Regional atrophy of transcallosal prefrontal connections in cognitively normal APOE ϵ4 carriers

Purpose

To investigate the possible effect of the APOE ?4 allele on age‐related regional volume loss within the corpus callosum (CC) in healthy ?4 allele carriers compared with noncarriers.

Materials and Methods

A total of 211 subjects, ages 27 to 83 years, 51 ?4 carriers and 160 noncarriers underwent T1‐weighted MRI scan. All subjects had normal MRI scan and performed within normal range on a neuropsychological battery of tests. CC was segmented into seven functionally relevant regions using a previously published probabilistic map of the CC connectivity. We measured the volumes of the CC and its subregions. We used a regression model (with volumes as dependent and age as independent variables) and compared the slopes between carriers and noncarriers using an analysis of covariance model. We also carried out voxel‐based‐morphometry analysis to investigate the possible effect of the APOE ?4 gene on the gray matter.

Results

We found that the volume of the CC and all subregions decreased with increasing age in both groups. The slope was steeper in the APOE ?4 carriers compared withthe noncarriers particularly in the prefrontal region (P = 0.02). No gray matter differences were observed between the two groups.

Conclusion

APOE ?4 polymorphism is associated with accelerated age‐related volume loss in the prefrontal callosal tracts without gray matter loss. This result suggests the role of APOE ?4 in the brain aging by primarily affecting white matter structures particularly in the frontal lobe. J. Magn. Reson. Imaging 2009;29:1021–1026. © 2009 Wiley‐Liss, Inc.

     

Effect of cerebral spinal fluid suppression for diffusional kurtosis imaging

Purpose:

To evaluate the cerebral spinal fluid (CSF) partial volume effect on diffusional kurtosis imaging (DKI) metrics in white matter and cortical gray matter.

Materials and Methods:

Four healthy volunteers participated in this study. Standard DKI and fluid‐attenuated inversion recovery (FLAIR) DKI experiments were performed using a twice‐refocused‐spin‐echo diffusion sequence. The conventional diffusion tensor imaging (DTI) metrics of fractional anisotropy (FA), mean, axial, and radial diffusivity (MD, D_‖, D_?) together with DKI metrics of mean, axial, and radial kurtosis (MK, K_‖, K_?), were measured and compared. Single image slices located above the lateral ventricles, with similar anatomical features for each subject, were selected to minimize the effect of CSF from the ventricles.

Results:

In white matter, differences of less than 10% were observed between diffusion metrics measured with standard DKI and FLAIR‐DKI sequences, suggesting minimal CSF contamination. For gray matter, conventional DTI metrics differed by 19% to 52%, reflecting significant CSF partial volume effects. Kurtosis metrics, however, changed by 11% or less, indicating greater robustness with respect to CSF contamination.

Conclusion:

Kurtosis metrics are less sensitive to CSF partial voluming in cortical gray matter than conventional diffusion metrics. The kurtosis metrics may then be more specific indicators of changes in tissue microstructure, provided the effect sizes for the changes are comparable. J. Magn. Reson. Imaging 2013;37:365–371. © 2012 Wiley Periodicals, Inc.

     

Phase‐contrast magnetic resonance quantification of normal pulmonary venous return

Purpose

To assess the feasibility of phase‐contrast magnetic resonance (PCMR) in quantifying the pulmonary venous return in normal subjects.

Materials and Methods

PCMR was performed in 12 healthy adult volunteers (mean age 38 years, range 27–60 years; 9 men; body surface area 1.81 ± 0.15 m²) for the ascending and descending aorta, caval veins, main and branch pulmonary arteries, and pulmonary veins. Two readers independently quantified blood flow in all subjects.

Results

Intraobserver differences were ?2.0% (95% confidence interval [CI]: ?9.9% to 5.9%), ?4.5% (95% CI: ?15.6% to 6.5%), and ?0.7% (95% CI: ?4.5% to 3.0%) for all vessels, pulmonary veins, and other great vessels, respectively. Interobserver differences were ?2.0% (95% CI: ?10.6% to 6.6%), ?3.1% (95% CI: ?16.0% to 9.9%), and ?1.4% (95% CI: ?6.4% to 3.5%) for all vessels, pulmonary veins, and other great vessels, respectively. Pulmonary venous flow volume showed high correlations with the volumes of the pulmonary arterial flow, systemic arterial flow, and systemic venous flow (r = 0.76–0.92, P < 0.005).

Conclusion

Flow quantification of normal pulmonary venous return using PCMR is feasible with high reproducibility and accuracy. J. Magn. Reson. Imaging 2009;29:588–594. © 2009 Wiley‐Liss, Inc.

     

Cortical calcification in sturge–weber syndrome on MRI‐SWI: Relation to brain perfusion status and seizure severity

Purpose:

To determine the relationship between calcified cortex and perfusion status of white matter and seizure severity in patients with Sturge–Weber Syndrome (SWS), a sporadic neurocutaneous disorder characterized by a leptomeningeal angioma, progressive brain ischemia, and a high incidence of seizures using susceptibility weighted imaging (SWI) and dynamic susceptibility contrast‐enhanced perfusion weighted imaging (DSC‐PWI).

Materials and Methods:

Fifteen children (ages: 0.9–10 years) with unilateral SWS prospectively underwent magnetic resonance imaging (MRI). The degree of cortical calcification was assessed using SWI while perfusion status was quantified using DSC‐PWI images (asymmetries of various perfusion parameters). Comparisons between calcification, perfusion status, and seizure variables were performed.

Results:

Patients with severely calcified cortex demonstrated significantly lower perfusion in the ipsilateral white matter (mean asymmetry: ?0.52 ± 0.22) as compared to patients with only mildly calcified cortex or no calcification (mean asymmetry: 0.08 ± 0.25). Patients with severely calcified cortex also suffered from a higher seizure burden (a composite measure of seizure frequency and epilepsy duration; P = 0.01) and a trend for earlier seizure onset and longer epilepsy duration.

Conclusion:

Severe calcification in the affected hemisphere is related to severely decreased perfusion in underlying white matter and is associated with more severe epilepsy in SWS patients. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.

     

Association of placental volume measured by MRI and birth weight percentile

Purpose:

To investigate if placental volume in the second trimester of pregnancy is related to uterine artery blood flow and neonatal birth weight.

Materials and Methods:

In 83 singleton pregnancies at 24–29 weeks' gestation, uterine artery pulsatility index (PI) was measured by Doppler ultrasound and placental volume was calculated from images obtained by magnetic resonance imaging (MRI) at 1.5T. The significance of the association between placental volume, uterine artery PI, and birth weight was examined.

Results:

In 37 normal pregnancies resulting in delivery of neonates with birth weight at or above the 10th percentile, the median placental volume increased with gestational age from 363 cm³ at 24 weeks to 515 cm³ at 29 weeks. In 46 pregnancies that resulted in delivery of small for gestational age (SGA) neonates with birth weight below the 10th percentile the median placental volume, corrected for gestational age, was significantly decreased by 120 cm³ (P < 0.0001) and median uterine artery PI was increased (1.87 vs. 1.59, P < 0.0001). There were significant associations between placental volume and both uterine artery PI (r = ?0.677, P < 0.0001) and birth weight percentile (r = 0.658, P < 0.0001).

Conclusion:

Placental volume during the second trimester is smaller in pregnancies that subsequently deliver SGA neonates and the measurement is related to placental perfusion. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.

     

Imaging age‐related cognitive decline: A comparison of diffusion tensor and magnetization transfer MRI

Purpose

To determine which MR technique was the most sensitive to age‐related white matter damage. We compared both diffusion tensor imaging (DTI) and magnetization transfer (MT) maps to determine which technique correlated most strongly with cognitive function in a middle‐aged and elderly community population.

Materials and Methods

In all, 64 healthy subjects (aged 50–90) underwent MRI and neuropsychology. Histograms were generated for white matter mean diffusivity (MD), fractional anisotropy (FA), and MT ratio (MTR). White matter hyperintensity volume (WMH) and brain volume were also determined. Composite neuropsychological scores were derived for 4 cognitive domains (executive function, working memory, episodic memory, and information processing speed).

Results

All MRI parameters correlated with age (FA r = 0.726, P < 0.001; MD r = ?0.619 P < 0.001, MTR r = ?0.566, P < 0.001, WMH r = 0.511, P < 0.001). All MRI parameters correlated with cognition, but DTI, and particularly FA, correlated most strongly. Adding DTI parameters explained more variance in cognition than WMH alone; the increase was greatest with FA, which alone explained 45%, 33%, and 25% of the variance in cognition for information processing speed, episodic memory, and executive function, respectively.

Conclusion

DTI appears the most sensitive imaging parameter to determine age‐related white matter damage. The stronger relationship with FA suggests that axonal damage is important in age‐related cognitive decline. J. Magn. Reson. Imaging 2009;29:23–30. © 2008 Wiley‐Liss, Inc.

     

Changes in hepatic venous morphology with cirrhosis on MRI

Purpose

To identify changes in vascular morphology on magnetic resonance imaging (MRI) in patients with cirrhosis and to compare these findings to liver donors.

Materials and Methods

Patients undergoing liver transplantation with biopsy‐proven cirrhosis (n = 74) and liver donor candidates (n = 85) underwent dynamic gadolinium‐enhanced 3D MR at 1.5T. Vessel diameters were measured independently by three radiologists and features of cirrhosis were identified and correlated with cirrhosis.

Results

Hepatic veins were smaller in patients with cirrhosis (4.9, 4.5, and 5.0 mm for right, middle, and left vs. 9.9, 7.6, and 8.9 mm in donors, P ? 0.001) and were negatively correlated with cirrhosis (P < 0.001). Right hepatic vein (RHV) <5 mm diagnosed cirrhosis with 59% sensitivity and 99% specificity; the sensitivity and specificity were 88% and 85% for RHV <7 mm. Main portal vein was minimally larger in cirrhosis, 14 versus 12 mm (P < 0.001) in donors. Right portal veins were smaller in cirrhotic patients, 6.5 and 6.2 mm compared to 8.4 and 7.6 mm (P ? 0.001), respectively, in donors.

Conclusion

Vascular features of cirrhosis include small hepatic veins, minimally enlarged main portal vein, and small intrahepatic portal veins; these features may facilitate identification of cirrhosis. J. Magn. Reson. Imaging 2009;29:1085–1092. © 2009 Wiley‐Liss, Inc.

     

Validation of functional diffusion maps (fDMs) as a biomarker for human glioma cellularity

Purpose:

To present comprehensive examinations of the assumptions made in functional diffusion map (fDM) analyses and provide a biological basis for fDM classification.

Materials and Methods:

Sixty‐nine patients with gliomas were enrolled in this study. To determine the sensitivity of apparent diffusion coefficients (ADCs) to cellularity, cell density from stereotactic biopsy specimens was correlated with preoperative ADC maps. For definition of ADC thresholds used for fDMs, the 95% confidence intervals (CI) for changes in voxel‐wise ADC measurements in normal appearing tissue was analyzed. The sensitivity and specificity to progressing disease was examined using both radiographic and neurological criteria.

Results:

Results support the hypothesis that ADC is inversely proportional to cell density with a sensitivity of 1.01 × 10^?7 [mm²/s]/[nuclei/mm²]. The 95% CI for white matter = 0.25 × 10^?3 mm²/s, gray matter = 0.31 × 10^?3 mm²/s, a mixture of white and gray matter = 0.40 × 10^?3 mm²/s, and a mixture of white matter, gray matter, and cerebrospinal fluid = 0.75 × 10^?3 mm²/s. Application of these measurements as ADC thresholds produce varying levels of sensitivity and specificity to disease progression, which were all significantly better than chance.

Conclusion:

This study suggests fDMs are valid biomarkers for brain tumor cellularity. J. Magn. Reson. Imaging 2010;31:538–548. ©2010 Wiley‐Liss, Inc.

     

Brain iron detected by SWI high pass filtered phase calibrated with synchrotron X‐ray fluorescence

Purpose:

To test the ability of susceptibility weighted images (SWI) and high pass filtered phase images to localize and quantify brain iron.

Materials and Methods:

Magnetic resonance (MR) images of human cadaver brain hemispheres were collected using a gradient echo based SWI sequence at 1.5T. For X‐ray fluorescence (XRF) mapping, each brain was cut to obtain slices that reasonably matched the MR images and iron was mapped at the iron K‐edge at 50 or 100 μm resolution. Iron was quantified using XRF calibration foils. Phase and iron XRF were averaged within anatomic regions of one slice, chosen for its range of iron concentrations and nearly perfect anatomic correspondence. X‐ray absorption spectroscopy (XAS) was used to determine if the chemical form of iron was different in regions with poorer correspondence between iron and phase.

Results:

Iron XRF maps, SWI, and high pass filtered phase data in nine brain slices from five subjects were visually very similar, particularly in high iron regions. The chemical form of iron could not explain poor matches. The correlation between the concentration of iron and phase in the cadaver brain was estimated as c_Fe [μg/g tissue] = 850Δ? + 110.

Conclusion:

The phase shift Δ? was found to vary linearly with iron concentration with the best correspondence found in regions with high iron content. J. Magn. Reson. Imaging 2010;31:1346–1354. © 2010 Wiley‐Liss, Inc.

     

Caudate nuclei volume,diffusion tensor metrics,and T2 relaxation in healthy adults and relapsing‐remitting multiple sclerosis patients: Implications for understanding gray matter degeneration

Purpose

To investigate the utility of caudate nuclei (CN) macro‐ and microstructural metrics as markers of gray matter degeneration in healthy adults and relapsing‐remitting multiple sclerosis (RRMS) patients.

Materials and Methods

The normal age‐ and pathology‐related changes in caudate nuclei volume (CNV), the corresponding diffusion tensor metrics, and the T₂ relaxation times were measured in a cohort of 32 healthy adults (12 men/20 women; age range 21–59 years) and 32 age‐matched RRMS patients (8 men/34 women; age range 21–57 years).

Results

Smaller values in both the absolute CNV and the caudate volume ratio relative to the total intracranial volume (CNVp) were observed in the RRMS group relative to healthy controls. The fractional anisotropy (FA), based on the diffusion tensor imaging (DTI) of the CN increased with age in healthy adults (r = 0.52; P = 0.003) but not in patients (r = 0.28; P = 0.12). The caudate FA value was approximately 9% larger in RRMS patients relative to controls (P = 0.001). The mean diffusivity of the CN was greater in the RRMS group compared to controls (P = 0.02). The caudate T₂ relaxation times were smaller in the RRMS group relative to the control group (3% reduction, P = 0.05). T₂ relaxation times did not exhibit age‐related changes (P > 0.35) in either cohort. Strong and significant correlations between CNVp and whole‐brain lesion load (r = ?0.48; P = 0.005) and whole‐brain CSF fraction (r = ?0.46; P = 0.01) were also noted.

Conclusion

These preliminary findings indicate that caudate DTI‐derived metrics can serve as potential quantitative radiological markers of MS pathology. J. Magn. Reson. Imaging 2009;29:70–77. © 2008 Wiley‐Liss, Inc.

     

Characterization of the regional distribution of skeletal muscle adipose tissue in type 2 diabetes using chemical shift-based water/fat separation

Purpose:

To show the feasibility of assessing the spatial distribution of skeletal muscle adipose tissue using chemical shift‐based water/fat separation and to characterize differences in calf intermuscular adipose tissue (IMAT) compartmentalization in patients with type 2 diabetes mellitus (T2DM) compared to healthy age‐matched controls.

Materials and Methods:

A chemical shift‐based water/fat separation approach using a multiecho 3D spoiled gradient echo sequence was applied in a study of 64 patients, including 35 healthy controls and 29 subjects with T2DM. Masks were defined based on manual segmentations to compute fat volume within different compartments, including regions of subcutaneous adipose tissue (SAT) and six muscular regions. IMAT was divided into two compartments representing fat within the muscular regions (intraMF) and fat between the muscular regions (interMF). Two‐sample Student's t‐tests were used to compare fat volumes between the two groups.

Results:

The subjects with T2DM had a lower volume of SAT compared to the healthy controls (P = 4 × 10^?5). There was no statistically significant difference in the IMAT volume between the two groups. However, the intraMF volume normalized by the IMAT volume was higher in the diabetics compared to the controls (P = 0.006).

Conclusion:

Chemical shift‐based water/fat separation enables the quantification of fat volume within localized muscle regions, showing that the IMAT regional distribution is significantly different in T2DM compared to normal controls. J. Magn. Reson. Imaging 2012;35:899–907. © 2011 Wiley Periodicals, Inc.

     

Correlation of iron in the hippocampus with MMSE in patients with Alzheimer's disease

Purpose

To investigate the brain iron deposits in patients with Alzheimer's disease (AD) and healthy age‐matched controls using phase imaging.

Materials and Methods

Twenty‐six AD patients and 24 healthy controls were recruited. A three‐dimensional high‐resolution, gradient‐echo sequence was used to acquire phase data in the coronal plane. A high‐pass filter was used to remove the phase variation caused by field inhomogeneity. The regions evaluated included the bilateral putamen, globus pallidus, and the head and body of the hippocampus.

Results

Significantly lower phase values in both the basal ganglion and hippocampus were revealed in the AD group compared to the normal controls (P < 0.05). The phase value in the right side of the head of the hippocampus had a moderate positive correlation with the MMSE score (r= 0.603, P = 0.000) and a negative correlation with the duration of the disease (r = ?0.677, P = 0.013). Using ?0.0972 radians as an optimal cutoff value, the sensitivity and specificity for differentiation between AD and normal controls reached 95.8 and 80.8%, respectively.

Conclusion

Phase imaging proved to be a useful method for the differentiation between normal controls and AD patients. An investigation of the excessive accumulation of iron in the hippocampus may help us better understand the pathologic process and neuropsychological dysfunction of AD disease. J. Magn. Reson. Imaging 2009;29:793–798. © 2009 Wiley‐Liss, Inc.

     

Blood oxygen level-dependent (BOLD) MRI of diabetic nephropathy: preliminary experience

Purpose:

To evaluate the blood oxygen level‐dependent (BOLD) magnetic resonance imaging (MRI) findings in kidneys of patients with diabetic nephropathy.

Materials and Methods:

BOLD MRI of the kidneys (1.5 T, multigradient‐recalled‐echo sequence with 12 echoes) was performed in 20 patients with diabetic nephropathy (moderate to severe chronic kidney disease: n = 14; mild chronic kidney disease: n = 6), and seven healthy volunteers. The medullary and cortical R2* values were compared between patients with diabetic nephropathy and healthy volunteers using Student's t‐tests.

Results:

The mean medullary R2* values were lower in patients with diabetic nephropathy compared to healthy volunteers (13.8 ± 2.4 sec^?1 vs. 19.3 ± 1.2 sec^?1, P = 0.0002). The cortical R2* values were not significantly different between the two groups (11.1 ± 0.9 sec^?1 vs. 11.5 ± 0.7 sec^?1, P = 0.7). A multiple logistic regression model using patient age, gender, and degree of chronic kidney disease (none, mild, or moderate to severe) as variables showed that the degree of kidney disease was independently associated with a decrease in medullary R2* values (P = 0.005).

Conclusion:

The medullary R2* values were lower in patients with diabetic nephropathy compared to healthy volunteers. J. Magn. Reson. Imaging 2011;33:655–660. © 2011 Wiley‐Liss, Inc.

     

Diagnostic utility of diffusion‐weighted MR imaging and apparent diffusion coefficient value for the diagnosis of adrenal tumors

Purpose

To determine the utility of diffusion‐weighted MR imaging (DWI) for the diagnosis of adrenal tumors.

Materials and Methods

Forty‐two patients (24 men and 18 women; age, 61.5 ± 12.7 years old; range, 34–86 years) with 43 adrenal tumors (11 functioning cortical adenomas, 20 nonfunctioning cortical adenomas, 7 metastatic tumors, and 5 pheochromocytomas) were retrospectively investigated. DWIs were obtained by single‐shot spin‐echo type echo‐planar imaging sequence (1.5 Tesla [T]; TR = 8000 ms, TE = 72, b‐factor = 0 and 1000 s/mm²), and apparent diffusion coefficient (ADC) value was calculated. Chemical shift images were obtained by gradient echo sequence (TR = 161, TE = 2.38 [out‐of‐phase, OP] and 4.76 [in‐phase, IP], FA = 60), and the signal intensity index (SII; [IP‐OP]/IP *100%) was calculated.

Results

There was no difference in ADC values between adenomas (1.09 ± 0.29*10^?3 mm²/s; range, 0.52–1.64) and metastatic tumors (0.85 ± 0.26*10^?3; 0.51–1.23; p = 0.14). Pheochromocytomas showed the higher mean ADC value (1.59 ± 0.34*10^?3; 1.04–1.96) compared with those of adenomas or metastatic tumors (P < 0.05 and P < 0.005, respectively). The mean SII of adenomas (62.1 ± 17.9%; 14.5–88.4) was significantly higher than those of pheochromocytomas (4.0 ± 10.0%; ?19.6–3.3; P < 0.005) or metastatic tumors (?1.5 ± 11.7%; ?18.3–8.2; P < 0.01). There was no correlation between ADC values and SII.

Conclusion

Although pheochromocytomas showed higher ADC values, we did not find that ADC value had diagnostic utility for differentiating adenomas and metastatic tumors. J. Magn. Reson. Imaging 2009;29:112–117. © 2008 Wiley‐Liss, Inc.

     

Age dependence of T1 perfusion MRI‐based hemodynamic parameters in human kidneys

Purpose

To determine the association between renal cortical perfusion parameters from T1‐DCE magnetic resonance imaging (MRI) and age in human kidney.

Materials and Methods

Thirty‐five patients (mean age: 53 years, SD = 15 years) were imaged using inversion recovery (IR)‐prepared FLASH (pulse repitition time [TR] = 4.4 msec, echo time [TE] 2.2 msec, inversion time [TI] = 180 msec, FA 50°, matrix 128 × 256, 0.3 sec/slice) during the injection of Gadolinium‐DTPA. Tissue concentration–time courses were deconvolved. Renal blood flow (RBF), volume of distribution (RVD), and mean transit time (MTT) were derived from the resulting impulse response function.

Results

Mean RBF, RVD, and MTT were 127 mL/min/100 mL (SD = 81 mL/min/100 mL), 40 mL/100 mL (SD 23 mL/100 mL), and 22 sec (SD = 9 sec). A significant moderately negative correlation was found between RBF and age (R = ?0.447, P = 0.007), RVD and age (R = ?0.420, P = 0.012). MTT and age did not show a significant correlation (R = 0.017, P = 0.924). Repeating this analysis for each gender revealed a moderate age dependence of RBF (R = ?0.600 with P = 0.009) and RVD (R = ?0.540 with P = 0.021) in the male group only.

Conclusion

T1‐DCE quantitative perfusion MRI was sufficiently sensitive to demonstrate a significant negative correlation of RBF and RVD with patient age. This was due to a moderate age dependence of these quantities in males that seems to be absent in females. J. Magn. Reson. Imaging 2009;29:398–403. © 2009 Wiley‐Liss, Inc.

     

Method for rapid calculation of quantitative cerebral perfusion

Purpose

To evaluate an algorithm based on algebraic estimation of T₁ values (three‐point estimation) in comparison with computational curve‐fitting for the postprocessing of quantitative cerebral perfusion scans.

Materials and Methods

Computer simulations were performed to quantify the magnitude of the expected error on T₁ and consequently cerebral perfusion using the three‐point estimation technique on a Look‐Locker (LL) EPI scan. In 50 patients, quantitative cerebral perfusion was calculated using the bookend method with three‐point estimation and curve‐fitting. The bookend method, a novel approach for calculating quantitative cerebral perfusion based on changes in T₁ values after a contrast injection, is currently being validated. The number of computations was used as a measure of computation speed for each method. Student's paired t‐test, Bland‐Altman, and correlation analyses were performed to evaluate the accuracy of estimation.

Results

There was a 99.65% reduction in the number of computations with three‐point estimation. Student's t‐test showed no significant difference in cerebral perfusion (P = 0.80, 0.49, paired t‐test N = 50, quantitative cerebral blood flow–white matter [qCBF‐WM], qCBF–gray matter [qCBF‐GM]) when compared to curve‐fitting. The results of the two techniques were strongly correlated in patients (slope = 0.99, intercept =1.58 mL/(100 g/minute), r = 0.86) with a small systemic bias of ?0.97 mL/(100 g/minute) in Bland‐Altman analysis.

Conclusion

The three‐point estimation technique is adequate for rapid calculation of qCBF. The estimation scheme drastically reduces processing time, thus making the method feasible for clinical use. J. Magn. Reson. Imaging 2008;28:1258–1265. © 2008 Wiley‐Liss, Inc.

     

Morphological and hemodynamic magnetic resonance assessment of early neonatal brain injury in a piglet model

Purpose

To investigate the utility of functional and morphological magnetic resonance imaging (MRI) to assess the extent of brain injury in a hypoxia‐ischemia (HI) piglet model and further to validate that the desired ischemic injury was successfully induced.

Materials and Methods

MRI was performed at 1.5 T in anesthetized piglets (N = 10, age = 12‐36 hours). Relative cerebral blood flow (rCBF), time‐to‐peak (TTP) contrast, and apparent diffusion coefficient (ADC) were estimated at different time points pre‐, during, and post‐HI. The effect following bilateral clamping of the carotid arteries was assessed by contrast‐enhanced MR angiography (MRA) and phase contrast MR angiography (PCA) (N = 4).

Results

A linear correlation was observed between relative cerebral perfusion reduction and cerebral ADC during HI (r² = 0.85, P < 0.05). There was no correlation between rCBF reduction during 30 minutes of HI and cerebral ADC after 30 or 150 minutes of reperfusion/reoxygenation (RR).

Conclusion

The combination of morphological and functional (perfusion and diffusion) MRI enabled consistent assessment of both the presence and absence of complete occlusion as well as the functional significance of the occlusion. J. Magn. Reson. Imaging 2004;20:8–15. © 2004 Wiley‐Liss, Inc.

     

Detecting lesions in multiple sclerosis at 4.7 tesla using phase susceptibility‐weighting and T2‐weighting

Purpose

To demonstrate 4.7 Tesla (T) imaging methods for visualizing lesions in multiple sclerosis in the human brain using phase susceptibility‐weighting and T2 weighting.

Materials and Methods

Seven patients with relapsing‐remitting multiple sclerosis were imaged at 4.7T using three‐dimensional (3D) susceptibility‐weighted imaging (SWI) with 0.90 mm³ voxel volumes, and with 2D T2‐weighted fast spin echo (T2WFSE) with 0.34 mm³ voxels and 1.84 mm³ voxels. The visibility of MS lesions at 4.7T with phase SWI and T2WFSE was assessed by independent lesion counts made by an experienced neuroradiologist, and by quantitative measures.

Results

High resolution T2WFSE at 4.7T provided excellent depiction of hyperintense lesions. When combined with phase SWI, 124 total lesions were identified of which 18% were only visible on phase SWI and not on T2WFSE. The phase lesions had a mean phase shift relative to local background of ?11.15 ± 5.97 parts per billion.

Conclusion

Imaging at 4.7T can provide both high quality, high resolution T2WFSE and SWI for visualization of lesions in multiple sclerosis. Phase susceptibility‐weighting can identify additional lesions that are not visible with high resolution T2WFSE. J. Magn. Reson. Imaging 2009;30:737–742. © 2009 Wiley‐Liss, Inc.

     

Usefulness of Gd‐EOB‐DTPA‐enhanced MR imaging in the evaluation of simple steatosis and nonalcoholic steatohepatitis

Purpose:

To evaluate the usefulness of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd‐EOB‐DTPA)‐enhanced MR imaging (EOB‐MRI) in differentiating between simple steatosis and nonalcoholic steatohepatitis (NASH), as compared with MR in‐phase/out‐of‐phase imaging. The correlations between the MR features and histological characteristics were preliminarily investigated.

Materials and Methods:

From April 2008 to October 2011, 25 patients (13 simple steatosis and 12 NASH) who underwent both EOB‐MRI and in‐phase/out‐of‐phase imaging were analyzed. The hepatobiliary‐phase enhancement ratio and signal intensity loss on opposed‐phase T1‐weighted images (fat fraction) were compared between the simple steatosis and NASH groups. In the simple steatosis and NASH groups, the correlations between enhancement ratio and histological grade/stage were explored. In the NASH group, fat fraction was correlated with the steatosis score.

Results:

The enhancement ratio in NASH was significantly lower than that in simple steatosis (P = 0.03). In the simple steatosis and NASH groups, the enhancement ratio was significantly correlated with the fibrosis stage (r = ?0.469, P = 0.018). Fat fraction in NASH was strongly correlated with the steatosis score (r = 0.728, P = 0.007).

Conclusion:

In simple steatosis and NASH, the hepatobiliary‐phase enhancement ratio of EOB‐MRI showed significant association with fibrosis stage, and may be a useful discriminating parameter compared with the fat fraction measured by in‐phase/out‐of‐phase imaging. J. Magn. Reson. Imaging 2012;37:1137–1143. © 2012 Wiley Periodicals, Inc.

     

Clinical evaluation of aortic coarctation with 4D flow MR imaging

Purpose:

To show that 4D Flow is a clinically viable tool for evaluation of collateral blood flow and demonstration of distorted blood flow patterns in patients with treated and untreated aortic coarctation.

Materials and Methods:

Time‐resolved, 3D phase contrast magnetic resonance imaging (MRI) (4D Flow) was used to assess blood flow in the thoracic aorta of 34 individuals: 26 patients with coarctation (22 after surgery or stent placement) and eight healthy volunteers.

Results:

Direct comparison of blood flow calculated with 2D and 4D phase contrast data at standard levels for analysis in coarctation patients showed good correlation and agreement (correlation coefficient r = 0.99, limits of agreement = ?20% to 20% for collateral blood flow calculations). Abnormal blood flow patterns were demonstrated at peak systole with 4D Flow visualization techniques in the descending thoracic aorta of patients but not volunteers. Marked helical flow was seen in 9 of 13 patients with angulated aortic arch geometries after coarctation repair. Vortical flow was seen in regions of poststenotic dilation.

Conclusion:

4D Flow is a fast and reliable means of evaluating collateral blood flow in patients with aortic coarctation in order to establish hemodynamic significance. It also can detect distorted blood flow patterns in the descending aorta after coarctation repair. J. Magn. Reson. Imaging 2010;31:711–718. © 2010 Wiley‐Liss, Inc.