Diffusion abnormality in posterior cingulate fiber tracts in Alzheimer’s disease: tract-specific analysis

Purpose

The aim of this study was to determine diffusion abnormalities in the posterior cingulate fiber tracts (PCFTs) in patients with Alzheimer’s disease (AD) by diffusion tensor tractography (DTT).

Materials and methods

We studied 23 AD patients and 18 age-matched normal controls who underwent magnetic resonance imaging using diffusion tensor imaging (DTI). DTT of PCFTs was generated from DTI. Mean diffusivity (MD) and fractional anisotropy (FA) were measured in co-registered voxels along with DTT of PCFTs. Student’s t-test was used to compare results between the AD patients and normal controls.

Results

The MD in PCFTs was significantly higher in AD patients than in normal controls (P = 0.019). The FA in PCFTs was significantly lower in AD patients than in normal controls (P = 0.007).

Conclusion

The abnormal MD increase and FA decrease, which is considered to indicate a net loss of barriers that restrict water molecular motion and tissue anisotropy of white matter, is consistent with neuropathological data that demonstrate partial loss of myelin, axons, and oligodendrial cells in white matter of AD brains. Our results suggest that MD and FA reflect progression of AD-related histopathological changes in the PCFTs and may represent a useful biological index for monitoring AD.     

Prognostic value of brain proton MR spectroscopy and diffusion tensor imaging in newborns with hypoxic-ischemic encephalopathy treated by brain cooling

Introduction

MRI, proton magnetic resonance spectroscopy (¹H-MRS), and diffusion tensor imaging (DTI) have been shown to be of great prognostic value in term newborns with moderate–severe hypoxic-ischemic encephalopathy (HIE). Currently, no data are available on ¹H-MRS and DTI performed in the subacute phase after hypothermic treatment. The aim of the present study was to assess their prognostic value in newborns affected by moderate–severe HIE and treated with selective brain cooling (BC).

Methods

Twenty infants treated with BC underwent conventional MRI and ¹H-MRS at a mean (SD) age of 8.3 (2.8) days; 15 also underwent DTI. Peak area ratios of metabolites and DTI variables, namely mean diffusivity (MD), axial and radial diffusivity, and fractional anisotropy (FA), were calculated. Clinical outcome was monitored until 2 years of age.

Results

Adverse outcome was observed in 6/20 newborns. Both ¹H-MRS and DTI variables showed higher prognostic accuracy than conventional MRI. N-acetylaspartate/creatine at a basal ganglia localisation showed 100 % PPV and 93 % NPV for outcome. MD showed significantly decreased values in many regions of white and gray matter, axial diffusivity showed the best predictive value (PPV and NPV) in the genu of corpus callosum (100 and 91 %, respectively), and radial diffusivity was significantly decreased in fronto white matter (FWM) and fronto parietal (FP) WM. The decrement of FA showed the best AUC (0.94) in the FPWM.

Conclusion

Selective BC in HIE neonates does not affect the early and accurate prognostic value of ¹H-MRS and DTI, which outperform conventional MRI.     

Aortic stiffness is associated with white matter integrity in patients with type 1 diabetes

Objective

To assess the association between aortic pulse wave velocity (PWV) as a marker of arterial stiffness and diffusion tensor imaging of brain white matter integrity in patients with type 1 diabetes using advanced magnetic resonance imaging (MRI) technology.

Methods

Forty-one patients with type 1 diabetes (23 men, mean age 44?±?12 years, mean diabetes duration 24?±?13 years) were included. Aortic PWV was assessed using through-plane velocity-encoded MRI. Brain diffusion tensor imaging (DTI) measurements were performed on 3-T MRI. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were calculated for white and grey matter integrity. Pearson correlation and multivariable linear regression analyses including cardiovascular risk factors as covariates were assessed.

Results

Multivariable linear regression analyses revealed that aortic PWV is independently associated with white matter integrity FA (β?=??0.777, p?=?0.008) in patients with type 1 diabetes. This effect was independent of age, gender, mean arterial pressure, body mass index, smoking, duration of diabetes and glycated haemoglobin levels. Aortic PWV was not significantly related to grey matter integrity.

Conclusions

Our data suggest that aortic stiffness is independently associated with reduced white matter integrity in patients with type 1 diabetes.

Key Points

? Aortic stiffness is associated with brain injury. ? Aortic stiffness exposes small vessels to high pressure fluctuations and flow. ? Aortic stiffness is associated with microvascular brain injury in diabetes. ? This suggests a vascular contribution to early subtle microstructural deficits.     

Short-term evolution of spinal cord damage in multiple sclerosis: a diffusion tensor MRI study

Introduction

The potential of diffusion tensor imaging (DTI) to detect spinal cord abnormalities in patients with multiple sclerosis has already been demonstrated. The objective of this study was to apply DTI techniques to multiple sclerosis patients with a recently diagnosed spinal cord lesion, in order to demonstrate a correlation between variations of DTI parameters and clinical outcome, and to try to identify DTI parameters predictive of outcome.

Methods

A prospective single-centre study of patients with spinal cord relapse treated by intravenous steroid therapy was made. Patients were assessed clinically and by conventional MRI with DTI sequences at baseline and at 3?months.

Results

Sixteen patients were recruited. At 3?months, 12 patients were clinically improved. All but one patient had lower fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values than normal subjects in either inflammatory lesions or normal-appearing spinal cord. Patients who improved at 3?months presented a significant reduction in the radial diffusivity (p?=?0.05) in lesions during the follow-up period. They also had a significant reduction in the mean ADC (p?=?0.002), axial diffusivity (p?=?0.02), radial diffusivity (p?=?0.02) and a significant increase in FA values (p?=?0.02) in normal-appearing spinal cord. Patients in whom the American Spinal Injury Association sensory score improved at 3?months showed a significantly higher FA (p?=?0.009) and lower radial diffusivity (p?=?0.04) in inflammatory lesion at baseline compared to patients with no improvement.

Conclusion

DTI MRI detects more extensive abnormalities than conventional T2 MRI. A less marked decrease in FA value and more marked decreased in radial diffusivity inside the inflammatory lesion were associated with better outcome.     

Post-mortem cardiac diffusion tensor imaging: detection of myocardial infarction and remodeling of myofiber architecture

Objectives

To investigate the accuracy of post-mortem diffusion tensor imaging (DTI) for the detection of myocardial infarction (MI) and to demonstrate the feasibility of helix angle (HA) calculation to study remodelling of myofibre architecture.

Methods

Cardiac DTI was performed in 26 deceased subjects prior to autopsy for medicolegal reasons. Fractional anisotropy (FA) and mean diffusivity (MD) were determined. Accuracy was calculated on per-segment (AHA classification), per-territory, and per-patient basis, with pathology as reference standard. HAs were calculated and compared between healthy segments and those with MI.

Results

Autopsy demonstrated MI in 61/440 segments (13.9 %) in 12/26 deceased subjects. Healthy myocardial segments had significantly higher FA (p?p?p?p?=?0.01) with the covariate post-mortem time (p?p?p?>?0.05).

Conclusions

Post-mortem cardiac DTI enablesdifferentiation between healthy and infarcted myocardial segments by means of FA and MD. HA assessment allows for the demonstration of remodelling of myofibre architecture following chronic MI.

Key Points

? DTI enables post-mortem detection of myocardial infarction with good accuracy. ? A decrease in right-handed helical fibre indicates myofibre remodelling following chronic myocardial infarction. ? DTI allows for ruling out myocardial infarction by means of FA. ? Post-mortem DTI may represent a valuable screening tool in forensic investigations.     

Diagnostic performance of regional DTI-derived tensor metrics in glioblastoma multiforme: simultaneous evaluation of p, q, L, Cl, Cp, Cs, RA, RD, AD, mean diffusivity and fractional anisotropy

Objectives

Almost a dozen diffusion tensor-imaging (DTI) variables have been used to evaluate brain tumours with scarce information about their diagnostic ability. We aimed to perform a comprehensive evaluation of tensor metrics reported in the last decade.

Methods

Retrospective case control study performed in 14 patients with glioblastoma multiforme (GBM) and 28 controls. Conventional brain MR sequences and image postprocessing of DTI allowed the calculation of: MD, FA, p, q, L, Cl, Cp, Cs, RA, RD and AD, classified into five regions: normal appearance white matter (NAWM), immediate and distant oedema, enhancing rim and cystic cavity. ANOVA and AUROC analyses were performed.

Results

ANOVA depicted a significant difference among all metrics (p?<?0.05). RA had the highest performance in the NAWM and cystic cavity; immediate and distant zones of oedema were best diagnosed by RD and Cp respectively; q was the best biomarker of the enhancing rim zone; p?<?0.001 for all metrics.

Conclusions

FA and MD, accepted biomarkers of brain injury, were surpassed by other metrics. RA, together with Cs, Cl and CP, might be the new leaders in the evaluation of brain tumours. DTI tensor metrics depict different clinical applicability at each tumour region.

Key Points

? DTI-derived tensor metrics can characterise the regional impairment of intraaxial brain tumours. ? A performance evaluation of new diagnostic tests should follow the STARD initiative. ? Each tumour region in GBM is detected by a different tensor metric. ? FA and MD are not the best biomarkers of tumour infiltration. ? The diagnostic performance of some tensor metrics allows them to be used interchangeably.     

Evaluation of white matter damage in patients with Alzheimer’s disease and in patients with mild cognitive impairment by using diffusion tensor imaging

Purpose

The objective of this study was to evaluate white matter tissue damage in patients with Alzheimer’s disease (AD) and in patients with mild cognitive impairment (MCI) using diffusion tensor imaging (DTI).

Materials and methods

Forty-seven subjects were evaluated: 14 patients with AD, 15 with MCI and 18 healthy volunteers. All subjects were studied using conventional magnetic resonance imaging (MRI) and DTI (32 directions) with a 1.5 T magnet. Fractional anisotropy (FA) was measured in the following regions: frontal, occipital, parietal and temporal white matter and in the genu and splenium of the corpus callosum. The results were compared between the different groups and correlated with the Mini-Mental State Evaluation (MMSE) scores.

Results

A statistically significant difference was obtained between controls and MCI patients (p<0.007) and between controls and AD patients (p<0.05) with regard to FA of the white matter in the splenium. A statistically significant difference was obtained between controls and AD patients with regard to FA in the genu (p<0.016). Moreover, there was a statistically significant difference between controls and AD patients considering the genu (p<0.016) and the frontal white matter on the right side (p<0.024). The MMSE scores correlated with the FA values measured in the genu, the splenium and frontal white matter on the right side. No significant differences were identified between patients with AD and those with MCI.

Conclusions

DTI could be of value in the early detection of white-matter damage in patients with MCI and AD. The DTI values correlate with the neuropsychological tests.     

Does the use of hormonal contraceptives cause microstructural changes in cerebral white matter? Preliminary results of a DTI and tractography study

Objective

To evaluate the effect of monophasic combined oral contraceptive pill (COCP) and menstrual cycle phase in healthy young women on white matter (WM) organization using diffusion tensor imaging (DTI).

Methods

Thirty young women were included in the study; 15 women used COCP and 15 women had a natural cycle. All subjects underwent DTI magnetic resonance imaging during the follicular and luteal phase of their cycle, or in different COCP cycle phases. DTI parameters were obtained in different WM structures by performing diffusion tensor fibre tractography. Fractional anisotropy and mean diffusivity were calculated for different WM structures. Hormonal plasma concentrations were measured in peripheral venous blood samples and correlated with the DTI findings.

Results

We found a significant difference in mean diffusivity in the fornix between the COCP and the natural cycle group. Mean diffusivity values in the fornix were negatively correlated with luteinizing hormone and estradiol blood concentrations.

Conclusion

An important part in the limbic system, the fornix, regulates emotional processes. Differences in diffusion parameters in the fornix may contribute to behavioural alternations related to COCP use. This finding also suggests that the use of oral contraceptives needs to be taken into account when designing DTI group studies.

Key Points

? Diffusion tensor MRI offers new insights into brain white matter microstructure. ? The effects of oral hormonal contraception were examined in young women. ? Diffusion tensor images and hormone blood concentrations were evaluated. ? Women using hormonal contraception demonstrated higher mean diffusivity in the fornix. ? These changes may contribute to behavioural alternations related to contraception use.     

Feasibility of in vivo diffusion tensor imaging of articular cartilage with coverage of all cartilage regions

Objectives

To investigate the value of diffusion tensor imaging (DTI) of articular cartilage to differentiate healthy from osteoarthritis (OA) subjects in all cartilage regions.

Methods

DTI was acquired sagittally at 7 T in ten healthy and five OA (Kellgren-Lawrence grade 2) subjects with a line scan diffusion tensor sequence (LSDTI). Three healthy volunteers and two OA subjects were examined twice to assess the test-retest reproducibility. Averaged mean diffusivity (MD) and fractional anisotropy (FA) were calculated in each cartilage region (femoral trochlea, lateral and medial femoral condyles, patella, and lateral and medial tibia).

Results

The test-retest reproducibility was 2.9 % for MD and 5.6 % for FA. Averaged MD was significantly increased (+20 %, p?<?0.05) in the OA subjects in the lateral femoral condyle, lateral tibia and the femoral trochlea compartments. Averaged FA presented a trend of lower values in the OA subjects (-12 %), which was only significant for the lateral tibia.

Conclusions

In vivo DTI of articular cartilage with coverage of all cartilage regions using an LSDTI sequence is feasible, shows excellent reproducibility for MD and FA, and holds potential for the diagnosis of OA.

Key points

? DTI of articular cartilage is feasible at 7 T in all cartilage regions ? DTI of articular cartilage can potentially differentiate healthy and OA subjects     

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.

     

Relationship between cognitive impairment and white-matter alteration in Parkinson’s disease with dementia: tract-based spatial statistics and tract-specific analysis

Objectives

We investigated the relationship between white-matter alteration and cognitive status in Parkinson’s disease (PD) with and without dementia by using diffusion tensor imaging.

Methods

Twenty PD patients, 20 PDD (Parkinson’s disease with dementia) patients and 20 age-matched healthy controls underwent diffusion tensor imaging. The mean diffusivity and fractional anisotropy (FA) map of each patient group were compared with those of the control group by using tract-based spatial statistics. Tractography images of the genu of the corpus callosum fibre tracts were generated, and mean diffusivity and FA were measured.

Results

FA values in many major tracts were significantly lower in PDD patients than in control subjects; in the prefrontal white matter and the genu of the corpus callosum they were significantly lower in PDD patients than in PD patients. There was a significant correlation between the Mini-Mental State Examination (MMSE) scores and the FA values of the prefrontal white matter and the genu of the corpus callosum in patients with PD.

Conclusions

Our study shows a relationship between cognitive impairment and alteration of the prefrontal white matter and genu of the corpus callosum. These changes may be useful in assessing the onset of dementia in PD patients.

Key Points

? Dementia is a common and important non-motor sign of Parkinson’s disease (PD). ? The neuropathological basis of dementia in PD is not clear. ? DTI shows abnormalities in the prefrontal white matter in PD with dementia. ? Prefrontal white matter alteration may be useful biomarker of dementia in PD.     

Unraveling pathology in juvenile Alexander disease: serial quantitative MR imaging and spectroscopy of white matter

Introduction

Alexander disease is a rare disorder of the central nervous system with characteristic symmetric white matter abnormalities with frontal predominance on magnetic resonance (MR) images. Histopathology shows a lack of myelin in the affected white matter, variably interpreted as hypomyelination or demyelination. To increase our insight into the nature of the pathology leading to the MR imaging findings in Alexander disease, we applied serial MR imaging, spectroscopy, magnetization transfer (MT) imaging (MTI), and diffusion tensor imaging (DTI) in six patients with juvenile Alexander disease.

Methods

The MR imaging protocol comprised T1- and T2-weighted spin echo images and fluid-attenuated inversion recovery images. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), and MT ratio (MTR) maps were generated, and MR spectroscopy concentrations were quantified for several metabolites.

Results

MR imaging showed similar cerebral white matter abnormalities in all patients, with only minor increase on prolonged follow-up, despite sometimes serious clinical progression. MR spectroscopy showed highly elevated levels of myo-inositol, lactate, and choline-containing compounds and decreased total N-acetyl-aspartate and N-acetyl-aspartyl-glutamate levels in the abnormal white matter. High values of ADC were observed, and both FA and MTR were attenuated.

Conclusion

The sequential MR imaging findings in Alexander disease provide strong evidence against active demyelination as sole explanation for the underlying pathology. An alternative explanation for our spectroscopic, DTI, and MTI findings—which would suggest demyelination—could be hyperplasia and hypertrophy of astrocytes, as seen in low grade gliomas.     

Diffusion tensor imaging and tractography of the kidneys: assessment of chronic parenchymal diseases

Objective

To assess renal dysfunction in chronic kidney diseases using diffusion tensor imaging (DTI).

Methods

Forty-seven patients with impaired renal function (study group) and 17 patients without renal diseases (control group) were examined using DTI sequences. Cortical and medullary regions of interest (ROIs) were located to obtain the corresponding values of the apparent diffusion coefficient (ADC) and the fractional anisotropy (FA). The mean values of the ADC and FA, for each ROI site, were obtained in each group and were compared. Furthermore, the correlations between the diffusion parameters and the estimated glomerular filtration rate (eGFR) were determined.

Results

In both the normal and affected kidneys, we obtained the cortico-medullary difference of the ADC and the FA values. The FA value in the medulla was significantly lower (P?=?0.0149) in patients with renal function impairment as compared to patients with normal renal function. A direct correlation between DTI parameters and the eGFR was not found. Tractography visualised disruption of the regular arrangement of the tracts in patient with renal function alteration.

Conclusion

DTI could be a useful tool in the evaluation of chronic kidney disease and, in particular, the medullary FA value seems to be the main parameter for assessing renal damage.

Key Points

? Magnetic resonance diffusion tensor imaging (MRDTI) provides new information about renal problems. ? DTI allows non-invasive repeatable evaluation of the renal parenchyma, without contrast media. ? DTI could become useful in the management of chronic parenchymal disease. ? DTI seems more appropriate for renal evaluation than diffusion-weighted imaging.     

A preliminary diffusional kurtosis imaging study of Parkinson disease: comparison with conventional diffusion tensor imaging

Introduction

Diffusional kurtosis imaging (DKI) is a more sensitive technique than conventional diffusion tensor imaging (DTI) for assessing tissue microstructure. In particular, it quantifies the microstructural integrity of white matter, even in the presence of crossing fibers. The aim of this preliminary study was to compare how DKI and DTI show white matter alterations in Parkinson disease (PD).

Methods

DKI scans were obtained with a 3-T magnetic resonance imager from 12 patients with PD and 10 healthy controls matched by age and sex. Tract-based spatial statistics were used to compare the mean kurtosis (MK), mean diffusivity (MD), and fractional anisotropy (FA) maps of the PD patient group and the control group. In addition, a region-of-interest analysis was performed for the area of the posterior corona radiata and superior longitudinal fasciculus (SLF) fiber crossing.

Results

FA values in the frontal white matter were significantly lower in PD patients than in healthy controls. Reductions in MK occurred more extensively throughout the brain: in addition to frontal white matter, MK was lower in the parietal, occipital, and right temporal white matter. The MK value of the area of the posterior corona radiata and SLF fiber crossing was also lower in the PD group.

Conclusion

DKI detects changes in the cerebral white matter of PD patients more sensitively than conventional DTI. In addition, DKI is useful for evaluating crossing fibers. By providing a sensitive index of brain pathology in PD, DKI may enable improved monitoring of disease progression.     

Peripheral nerve diffusion tensor imaging (DTI): normal values and demographic determinants in a cohort of 60 healthy individuals

Objective

To identify demographic determinants of peripheral nerve diffusion tensor imaging (DTI) and to establish normal values for fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD).

Methods

Sixty subjects were examined at 3 Tesla by single-shot DTI. FA, AD, RD, and MD were collected for the sciatic, tibial, median, ulnar, and radial nerve and were correlated with demographic variables.

Results

Mean FA of all nerves declined with increasing age (r = ?0.77), which could be explained by RD increasing (r = 0.56) and AD declining (r = ?0.40) with age. Moreover, FA was inversely associated with height (r = ?0.28), weight (r = ?0.38) and BMI (r = ?0.35). Although FA tended to be lower in men than women (p = 0.052), this difference became completely negligible after adjustment to body weight. A multiple linear regression model for FA was calculated with age and weight as predictors (defined by backward variable selection), yielding an R ² = 0.71 and providing a correction formula to adjust FA for age and weight.

Conclusion

Peripheral nerve DTI parameters depend on demographic variables. The most important determinants age and weight should be considered in all studies employing peripheral nerve DTI.

Key points

? Peripheral nerve diffusion tensor imaging (DTI) parameters depend on demographic variables. ? Fractional anisotropy (FA) declines with increasing age and weight. ? Gender does not systematically affect peripheral nerve DTI. ? The formula presented here allows adjustment of FA for demographic variables.

     

Quantitative 3-T diffusion tensor imaging in detecting optic nerve degeneration in patients with glaucoma: association with retinal nerve fiber layer thickness and clinical severity

Introduction

To investigate the association of quantitative 3-T diffusion tensor imaging (DTI) with retinal nerve fiber layer (RNFL) thickness measured by optical coherence tomography (OCT) and clinical severity in detecting optic nerve degeneration in patients with primary closed-angle glaucoma.

Methods

Twenty three patients (42 eyes; 9 men, 14 women) with primary closed-angle glaucoma and 20 healthy controls were enrolled in this study. Both DTI and OCT were performed on the optic nerves of all subjects. The mean diffusivity (MD), fractional anisotropy (FA), and eigenvalue maps were obtained for quantitative analysis. RNFL thickness and quantitative electrophysiology were also performed on all subjects. The association of quantitative DTI with RNFL thickness and glaucoma stage was analyzed.

Results

Compared with control nerves, the FA, λ_‖, and λ_⊥ values, and RNFL thickness in affected nerves decreased, while MD increased in patients with primary glaucoma (p?<?0.05). There was a significant correlation between FA, MD, λ_‖, and λ_⊥ and the mean RNFL thickness (P?<?0.01). The mean FA and λ_⊥ values derived with DT MR imaging correlated well with glaucoma stage (P?<?0.05), but the mean MD and λ_‖ values did not correlate with glaucoma stage (P?>?0.05).

Conclusion

DTI measurement could detect abnormality of the optic nerve in patients with glaucoma and may serve as a biomarker of disease severity.     

3-T MRI with diffusion tensor imaging and tractography of the median nerve

Objective

To apply diffusion tensor imaging (DTI) and tractography to the median nerve by use of a 3-T MRI device in order to demonstrate potential differences in diffusion parameters between healthy subjects and patients with carpal tunnel syndrome (CTS).

Methods

The median nerve of 15 patients and 20 healthy volunteers was examined in two sequences: DTI and a high-resolution T1-weighted sequence. Mean fractional anisotropy (FA) and mean apparent diffusion coefficient (ADC) were measured based on tractography findings. Mean FA was significantly lower in CTS patients (P?=?0.01) whereas no significant difference was found in mean ADC. Focal measurements of FA and ADC were also obtained at three locations along the course of the median nerve.

Results

We observed a highly significant difference (P?<?0.0001) between FA measured at the proximal carpus and FA measured at the distal carpus in healthy subjects and CTS patients. Focal FA values along the median nerve showed an opposite trend in the two groups: in healthy subjects FA tended to increase (P?<?0.05) whereas in subjects with CTS it tended to decrease (P?=?0.0001). We defined a threshold value of ?0.058 (FA3-FA1) that was sensitive and specific for nerve compression.

Conclusion

DTI and tractography can detect chronic nerve compression.

Key Points

? Diffusion tensor magnetic resonance imaging offers new information about carpal tunnel syndrome. ? Diffusion tensor MRI of the median nerve provides some functional data. ? Mean fractional anisotropy (FA) was lower in patients with CTS than volunteers. ? There was no significant difference in ADC values between patients and volunteers. ? Fractional anisotropy seems a sensitive and specific predictor of chronic nerve compression.     

Diffusion tensor imaging of peripheral nerve in patients with chronic inflammatory demyelinating polyradiculoneuropathy: a feasibility study

Introduction

The purpose of this study was to assess the clinical feasibility of diffusion tensor imaging (DTI) for the evaluation of peripheral nerves in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).

Methods

Using a 3-T magnetic resonance imaging scanner, we obtained DTI scans of the tibial nerves of 10 CIDP patients and 10 sex- and age-matched healthy volunteers. We prepared fractional anisotropy (FA) maps, measured the FA values of tibial nerves, and compared these values in the two study groups. In nine patients, we also performed tibial nerve conduction studies and analyzed the correlation between the FA values and parameters of the nerve conduction study.

Results

The tibial nerve FA values in CIDP patients (median 0.401, range 0.312?C0.510) were significantly lower than those in healthy volunteers (median 0.530, range 0.469?C0.647) (Mann?CWhitney test, p?<?0.01). They were significantly correlated with the amplitude of action potential (Spearman correlation coefficient, p?=?0.04, r?=?0.86) but not with nerve conduction velocity (p?=?0.79, r?=?0.11).

Conclusion

Our preliminary data suggest that the noninvasive DTI assessment of peripheral nerves may provide useful information in patients with CIDP.     

MR imaging and differentiation of cerebral fat embolism syndrome from diffuse axonal injury: application of diffusion tensor imaging

Introduction

Cerebral fat embolism syndrome (CFES) mimics diffuse axonal injury (DAI) on MRI with vasogenic edema, cytotoxic edema, and micro-hemorrhages, making specific diagnosis a challenge. The objective of our study is to determine and compare the diagnostic utility of the conventional MRI and DTI in differentiating cerebral fat embolism syndrome from diffuse axonal injury.

Methods

This retrospective study was performed after recruiting 11 patients with severe CFES and ten patients with severe DAI. Three trauma radiologists analyzed conventional MR images to determine the presence or absence of CFES and DAI. DTI analysis of the whole-brain white matter was performed to obtain the directional diffusivities. The results were correlated with clinical diagnosis to determine the diagnostic utility of conventional MRI and DTI.

Results

The sensitivity, specificity, and accuracy of conventional MRI in diagnosing CFES, obtained from the pooled data were 76, 85, and 80 %, respectively. Mean radial diffusivity (RD) was significantly higher and the mean fractional anisotropy (FA) was lower in CFES and differentiated subjects with CFES from the DAI group. Area under the receiver operating characteristic (ROC) curve for conventional MRI was 0.82, and for the differentiating DTI parameters the values were 0.75 (RD) and 0.86 (FA), respectively.

Conclusions

There is no significant difference between diagnostic performance of DTI and conventional MRI in CFES, but a difference in directional diffusivities was clearly identified between CFES and DAI.