ct增強掃描時機與用量把握

1、CT增強掃描給藥方案及掃描時機——文獻回顧及應用,Intravenous Contrast Medium Administration and Scan Timing at CT: Literature Review and Application,香港大學深圳醫(yī)院 何健龍,Adjustment is inevitable in certain situations including:,腎功能不全 Renal dysfuncti

2、on 肥胖 Obesity 血液循環(huán)異常 多層螺旋CT Multidetector CT 非常規(guī)靜脈入路 Venous Access Site,Goal: Achieve diagnostically adequate contrast enhancement,Cost:,Lowest radiation exposure (the shortest scan duration) Least amount of iodi

3、ne mass injected at the lowest acceptable rate for a given patient’s cardiovascular and renal function,造影劑動力學,Contrast Medium(CM) Pharmacokinetics,CT衰減 碘 X-ray能量,CT衰減與碘濃度成比例增加 Tube V. 越低，衰減比例越高 Care Mode 優(yōu)點：血管 軟組織↑

4、 CM Radiation ↓ 缺點：骨骼偽影↑ SNR ↓,造影劑動力學,Contrast Medium(CM) Pharmacokinetics,CT衰減 碘 X-ray能量,造影劑藥代動力學,Contrast Medium(CM) Pharmacokinetics,CM 體內(nèi)分布,主要與血流灌注(perfusion)相關 血液回流(recirculation)的影響 15s,造影劑藥代動力學,C

5、ontrast Medium(CM) Pharmacokinetics,CM 體內(nèi)分布,血流速度影響 峰值上升 高峰期縮短,影響增強效果和時機的因素,Factors Affecting Contrast Enhancement and Scan Timing,患者因素 Patient factors,Body Weight, Mass, Surface Area, and Mass Index,體重是最重要的影響參數(shù) 由于血容量

6、占體重比例的不同，CM的稀釋程度差異,患者因素 Patient factors,Body Weight, Mass, Surface Area, and Mass Index,調(diào)整比例1:1 linear scale e.g. doubling the iodine mass when the patient’s body weight doubles 兒童和肥胖患者血液含量的差別 Lean body weight, Su

7、rface area and Mass index 體表面積與體重直接相關 (kg0.65),患者因素 Patient factors,Body Weight, Mass, Surface Area, and Mass Index,體重是調(diào)整CM用量的最主要參數(shù) 需要提高CM用量 和/或 濃度，以應對體重的增加 以體重為基礎的調(diào)節(jié)比例基本正確，但須注意兒童和肥胖患者,患者因素 Patient factors,Cardiac Ou

8、tput and Cardiovascular Circulation,患者因素 Patient factors,Cardiac Output and Cardiovascular Circulation,是影響掃描時機的最主要參數(shù) 個體差異較大，因此需要bolus-tracking or test-bolus 器官差異：心臟、主動脈、腎/ 肝臟 CO下降或循環(huán)障礙→Bolus延遲到達→ 排空延長+強化上升,患者因素 Pat

9、ient factors,Other,性別：5-10%差異 年齡：>60 VS younger 10% stronger because of CO 身高：影響輕微 肝硬化：門脈期延遲并減弱 注射血管(intravenous access sites)：中心靜脈入路 central venous injection 效果好但不安全，須減慢注射速度前臂靜脈須用低流速，強化高峰延遲2-4s,患者因素 Patient fac

10、tors,腎功能,對比劑腎病 contrast-induced nephropathy  尤其是腎功能不全的患者 Contrast-induced Nephropathy Consensus Working Panel guideline: <100 mL in patients with GFR <60 mL/min per 1.73 m2,對比劑因素 Contrast Medium Factors,注射時

11、間 Injection Duration,對強化程度和掃描時機均有明顯影響 太短——強化不足 太長——不必要的組織及靜脈強化，影響觀察血管，浪費CM，增加腎毒性,對比劑因素 Contrast Medium Factors,注射時間 Injection Duration,,,對比劑因素 Contrast Medium Factors,注射時間 Injection Duration,體型、目標器官的血供、需要的強化程度 有時受注

12、射速率和對比劑濃度限制 計算方法A：根據(jù)體重計算適度強化所需碘用量選擇合適的注射速度及對比劑濃度得出注射時間,對比劑因素 Contrast Medium Factors,注射時間 Injection Duration,計算方法B：固定注射時間根據(jù)對比劑用量調(diào)整速度 好處是可以固定掃描時機，不需重復計算scan delay,對比劑因素 Contrast Medium Factors,注射速度（流速） Injection

13、Rate,對比劑因素 Contrast Medium Factors,注射速度（流速） Injection Rate,提高流速用于可提高增強效果，但會縮小掃描時間窗(window for CT scanning)，適合短程掃描,對比劑因素 Contrast Medium Factors,Fast injection for short scan duration 應用于內(nèi)臟多期掃描 multiphasic imaging Slo

14、w injection for long scan duration,注射速度（流速） Injection Rate,對比劑因素 Contrast Medium Factors,對比劑濃度 Contrast Medium Concentration,Fixed CM Volumn,對比劑因素 Contrast Medium Factors,對比劑濃度 Contrast Medium Concentration,Fixed iodi

15、ne mass,e.g. 42g iodine for 70kg 4mL/s,300 mgI/mL at 140 mL 350 mgI/mL at 120 mL 400 mgI/mL at 105 mL,對比劑因素 Contrast Medium Factors,對比劑濃度 Contrast Medium Concentration,Effect of fixed iodine mass per second,300 mgI/

16、mL at 4mL/s vs 400 mgI/mL at 3mL/s,1.2g iodine / s,低濃度在CTA也許更好，因為減輕靜脈強化的背景干擾，尤其是下肢粘度低，系統(tǒng)壓力低,iodine delivery rate 碘劑給藥速度,對比劑因素 Contrast Medium Factors,對比劑濃度 Contrast Medium Concentration,提 示,為了提高對比劑給藥速

17、度，使用高濃度碘劑相當于提高注射速率 在快速多排螺旋CT(MDCT)，提高碘給藥速度可以使動脈強化更明顯，動脈期與延遲期分別更大 高濃度碘劑的潛在缺點在于高粘度,對比劑因素 Contrast Medium Factors,對比劑粘度 Viscosity,高濃度CM對增強效果的改善可能低于預期 受溫度影響，加熱至35°左右可降低粘度，改善患者耐受力 加溫可能會增加強化效果并使強化峰值提前,對比劑因素 Contrast

18、Medium Factors,沖管 Saline flush,提高CM集中度，改善增強效果 在胸部掃描中減輕無名靜脈及上腔靜脈引起的條形偽影 reduced streak artifact from dense contrast medium in thebrachiocephalic vein and superior vena cava on thoracic CT studies 減輕腎毒性 避免殘留CM堵塞靜脈留置管

19、 central line or PICC,對比劑因素 Contrast Medium Factors,沖管 Saline flush,沖管量決定于注射管容量contrast medium retained in the injection tubing 肘前靜脈至上腔靜脈的血容量 the peripheral venous space between the brachial vein and the superior ve

20、na cava 通常約20-30mL 對掃描時機的影響輕微,CT掃描因素 CT Scanning Factors,掃描時間 Scan Duration,掃描時間直接影響注射時間 Short scan < 10s Long scan including: 全外周血管造影 peripheral runoff CT angiography 冠脈造影 灌注掃描 perfusion acquisitions,,,CT掃

21、描因素 CT Scanning Factors,掃描方向 Scan Direction,一般為順造影劑流向 Craniocaudal Craniocaudal difference Caudocranial scanning Pulmonary CT angiography for the detection of pulmonary emboli Contrast material injection duration m

22、ay need to be increased,CT掃描因素 CT Scanning Factors,Determination of Contrast Material Arrival Time: Test Bolus vs Bolus-tracking Method,TB: 小劑量團注 時間曲線 適當延遲 BT: 正常注射 閾值監(jiān)控 延遲觸發(fā)掃描 前者更準確，后者更有效率,CT掃描因素 CT Scanning Fact

23、ors,Determination of Contrast Material Arrival Time: Bolus-tracking,觸發(fā)閾值 enhancement threshold: 50-150 HU 觸發(fā)后延遲 post trigger delay,CT掃描因素 CT Scanning Factors,Determination of Contrast Material Arrival Time: Test Bolus

24、,Particularly for cardiac CT angiographic,CT掃描因素 CT Scanning Factors,只代表對比劑到達時間，不代表掃描延遲 對掃描延遲的個體化 individualize Scan dalay= Tarr + post trigger delay Post trigger delay depends on:injection duration, scan duration, h

25、emodynamics, location of target organ,Determination of Contrast Material Arrival Time: Time of arrival, Tarr,CT掃描因素 CT Scanning Factors,Determination of Contrast Material Arrival Time: Time of arrival, Tarr,常用Tarr 7–1

26、0 s for pulmonary artery 12–15 s for ascending aorta 15–18 s for abdominal aorta 30–40 s for hepatic parenchyma,CT掃描因素 CT Scanning Factors,TPEAK=TID+TARR-5or TPEAK=TID+TARR+25 TDELAY=TPEAK - 1/2TSD,掃描延遲 Scan delay

27、,Summary,使用較低的tube voltage可獲得更強的對比效果，或者減少對比劑用量 影響對比增強效果最重要的因素是患者體重 Injection duration 注射時間是最重要的注射器影響因素 Test bolus測得的TARR不能簡單理解為掃描延遲，而是作為計算延遲的重要參數(shù) Scan delay=TARR + post trigger delay 推薦的scan delay計算公式為： TDELAY=TPEAK

28、 - 1/2TSD,Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches ; Kyongtae T.Bae, MD, PhD; July 2010, Radiology, 256, 32-61.,CT掃描因素 CT Scanning Factors,掃描延遲 Scan delay,Part two,

29、Clinical CT Applications,300 mgI/mL at 4mL/s vs 400 mgI/mL at 3mL/s,1.2g iodine / s,Iodine delivery rate 碘劑給藥速度,使用較低的tube voltage可獲得更強的對比效果，或者減少對比劑用量 影響對比增強效果最重要的因素是患者體重,Adjustment is inevitable in cert

30、ain situations including:,腎功能不全 Renal dysfunction 肥胖 Obesity 血液循環(huán)異常 多層螺旋CT Multidetector CT 非常規(guī)靜脈入路 Venous Access Site,Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches

31、 Kyongtae T.Bae, MD, PhD; Radiology, July 2010, 256, 32-61.,TARR at ascending aorta 降主動脈,Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches Kyongtae T.Bae, MD, PhD; Radiolo

32、gy, July 2010, 256, 32-61.,Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches Kyongtae T.Bae, MD, PhD; Radiology, July 2010, 256, 32-61.,To achieve CT angiographic attenuatio

33、n of 250–350 HU for a 70-kg adult, 25 g of iodine injected at 1.6 g of iodine per second Caudocranial scanning direction TARR at ascending aorta 升主動脈 A longer diagnostic delay will be required for a faster scan, a

34、longer injection, and brain-only CT angiography,Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches Kyongtae T.Bae, MD, PhD; Radiology, July 2010, 256, 32-61.,Enhancement of 1

35、50–200 HU in the thoracic vessels and cardiac chambers A shorter delay is typically used for greater thoracic cardiovascular enhancement, whereas a longer delay is used to increase the enhancement in the mediastinal sof

36、t tissue as well as the upper abdominal viscera.,Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches Kyongtae T.Bae, MD, PhD; Radiology, July 2010, 256, 32-61.,Diagnostic enha

37、ncement of pulmonary artery attenuation at 300–350 HU, with 1.4-1.6 g iodine/second Increased amount by 20%–40% of contrast medium for venography.,Intravenous Contrast Medium Administration and Scan Timing at CT: Consid

38、erations and Approaches Kyongtae T.Bae, MD, PhD; Radiology, July 2010, 256, 32-61.,Diagnostic enhancement of coronary attenuation at 300–350 HU Higher attenuation may lead to an underestimation of stenosis in smaller v

39、essels, whereas lower attenuation may cause a slight overestimation of stenosis Prospective cardiac-gated coronary CT angiography necessitates a longer injection duration for its longer scan duration,Intravenous Contras

40、t Medium Administration and Scan Timing at CT: Considerations and Approaches Kyongtae T.Bae, MD, PhD; Radiology, July 2010, 256, 32-61.,Injection rate is adjusted for the body weight, the injection duration is adjusted

41、for the scan duration. The total amount of C.M. volume is determined as the product of the injection rate and duration. CT scanner table may move faster than the contrast material bolus ("outrunning") Delib

42、erately reducing the scan speed would help prevent outrunning of the contrast material bolus Test-bolus recommended,,Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches Kyong

43、tae T.Bae, MD, PhD; Radiology, July 2010, 256, 32-61.,With multidetector CT, 50 HU is commonly considered to be a diagnostically appropriate level of hepatic phase enhancement. Be ware of obese patients for iodine dose