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Biomedical subjects

M Reivich

Publications and source records attributed to M Reivich.

At least 127 records · Page 7Linked to original sources
PubMed1983

A computerized system for the elastic matching of deformed radiographic images to idealized atlas images.

A system of computer programs is described which, for the first time, is able to use computerized tomographic data to automatically locate, measure, and describe anatomical structures of interest with accuracy and consistency. Input to the system consists of any digitized radiographic data. Computer assisted tomographic (CAT) scans of the head were used in this first implementation. Using these data and a predefined atlas picture representing an idealized view of the average normal image, an individualized atlas was created. From the individualized atlas, structure size, density, location displacement, and distortion may be calculated. The individualized atlas created using high resolution data, such as the CAT scan, may then be directly superimposed on pictures obtained using lower resolution modalities, such as positron emission tomographic scan images. This allows the precise location of structures poorly visualized by the secondary imaging modality. This system is capable of using either two- or three-dimensional data.

Adolescent↗
PubMed1983

Positron emission tomographic studies of sensory stimuli, cognitive processes and anxiety.

Research in detecting regional changes in brain metabolism related to functional activity is reviewed and supplemented by original results from positron emission tomography (PET) and the 18F-fluorodeoxyglucose method (FDG). A formula for calculating the value of local cerebral glucose metabolism (LCMRGlc) is discussed. Results concerning auditory stimulation suggest that metabolic responses are determined by the stimulus content and analysis strategy used by the subject rather than the side of stimulation. Tactile stimulation of the hand and fingers caused asymmetrical increases in LCMRGlc confirming topographic maps of the postcentral gyrus and other functional studies. Data from visually stimulated normal subjects show how the visual hemifields project to the opposite calcarine cortex. Studies of patients with hemianopsia or various field defects demonstrated that metabolic scanning can reveal alterations of cortical function not detectable by CT scan. Data obtained reveal the ability of metabolic mapping to subdivide the occipital cortex into distinct regions. Such measurements may also anticipate the course of visual recovery. Findings of increased overall right-hemispheric metabolism during the performance of verbal and spatial cognitive tasks are consistent with earlier results from right-handed males. Results for the frontal eye fields provide the first experimental evidence that lateralized metabolic activity, produced by cognitive tasks, causes similarly lateralized activity within a motor region. It is further demonstrated that FDG is able to provide information on such states as vigilance and anxiety.

Anxiety↗
PubMed1982

Sex and handedness differences in cerebral blood flow during rest and cognitive activity.

Cognitive activity resulted in increased flow of blood to the cerebral hemispheres. The increase was greater to the left hemisphere for a verbal task and greater to the right hemisphere for a spatial task. The direction and degree of hemispheric flow asymmetry were influenced by sex and handedness, females having a higher rate of blood flow per unit weight of brain, and females and left-handers having a greater percentage of fast-clearing tissue, presumably gray matter.

Adolescent↗
PubMed1982

Use of 2-deoxy-D[1-11C]glucose for the determination of local cerebral glucose metabolism in humans: variation within and between subjects.

The deoxyglucose technique for the measurement of local cerebral glucose metabolism (LCMRgl) has been widely applied in animals utilizing 14C-deoxyglucose and in humans employing 18F-fluorodeoxyglucose. Repeat studies in humans over a relatively brief period of time have not been possible because of the 110-min half-life of fluorine-18. With the synthesis of 11C-deoxyglucose it has now become possible to utilize this short-lived (20 min) tracer for the measurement of LCMRgl and to determine its variability within subjects over a 2-h period. The kinetic rate constants for 11C-deoxyglucose were determined for gray and white matter and found to be very similar to those for 18F-fluorodeoxyglucose, suggesting that these two analogues of glucose have similar affinities for the facilitated transport system and are similar substrates for hexokinase in the brain. The coefficient of variation of repeated measurements of LCMRgl in a series of six normal subjects was 5.5% to 8.7% for various gray matter structures and 9.7% and 14.0% for white matter structures. The pattern of cerebral metabolic rates is relatively constant in a given individual when the conditions of the study are unchanged. The ability to make repeat measurements in the same subject reduces the variance due to between-subject differences, allowing smaller changes in LCMRgl to be detected with confidence.

Brain↗
PubMed1982

Noninvasive method of estimating human newborn regional cerebral blood flow.

A noninvasive method of estimating regional cerebral blood flow (rCBF) in premature and full-term babies has been developed. Based on a modification of the xenon-133 inhalation rCBF technique, this method uses eight extracranial NaI scintillation detectors and an i.v. bolus injection of xenon-133 (approximately 0.5 mCi/kg). Arterial xenon concentration was estimated with an external chest detector. Cerebral blood flow was measured in 15 healthy, neurologically normal premature infants. Using Obrist's method of two-compartment analysis, normal values were calculated for flow in both compartments, relative weight and fractional flow in the first compartment (gray matter), initial slope of gray matter blood flow, mean cerebral blood flow, and initial slope index of mean cerebral blood flow. The application of this technique to newborns, its relative advantages, and its potential uses are discussed.

Breath Tests↗
PubMed1982

Error analysis for the determination of cerebral blood flow with the continuous inhalation of 15O-labeled carbon dioxide and positron emission tomography.

The inhalation of C15O2 can be used for determining local cerebral blood flow (LCBF) using a quantitative model. The determination of LCBF in three dimensions using positron emission tomography (PET) involves errors due to counting statistics, data manipulation, and the estimation of parameters in the mathematical model. This work examines error propagation and its relation to the radiation dose to the subject's lungs. An expression has been derived for the root mean square uncertainty in LCBF as a function of LCBF, the spatial resolution and the sensitivity of PET instrument, the normal variability in the brain-blood partition coefficient for water, and absorbed radiation dose to the subject's lungs. The error in LCBF increases as CBF increases. At a normal cortical LCBF of 80 ml/100 g-m and a PET instrument with a 1.65 cm FWHM resolution, and a 46,000 cps per microCi/g sensitivity per slice, an error (coefficient of variation) of 5% results from an inhaled activity of 250 mCi, resulting in a lung dose of 5 rads, the maximum permissible dose allowed. For a more acceptable dose of 1.2 rads, the error is 7%. At a higher resolution (0.8 cm FWHM) and lower sensitivity (15,000 cps per microCi/g per slice), errors become on the order of 28% for a lung dose of 1.2 rads. Errors due to other factors such as blood sample counting, and instrument cross calibration can be virtually eliminated by proper technical strategies. This consideration of error and its relation to radiation dose is important for the application of this inhalation technique for the quantification of LCBF.

Administration, Intranasal↗
PubMed1982

Positron emission tomography in two cases of childhood epileptic encephalopathy (Lennox-Gastaut syndrome).

Two patients with childhood epileptic encephalopathy were studied by positron emission tomography before and after corpus callosotomy. Preoperatively, both patients showed in the temporal lobe unilateral hypometabolism that is characteristic of interictal epileptic foci. Postoperatively, the first patient had no seizures by the time of scanning, and his temporal lobe metabolism was bilaterally symmetric. Seizure control in the second patient did not improve by the time of scanning, and unilateral temporal hypometabolism persisted. This finding suggests a temporal lobe focus in two patients with Lennox-Gastaut syndrome.

Adult↗
PubMed1982

The radiation dosimetry of 2 [F-18]fluoro-2-deoxy-D-glucose in man.

Bladder and brain time-activity measurements in humans were performed after the intravenous administration of 2-[F-18]fluoro-2-deoxy-D-glucose. Radiation doses were calculated using the MIRD schema. The bladder wall received an average of 440 mrad/mCi (s.e. 76) in ten subjects who voided at 2 hr after administration of tracer. If these subjects had voided at 1 hr, the bladder-wall dose would have been reduced to 220 mrad/mCi. The brain received an average of 81 mrad/mCi in eight subjects. The doses to other organs, calculated from published dog biodistribution data, are between 50 and 85 mrad/mCi except for spleen and heart, which both received 160 mrad/mCi. These time-activity measurements for the critical organ in the human avoid the assumptions made in using animal biodistribution data for human dosimetry calculations.

Adult↗
PubMed1981

Metabolic mapping of functional activity in human subjects with the [18F]fluorodeoxyglucose technique.

The 2-[18F]fluoro-2-deoxy-D-glucose technique was used to measure regional cerebral glucose utilization by human subjects during functional activation. Normal male volunteers subjected to one or more sensory stimuli (tactile, visual, or auditory) exhibited focal increases in glucose metabolism in response to the stimulus. Unilateral visual hemifield stimulation caused the contralateral striate cortex to become more metabolically active than the striate cortex ipsilateral to the stimulated hemifield. Similarly, stroking the fingers and hand of one arm with brush produced an increase in metabolism in the contralateral postcentral gyrus, compared with the homologous ipsilateral region. The auditory stimulus, which consisted of a monaurally presented factual story caused an increase in glucose metabolism in the auditory cortex in the hemisphere contralateral to the stimulated ear. These results demonstrate that the technique is capable of providing functional maps in vivo related to both body region and submodality of sensory information in the human brain.

Adult↗
PubMed1981

Vaginocervical stimulation selectively increases metabolic activity in the rat brain.

Vaginocervical stimulation affects progesterone secretion, sperm transport, sexual receptivity, locomotion, and perception of pain in female rats. In this experiment, vaginocervical stimulation produced statistically significant increases in the metabolic uptake of carbon-14-labeled 2-deoxy-D-glucose in the following brain areas (ordered by magnitude of uptake): medial preoptic, mesencephalic reticular formation, bed nucleus of stria terminalis, dorsal raphe, and globus pallidus. The results provide information about the concurrent processing of sensory stimulation by several neural areas and indicate that the medial preoptic area is a receiving area for copulatory stimulation.

Animals↗
PubMed1981

Mapping of functional activity in brain with 18F-fluoro-deoxyglucose.

The efficacy of using the 18F-fluoro-deoxyglucose (18F-DG) for measuring regional cerebral glucose utilization in man during functional activation is demonstrated. Normal male volunteers subjected to sensory stimuli (visual, auditory, tactile) exhibited focal increases in glucose metabolism in response to the stimulus. Unilateral visual hemifield stimulation caused the contralateral striate cortex to become more active metabolically than the striate cortex ipsilateral to the stimulated hemifield. Similarly, stroking of the fingers and hand of one arm with a brush produced an increase in metabolism in the contralateral postcentral gyrus compared to the homologous ipsilateral region. The auditory stimulus, which consisted of monaural listening to either a meaningful or nonmeaningful story, caused an increase in glucose metabolism in the right temporal cortex independent of which ear was stimulated. These results demonstrate that the 18F-DG technique is capable of providing functional maps in vivo in the human brain.

Adult↗
PubMed1981

Technical note. Computer assisted analysis of tomographic images of the brain.

A computer system for the analysis of computed tomography and positron emission tomography scans of the brain is described. The system, called TOAP (Tomographic Overlay and Analysis Program), permits the registration of user specified slices from a digital brain atlas with the tomographic images. Regions of interest can then be defined with respect to the atlas. The system thus affords an objective and reproducible means for the analysis of tomographic images.

Brain↗
PubMed1980

Differences in the distribution of gray and white matter in human cerebral hemispheres.

The distribution of gray matter in the two cerebral hemispheres was determined by the xenon-133 inhalation method. There was more gray matter relative to white matter in the left hemisphere than in the right, particularly in the frontal and precentral regions. This finding suggests that the organization of the left hemisphere, relative to that of the right, emphasizes processing or transfer within regions, or both, rather than transfer across regions.

Brain↗