超顺磁性葡聚糖氧化铁纳米颗粒中葡聚糖含量测定方法研究

目的新型磁共振造影剂的研究是目前国内外的一个热点,本研究建立了超顺磁氧化铁中葡聚糖含量测定方法。方法用共沉淀法制备氧化铁纳米粒子,通过强酸性阳离子交换树脂纯化,提取,葡聚糖在苯酚-硫酸作用下脱水并显色,于488nm波长处测定吸收度。结果葡聚糖在9.8~98.0μg/mL范围内呈良好的线性关系(r=0.9991)。平均回收率分别为97.3%,104.3%,102.6%。结论本法简便、快速、重现性好,可用于超顺磁氧化铁中葡聚糖的检测。     

Magnetic resonance imaging of atherosclerotic plaques using superparamagnetic iron oxide particles

Experimental data show accumulation of superparamagnetic iron oxide (SPIO) particles in atherosclerotic plaques. SPIO uptake occurred in plaques, suggesting an increased endothelial permeability and macrophage infiltrates as signs of inflammatory plaque activity. We incidentally observed SPIO uptake in aortic and arterial wall segments in patients who had originally received the magnetic resonance (MR) contrast agent for staging lymph node metastases. Twenty patients (19 male, 1 female; mean age, 64; range, 41-78 years) with bladder or prostate cancer underwent MR imaging (MRI) using a T2*-weighted high-resolution gradient-echo sequence prior to and 24-36 hours after intravenous injection of 2.6 mg of Fe/kg of SPIO (Sinerem). The aorta, both common external and internal iliac, as well as both superficial femoral arteries, were retrospectively analyzed for atherosclerotic wall changes. One patient was excluded. A positive finding was defined as an area of pronounced signal loss on postcontrast images clearly confined to the arterial wall, which was absent in the precontrast examination or increased in size. Such a finding was observed in one to three arteries in 7 of the 19 patients. The pronounced signal loss in the wall of the aorta and pelvic arteries seen in part of an elderly patient population after intravenous SPIO administration strongly suggests that this contrast agent accumulates in human atherosclerotic plaques.     

Susceptibility gradient mapping (SGM): A new postprocessing method for positive contrast generation applied to superparamagnetic iron oxide particle (SPIO)‐labeled cells

Local susceptibility gradients result in a dephasing of the precessing magnetic moments and thus in a fast decay of the NMR signals. In particular, cells labeled with superparamagnetic iron oxide particles (SPIOs) induce hypointensities, making the in vivo detection of labeled cells from such a negative image contrast difficult. In this work, a new method is proposed to selectively turn this negative contrast into a positive contrast. The proposed method calculates the susceptibility gradient and visualizes it in a parametric map directly from a regular gradient‐echo image dataset. The susceptibility gradient map is determined in a postprocessing step, requiring no dedicated pulse sequences or adaptation of the sequence before and during image acquisition. Phantom experiments demonstrated that local susceptibility differences can be quantified. In vivo experiments showed the feasibility of the method for tracking of SPIO‐labeled cells. The method bears the potential also for usage in other applications, including the detection of contrast agents and interventional devices as well as metal implants. Magn Reson Med 60:595–603, 2008. © 2007 Wiley‐Liss, Inc.     

锰增强磁共振在大脑功能活动评价中的初步探索

目的：探讨用锰增强磁共振功能成像（ME-MRI）检测大脑功能活动的可能性，为示踪移植神经干细胞（NSCs）在创伤性脑损伤大鼠脑内的功能作铺垫。方法：A组正常SD大鼠静脉缓慢输注四水合氯化锰（MnCl2·4H2O），用甘露醇开放其一侧血脑屏障，然后电刺激其对侧肢体，即刻行T1加权MRI扫描；同时比较C组未开放血脑屏障、D组未行肢体电刺激和应用钙通道阻断剂的ME-MRI图像。结果：仅静脉输注MnCl2·4H2O、开放血脑屏障和行电刺激的T1加权MRI上体感皮质区表现出高信号。结论：ME-MRI可在体评估大脑功能活动，并为移植NSCs在创伤性脑损伤大鼠脑内的功能评价提供依据。     

Effect of superparamagnetic iron oxide on tumor‐to‐liver contrast at T2*‐weighted gradient‐echo MRI: Comparison between 3.0T and 1.5T MR systems

Purpose

To compare 3.0T and 1.5T MR systems in terms of the effect of superparamagnetic iron oxide (SPIO) on tumor‐to‐liver contrast in T2*‐weighted gradient‐echo MRI.

Materials and Methods

SPIO‐enhanced gradient‐echo MR images of the liver with four different TEs (3, 5.3, 6.5, and 8.5 msec) were obtained by means of 1.5T and 3.0T systems. Quantitative analyses of relative signal intensities (SIs) and relative tumor contrast and qualitative analyses of image quality and lesion conspicuity of the liver were performed in 22 patients, 16 of whom had malignant liver tumors.

Results

With both 1.5T and 3.0T, at TE = 8.4 msec, the relative SI of liver and relative tumor contrast were significantly (P < 0.01) lower and higher, respectively, than that for any of the other TEs. There were no significant differences in the relative SI of the liver, relative tumor contrast, image quality, and tumor conspicuity for the same TE between the 1.5T and 3.0T systems.

Conclusion

Our results showed that the effect of SPIO on tumor‐to‐liver contrast at T2*‐weighted gradient‐echo imaging was similar for the 1.5T and 3.0T systems, and that the 8.4‐msec TE was optimal of the four TEs used in this study at 3.0T. J. Magn. Reson. Imaging 2009;29:595–600. © 2009 Wiley‐Liss, Inc.     

Evaluation of the changes in signals from the spleen using ferucarbotran

Purpose Because superparamagnetic iron oxide is actively taken into the reticuloendothelial system, the signal intensity observed on T2-weighted images is reduced not only in the liver but also in the spleen. There is no difference in the reduction in signal intensity in the liver after contrast between the ferumoxides and ferucarbotran, but the reduction in signal intensity in the spleen is considerable. In the present study, we examined the efficacy of T2*-weighted imaging to compensate for the reduction in signal intensity in the spleen by administering ferucarbotran. Materials and methods We examined the images obtained from 35 patients who underwent MRI with ferucarbotran. T2-weighted images and T2*-weighted images were obtained before and after administration of ferucarbotran, and the changes in signal intensity in the liver and spleen were then analyzed. Results A reduction in signal intensity was observed in the liver by both T2- and T2*-weighted imaging. In the spleen, the signal intensity was reduced on T2-weighted images but was not reduced on T2*-weighted images. Conclusion The reduction in signal intensity due to administration of ferucarbotran is low in the spleen. Thus, it was considered necessary to approach the problem of diagnosing ectopic splenic tissue using ferucarbotran with caution.     

Superparamagnetic iron oxide (SPIO)-enhanced liver MRI with ferucarbotran: efficacy for characterization of focal liver lesions

PURPOSE: To evaluate the efficacy of ferucarbotran in T2-weighted (T2W) fast spin-echo (FSE) and T2*W gradient-echo (GRE) sequences for characterizing focal liver lesions. MATERIALS AND METHODS: In 68 patients, 46 malignant and 22 benign focal liver lesions were evaluated. Precontrast (NCE) T2W FSE images and contrast-enhanced (CE) T2W FSE and T2*W GRE images were obtained on a 1.5T MR system. Based on signal intensity (SI) measurements in focal lesions and liver parenchyma, the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for all sequences. The percentage of SI loss (PSIL) in focal lesions after contrast agent (CA) application was calculated for the T2W FSE sequence. Qualitative analyses were performed to assess image quality and lesion conspicuity obtained with the CE-T2W FSE and CE-T2*W GRE sequences. RESULTS: The mean PSIL was higher in solid benign lesions than in malignant lesions (39.6% vs. 3.2%, P<0.05). With a threshold PSIL of 25%, the sensitivity and specificity for characterizing malignant lesions were 97.8% and 92.9%, respectively. The mean CNR of the malignant lesions was higher in the CE-T2*W sequence than in the CE- and NCE-T2W FSE sequences (29.9 vs. 22.7 (P<0.01) vs. 12.8 (P<0.01)). CE-T2*W images showed a superior image quality and lesion conspicuity (P<0.05) compared to the CE-T2W FSE sequence. CONCLUSION: The PSIL can be an accurate tool for characterizing benign and malignant lesions. The addition of a CE-T2*W GRE sequence is helpful for the detection and characterization of malignant lesions.     

肝纤维化的SPIO增强磁共振成像研究

目的旨在通过动物肝纤维化模型的超顺磁性氧化铁（SPIO）增强磁共振（MR）研究,分析不同程度肝纤维化对SPIO增强效应的影响。方法肝纤维化大鼠21只及正常大鼠8只于注射SPIO前及60min后行T2加权MR扫描。测量图像的信号强度（SI）,计算信噪比（SNR）和信号强度变化百分比。肝脏标本行组织学检查,根据Scheuer的肝纤维化分期标准将大鼠分为4组。结果正常及肝纤维化组的SI及SNR于增强前后差异有显著性（P〈0.01）。肝纤维化分期与信号强度变化百分比的Spearman相关分析显示无相关性存在（P=0.212,r=0.239）。结论SPIO在肝纤维化与正常肝脏具有同样有效的增强作用。SPIO对肝脏增强效果的降低与慢性肝脏疾病的损害程度无显著相关。     

Neural progenitor cells transplanted into the uninjured brain undergo targeted migration after stroke onset

Endogenous neural stem cells normally reside in their niche, the subventricular zone, in the uninjured rodent brain. Upon stroke, these cells become more proliferative and migrate away from the subventricular zone into the surrounding parenchyma. It is not known whether this stroke-induced behavior is due to changes in the niche or introduction of attractive cues in the infarct zone, or both. A related question is how transplanted neural stem cells respond to subsequent insults, including whether exogenous stem cells have the plasticity to respond to subsequent injuries after engraftment. We addressed this issue by transplanting neural progenitor cells (NPCs) into the uninjured brain and then subjecting the animal to stroke. We were able to follow the transplanted NPCs in vivo by labeling them with superparamagnetic iron oxide particles and imaging them via high-resolution magnetic resonance imaging (MRI) during engraftment and subsequent to stroke. We find that transplanted NPCs that are latent can be activated in response to stroke and exhibit directional migration into the parenchyma, similar to endogenous neural NPCs, without a niche environment.     

Macrophage labeling by SPIO as an early marker of allograft chronic rejection in a rat model of kidney transplantation.

Anatomical and functional information (renography, perfusion) was obtained by MRI in a life-supporting transplantation model, in which Lewis rats received kidneys from Fisher 344 donors. Renography and perfusion analyses were carried out with Gd-DOTA and small particles of iron oxide (SPIO), respectively. Starting 12 weeks posttransplantation, images from grafts of untreated recipients exhibited distinctive signal attenuation in the cortex. Animals treated with cyclosporin (Sandimmune Neoral; Novartis Pharma, Basel, Switzerland) to prevent acute rejection showed a signal attenuation in the cortex at 33 weeks posttransplantation, while kidneys from rats treated additionally with everolimus (Certican; Novartis), a rapamycin derivative, had no changes in anatomical appearance. A significant negative correlation was found between the MRI cortical signal intensity and the histologically determined iron content in macrophages located in the cortex. Renography revealed a significantly reduced functionality of the kidneys of untreated controls 33 weeks after transplantation, while no significant changes in perfusion were observed in any group of rats. These results suggest the feasibility, by labeling macrophages with SPIO, of detecting signs of graft rejection significantly earlier than when changes in function occur. Monitoring early changes associated with chronic rejection can have an impact in preclinical studies by shortening the duration of the experimental period and by facilitating the investigation of novel immunomodulatory therapies for transplantation.