Assessment of the link between quantitative biexponential diffusion-weighted imaging and contrast-enhanced MRI in the liver

PurposeTo investigate if intravoxel incoherent motion (IVIM) modeled diffusion-weighted imaging (DWI) can be linked to contrast-enhanced (CE-)MRI in liver parenchyma and liver lesions.MethodsTwenty-five patients underwent IVIM-DWI followed by multiphase CE-MRI using Gd-EOB-DTPA (n = 20) or Gd-DOTA (n = 5) concluded with IVIM-DWI. Diffusion (D_slow), microperfusion (D_fast), its fraction (f_fast), wash-in-rate (R_early) and late-enhancement-rate (R_late) of Gd-EOB-DTPA were calculated voxel-wise for the liver. Parenchyma and lesions were segmented. Pre-contrast IVIM was compared 1) between low, medium and high R_early for parenchyma 2) to post-contrast IVIM substantiated with simulations 3) between low and high R_late per lesion type.ResultsD_fast and f_fast increased (P < 0.001) with 25.6% and 33.8% between low and high R_early of Gd-EOB-DTPA. D_slow decreased (− 15.0%; P < 0.001) with increasing R_early. Gd-DOTA demonstrated similar observations. f_fast (+ 10%; P < 0.001) and D_fast (+ 6.6%; P < 0.001) increased after Gd-EOB-DTPA, while decreasing after Gd-DOTA (− 4.2% and − 5.7%, P < 0.001) and were confirmed by simulations. For focal nodular hyperplasia lesions (n = 5) D_fast and f_fast increased (P < 0.001) with increasing R_late, whereas for hepatocellular carcinoma (n = 4) and adenoma (n = 7) no differences were found.ConclusionMicroperfusion measured by IVIM reflects perfusion in a way resembling CE-MRI. Also IVIM separated intra- and extracellular MR contrast media. This underlines the potential of IVIM in quantitative liver imaging.     

Correlation of CSF neuroinflammatory molecules with leptomeningeal cortical subcortical white matter fractional anisotropy in neonatal meningitis

It has been previously hypothesized that the high fractional anisotropy (FA) values in leptomeningeal cortical subcortical white matter (LCSWM) regions of neonatal brain with bacterial meningitis is due to the presence of adhesion molecules in the subarachnoid space, which are responsible for adherence of inflammatory cells over the subarachnoid membrane. The aim of this study was to look for any relationship between FA values in LCSWM regions and various neuroinflammatory molecules (NMs) in cerebrospinal fluid (CSF) measured in neonates with bacterial meningitis. Diffusion tensor imaging was performed on 18 term neonates (median age, 10.5 days) having bacterial meningitis and 10 age-/sex-matched healthy controls. CSF enzyme-linked immunosorbent assay was performed to quantify NMs [soluble intracellular adhesion molecules (sICAM), tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta)]. Significantly increased FA values were observed in LCSWM regions of the patients compared to controls. A significant positive correlation was observed between FA values in LCSWM regions and NMs [sICAM (r=0.67, P=.006), TNF-alpha (r=0.69, P=.005) and IL-1beta (r=0.82, P=.000)] in CSF of these patients. No difference in FA values (P=.99) in LCSWM regions was observed between patients with sterile (0.12+/-0.02) and culture-positive CSF study (0.12+/-0.02). FA may be used as noninvasive surrogate marker of NMs in neonatal meningitis in assessing therapeutic response in future.     

Multi-level Assessment Cerebrospinal Fluid Flow in Patients with Chiari I Malformation

The purpose of this study is to characterize the cerebrospinal fluid (CSF) flow throughout the cardiac cycle in the conditions of Chiari I at intracranial and cervical levels. Magnetic resonance imaging studies were examined with phase-contrast magnetic resonance imaging retrospectively cardiac triggered (Quantitative Flow technique). 60 healthy volunteers (control group) and 12 patients with the anomaly of Chiari I (patient’s group) were investigated. Mean velocity, mean flux and peak velocity values of CSF flow at the five levels (the Sylvian aqueduct, the fourth ventricle, the Magendie’s foramen, subarachnoid space of the foramen occipital magnum and the cervical level) were defined. Analysis of differences between respective mean values of CSF flow has shown that CSF flow characteristics have the highest values in the Sylvian aqueduct and on the cervical level in both groups. Our findings show that mean velocity and mean flux of antegrade (from head to feet) flow have significantly higher values in comparison with the retrograde flow (from feet to head) through investigated structures, respectively (p < 0.01). Our findings show the importance of multi-level cerebrospinal fluid flow assessment and allow investigating this system as a single whole, with their relationships and interaction laws.     

Objective evaluation of acute adverse events and image quality of gadolinium-based contrast agents (gadobutrol and gadobenate dimeglumine) by blinded evaluation. Pilot study

Purpose

The purpose was to objectively evaluate a recently FDA-approved gadolinium-based contrast agent (GBCA) in comparison to our standard GBCA for acute adverse events and image quality by blinded evaluation.

Methods

Evaluation was made of a recently FDA-approved GBCA, gadobutrol (Gadavist; Bayer), in comparison to our standard GBCA, gadobenate dimeglumine (MultiHance; Bracco), in an IRB- and HIPAA-compliant study. Both the imaging technologist and patient were not aware of the brand of the GBCA used. A total of 59 magnetic resonance studies were evaluated (59 patients, 31 men, 28 women, age range of 5–85 years, mean age of 52 years). Twenty-nine studies were performed with gadobutrol (22 abdominal and 7 brain studies), and 30 studies were performed with gadobenate dimeglumine (22 abdominal and 8 brain studies). Assessment was made of acute adverse events focusing on objective observations of vomiting, hives, and moderate and severe reactions. Adequacy of enhancement was rated as poor, fair and good by one of two experienced radiologists who were blinded to the type of agent evaluated.

Results

No patient experienced acute adverse events with either agent. The target minor adverse events of vomiting or hives, and moderate and severe reactions were not observed in any patient. Adequacy of enhancement was rated as good for both agents in all patients.

Conclusions

Objective, blinded evaluation is feasible and readily performable for the evaluation of GBCAs. This proof-of-concept study showed that both GBCAs evaluated exhibited consistent good image quality and no noteworthy adverse events.     

Studies of pathology and VEGF expression in rabbit cerebrospinal fluid metastasis: application of dynamic contrast-enhanced MRI

Objective

The objective was to analyze the correlation of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with vascular endothelial growth factor (VEGF) protein expression and to assess the potential application of DCE-MRI to the rabbit cerebrospinal fluid (CSF) metastasis model.

Methods

Thirty New Zealand rabbits were divided into experimental and control groups. In the experimental group, VX2 tumor cells were injected into the subarachnoid space at the plane of cisterna magna in 24 rabbits. In the control group, physiological saline was injected into the subarachnoid space at the plane of cisterna magna in six rabbits. DCE-MRI was performed at multiple time points, and several pharmacokinetic parameters, including K^trans, K_ep and V_e, were calculated. Also, VEGF levels in plasma and CSF were evaluated by enzyme-linked immunosorbent assay prior to DCE-MRI examination. After DCE-MRI examination, the rabbits were sacrificed, and the corresponding tumor specimens were harvested. Hematoxylin–eosin staining and VEGF immunohistochemical staining were carried out, and VEGF expression in the specimens was evaluated by the immunohistochemical scoring system.

Results

Vascular endothelial growth factor positive staining was localized in the cytoplasm and cell membranes of tumor cells, as well as in a subset of epithelial cells. Both VEGF immunohistochemical scores and VEGF expression in CSF and plasma exhibited positive correlations with K^trans and K_ep values as demonstrated by rank correlation statistical analysis.

Conclusions

Vascular endothelial growth factor expression in plasma and CSF in the CSF metastasis model was higher than in normal tissues. Therefore, DCE-MRI reliably indicated VEGF expression in the rabbit CSF metastasis model.     

Greatly attenuated experimental autoimmune encephalomyelitis in aquaporin-4 knockout mice

Background  

The involvement of astrocyte water channel aquaporin-4 (AQP4) in autoimmune diseases of the central nervous system has been suggested following the identification of AQP4 autoantibodies in neuromyelitis optica, an inflammatory demyelinating disease.     

Transverse relaxation of cerebrospinal fluid depends on glucose concentration

PurposeTo evaluate the biophysical processes that generate specific T₂ values and their relationship to specific cerebrospinal fluid (CSF) content.Materials and methodsCSF T_2s were measured ex vivo (14.1 T) from isolated CSF collected from human, rat and non-human primate. CSF T_2s were also measured in vivo at different field strength in human (3 and 7 T) and rodent (1, 4.7, 9,4 and 11.7 T) using different pulse sequences. Then, relaxivities of CSF constituents were measured, in vitro, to determine the major molecule responsible for shortening CSF T₂ (2 s) compared to saline T₂ (3 s). The impact of this major molecule on CSF T₂ was then validated in rodent, in vivo, by the simultaneous measurement of the major molecule concentration and CSF T₂.ResultsEx vivo CSF T₂ was about 2.0 s at 14.1 T for all species. In vivo human CSF T₂ approached ex vivo values at 3 T (2.0 s) but was significantly shorter at 7 T (0.9 s). In vivo rodent CSF T₂ decreased with increasing magnetic field and T₂ values similar to the in vitro ones were reached at 1 T (1.6 s). Glucose had the largest contribution of shortening CSF T₂ in vitro. This result was validated in rodent in vivo, showing that an acute change in CSF glucose by infusion of glucose into the blood, can be monitored via changes in CSF T₂ values.ConclusionThis study opens the possibility of monitoring glucose regulation of CSF at the resolution of MRI by quantitating T₂.     

Experimental cerebral infarction in the rat: utility of Gd-DOTA for MR imaging

Nineteen rats presenting a very small (about 2-mm diameter), superficial cerebral infarction were studied with MR-imaging (1.89 Tesla) before and after injection of Gd-DOTA. Fifteen rats examined 1 or 2 hr, and 2, 3, 4, 5, 7, or 10 days after lesion induction, received 0.5 mmol Gd-DOTA/kg body weight. Four other rats presenting a 4-day-old lesion, received 0.1, 0.2, or 0.6 mmol Gd-DOTA/kg. Each rat underwent one imaging study comprising T2-weighted spin-echo (SE) images (3000/100) with subsequent injection of Gd-DOTA followed by 12 consecutive series of T1-weighted SE images (320/40), each taking 6 min. Using 0.5 mmol Gd-DOTA/kg, early (immediate) and long-lasting (more than 1 hour) visualization of lesions of varying age (1 hr to up to 10 days) was possible and at appropriate time intervals after injection, the visualization of the lesion was clearer and more complete than with T2-weighted images. Even in the rats studied with smaller doses of the contrast agent (0.1 or 0.2 mmol/kg), postcontrast T1-weighted images provided superior delineation of the lesions as compared to T2-weighted images.     

Synthesis and structural details of MSr2RECu2O7+δ(M-1212;0⩽δ<1) compounds with M = Al,Nb, Fe,Ru, Ga & Co and RE = Eu,Y

Synthesis and structural details of MSr₂RECu₂O_z (M-1212) compounds with M = Ga, Nb, Fe, Al and Co) and RE = Eu, Y are reported. Reitveld refinement of X-ray diffraction (XRD) patterns shows that all compounds are crystallized in single phase. Nb-, Fe- and Al-1212 possess tetragonal P4/mmm space group structure while the Ga-1212 and Co-1212 are crystallized in orthorhombic Ima2 space group. The change of space group from P4/mmm to Ima2 indicating towards the doubling of unit cell. The buckling angle [Cu(2)–O(2)–Cu(2) angle] shows that most of the studied samples are heavily under doped and hence they could not exhibit superconductivity. Thermogravimetric (TGA) analysis shows the M-1212 compounds to be more stable than widely studied 90 K superconductor Cu-1212 (RE-123).     

Effects of diagnostic ultrasound-targeted microbubble destruction on permeability of normal liver in rats

This work investigated the effect of diagnostic ultrasound-targeted microbubble destruction (UTMD) on the permeability of normal liver tissue and the safety of this technique. One hundred and four rats were divided into four groups: the control group, the microbubble-only (MB) group, the ultrasound-only (US) group, and the ultrasound-targeted microbubble destruction group (UTMD). The permeabilities of capillaries and cell membranes were determined using Evans blue and lanthanum nitrate as tracers, respectively. The amount of Evans blue was approximately fourfold higher in the UTMD group than in the control, MB-only, and US-only groups (all P < 0.01). Evans blue extravasation, visualized as red fluorescence, was detectable by laser confocal scanning microscopy in the parenchyma only in the UTMD group. Lanthanum nitrate-tracing transmission electron microscopy examination indicated that intracellular lanthanum was detectable in the cytoplasm only in the UTMD group. Blood chemical analysis indicated that the effect of diagnostic ultrasound-targeted microbubble destruction on the rats’ serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels was transient and recoverable and that this technique had no obvious effect on renal function. Cellular swelling was observed in liver cells in the UTMD group at 0.5 h, but this swelling was no longer apparent after 1 week. These results suggest that diagnostic ultrasound-targeted microbubble destruction can increase the capillary and cell membrane permeabilities in normal liver tissue without a significant increase in hepatic and renal toxicity.     

氨基酸共聚物修饰的生物相容性MRI造影剂

通过天门冬氨酸(Asp)、异亮氨酸(Ile)热缩聚反应,制备了天门冬氨酸-异亮氨酸共聚物(AI),通过乙二胺(EDA)胺化,并与1,4,7,10-四氮杂环十二烷-1,4,7,10-四羧酸(DOTA)连接,再与钆离子(Gd3+)络合,合成了生物相容性大分子磁共振成像(MRI)造影剂——AI-EDA-DOTA-Gd.运用红外光谱(IR)、核磁共振(NMR)、电感耦合等离子谱(ICP)等方法对其进行结构表征,并通过弛豫性能、溶血性质、急性毒性及动物体内成像对其进行综合评价.体外弛豫结果表明,AI-EDA-DOTA-Gd的纵向弛豫效率(r_1=12.6mmol~(–1)×L×s~(–1))是商用造影剂Gd-DOTA(r_1=5.8 mmol~(–1)×L×s~(–1))的2.2倍.动物组织生理切片和溶血性实验结果说明其具有良好的生物相容性和较低的毒性.动物体内成像结果显示,AI-EDA-DOTA-Gd的最佳成像时间为30~70 min,注射AI-EDA-DOTA-Gd后的肝脏组织信号相比于未注射造影剂时增强了约(55.1±5.7)%.     

Tissue gadolinium deposition in renally impaired rats exposed to different gadolinium-based MRI contrast agents: Evaluation with inductively coupled plasma mass spectrometry (ICP-MS)

ObjectivesTo quantify tissue gadolinium (Gd) deposition in renally impaired rats exposed to Gd-EOB-DTPA and other Gd-based MRI contrast agents by means of inductively coupled plasma mass spectrometry (ICP-MS), and to compare the differences in distribution among major organs as possible triggers for nephrogenic systemic fibrosis (NSF).MethodsA total of 15 renally impaired rats were injected with Gd-EOB-DTPA, Gd-DTPA-BMA and Gd-HP-DO3A. Gd contents of skin, liver, kidney, lung, heart, spleen, diaphragm and femoral muscle were measured by inductively coupled plasma mass spectrometry (ICP-MS). Histological assessment was also conducted.ResultsTissue Gd deposition in all organs was significantly higher (P = 0.005 ~ 0.009) in the Gd-DTPA-BMA group than in the Gd-HP-DO3A and Gd-EOB-DTPA groups. In the Gd-DTPA-BMA group, Gd was predominantly deposited in kidney (1306 ± 605.7 μg/g), followed by skin, liver, lung, spleen, femoral muscle, diaphragm and heart. Comparing Gd-HP-DO3A and Gd-EOB-DTPA groups, Gd depositions in the kidney, liver and lung were significantly lower (P = 0.009 ~ 0.011) in the Gd-EOB-DTPA group than in the Gd-HP-DO3A group although no significant differences were seen for any other organs.ConclusionsGd-EOB-DTPA is a stable and safe Gd-based contrast agent (GBCA) showing lower Gd deposition in major organs in renally impaired rats, compared with other GBCAs. This fact suggests that the risk of NSF onset would be low in the use of Gd-EOB-DTPA.     

Migration mechanisms of radionuclides from a clay repository toward adjacent aquifers and the surface

This article is a critical review of the current understanding of migration processes of solutes in clay. The major migration mechanisms are examined: advection through compaction, thermal convection, migration by hydrocarbon expulsion, gravitational flow, osmosis, molecular diffusion, hydrodynamic dispersion. Examples are taken from the Callovo-Oxfordian clays of the Paris basin in the Meuse/Haute Marne area, near Bure, where France is studying the feasibility of a potential nuclear waste disposal facility. Recent work on the helium distribution in the aquifers of the Paris Basin confirms the importance of molecular diffusion for solute transport in clays. Migration in aquifers is also described, and the major causes of uncertainties for solute migration are discussed. To cite this article: G. de Marsily et al., C. R. Physique 3 (2002) 945–959.     

Rietveld refinement and impedance spectroscopy of calcium titanate

Single phase perovskite CaTiO₃ has been synthesized by conventional solid state reaction technique. The ceramic was characterized by XRD at room temperature and its Rietveld refinement inferred orthorhombic crystal structure with the space group Pbnm. The field dependence of dielectric relaxation and conductivity was measured over a wide frequency range from room temperature to 673 K. Analysis of Nyquist plots of CaTiO₃ revealed the contribution of many electrically active regions corresponding to bulk mechanism, distribution of grain boundaries and electrode processes. The dc conductivity depicted a semiconductor to metal type transition. Frequency dependence of dielectric constant (ε′) and tangent loss (tan δ) show a dispersive behavior at low frequencies and is explained on basis of Maxwell-Wagner model and Koop's theory. Both conductivity and electric modulus formalisms have been employed to study the relaxation dynamics of charge carriers. The variation of ac conductivity with frequency at different temperatures obeys the universal Jonscher's power law (σ_ac α ω^s). The values of exponent ‘s’ lie in the range 0.13 ≤ s ≤ 0.33, which in light of CBH model suggest a large polaron hopping type of conduction mechanism.     

Quantification of Flow of Cerebrospinal Fluid on Basal Level of Brain by a Phase-Contrast MRI Technique

Here we present on the ability of phase-contrast magnetic resonance imaging (MRI) to accurately measure dynamic properties of cerebrospinal fluid (CSF) flow on basal level of brain. CSF characteristics were compared in a group of 55 healthy volunteers. MRI study was performed using 1.5 T system with the following parameters: repetition time TR/echo time TE = 14/8.3 ms; flip angle FA = 15°; slice thickness = 4 mm. Velocity values of CSF flow on basal level of brain obtained in the study were statistically analyzed by capturing mean values and building confidence intervals (p = 0.05). Student’s paired t-test was performed to determine significance of the differences between mean values and between caudal and cranial CSF flows. Normal values of mean velocity, mean flux and peak velocity were defined by Q-flow technique. The highest values of CSF flow characteristics were observed in the Sylvian aqueduct and pontomedullaris cistern. Mean velocity and mean flux of caudal CSF flow had significantly higher values compared to the cranial CSF flow in all investigated structures.     

Magnetic resonance neurography of the lumbosacral plexus at 3 Tesla – CSF-suppressed imaging with submillimeter resolution by a three-dimensional turbo spin echo sequence

PurposeTo investigate magnetic resonance neurography (MRN) of the lumbosacral plexus (LSP) with cerebrospinal fluid (CSF) suppression by using submillimeter resolution for three-dimensional (3D) turbo spin echo (TSE) imaging.Materials and methodsUsing extended phase graph (EPG) analysis, the signal response of CSF was simulated considering dephasing from coherent motion for frequency-encoding voxel sizes ranging from 0.3 to 1.3 mm and for CSF velocities ranging from 0 to 4 cm/s. In-vivo MRN included 3D TSE data with frequency encoding parallel to the feet/head axis from 15 healthy adults (mean age: 28.5 ± 3.8 years, 5 females; acquisition voxel size: 2 × 2 × 2 mm³) and 16 pediatric patients (mean age: 6.7 ± 4.1 years, 7 females; acquisition voxel size: 0.7 × 0.7 × 1.4 mm³) acquired at 3 Tesla. Five of the adults were scanned repetitively with changing acquisition voxel sizes (1 × 2 × 2 mm³, 0.7 × 2× 2 mm³, and 0.5 × 2 × 2 mm³). Measurements of the bilateral ganglion of the L5 nerve root, averaged between sides, as well as the CSF in the thecal sac were obtained for all included subjects and compared between adults and pediatric patients and between voxel sizes, using a CSF-to-nerve signal ratio (CSFNR).ResultsAccording to simulations, the CSF signal is reduced along the echo train for moving spins. Specifically, it can be reduced by over 90% compared to the maximum simulated signal for flow velocities above 2 cm/s, and could be most effectively suppressed by considering a frequency-encoding voxel size of 0.8 mm or less. For in-vivo measurements, mean CSFNR was 1.52 ± 0.22 for adults and 0.10 ± 0.03 for pediatric patients (p < .0001). Differences in CSFNR were significant between measurements using a voxel size of 2 × 2 × 2 mm³ and measurements in data with reduced voxel sizes (p ≤ .0012), with submillimeter resolution (particularly 0.5 × 2 × 2 mm³) providing highest CSF suppression.ConclusionsApplying frequency-encoding voxel sizes in submillimeter range for 3D TSE imaging with frequency encoding parallel to the feet/head axis may considerably improve MRN of LSP pathology in adults in the future because of favorable CSF suppression.     

Cerebrospinal fluid promotes survival and astroglial differentiation of adult human neural progenitor cells but inhibits proliferation and neuronal differentiation

Background  

Neural stem cells (NSCs) are a promising source for cell replacement therapies for neurological diseases. Growing evidence suggests an important role of cerebrospinal fluid (CSF) not only on neuroectodermal cells during brain development but also on the survival, proliferation and fate specification of NSCs in the adult brain. Existing in vitro studies focused on embryonic cell lines and embryonic CSF. We therefore studied the effects of adult human leptomeningeal CSF on the behaviour of adult human NSCs (ahNSCs).     

Tiny golden angle stack-of-stars (tygaSoS) free-breathing functional lung imaging

PurposeMRI of the lung parenchyma is still challenging due to cardiac and respiratory motion, and the low proton density and short T₂*. Clinical feasible MRI methods for functional lung assessment are of great interest. It was the objective of this study to evaluate the potential of combining the ultra-short echo-time stack-of-stars approach with tiny golden angle (tyGASoS) profile ordering for self-gated free-breathing lung imaging.MethodsFree-breathing tyGASoS data were acquired in 10 healthy volunteers (3 smoker (S), 7 non-smoker (NS)). Images in different respiratory phases were reconstructed applying an image-based self-gating technique. Resulting image quality and sharpness, and parenchyma visibility were qualitatively scored by three blinded independent reader, and the signal-to-noise ratio (SNR), proton fraction (f_P) and fractional ventilation (FV) quantified.ResultThe imaging protocol was well tolerated by all volunteers. Image quality was sufficient for subsequent quantitative analysis in all cases with good to excellent inter-reader reliability. Between expiration (EX) and inspiration (IN) significant differences (p < 0.001) were observed in SNR (EX: 3.73 ± 0.89, IN: 3.14 ± 0.74) and f_P (EX: 0.27 ± 0.09, IN: 0.25 ± 0.08). A significant (p < 0.05) higher f_P (EX/IN: 0.22 ± 0.07/0.21 ± 0.07 (NS), 0.33 ± 0.07/0.30 ± 0.06 (S)) was observed in the smoker group. No significant FV differences resulted between S and NS.ConclusionThe study proves the feasibility of free-breathing tyGASoS for multiphase lung imaging. Changes in f_P may indicate an initial response in the smoker group and as such proves the sensitivity of the proposed technique. A major limitation in FV quantification rises from the large inter-subject variability of breathing patterns and amplitudes, requiring further consideration.     

MR tracking of magnetically labeled mesenchymal stem cells in rats with liver fibrosis

Purpose

In vivo magnetic resonance (MR) tracking of magnetically labeled bone marrow mesenchymal stem cells (BMSCs) administered via the mesenteric vein to rats with liver fibrosis.

Materials and Methods

Rat BMSCs were labeled with superparamagnetic iron oxide (SPIO) and the characteristics of the BMSCs after labeling were investigated. Eighteen rats with CCL4-induced liver fibrosis were randomized to three groups to receive SPIO-labeled BMSCs (BMSC-labeled group), cell-free SPIO (SPIO group), or unlabeled BMSCs (control group). MR imaging of the liver was performed at different time points, and signal-to-noise ratio (SNR) of the liver was measured. In vivo distribution of delivered BMSCs was assessed by histological analysis.

Results

Labeling of BMSCs with SPIO did not significantly alter cell viability and proliferation activity. In BMSC-labeled group, the liver SNR immediately decreased from 8.56±0.26 to 3.53±0.41 at 1 h post injection and remained at a significantly lower level till 12 days (P<.05 versus the level before). By contrast, the liver SNR of the SPIO group almost recovered to the preinjection level (P=.125) at 3 days after a transient decrease. In control group, the liver SNR demonstrated no significant difference at the tested time points. Additionally, Prussian blue-positive cells were mainly distributed in the liver parenchyma, especially in injured areas.

Conclusion

The magnetically labeled BMSCs infused through the mesenteric vein can be detected in the fibrotic liver of rats using in vivo MR imaging up to 12 days after injection.     

Novel diffusion tensor imaging methodology to detect and quantify injured regions and affected brain pathways in traumatic brain injury

Purpose

To develop and apply diffusion tensor imaging (DTI)-based normalization methodology for the detection and quantification of sites of traumatic brain injury (TBI) and the impact of injury along specific brain pathways in (a) individual TBI subjects and (b) a TBI group.

Materials and Methods

Normalized DTI tractography was conducted in the native space of 12 TBI and 10 age-matched control subjects using the same number of seeds in each subject, distributed at anatomically equivalent locations. Whole-brain tracts from the control group were mapped onto the head of each TBI subject. Differences in the fractional anisotropy (FA) maps between each TBI subject and the control group were computed in a common space using a t test, transformed back to the individual TBI subject's head space, and thresholded to form regions of interest (ROIs) that were used to sort tracts from the control group and the individual TBI subject. Tract counts for a given ROI in each TBI subject were compared to group mean for the same ROI to quantify the impact of injury along affected pathways. The same procedure was used to compare the TBI group to the control group in a common space.

Results

Sites of injury within individual TBI subjects and affected pathways included hippocampal/fornix, inferior fronto-occipital, inferior longitudinal fasciculus, corpus callosum (genu and splenium), cortico-spinal tracts and the uncinate fasciculus. Most of these regions were also detected in the group study.

Conclusions

The DTI normalization methodology presented here enables automatic delineation of ROIs within the heads of individual subjects (or in a group). These ROIs not only localize and quantify the extent of injury, but also quantify the impact of injury on affected pathways in an individual or in a group of TBI subjects.