Reversible MR changes in the cat brain after cerebral fat embolism induced by triolein emulsion

BACKGROUND AND PURPOSE: Clinical cerebral-fat embolism shows both reversible and irreversible changes. We used MR imaging to investigate the reversibility of embolized lesions induced with a fat-emulsion technique and to evaluate the histologic findings. METHODS: A fat emulsion was made with 0.05 mL of triolein and 20 mL of normal saline and vigorous to-and-fro movement through a three-way stopcock. In 50 cats, the internal carotid artery was infused with the fat emulsion. Cats were divided into six groups on the basis of time delay after embolization: 1 hour; 1 and 4 days; and 1, 2, and 3 weeks. MR imaging and histologic examination were performed at these times. RESULTS: Embolized lesions were hyperintense on T2-weighted images, isointense or mildly hyperintense on diffusion-weighted images, isointense on apparent diffusion coefficient maps, and enhancing on gadolinium-enhanced T1-weighted images at 1 hour. These MR imaging findings were less evident at day 1 and reverted to normal after day 4 (isointense on all images). Electron microscopy showed minimal findings in the cortical lesion in groups 1 and 2 (group 1 at 1 hour and group 2 at 1 hour and 1 day). Light microscopic findings revealed evidence of necrosis-small focal gliosis and demyelination in the periventricular white matter-in only one cat. The number of intravascular fat globules was not significantly different between groups, as visualized by oil red O staining. CONCLUSION: Cerebral-fat embolism induced by a triolein emulsion revealed reversible MR findings and minimal histologic findings.     

Experimental pulmonary fat embolism induced by injection of triolein in rats

The relationship between the volume of fat flowing in the bloodstream and the degree of pulmonary fat embolism has remained unclear. In this study, in order to examine whether the volume of fat particles in the bloodstream could be estimated from the degree of pulmonary fat embolism, 0.05, 0.1, 0.15, 0.2 and 0.25 ml of triolein were injected into male rats weighing 300-320 g, through the caudal vein. Consequently, it was noted that the severity of pulmonary fat embolism tended to gradually increase in proportion to the volume of injected triolein, with the severity of pulmonary fat embolism being significantly augmented by the injection of 0.2 and 0.25 ml of triolein, based on morphometric analysis. In application to human cases, about 60 ml of fat particles was estimated to flow into the bloodstream after the occurrence of a pelvic fracture. Moreover, the results of this study led to the hypothesis that the prognosis of pulmonary fat embolism is affected by the severity of preceding conditions which have caused fat embolism.     

脂肪乳注射液治疗碘油脑栓塞的实验研究

目的 探讨脂肪乳注射液对颅内碘油清除的作用.方法 12只家兔按随机数字表法分成2组,对照组、实验组各6只,均通过颈内动脉穿刺注入超液态碘油(0.06 ml/kg),CT扫描发现脑内有碘油沉积为造模成功.实验组造模成功后即刻经静脉注射脂肪乳(20 ml/kg),并于其后每隔24h,即术后24、48、72、96、120 h分别注射1次脂肪乳,共6次,并于上述时间点及术后144h各行1次头颅CT扫描.对照组不做治疗,并于相同时间点行CT扫描.选取碘油沉积最明显的0.1 cm×0.1 cm ROI测量CT值.2组间不同时点比较采用重复测量的方差分析,2组间相同时点比较采用两独立样本t检验,并观察动物的临床症状变化情况.结果 术后24、48、72、96、120、144h,对照组ROI CT值分别为(103.8±7.1)、(91.0±4.2)、(79.5±5.5)、(67.8±6.6)、(53.9±5.1)、(39.9±3.1)HU,实验组相应时间点ROICT值分别为(90.7±5.4)、(74.1±4.6)、(62.9±4.5)、(48.1±3.1)、(39.1±1.3)、(38.8±1.2)HU.重复测量的方差分析显示,2组间不同时间点CT值差异有统计学意义(F=201.30,P＜0.01).两独立样本t检验比较显示,2组间术后24～ 120 h相同时间点CT值的差异有统计学意义(t值分别为3.60、6.64、5.72、6.62、6.89,P值均＜0.01).造模成功后,所有动物均出现不同程度卒中症状,实验组临床症状完全消失较对照组提前24 h.结论 脂肪乳注射液能加速颅内碘油清除,本实验为临床应用脂肪乳治疗碘油脑栓塞提供了一定的理论依据.     

Experimental cerebral fat embolism: embolic effects of triolein and oleic acid depicted by MR imaging and electron microscopy

BACKGROUND AND PURPOSE: In fat embolism, free fatty acid is more toxic than neutral fat in terms of tissue damage. We evaluated the hyperacute embolic effects of triolein and oleic acid in cat brains by using MR imaging and electron microscopy. METHODS: T2-weighted imaging, diffusion-weighted imaging, and contrast-enhanced T1-weighted imaging were performed in cat brains after the injection of triolein (group 1, n = 8) or oleic acid (group 2, n = 10) into the internal carotid artery. MR images were quantitatively assessed by comparing the signal intensity ratios of the lesions with their counterparts on T2-weighted images, apparent diffusion coefficient (ADC) maps, and contrast-enhanced T1-weighted images. Electron microscopic findings in group 1 were compared with those in group 2. RESULTS: Qualitatively, MR images revealed two types of lesions. Type 1 lesions were hyperintense on diffusion-weighted images and hypointense on ADC maps. Type 2 lesions were isointense or mildly hyperintense on diffusion-weighted images and isointense on ADC maps. Quantitatively, the signal intensity ratios of type 1 lesions in group 2 specimens were significantly higher on T2-weighted images (P =.013)/(P =.027) and lower on ADC maps compared with those of group 1. Electron microscopy of type 1 lesions in both groups revealed more prominent widening of the perivascular space and swelling of the neural cells in group 2, in contrast to notable endothelial defects in group 1. CONCLUSION: MR and electron microscopic data on cerebral fat embolism induced by either triolein or oleic acid revealed characteristics suggestive of both vasogenic and cytotoxic edema in the hyperacute stage. Tissue damage appeared more severe in the oleic acid group than in the triolein group.     

Hemorrhage in cerebral fat embolisms in a cat model using triolein dependent on the physical properties of triolein

Purpose

Hemorrhage is a finding of clinical fat embolism syndrome. The purpose of the present study was to evaluate the occurrence of hemorrhage in the cat brain by SW MR imaging after infusion of triolein as a bolus or as an emulsion into the carotid artery.

Materials and methods

Twenty-two cats were divided into two groups according to the type of triolein infused: group 1 (n = 11) was infused with a 0.1 ml triolein bolus, group 2 (n = 11) with triolein emulsion containing 0.1 ml triolein in 20 ml saline. SW imaging was performed before and after triolein infusion (at 2 h, 1 and 4 days). After MR imaging on day 4, cats were sacrificed and brains were immediately excised. Hemorrhage was evaluated using H&E staining.

Results

Hemorrhage was observed in eight cats in group 1, in no cats in group 2. Hemorrhage on SW images was found to correspond with light microscopy.

Conclusions

SW images revealed hemorrhage in lesion hemispheres infused with triolein bolus. However, there was no evidence of hemorrhage infused with emulsified triolein. Thus, the occurrence of hemorrhage in cerebral fat embolism may depend on fat status.     

MRI findings in cerebral fat embolism

The purpose of this retrospective study was to demonstrate the MRI features of cerebral manifestations in patients with fat embolism syndromes in comparison with cerebral CT (CCT). Magnetic resonance imaging was performed according to standard protocols revealing multiple small non-confluent hyperintense intracerebral lesions larger than 2 mm on proton-density and T2-weighted images to various extents in three of four patients with clinically suspected cerebral fat embolism. Cerebral CT was negative in all patients. Our findings confirm that MRI can detect cerebral fat embolism with a higher sensitivity than CCT. Thus, MRI should be the first choice for imaging of cerebral fat embolism. Received 28 November 1997; Revision received 9 March 1998; Accepted 30 March 1998     

Reversible cytotoxic cerebral edema in cerebral fat embolism

We present a case of cerebral fat embolism (CFE) that demonstrated evidence of diffuse white matter cytotoxic edema on diffusion-weighted magnetic resonance imaging, in addition to punctate hyperintensities on T2-weighted and diffusion-weighted imaging. The case suggests that CFE represents a combination of occlusive arteriolar disease and secondary neurotoxicity.     

脑脂肪栓塞的MRI诊断价值

目的：研究MIU对脑脂肪栓塞的影像学诊断及其临床价值。方法：回顾性分析了25例经临床诊断为脂肪栓塞综合征(FES)的脑部MRI资料。MRI检查采用0．3T、0．5T低场强设备，行常规SE T1WI、FSE T2WI和FI FLAIR，16例病人在发病后1～3月内行MRI复查，CT检查22例。结果：脑脂肪栓塞(CFE)的MRI表现为散在多发、对称分布的点、片状等或长T1长T2信号灶，边缘多较模糊，主要位于基底节区、脑干深部、深部白质及分水岭区白质。MRI复查示随脑内病灶的吸收，病人症状得到不同程度的改善，因此，MRI对判断预后及指导治疗具有重要意义。结论：MRI可为CFE的诊断提供直接的证据，应作为诊断CFE的常规手段。     

The steroid effect on the blood-ocular barrier change induced by triolein emulsion as seen on contrast-enhanced MR images.

OBJECTIVE: The purpose of this study is to evaluate the effect of dexamethasone on the damaged blood-ocular barrier caused by triolein emulsion, using contrast-enhanced MR imaging. MATERIALS AND METHODS: An emulsion of 0.1-mL triolein in 20 mL of saline was infused into the carotid arteries of 32 cats, 12 cats were placed in the treatment group and 18 cats were placed in the Control group. Thirty minutes after the infusion of triolein emulsion, a set of orbital pre- and post-contrast T1-weighted MR images (T1WIs) were obtained. Infusion of 10 mg/kg dexamethasone into the ipsilateral carotid artery of each of the cats in the treatment group cats and 20 mL saline in each of the cats in the control group was given. A second set of pre- and post-contrast orbital T1WIs were obtained three hours following triolein emulsion infusion. Qualitative analysis was performed for the the anterior chamber (AC), the posterior chamber (PC), and in the vitreous humor of the ipsilateral and contralateral eyes. The signal intensity ratios of the ipsilateral eye over the contralateral eye were quantitatively evaluated in the three ocular chambers on the first and second set of T1WIs, and were then statistically compared. RESULTS: Qualitatively, the AC, the PC or the vitreous did not show immediate contrast enhancement on the first and the second set of post-contrast T1WIs. However, the AC and the PC showed delayed contrast enhancement for both groups of cats on the second pre-contrast T1WIs. No enhancement or minimally delayed enhancement was seen for the vitreous humor. Quantitatively, the signal intensity ratios in the PC of the treatment group of cats were statistically lower than the ratios of the control group of cats for the second set of T1WIs (p = 0.037). The AC and vitreous showed no statistically significant difference between the feline treatment group and control group (p > 0.05). CONCLUSION: Contrast-enhanced MR images revealed increased vascular permeability in the PC of the eye after infusion of triolein emulsion. Dexamethasone seems to decrease the breakdown of the blood-aqueous barrier in the PC.     

Magnetic resonance imaging of cerebral fat embolism

Summary The cerebral fat embolism is a potentially serious complication of fractures but clinical cases often go undiagnosed. Two cases of clinically diagnosed cerebral fat embolism are reported, and MR images of these patients are described. While brain CT revealed no abnormality, MR imaging showed relative low-intensity areas on T1-weighted images and high-intensity areas on T2-weighted images. In one patient follow-up MR showed nearly complete resolution of the abnormal signal. MR imaging appears to be valuable for detecting the lesions in these patients.     

脑脂肪栓塞的MRI及CT诊断

目的 总结脑脂肪栓塞(CFE)的临床及MRI及CT的影像特点。方法 分析3例急性CFE的临床表现、影像特点。结果 (1)3例均为长骨骨折，在外伤后或骨折固定、复位数小时后突发精神状态改变。(2)醒状昏迷是主要临床表现。(3)3例患者MRI能明确显示病灶，1例CT显示了病灶。(4)MRI、CT显示脑内病灶均呈基本对称性分布，为边缘模糊的点、片状长T1、长T2信号，CT呈低密度。病灶均累及脑干、分水岭区脑白质、基底节区、胼胝体压部。2例病灶累及小脑。(5)1例患者发病康复治疗3个月后MRI复查示脑内病灶完全消失。结论 急性脑脂肪栓塞的临床及MRI、CT影像改变具有特征性，MRI在病灶显示上优于CT。     

Effect of triolein emulsion on the blood-testis barrier in cats

PURPOSE: Although the blood-testis barrier (BTB) is beneficial physiologically, it acts as an obstacle to chemotherapy. We wished to determine whether a triolein emulsion could alter the permeability of the BTB in cats. MATERIALS AND METHODS: An emulsion of 0.05-mL triolein in 20 mL of saline was infused into the abdominal aorta just proximal to the branching of the renal arteries of each of 15 cats (embolic group). As controls, 12 cats were each similarly infused with 20 mL of normal saline (control group). Pre and postcontrast MR images were obtained 30 minutes and 2 hours after embolization. The images were analyzed for the presence and degree of contrast enhancement (qualitative analysis), and the contrast enhancement ratios (CER) derived from one testis of each animal were compared and statistically analyzed by the mixed linear model (quantitative analysis). RESULTS: Contrast enhancement of the testis was observed in both groups at both time points, but it was more prominent in the embolic group. The CERs in the embolic group (0.63 at 30 minutes, 0.42 at 2 hours) were significantly higher than in the control group (0.36 at 30 minutes, 0.28 at 2 hours; P = 0.0001). In each group, the CERs at 2 hours were significantly lower than those at 30 minutes (P = 0.006). CONCLUSION: Intra-arterial infusion of triolein emulsion increased the permeability of the BTB. This result may be useful in future studies of BTB disruptions caused by fat emulsions.     

脑脂肪栓塞的CT和MRI诊断(附3例分析)

目的 :分析脑脂肪栓塞 (CFE)的CT和MRI表现 ,以提高对此病的早期诊断。方法 :对 3例CFE患者的临床及CT和MRI资料进行分析。结果 :3例CFE患者CT检查均为阴性 ,MRI示双侧额叶皮层下脑白质区、基底节、放射冠、半卵圆中心区多发散在点状异常信号影 ,1例T1WI表现为低信号 ,2例未见异常 ,3例T2 WI均表现为点状较高信号 ,DWI上 3例均有点状高信号。结论 :有近期骨折病史者 ,一旦出现神经系统症状 ,要想到CFE的可能 ,应早期行颅脑MRI检查 ,常规选择T1WI、T2 WI和DWI多种序列成像技术进行检查。     

正常成人多层螺旋CT灌注成像的脑血流动力学研究

目的　探讨多层螺旋CT灌注成像 (MSCTPI)技术在正常人脑血流动力学中的应用。方法　选择 30例正常成年人行常规头颅CT平扫后 ,再行MSCTPI检查。在常规轴面CT扫描后选取基底节及其相邻层面 ,经肘静脉团注对比剂 ,同时开始连续 4 0s的双层动态扫描 ,重建的 80幅动态图像使用CT脑灌注软件包进行处理 ,获得灌注图像 ,测量所选脑内感兴趣区的血流量、血容量及达峰时间 ,并对其进行定量分析。结果　MSCTPI显示正常成年人脑灰质灌注高于脑白质 ,脑灰质的平均血流量、平均血容量、达峰时间分别为 (5 0 6± 9 0 )ml·min-1·10 0 g-1、(5 7 8± 9 1)ml·min-1·10 0 g-1、(10 6± 1 6 )s,脑白质分别为 (2 2 7± 8 6 )ml·min-1·10 0 g-1、(30 8± 9 8)ml·min-1·10 0g-1、(12 9± 2 6 )s。结论　MSCTPI技术为测量脑血流动力学指标提供了一种新的影像学方法。     

超早期脑梗死CT灌注表现的实验性研究

目的 :研究兔的脑梗死模型在缺血后 6h内各时间段CT灌注影像表现。方法 :健康成年新西兰白兔 42只 ,采用改良O′Brein法制作局灶性脑缺血模型 ,于术后 0 .5、1、2、3、4、6h不同时间段进行CT灌注扫描 ,图像用PerfusionCT/VA 10B软件处理。测量并计算缺血区的相对面积。在各时间段取兔脑组织切片 ,进行红四氮唑 (TTC)染色比较。结果 :①从缺血 0 .5h开始 ,CT灌注血流功能图上可见“斑状”分布缺血灶 ,缺血中心区在各功能图上的表现比较一致 ,缺血边缘区改变在TP图上最明显 ,侧支循环区改变只表现在TS、TP图。② 0 .5、1h时间段兔脑TTC染色未见明显改变 ,4～6h可见缺血区从基底节向颞叶皮层发展。结论 :CT灌注成像与TTC染色表现一致 ,能够在早期反应缺血灶的变化 ,是超早期脑梗死比较敏感、稳定、快速的诊断技术。     

Magnetic resonance imaging and histologic findings of experimental cerebral fat embolism

RATIONALE AND OBJECTIVES: The purpose of this study was to determine whether cerebral fat embolism demonstrated reversible or irreversible findings in magnetic resonance (MR) imaging over time and to compare the features in MR images with histologic findings in a cat model. MATERIALS AND METHODS: MR images were obtained serially at 2 hours, 1 and 4 days, and 1, 2, and 3 weeks after embolization with 0.05 mL of triolein into the internal carotid artery in 19 cats. Any abnormal signal intensity and change in the signal intensity were evaluated on T2-weighted images, T1-weighted images, diffusion-weighted images (DWIs; including apparent diffusion coefficient [ADC] maps), and gadolinium-enhanced T1-weighted images (Gd-T1WI) over time. After MR imaging at 3 weeks, brain tissue was obtained and evaluated for light microscopic (LM) examination using hematoxylin-eosin and Luxol fast blue staining. For electron microscopic examination, the specimens were obtained at the cortex. The histologic and MR findings were compared. RESULTS: The embolization lesions showed hyperintensity on T2-weighted images, hyperintensity, or isointensity on DWIs, hypointensity, or isointensity on ADC maps and contrast enhancement on Gd-T1WIs at 2 hours. The T2-weighted hyperintensity extended to the white matter at day 1 and decreased thereafter. Contrast enhancement decreased continuously from day 1, and hyperintensity on DWI decreased after day 4. Hypointensity on ADC maps became less prominent after day 4. By week 3, most lesions had reverted to a normal appearance on MR images and were correlated with LM findings. However, small focal lesions remained in the gray matter of 8 cats and in the white matter of 3 cats on MR images, and this correlated with the cystic changes on LM findings. Electron microscopic examination of the cortical lesions that reverted to normal at week 3 in MR images showed that most of these lesions appeared normal but showed sporadic intracapillary fat vacuoles and disruption of the endothelial walls. CONCLUSIONS: The embolized lesions of the hyperacute stage were of 2 types: type 1 lesions, showing hyperintensity on DWIs and hypointensity on ADC maps, have irreversible sequelae, such as cystic changes; whereas type 2 lesions, showing isointensity or mild hyperintensity on DWIs and ADC maps, reverted to a normal appearance in the subacute stage.