Contrast between hypervascularized liver lesions and hepatic parenchyma: early dynamic PET versus contrast-enhanced CT

Objectives

To detect hypervascularized liver lesions, early dynamic (ED) ¹⁸F-FDG PET may be an alternative when contrast-enhanced (CE) imaging is infeasible. This retrospective pilot analysis compared contrast between such lesions and liver parenchyma, an important objective image quality variable, in ED PET versus CE CT.

Materials and methods

Twenty-eight hypervascularized liver lesions detected by CE CT [21 (75 %) hepatocellular carcinomas; mean (range) diameter 4.9 ± 3.5 (1–14) cm] in 20 patients were scanned with ED PET. Using regions of interest, maximum and mean lesional and parenchymal signals at baseline, arterial and venous phases were calculated for ED PET and CE CT.

Results

Lesional/parenchymal signal ratio was significantly higher (P < 0.005) with ED PET versus CE CT at the arterial phase and similar between the methods at the venous phase.

Conclusion

In liver imaging, ED PET generates greater lesional–parenchymal contrast during the arterial phase than does CE CT; these observations should be formally, prospectively evaluated.     

Multidetector multiphase contrast-enhanced liver CT: prospective study comparing two contrast material injection rates on vascular and liver parenchyma enhancement in patients with varied cirrhotic status

BACKGROUND: To compare 2 rates of contrast material injection, with dose tailored to patient body weight (bw) and automatic bolus triggering system, on vascular and liver parenchyma enhancement at multidetector multiphase contrast-enhanced liver computed tomography (CT) of patients with varied cirrhotic status. METHODS: One hundred and thirty consecutive patients with varied cirrhotic status, referred for contrast-enhanced liver CT evaluation of focal liver nodule(s), were prospectively and randomly assigned to 1 of 2 routine contrast-enhanced liver CT protocols: 2 mL/kg of bw of a nonionic contrast agent (300 mg I/mL) injected at a 3 mL/sec, versus 2 mL/kg of bw of the same contrast agent injected at 4 mL/sec. Quantitative vascular and liver parenchyma enhancements were obtained. Attenuation values of the abdominal aorta during the arterial phase CT, of the main portal vein during the portal venous phase CT, and of the liver parenchyma during the arterial, the portal venous, and the equilibrium phases liver CT, were compared with multiple 2-way analysis of variance. RESULTS: Significantly higher attenuation values were noted in the abdominal aorta with a 4-mL/sec-flow rate. Attenuation values were not significantly different in the portal vein and in the liver parenchyma, whatever was the patient cirrhotic status. CONCLUSIONS: With dose tailored to body weight and automatic bolus triggering system, adjusting flow rate makes no difference in patients with regard to liver or portal vein enhancement, regardless of presence/absence of cirrhosis.     

Standardisation of liver MDCT by tracking liver parenchyma enhancement to trigger imaging

Objective  

To assess parenchymal bolus-triggering in terms of liver enhancement, lesion-to-liver conspicuity and inter-image variability across serial follow-up MDCTs.     

MDCT肝实质强化示踪触发成像的标准化

目的以肝脏强化、病灶相对于肝脏的显示度以及系列随访多层螺旋CT(MDCT)的影像间的差异性来评价肝实质增强团注触发技术。方法回顾性分析50例肝转移瘤病人的MDCT影像,他们均行1次基础CT和2次随访CT检查。在25例病人中设置肝实质CT强化阈值为50HU时开     

Focal liver masses: enhancement patterns on contrast-enhanced images--concordance of US scans with CT scans and MR images

PURPOSE: To assess prospectively the concordance of enhancement patterns of focal liver masses on contrast material-enhanced ultrasonographic (US) scans with patterns on contrast-enhanced computed tomographic (CT) scans or magnetic resonance (MR) images. MATERIALS AND METHODS: This study was approved by the institutional review board; patients gave informed consent. Contrast-enhanced US and contrast-enhanced CT or MR imaging were performed in 135 patients (62 men, 73 women; mean age, 51 years) with 144 confirmed liver masses. Masses included 49 hepatocellular carcinomas, 13 metastases, 30 hemangiomas, 41 lesions of focal nodular hyperplasia, and 11 others. Randomized image sets from each modality were shown independently to three blinded readers, who answered identical questions about enhancement of the lesion and liver in the arterial and portal venous phases and changes with time. Concordance for modalities was calculated from answers of readers and consensus answers between readers, with 95% confidence intervals (CIs). The kappa values were calculated for interreader agreement. RESULTS: Features of arterial phase enhancement showed concordance of more than 76% for modalities. The highest concordance of 92% (132 of 144), with 95% CI of 86% and 95% (kappa>0.84), was for the presence of peripheral pools and centripetal progression. Concordance in the portal venous phase was lower, with agreement for predominant enhancement of the lesion in 61% (86 of 142), with 95% CI of 52% and 68% (kappa>0.83). Portal venous phase washout occurred in 75% (106 of 142), with 95% CI of 67% and 81% (kappa>0.81). The majority of discordances were for malignancies for which only US depicted no sustained enhancement in the portal venous phase. CONCLUSION: US shows high concordance with CT or MR imaging, especially for the arterial phase. Discordance in the portal venous phase may reflect the tendency of CT and MR contrast agents, unlike microbubbles, to diffuse into interstitium.     

Contrast enhancement of liver parenchyma and biliary tract related to liver function at delayed computed tomography

Computed tomography (CT) of the liver was performed in 53 patients before, during and 4 to 6 hours after intravenous administration of approximately 60 g of iodine in metrizoate. At delayed CT, contrast medium was observed in the extrabiliary ducts in 20 patients (38%) and in the gallbladder in 28 (68%) of the 41 patients with no previous cholecystectomy. The increase in attenuation of liver parenchyma at delayed CT compared with the non-enhanced baseline CT ranged between 2 and 26 HU (mean 13.9). The material was divided into three groups with regard to liver function: normal, intermediate and pathologic. In the normal group contrast medium was observed in the gallbladder in 81 per cent and in the bile ducts in 57 per cent and the mean increase in attenuation of the liver parenchyma was 14.5 HU. In the pathologic group the same parameters were 40 per cent, 7 per cent and 10.6 HU, respectively. Contrast medium in the gallbladder and biliary ducts improved the information about anatomy. Pathology of the gallbladder and tumour growth along the hepatoduodenal ligament were better demonstrated. Delayed CT is a simple and non-invasive technique that may improve planning of liver surgery.     

Dynamic contrast-enhanced three-dimensional MR imaging of liver parenchyma: source images and angiographic reconstructions to define hepatic arterial anatomy

PURPOSE: To assess the accuracy of an interpolated breath-hold T1-weighted three-dimensional (3D) gradient-echo (GRE) magnetic resonance (MR) imaging sequence with near-isotropic pixel size (相似文献   

Liver perfusion in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI): comparison of enhancement in Gd-BT-DO3A and Gd-EOB-DTPA in normal liver parenchyma

Purpose

Within-patient comparison of the enhancement patterns of normal liver parenchyma after gadobutrol and gadoxetate disodium, with emphasis on the start of hepatocytic uptake of gadoxetate disodium.

Materials and methods

Twenty-one patients (12 female, 9 male) without chronic liver disease underwent 1.5-T contrast-enhanced MRI twice, once with an extracellular contrast agent (gadobutrol) and once with a hepatospecific agent (gadoxetate disodium), using a T1-weighted keyhole sequence. Fifteen whole-liver datasets were acquired up to 5 min for both contrast agents and two additional datasets, up to 20 min, for gadoxetate. Signal intensities (SI) of the parenchyma, aorta and portal vein were measured and analysed relative to pre-contrast parenchymal SI.

Results

After gadoxetate, in 29 % of the patients the parenchymal SI decreased by ≥5 % after the initial vascular-phase-induced peak, while in the other 71 % the parenchymal SI remained stable or gradually increased until up to 20 min after the initial peak. The hepatocytic gadoxetate uptake started at a mean of 37.8 s (SD 14.7 s) and not later than 76 s after left ventricle enhancement.

Conclusion

Parenchymal enhancement due to hepatocytic uptake of gadoxetate can start as early as in the late arterial phase. This may confound the assessment of lesion appearance as compared to extracellular contrast such as gadobutrol.

Key Points

? Gadoxetate-enhanced liver MRI results in early enhancement of normal parenchyma in patients ? The start of the hepatobiliary phase coincides with the late arterial phase ? This may confound the assessment of lesion appearance compared to extracellular contrast ? Different parenchymal enhancement patterns after gadoxetate were found for normal parenchyma     

Multiphase contrast-enhanced CT of the liver with a multislice CT scanner

Our objective was to assess the effects of the injection rate of contrast material and of a 5% dextrose flush on enhancement in multiphase hepatic CT using a multislice CT scanner. Most patients had chronic hepatitis and/or liver cirrhosis. One hundred eighty examinations, in which two sequential acquisitions were performed during a single breath-hold followed by third- and fourth-pass acquisitions, were randomized into four protocols: contrast injection at 0.1 ml/kg body weight s^–1 over 21 s without and with a 30-ml flush in groups 1 and 2, respectively, and contrast injection at 0.07 ml/kg body weight s^–1 over 30 s without and with a flush in groups 3 and 4, respectively. Contrast enhancement in each acquisition was measured in the aorta, portal vein, and liver. The visualization of hepatic arterial branches was scored by visual assessment. The highest aortic enhancement was observed in the first-pass acquisition in all groups. At the higher injection rate (groups 1 and 2), aortic enhancement in the first-pass acquisition was significantly more intense, whereas portal venous and hepatic enhancement was significantly less intense. The use of a flush considerably improved aortic enhancement at the beginning of the second-pass acquisition. In the visual assessment of hepatic arterial branches, the protocols with the higher injection rate received significantly higher grades. Multislice CT permits the entire liver to be imaged during an almost exclusively arterial phase by shortening the injection duration for a given volume of contrast material. Electronic Publication     

超声造影与CT增强扫描对肝占位性病变的诊断价值比较

目的 :对比超声造影与CT增强扫描在肝占位性病变中的诊断价值,为临床诊断肝占位性病变提供参考依据。方法 :回顾性分析71例肝占位性病变患者的临床资料,比较超声造影与CT增强扫描的诊断阳性率,对比2种检查方法的诊断价值。结果:超声造影对肝癌、肝血管瘤及肝局灶性结节增生的诊断阳性率分别为83.33%、88.00%及82.14%,而CT增强扫描分别为88.89%、92.00%及85.71%,2种检查方法的诊断阳性率比较差异无统计学意义(P0.05)。此外,2种检查方法对肝癌、肝血管瘤及肝局灶性结节增生均具有较高的诊断效能(P0.05)。结论:超声造影与CT增强扫描对肝占位性病变的诊断价值相当。     

Inversion of gallbladder secondary to traumatic herniation of liver: CT findings

This report describes the CT and radioisotope diagnosis of a suprahepatic gallbladder with partial inversion of the liver resulting from traumatic rupture of the diaphragm.     

Enhancement patterns of focal liver masses: discordance between contrast-enhanced sonography and contrast-enhanced CT and MRI

OBJECTIVE: The purpose of this study was to investigate the origin of the infrequent discordance between the contrast enhancement patterns of liver lesions on sonography and those on CT and MRI. Forty-four discordant cases were reviewed retrospectively. CONCLUSION: Four categories of discordance were identified, one of which is unexplained. Contrast agent diffusion caused portal venous phase discordance in malignant tumors (n = 6) whereby CT and MRI contrast material diffused through the vascular endothelium into the tumor interstitium, concealing washout. Sonographic microbubbles were purely intravascular and showed washout. Arterial phase timing discordance occurred in metastatic lesions (n = 10) with hypervascularity and rapid washout on contrast-enhanced sonography. CT arterial imaging performed later showed hypovascularity. Rapidly enhancing hemangiomas (n = 7) exhibited hypervascularity on CT when contrast-enhanced sonography also showed peripheral nodules and fast centripetal progression. Discordance caused by fat in lesions (n = 4) or liver (n = 10) reflected the inherent echogenicity of fat on sonography compared with its low attenuation on CT and low signal intensity on MRI. Infrequent cases of discordance remain unexplained. Recognition of the cause of the infrequent disagreement in enhancement patterns on contrast-enhanced sonography with those on CT and MRI improves diagnostic interpretation.     

Re-evaluation of pheochromocytomas on delayed contrast-enhanced CT: washout enhancement and other imaging features

The purpose of this study was to retrospectively evaluate the enhancement washout and other imaging features of pheochromocytomas on delayed contrast-enhanced CT. Twenty-four patients with 31 pathologically confirmed pheochromocytomas were examined using unenhanced, early and delayed contrast-enhanced CT. The range of their APEW (absolute percentage of enhancement washout) or RPEW (relative PEW) values was analyzed. The other CT features including cystic or necrotic change, calcification, and hemorrhage were also determined by a pathologic correlation. Of the 31 pheochromocytomas, 10 (32%) had APEW values of 60% or less and RPEW values of 40% or less. Fourteen (45%) had APEW values >60% and RPEW values >40%. CT showed cystic or necrotic changes in 11 pheochromocytomas (35%) and calcification (10%) in 3. Nineteen pheochromocytomas showed cystic or necrotic changes on early contrast-enhanced CT, but eight of these lesions showed late enhancement on delayed contrast-enhanced CT, which pathologically corresponded to myxoid degeneration. The unenhanced CT showed hemorrhage in 23 pheochromocytomas, but the pathology examinations showed hemorrhage in 15 lesions. Many pheochromocytomas can be misdiagnosed as adenomas on CT due to the high enhancement washout values. Delayed contrast-enhanced CT can detect myxoid degeneration with late enhancement, which is seen as a cystic or necrotic change on early contrast-enhanced CT.     

双能量CT在肝实质弥漫性疾病中的应用进展

双能量CT是一种采用2种不同能量进行数据采集的成像技术,可选择多种算法进行影像后处理。基于物质分离算法的双能量CT可以定量分析肝实质内的脂肪、铁、碘等物质,有助于早期评估肝实质弥漫性疾病及其严重程度,为肝实质弥漫性疾病的早期诊断及其发展的监测提供了一种新的影像学方法。综述近年来双能量CT在脂肪肝、肝铁沉积症、肝硬化等肝实质弥漫性疾病方面的应用进展。     

"类血管瘤样强化":肝转移癌化疗后的特殊CT表现

目的:探讨化疗后肝转移瘤在CT扫描中出现类似血管瘤样强化的意义。方法:回顾7例(共10个)CT扫描中出现类似血管瘤样强化的化疗后肝转移瘤,并分析病灶的大小、密度和强化特征。结果:本组10个病灶中最小0.7cm,最大3.5cm,10个病灶平扫为低密度,其中7个边界清楚,3个边界不清;增强后病灶为边缘不均匀强化(6个)或无明显强化(4个),门脉期或延迟后均见对比剂均匀充填。结论:肝转移瘤化疗后CT扫描可出现“类血管瘤样强化”,应引起足够重视。