Biomedical subjects

J C Haselgrove

Publications and source records attributed to J C Haselgrove.

At least 19 recordsLinked to original sources

PubMed2001

Diffusion-weighted imaging and fluid attenuated inversion recovery imaging in the evaluation of primitive neuroectodermal tumors.

The aim of our study was to determine whether fluid-attenuated inversion recovery (FLAIR) imaging and diffusion-weighted imaging (DWI) would be helpful in characterizing primitive neuroectodermal tumors (PNET) from other pediatric brain tumors. We expected that the compact cellular nature and the relatively small extracellular space of this tumor would affect the signal intensity on both pulse sequences relative to the more sparsely cellular glial tumors that have larger extracellular spaces. Eighteen pediatric patients with PNET were examined on a 1.5 T MRI with routine imaging plus FLAIR and compared with 28 patients with nonPNET. DWI was also performed in 7 PNET and 18 non-PNET. Seventyeight percent of PNET were isointense to gray matter on FLAIR while 82% of non-PNET were hyperintense and only one was isointense (3%). Diffusion was abnormally restricted in all 7 PNET examined (100%) but was restricted in non-PNET in only 1 out of 18 (6%) patients who had DWI. The differences in the histologic architecture between PNET and non-PNET are reflected in both FLAIR imaging and in DWI.

Adolescent↗

PubMed2001

Diffusion-weighted imaging in the evaluation of watershed hypoxic-ischemic brain injury in pediatric patients.

The purpose of our study was to determine the usefulness of echo-planar diffusion-weighted imaging (EPDI) in the evaluation of watershed hypoxic-ischemic brain injury in pediatric patients. Eighteen patients ranging in age from 3 weeks to 12 years were evaluated for evidence of ischemic/infarction changes on conventional MR and EPDI. Included in the study group were five patients with sickle cell disease, four with congenital heart disease, four with hypotensive episodes with various etiologies, three with sepsis, and two with encephalitis or meningitis. Patients were examined 2 h to 6 days after the initial insult, with follow-up studies in four patients at 1 to 62 days after the initial examination. After conventional MR imaging (T1, FSE T2, and FLAIR), diffusion-weighted MR imaging was performed using high-speed, single-shot EP techniques with TR 6000, TE 144, matrix 96 x 128, FOV 23.3 x 31 and five b values of 0, 160, 360, 640, and 1,000 s/mm2. EPDI demonstrated abnormally increased signal in watershed ischemic/infarction zones in all initial cases. Apparent diffusion coefficients (ADC) were obtained in 59 lesions. When compared with radiographically normal (on EPDI) contralateral brain parenchyma, 45 demonstrated a relatively decreased ADC, while eight had normal ( +/- 10%) and six had increased ADC. In four cases, signal abnormalities on EPDI were not seen or exceeded that seen with conventional MR imaging. In the remaining cases, signal abnormalities were obvious on EPDI and more subtle on conventional MR imaging. Follow-up studies demonstrated resolution of abnormal EPDI signal with persistent abnormalities on conventional imaging in some cases, while others revealed an increase in size or number of EPDI signal abnormalities, suggesting ongoing acute ischemic/infarctive changes. EPDI is a rapid, sensitive technique for detecting watershed ischemic/infarction changes in pediatric patients with hypoperfusion episodes, at times before such changes are apparent on conventional MR images and/or are clinically apparent.

Brain↗

PubMed2001

Diffusion imaging in pediatric central nervous system infections.

Our purpose was to investigate the role of diffusion imaging (DI) in central nervous system (CNS) infections in pediatric patients. It was anticipated that DI would be more sensitive than conventional MRI in the detection of the infarctive complications of infection, and possibly, in the detection of the infectious process as well. Seventeen pediatric patients, eight having meningitis,, five with herpes encephalitis, three with brain abscess or cerebritis and one with sepsis, were evaluated at 1.5-T with DI. All herpes patients had positive DI at the site of herpetic involvement, and two had the addition of watershed infarctions. DI demonstrated more lesions in three of the four cases of herpetic encephalitis. Half the meningitis cases had watershed infarction where DI was better and half had vasculitic infarctions in which DI was equal to or better than conventional MRI. Diffusion imaging was more sensitive than conventional MRI alone in detection of changes due to infections and ischemic lesions, but did not differentiate between them by DI or apparent diffusion coefficient (ADC), although anatomic distribution of lesions proved useful.

Adolescent↗

PubMed2001

Ocular dominance in anterior visual cortex in a child demonstrated by the use of fMRI.

Negative signal changes in the visual cortex have been observed during visual stimulation when performing functional magnetic resonance imaging (fMRI) in children. This report investigated whether the ocular dominance, which has been demonstrated in the contralateral anterior visual cortex in adults, could be observed in a child by the use of fMRI. A 5-year-old child was studied using fMRI at 1.5 T during alternating monocular visual stimulation under sedation with morphine and pentobarbital. The functional images were motion corrected, and statistical parametric maps were made by contrasting the left or right eye stimulation conditions vs the right or left eye stimulation conditions, respectively, at each voxel. Areas with negative signal changes were found on the left anterior visual cortex during monocular visual stimulation of the right eye and vice versa. There was no area with negative or positive signal change on the ipsilateral visual cortex to the stimulated eye and no area with positive signal change on the contralateral visual cortex. Contralateral ocular dominance of anterior visual cortex similar to that of adults was demonstrated in this child with a negative correlation with the visual stimulus. This finding suggests that peripheral visual fields are represented in the anterior visual cortex of 5-year-old children.

Child, Preschool↗

PubMed2001

Visual activation in functional magnetic resonance imaging at very high field (4 Tesla).

OBJECTIVES: Functional magnetic resonance imaging (fMRI) at very high field strengths provides functional brain mapping with the enhanced signal to noise ratio and the larger blood oxygenation level-dependent (BOLD) effect. We report activated areas in the standard space detected by fMRI at 4 Tesla (T) during simple visual stimulation. MATERIALS AND METHODS: Twelve healthy young subjects were scanned using a 4 T scanner during binocular flashing visual stimulation. Functional images were realigned to the first scan and then spatially normalized. Individual and group data analyses were performed to identify areas of visual activation. RESULTS: Activation of the bilateral primary visual cortex (V1/V2) was observed along the entire calcarine fissure in all subjects. The activated area extended to the extrastriate cortex in all subjects. Activation of the bilateral lateral geniculate nucleus (LGN) was detected in all subjects. The group data showed activation of the bilateral primary visual cortex and the bilateral lateral geniculate nucleus. CONCLUSIONS: Robust activation of the vision-related areas was successfully obtained in all subjects using a 4 T magnetic resonance scanner. These results suggest that fMRI at very high field strengths may be effective in showing visual system physiology, and that it can be a promising method to assess visual function of human subjects.

Adult↗

PubMed2001

Functional magnetic resonance imaging of the visual system.

Functional magnetic resonance imaging (fMRI), which is a technique useful for non-invasive mapping of brain function, is well suited for studying the visual system. This review highlights current clinical applications and research studies involving patients with visual deficits. Relevant reports regarding the investigation of the brain's role in visual processing and some newer fMRI techniques are also reviewed. Functional magnetic resonance imaging has been used for presurgical mapping of visual cortex in patients with brain lesions and for studying patients with amblyopia, optic neuritis, and residual vision in homonymous hemianopia. Retinotopic borders, motion processing, and visual attention have been the topics of several fMRI studies. These reports suggest that fMRI can be useful in clinical and research studies in patients with visual deficits.

Amblyopia↗

PubMed2000

Contralateral monocular dominance in anterior visual cortex confirmed by functional magnetic resonance imaging.

PURPOSE: Although it is known that the damage to anterior striate cortex results in temporal peripheral visual field loss of the contralateral eye in patients with cerebral visual disturbance, the monocularity of anterior striate cortex has not been demonstrated in normal living humans. The aim of this study was to investigate whether this could be shown noninvasively using functional magnetic resonance imaging of the human visual cortex. METHODS: Eleven normal volunteers were studied with functional magnetic resonance imaging during alternating monocular visual stimulation using a 1.5 Tesla scanner. The data were motion corrected and spatially normalized to the standard brain. The monocular activation of the visual cortex was compared with the activation by the other eye. RESULTS: In the individual data analysis, contralateral eye dominance was always observed in the anterior striate cortex. In the group analysis from 11 subjects, the area with contralateral eye dominance was found in the most anterior part of primary visual cortex where the calcarine fissure merged with the parieto-occipital sulcus. CONCLUSIONS: This study shows that the contralateral eye dominance of anterior striate cortex can be detected noninvasively with functional magnetic resonance imaging during monocular visual stimulation. The finding confirms that the anterior striate cortex, where the monocular temporal crescent is represented, is primarily monocular, but the fact that greatest density of retinal ganglion cells and photoreceptors is in the nasal hemiretina must also be taken into account when interpreting these results.

Dominance, Cerebral↗

PubMed2000

Functional MRI in children with congenital structural abnormalities of the occipital cortex.

Functional MRI techniques were used to map the position of visual cortex in an awake and a sedated child with congenital anomalies of the posterior hemispheres. In one subject with cortical heterotopia, an activated cortex was found distinct from the structurally abnormal area detected on conventional MRI. In a sedated patient with holoprosencephaly, activated cortical areas in the posterior-medial portions of the hemispheres were identified. This study demonstrates the utility of functional MRI in such patients, both awake and sedated.

Adolescent↗

PubMed2000

Reproducibility of visual activation in functional MR imaging and effects of postprocessing.

BACKGROUND AND PURPOSE: Functional MR imaging studies of the brain should be interpreted in the context of their reproducibility. We assessed the reproducibility of visual activation measured by functional MR imaging and analyzed the effect of image transformation to standard space. METHODS: Seven healthy volunteers were studied twice with echo-planner functional MR imaging at 1.5 T during visual stimulation. The studies were separated by an interval of 2 to 7 days. Functional images were analyzed after spatial normalization to the space described by Talairach and Tournoux and/or after coregistration of the images of the second study with the images of the first study. The number of active voxels for each study was determined at three thresholds. In addition, the change in the center of the mass of activation, the mean change in signal intensity, and the mean t value within the activated area were measured. These reproducibility indexes were calculated for the spatially normalized and nonnormalized data for each subject. RESULTS: Variations in visual activation were observed between the two studies in the same individual as well as across subjects. There was no evidence of an effect from image transformation on reproducibility on any of the measures. CONCLUSION: Our findings show that the reproducibility of activation in functional MR imaging may be much more variable across subjects than suggested in previous studies. The use of different types of image transformation (coregistration, spatial normalization) does not significantly affect the reproducibility of visual activation.

Adult↗

PubMed2000

Functional magnetic resonance imaging of lateral geniculate nucleus at 1.5 tesla.

Although activation of the lateral geniculate nucleus has been detected by functional magnetic resonance imaging with magnetic field strengths higher than 2.0 Tesla, there have been no reports of functional magnetic resonance imaging of the lateral geniculate nucleus with the more widely available 1.5 Tesla scanner. The authors used functional magnetic resonance imaging techniques at 1.5 Tesla to detect lateral geniculate nucleus activation in five of seven healthy subjects. This study shows that visual activation of the lateral geniculate nucleus can be obtained with functional magnetic resonance imaging using conventional 1.5 Tesla scanners.

Adult↗

PubMed1999

Magnetic resonance imaging measurement of volume magnetic susceptibility using a boundary condition.

A magnetic resonance imaging method is described for measuring the magnetic susceptibility difference between two homogeneous macroscopic compartments in contact with each other. A boundary condition is derived for the interface of the two compartments. This boundary condition predicts that across the interface there is a resonant frequency jump, which is a function of interfacial orientation relative to B0 field and the difference in susceptibility of the two sides. Based on this relationship, the magnetic susceptibility difference between two materials can be obtained from MR gradient echo imaging using signals from both sides in the vicinity of the boundary. This method is demonstrated by solution phantom experiments.

Algorithms↗

PubMed1999

Changes in brain water diffusion during childhood.

We studied the changes in brain water diffusion in childhood as seen on diffusion-weighted MRI in 30 children from 1 day of life to 17 years to provide a data base and to investigate the correlation of diffusion changes with known patterns of white matter maturation. The apparent diffusion coefficient (ADC) and apparent anisotropy (AA) were calculated in numerous regions of the brain to include major white matter tracts and gray matter. ADC and AA values were directly related to the structural maturity and compactness of the white matter tracts and changed with aging in a way that predated early myelination markers such as signal change on T1- or T2-weighted images. Diffusion of water is sensitive to structural changes in the brain such as white matter maturation and may be useful in investigating white matter disorders.

Adolescent↗

PubMed1999

High-resolution imaging using Hadamard encoding.

High-resolution imaging techniques using noninvasive modalities such as magnetic resonance (MR) imaging are being pursued as in vivo cancer screening techniques in an attempt to eliminate the invasive nature of surgical biopsy. When acquiring high-resolution MR images for tissue screening, image fields of view have in the past been limited by the matrix sizes available in conventional MR scanners. We present here a technique that uses aliasing to produce high resolution images with larger matrix sizes than are currently available. The image is allowed to alias in both the frequency encoding and phase encoding dimensions, and the individual, aliased fields of view are recovered by Hadamard encoding methods. These fields may then be tiled to obtain a composite image with high spatial resolution and a large field of view. The technique is demonstrated using two-dimensional and three-dimensional in vivo imaging of the human brain and breast.

Brain↗

PubMed1999

Congenital chest lesions: diagnosis and characterization with prenatal MR imaging.

PURPOSE: To evaluate prenatal magnetic resonance (MR) imaging for diagnosis of fetal chest masses and to determine if MR imaging provides information in addition to that of ultrasonography (US). MATERIALS AND METHODS: Eighteen pregnant women were referred for MR imaging of possible fetal chest tumors seen at US (16 congenital cystic adenomatoid malformation [CCAM], two bronchopulmonary sequestration [BPS]). The presence, position, size, and characteristics of masses were determined and correlated with postnatal results. RESULTS: The MR imaging diagnoses were three cases of congenital diaphragmatic hernia, nine of CCAM, two of BPS, and one each of foregut cyst, lung atresia, tracheal atresia, and bronchial stenosis. MR imaging results were in agreement with US results in nine fetuses and in disagreement in nine. MR imaging diagnoses were confirmed at surgery or autopsy in 17 fetuses. MR imaging results led to an error in diagnosis in one fetus with BPS. CONCLUSION: Fetal chest masses had characteristic MR imaging appearances. MR imaging was accurate for distinguishing congenital diaphragmatic hernia from CCAM and was useful for less common diagnoses and determination of the origin of very large chest tumors. Prenatal diagnosis was changed in some patients owing to MR results and affected treatment and counseling of parents. MR imaging is a valuable adjunct to US for prenatal diagnosis of fetal chest masses.

Bronchopulmonary Sequestration↗

PubMed1998

1H MR spectroscopy of the basal ganglia in childhood: a semiquantitative analysis.

Proton MR spectra of the basal ganglia were obtained from 28 patients, 24 male and 14 female, median age 16.3 months (5 weeks to 31 years). They included 17 patients with normal MRI of the basal ganglia without metabolic disturbance (control group) and 11 patients with various metabolic diseases: one case each of high serum sodium and high serum osmolarity, cobalamin C deficiency, Leigh disease, Galloway-Mowat syndrome, Pelizaeus-Merzbacher disease, hemolytic-uremic syndrome and Wilson disease and two cases of Alagille syndrome and methylmalonic acidemia with abnormal MRI of the basal ganglia or blood or urine analysis (abnormal group). The MR spectrum was measured by using STEAM. The MR-visible water content of the region of interest was obtained. Levels of myoinositol, choline, creatine and N-acetylaspartate were measured using a semiquantitative approach, with absolute reference calibration. In the control group, there was a gradual drop of water content over the first year of life; N-acetylaspartate, creatine and myoinositol levels showed no significant change with age, in contrast to the occipital, parietal and cerebellar regions. Choline showed a gradual decrease for the first 2 years of life and then remained fairly constant. In the abnormal group the water content was not significantly different. N-Acetylaspartate was decreased in patients with high serum sodium and high serum osmolarity, cobalamin C deficiency, Leigh disease and one case of methylmalonic acidemia. Decreased creatine was also found in Leigh disease, and decreased choline in Galloway-Mowat syndrome and Wilson disease. Myoinositol was elevated in the patient with abnormally high serum sodium, and decreased in the hemolytic-uremic syndrome.

Adolescent↗

PubMed1998

MRI for physiology and function: technical advances in MRI of congenital heart disease.

Cardiovascular MRI is an active area of research, and the techniques and application are continuing to evolve. We have presented the basic categories of MRI techniques used to image the heart and have shown some examples of advanced techniques applied to the evaluation of congenital heart disease. The reader is referred to other articles for examples of these techniques in clinical practice.

Equipment Design↗

PubMed1998

Advances in pediatric neuroimaging.

Magnetic resonance evaluation of the pediatric central nervous system is rapidly improving in a number of ways: (1) anatomically with higher resolution; (2) with greater sensitivity to pathological processes characterized by increased water content utilizing fluid attenuated inversion recovery imaging (FLAIR); (3) with greater speed of acquisition with ultrafast (1 s/image) and echo planar imaging techniques (50 ms/image); (4) with measurement of cerebral blood flow as perfusion; (5) with measurement of water proton dispersion (e.g. diffusion imaging); (6) with measurement of biochemical components within tissues with proton spectroscopy; and (7) with evaluation of cortical activation with functional magnetic resonance imaging.

Central Nervous System Diseases↗

PubMed1998

Variability in visual cortex activation during prolonged functional magnetic resonance imaging.

This study was conducted to test whether cortical activation varies across successive epoques during functional magnetic resonance imaging (fMRI) studies. Ten normal adult volunteers were studied with a 1.5-T MR scanner. Pseudocoronal study planes were chosen perpendicular to the tentorium cerebelli, at two thirds the distance from the posterior edge of the splenium of the corpus callosum to the transverse sinuses. Functional images were acquired with a T2*-weighted spoiled gradient echo sequence. The visual cortex was stimulated by goggles flashing at 8 Hz. Each study consisted of 82 sequential scans, lasting 15 seconds each for a total of 20.5 minutes. Two scans without stimulation were alternated with two scans of visual stimulation. Scans 3 through 83 were divided into five sequences of 16 scans. For each sequence, the number of pixels within a predefined rectangular region of interest that showed increased activity during stimulation were counted. Least squares regression models of straight lines were fit to the data. The initial level of visual cortex activation in the region of interest, as measured by the y-intercept, varied substantially from subject to subject (range: 4-68, p < 0.001). There was sufficient evidence of systematic change with time to reject the hypothesis of constant activation with the same stimulus over time (p=0.02). The observed visual cortex activation with single-plane fMRI varied both with time over successive epoques and among subjects. Possible factors responsible for the variation may include head movement, eyelid position, attention, and physiologic fatigue. These factors must be accounted for in experimental design and in data analysis and interpretation.

Adult↗