In vivo tracking of genetically engineered, anti-HER2/neu directed natural killer cells to HER2/neu positive mammary tumors with magnetic resonance imaging

The purpose of this study is to optimize labeling of the human natural killer (NK) cell line NK-92 with iron-oxide-based contrast agents and to monitor the in vivo distribution of genetically engineered NK-92 cells, which are directed against HER2/neu receptors, to HER2/neu positive mammary tumors with magnetic resonance (MR) imaging. Parental NK-92 cells and genetically modified HER2/neu specific NK-92-scFv(FRP5)-zeta cells, expressing a chimeric antigen receptor specific to the tumor-associated ErbB2 (HER2/neu) antigen, were labeled with ferumoxides and ferucarbotran using simple incubation, lipofection and electroporation techniques. Labeling efficiency was evaluated by MR imaging, Prussian blue stains and spectrometry. Subsequently, ferucarbotran-labeled NK-92-scFv(FRP5)-zeta (n=3) or parental NK-92 cells were intravenously injected into the tail vein of six mice with HER2/neu-positive NIH 3T3 mammary tumors, implanted in the mammary fat pad. The accumulation of the cells in the tumors was monitored by MR imaging before and 12 and 24 h after cell injection (p.i.). MR data were correlated with histopathology. Both the parental NK-92 and the genetically modified NK-92-scFv(FRP5)-zeta cells could be labeled with ferucarbotran and ferumoxides by lipofection and electroporation, but not by simple incubation. The intracellular cytoplasmatic iron-oxide uptake was significantly higher after labeling with ferucarbotran than ferumoxides (P<0.05). After intravenous injection of 5×10⁶ NK-92-scFv(FRP5)-zeta cells into tumor-bearing mice, MR showed a progressive signal decline in HER2/neu-positive mammary tumors at 12 and 24 h (p.i.). Conversely, injection of 5×10⁶ parental NK-92 control cells, not directed against HER2/neu receptors, did not cause significant signal intensity changes of the tumors. Histopathology confirmed an accumulation of the former, but not the latter cells in tumor tissue. The human natural killer cell line NK-92 can be efficiently labeled with clinically applicable iron-oxide contrast agents, and the accumulation of these labeled cells in murine tumors can be monitored in vivo with MR imaging. This MR cell tracking technique may be applied to monitor NK-cell based immunotherapies in patients in order to assess the presence and extent of NK-cell tumor accumulations and, thus, to determine therapy response early and non-invasively.     

脐血间充质干细胞磁探针标记和MR成像研究

目的　应用磁性氧化铁纳米粒子和多聚赖氨酸 (Poly L Lysine ,PLL)的偶联物Fe2 O3 PLL ,体外标记人脐血间充质干细胞 (mesenchymalstemcells,MSCS) ,磁共振进行标记细胞成像。方法　制备Fe2 O3 PLL ,分离人脐血MSCS 进行纯化并传代培养 ,标记Fe2 O3 PLL ,普鲁士蓝染色显示细胞内铁 ,四氮噻唑蓝 (MTT)比色试验评价不同浓度Fe2 O3 PLL标记MSCS 后对细胞生长状况的影响 ,Annexin/碘化吡啶 (PI)双染色法检测细胞凋亡 ,应用MR的T1WI、T2 WI、T2 WI3个序列进行细胞群成像。结果　普鲁士蓝染色清晰显示蓝色铁颗粒位于MSCS 胞质内 ,MTT比色试验示 5～ 2 0 0 μg/ml等7个铁浓度组 ,Fe2 O3 PLL标记后细胞的光吸收值与未标记MSCS 者比较 ,各组间总体比较差异无统计学意义(Kruskal Wallis秩和检验 ,χ2 =10 35 ,P =0 17)。标记MSCS 时 ,铁浓度采用 2 0 μg/ml较合适。标记MSCS、未标记MSCS 者晚期凋亡及坏死细胞分别为 5 4 3%、2 95 % ,早期凋亡细胞分别为 9 93%、10 14 %。在MR的T1WI、T2 WI、T2 WI中 ,标记 1× 10 6个MSCS 者、标记 5× 10 5个MSCS 者较未标记MSCS 者均有信号降低改变 ,且前者的降低率大于后者 ,3个序列中以T2 WI的信号强度变化率最大 ;标记 1× 10 6个MSCS 者 ,标记后培养 8d的信号     

神经干细胞超顺磁性氧化铁标记及体内外MRI示踪

目的使用超顺磁性氧化铁(SPIO)纳米粒子对神经干细胞进行体外标记,并在体外及活体移植后对标记细胞进行MRI示踪。方法实验动物包括13只SD大鼠。联合应用SPIO及多聚左旋赖氨酸(PLL)通过受体介导的内吞作用标记神经干细胞,对标记细胞分别进行普鲁士蓝染色、电子显微镜观察、体外MRI示踪及活体移植后体内MRI示踪。体外1.5T及4.7TMR扫描对象分为5组,分别为5×105个标记后培养1d的细胞、5×105个相同时期未标记的细胞、提取标记细胞后的含铁培养基、相应的无铁培养基及蒸馏水。扫描序列包括轴面T1WI、T2WI及T2WI,并在4.7TMR仪上测量标记细胞的弛豫率R2及R2的变化。结果(1)该方法标记神经干细胞的有效率为100%,普鲁士蓝染色证实了每个标记细胞胞质内有多少不等的蓝染铁颗粒。(2)体外1.5T及4.7TMRI显示,标记细胞同未标记细胞相比,T1WI信号强度平均上升分别为20.53%及24.06%,T2WI信号强度平均下降分别为40.78%及50.66%,T2WI信号强度平均下降46.57%及53.70%。1.5TMRI上标记细胞的信号改变在T2WI与T2WI之间差异无统计学意义(F=3.06,P>0.05),而T2WI及T2WI与T1WI之间差异均有统计学意义(F=6.5,P<0.05)。(3)4.7TMRI测量未标记细胞和标记细胞的T2分别为516ms及77ms,其弛豫率R2分别为1.94s-1及12.98s-1;T2分别为109ms及22.9ms,其弛豫率R2分别为9.17s-1及43.67s-1。(4)标记细胞活体移植1周后行1.5TMR检查,见移植部位在T2WI及T2WI上呈显著低信号,而对照侧未见低信号。结论该方法标记神经干细胞简单高效,标记细胞弛豫率R2及R2明显提高,并能采用1.5TMRI对标记细胞进行活体内外示踪研究。     

Migration of iron oxide-labeled human hematopoietic progenitor cells in a mouse model: in vivo monitoring with 1.5-T MR imaging equipment

PURPOSE: To evaluate the use of clinical 1.5-T magnetic resonance (MR) imaging equipment to depict the in vivo distribution of iron oxide-labeled human hematopoietic progenitor cells in athymic mice. MATERIALS AND METHODS: This study was approved by the ethical committee, and all women had given consent to donate umbilical cord blood for research. Twenty athymic female Balb/c mice underwent MR imaging before and 1, 4, 24, and 48 hours after intravenous injection of (1-3) x 10(7) human hematopoietic progenitor cells labeled with the superparamagnetic iron oxide particles ferumoxides through simple incubation (n = 10) or P7228 through lipofection (n = 10). Fifteen female Balb/c control mice were examined after intravenous injection of the pure contrast agents (n = 6 for both probes) or nonlabeled cells (n = 3). Signal intensities of liver, spleen, and bone marrow on MR images obtained before and after injection were measured and compared for significant differences by using the t test. MR imaging data were compared with the results of immunostaining against human CD31(+) cells and against the coating of the contrast agents; these results served as the standard of reference. RESULTS: Ferumoxides was internalized into more mature CD34(-) cells but not into CD34(+) stem cells, while P7228 liposomes were internalized into both CD34(-) and CD34(+) cells. After injection of iron oxide-labeled hematopoietic cells, a significant decrease in MR signal intensity was observed in liver and spleen at 1, 4, 24, and 48 hours after injection (P < .05) and in the bone marrow at 24 and 48 hours after injection (P < .05). The signal intensity decrease in bone marrow was significantly stronger after injection of iron oxide-labeled cells compared to controls that received injections of the pure contrast agent (P < .05). Results of histopathologic examination confirmed homing of iron oxide-labeled human progenitor cells in the murine recipient organs. CONCLUSION: The in vivo distribution of intravenously administered iron oxide-labeled hematopoietic progenitor cells can be monitored with 1.5-T MR imaging equipment.     

Contrast-enhanced MR imaging of liver and spleen: First experience in humans with a new superparamagnetic iron oxide

The aim of this prospective study was to obtain the first human safety and magnetic resonance (MR) imaging results with a new formulation of superparamagnetic iron oxide (SPIO) (SHU 555 A). The SPIO was tested at four iron doses, from 5 to 40 μmol/kg. Laboratory tests and clinical measurements were done in 32 healthy volunteers for up to 3 weeks after administration. MR imaging at 1.5 T was performed before and 8 hours to 14 days after fast intravenous injection (500 μmol Fe/min) of the SPIO (six subjects per dose). Results of this phase I study demonstrate that SHU 555 A at a concentration of 0.5 mol Fe/L was well tolerated. A dose-dependent minor increase in activated partial thromboplastin time, which remained within the normal range, was seen. All doses of SPIO caused a signal loss in both liver and spleen (P <.05) with a spin-echo sequence (TR = 2,300 msec, TE = 45 msec). The signal losses in the liver 8 hours after contrast agent injection were 58%, 79%, 82%, and 87% for the 5, 10, 20, and 40 μmol Fe/kg doses, respectively. The corresponding signal losses in the spleen were 23%, 45%, 65%, and 78%, respectively. The doses that reduced signal intensity by half were 3.1 μmol Fe/kg for the liver and 12.8 μmol Fe/kg for the spleen. The results suggest that the new SPIO formulation is a safe and efficient MR contrast agent.     

Evaluation of an ultrasmall superparamagnetic iron oxide in MRI in a bone tumor model in rabbits

Ultrasmall superparamagnetic iron oxides (USPIOs) are a class of MRI contrast agents having moderately selective affinity for the reticuloendothelial cells of lymph nodes and bone marrow. This study evaluated a USPIO preparation, Combidex (Code 7227), in MRI of a rabbit bone tumor model. VX2 carcinoma implanted into the tibial marrow of nine subject rabbits was studied. After tumor growth, the subjects underwent MRI of their lesions both before and after intravenous administration of Code 7227. Code 7227 was judged subjectively to conspicuously reduce the signal intensity of normal marrow on some pulse sequences. A hypointense zone outlined the tumor margins on postcontrast imaging, which allowed improved visualization of the soft tissue component of the larger lesions. Accumulation of the contrast agent in a zone of inflammation outside the tumor margin was demonstrated on histologic sections of the lesions. Code 7227 deserves additional study as a potential contrast agent for MRI of bone tumors.     

Gadolinium-ethoxybenzyl-DTPA as a hepatobiliary contrast agent for use in MR cholangiography: results of an in vivo phase-I clinical evaluation

The purpose of this study was to investigate the time course of contrast enhancement in bile ducts and the gallbladder (GB) after injection of gadolinium-ethoxybenzyl-DTPA (Gd-EOB-DTPA). In a clinical phase-I study, MR imaging at 1.5T was performed in 16 healthy volunteers with four different doses of Gd-EOB-DTPA (10, 25, 50, and 100 μmol/kg b. w., four volunteers per dosage). The study protocol comprised a heavily T1-weighted fast multiplanar gradient-echo (GE) sequence before and at increasing intervals for up to 360 min after injection of Gd-EOB-DTPA. The signal enhancement was evaluated in extra- and intrahepatic bile ducts as well as in the GB. In all 16 volunteers the common bile duct showed intense signal enhancement beginning 5–16 min after injection (mean 10 min) and persisting for at least 120 min in 4 subjects and for 360 min in 12 subjects. The duration of signal enhancement was significantly (p < 0.05) longer for higher doses (50, 100 μmol/kg) than for lower doses (10, 25 μmol/kg). Intrahepatic bile ducts were hyperintense as compared with liver parenchyma in all subjects receiving 10 μmol/kg from approximately 50–120 min after contrast agent application. Intrahepatic bile ducts were not displayed using the higher doses, probably because of the strong enhancement of the liver parenchyma. Gallbladder contrasting was achieved in all cases beginning 7–33 min after injection (mean 19 min) and remained visible for up to 360 min in 94 %. Hyperintense visualization of normal extrahepatic bile ducts as well as the GB is regularly achieved with the hepatobiliary contrast agent Gd-EOB-DTPA. The dosage for hyperintense visualization of intrahepatic bile ducts is 10 μmol/kg. Received 6 December 1995; Revision received 21 March 1996; Accepted 25 March 1996     

新型MR对比剂长循环超顺磁氧化铁脂质体纳米微粒的体内外实验研究

目的 评价自制新型MR对比剂:长循环超顺磁性氧化铁(superparamagnetic iron oxide,SPIO)脂质体纳米微粒的药代动力学.方法 以加入SPIO为对照组,加入长循环SPIO脂质体纳米微粒为实验组.(1)巨噬细胞的体外吞噬实验:将巨噬细胞株RAW 264.7经复苏、培养,细胞达到80%～90%融合后,以每孔2.5×105个细胞接种于培养板,对照组和实验组细胞与不同浓度药物孵化后,分别测定细胞中Fe浓度和Fe染色情况,并用析因设计的方差分析对结果进行统计学处理.(2)小鼠体内药物分布实验:C57BL/6J雄性小鼠6只,每组2只,设为空白对照组、对照组、实验组,经尾静脉分别注射生理盐水、SPIO以及长循环SPIO脂质体后牺牲动物,经病理检查观察2组药物在体内的分布情况.(3)荷肺癌裸鼠MR成像实验:建立20只BALB/c裸鼠移植型肺癌模型,分为对照组和实验组,每组10只,分别经尾静脉注入SPIO和长循环SPIO脂质体纳米微粒后行MR扫描,测量增强前后2组实验动物各时间点肝脏和肿瘤ROI的信号强度,绘制信噪比(SNR)时间动态变化曲线,采用协方差分析比较2组动物肝脏及肿瘤增强12 h 后SNR差异有无统计学意义.(4)细胞毒性实验(噻唑蓝,MTT法):检查2种药物对人肝细胞株HL-7702细胞的毒性作用,用析因设计的方差分析对结果进行统计学处理.结果 (1)巨噬细胞的体外实验:析因分析结果表明,对照组细胞内Fe含量明显高于实验组,差异有统计学意义(F=296 839.9,P=0.000).普鲁士蓝染色显示对照组巨噬细胞染色较深,实验组巨噬细胞染色较浅.(2)小鼠体内药物分布实验:对照组肝、脾、肺、肾组织内蓝染颗粒多于实验组.(3)荷肺癌裸鼠MR成像实验:平扫对照组肝脏SNR为31.47±0.56,实验组为30.89±1.41;增强扫描12 h后对照组为17.00±0.96,实验组为22.29±0.73.平扫对照组肿瘤SNR为58.41±0.61,实验组为58.44±1.08;增强扫描12 h后对照组为58.50±0.63,实验组为52.47±1.18.经协方差分析表明增强12 h后对照组肝脏SNR显著低于实验组(F=167.022,P=0.000);而实验组肿瘤 SNR显著低于对照组(F=266.106,P=0.000).(4)细胞毒性实验:随着培养液中Fe浓度的增加,HL-7702细胞生存率均有下降趋势,但析因分析结果表明,实验组药物的细胞毒性较对照组低(F=2256.204,P=0.000).结论 长循环SPIO脂质体纳米微粒在体内外均有较好的抗巨噬系统吞噬功能,在体内实现了长循环,对非网状内皮系统的肿瘤也具有良好的T2负性被动靶向强化效果;同时还降低了SPIO对细胞的毒性作用.

Abstract：

Objective To evaluate pharmacodynamics of prepared long-circulating superparamagnetic iron oxide (SPIO) liposomes. Methods Control and experimental groups were established after adding SPIO or long-circulating SPIO liposomes as agents. (1)Macrophages experiment in vitro: the RAW 264.7 macrophage cell strains were recovered, cultured and seeded in the culture plate at a density of 2.5×105 cells/well until they reached 80%-90% confluence. The intracellular Fe uptake of control and experimental group cells were quantified by Ferrozine assay after incubation with different concentrations of drugs. Factorial design analysis of variance was used as statistics method. Prussian blue staining method was used to detect staining of experimental cells.(2)Drug biodistribution in mice: C57BL/6J(n=6) were classified into blank control group (n=2), control group(n=2) and experimental group(n=2).Saline, SPIO and long circulating SPIO were injected via the tail vein in the blank control group, control group and experimental group respectively. Then distribution of drugs in the body was observed by pathological examination.(3) MR imaging of tumor-bearing nude mice: 20 BALB/c nude mice bearing lung cancer models were established and classified into control group and experimental group. After administration of drugs, all animals underwent MR scanning. Signal intensities of livers and tumors were measured, SNR-time dynamic curves were drew. Covariance analysis was used to compare post-enhanced SNR at the 12th hour. (4)Cytotoxicity studies (MTT): cytotoxicity of both drugs on human liver cell line HL-7702 was studied, and statistically analyzed using factorial design analysis of variance. Results (1) Macrophages experiment in vitro: The nanoparticle uptake by macrophage cells evaluated by ferrozine assay showed the uptake of blank SPIO was higher than long-circulating SPIO liposomes. Compared with the blank control group, there was strong blue staining in the macrophages with Prussian staining in the control group and little blue staining in the experimental group. (2) Drug biodistribution in mice: for blue stained cells composed of iron particles, the amounts in the liver, spleen, lung, kidney of the control group were more than those in the experimental group. (3) MR imaging of tumor-bearing nude mice: the non-enhanced SNR of livers and tumors in the control group and experimental group were 31.47 ± 0.56, 30.89 ± 1.41, 58.41 ± 0.61, 58.44 ± 1.08, respectively. After injecting of contrast agents, SNR of livers and tumors in the control group and experimental group were 17.00 ± 0.96, 22.29 ± 0.73, 58.50 ± 0.63, 52.47 ± 1.18, respectively. The covariance analysis showed that SNR of the livers in the control group after 12 hours was significantly lower than the experimental group (F=167.022, P=0.000); while the SNR of the tumors in the experimental group was significantly lower than the control group (F=266.106, P=0.000).(4) Cytotoxicity of nanoparticles by MTT method: the viability of HL-7702 cells tend to decrease with the increase of Fe concentration. Cytotoxicity in the long-circulating SPIO liposomes was lower than the SPIO(F=2256.204,P=0.000). Conclusions Long-circulating SPIO liposomes we prepared reveal suitable sizes, even distribution, and good anti-macrophage ability in vitro and in vivo. They have long circulation characteristic and T2 negative enhancement effect in the transplanted lung cancers, while they still maintain low cytotoxicity.     

In vivo MR imaging tracking of transplanted mesenchymal stem cells in a rabbit model of acute peripheral nerve traction injury

Purpose

To investigate in vivo MRI tracking mesenchymal stem cells (MSCs) in peripheral nerve injures using a clinically available paramagnetic contrast agent (Gd‐DTPA) and commercially available rhodamine‐incorporated transfection reagents (PEI‐FluoR).

Materials and Methods

After bone marrow MSCs were labeled with Gd‐DTPA and PEI‐FluoR complex, the labeling efficacy and longevity of Gd‐DTPA maintenance were measured and cell viability, proliferation, and apoptosis were assessed. Thirty‐six rabbits with acute sciatic nerve traction injury randomly received 1 × 10⁶ labeled (n = 12) or unlabeled MSCs (n = 12) or vehicle alone injection. The distribution and migration of implanted cells was followed by MRI and correlated with histology. The relative signal intensity (RSL) of the grafts was measured.

Results

The labeling efficiency was 76 ± 4.7% and the labeling procedure did not in?uence cell viability, proliferation, and apoptosis. A persistent higher RSL in grafts was found in the labeled group compared with the unlabeled and vehicle groups until 10 days after transplantation (P < 0.05). The distribution and migration of labeled cells could be tracked by MRI until 10 days after transplantation. Transplanted MSCs were not found to transdifferentiate into Schwann‐like cells within 14‐day follow‐up.

Conclusion

Labeling MSCs with the dual agents may enable cellular MRI of the engraftment in the experimental peripheral nerve injury. J. Magn. Reson. Imaging 2010;32:1076–1085. © 2010 Wiley‐Liss, Inc.

     

Usage of the T1 effect of an iron oxide contrast agent in an animal model to quantify myocardial blood flow by MRI

BACKGROUND: To present a new method for fully quantitative analysis of myocardial blood flow (MBF) using magnetic resonance imaging. The first pass of an intravascular iron oxide contrast medium can be used to quantify myocardial perfusion. The technique was validated in an animal model using colored microspheres. MATERIALS AND METHODS: In six pigs, a tracking catheter was positioned in the left anterior descending artery (LAD). Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was performed on a 1.5-T scanner using a hybrid gradient-echo/echoplanar imaging (GRE-EPI) sequence. Regional myocardial blood flow (rMBF) was altered by either inducing vasodilatation with adenosine or creating coronary artery obstruction. The T(1) effect of a superparamagnetic iron oxide-based contrast medium (Resovist) administered at a dose of 8 micromol/kg was used. Upslope, time-to-peak and peak intensity were calculated from the signal intensity-time curves and absolute rMBF using the Kety-Schmidt equation; results were compared to those obtained using colored microspheres. RESULTS: The mean rMBF calculated by MRI was 1.49 (+/-6.91, quartile width) ml/min/g versus 3.21 (+/-1.61) ml/min/g measured by means of microspheres under resting conditions. rMBF increased to a mean of 6.21 (+/-2.83) ml/min/g versus 4.22 (+/-1.70) ml/min/g under adenosine and was reduced to zero flow in total occlusion. Linear regression showed the best correlation for upslope (R=0.714), time-to-peak (R=0.626) and the Kety-Schmidt equation (R=0.584). CONCLUSIONS: The T(1) effect of an iron oxide-based contrast medium allows determination of rMBF when using the Kety-Schmidt equation. The results are similar to those obtained with the standard of reference, colored micropheres, but not better than the results of the semiquantitative approach.     

Serial in vivo positive contrast MRI of iron oxide-labeled embryonic stem cell-derived cardiac precursor cells in a mouse model of myocardial infarction

Myocardial regeneration with stem-cell transplantation is a possible treatment option to reverse deleterious effects that occur after myocardial infarction. Since little is known about stem cell survival after transplantation, developing techniques for "tracking" cells would be desirable. Iron-oxide-labeled stem cells have been used for in vivo tracking using MRI but produce negative contrast images that are difficult to interpret. The aim of the current study was to test a positive contrast MR technique using reduced z-gradient rephasing (GRASP) to aid in dynamically tracking stem cells in an in vivo model of mouse myocardial infraction. Ferumoxides and protamine sulfate were complexed and used to magnetically label embryonic stem cell-derived cardiac-precursor-cells (ES-CPCs). A total of 500,000 ES-CPCs were injected in the border zone of infarcted mice and MR imaging was performed on a 9.4T scanner using T(2)*-GRE sequences (negative contrast) and positive contrast GRASP technique before, 24 hours, and 1 week after ES-CPC implantation. Following imaging, mice were sacrificed for histology and Perl's staining was used to confirm iron within myocardium. Good correlation was observed between signal loss seen on conventional T(2)* images, bright areas on GRASP, and the presence of iron on histology. This demonstrated the feasibility of in vivo stem cell imaging with positive contrast MRI.     

Comparison of dysprosium DTPA BMA and superparamagnetic iron oxide particles as susceptibility contrast agents for perfusion imaging of regional cerebral ischemia in the rat

The aim of the study was to compare the first-passage profiles of dysprosium diethylenetriamine penta-acetic acid bis(methylamide) (DTPA BMA) and the superparamagnetic iron oxide particles NSR 0430 in regions with severe and moderate cerebral ischemia. In seven rats subjected to middle cerebral artery occlusion, two dynamic MR perfusion imaging series were acquired after intravenous bolus injections of .5 mmol/kg dysprosium DTPA BMA and .06 mmolFe/kg iron oxide particles, respectively. The doses were chosen to obtain similar maximum signal change in normally perfused brain. The first-passage profiles were compared in a region of interest (ROI) in the core area with severe ischemia and in a ROI in the penumbra area of moderate ischemia. The results were compared both as the calculated mean signal intensity versus time curves for all seven rats and statistically for an estimated mean transit time (MTT) after gamma variate fitting of the calculated concentration versus time curves. The first-passage profiles for the two contrast agents were similar, both in the core area of severe ischemia and in the penumbra area of moderate ischemia. In this rat stroke model, dysprosium DTPA BMA and the superparamagnetic iron oxide particles NSR 0430 were found to be equally efficacious for the diagnosis of the perfusion deficit, but if safe for human investigations, iron oxide particles would have an advantage as equal susceptibility effect may be achieved with smaller injection volumes.     

Comparison of a conventional cardiac-triggered dual spin-echo and a fast STIR sequence in detection of spinal cord lesions in multiple sclerosis

The current optimal imaging protocol in spinal cord MR imaging in patients with multiple sclerosis includes a long TR conventional spin-echo (CSE) sequence, requiring long acquisition times. Using short tau inversion recovery fast spin-echo (fast STIR) sequences both acquisition time can be shortened and sensitivity in the detection of multiple sclerosis (MS) abnormalities can be increased. This study compares both sequences for the potential to detect both focal and diffuse spinal abnormalities. Spinal cords of 5 volunteers and 20 MS patients were studied at 1.0 T. Magnetic resonance imaging included cardiac-gated sagittal dual-echo CSE and a cardiac-gated fast STIR sequence. Images were scored regarding number, size, and location of focal lesions, diffuse abnormalities and presence/hindrance of artifacts by two experienced radiologists. Examinations were scored as being definitely normal, indeterminate, or definitely abnormal. Interobserver agreement regarding focal lesions was higher for CSE (ϰ = 0.67) than for fast STIR (ϰ = 0.57) but did not differ significantly. Of all focal lesions scored in consensus, 47 % were scored on both sequences, 31 % were only detected by fast STIR, and 22 % only by dual-echo CSE (n. s.). Interobserver agreement for diffuse abnormalities was lower with fast STIR (ϰ = 0.48) than dual-echo CSE (ϰ = 0.65; n. s.). After consensus, fast STIR showed in 10 patients diffuse abnormalities and dual-echo CSE in 3. After consensus, in 19 of 20 patients dual-echo CSE scans were considered as definitely abnormal compared with 17 for fast STIR. The fast STIR sequence is a useful adjunct to dual-echo CSE in detecting focal abnormalities and is helpful in detecting diffuse MS abnormalities in the spinal cord. Due to the frequent occurrence of artifacts and the lower observer concordance, fast STIR cannot be used alone. Received: 9 September 1999; Revised: 14 December 1999; Accepted: 16 December 1999     

磁性标记的小胶质细胞在大鼠脑内的MR示踪

目的 探讨超顺磁性氧化铁颗粒(SPIO)标记的小胶质细胞在正常大鼠及阿尔茨海默病(AD)大鼠体内移植后,MR活体示踪的可行性.方法 以日本血液凝集病毒包膜(HVJ-E)为标记载体,将SPIO标记的小胶质细胞经颈内动脉注入正常大鼠(5只)及AD大鼠动物模型(5只)体内,3 d后应用7.0 T MR行T2*序列扫描,并与脑组织切片组织化学染色结果对照.结果 在正常大鼠脑内,MRI可见数个点状的信号改变区,这些信号改变区散在地分布在脑内各处,脑组织切片显示铁颗粒标记细胞位置与信号改变部位一致.MRI能够检测到由数个标记细胞引起的信号强度的改变.在AD大鼠模型脑内,MRI可见β-淀粉样蛋白42(Aβ42)注射区信号强度明显下降,信号改变区面积较大.与之相比,生理盐水注射区信号改变的强度及面积均不如Aβ42注射区改变明显.Aβ42注射区的标记细胞数为(454±47)个/mm2,明显高于生理盐水注射区的标记细胞数(83±13)个/mm2(P<0.05).结论 MRI可作为一种非侵入性检测手段在活的动物体内追踪标记细胞,在AD细胞水平的治疗中具有一定临床应用前景.     

3．0TMR动脉自旋标记与动态磁敏感对比增强灌注技术在脑胶质瘤术前分级中的对照研究

目的：对照研究动脉自旋标记（arterial spin labeling,ASL）与动态磁敏感对比增强（dynamic susceptibility contrast—enhanced．DSC）灌注成像技术在脑胶质瘤中的灌注特点．探讨ASL在脑胶质瘤术前分级中的临床应用价值。方法：使用3．0TMR成像系统对23例脑胶质瘤患者（术后病理证实高级别胶质瘤17例,低级别胶质瘤6例）术前行常规扫描外,加扫ASL及DSC灌注检查。测量肿瘤实质部分最大肿瘤血流量（maximal tumor blood flow,TBFmax）以及对侧白质、对侧灰质、对侧半球的血流量（cerebral blood flow,CBF）。结果：23例脑胶质瘤患者。两种灌注方法均获得了一致的灌注结果,TBF max／对侧白质CBF、TBFmax／对侧灰质CBF及TBFmax／对侧半球CBF的各比值在ASL和DSC两种技术之间的差异无明显统计学意义（P〉0．05）,但在高、低级别胶质瘤之间的差异均有统计学意义（P〈0．05）。在ASL法中,TBFmax／对侧白质CBF、TBFmax／对侧灰质CBF及TBFmax／对侧半球CBF分别取阈值为3．06、0．46和1．31时,其敏感性分别为i00％、88．2％和100％．特异性分别为83．3％、83．3％和100％。结论：ASL在评估脑胶质瘤血流灌注方面与DSC之间有相似的敏感性,具有可重复性高、完全无创性等优点,同时有助于术前对脑胶质瘤进行分级评判。     

超顺磁性氧化铁MR成像评估大鼠非酒精性脂肪肝炎枯否细胞功能的初步研究

目的 初步探讨超顺磁性氧化铁(SPIO)作为MRI对比剂评估大鼠非酒精性脂肪肝炎(NASH)枯否细胞(KC)功能的可行性.方法 20只雄性SD大鼠按完全随机法分为实验组和对照组,每组10只,实验组喂养高脂饲料,对照组喂养普通饲料.8周后对所有大鼠行肝脏MRI及SPIO增强扫描,计算肝脏组织平均信号强度下降百分比(PSIL)和SPIO增强前后肝脾对比信号强度比值(RSIR),测定血清总胆固醇(TC)和甘油三酯(TG)值,并取肝脏标本行HE和普鲁士蓝染色分析病理表现.采用两组独立样本均数t检验比较2组不同序列SPIO增强后PSIL和RSIR值的差异.结果 实验组1只大鼠因麻醉过深死亡,其余9只血清TC及TG值分别为(6.58±1.25)和(1.53±0.23)mmoL/L,较对照组[分别为(1.64±0.22)和(0.55±0.14)mmol/L]均明显升高(t值分别为11.716和11.588,P值均＜0.01).SPIO增强扫描后两组肝实质信号强度在各序列明显下降,在PDWI及T_1WI上实验组PSIL分别为(34.78±4.51)%和(60.38±3.49)%,较实验组[分别为(64.96±2.42)%和(81.08±1.66)%]小,差异有统计学意义(t值分别为-18.451和-16.240,P值均＜0.01).PDWI、T_2WI、T_2~*WI和T_1WI序列实验组RSIR分别为1.002±0.141、5.000±0.516、20.004±1.490和2.601±0.077,均较对照组(0.400±0.102、1.500±0.115、0.503±0.105和-0.300±0.058)大(t值分别为10.745、19.800、39.168和92.785,P值均＜0.01).实验组肝脏组织中普鲁士蓝染色阳性颗粒积分(2.33±0.50)分较对照组(4分)明显减少(t=-10.000,P＜0.01).结论 高脂饮食诱导的SD大鼠NASH模型接近人类发病情况且容易建立,临床应用型1.5 T MR通过SPIO增强肝脏扫描可评估KC的功能,提示NASH的发病机制与KC功能的下降有关.     

纳米氧化铈对X射线照射小鼠外周血免疫细胞分布及脾脏T淋巴细胞增殖能力的影响

目的 观察纳米氧化铈对X射线引起的小鼠免疫损伤是否具有保护作用。方法 小鼠按体重分层分为7组：对照组、模型组、模型+不同剂量纳米氧化铈组（模型+10 ng组、模型+100 ng组、模型+1 μg组、模型+10 μg组、模型+100 μg组）,每组各6只。模型组和纳米氧化铈组小鼠经X射线1次性全身照射,照射剂量4 Gy,纳米氧化铈组小鼠于照射前4 d开始,分别腹腔注射10、100 ng/kg,1、10和100 μg/kg体重的纳米氧化铈,每周2次,照射后第10天处死小鼠。采用全自动血细胞计数仪进行外周血白细胞计数及分类;采用流式细胞术检测T、B、NK、CD4+、CD8+ T淋巴细胞的百分比,计算CD4/CD8比值;采用四甲基偶氮唑盐（MTT）法检测脾脏T淋巴细胞增殖能力。结果 与对照组相比,经X射线照射小鼠外周血的白细胞总数和NK细胞绝对值,中性粒细胞、单核细胞、总淋巴细胞、T淋巴细胞、CD4+和CD8+ T淋巴细胞的绝对值及百分比,脾脏T淋巴细胞增殖能力均降低（t=2.26~3.18,P<0.05）;B淋巴细胞百分比和CD4/CD8比值升高（t=2.45、3.18,P<0.05）。X射线照射小鼠腹腔注射不同剂量的纳米氧化铈对上述免疫学指标有改善作用,其中以10和100 μg纳米氧化铈组改善效果明显,而10 μg组改善作用最佳。结论 纳米氧化铈能够提高X射线照射小鼠的免疫功能。