Axon tracing in the adult rat optic nerve and tract after intravitreal injection of MnDPDP using a semiautomatic segmentation technique

PURPOSE: To develop and validate an objective technique for 3D segmentation of manganese-enhanced MR images of the optic nerve/tract (ON) in adult rats to improve contrast-to-noise (CNR) calculations and use the technique to ascertain if manganese dipyridoxyl diphosphate (MnDPDP) gives sufficient Mn(2+) enhancement compared to MnCl(2) when used for functional imaging of the visual pathway. MATERIALS AND METHODS: Intravitreous injection of the manganese-releasing MR contrast agent MnDPDP (30 nmol Mn(2+)) was performed to trace the ON in adult rats (n = 4). A positive control group of rats (n = 5) received a standard preparation of MnCl(2) (200 nmol Mn(2+)), while gadodiamide (1500 nmol Gd(3+)) was administered in negative control rats (n = 2). An objective technique for 3D segmentation of the enhanced ON was developed. CNR profiles along the ON were calculated by resampling the 3D image-volume in 2D planes perpendicular to the Mn(2+) enhanced ON in 0.2 mm steps, 4 mm along the segmented ON measured from the lamina cribrosa. RESULTS: The ON was successfully segmented and CNR calculated accurately within 2 minutes in a representative 3D MR image volume. Intravitreal MnDPDP injection resulted in significant MRI contrast enhancement of the retina and ON after 12-24 hours similar to that of MnCl(2) injection. CONCLUSION: 3D semiautomated image segmentation and the use of MnDPDP can improve in vivo axon tracing based on MRI. Mn(2+) was found to be released from MnDPDP after intravitreal injection in sufficient amounts to obtain functional tracing of the adult rat primary visual pathway.     

Manganese-enhanced MRI of the optic visual pathway and optic nerve injury in adult rats

PURPOSE: To evaluate manganese (Mn2+)-enhanced MRI in a longitudinal study of normal and injured rat visual projections. MATERIALS AND METHODS: MRI was performed 24 hours after unilateral intravitreal injection of MnCl2 (150 nmol) into adult Fischer rats that were divided into four groups: 1) controls (N = 5), 2) dose-response (N = 10, 0.2-200 nmol), 3) time-response with repeated MRI during 24-168 hours post injection (N = 4), and 4) optic nerve crush (ONC) immediately preceding the MnCl2 injection (N = 7). Control and ONC animals were reinjected with MnCl2 20 days after the first injection, and MRI was performed 24 hours later. RESULTS: In the control group, the optic projection was visualized from the retina to the superior colliculus, with indications of transsynaptic transport to the cortex. There was a semilogarithmic relationship between the Mn2+ dose and Mn2+ enhancement from 4 to 200 nmol, and the enhancement decayed gradually to 0 by 168 hours. No Mn2+-enhanced signal was detected distal to the ON crush site. In the control group, similar enhancement was obtained after the first and second MnCl2 injections, while in the ONC group the enhancement proximal to the crush site was reduced 20 days post lesion (20 dpl). CONCLUSION: Mn2+-enhanced MRI is a viable method for temporospatial visualization of normal and injured ON in the adult rat. The observed reduction in the Mn2+ signal proximal to the ONC is probably a result of retrograde damage to the retinal ganglion cells, and not of Mn2+ toxicity.     

Improved neuronal tract tracing using manganese enhanced magnetic resonance imaging with fast T(1) mapping.

There has been growing interest in using manganese-enhanced MRI (MEMRI) to detect neuronal activation, neural architecture, and neuronal connections. Usually Mn(2+) produces a very wide range of T(1) change. In particular, in neuronal tract tracing experiments the site of Mn(2+) injection can have very short T(1) while distant regions have small T(1) reductions, primarily due to dilution of Mn(2+). Most MEMRI studies use T(1)-weighted sequences, which can only give optimal contrast for a narrow range of T(1) changes. To improve sensitivity to the full extent of Mn(2+) concentrations and to optimize detection of low concentrations of Mn(2+), a fast T(1) mapping sequence based on the Look and Locker technique was implemented. Phantom studies demonstrated less than 6.5% error in T(1) compared to more conventional T(1) measurements. Using center-out segmented EPI, whole-brain 3D T(1) maps with 200-microm isotropic resolution were obtained in 2 h from rat brain. Mn(2+) transport from the rat olfactory bulb through appropriate brain structures could be detected to the amygdala in individual animals. The method reliably detected less than 7% reductions in T(1). With this quantitative imaging it should be possible to study more extensive pathways using MEMRI and decrease the dose of Mn(2+) used.     

锰离子增强 MRI 在大鼠视觉中枢核团立体定位中的运用

目的：探索锰离子增强磁共振成像(MEMRI)在大鼠视觉中枢核团立体定位中的价值。方法 SD 大鼠36只,分成3组。A 组(1 6只)使用 MEMRI 定位法;B 组(1 6只)使用传统解剖图谱定位;C 组(4只)使用 A 组所取得的数据定位并穿刺中枢核团。A 组定位方法为提前在单侧眼球内注射氯化锰(MnCL2)水溶液(30 mmol/L×3μL),24 h 后行 MRI 确定对侧上丘、外侧膝状体位置;B 组为根据图谱确定上述核团位置。随后,A、B 2组均经颅骨穿刺视觉核团后,注入3%荧光金溶液1μL,5 d 后处死大鼠并取出视网膜铺片,在荧光显微镜下观察视网膜神经节细胞(RGCs)标记情况。C 组则根据 A 组中取得的定位数据确定核团位置,穿刺并注射 MnCL2溶液(30 mmol/L×0.5μL)1 h 后,使用 MRI 观察强化区域,直接验证 MEMRI 定位数据的可靠性。结果 A 组RGCs 标记成功15只(93.8%),B 组 RGCs 标记成功10只(62.5%)。A 组的成功率高于 B 组(P =0.041,<0.05)。C 组 4只均准确命中核团。结论 MEMRI 在大鼠的视觉中枢核团立体定位中可提高定位准确性。     

In vivo trans-synaptic tract tracing from the murine striatum and amygdala utilizing manganese enhanced MRI (MEMRI).

Small focal injections of manganese ion (Mn(2+)) deep within the mouse central nervous system combined with in vivo high-resolution MRI delineate neuronal tracts originating from the site of injection. Previous work has shown that Mn(2+) can be taken up through voltage-gated Ca(2+) channels, transported along axons, and across synapses. Moreover, Mn(2+) is a paramagnetic MRI contrast agent, causing positive contrast enhancement in tissues where it has accumulated. These combined properties allow for its use as an effective MRI detectable neuronal tract tracer. Injections of low concentrations of MnCl(2) into either the striatum or amygdala produced significant contrast enhancement along the known neuronal circuitry. The observed enhancement pattern is different at each injection site and enhancement of the homotopic areas was observed in both cases. Ten days postinjection, the Mn(2+) had washed out, as evidenced by the absence of positive contrast enhancement within the brain. This methodology allows imaging of neuronal tracts long after the injection of the ion because Mn(2+) concentrates in active neurons and resides for extended periods of time. With appropriate controls, differentiation of subsets of neuronal pathways associated with behavioral and pharmacological paradigms should be feasible.     

视神经炎的MRI表现及与视觉诱发电位的相关性研究

目的 探讨诊断视神经炎的有效MR检查序列、MRI表现及其与视觉诱发电位(VEP)的相关性.方法 对98例(154只眼)诊断为视神经炎、视神经乳头炎、多发性硬化、视神经脊髓炎的视力下降患者MRI资料进行分析,并与VEP结果及临床视力表现做x2检验、秩和检验和一致性分析.结果154只患眼中56条视神经增粗,76条形态不变,22条变细.MR短时间反转恢复(STIR)序列显示132条视神经呈异常高信号.异常信号累及范围包括视神经球壁段7条,眶内段135条,管内段109条,颅内段97条,视交叉受累56例,视束受累23条.54例行钆喷替酸葡甲胺(Gd-DTPA)增强枪查者,87只患眼中74条视神经强化.98例患者共196只眼中,视力下降同时视神经MRI信号异常者132只眼,视力正常、视神经MRI信号正常者26眼,MRI与视力表现之间的一致率为80.61%(Kappa=0.453,P＜0.01).住获得VEP结果的175只眼中,视力下降同时VEP异常者129只眼,视力正常、VEP正常者30只眼,VEP与视力表现之间的一致率为90.86%(Kappa=0.731,P＜0.01);视神经MRI信号异常及VEP异常者117只眼,MRI信号正常、VEP正常者24只眼,MRI表现与VEP之间的一致率为80.57%(Kappa=0.460,P＜0.01).结论MR STIR序列和Gd-DTPA增强扫描联合脂肪抑制技术有助于视神经炎定位和定性诊断,VEP有助于视神经炎的诊断和亚临床病灶发现,MRI结合VEP能提高视神经炎诊断的准确率.     

Axonal tracing of the normal and regenerating visual pathway of mouse,rat, frog,and fish using manganese‐enhanced MRI (MEMRI)

Purpose:

To assess optic nerve (ON) regeneration after injury by applying manganese‐enhanced MRI (MEMRI) in a study of comparative physiology between nonregenerating rat and mouse species and regenerating frog and fish species.

Materials and Methods:

The normal visual projections of rats, mice, frogs, and fish was visualized by intravitreal MnCl₂ injection followed by MRI. Rats and mice with ON crush (ONC) were divided into nonregenerating (ONC only), and regenerating animals with peripheral nerve graft (ONC+PNG; rats) or lens injury (ONC+LI; mice) and monitored by MEMRI at 1 and 20 days post‐lesion (dpl). Frog and fish with ON transection (ONT) were monitored by MEMRI up to 6 months postlesion (mpl).

Results:

Signal intensity profiles of the Mn²⁺‐enhanced ON were consistent with ON regeneration in the ONC+PNG and ONC+LI rat and mice groups, respectively, compared with the nonregenerating ONC groups. Furthermore, signal intensity profiles of the Mn²⁺‐enhanced ON obtained between 1 mpl and 6 mpl in the fish and frog groups, respectively, were consistent with spontaneous, complete ON regeneration.

Conclusion:

Taken together, these results demonstrate that MEMRI is a viable method for serial, in vivo monitoring of normal, induced, and spontaneously regenerating optic nerve axons in different species. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

In vivo 3D MRI staining of mouse brain after subcutaneous application of MnCl2.

Follow-up T(1)-weighted 3D gradient-echo MRI (2.35 T) of murine brain in vivo (N = 5) at 120 microm isotropic resolution revealed spatially distinct signal increases 6-48 hr after subcutaneous application of MnCl(2) (20 mg/kg). The effects result from a shortening of the water proton T(1) relaxation time due to the presence of unchelated paramagnetic Mn(2+) ions, which access the brain by systemic circulation and crossing of the blood-brain barrier (BBB). A pronounced Mn(2+)-induced signal enhancement was first seen in structures without a BBB, such as the choroid plexus, pituitary gland, and pineal gland. Within 24 hr after administration, Mn(2+) contrast highlighted the olfactory bulb, inferior colliculi, cerebellum, and the CA3 subfield of the hippocampus. The affinity of Mn(2+) to various brain systems suggests the neuronal uptake of Mn(2+) ions from the extracellular space and subsequent axonal transport. Thus, at least part of the Mn(2+) contrast reflects a functional brain response of behaving animals, for example, in the olfactory system. In vivo MRI staining of the brain by systemic administration of MnCl(2) may contribute to phenotyping mutant mice with morphologic and functional alterations of the central nervous system.     

Paramagnetic metalloporphyrins: infarct avid contrast agents for diagnosis of acute myocardial infarction by MRI

In previous experiments in tumors we demonstrated that metalloporphyrins are particularly avid for nonviable tumor components. This study was performed to find out wether these agents can be used as MRI contrast agents for the visualization of acute myocardial infarction (MI). A total of 44 rats, 6 normal controls and 38 with occlusive MI (2–24 h old), were used. Gadolinium mesopophyrin (Gd-MP) or manganese totraphenylporphyrin (Mn-TPP) was intravenously injected at doses of 0.1, 0.05, and 0.01 mmol.kg. Three to 24 h after injection, axial and coronal T1-weighted (TR/TE 300/15 ms) spinecho MR images were obtained before and after killing the animals and correlated with triphenyl tetrazolium chloride (TTC) histocemical preparations. The Gd-MP content in infarcted and noninfarcted myocardium was measured using inductively coled plasma atomic emission spectroscopy (ICP-AES) MRI without contrast media could not discern the MI. However, 3–24 h after injection of either Gd-MP or Mn-TPP, the infarcted area was positively stained on MR images. This area matched well witht he negatively TTC-stained area on the heart slices (r = 0.97). The contrast ratios between the infarcted nectrotic myocardium and the noninfarcted regions varied from 150 to 300% depending on the tye of agensts and doses used. Neither false-positive nor false-negative findings were encountered. The metallaporphyrin concentration was more than 10 times higher in the infarcted than in the noninfarcted heart. Metalloporphyrins appear to be promising MRI contrast agents for detection and quantification of necrosis in MI. These preclinical results may open new perspectives in cardiac imaging.     

肿瘤相关巨噬细胞MR成像可行性的实验研究

目的 探讨肿瘤相关巨噬细胞(TAMs)MR成像的可行性.方法 BALB/c小鼠和BALB/c(nu/nu)裸鼠按数字表法随机分组,每组3只,小鼠分为6个组(分别为注射前组,注射后6、24、48、72 h、7 d组)和裸鼠5个组(分别为注射前,注射后6、24、48、72 h).用含20μg Fe/ml人血清白蛋白和多巴胺包裹的铁氧颗粒(HAS-IONPs)标记巨噬细胞系(RAW 264.7)24 h,收集细胞,经尾静脉注射5×106RAW 264.7至皮下4T1荷瘤小鼠和22B移植瘤裸鼠,分别在上述不同时间点应用7.0 T MR扫描仪行横断面、冠状面T2WI,动物处死后行病理检查.细胞毒性试验应用SPSS 11.5软件行单因素方差分析;MPd信号强度采用ImageJ 1.42软件测量.结果 普鲁士蓝染色及电镜证实细胞标记有效,单个细胞吸入的铁量为6.19 Pg.HAS-IONPs孵育细胞24 h后,不同浓度HAS-IONPs (5、10、20、40、80、160μg/ml)每组细胞平均吸光度A值分别为1.95 ±0.19、1.82±0.29、2.10±0.14、1.96±0.18、2.05±0.27、2.17±0.22,与对照组(2.00±0.07)相比,细胞吸光度A值差异无统计学意义(F=1.24,P>0.05).标记HAS-IONPs细胞数与MR R2值呈线性正相关,r=0.99,P<0.05.4T1肿瘤:注射后6 h T2WI坏死囊变周围呈明显低信号,信号强度下降率为59.4%,肿瘤实质区信号未见明显改变,下降率为4.8%.注射后24 h坏死与肿瘤实质交界部位见不规则环形低信号影,下降率为46.8%,肿瘤坏死囊变周围T:WI信号恢复,恢复96.8%.22B肿瘤:注射后6 h MRI见多发散在灶性低信号影,下降率为64.3%,24 h见点片状低信号影缩小.2种肿瘤注射后48、72 h或7 d MRT2WI形态、位置和注射后24 h相似,但信号强度递减.病理与影像结果一致.结论 TAMs MR成像可行.注射后24 h T2WI是显示肿瘤巨噬细胞迁移、浸润及定位肿瘤内的最佳时机,注射后6 h可能反映病变局部血流灌注及新生血管的状态,不同肿瘤巨噬细胞分布不同.     

CB-HRP-高效敏感的神经束路追踪方法

目的：寻找一种高效敏感析神经通路追踪方法。方法：采用结合了霍乱霍素亚单位B的辣根过氧化物酶（CB－HRP）作为示踪剂，用钨酸钠作为四氨基联苯（TMB）显色剂的稳定剂，顺行追踪视神经纤维向下丘脑前区的投射；逆行追踪舌下神经纤维在延髓背侧的分布。结果：发现视神经纤维投身到视交叉上级内侧；舌下神经纤维在延髓背侧的舌下神经纤维核分布区显示神经元胞体和轴突结构清晰。结论：用霍乱霉素亚单位B与辣根过氧化物酶结合作为示踪剂，以钨酸钠作为四氨基联苯胺显色剂的稳定剂方法是一种高效敏感的神经束踪追踪方法。     

视神经胶质瘤的CT与MRI表现

目的 分析视神经胶质瘤CT和MBI表现，并探讨其在诊断和鉴别诊断中的价值。资料与方法回顾性分析经手术及病理证实的视神经胶质瘤16例，其中CT检查15例，MRI检查6例，CT MRI检查4例。结果16例中肿瘤位于眶内段13例，眶内段累及视神经管内2例，其中1例涉及颅内，另1例位于视神经管内。肿瘤表现为眼球后肌锥内肿块占位，梭形8例，条索状与椭圆形各3例，梨形及结节状各1例。CT检查15例，2例平扫与脑实质呈等密度，14例密度均匀，边界清晰，与视神经无法区分，增强后(13例)肿瘤大多呈轻至中等强化，1例CT扫描示视神经管扩大。MRI检查6例，3例肿瘤位于眶内段，2例涉及视神经管内，其中1例蔓延至颅内显示为视交叉前视神经增粗，另1例肿瘤位于视神经管内呈结节状；肿瘤在T1WI上呈低信号，T2WI呈高信号，注射对比剂肿瘤可强化，1例肿瘤内伴有囊性变。结论 CT与MRI均能显示眶内段视神经胶质瘤，但MRI较CT能够获得更多的肿瘤内部信息，为管内及颅内视神经胶质瘤首选的影像学检查方法。     

Cavernous hemangioma of the intracranial optic pathways: CT and MRI.

PURPOSE: The purpose of this work was to describe the CT and MR findings in three patients with cavernous hemangioma (CH) of the intracranial optic pathways. METHOD: CT and MR studies of three patients with CH of the optic chiasm were reviewed. All patients underwent MRI of the chiasmal area, with coronal T2- and T1-weighted studies as well as gadolinium-enhanced coronal and sagittal T1-weighted studies. RESULTS: The patients (mean age, 40 years) presented with chiasmal apoplexy (two cases) and progressive decrease of visual acuity (one case). In all cases, MRI showed regular enlargement of the optic chiasm, with extension to the optic nerve in one case and to the left optic tract in one case. The chiasmatic dimension was 2.5-3 cm in two cases and 1-1.5 cm in the other case. In all cases, MRI revealed an acute (isointense signal on T1-weighted and hypointense signal on T2-weighted sequences) or subacute (hyperintense signal on T1 - and T2-weighted sequences) hemorrhage with, adjacent to it, an area with signals of blood of different ages, highly suggestive of CH. CT showed, in chiasmatic CHs, a suprasellar mass spontaneously denser than adjacent brain parenchyma. In two cases, microcalcifications were associated. In two cases, CT and MRI revealed slight heterogeneous enhancement after contrast agent administration. In one case, no enhancement was observed. Two patients underwent surgery by frontopterional craniotomy. The optic chiasms were swollen with an intrinsic bluish mass. The cerebrospinal fluid was not xanthochromic. Microscope examination confirmed the diagnosis of CH. After 12 months, the operated patients had improved visual acuity and visual field but did not completely recover. The nonoperated patient (because of spontaneous rapid recovery of visual acuity) was followed clinically and on MRI over 18 months. CONCLUSION: CH in the optic chiasm must be suspected in the presence of an acute chiasmatic syndrome. MRI is the best imaging modality, showing either an acute or a subacute chiasmatic hemorrhage or the typical pattern of CH with heterogeneous alternation of foci of blood of different ages, with a central focus of methemoglobin, a peripheral rim of hemosiderin, adjacent foci of acute or subacute hemorrhage, and slight or no enhancement after gadolinium administration.     

Gadofluorine M enhanced MRI in experimental glioma: superior and persistent intracellular tumor enhancement compared with conventional MRI

Purpose:

To compare conventional magnetic resonance imaging (MRI) techniques (T2‐w and Gadolinium‐DTPA‐enhanced T1‐w images) and Gadofluorine‐M (GfM), a novel contrast agent in MRI, in murine gliomas.

Materials and Methods:

Growth monitoring of murine gliomas (induced in mice) was performed on a 2.3 Tesla Bruker Biospec MRI unit. First all animals were investigated with conventional MRI techniques. In group I GfM was applied at an early stage of disease, in group II at a later stage. After injection of GfM follow‐up MRI was performed without further injection of contrast agent. On MR images tumor size and signal intensities were assessed. Animals were killed for histological evaluation.

Results:

In both groups GfM delineated tumor extents larger and more precisely than conventional MRI techniques. The difference between GfM and conventional MRI techniques reached level of significance at both tumor stages. Follow‐up MRI after singular injection of GfM showed persistence of GfM in tumor tissue. On tissue sections GfM‐enhancing areas corresponded closely to vital tumor tissue. GfM showed a mainly intracellular accumulation.

Conclusion:

Application of GfM resulted in superior delineation of experimental glioma compared with conventional MRI techniques. Thus, GfM bears a high potential in clinical application. J. Magn. Reson. Imaging 2012;35:551‐560. © 2011 Wiley Periodicals, Inc.     

肝细胞急性坏死与凋亡的磁共振扩散加权成像活体检测实验研究

 目的 评价MRI、DWI检测及鉴别肝细胞凋亡和坏死两种病理改变的价值.方法 72只S-D大鼠随机分成假手术对照组、右侧肝动脉与门静脉分支均结扎组(HA+PV组)和单独右侧门静脉分支结扎组(PV组),各24只.每组再分成4个亚组,每个亚组6只,分别于术后3 h、12 h、24 h、72 h行MRI、DWI检查,检查结束后取肝标本作HE染色、TUNEL染色,将病理结果与影像检查进行对照分析.结果 右侧门静脉与肝动脉均结扎后,肝右叶于术后3 h在T2WI上即表现为高信号,ADC值下降.单独肝右侧门静脉结扎后12 h,肝右叶ADC值出现升高,至24 h肝细胞凋亡数达最高,ADC值也达最高.结论 T2WI和DWI可早期检测发生坏死的肝组织.而组织中细胞发生凋亡后,DWI较T1WI、T2WI早期检测到凋亡组织.     

Direct CSF injection of MnCl(2) for dynamic manganese-enhanced MRI.

MnCl(2) was injected intrathecally through the cisterna magna in rats, allowing infusion of divalent manganese ions (Mn(++)) into the CSF space and thence into the brain, without breaking the blood-brain barrier (BBB). Mn(++) uptake and washout dynamics in the brain were measured by serial T(1)-weighted MRI and EPI T(1) and T(2) mapping for up to 3 weeks after injection. Observations within the first 6 hr after injection demonstrated anterograde and bilateral distribution of the Mn(++) within the CSF space, from the olfactory bulb and frontal cortex to the brain stem. Enhancement increased in most brain areas up to 4 days after injection, and then slowly decreased. Relaxation maps at each time point demonstrated higher concentrations of Mn in basal ganglia. Residual concentrations were still observable after 3 weeks in all brain regions. With the use of MnCl(2) calibration phantoms, the maximum Mn concentration in the brain was estimated to be approximately 27 +/- 16 microM, corresponding to changes in relaxation rates of 0.49 +/- 0.30 s(-1) for R(1) and 3.9 +/- 2.4 s(-1) for R(2). For comparison, an intrathecal GdDTPA injection was performed. This injection showed different distribution dynamics: it remained chiefly within the CSF spaces, and was largely washed out after 1 day. This method shows promise as a means of supplying Mn(++) uniformly to the whole brain for a variety of chronic functional activation studies.     

Manganese‐enhanced MRI of salivary glands and head and neck tumors in living subjects

Manganese‐enhanced MRI has previously been used for visualization of brain architecture and functional mapping of neural pathways. The present work investigated the potential of manganese‐enhanced MRI for noninvasive imaging of salivary glands in living subjects. Marked shortening of T₁ was observed in salivary glands of naïve mice (n = 5) 24–48 h after systemic administration of MnCl₂ (0.4 mmol/kg, intraperitoneally). Three‐dimensional MR microscopy confirmed selective contrast enhancement of salivary gland tissues post–MnCl₂ injection. Ectopic and orthotopic head and neck tumor xenografts also showed an increase in R₁ at 24 h following MnCl₂ injection (0.2 mmol/kg, intraperitoneally). However, tumor enhancement was minimal compared to salivary gland tissue. Salivary gland R₁ values were lower in mice bearing orthotopic head and neck tumors compared to naïve mice. These results demonstrate, for the first time, the usefulness of manganese‐enhanced MRI in the visualization of salivary glands and head and neck tumors in vivo. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Time course study on the effects of iodinated contrast medium on intrarenal water transport function using diffusion-weighted MRI

Purpose:

To assess the effects of intravenous‐injected iodinated contrast medium (CM) on intrarenal water diffusion using noninvasive diffusion‐weighted MRI (DW‐MRI).

Materials and Methods:

Ten New Zealand White rabbits were randomized to receive a 6 mL/kg body weight intravenous injection of clinically used iopamidol‐370 (n = 7) or an equivalent amount of 0.9% physiological saline (n = 3). A sequential DW‐MRI was performed to estimate the intrarenal apparent diffusion coefficient (ADC) at 24 h before and 1 h, 24 h, 48 h, and 72 h after administration.

Results:

Iopamidol produced a progressive ADC reduction in inner stripes of the renal outer medulla (IS) by 13.92% (P = 0.05) at 1 h, 17.52% (P = 0.02) at 24 h, 20.23% (P = 0.01) at 48 h and 16.31% (P = 0.04) at 72 h after injection. Cortical ADC was decreased by 14.14% (P = 0.01) at 48 h and 14.12% (P = 0.01) at 72 h after injection. Iopamidol produced slight decrease of ADCs in outer stripes of the outer medulla (OS) and inner medulla (IM) of kidney but without statistical difference. In control group, no significant ADC changes was observed in each anatomic compartment due to saline injection (P > 0.05).

Conclusion:

As demonstrated by DW‐MRI, intravenous iopamidol injection resulted in a successive reduction of intrarenal water diffusion, particularly in IS of kidney. This MR technique may be used as a noninvasive tool to perform a time course study of the pathogenesis associated with contrast‐induced nephropathy (CIN). J. Magn. Reson. Imaging 2012;35:1139‐1144. © 2012 Wiley Periodicals, Inc.     

In vivo MR imaging of pulmonary arteries of normal and experimental emboli in small animals

PURPOSE: To demonstrate the feasibility of pulmonary MRA in living rodents. MATERIALS AND METHODS: A three-dimensional (3D) gradient echo sequence was adapted to perform a time-of-flight (TOF) angiography of rat lung. Angiogram with a spatial resolution of 195 x 228 x 228 microm(3) was acquired in around 33 minutes. The method was then applied in animals before and after pulmonary embolism (PE) induction. Section of the proximal right pulmonary artery was measured and compared between the two populations. RESULTS: Good quality images were obtained with a contrast-to-noise ratio (CNR) of 9 +/- 3 in the proximal part of the pulmonary artery. Cross-section areas of the right main artery are statistically different before (3.45 +/- 0.69 mm(2)) and after induction of PE (4.3 +/- 0.86 mm(2)). CONCLUSION: This noninvasive tool permits angiogram acquisition at around 200 microm spatial resolution and objective distinction between healthy and embolized arteries.     

一种高效敏感的神经束路追踪方法

为寻找一种高效敏感的神经通路追踪方法。采用结合了霍乱毒素亚单位Ｂ的辣根过氧化物酶（ＣＢ ＨＲＰ）作为示踪剂，用钨酸钠作为四氨基联苯胺（ＴＭＢ）显色剂的稳定剂，顺行追踪视神经纤维向下丘脑前区的投射；逆行追踪舌下神经纤维在延髓背侧的分布。结果发现视神经纤维投射到视交叉上核背内侧；舌下神经纤维在延髓背侧的舌下神经纤维核分部区显示神经元胞体和轴突结构清晰。提示用霍乱毒素亚单位Ｂ与辣根过氧化物酶结合（ＣＢ ＨＲＰ）作为示踪剂，以钨酸钠作为四氨基联苯胺显色剂的稳定剂的方法是一种高效敏感的神经束路追踪方法。