Search PubMed⌕ Search

Biomedical subjects

R Kreis

Publications and source records attributed to R Kreis.

53 records · Page 3Linked to original sources
PubMed1996

Phenylketonuria: findings at MR imaging and localized in vivo H-1 MR spectroscopy of the brain in patients with early treatment.

PURPOSE: To characterize white matter changes in early-treated phenylketonuria (PKU) with magnetic resonance (MR) imaging and hydrogen-1 MR spectroscopy and to correlate these findings to biochemical control and brain function. MATERIALS AND METHODS: Fifty-one patients aged 12-33 years underwent T1-, T2-, and proton-density-weighted MR imaging and testing of intelligence, visual evoked potentials (VEPs), and neuropsychologic status (29 adult patients only). H-1 MR spectroscopy was performed in eight patients to determine brain metabolite concentrations, including phenylalanine (PHE) concentration, and brain compartmentation. RESULTS: MR imaging revealed a high frequency of supra- and infratentorial abnormalities. MR imaging grade, which was based on areas of high signal intensity on T2-weighted images, showed statistically significant correlation with long-term biochemical control and neuropsychologic test results but not with intelligence quotient or VEPs. H-1 MR spectroscopy revealed normal metabolite levels, except for increased PHE levels. It also showed enlarged cerebrospinal fluid-like compartments in affected white matter, related to plasma and brain concentrations of PHE and MR imaging grades. CONCLUSION: A synergistic use of MR imaging and MR spectroscopy may help elucidate both the pathogenesis of brain dysfunction and clinical treatment policies in PKU.

Adolescent↗
PubMed1995

Identification and quantitation of phenylalanine in the brain of patients with phenylketonuria by means of localized in vivo 1H magnetic-resonance spectroscopy.

Localized proton MR spectroscopy was used to identify phenylalanine (PHE) and to quantitate its cerebral concentration in patients with type I phenylketonuria (PKU). Data acquisition was optimized for the detection of low-concentration metabolites, using a short TE (20 ms) double Hahn-echo localization sequence for large volumes within the head coil and for smaller volumes using a surface coil. Previously described methods to quantitate localized MR spectra were extended to cover the case of low-concentration metabolites, unevenly distributed in three brain compartments and measured in difference spectra only. PHE content was determined in difference spectra of four PKU patients with respect to normals and in one patient before and after an oral load of L-PHE. PHE concentrations of 0.3 to 0.6 mmol/kg brain tissue were obtained, resulting in a concentration gradient for PHE between blood and brain tissue of 2.4 to 3.0. No significant changes were found for the abundant metabolites in gray or white matter. Previously reported MRI changes were confirmed to be due to increased cerebro-spinal-fluid-like spaces.

Adult↗
PubMed1995

In vivo proton magnetic resonance spectroscopy in a case of Reye's syndrome.

A case of a 14-year-old boy with Reye's syndrome (RS) and complete neurologic recovery is presented. 1H magnetic resonance spectroscopy was performed on days 1 (admission to ICU), 8 and 62: During the acute phase of RS substantial cerebral metabolic imbalances were observed and their normalization monitored. The spectra from day 1 featured extremely high glutamine content (approximately 18 mmol/kg excess) and low concentrations of choline compounds pounds (approximately 1 mmol/kg deficit). Also some excess lactate was present. The subsequent spectra demonstrated the return to an almost normal brain metabolite profile.

Adolescent↗
PubMed1995

The dynamics of brain concentrations of phenylalanine and its clinical significance in patients with phenylketonuria determined by in vivo 1H magnetic resonance spectroscopy.

Cerebral concentrations of phenylalanine (PHE) were measured by means of quantitative in vivo 1H MR spectroscopy in 8 adult patients treated early for phenylketonuria type I. A 1.5-Tesla routine magnetic resonance scanner, localization sequence with short echo time (20 ms), and a fully automated data processing scheme were used. Baseline plasma PHE concentrations were 1.04 (0.70-1.39) mmol/L PHE with concurrent brain PHE concentrations of 0.27 (0.13-0.41) mmol/kg of wet weight resulting in a plasma/brain ratio of 4.12. Plasma and brain concentrations correlated significantly (Kendall tau b = 0.91, p < 0.01). During an oral load with a single dose of 100 mg L-PHE per kg of body weight in four patients, plasma levels steeply increased. Concurrent brain PHE increase was less steep, was significantly delayed, and still continued up to 20 h postload. Despite the proven rise in plasma and brain concentrations of PHE, neuropsychologic examinations revealed no impairment of attentional and fine motor abilities from preload up to 20 h postload.

Adult↗
PubMed1994

Subclinical hepatic encephalopathy: proton MR spectroscopic abnormalities.

PURPOSE: To determine whether hydrogen-1 magnetic resonance (MR) spectroscopy of the brain allows detection of subclinical hepatic encephalopathy (SCHE). MATERIALS AND METHODS: In a double-blind study, overt hepatic encephalopathy (HE) and SCHE (defined with clinical and neuropsychiatric tests) were compared by means of H-1 MR spectroscopic criteria--reduction in cerebral myo-inositol (< 2 standard deviations [SDs] from normal) and choline (< 2 SDs from normal) with or without increased cerebral glutamine (> 1 SD from normal)--in 20 patients with cirrhosis. RESULTS: Concordance between MR spectroscopic and neuropsychiatric test results was 94% (kappa = 0.84). MR spectroscopy allowed diagnosis of SCHE in nine of nine patients (100%) and of HE in seven of eight (88%). Myo-inositol depletion alone had 80%-85% sensitivity for detection of HE and SCHE. CONCLUSION: H-1 MR spectroscopy allows accurate diagnosis of SCHE, and the results suggest an important role for myo-inositol in psychomotor and visuopractic functions.

Adult↗
PubMed1993

Development of the human brain: in vivo quantification of metabolite and water content with proton magnetic resonance spectroscopy.

Cerebral metabolite concentrations and water content were measured by means of localized proton magnetic resonance spectroscopy in 50 children, while metabolite peak ratios in short echo time spectra were evaluated in 173 examinations. Normative curves for normal development were established for two cerebral locations. The current report presents the first study of absolute metabolite concentrations and T1- and T2- relaxation as a function of age. Myo-inositol was found dominating the spectra at birth (12 mmoles/kg), while choline is responsible for the strongest peak in older infants (2.5 mmoles/kg). Creatine and N-acetyl groups are at significantly lower concentrations in the neonate than in the adult (Cr: 6, NA: 5 mmoles/kg). NA and Cr are determined by gestational age, whereas the concentration of ml correlates best with postnatal age. Quantitative 1H MRS is expected to be of particular value in diagnosis and monitoring of pathology in infants, since metabolite ratios are often misleading.

Brain↗
PubMed1992

Metabolic disorders of the brain in chronic hepatic encephalopathy detected with H-1 MR spectroscopy.

Proton magnetic resonance (MR) spectroscopy of the brain was performed in 11 patients with chronic hepatic encephalopathy (CHE), and the results were compared with those of patients with liver disease but without CHE; clinical control subjects with diabetes, uremia, or cortical atrophy; and healthy subjects. The technique of water-suppressed stimulated-echo hydrogen-1 MR spectroscopy for detection of cerebral glutamate, glutamine, glucose, N-acetylaspartate, choline metabolites, (phospho)creatine, and myo-inositol is described. Specific changes in the brain of CHE patients included the anticipated elevation in cerebral glutamine levels (P less than or equal to .0001), a 23% reduction in choline metabolite levels (P less than or equal to .0001), and a more than 50% reduction in cerebral myo-inositol levels (P less than or equal to .0001). In four of the 15 patients with liver disease but without clinical CHE, a significant reduction in the myo-inositol level was detected, and in two of these patients an elevation in the glutamine concentration was also observed. These findings indicate a role for image-guided H-1 MR spectroscopy in the diagnosis and monitoring of both overt and preclinical CHE.

Aspartic Acid↗
PubMed1992

Cerebral metabolic disturbances in patients with subacute and chronic diabetes mellitus: detection with proton MR spectroscopy.

Localized proton magnetic resonance (MR) spectroscopy was used to define biochemical changes in gray and white matter of the cerebral cortex in 22 patients with diabetes mellitus (DM), including 10 episodes of diabetic ketoacidosis (DKA), compared with MR spectra in 30 healthy subjects. Five distinct metabolic abnormalities were identified: Concentrations of glucose (Glc) (P greater than or equal to .002), ketone body or bodies, myo-inositol (P greater than or equal to .003) (with or without glycine), and choline (Cho) metabolites were increased in both white and gray matter, whereas a significant reduction of N-acetyl metabolites was found in the parietal cortex (P greater than or equal to .003). Diurnal variations in the intracerebral concentration of Glc were demonstrated in a patient with DM whose condition was stable. Elevated concentrations of ketones were detected in three episodes and excess Cho in two episodes of DKA. Evidence obtained with hydrogen-1 MR spectroscopy favors acetone rather than acetoacetate as the ketone present in the brain, which is a major target of biochemical change in DM.

Adult↗
PubMed1991

Localized 1H NMR spectroscopy in patients with chronic hepatic encephalopathy. Analysis of changes in cerebral glutamine, choline and inositols.

Localized, short echo 1H magnetic resonance spectra from an area in the parietal cortex of three patients suffering from chronic hepatic encephalopathy are compared with equivalent spectra obtained from healthy control subjects. Three significant differences are found: elevated glutamine, decreased inositol, and decreased choline peak intensities. The elevation of cerebral glutamine concentration is expected as a consequence of the presumed chronic hyperammonemia in this disease. The finding of a 50% change in the inositol peak is physiologically unexpected and so far unaccounted for. Data acquisition and processing parameters are described in detail. To further define spectral abnormalities, which were readily detected in untransformed spectra, a simple data analysis scheme has been used that consists of post-acquisition low-frequency filtering, a lineshape transformation, and a difference technique to clarify spectral changes.

Aged↗
PubMed1983

[Scalds in children: an extremely important problem].

Treatment of scalds in children with human allografts offers the following advantages: 1. Essential relief of pain. 2. Prevention of deepening of scalds by desiccation. 3. Fewer autografting procedures. 4. Shorter hospital stay. 5. Considerably less hypertrophic scarring.

Burns↗
PubMedDate not supplied

1H MRS in acute traumatic brain injury.

The objective of this study was to demonstrate 1H MR spectroscopy (MRS) changes in cerebral metabolites after acute head trauma. Twenty-five patients (12 children, 13 adults) were examined with quantitative 1H MRS after closed head injury. Clinical grade (Glasgow Coma Scale [GCS]) and outcome (Rancho Los Amigos Medical Center Outcome Score [ROS]) were correlated with quantitative neurochemical findings. N-acetylaspartate (NAA), a neuronal and axonal marker, was reduced (P < .03-.001). In children, a reduced NAA/creatine plus phosphocreatine (Cr) level and the presence of detectable lipid/lactate predicted bad outcome (sensitivity, 89%; specificity, 89%). The first MRS examination of all patients correlated with ROS versus NAA (r = .65, P < .0001). Although most patients showed MRS abnormalities, striking heterogeneity of 1H MRS characterized the individual patients. 1H MRS identifies multiple patterns of diffuse brain injury after blunt head trauma. There was a strong correlation between MRS and outcome. Future prospective studies will be needed to determine the clinical usefulness of MRS in predicting outcome from closed head injury.

Adult↗
PubMedDate not supplied

Clinical tools for the 90s: magnetic resonance spectroscopy and metabolite imaging.

Magnetic resonance spectroscopy (MRS) is a flexible tool with real clinical utility. Examples from our experience in over 250 cases of clinical proton MRS are presented. Shorter echo time and reproducible water suppression increases the number of metabolites which can be detected and identified. Case reports illustrate the significance of altered ratios of N-acetylaspartate, choline, total creatine, myo-inositol, glutamate, glutamine, lactate, glucose, ketones, and, as an incidental finding, ethanol. Significant new information has resulted by applying proton MRS in chronic hepatic encephalopathy, diabetes mellitus and severe hypoxic encephalopathy ('near-drowning'). Potentially useful measurements have been made in normal brain maturation, ethanol related diseases, dementia (normal-pressure hydrocephalus), urea cycle defect and neuronal disease presenting as seizures. Metabolite imaging, particularly with proton, is clinically valuable, documenting the heterogeneity of biochemical disorders in seemingly focal lesions. A new method of specific 31-phosphorus--phosphocreatine imaging provides information in partially denervated skeletal muscle and is expected to have applications in brain.

Adult↗