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Ingrid L Kwee

Publications and source records attributed to Ingrid L Kwee.

12 recordsLinked to original sources
PubMed2005

High-field, T2 reversed MRI of the hippocampus in transient global amnesia.

OBJECTIVE: To investigate the fine structural integrity of the hippocampus in patients with transient global amnesia (TGA) using high-resolution T2 reversed (T2R) MRI. METHODS: The authors performed detailed structural analysis of the hippocampus in 15 patients who had recovered from an episode of TGA and 150 randomly recruited normal volunteers across the adult age spectrum using high-resolution T2R MRI obtained on a 3.0-T system. An additional 100 subjects, with stroke or tumor, were similarly studied and served as disease controls. RESULTS: The overall incidence of hippocampal cavities detected in normal volunteers increased with age but never exceeded 40%, whereas the incidence in disease control group was 31%. They were always unilateral. In contrast, cavities were found in all 15 patients with TGA (100%), an incidence higher than in normal or disease controls (p < 0.05; Ryan's multiple comparison test), and were bilateral in eight patients (53%). The cavities in all but one of the normal volunteers (99%) and all disease controls (100%) were crescent shaped and < or =2 mm in width. The cavities in 14 of 15 patients with TGA (93%) were considerably larger (>3 mm in width), and five of the patients had giant cavities (>5 mm in width). Most of the cavities in patients with TGA had a rounded shape and resembled pathologic cavities described in specimens of hypoxia-related CA1 necrosis. CONCLUSION: The data indicate that transient global amnesia may not be a benign entity. Delayed neuronal loss within CA1 area of Lorente de No may represent its important sequel.

Adolescent↗
PubMed2005

Diffusion tensor analysis in chronic schizophrenia. A preliminary study on a high-field (3.0T) system.

The objective of this study was to delineate further the nature of diffusion anisotropy abnormalities in frontal white matter previously observed in schizophrenic patients using a high-field magnetic resonance imaging (MRI) system. Six schizophrenia patients and six healthy control subjects were examined using a highfield MRI (3.0T) system. In order to confirm previously reported abnormalities in anisotropy, data were first analyzed to determine fractional anisotropy (FA), a frequently utilized general index of anisotropy. Subsequently, the identical data set was subjected to lambda chart analysis (LCA), a newly developed algorithm for diffusion tensor analysis (DTA) that more effectively provides eigenvalue information. Frontal white matter FA was found to be significantly reduced in schizophrenic patients compared to control subjects, confirming previously reported findings. LCA revealed that the decline in FA was due to a disproportionate increase in small eigenvalue components, and not due to a decline in principal eigenvalue components.

Adult↗
PubMed2005

Isotropic component trace analysis.

A new method for analyzing diffusion tensor imaging (DTI) of the brain, based on a recently introduced algorithm, lambda chart analysis (LCA), is presented. Pre-treatment of a given DTI data set with LCA, which effectively segregates isotropic and anisotropic components, allows for total removal of the anisotropic component from the DTI data set. The remaining pure isotropic component can therefore be subjected to further analysis similar to that applied in the trace histogram method. Deconvolution of the trace function yielded 3 Gaussian elements. Remapping of these 3 deconvoluted isotropic elements back onto the 2-dimensional image plane provided anatomical correlates of each element. The algorithm, referred to here as isotropic component trace analysis, can be used as a pictorial analytic tool, as well as a numerical analytical tool, for the noninvasive assessment of isotropic parenchymal components. The presented method provides quantitative indices of certain parenchymal parameters with better clarity than currently available methods. A ready-to-use program, EZ-LCA, for this powerful method is provided (available at http://coe.bri.niigata-u.ac.jp).

Algorithms↗
PubMed2005

MT+/V5 activation without conscious motion perception: a high-field fMRI study.

While activity of MT+/V5 neurons is believed to be necessary for the conscious perception of visual motion, whether neural activity in MT+/V5 is a sufficient condition for the conscious perception of motion in vision still remains unanswered. A high-field (3.0 Tesla) functional magnetic resonance imaging (fMRI) study was designed and performed to answer this specific question. Eleven healthy subjects viewed a checkerboard pattern stimulus reversed in contrast at 0.2, 12, 30, and 60 Hz while being probed for activation in MT+/V5. At 0.2 Hz, all viewers perceived pattern-reversal which was stationary in position. However, at 12, 30, and 60 Hz, many subjects perceived apparent motion (e.g., vertical and horizontal flows) in the square pattern. At 12 and 30 Hz reversals, MT+/V5 was activated in all subjects (11/11). Nevertheless, three out of eleven (3/11) subjects denied motion perception in these conditions. At 60 Hz reversal, as many as seven out of eleven (7/11) subjects failed to see motion but activation in MT+/V5 was found in the majority (5/7) of the subjects. The results demonstrated that significant MT+/V5 activation occurs without accompanying subjective awareness of seeing motion in an apparent-motion stimulus, indicating that neural activity in MT+/V5 does not represent a sufficient condition for conscious perception of motion in vision.

Adult↗
PubMed2005

Diffusion tensor analysis of peritumoral edema using lambda chart analysis indicative of the heterogeneity of the microstructure within edema.

OBJECT: Histopathological studies indicate that cerebral edema associated with tumors (peritumoral edema) does not represent a single pathophysiological or clinical entity. In this study the authors investigated peritumoral edema by performing lambda chart analysis (LCA), a noninvasive technique that can be used to make visible and analyze apparent water diffusivity in tissues in vivo, and assessed the utility of LCA in differentiating high-grade gliomas from nonglial tumors. METHODS: The water diffusivity characteristics of peritumoral edema associated with four tumor groups-12 high-grade gliomas, five low-grade gliomas, 11 metastatic tumors, and 15 meningiomas-were assessed in 43 patients by performing magnetic resonance imaging with the aid of a 3-tesla magnetic resonance imaging system. In all tumor groups, peritumoral edema exhibited greater trace values and reduced anisotropy compared with normal white matter. Edema associated with high-grade gliomas had significantly higher trace values than edema associated with the other three tumor groups, although the anisotropic angles of those groups were comparable. CONCLUSIONS: Lambda chart analysis identified two distinct types of peritumoral edema: edema associated with high-grade gliomas and edema associated with low-grade gliomas or nonglial tumors. The apparent water diffusivity was significantly greater in high-grade gliomas, whereas the anisotropy in these lesions was comparable to that of edema in other tumors. These findings indicated that water movement in areas of edema, predominantly in the extracellular spaces, was less restricted in high-grade gliomas, a phenomenon that likely reflected the destruction of the extracellular matrix ultrastructure by malignant cell infiltration and consequently greater water diffusion. Although preliminary, this study indicates that LCA could be used as a clinical tool for differentiating high-grade gliomas and for evaluating the extent of cellular infiltration.

Adolescent↗
PubMed2004

Coerced training of the nondominant hand resulting in cortical reorganization: a high-field functional magnetic resonance imaging study.

OBJECT: The authors investigated brain strategies associated with hand use in an attempt to clarify genetic and nongenetic factors influencing handedness by using high-field functional magnetic resonance imaging. METHODS: Three groups of patients were studied. The first two groups comprised individuals in whom handedness developed spontaneously (right-handed and left-handed groups). The third group comprised individuals who were coercively trained to use the right hand and developed mixed handedness, referred to here as trained ambidexterity. All trained ambidextrous volunteers were certain that they were innately left-handed, but due to social pressure had modified their preferred hand use for certain tasks common to the right hand. Although right-handed and left-handed volunteers displayed virtually identical cortical activation, involving homologous cortex primarily located contralateral to the hand motion, trained ambidextrous volunteers exhibited a clearly unique activation pattern. During right-handed motion, motor areas in both hemispheres were activated in these volunteers. During left-handed motion, the right supplemental motor area and the right intermediate zone of the anterior cerebellar lobe were activated significantly more frequently than observed in naturally right-handed or left-handed volunteers. CONCLUSIONS: The results provide strong evidence that cortical organization of spontaneously developed right- and left-handedness involves homologous cortex primarily located contralateral to the hand motion, and this organization is likely to be prenatally determined. By contrast, coerced training of the nondominant hand during the early stages of an individual's development results in mixed handedness (trained ambidexterity), indicating cortical reorganization.

Cerebral Cortex↗
PubMed2003

All-phase MR angiography using independent component analysis of dynamic contrast enhanced MRI time series: phi-MRA.

Dynamic contrast enhanced magnetic resonance imaging (dynamic MRI) represents a MRI version of non-diffusible tracer methods, the main clinical use of which is the physiological construction of what is conventionally referred to as perfusion images. The raw data utilized for constructing MRI perfusion images are time series of pixel signal alterations associated with the passage of a gadolinium containing contrast agent. Such time series are highly compatible with independent component analysis (ICA), a novel statistical signal processing technique capable of effectively separating a single mixture of multiple signals into their original independent source signals (blind separation). Accordingly, we applied ICA to dynamic MRI time series. The technique was found to be powerful, allowing for hitherto unobtainable assessment of regional cerebral hemodynamics in vivo.

Aged↗
PubMed2003

Absolute eigenvalue diffusion tensor analysis for human brain maturation.

The absolute eigenvalues of the diffusion tensor of white matter in sixteen normal subjects in two groups representing the early developmental stage (ages 1-10 years, n=8) and young adult stage (ages 18-34 years, n=8) were assessed using a high-field (3.0 T) magnetic resonance (MR) system. All three eigenvalues, including the largest eigenvalue, decreased significantly with brain maturation. The rate of the decline in the two small eigenvalues was, however, much higher than that of the largest eigenvalue, resulting in an actual increase in fractional anisotropy, a commonly measured relative index. The data demonstrate that an increase in anisotropy associated with brain maturation represents a significant decline in the small eigenvalue components, rather than an increase in the largest eigenvalue. The observed pattern of eigenvalue changes is best explained by the simultaneous occurrence of two of several independent phenomena within the axonal microenvironment during the myelination process, namely, (1) decline in unrestricted water content in extra-axonal space, and (2) increase in apparent diffusivity within the axon.

Adolescent↗
PubMed2003

Dorsolateral prefrontal lobe activation declines significantly with age--functional NIRS study.

Dorsolateral prefrontal cortex (DLPF) activation in response to cognitive paradigms engaging working memory was quantitatively evaluated using functional near infrared spectroscopy (fNIRS) in cognitively normal individuals across the age spectrum (20-90 years; 8 females, 52 males). DLPF activation score (DAS) demonstrated a significant decline (r(2) = -0561, p < 0.05) as a function of age. The study indicates that blood flow response associated with DLPF activation declines as a function of age in cognitively normal individuals and that fNIRS can be used as a convenient, portable tool for assessing such activation.

Adult↗
PubMed2002

Evaluation of efficacy of an automated single-voxel proton MRS algorithm on a 3T system.

PURPOSE: To evaluate the efficacy of a fully automatic, single-voxel, proton MR spectroscopy algorithm on a 3.0T MR system. METHODS: The PROBE/SVQ algorithm (GE Medical Systems) was evaluated on a General Electric (GE) Signa LX-3T system. Ten normal volunteers (female, 21.1+/-2.0 years old) participated in the study. Nine representative regions of interest were examined, namely, right and left frontal white matter; right and left parietal white matter; right and left basal ganglia; right and left dentate nucleus; and pons. RESULTS: The mean coefficients of variation in all regions for the N-acetyl-aspartate to creatine ratio (NAA/Cr), choline to creatine ratio (Cho/Cr), and choline to N-acetyl-aspartate ratio (Cho/NAA) were 10.2+/-2.4%, 11.4+/-3.2% and 12.6+/-1.4%, respectively. CONCLUSION: A fully automated spectroscopic examination under clinical setting utilizing the PROBE/SVQ algorithm appears to be a reliable method, extending the window of routine clinical assessment of brain metabolism.

Adult↗
PubMed2002

Criteria for normalcy of cavities observed within the adult hippocampus: high-resolution magnetic resonance imaging study on a 3.0-T system.

BACKGROUND AND PURPOSE: Cavities occasionally found within the hippocampus during routine clinical magnetic resonance imaging (MRI) studies are believed to be a normal variant reflecting fluid collection within the vestigial hippocampal sulcus. However, the lack of systematic studies defining objective criteria for such cavities has hampered further assessment of potential abnormalities within the hippocampus. This study assessed the detailed characteristics of hippocampal cavities in normal subjects using a new high-resolution MRI technique in an attempt to define objective criteria of normalcy. METHODS: A new high-resolution imaging technique, T2-reversed MRI on a high-field (3.0-T) system was used to image the hippocampus in 74 normal volunteers in 3 age groups (28 young, 24 middle, and 22 senior). RESULTS: Residual cavities in the vestigial hippocampal sulcus were resolved as single, crescent-shaped structures along the deep aspect of the vestigial hippocampal sulcus. The size of the cavities did not vary with age and never exceeded 1 mm in width and 3 mm in length. The frequency of detection, however, increased with age (21.4% [5/28] in the young, 25.0% [6/24] in the middle, and 36.4 [8/22] in the senior age group). CONCLUSION: The study established clear objective criteria for normal cavities within the hippocampus. These cavities likely represent physiological fluid collection within the vestigial hippocampal sulcus. Any cavity that does not meet these defined criteria should be considered potentially abnormal.

Adult↗