IV.Safety ofX-ray examinationBiological effects of X-ray can cause radiation damageThe indications of X-ray examinations should be strictly controlledtoavoidunnecessary radiation射线检查请使用个人防护用品Methods of radiation protectionShieldprotection（屏蔽防护）Distanceprotection（距离防护）Timeprotection（时间防护）
IV. Safety of X-ray examination ◼ Biological effects of X-ray can cause radiation damage. ◼ The indications of X-ray examinations should be strictly controlled to avoid unnecessary radiation. ◼ Methods of radiation protection ➢ Shield protection（屏蔽防护） ➢ Distance protection（距离防护） ➢ Time protection（时间防护）
V.Features of X-ray imagesThe black and white grayscale ofthe image reflects the density ofthe tissue.Highdensity-white shadow,Medium density-gray shadow, Low density-dark shadowTheX-ray image is an image ofoverlappingtissues and structuresR
V. Features of X-ray images ◼ The black and white grayscale of the image reflects the density of the tissue. High density-white shadow; Medium density-gray shadow; Low density-dark shadow. ◼ The X-ray image is an image of overlapping tissues and structures
Sect. 2 computed tomography (CT)ImagingprincipleII. Device and imaging featuresIl.Examination methodsIV.Safety of CTexamV. Image characteristics
Sect. 2 computed tomography（CT） I. Imaging principle II. Device and imaging features III. Examination methods IV. Safety of CT exam V. Image characteristics
I. Principle of CT imagingAnX-raybeam is used to scanthecross section of theImagestomographiquesransversesreconstruitesbodyThe detector receivesthe X-ray through thehuman body and convertsit into digital informationcalculatesthedigital information ofeachVoxel,andconstructs a digital matrix.Thedigital matrix isVueventro-dorsaleThoraxGoldenretrieverreconstructedinto agrayscaleimagennX1+X2=a5X1+Y1=CY1+Y2=b5486Y1+Y2=d
I. Principle of CT imaging X1 X2 Y1 Y2 ➢ An X-ray beam is used to scan the cross section of the body. The detector receives the X-ray through the human body and converts it into digital information, calculates the digital information of each Voxel, and constructs a digital matrix. The digital matrix is reconstructed into a grayscale image. 5 9 6 8 X1+X2=a X1+Y1=c Y1+Y2=b Y1+Y2=d 2 3 4 5
II. Device and imaging propertiesDevice:scanning gantry, bed andcomputer processing systemCategory:Single-slice spiral(单层螺旋）CTMulti-slice spiral(多层螺旋）CTDual-source(双源）CTDual-energy(能谱)CT
II. Device and imaging properties ◼ Device: ➢ scanning gantry, bed and computer processing system ◼ Category: ➢ Single-slice spiral(单层螺旋)CT ➢ Multi-slice spiral(多层螺旋)CT ➢ Dual-source(双源)CT ➢ Dual-energy(能谱)CT