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Magnetic resonance imaging stereotaxy: recognition and utilization of the commissures.

Magnetic Resonance Imaging (MRI) offers a non-invasive method to visualize the intracerebral structures. Coupled to a compatible stereotactic frame and software, MRI can be used to determine the coordinates of intracranial targets. Coordinates of the anterior commissure, posterior commissure, targets and intercommissural distance were obtained from positive contrast ventriculography and by MRI in 6 patients undergoing stereotactic localization prior to the implantation of stimulating thalamic electrodes for pain control. The correlation of coordinates and measurements obtained with ventriculography and MRI is +/- 1 mm in most measurements, but up to 3 mm in 2 cases. Magnetic resonance stereotaxy allows non-invasive and precise localization of intracerebral targets, but does not yet allow its routine use with confidence. Further understanding of distortion and artifacts and corrections of these is mandatory.

Brain↗

Non-invasive, quantitative assessment of the anatomical phenotype of corticotropin-releasing factor-overexpressing mice by MRI.

High resolution magnetic resonance imaging (MRI) was applied to quantify alterations in thymus and adrenal volumes, as well as body fat in genetically engineered corticotropin-releasing factor (CRF)-overexpressing mice. When compared to the organs in age-matched wild-type animals, the adrenals in CRF-overexpressing male mice were significantly enlarged and the thymus volume in females was significantly smaller. The fat content was significantly larger in CRF-overexpressing mice. The anatomical alterations observed in the MRI studies were in perfect line with post-mortem data (weights of organs). Furthermore, the observed interstrain differences are in agreement with recently published data on (i) the effect of continuous, intraventricular infusion of CRF in rats and (ii) the presence of atrophic adrenals in CRF-knockout mice. The present studies demonstrate that MRI can provide reliable measures of relatively small structures such as the adrenal glands and the thymus in mice. This makes MRI an attractive, non-terminal tool to monitor in laboratory animals, including transgenic mice, the consequence of continuous stress on relevant organs.

Adipose Tissue↗

Imaging the neocortex in epilepsy with double inversion recovery imaging.

The neocortices of 10 patients with partial seizures and acquired lesions, 14 patients with malformations of cortical development (MCD) and 33 patients with partial seizures and normal conventional MRI were quantitatively evaluated using whole brain double inversion recovery imaging (DIR) and Statistical Parametric Mapping (SPM). Compared to a group of 30 control subjects, DIR and objective voxel-by-voxel statistical comparison identified regions of significantly abnormal DIR signal intensity (DSI) in 9 out of 10 patients with acquired nonprogressive cerebral lesions and partial seizures. In all 9 patients, the areas of abnormal DSI concurred with abnormalities identified on visual inspection of conventional MRI. In all 14 patients with MCD, SPM detected regions of significantly abnormal DSI; all of which corresponded to abnormalities identified on visual inspection of conventional MRI. In addition, in both groups, there were areas that were normal on conventional imaging, which demonstrated abnormal DSI. Voxel-by-voxel statistical analysis identified significantly abnormal DSI in 15 of the 33 patients with cryptogenic focal epilepsy. In 10 of these, the areas of abnormal DSI concurred with epileptic EEG abnormality and clinical seizure semiology. Group analysis of MRI-negative patients with electroclinical seizure onset localising to the left temporal and left and right frontal regions revealed significantly abnormal DSI within the white matter of each respective lobe. DIR analysed using SPM was sensitive in patients with MCDs and acquired cerebral damage. Significant abnormalities in DSI in individual and grouped MRI-negative patients suggest that occult epileptogenic cerebral lesions are associated with subtle structural abnormalities. DIR is, therefore, a useful quantitative MRI technique for characterising epileptic foci and may contribute to presurgical evaluation.

Adult↗

Magnetic resonance imaging of the normal and injured lateral collateral ligaments of the ankle.

BACKGROUND AND AIMS: To study the role of MR Imaging in evaluating both normal and injured lateral collateral ligaments of the ankle. MATERIALS AND METHODS: Twenty-four patients with clinically diagnosed inversion injury to the ankle and 20 healthy volunteers underwent Magnetic Resonance Imaging (MRI) of the ankle with special emphasis on the lateral complex ligaments. RESULTS: The anterior talofibular (ATFL) and posterior talofibular ligaments (PTFL) were identified in 100% of the ankles of normal volunteers in the axial plane. The PTFL was identified in 100% in the coronal plane. The calcaneofibular ligament (CFL) was identified in 76% of the ankles in the axial, 84% in the coronal and 88% in the sagittal plane. Of the 24 patients with inversion injury, MRI showed ligament abnormalities in 16 patients, ten of these were isolated ATFL tears, five had combined ATFL and CFL tears and one case showed in addition abnormal signal in the PTFL. MRI revealed associated injuries to other ligaments and other soft tissue and osseous structures of the ankle in twelve patients. CONCLUSION: MRI is a non-invasive, accurate technique for evaluation of the normal and injured lateral collateral ligaments of the ankle.

Acute Disease↗

[Diagnostic values of MRI in combination with DSA in vascular malformations of the head and neck].

OBJECTIVE: To evaluate prospectively diagnostic values of magnetic resonance imaging (MRI) as the initial examination for vascular malformations of the head and neck, and establish a flowchart based on radiodiagnostic features. METHODS: 45 patients with vascular malformations of the head and neck were evaluated prospectively with MRI. MRI was followed by angiography in 15 patients, contrast-enhanced CT in 15 patients. MRI was performed by using spin-echo pulse sequences with Philips Gyroscan NT 1.0 Teslaunit. RESULTS: In all cases, MRI demonstrated usefully, and there was no other single imaging modality that could provide information about internal structures and flow characteristics as much as MRI. It made differentiation between high-flow and low-flow lesions obvious, however MRI was inferior to angiography in delineation of feeder vessels. CONCLUSION: MRI can be used as the initial methods for diagnosis of vascular malformations in the head and neck, and could be combined with angiography in cases with high-flow or combined-flow lesions.

Adolescent↗

Regional cerebral blood flow in depressed patients with white matter magnetic resonance hyperintensity.

BACKGROUND: Functional neuroimaging studies have consistently demonstrated decreased regional cerebral blood flow (rCBF) or metabolism in the frontal lobe, temporal lobe, or anterior cingulate gyrus of depressed patients. On the other hand, white matter hyperintensity as defined by magnetic resonance imaging (MRI) has been the most consistently replicated finding in structural neuroimaging studies on depression; however, these functional and structural neuroimaging findings of depression have not been well integrated. We aimed to clarify the possible associations of MRI-defined subcortical hyperintensities with rCBF changes in depressed patients. METHODS: Twelve depressed patients with subcortical hyperintensities defined by MRI, 11 depressed patients without MRI hyperintensities, and 25 healthy volunteers underwent 99mTc ECD SPECT. Group comparisons of their rCBF and correlation analysis between MRI hyperintensity and rCBF in patients were performed with a voxel-based analysis using statistical parametric mapping (SPM) software. RESULTS: Depressed patients showed decreased rCBF compared with control subjects in the frontal lobe, temporal lobe, and anterior cingulate gyrus whether subcortical hyperintensity existed or not; however, the patients with MRI hyperintensity showed decreased rCBF in the thalamus, basal ganglia, and brainstem in addition to cortical areas. Further, the score for white matter hyperintensity correlated negatively with rCBF in subcortical brain structures, including the thalamus and right basal ganglia. CONCLUSION: Our study indicates that depressed patients with MRI hyperintensities may have dysfunction in subcortical brain structures in addition to dysfunction in the fronto-temporal cortical structures.

Adult↗

Use of magnetic resonance imaging in planning the separation of omphalopagus conjoined twins.

Magnetic resonance imaging (MRI) was used for the first time in the preoperative planning for separation of conjoined twins. In these omphalopagus infants, MRI showed normal biliary and cardiovascular structures and demonstrated, in detail, a relatively avascular plane through the liver bridge, which enabled safe separation with minimal blood loss at 3 1/2 months of age. A single MRI study supplied information superior to that obtained with multiple previously available imaging studies. MRI should be an essential part of the preoperative workup of all types of conjoined twins.

Abdomen↗

A three-dimensional MRI atlas of the mouse brain with estimates of the average and variability.

Although there is growing interest in finding mouse models of human disease, no technique for quickly and quantitatively determining anatomical mutants currently exists. Magnetic resonance imaging (MRI) is ideally suited to probe fine structures in mice. This technology is three-dimensional, non-destructive and rapid compared to histopathology; hence MRI scientists have been able to create detailed three-dimensional images of 60 mum resolution or better. The data is digital which lends itself to sophisticated image processing algorithms. Here we show a variational MRI atlas constructed from nine excised brains of 8 week old 129S1/SvImJ male mice. This new type of atlas is comprised of an unbiased average brain--created from alignment of the individual brains--and the mathematical descriptors of anatomical variation across the individuals. We found that the majority of internal points in the individuals never varied more than 117 microm from equivalent points in the atlas. A three-dimensional annotation of the average image was performed and used to estimate the mean and standard deviation of volumes in a variety of structures across the individual brains; these volumes never differed by more than 5%. Our results indicate that variational atlases of inbred strains represent a well-defined basis against which mutant outliers can be readily compared.

Algorithms↗

A simplified approach for assessment of intracardiac baffles and extracardiac conduits in congenital heart surgery with two- and three-dimensional magnetic resonance imaging.

BACKGROUND: Intracardiac baffles and extracardiac conduits have been used in the reconstructive surgery of a broad spectrum of congenital cardiac malformations. Periodic evaluation of these structures may not lend itself readily to echocardiographic and angiographic imaging. The purpose of the study was to describe the experience of our institution with the use of magnetic resonance imaging (MRI) in evaluating conduits and baffles and to describe the simplified approach we developed to image these structures, which allows for grouping individual lesions into broad categories. METHODS AND RESULTS: We retrospectively reviewed our MRI experience in visualizing these structures from 1989-1996. One hundred thirty-nine patients underwent MRI to visualize 144 structures (116 baffles, 28 conduits). The 116 baffles included 86 Fontan, 16 Mustard, 6 Senning, 6 left ventricle to aorta, 1 right ventricle to aorta, and 1 pulmonary vein to left atrium baffle. The 28 conduits included 15 right ventricle to pulmonary artery, 4 left ventricular apical to aorta, 2 left ventricle to pulmonary artery, 3 aorta to aorta, 2 inferior vena cava to left atrium conduits, and 2 aortic root replacements. Of the 3 aortic-aortic conduits, 1 was in conjoined twins. Both inferior vena cava-left atrial conduits were in a Baffes procedure. An infectious mass missed by echocardiography in a right ventricle to pulmonary artery conduit was visualized by MRI. With multiplanar reconstruction, contiguous images were stacked atop each other and resliced to define the salient points of the anatomy. Three-dimensional reconstruction further added to this delineation. All structures were visualized successfully, and an assessment of obstruction was made. Multiple examples of conduit and baffle narrowing were diagnosed by spin echo and cine MRI and were subsequently confirmed by catheterization and surgical inspection. CONCLUSION: MRI, with multiplanar and 3-dimensional reconstruction, is useful in examining the variety of baffles and conduits used in congenital heart surgery. MRI can add to the care of patients whose echocardiographic windows or whose angiographically overlapping structures do not allow adequate delineation of conduits and baffles.

Adolescent↗

Noninvasive imaging of the normal temporal bone. Comparison of sagittal surface coil magnetic imaging and high-resolution computed tomography.

High-resolution computed tomography (HRCT) is a noninvasive technique for evaluating the middle ear for primary and recurrent cholesteatoma. However, a limitation of HRCT is that it cannot differentiate between cholesteatoma and granulation tissue. Magnetic resonance imaging (MRI) is a noninvasive, nonradiologic technique that has been effective in demonstrating histochemical differences between various soft tissues. We present images from a normal living subject's temporal bone in the sagittal plane obtained with both HRCT and MRI. Anatomic correlates in the same cut planes are presented. The HRCT provided excellent detail of the bony landmarks within the temporal bone and was used as the reference for the MRI. The soft-tissue structures such as cranial nerves, cochlea, vestibule, and semicircular canals were identified.

Humans↗

Fetal alcohol spectrum disorders in Finland: clinical delineation of 77 older children and adolescents.

The adverse effects of alcohol on the developing human comprise a spectrum of structural anomalies and behavioral and neurocognitive disabilities, most accurately termed fetal alcohol spectrum disorders (FASD). We previously have proposed revisions to the 1996 Institute of Medicine Diagnostic Criteria for diagnoses in the FASD continuum [fetal alcohol syndrome (FAS), partial fetal alcohol syndrome (PFAS), alcohol related birth defects (ARBD), and alcohol related neurodevelopmental disorder (ARND)], allowing for more reproducible and accurate FASD diagnosis in a clinical setting [Hoyme et al., 2005]. The NIAAA recently has coordinated and funded an international consortium of projects aimed at more complete characterization of the teratogenic spectrum of alcohol. One of the projects sites is in Finland. The aims of this project are: (1) to completely clinically characterize the structural and learning/behavioral phenotypes of a large cohort of older children and adolescents with moderate to severe disability within the FASD continuum; (2) to correlate FASD dysmorphology and behavioral phenotypes with CNS structure and function (i.e., MRS, MRI correlations); (3) to compare the phenotype of a genetically homogeneous population of Finnish children with FASD to that observed in other populations. We have recently completed dysmorphology examination and parent/guardian interviews of the 77 children in the Finnish cohort. The purpose of this report is to present historical and morphometric data on these patients, thereby more completely delineating the clinical spectrum of FASD in older children and adolescents, contrasting the phenotype with that described in other populations and examining whether a weighted dysmorphology score could be used as a clinical and research adjunct when fetal alcohol exposure is being suspected. All children were previously diagnosed with FASD by an experienced pediatric specialist in Finland, and all were exposed to significant maternal alcohol abuse prenatally. The sex ratio of the cohort was 0.38 (male: female) and ages ranged from 8 to 20 years, with a mean of 13 years. After application of the Revised IOM Diagnostic Criteria, 53% of the subjects were diagnosed as having FAS, 30% PFAS, 12% ARND, and 5% other diagnoses. Of note, although a family history of mental retardation or birth defects was rare, 43% of the children had one or more sibling who also carried a diagnosis of FAS. Eighty-nine percent of the mothers smoked cigarettes during gestation; other teratogenic exposures were rare. Almost none had undergone genetics evaluation in the past. Almost all of the subjects had resided in multiple foster placements since early childhood and had been followed regularly by pediatric specialists. Although 11% were born prematurely, 70% demonstrated prenatal growth deficiency, and 45% were microcephalic. Other than growth deficits and the cardinal facial features, the most common major and minor anomalies noted were: camptodactyly (55%), "hockey stick" or other altered palmar creases (51%), refractive errors (40%), strabismus (38%), dental crowding (43%), nail hypoplasia (38%), GU anomalies (22%), and congenital heart defects (18%), "Railroad track" ears were not observed in this population.

Abnormalities, Multiple↗

Serial MRI after experimental febrile seizures: altered T2 signal without neuronal death.

Whereas most febrile seizures (FSs) carry a benign outcome, a subpopulation of individuals with prolonged FSs are at risk for later temporal lobe epilepsy. Signal changes on magnetic resonance imaging (MRI) may provide early markers for changes in neuronal integrity that may promote epileptogenesis in such individuals. Here, we used serial MRIs, obtained before and at several time points after experimental prolonged FSs, to determine the prevalence and distribution of signal changes on T2-weighted images and to investigate the pathological substrates leading to these changes. Seventy-five percent of immature rats with experimental prolonged FSs had abnormal T2 signal enhancement at 24 hours, and 87.5% at 8 days after the seizures. The altered T2 values involved the dorsal hippocampus (75%), the piriform cortex (87.5%), and the amygdala (25%). However, these changes were not accompanied by evidence of neuronal injury or death in these regions, as assessed using the Fluoro-Jade method. Thus, experimental prolonged FSs lead to relatively frequent abnormal MRI signal in "temporal lobe" structures. Although these changes do not signify cell death, they may denote pathological cellular processes that promote epileptogenesis. .

Animals↗

Quantification of multicontrast vascular MR images with NLSnake, an active contour model: in vitro validation and in vivo evaluation.

Vessel-wall measurements from multicontrast MRI provide information on plaque structure and evolution. This requires the extraction of numerous contours. In this work a contour-extraction method is proposed that uses an active contour model (NLSnake) adapted for a wide range of MR vascular images. This new method employs length normalization for the purpose of deformation computation and offers the advantages of simplified parameter tuning, fast convergence, and minimal user interaction. The model can be initialized far from the boundaries of the region to be segmented, even by only one pixel. The accuracy and reproducibility of NLSnake endoluminal contours were assessed on vascular phantom MR angiography (MRA) and high-resolution in vitro MR images of rabbit aorta. An in vivo evaluation was performed on rabbit and clinical data for both internal and external vessel-wall contours. In phantoms with 95% stenoses, NLSnake measured 94.3% +/- 3.8%, and the accuracy was even better for milder stenoses. In the images of rabbit aorta, variability between NLSnake and experts was less than interobserver variability, while the maximum intravariability of NLSnake was equal to 1.25%. In conclusion, the NLSnake technique successfully quantified the vessel lumen in multicontrast MR images using constant parameters.

Animals↗

Molecular mechanisms for the hepatic uptake of magnetic resonance imaging contrast agents.

The mechanisms were investigated for the hepatic transport of 4 different gadolinium complexes used as contrast agents for magnetic resonance imaging (MRI). In basolateral rat hepatocyte plasma membrane vesicles, Gd-DTPA uptake was indistinguishable from non-specific binding to vesicles; Gd-BOPTA and Gd-EOB-DTPA entered plasma membrane vesicles following a linear, concentration-dependent mechanism up to 1.5 mM of substrate. By contrast, Gd-B 20790 uptake followed a saturative kinetic with an apparent Km of 92 +/- 15 microM and a Vmax of 143 +/- 42 pmol/mg prot/15 sec, and it occurred into an osmotic-sensitive space. Sulfobromophthalein ant taurocholate, but not unconjugated bilirubin inhibited the uptake rate of Gd-B 20790 but not that of the other three compounds. Injection into Xenopus laevis oocytes of 5 ng of human OATP cRNA resulted, after 3 days, in a >/=2-fold stimulation (p < 0.001) of transport of Gd-B 20790 but not of Gd-BOPTA or Gd-EOB-DTPA. Collectively, these data indicate that the hepatic uptake of the MRI contrast agent Gd-B 20790 is a carrier-mediated mechanism operated by OATP while MRI compounds with other chemical structures enter the hepatocyte by other mechanisms.

Animals↗

Synthesized surface anatomy scanning (SSAS) for surgical planning of brain metastasis at the sensorimotor region: initial experience with 5 patients.

Surface anatomy scanning (SAS) is a powerful technique that uses T2-weighted magnetic resonance images (MRI) to visualize brain surface structures, and to precisely localize subcortical lesions. To overcome technical limitations of this method, synthesized SAS (SSAS) superimposes MR angiography (MRA) data on the SAS images. We describe our initial experience with surgical planning for the resection of metastases at the sensorimotor region in 5 patients using SSAS. Neurological deficits were assessed before and after surgical resection. Although 4 of 5 patients had mild to severe neurological deficits before surgery, three became symptom-free and no patient had an increased deficit after surgery. Our results undoubtedly provide palliative surgery for sensorimotor metastases. As SSAS is non-invasive and requires a short scanning time, this method could become a useful technique for the routine pre-operative simulation for surgery on brain surface lesions such as sensorimotor metastases.

Adenocarcinoma↗

The myelon in cervical spinal canal stenosis: imaging by X-ray and MRI.

Methods which produce findings relevant to diagnosis and therapy of cervical vertebral canal stenosis are described. Especially MRI provides insights into the structure of the myelon; abnormal image signals may possibly correlate with cervical myelopathy based on disorders of microcirculation.

Adult↗

Stereotactic radiosurgery planning with ictal SPECT images.

This paper is motivated by a clinical requirement to utilise ictal SPECT images for target localisation in stereotactic radiosurgery treatment planning using the xknife system which only supports CT and MRI images. To achieve this, the SPECT images were converted from raw (pixel data only) format into a part 10 compliant DICOM CT fileset. The minimum requirements for the recasting of a raw format image as DICOM CT or MRI data set are described in detail. The method can be applied to the importation of raw format images into any radiotherapy treatment planning system that supports CT or MRI import. It is demonstrated that the combination of the low spatial resolution SPECT images, depicting functional information, with high spatial resolution MRI images, which show the structural information, is suitable for stereotactic radiosurgery treatment planning.

Algorithms↗

Assessment of T2- and T1-weighted MRI brain lesion load in patients with subcortical vascular encephalopathy.

Previous cross-sectional studies in patients with subcortical vascular encephalopathy (SVE) have shown little or no correlation between brain lesion load and clinical disability, which could be due to the low specificity of T2-weighted MRI. Recent studies have indicated that T1-weighted MRI may be more specific than T2-weighted MRI for severe tissue destruction. We studied 37 patients with a diagnosis of SVE and 11 normal controls with standardised T1- and T2-weighted MRI. All patients underwent detailed clinical assessment including a neuropsychological test battery and computerised gait analysis. Both the T2- and T1-weighted total MRI lesion loads different between patients and controls different, particularly T1. The ratio of T2-/T1-weighted lesion load was lower in controls than in patients. There was no overall correlation of T1- or T2-weighted lesion load with clinical disability, but group comparison of patients with severe and mild clinical deficits showed different lesion loads. We suggest that T1- and T2-weighted MRI lesion loads demonstrate relevant structural abnormality in patients with SVE.

Aged↗