Biomedical subjects

J C Haselgrove

Publications and source records attributed to J C Haselgrove.

At least 19 recordsLinked to original sources

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↗

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↗

PubMed1997

Left-sided congenital diaphragmatic hernia: value of prenatal MR imaging in preparation for fetal surgery.

PURPOSE: To evaluate the usefulness of prenatal magnetic resonance (MR) imaging in determination of the position of the fetal liver and amount of lung tissue in left-sided congenital diaphragmatic hernia. MATERIALS AND METHODS: In three pregnant women, MR imaging was performed with a 1.5-T magnet and fast gradient-echo, half-Fourier single-shot turbo spin-echo, and echo-planar sequences. MR imaging findings were compared with those from ultrasound (US) performed the same day. The fetuses were 20, 23, and 32 weeks gestational age. RESULTS: The fetal liver was demonstrated in the chest in all three fetuses with MR imaging and in only one fetus with US. The best images of the fetal liver were obtained with a T1-weighted gradient-echo sequence. The best images of the entire fetus were obtained with a half-Fourier single-shot turbo spin-echo sequence. CONCLUSION: In these fetuses, MR imaging proved important by clearly demonstrating herniation of fetal liver into the chest, thereby changing family counseling and prenatal care.

Counseling↗

PubMed1996

Correction for distortion of echo-planar images used to calculate the apparent diffusion coefficient.

An algorithm for correcting the distortions that occur in diffusion-weighted echo-planar images due to the strong diffusion-sensitizing gradients is presented. The dominant distortions may be considered to be only changes of scale coupled with a shear and linear translation in the phase-encoding direction. It is then possible to correct for them by using an algorithm in which each line of the image in the phase-encoding direction is considered in turn, with only one parameter (the scale) to be found by searching.

Algorithms↗

PubMed1995

Three-dimensional reconstruction of fibrin clot networks from stereoscopic intermediate voltage electron microscope images and analysis of branching.

Fibrin polymerizes to produce branching fibers forming a three-dimensional network, which has been difficult to visualize by conventional microscopy. Three-dimensional images of whole clots at high resolution were obtained from stereo-pair intermediate-voltage electron micrographs. Computer software was developed to produce three-dimensional reconstructions of the networks in the form of a pattern of links that connect branching junctions. Network parameters were measured and analyzed to characterize the clots quantitatively. Models in which all links were moved to the origin, while preserving their orientation, allowed visualization of some network parameters and facilitated comparison of networks. Fibrin clots formed in three different conditions were analyzed and compared by these methods. Clots formed in 0.20 M saline buffer consist of fibers of uniform size, and most of the branching junctions consist of three links. Fibrin clots formed in 0.05 M saline buffer are made up of very large diameter fiber bundles with far fewer branching junctions and correspondingly longer links. Clots formed in 0.40 M saline buffer consist of very fine fibers with numerous branching junctions and very short links. In summary, the extent of lateral aggregation is directly related to the distance between branching junctions and inversely related to the total number of branching junctions. These observations must be considered in defining possible mechanisms of fibrin branching.

Biophysical Phenomena↗

PubMed1995

Proton MR spectroscopy of pediatric cerebellar tumors.

PURPOSE: To investigate the role of proton MR spectroscopy in pediatric cerebellar tumor diagnosis. METHODS: Single voxel pulse sequences with long echo time (135 or 270 milliseconds, voxel size 8 to 19 cm3), were used to obtain proton spectra of primary pediatric cerebellar tumors. Eleven primitive neuroectodermal tumors (patient age, 2 to 12 years; mean, 7 years), 11 low-grade astrocytomas (age, 2 to 16 years; mean, 9 years), 4 ependymomas (age, 1 to 6 years; mean, 4 years), 1 mixed glioma ependymo-astrocytoma (age, 11 years), 1 anaplastic ependymoma (age, 7 years), 1 ganglioglioma (age, 14 years), and 1 malignant teratoma (age, 6 days) were studied. Control cerebellum spectra were acquired from five patients without abnormality in cerebellum (age, 2 to 15 years; mean, 8 years). The signal intensities from choline-containing compounds (Cho), creatine/phosphocreatine (Cr), N-acetyl-aspartate (NAA), and lactate (Lac) were quantified. The mean and standard deviation of metabolite ratios were calculated. RESULTS: The control spectra ratios (NAA:Cho = 1.49 +/- 0.36, Cr:Cho = 1.13 +/- 0.23) were distinct from the tumor spectra (NAA:Cho = 0.41 +/- 0.27 and Cr:Cho = 0.37 +/- 0.23). Most of primitive neuroectodermal tumors had low NAA:Cho (0.17 +/- 0.09) and Cr:Cho (0.32 +/- 0.19). Compared with primitive neuroectodermal tumors, low-grade astrocytomas and ependymomas had higher NAA:Cho ratio (0.63 +/- 0.19 and 0.39 +/- 0.12). The Cr:Cho ratio was higher for ependymomas (0.60 +/- 0.20) than for astrocytomas (0.27 +/- 0.12) and primitive neuroectodermal tumors. No NAA was found in the malignant teratoma. Lac:Cho ratio was 0.66 +/- 0.40, 0.58 +/- 0.30, and 0.08 +/- 0.12 for astrocytoma, ependymoma, and primitive neuroectodermal tumor, respectively. Lactate was elevated in the mixed glioma ependymo-astrocytoma, ganglioglioma, and teratoma. The NAA and lactate signals were sometimes obscured by lipids in the spectra. Discriminant analysis was carried out using NAA:Cho and Cr:Cho ratios to differentiate the three major tumor types. The sensitivity/specificity values for diagnosing astrocytoma, ependymoma, and primitive neuroectodermal tumor were found to be 0.91/0.84, 0.75/0.92, and 0.82/0.89, respectively, based on this study. CONCLUSION: In many cases, proton MR spectroscopy can be used to help differentiate cerebellar primitive neuroectodermal tumor, low-grade astrocytoma, and ependymoma.

Adolescent↗

PubMed1994

A MRI bolus tagging method for observing helical flow in the descending aorta.

We present a MRI bolus tagging method for exploring the helical nature of blood flow in the aorta. Two image series are collected, the first to quantify longitudinal flow (coronal/sagittal imaging plane-transverse saturation plane), the second to measure rotational flow (transverse imaging plane-coronal/sagittal saturation plane). The experimental protocol has been established in healthy adult volunteers and children with normal vasculature. Our results permit immediate visualization of the unique nature of helical flow in each volunteer. We demonstrate evidence of rapid helical twist, no helical twist, and reversal of twist.

Adult↗

PubMed1993

Resorption of peritumoural oedema in cerebral gliomas during dexamethasone treatment evaluated by NMR relaxation time imaging.

Peritumoural brain oedema is a prominent feature of malignant brain tumours. Glucocorticoids diminish the neurological symptoms and signs caused by the oedema and reduce the abnormally high cerebral water content. The exact mechanisms of action of the glucocorticoids are unknown. The present study investigates the influence of dexamethasone on NMR relaxation time T1 in peritumoural oedema in 13 patients with gliomas. It is shown that NMR T1 images can be used as a potent monitor of brain oedema, and that dexamethasone significantly reduces mean T1 after 1, 3, and 7 days of treatment by 2%, 6%, and 13% respectively. Using an image histogram analysis technique the term "super-oedema" was defined as the 50% of the total oedema area with the highest T1, corresponding to the highest water content. It is shown, that with this technique the treatment effect of steroids on super-oedema was a reduction of 13%, 33%, and 57% after 1, 3, and 7 days of treatment respectively. The mean change after 24 hours of treatment was statistically significant (p < 0.01). The method can be used in all situations where the anti-oedematous effect of a given treatment is to be monitored.

Aged↗

PubMed1993

Spectral localization of arbitrarily shaped regions of interest (SLASH) using single voxel signals.

A method for obtaining localized spectra from arbitrarily shaped regions of interest is described. When a sample consists of homogeneous compartments or domains, spectra localized in each compartment can be obtained from signals of single voxels with regular shapes by solving a set of simultaneous linear equations. Experimental demonstrations on a phantom and on human brain in vivo for a two compartment, two voxel case are presented. The issue of signal-to-noise ratio is also discussed.

Brain↗

PubMed1993

Computer modeling of the oxygen supply and demand of cells of the avian growth cartilage.

We have used computer modeling studies to investigate the oxygen supply to the prehypertrophic and hypertrophic regions of avian growth plate. We measured experimentally the characteristics of the oxygen consumption of chondrocytes at different oxygen tensions. The oxygen consumption decreases at low oxygen tensions. This relation between oxygen tension and oxygen consumption serves as a protective mechanism that prevents the cells in the prehypertrophic zone from becoming anoxic in the regions farthest from the blood vessels. The results of the calculations, when combined with redox measurements of the cells in the growth plate, indicate that the metabolism of the chondrocytes is not controlled simply by the available oxygen supply.

Animals↗