rays pass through the human body, they are attenuated — meaning their intensity is reduced — by absorption and scattering. Different types of body tissue attenuate X-rays to different degrees. Dense materials such as bone absorb more X-rays, while softer tissues such as muscle and fat absorb fewer. Air absorbs almost none.
当X射线穿过人体时，会因吸收和散射而衰减，即其强度降低。不同类型的身体组织对X射线的衰减程度不同。骨骼等致密材料吸收较多X射线，而肌肉、脂肪等较软的组织吸收较少，空气几乎不吸收。
The attenuation of X-rays follows an exponential law described by the Beer-Lambert equation. If I₀ is the initial intensity of the X-ray beam, μ is the linear attenuation coefficient of the material, and x is the path length through the material, then the transmitted intensity I is given by:
X射线的衰减遵循由比尔-朗伯定律描述的指数规律。若I₀为X射线束的初始强度，μ为材料的线性衰减系数，x为穿过材料的路径长度，则透射强度I由下式给出：
I = I₀ × e^(−μx)
In a CT scan, the body consists of many different materials with different attenuation coefficients. The total attenuation along an X-ray path is the integral of μ along that path. The detector measures this integral, and the challenge is to reconstruct the spatial distribution of μ within the body slice from many such measurements taken at different angles.
在CT扫描中，人体由许多具有不同衰减系数的材料组成。沿某条X射线路径的总衰减是该路径上μ的积分。探测器测量此积分值，而面临的挑战是从不同角度采集的大量此类测量值中重建出身体切片内μ的空间分布。
3. Scanner Architecture | 扫描仪架构
A modern CT scanner consists of several key hardware components working together. The X-ray tube generates a fan-shaped beam of X-rays that passes through the patient. An array of detectors is positioned on the opposite side of the patient, diametrically opposite the X-ray tube. Both the X-ray tube and the detector array are mounted on a rotating gantry.
现代CT扫描仪由若干协同工作的关键硬件组件构成。X射线管产生扇形X射线束，穿过患者身体。探测器阵列位于患者对侧，与X射线管径向相对。X射线管和探测器阵列都安装在旋转机架上。
-
X-ray tube: generates a collimated fan beam of X-rays with typical energies in the range 20-150 keV
X射线管：产生准直的扇形X射线束，典型能量范围为20-150 keV
-
Detector array: typically contains thousands of individual detector elements that convert X-rays into electrical signals
探测器阵列：通常包含数千个独立的探测器元件，将X射线转换为电信号
-
Rotating gantry: spins the X-ray
Published by TutorHao | A-Level Computer Science Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导