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PubMed2003

Parametric and non-parametric statistical analysis of DT-MRI data.

In this work parametric and non-parametric statistical methods are proposed to analyze Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) data. A Multivariate Normal Distribution is proposed as a parametric statistical model of diffusion tensor data when magnitude MR images contain no artifacts other than Johnson noise. We test this model using Monte Carlo (MC) simulations of DT-MRI experiments. The non-parametric approach proposed here is an implementation of bootstrap methodology that we call the DT-MRI bootstrap. It is used to estimate an empirical probability distribution of experimental DT-MRI data, and to perform hypothesis tests on them. The DT-MRI bootstrap is also used to obtain various statistics of DT-MRI parameters within a single voxel, and within a region of interest (ROI); we also use the bootstrap to study the intrinsic variability of these parameters in the ROI, independent of background noise. We evaluate the DT-MRI bootstrap using MC simulations and apply it to DT-MRI data acquired on human brain in vivo, and on a phantom with uniform diffusion properties.

Artifacts↗
PubMedDate not supplied

Portal blood flow in the presence or absence of diffuse liver disease: measurement by phase contrast MR imaging.

BACKGROUND: In patients with diffuse liver disease, the portal flow dynamics change markedly in accordance with disease progression and would provide a useful index of progression of stage. METHODS: Portal blood flow (PBF) was measured by phase contrast magnetic resonance imaging (MRI) in 21 patients with diffuse liver disease and 20 healthy volunteers. The MRI method was validated by a flow phantom study. The mean PBF could be measured in 6.8 min without breath-holding. RESULTS: Doppler ultrasound measurements of PBF volume were obtained reproducibly in all the healthy volunteers and were shown to correlate with the MRI values (Doppler: 12.5 +/- 3.2 cm3/s, MRI: 12.0 +/- 3.3 cm3/s; mean +/- SD). The PBF volume of patients with chronic hepatitis showed no significant difference from that of the healthy volunteers. In patients with liver cirrhosis, the PBF volume ranged from 5.01 to 32.3 cm3/s. A significant increase in PBF volume was caused in one patient by massive intrahepatic shunting and a significant decrease was caused in two patients by massive extrahepatic shunting. CONCLUSIONS: The measurement of PBF by phase contrast MRI is clinically useful in predicting intrahepatic or extrahepatic shunting in patients with liver cirrhosis, and may be of value in detecting the progression of stage in diffuse liver diseases.

Adult↗
PubMed2006

Infiltrative MRI pattern and incomplete initial surgery compromise local control of myxofibrosarcoma.

UNLABELLED: Myxofibrosarcoma (MFS) has a high local failure rate of up to 79%. We conducted a retrospective analysis on all patients with the diagnosis of myxofibrosarcoma seen between 1990 and 2004 to assess whether improved imaging with MRI reduced local recurrence, increased survival, and whether radiotherapy following resection influenced outcome. Twenty-one patients were treated for MFS with a median followup of 52 months (range, 18-122). All patients were surgically treated, with 19 receiving limb-sparing surgery. All patients with high grade disease, positive margins, or a pre-referral procedure received radiation therapy. The local recurrence rate was 57% for patients with a prior outside procedure (8 of 14), while patients with no prior surgery had a rate of 14% (1 of 7). Prior marginal excision and diffuse fascial spread on MRI predicted an increased local recurrence rate. The disease-free survival at 5 years was 43% (SE, 22%) for low-grade disease and 39% (SE, 18%) for high- grade disease. Magnetic resonance imaging observations suggest a unique pattern of diffuse spread along fascial planes that could be responsible for the high local recurrence. Radiation did not compensate for positive margins, nor did it reduce recurrence after negative margins. LEVEL OF EVIDENCE: Therapeutic study, level IV (case series).

Aged↗
PubMed2000

The relationship between the apparent diffusion coefficient measured by magnetic resonance imaging, anoxic depolarization, and glutamate efflux during experimental cerebral ischemia.

A reduction in the apparent diffusion coefficient (ADC) of water measured by magnetic resonance imaging (MRI) has been shown to occur early after cerebrovascular occlusion. This change may be a useful indicator of brain tissue adversely affected by inadequate blood supply. The objective of this study was to test the hypothesis that loss of membrane ion homeostasis and depolarization can occur simultaneously with the drop in ADC. Also investigated was whether elevation of extracellular glutamate ([GLU]e) would occur before ADC changes. High-speed MRI of the trace of the diffusion tensor (15-second time resolution) was combined with simultaneous recording of the extracellular direct current (DC) potential and on-line [GLU]e from the striatum of the anesthetized rat. After a control period, data were acquired during remote middle cerebral artery occlusion for 60 minutes, followed by 30 minutes of reperfusion, and cardiac arrest-induced global ischemia. After either focal or global ischemia, the ADC was reduced by 10 to 25% before anoxic depolarization occurred. After either insult, the time for half the maximum change in ADC was significantly shorter than the corresponding DC potential parameter (P < 0.05). The [GLU]e remained at low levels during the entire period of varying ADC and DC potential and did not peak until much later after either ischemic insult. This study demonstrates that ADC changes can occur before membrane depolarization and that high [GLU]e has no involvement in the early rapid ADC decrease.

Animals↗
PubMed1999

[Radiologic follow-up after breast-conserving surgery: value of MRI examination of the breast].

The aim of the study was to establish an objective method for evaluation the extent, topography and quantity of skin and soft tissue side effects after tele- and/or brachyradiotherapy of the conserved breast and to compare the sequales of different radiation methods. 26 patients operated on for T1-2 N0-1 breast cancer underwent the following kinds of postoperative radiotherapy: 1. 46-50 Gy whole breast teletherapy + 10-16 Gy electron boost (5 patients), 2. 46-50 Gy teletherapy + 10-15 Gy HDR brachytherapy boost (12 patients), 3. 46-50 Gy teletherapy (6 patients), 4. 36,4 Gy sole HDR brachytherapy of the tumour bed (5 patients). The postirradiation side effects were examined by MRI, mammogram, US and physical examination, as well. MRI was performed on a 0.5 T, double breast coil, with SE-T1, SE-T2 and 3D-GE sequences. The findings of MRI and mammography were compared to physically detectable side effects using the RTOG/EORTC late radiation morbidity scoring scheme. US is useful in the measurement of skin thickening and in the diagnosis of fat necrosis. Mammography and physical examination are very subjective and low specificity methods to evaluate postirradiation side effects. MRI is a suitable and more objective method to detect the real extent and quantity of skin thickening and fibrosis. The incidence of > or = G2 side effects of skin and breast parenchyma were 64.5 and 32.2%, respectively. The differences between the side effects of whole breast irradiation and sole brachytherapy of the tumour bed are also clearly demonstrated. Brachytherapy alone is feasible without compromising cosmetic results. The authors established the MRI criteria for categorization the extent and grade of skin thickening and fibrosis (focal vs diffuse, grade 1-4). Breast MRI is an objective tool for assisting to the evaluation of the side effects of postoperative radiotherapy.

Brachytherapy↗
PubMedDate not supplied

Diffusion-weighted MR imaging in the evaluation of renal infection: preliminary results.

Diffusion-weighted (DW) magnetic resonance imaging (MRI) has already gained status in the neuroradiological MRI approach of a patient suffering from a variety of neurological diseases. The clinical application of DW MRI in the evaluation of renal disease is not standard. This manuscript describes preliminary results of the application of DW imaging in renal infection to aid differential diagnosis and/or lesion detection in clinical MRI. Three patients with acute pyelonephritis and two patients with renal abscess (one with xanthogranulomatous pyelonephritis, the other with a solitary pyogenic renal abscess) were examined with MRI. Areas of acute pyelonephritis and abscedation have restricted proton diffusion and are demonstrated on the DW images. Refinement of the technique, in-depth investigation of the pathological background of the MR findings and evaluation of its true clinical value need further investigation. This manuscripts shows preliminary findings of DW imaging in patients with renal infectious disease.

Abscess↗
PubMed2003

Imaging of Alzheimer's disease.

Imaging is widely used in the evaluation of Alzheimer's disease (AD). In addition to imaging's traditional role of aiding in the exclusion of diseases that may be confused with AD, structural and functional imaging are being explored for potential use in the early detection of AD and as surrogate markers of treatment outcome. Volumetric measurements of the hippocampal and entorhinal regions using modern magnetic resonance imaging (MRI) and computed tomography are most widely studied in the discrimination of AD from nondemented aging and other dementias. Other imaging modalities include positron emission tomography and single-photon-emission computed tomography, which evaluate global and regional disturbances of blood flow and metabolism, and proton spectroscopy, which assesses neuronal degeneration and loss as marked by the presence of abnormal metabolites. Diffusion tensor and functional MRI, which examine white matter changes and brain-behavior relationships, are more recent techniques that contribute to the burgeoning application of imaging techniques to dementing illnesses and are notably improving our understanding of the pathophysiology of AD.

Alzheimer Disease↗
PubMed1992

Angiographically occult brainstem vascular malformation: a longitudinal comparison of magnetic resonance imaging (MRI) and multimodal evoked potential (EP) recordings.

Over a period of several years, a patient with angiographically occult vascular malformation (AOVM) involving the brainstem was longitudinally studied by means of serial Magnetic Resonance Imaging (MRI) and multimodal Evoked Potential (EP) recordings (visual-VEP, brainstem auditory-BAEP, somatosensory--SEP--by stimulating median and peroneal nerves). MRI did contribute to an accurate definition of AOVM features. In particular, it was able to follow over time the AOVM size, and to discriminate between recent and old bleedings. Multimodal EP recordings displayed different pathological BAEP and peroneal SEP values, which documented a transient segmental brainstem involvement (related to the presence of hemorrhage), along with persistent and probably irreversible signs of diffuse brainstem dysfunction. Thus, MRI and EP assessment is useful in monitoring the clinical course of brainstem occult vascular malformations.

Brain Neoplasms↗
PubMed1995

Lesion of dentatothalamic pathways in severe post-traumatic tremor.

The present study investigates evidence of dentatothalamic pathway lesions in nineteen patients with severe kinetic post-traumatic tremor respectively by magnetic resonance imaging (MRI). Kinetic tremor is thought to be characteristic of lesions of the cerebellar outflow. While this hypothesis is supported by experimental data, neuropathological and neuroradiological findings have been limited. The appendicular tremors were unilateral in 13 patients and bilateral in 6, accounting for 25 instances of tremor. The tremor developed after severe head trauma in 18 patients. These patients had evidence of diffuse axonal injury on MRI. Postural and kinetic tremor was present in all patients, and was accompanied by tremor also present at rest in 14 instances. Multiplanar MRI studies were performed on a high-field MRI system operating at 2.0 T in 13 patients and on intermediate-field strength MRI systems in 6 patients according to a standardized protocol. To detect small deposits of hemosiderin after post-traumatic lesions, the protocol included a heavily T2-weighted spin-echo pulse sequence. Lesions of the dentatothalamic pathways were found in 22 instances. The lesions were classified into different types of according to their distribution. A lesion of the dentate nucleus ipsilateral to the tremor (type 1) was found in one instance (4%), lesions involving the ipsilateral predecussational dentatothalamic pathway (type II and III) were found in 14 instances (56%), and lesions involving the contralateral post-decussational course (type IV) in 7 instances (28%). One patient with a mild head trauma had a lesion of the contralateral thalamus. The lesions appeared as hypointense, hyperintense or mixed. Two of three patients with a parkinsonian-like rest tremor had type IV lesions involving the substantia nigra. The nosological concepts of tremors are discussed. 'Midbrain' tremor may have distinct pathoanatomical lesion sites.

Adult↗
PubMed2008

Corpus callosal connection mapping using cortical gray matter parcellation and DT-MRI.

Population maps of the corpus callosum (CC) and cortical lobe connections were generated by combining cortical gray matter parcellation with the diffusion tensor fiber tractography of individual subjects. This method is based on the fact that the cortical lobes of both hemispheres are interconnected by the corpus callosal fibers. T1-weighted structural MRIs and diffusion tensor MRIs (DT-MRI) of 22 right-handed, healthy subjects were used. Forty-seven cortical parcellations in the dorsal prefrontal cortex, ventral prefrontal cortex, sensory-motor cortex, parietal cortex, temporal cortex, and occipital cortex were semi-automatically derived from structural MRIs, registered to DT-MRI, and used to identify callosal fibers. The probabilistic connections to each cortex were mapped on entire mid-sagittal CC voxels that had anatomical homology between subjects as determined by spatial registration. According to the population maps of the callosal connections, the ventral prefrontal cortex and parts of the dorsal prefrontal cortex both project fibers through the genu and rostrum. The CC regions through which the superior frontal cortex passes extend into the posterior body. Fibers arising from the parietal lobe and occipital lobe run mainly through the splenium, while fibers arising from the sensory-motor cortex pass through the isthmus. In general, dorsal or medial cortical lobes project fibers through the dorsal region of the CC, while lateral cortical lobes project fibers through the ventral region of the CC. The probabilistic subdivision of the CC by connecting cortical gray matter provides a more precise understanding of the CC.

Brain Mapping↗
PubMed2003

Evidence for cortical functional changes in patients with migraine and white matter abnormalities on conventional and diffusion tensor magnetic resonance imaging.

BACKGROUND: In this study, we used functional MRI (fMRI) to investigate the pattern of cortical activations after a simple motor task in patients with migraine and white matter (WM) abnormalities on conventional MRI scans of the brain. We also investigated whether the extent of brain activations was correlated with WM structural pathology measured using diffusion tensor (DT) MRI. METHODS: From 15 right-handed patients with migraine and 15 sex- and age-matched, right-handed healthy volunteers, we obtained the following: (1) fMRI (repetitive flexion-extension of the last 4 fingers of the right hand), (2) dual-echo turbo spin echo scans, and (3) pulsed-gradient spin-echo echo-planar sequence to calculate DT-MRI maps. fMRI analysis was performed using SPM99 and cluster detection. We measured the volume, the average mean diffusivity (), and the average fractional anisotropy of all lesions seen on the dual-echo scans. histograms of the normal-appearing WM were also produced. RESULTS: Compared with healthy volunteers, migraine patients had a larger relative activation of the contralateral primary sensorimotor cortex (P=0.01) and a rostral displacement of the supplementary motor area (P=0.03). The shapes of the curves reflecting the time course for fMRI signal intensity changes were similar between migraine patients and controls for all of the cortical areas we studied. Compared with healthy subjects, migraine patients had significantly lower histogram peak height of the normal-appearing WM histogram (P=0.02), which was found to be correlated with the extent of displacement of the supplementary motor area (r=-0.80, P<0.001). CONCLUSIONS: This study suggests that functional cortical changes occur in patients with migraine and brain MRI abnormalities and that they might be secondary to the extent of subcortical structural damage.

Adolescent↗
PubMed1998

Magnetic resonance imaging in multiple sclerosis.

Conventional magnetic resonance imaging (MRI) techniques acquire signal mainly from differences in relaxation properties and density of free water protons. Thus, the sensitivity in depicting lesions is high but pathological specificity is poor. Efforts are being made to increase the diagnostic power of MRI; better correlation with the clinical presentation and the use of better MRI criteria have increased the specificity of the conventional T2 sequences. New sequences, such as fast spin echo, turbo spin echo (TSE) or those derived from inversion recovery (fluid attenuated inversion recovery), have improved the detection of lesions. Acute phase monitoring focuses on changes in disease activity (new, recurring, enlarging, gadolinium-enhancing lesions) and chronic phase monitoring allows appreciation of the burden of the disease. However, MRI is considered as a secondary outcome measure in phase III trials because of insufficient correlation with the clinical disability. There is a continuing search for techniques that correlate better with clinical measures of the disease, such as the quantification of 'black holes' on T1-weighted images or the cerebral and spinal atrophy. The basic aspects of the pathological lesions in multiple sclerosis such as oedema, membrane disruption, demyelination, gliosis, cellular infiltration and axonal loss, can be studied more precisely by the new magnetic resonance techniques, which should better describe the actual clinical impact of the destructive process. In the past year the importance of axonal loss has simultaneously been confirmed by magnetic resonance spectroscopy and pathological findings. However, magnetization transfer imaging, magnetic resonance diffusion imaging and functional MRI are under intensive investigation for a better analysis of these different factors that impact on the reversibility of the patients disability.

Diffusion↗
PubMedDate not supplied

Diffusion tensor imaging and its application to neuropsychiatric disorders.

Magnetic resonance diffusion tensor imaging (DTI) is a new technique that can be used to visualize and measure the diffusion of water in brain tissue; it is particularly useful for evaluating white matter abnormalities. In this paper, we review research studies that have applied DTI for the purpose of understanding neuropsychiatric disorders. We begin with a discussion of the principles involved in DTI, followed by a historical overview of magnetic resonance diffusion-weighted imaging and DTI and a brief description of several different methods of image acquisition and quantitative analysis. We then review the application of this technique to clinical populations. We include all studies published in English from January 1996 through March 2002 on this topic, located by searching PubMed and Medline on the key words "diffusion tensor imaging" and "MRI." Finally, we consider potential future uses of DTI, including fiber tracking and surgical planning and follow-up.

Anisotropy↗
PubMed2005

Magnetic resonance imaging: implication in acute ischemic stroke management.

Multimodality magnetic resonance imaging (MRI) techniques, including diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI), fluid-attenuated inversion recovery (FLAIR), T2 susceptibility imaging, and magnetic resonance angiography (MRA), quickly provide accurate information about ischemic penumbra (DWI/PWI mismatch), tissue perfusion, and vascular localization in acute stroke setting. These techniques help physicians to select the proper candidates for thrombolysis and/or neuroprotective treatment to salvage tissue at risk (mismatch) and monitor acute stroke patients after treatment. Recent and ongoing trials demonstrate the benefit of treating acute stroke patients depending on tissue at risk of infarction rather than timing of onset. These techniques will extend timing to salvage ischemic brain tissue beyond the 3-hour window. MRI is a powerful tool for managing acute stroke patients and helps elucidate the pathophysiology of cerebral ischemia in a given patient.

Acute Disease↗
PubMed2002

[Rosai-Dorfman disease accompanying hypertrophic cranial pachymeningitis with an early symptom of right peripheral facial palsy].

We experienced a rare case of sinus histiocytosis with massive lymphoadenopathy (Rosai-Dorfman disease) accompanying hypertrophic cranial pachymeningitis. The patient is a 64-year-old woman with an early symptom of rt. peripheral facial palsy. She had a 4-month history of headache with a 5-week history of numbness in the rt. supraorbital nerve area, and lost her weight by 10 kg in 2 months. She developed rt. trochlea nerve palsy and numbness in the lt. mandibular nerve area. Laboratory findings showed that ALP, LDH and CRP were higher than normal. Of CT, MRI and MRA, the images of her head were normal. However, the Gd-enhanced MRI only showed a diffuse pachymeningeal enhancement. After about 3 months from the onset of rt. peripheral facial palsy, she died of DIC of unknown etiology. As a result of examinations in anatomical pathology, she was diagnosed as having sinus histiocytosis with massive lymphoadenopathy (Rosai-Dorfman disease). There were a large number of histiocytes on the pachymeninx. These findings suggest that hypertrophic cranial pachymeningitis caused multiple cranial neuropathy. We emphasize that use of Gd-enhanced MRI in the early stage is important for diagnosis.

Facial Paralysis↗
PubMed1991

Magnetic resonance imaging of the adrenal gland in women with late-onset adrenal hyperplasia.

To determine the presence of structural abnormalities of the adrenal in late-onset adrenal hyperplasia, four consecutive patients were studied by MRI before beginning glucocorticoid replacement therapy. Three women were diagnosed as 21-hydroxylase deficient late-onset adrenal hyperplasia by a 17-OHP level greater than 1,000 ng/dL 30 minutes after acute adrenal stimulation, and one patient was diagnosed as 11-hydroxylase deficient late-onset adrenal hyperplasia when her 11-deoxycortisol level was threefold the upper 95th percentile of normal. Two patients with 21-hydroxylase deficient late-onset adrenal hyperplasia had normal adrenal glands on MRI. Another 21-hydroxylase deficient late-onset adrenal hyperplasia patient was noted to have a 2.5 x 3.3-cm left adrenal nodule, which had been documented some 4 years earlier on CT scan and had not changed in size during that interval. This patient was 40 years of age when the diagnosis of late-onset adrenal hyperplasia was established. The patient with 11-hydroxylase deficient late-onset adrenal hyperplasia demonstrated a diffuse enlargement of the left adrenal gland consistent with hyperplasia, with no focal lesions. In conclusion, although patients with late-onset adrenal hyperplasia may often demonstrate nodular or diffuse adrenocortical hyperplasia on MRI, not all patients with endocrinologically evident disease demonstrate such abnormalities, consistent with a lesser degree of ACTH stimulation compared with women with classical congenital adrenal hyperplasia.

Adrenal Glands↗
PubMed2003

[Diagnostic imaging and differential diagnosis of pathological processes of the sinus cavernosus].

To describe the different imaging modalities for the evaluation of pathological changes in the cavernous sinus as well as to compile criteria for differential diagnosis. Imaging of the cavernous sinus comprises the primary use of tomographic modalities such as CT or MRI. The continuing development of multislice-CT (MSCT) allows the depiction of bony structures of the cavernous sinus with a high resolution.Secondary reconstructions of the acquired data set allow a reliable evaluation especially of the bony topography including the foraminae of nerves and vessels. Uni- or bilateral structures can be visualized using contrast-enhanced CT.CT-angiography is capable of demonstrating the course of the internal carotid artery and its involvement in pathologies of the cavernous sinus, this recent achievement has only been made available by use of the current short scanning times. Contrast-enhanced MRI in axial and coronal orientation, optionally using fat saturation techniques as well as arterial and venous MRI-angiography (MRA) are used to depict the soft parts of the cavernous sinus. Care must be taken to cover all topographic detail including different signal intensities, as multiple inborn, neoplastic, infectious or traumatic changes can be present hampering the radiologic diagnosis of the cavernous sinus. Uni- and bilateral infiltration of the cavernous sinus as well as vascular involvement represent additional criteria leading to the differential diagnosis. The advent of dynamic sequences as well as diffusion and perfusion weighted MRI have broadened the spectrum of diagnostic modalities. Digital subtraction angiography as an invasive technique is used during therapeutic procedures such as the local treatment of aneurysms or carotid-cavernous fistulas.

Carotid Artery, Internal↗
PubMed2003

Correlation between brain reorganization, ischemic damage, and neurologic status after transient focal cerebral ischemia in rats: a functional magnetic resonance imaging study.

The pattern and role of brain plasticity in stroke recovery has been incompletely characterized. Both ipsilesional and contralesional changes have been described, but it remains unclear how these relate to functional recovery. Our goal was to correlate brain activation patterns with tissue damage, hemodynamics, and neurologic status after temporary stroke, using functional magnetic resonance imaging (fMRI). Transverse relaxation time (T2)-weighted, diffusion-weighted, and perfusion MRI were performed at days 1 (n = 7), 3 (n = 7), and 14 (n = 7) after 2 hr unilateral middle cerebral artery occlusion in rats. Functional activation and cerebrovascular reactivity maps were generated from contrast-enhanced fMRI during forelimb stimulation and hypercapnia, respectively. Before MRI, rats were examined neurologically. We detected loss of activation responses in the ipsilesional sensorimotor cortex, which was related to T2 lesion size (r = -0.858 on day 3, r = -0.979 on day 14; p < 0.05). Significant activation responses in the contralesional hemisphere were detected at days 1 and 3. The degree of shift in balance of activation between the ipsilesional and contralesional hemispheres, characterized by the laterality index, was linked to the T2 and apparent diffusion coefficient in the ipsilesional contralesional forelimb region of the primary somatosensory cortex and primary motor cortex at day 1 (r = -0.807 and 0.782, respectively; p < 0.05) and day 14 (r = -0.898 and -0.970, respectively; p < 0.05). There was no correlation between activation parameters and perfusion status or cerebrovascular reactivity. Finally, we found that the laterality index and neurologic status changed in parallel over time after stroke, so that when all time points were grouped together, neurologic status was inversely correlated with the laterality index (r = -0.571; p = 0.016). This study suggests that the degree of shift of activation balance toward the contralesional hemisphere early after stroke increases with the extent of tissue injury and that functional recovery is associated mainly with preservation or restoration of activation in the ipsilesional hemisphere.

Animals↗