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1、CT增强扫描给药方案及扫描时机 文献回顾及应用,Intravenous Contrast Medium Administration and Scan Timing at CT: Literature Review and Application,香港大学深圳医院 何健龙,Adjustment is inevitable in certain situations including:,肾功能不全 Renal dysfunction肥胖 Obesity血液循环异常多层螺旋CT Multidetector CT 非常规静脉入路 Venous Access Site,Goal: Achieve d
2、iagnostically adequate contrast enhancement,Cost:,Lowest radiation exposure (the shortest scan duration)Least amount of iodine mass injected at the lowest acceptable rate for a given patients cardiovascular and renal function,造影剂动力学,Contrast Medium(CM) Pharmacokinetics,CT衰减 碘 X-ray能量,CT衰减与碘浓度成比例增加Tu
3、be V. 越低，衰减比例越高Care Mode优点：血管 软组织 CM Radiation 缺点：骨骼伪影 SNR ,造影剂动力学,Contrast Medium(CM) Pharmacokinetics,CT衰减 碘 X-ray能量,造影剂药代动力学,Contrast Medium(CM) Pharmacokinetics,CM 体内分布,主要与血流灌注(perfusion)相关血液回流(recirculation)的影响15s,造影剂药代动力学,Contrast Medium(CM) Pharmacokinetics,CM 体内分布,血流速度影响峰值上升高峰期缩短,影响增强效果和时机的因
4、素,Factors Affecting Contrast Enhancement and Scan Timing,患者因素 Patient factors,Body Weight, Mass, Surface Area, and Mass Index,体重是最重要的影响参数由于血容量占体重比例的不同，CM的稀释程度差异,患者因素 Patient factors,Body Weight, Mass, Surface Area, and Mass Index,调整比例1:1 linear scalee.g. doubling the iodine mass when the patients bo
5、dy weight doubles儿童和肥胖患者血液含量的差别Lean body weight, Surface area and Mass index体表面积与体重直接相关 (kg0.65),患者因素 Patient factors,Body Weight, Mass, Surface Area, and Mass Index,体重是调整CM用量的最主要参数需要提高CM用量 和/或 浓度，以应对体重的增加以体重为基础的调节比例基本正确，但须注意儿童和肥胖患者,患者因素 Patient factors,Cardiac Output and Cardiovascular Circulation,
6、患者因素 Patient factors,Cardiac Output and Cardiovascular Circulation,是影响扫描时机的最主要参数个体差异较大，因此需要bolus-tracking or test-bolus器官差异：心脏、主动脉、肾/ 肝脏CO下降或循环障碍Bolus延迟到达 排空延长+强化上升,患者因素 Patient factors,Other,性别：5-10%差异年龄：60 VS younger 10% stronger because of CO身高：影响轻微肝硬化：门脉期延迟并减弱注射血管(intravenous access sites)： 中心静脉
7、入路 central venous injection 效果好但不安全，须减慢注射速度 前臂静脉须用低流速，强化高峰延迟2-4s,患者因素 Patient factors,肾功能,对比剂肾病 contrast-induced nephropathy 尤其是肾功能不全的患者Contrast-induced Nephropathy Consensus Working Panel guideline:100 mL in patients with GFR 60 mL/min per 1.73 m2,对比剂因素 Contrast Medium Factors,注射时间 Injection Durati
8、on,对强化程度和扫描时机均有明显影响太短强化不足太长不必要的组织及静脉强化，影响观察血管，浪费CM，增加肾毒性,对比剂因素 Contrast Medium Factors,注射时间 Injection Duration,对比剂因素 Contrast Medium Factors,注射时间 Injection Duration,体型、目标器官的血供、需要的强化程度有时受注射速率和对比剂浓度限制计算方法A： 根据体重计算适度强化所需碘用量 选择合适的注射速度及对比剂浓度 得出注射时间,对比剂因素 Contrast Medium Factors,注射时间 Injection Duration,计算
9、方法B： 固定注射时间 根据对比剂用量调整速度好处是可以固定扫描时机，不需重复计算scan delay,对比剂因素 Contrast Medium Factors,注射速度（流速） Injection Rate,对比剂因素 Contrast Medium Factors,注射速度（流速） Injection Rate,提高流速用于可提高增强效果， 但会缩小扫描时间窗(window for CT scanning)，适合短程扫描,对比剂因素 Contrast Medium Factors,Fast injection for short scan duration应用于内脏多期扫描 multip
10、hasic imagingSlow injection for long scan duration,注射速度（流速） Injection Rate,对比剂因素 Contrast Medium Factors,对比剂浓度 Contrast Medium Concentration,Fixed CM Volumn,对比剂因素 Contrast Medium Factors,对比剂浓度 Contrast Medium Concentration,Fixed iodine mass,e.g. 42g iodine for 70kg 4mL/s,300 mgI/mL at 140 mL 350 mgI
11、/mL at 120 mL 400 mgI/mL at 105 mL,对比剂因素 Contrast Medium Factors,对比剂浓度 Contrast Medium Concentration,Effect of fixed iodine mass per second,300 mgI/mL at 4mL/s vs 400 mgI/mL at 3mL/s,1.2g iodine / s,低浓度在CTA也许更好，因为 减轻静脉强化的背景干扰，尤其是下肢 粘度低，系统压力低,iodine delivery rate 碘剂给药速度,对比剂因素 Contrast Medium Factors,
12、对比剂浓度 Contrast Medium Concentration,提 示,为了提高对比剂给药速度，使用高浓度碘剂相当于提高注射速率在快速多排螺旋CT(MDCT)，提高碘给药速度可以使动脉强化更明显，动脉期与延迟期分别更大高浓度碘剂的潜在缺点在于高粘度,对比剂因素 Contrast Medium Factors,对比剂粘度 Viscosity,高浓度CM对增强效果的改善可能低于预期受温度影响，加热至35左右可降低粘度，改善患者耐受力加温可能会增加强化效果并使强化峰值提前,对比剂因素 Contrast Medium Factors,冲管 Saline flush,提高CM集中度，改善增强效果
13、在胸部扫描中减轻无名静脉及上腔静脉引起的条形伪影 reduced streak artifact from dense contrast medium in the brachiocephalic vein and superior vena cava on thoracic CT studies减轻肾毒性避免残留CM堵塞静脉留置管 central line or PICC,对比剂因素 Contrast Medium Factors,冲管 Saline flush,冲管量决定于 注射管容量 contrast medium retained in the injection tubing 肘前静
14、脉至上腔静脉的血容量 the peripheral venous space between the brachial vein and the superior vena cava通常约20-30mL对扫描时机的影响轻微,CT扫描因素 CT Scanning Factors,扫描时间 Scan Duration,扫描时间直接影响注射时间Short scan 10sLong scan including:全外周血管造影 peripheral runoff CT angiography 冠脉造影灌注扫描 perfusion acquisitions,CT扫描因素 CT Scanning Fact
15、ors,扫描方向 Scan Direction,一般为顺造影剂流向 Craniocaudal Craniocaudal differenceCaudocranial scanningPulmonary CT angiography for the detection of pulmonary emboliContrast material injection duration may need to be increased,CT扫描因素 CT Scanning Factors,Determination of Contrast Material Arrival Time: Test Bolu
16、s vs Bolus-tracking Method,TB: 小剂量团注 时间曲线 适当延迟BT: 正常注射 阈值监控 延迟触发扫描前者更准确，后者更有效率,CT扫描因素 CT Scanning Factors,Determination of Contrast Material Arrival Time: Bolus-tracking,触发阈值 enhancement threshold: 50-150 HU触发后延迟 post trigger delay,CT扫描因素 CT Scanning Factors,Determination of Contrast Material Arrival Time: Test Bolus,Particularly for cardiac CT angiographic,CT扫描因素 CT Scanning Factors,只代表对比剂到达时间，不代表扫描延迟对扫描延迟的个体化 individualizeScan dalay= Tarr + post trigger delayPost trigger delay depends on: injection duration, scan duration, hemodynamics, location of target organ,
