Contrast enhancement in ischaemic lesions

Summary The contribution of post-enhancement CT scans to the diagnosis of acute cerebral infarction was studied in a consecutive series of infarcts. The timing, density and pattern of enhancement were also analysed for any possible prognostic information, and the incidence of factors of known prognostic significance was estimated on plain and contrast enhanced scans. Enhancement patterns of infarcts were variable and in those cases in which the plain CT diagnosis was equivocal the post-enhancement CT was not infrequently ambiguous also, and occasionally misleading. The outcome of infarcts that enhanced was significantly poorer than in those not showing enhancement, although no relationship between the timing, density or pattern of enhancement and prognosis could be shown. Consideration of the distribution of other factors known to adversely affect prognosis in the two groups does not adequately account for the difference between them suggesting that the contrast medium itself could be the cause of the poorer outcome. There are few positive indications for post-contrast scanning of suspected infarcts and the possible adverse effects of contrast medium should be considered prior to administration.     

电子束CT血管造影评价冠状动脉狭窄

目的:探讨电子束CT(EBT)血管造影评价冠状动脉狭窄的价值.材料和方法:分析56例经EBT血管造影和常规冠状动脉造影(CAG)检查的资料,将冠状动脉各支分成13个节段与相应CAG结果逐一对照,并进行统计学分析.结果:679个≥2mm的冠状动脉节段中,EBT可评价562个,无法评价117个.EBT对各支冠状动脉的评价准确性依次为左主干、前降支和右冠;对各节段的评价以近段的敏感性、特异性和阴性预测值最高;对不同程度狭窄的评价以＞75%狭窄的诊断最为可靠.此外对正常冠状动脉的诊断准确性也较高,为88.5%.结论:EBT血管造影对评价冠状动脉近段狭窄、重度狭窄和正常血管有很高的价值,可作为CAG术前筛选的常规无创性检查方法.     

脑膜瘤的CT表现与病理对照研究

目的探讨脑膜瘤的CT表现与病理分型之间的关系。方法收集经CT诊断和手术病理证实的脑膜瘤12例,CT检查均采用增强前后常规扫描,病理为手术巨检和切片光镜下所见。结果典型脑膜瘤为过渡型或纤维母细胞型脑膜瘤,密度(信号)均匀,明显均匀强化,15%~20%伴有钙化,无或轻度瘤周水肿。不典型脑膜瘤以合胞体和血管母细胞瘤型脑膜瘤为主,密度(信号)不均匀,无或不均匀强化,瘤周水肿较重。恶性脑膜瘤为混杂密度(信号)肿块,强化不均匀,形状不规则,瘤周水肿明显,伴有骨质破坏。结论CT平扫 增强是诊断脑膜瘤的最主要方法,准确率为95%,在一定程度上可提示脑膜瘤的病理学分型,为术前选择手术方案及判定预后提供信息。     

Contrast Media in Abdominal Computed Tomography: Optimization of Delivery Methods

Objective

To provide a systematic overview of the effects of various parameters on contrast enhancement within the same population, an animal experiment as well as a computer-aided simulation study was performed.

Materials and Methods

In an animal experiment, single-level dynamic CT through the liver was performed at 5-second intervals just after the injection of contrast medium for 3 minutes. Combinations of three different amounts (1, 2, 3 mL/kg), concentrations (150, 200, 300 mgI/mL), and injection rates (0.5, 1, 2 mL/sec) were used. The CT number of the aorta (A), portal vein (P) and liver (L) was measured in each image, and time-attenuation curves for A, P and L were thus obtained. The degree of maximum enhancement (Imax) and time to reach peak enhancement (Tmax) of A, P and L were determined, and times to equilibrium (Teq) were analyzed. In the computed-aided simulation model, a program based on the amount, flow, and diffusion coefficient of body fluid in various compartments of the human body was designed. The input variables were the concentrations, volumes and injection rates of the contrast media used. The program generated the time-attenuation curves of A, P and L, as well as liver-to-hepatocellular carcinoma (HCC) contrast curves. On each curve, we calculated and plotted the optimal temporal window (time period above the lower threshold, which in this experiment was 10 Hounsfield units), the total area under the curve above the lower threshold, and the area within the optimal range.

Results

A. Animal Experiment: At a given concentration and injection rate, an increased volume of contrast medium led to increases in Imax A, P and L. In addition, Tmax A, P, L and Teq were prolonged in parallel with increases in injection time The time-attenuation curve shifted upward and to the right. For a given volume and injection rate, an increased concentration of contrast medium increased the degree of aortic, portal and hepatic enhancement, though Tmax A, P and L remained the same. The time-attenuation curve shifted upward. For a given volume and concentration of contrast medium, changes in the injection rate had a prominent effect on aortic enhancement, and that of the portal vein and hepatic parenchyma also showed some increase, though the effect was less prominent. A increased in the rate of contrast injection led to shifting of the time enhancement curve to the left and upward. B. Computer Simulation: At a faster injection rate, there was minimal change in the degree of hepatic attenuation, though the duration of the optimal temporal window decreased. The area between 10 and 30 HU was greatest when contrast media was delivered at a rate of 2-3 mL/sec. Although the total area under the curve increased in proportion to the injection rate, most of this increase was above the upper threshould and thus the temporal window was narrow and the optimal area decreased.

Conclusion

Increases in volume, concentration and injection rate all resulted in improved arterial enhancement. If cost was disregarded, increasing the injection volume was the most reliable way of obtaining good quality enhancement. The optimal way of delivering a given amount of contrast medium can be calculated using a computer-based mathematical model.     

Contrast enhancement of round atelectases

Purpose:
To find out if round atelectases (RAs) of a lung enhance more than pulmonary malignant tumors. Material and Methods:
Twelve patients with RA and 16 patients with malignant lung tumor (MLT) evidenced on CT examination were selected (14 RAs and 16 MLTs). Two patients had 2 RAs. The examination data were reviewed on a work station and the attenuation values of RAs and tumors were measured. Results:
At enhanced CT the density of RAs varied from 88 to 190 HU whereas for MLTs the density varied from 30 to 71 HU. The difference between attenuation values of RAs and MLTs was statistically significant. Conclusion:
The attenuation values of RAs after contrast enhancement seem to differ from those of MLTs, at least during the first minute after contrast injection, and thus serve as a useful aid in the differential diagnosis of these masses.     

多层螺旋CT头颈部低剂量对比剂血管成像的可行性研究

目的 探讨16排多层螺旋CT低剂量对比剂头颈部血管成像的可行性。资料与方法 30例头颈部CT血管成像(CTA)分为3组．采用不同的对比剂量：100ml、80ml和60ml。根据原始图像和最大强度投影(MIP)重建像评价3组病例颈部动脉、颅内动脉的显示程度、静脉充盈程度以及伪影;并测量动脉内对比剂的浓度。结果 颈动脉、椎动脉及颅内动脉在3组病例中均清晰显示．显示程度评分上3组间无统计学差异。静脉充盈程度和伪影的主观评分亦无显著性差异。3组动脉内的对比剂浓度均维持在较高的水平,统计学无显著性差异。结论 16排多层螺旋CT头颈部血管成像使用低剂量对比剂可以满足临床需要。     

Effect of Contrast Media on Megavoltage Photon Beam Dosimetry

The purpose of this study was to quantify changes in photon beam dosimetry caused by using contrast media during computed tomography (CT) simulation and determine if the resulting changes are clinically significant. The effect of contrast on dosimetry was first examined for a single 6-MV photon beam incident on a plane phantom with a structure of varying electron densities (ρ_e) and thickness. Patient studies were then undertaken in which CT data sets were collected with and without contrast for 6 typical patients. Three patients received IV contrast (Optiray-240™) only and 3 received IV plus oral (Gastrograffin™) contrast. Each patient was planned using conformal multifield techniques in accordance with the department standards. Two methods were used to compare the effect of contrast on dosimetry for each patient. The phantom analysis showed that the change in dose at the isocenter for a single 10 × 10 cm² 6-MV photon beam traversing 10 cm of a contrast-enhanced structure with ρ_e 1.22 was 7.0% (1.22 was the highest average ρ_e observed in the patient data). As a result of using contrast, increases in ρ_e were observed in structures for the 6 patients studied. Consequently, when using contrast-enhanced CT data for multifield planning, increases in dose at the isocenter and in critical structures were observed up to 2.1% and 2.5%, respectively. Planning on contrast-enhanced CT images may result in an increase in dose of up to 2.1% at the isocenter, which would generally be regarded as clinically insignificant. If, however, a critical organ is in close proximity to the planning target volume (PTV) and is planned to receive its maximum allowable dose, planning on contrast-enhanced CT images may result in that organ receiving dose beyond the recommended tolerance. In these instances, pre-contrast CT data should be used for dosimetry.     

注氧气法MSCT仿真内镜技术诊断膀胱肿瘤

评价氧气为对比剂的多层螺旋CT仿真膀胱镜的检查方法、镜下表现及其临床应用价值.材料和方法:对22例膀胱镜拟诊膀胱肿瘤的患者排空膀胱、充满氧气后,行螺旋C T扫描,获得的容积数据进行后处理,重建类似传统膀胱镜的图像.结果:仿真膀胱镜诊断膀胱癌21例,前列腺癌尿道内口周围浸润生长1例,其中最小者肿瘤直径仅为0.3cm,与传统膀胱镜检查结果相符.结论:以氧气为对比剂的多层螺旋CT仿真膀胱镜是一种精确和无创的检查方法,是对传统膀胱镜检查的重要补充,适用于血尿患者和膀胱肿瘤术后随访,检查容易耐受,无并发症.     

Contrast agents in functional MR imaging

Contrast agents have greatly expanded the role of MR imaging (MRI) to allow assessment of physiologic, or “functional,” parameters. Although activation mapping generally does not require contrast agents, other forms of functional MRI, including mapping of cerebral hemodynamics (eg, perfusion imaging), are best done with the use of contrast agents. Serial echo planar images are obtained after bolus injection of lanthanide chelates. Application of susceptibility contrast physics and standard tracer kinetic principles permits generation of relative cerebral blood volume maps. Deconvolution of cerebral blood flow and mean transit time parameters is also possible within technical limitations. By using diffusion and perfusion pulse sequences, an imaging correlate to the ischemic penumbra can be identified. Functional MRI perfusion imaging of intraaxial tumors is analogous to positron emission tomography for delineation of metabolic activity, yet may be even more sensitive to neovascularity and possesses improved image quality. Clinical applications include biopsy site selection and postirradiation follow-up. Further improvements in data analysis and map generation techniques may improve diagnostic accuracy and utility.     

胃壁厚度与口服对比剂量之间关系的研究

目的：研究胃壁厚度与口服对比剂量之间的关系。材料和方法：通过三组６５ 例服用不同量对比剂者胃壁厚度的测量和研究，胃标本扫描模拟胃气液面征现象。结果：表明增强扫描胃扩张良好时胃壁呈均一性增强，中等度扩张时胃内常见到较多的粘膜皱襞，胃扩张不充分时胃襞明显增厚并可显示多层结构。结论：认为测量胃壁厚度时应使胃处于良好的扩张状态。胃扩张不充分时部分病例显示胃气液面征。     

离子型与非离子型MR对比剂对肝脏病变的增强效果比较

目的　对比离子型钆喷酸葡胺 (Gd -DTPA)和非离子型钆双胺MR对比剂 (Gd -DTPA -BMA)在肝脏病变手推团注多时相增强扫描中的增强效果。方法　 5 8例肝脏疾病患者 (男 3 1例 ,女 2 7例 ,年龄 3 0～ 77岁 )分 2组 ,第 1组 :3 0例 (男 16例 ,女 14例 ) ,采用Gd -DTPA -BMA。第 2组 :2 8例 (男 17例 ,女 11例 ) ,采用Gd -DTPA。行MR手推团注多时相增强扫描。结果　Gd -DTPA -BMA组 :增强效果满意者 2 3例 (77% ) ,增强效果一般者 6例 (2 0 % ) ,增强效果差者 1例 (3 % )。Gd -DTPA组 :增强效果满意者 2 2例(79% ) ,增强效果一般者 6例 (2 1% )。结论　在肝脏疾病MR手推团注多时相增强扫描中 ,Gd -DTPA -BMA和Gd -DTPA均可达到满意的增强效果 ,安全及有效性两者无显著性差异。Gd -DTPA -BMA粘滞度小 ,利于快速推注。     

硬化型肝癌的螺旋CT多期扫描表现

目的：分析总结硬化型肝癌的螺旋CT多期扫描表现，以进一步提高对该病的诊断准确性。材料和方法：经手术证实的7例硬化型肝癌患者行螺旋CT平扫和多期增强扫描。注射造影剂后30s开始动脉期扫描，70s开始门脉期扫描，另有4例加做3—4min的延迟期扫描，观察病灶的强化方式。结果：平扫7个病灶均为低密度。动脉期6个病灶有轻度的不规则环形、点状或结节状强化，1例无强化。门脉期7个病灶均有不同程度的强化，如不规则环形强化、边缘结节状强化或中心强化等，强化范围较动脉期增大。延迟期4个病灶仍有各种各样的强化表现。结论：硬化型肝癌的螺旋CT多期扫描表现特殊，以早期轻度强化、门脉期和(或)延迟期仍有持续强化为主，需认真与血管瘤及炎性假瘤鉴别，了解其CT表现有助于临床正确诊断和治疗方案的选择。     

Comparison of liver perfusion parameters studied with conventional extravascular and experimental intravascular CT contrast agents

RATIONALE AND OBJECTIVES: To compare liver perfusion parameters obtained by using an extravascular contrast agent and a blood-pool agent. MATERIALS AND METHODS: Fifteen rabbits were imaged with a continuous 40-second single-slice computed tomography acquisition after a bolus injection of contrast agent (physiologic bolus duration 4-5 seconds, extravascular iohexol, n = 7; experimental nanoparticulated blood-pool agent WIN8883, n = 8). Time-density curves were generated for the aorta, portal vein, and liver. From the curves, arterial, portal, and total blood flows and hepatic perfusion index (HPI, arterial-to-total perfusion ratio) were determined by using two commonly applied fundamentally different analyzing methods: the single-compartment model and the peak gradient (PG) method. Also, the gamma variate fitting method was used. RESULTS: By using the single-compartment model, the obtained HPI and total blood flow were 0.14 +/- 0.04 and 2.29 +/- 0.40 (mL/min/mL(tissue)) for WIN8883, and 0.15 +/- 0.06 (P = .54) and 4.60 +/- 1.14 (mL/min/mL(tissue)) (P = .0002) for iohexol, respectively. With the PG, HPI and total blood flow were 0.15 +/- 0.08 and 1.27 +/- 0.24 (mL/min/mL(tissue)) for WIN8883, and 0.20 +/- 0.06 (P = .12) and 2.11 +/- 0.25 (mL/min/mL(tissue)) (P = .00002) for iohexol, respectively. With the blood pool agent, similar contrast enhancement to the conventional agent was achieved with about 36% reduced dosage of iodine per body weight (mg I/kg). CONCLUSIONS: HPI was found to be quite insensitive to different contrast agent types and analyzing methods. However, the arterial, portal and total liver blood flow values strongly depend on contrast agent type and modeling method.     

对比剂流量对腹部脏器CT增强的影响

目的:研究静脉注射CT对比剂与最佳CT扫描时间的关系。材料和方法:25例分成5组,以1.5ml/kg体重静脉注射对比剂,流量分别为2、3、4、5和6ml/s。采用电子束CT多层流动模式对腹部进行扫描,获得肝脏、胰腺、脾脏等的时间-密度曲线。分析比较各组腹部脏器多个兴趣区对比剂到达峰值的时间(PT)、上升时间(RT)、平均通过时间(MTT)、到达峰值的CT值(PV)和上升CT值(RV)。结果:腹部脏器的PT、RT、MTT随对比剂流量升高明显缩短(p<0.05)。当对比剂流量超过3ml/s时腹部多数脏器可达到较好的增强效果。结论:当对比剂剂量相对固定时腹部脏器最佳扫描时间窗应随对比剂流量改变而改变。为提高诊断的准确性应选择较快速的对比剂流量(≥3ml/s)。     

宝石能谱CT在降低肾动脉成像对比剂浓度和用量中的应用研究

目的 探讨宝石能谱CT在降低肾动脉CT血管成像(CTA)对比剂浓度和用量中的应用价值.方法 50例临床怀疑肾血管源性高血压患者行肾动脉CTA,随机分为两组,两组对比剂用量均为1ml/kg,其中26例采用传统模式扫描,其对比剂浓度为350 mgI/ml;另一组(24例)采用宝石能谱CT扫描模式,其对比剂浓度稀释一半,为175 mgI/ml,选取能谱CT组肾动脉和肌肉之间具有最佳对比噪声比(CNR)的单能量图像,比较其与传统图像肾动脉CT值及CNR、背景肌肉噪声及主观评分间的差异.结果 能谱CT成像所用对比剂浓度较传统CT成像减少了一半(175 mgI/ml vs 350 mgI/ml,P＜0.0001),所用碘含量也明显下降(11.96 gI vs 25.63 gI,P＜0.0001).能谱CT成像所得最佳单能量图像上,肾动脉CT值明显高于传统模式成像图像,而两组的CNR、主观评分及剂量长度乘积之间差异无统计学意义.结论 能谱CT成像能够有效降低肾动脉CTA所需对比剂浓度及用量,可在临床尤其是肾动脉不全患者中推荐使用.