醫(yī)學成像技術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組織均衡(Tissue equalization, TE) 技術基于平板探測器的寬廣動態(tài)范圍，使不同組織結構以人眼的光學密度方位同時顯示在一幅

4、影像中，從而獲得不同組織整體性綜合觀察。 Over-penetrated Under-penetrated（曝光過度或不足）Attenuation differenceBrightnessContrast縱隔膜：提高對比度；降低亮度雙肺野：提高亮度，調節(jié)對比度 TE就是將采集X線信號強度，按照醫(yī)學影像顯示的要求進行重新分配。Enhanced visualization processing，EVP2022/8/12Clinical application 2 TE2022/8/12Clinical application 2 TE提高了不同層次圖像的整體可視性，傳統(tǒng)X線成像技術下對顯示不佳的結

5、構進行顯示。不用窗寬和窗位的調節(jié)即可觀察不同密度區(qū)的圖像。減少臨床攝像時的重復曝光幾率。2022/8/12Clinical application 3 TS融合斷層（Tomosynthesis）通過一次掃描獲得檢查區(qū)域內任意深度層面、多個層面的高清晰斷層圖像。2022/8/12Clinical application 3 TS2022/8/12Clinical application 3 TS一次曝光，獲得多層面體層圖像。拆分重疊的組織結構，顯示層厚和容積。劑量低1-3 mGy，常規(guī)CT的1/10。站立掃描。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圖像圖像預處理圖像分割特征提取量化和分類符號或區(qū)域標記Clinical application 6 TSOncology diagnosis & treatment evaluationTemporal Subtraction（時間減影）2022/8/12Part IIDigital subtraction angiographyWhat is DSA & D

7、SA principleContrast agentDSA display & processingDSA classificationClinical application醫(yī)學影像設備學, 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.骨骼血管軟組織2022/8/12DSA equipment & procedureC a

9、rmComputer & MonitorDetectorX-ray tubeDSA Procedure攝制普通片；制備mask; 拍攝血管造影片; 減影。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再循環(huán)636585

10、kVp, attenuation decreases 1/2Right time and kVp are critical.2022/8/12Clinical application 12022/8/12Clinical application 2介入放射學與外科學、內科學構成并列的3大治療學科。在介入放射學中，利用DSA的引導管方式，能實時顯示導管或導絲在血管內推進的情況，并清楚地觀察其與血管的關系，使其頭部的定位更為精確，因而能加速選擇性或超選擇性插管的操作。 DSA有助于各種介入性操作，如出血病灶和畸形血管的栓塞，腫瘤血管的栓塞或局部注入化學藥物，采用氣囊導管對狹窄的血管施行腔內成形術等

11、.可以說沒有DSA就沒有介入手術。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. 圖像中沒有原來的骨與軟組織影，使血管顯示清楚。（祛除偽影）2. 減少了造影劑濃度與用量，減少了造影劑的并發(fā)癥。（減少劑量和并發(fā)癥）3. 運用圖像處理技術進行造影后處理，提高了圖像質量與增強了更多信息。（提高質量）4. 由于實時顯示，使結果很快顯示，有利于立即做介入性處理。（節(jié)約時間）Drawbacks1. 對于運動器官或不自主運動（如胃腸

16、道）部位不宜做DSA。2. 靜脈法DSA顯示細小血管不夠清楚。3. 視野小，球管包含的范圍不夠大。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