医学成像技术lecture5dr applicationdsa

1、Lecture VDR application & DSALi Hong2022/8/12ReviewClassification of X-ray radiography, CR, and DR CR workflow and main componentsDR classification( DDR & IDR, Plane & Line scan)Quality evaluation parameter: DQE, MTF, dynamic range, Pixel & spatial parameters2022/8/12ContentDR applicationsDigital su

2、btraction angiographyReference: 第四章, P84-892022/8/12Part IDR application2022/8/12Clinical application 1 DES Dual Energy SubtractionHLLow kV：High kV：IfIfLow kV：High kV：2022/8/12Clinical application 1 DES2022/8/12Clinical application 1 DES GE technique AEC （Automatic exposure control, AEC) 120150 kVp，

3、6080 kVp, interval 200msTechnique difficulties:1. Rapid switch-over of high voltage generator2. Rapid response & acquisition of FPDIs there any other technique to realize this function?1 exposure2022/8/12Clinical application 2 TE组织均衡(Tissue equalization, TE) 技术基于平板探测器的宽广动态范围，使不同组织结构以人眼的光学密度方位同时显示在一幅

4、影像中，从而获得不同组织整体性综合观察。 Over-penetrated Under-penetrated（曝光过度或不足）Attenuation differenceBrightnessContrast纵隔膜：提高对比度；降低亮度双肺野：提高亮度，调节对比度 TE就是将采集X线信号强度，按照医学影像显示的要求进行重新分配。Enhanced visualization processing，EVP2022/8/12Clinical application 2 TE2022/8/12Clinical application 2 TE提高了不同层次图像的整体可视性，传统X线成像技术下对显示不佳的结

5、构进行显示。不用窗宽和窗位的调节即可观察不同密度区的图像。减少临床摄像时的重复曝光几率。2022/8/12Clinical application 3 TS融合断层（Tomosynthesis）通过一次扫描获得检查区域内任意深度层面、多个层面的高清晰断层图像。2022/8/12Clinical application 3 TS2022/8/12Clinical application 3 TS一次曝光，获得多层面体层图像。拆分重叠的组织结构，显示层厚和容积。剂量低1-3 mGy，常规CT的1/10。站立扫描。2022/8/12Clinical application 4 IPImage pas

6、ting2022/8/12Soft X-rayClinical application 5 CAD Mammography2022/8/12Clinical application 5 CAD Mammography2022/8/12DR图像图像预处理图像分割特征提取量化和分类符号或区域标记Clinical application 6 TSOncology diagnosis & treatment evaluationTemporal Subtraction（时间减影）2022/8/12Part IIDigital subtraction angiographyWhat is DSA & D

7、SA principleContrast agentDSA display & processingDSA classificationClinical application医学影像设备学, Chapter 4, P210-2682022/8/12What is DSA？ Digital Subtraction Angiography (DSA)Cerebral Angiography-Takingimages of arteries & veins- An injection of a special dye- dye (a clear liquid, but with high dens

8、ity)- Harmless, pass out of body in urine over the hours2022/8/12DSA principleBefore injection:After injection:Digital subtraction:DSA signal is proportional with the “dye” thickness and the difference between attenuation coefficients of tissue and iodine.骨骼血管软组织2022/8/12DSA equipment & procedureC a

9、rmComputer & MonitorDetectorX-ray tubeDSA Procedure摄制普通片；制备mask; 拍摄血管造影片; 减影。Same locationSame dose2022/8/12Contrast agent33 keV6 times increaseIodine (Z = 53) Barium (Z = 56) Soft tissue (Zeff = 7.4)Photoelectric interactionsvary with Z3 of the tissue5302022/8/12DSA signal amplitude & keV再循环636585

10、kVp, attenuation decreases 1/2Right time and kVp are critical.2022/8/12Clinical application 12022/8/12Clinical application 2介入放射学与外科学、内科学构成并列的3大治疗学科。在介入放射学中，利用DSA的引导管方式，能实时显示导管或导丝在血管内推进的情况，并清楚地观察其与血管的关系，使其头部的定位更为精确，因而能加速选择性或超选择性插管的操作。 DSA有助于各种介入性操作，如出血病灶和畸形血管的栓塞，肿瘤血管的栓塞或局部注入化学药物，采用气囊导管对狭窄的血管施行腔内成形术等

11、.可以说没有DSA就没有介入手术。Interventional surgery2022/8/123D digital angiographyWhen the acquisition sequence is initiated, the C-arm rotates from left to right for 220o at 40o per second but data acquisition is plished at the range of 200o, acquiring at 8.8 frames per second for 5 seconds resulting in 44 mas

12、k- images in 5122 matrix.The gantry then rotates back to the starting position. When the C-arm returns to the starting position, the Power injector is initiated according to the injector delay protocol, which is Mask-to-Image delay of 1.1 seconds and Injector-to-image delay of 1.1 seconds.The Power

13、injector injects 18 milliliter of Visipaque 280 at the rate of 3.6 ml/second for Internal Carotid Artery(ICA). The gantry repeats the mask acquisition path and acquires another 44 images with contrast. Real time subtraction angiographs are displayed on post processing screen.Step 1 Mask acquisitionS

14、tep 2 Image acquisition2022/8/123D digital angiography reconstruction SSDSurface Shaded Display MIPMaximum Intensity Projection. This shows the maximum pixel value and the anatomy but lacks the perception of depth. NavigatorFly through sequence or Virtual Endoscopy. The view is from within the vesse

15、l. Volume Rendering where the pixel value is taken into account, creating a see-through effect.2022/8/12Merit & drawbacksMerit:1. 图像中没有原来的骨与软组织影，使血管显示清楚。（祛除伪影）2. 减少了造影剂浓度与用量，减少了造影剂的并发症。（减少剂量和并发症）3. 运用图像处理技术进行造影后处理，提高了图像质量与增强了更多信息。（提高质量）4. 由于实时显示，使结果很快显示，有利于立即做介入性处理。（节约时间）Drawbacks1. 对于运动器官或不自主运动（如胃肠

16、道）部位不宜做DSA。2. 静脉法DSA显示细小血管不够清楚。3. 视野小，球管包含的范围不够大。2022/8/12Trends 3D digital angiography CT angiography (for aged people) MRA- Magnetic resonance angiographyCTA (before & after injection)MRA 3d visualization2022/8/12Conclusions Dual energy subtraction method What are TE, TS and IP(Image Pasting) & th

17、eir principles DSA principle, equipment & procedure DSA classification & temporal model2022/8/12Summary2022/8/12 X-ray generationX-ray generation equipment (Tube)X-ray generation physics (Energy spectrum)X-ray tube focal spot and rated parameterX-ray radiation dose Interaction between X-ray and substanceAttenuation coefficientHalf value layerPhotoelectric absorptionCompton scatteringEffective atomic numberAbsorption edge X-ray radiographyClassification of X-ray radiography, CR, and DR CR workflow and main componentsDR classificat