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J Sargentoni

Publications and source records attributed to J Sargentoni.

At least 37 records · Page 2Linked to original sources
PubMed1995

Effect of functional grade and etiology on in vivo hepatic phosphorus-31 magnetic resonance spectroscopy in cirrhosis: biochemical basis of spectral appearances.

Hepatic phosphorus-31 magnetic resonance spectroscopy (31P MRS) was undertaken in 85 patients with histologically proven cirrhosis of varying etiologies and functional severity. Reference data were acquired from 16 healthy volunteers who had no history or evidence of liver disease or alcohol abuse. In vivo hepatic 31P MR spectra were acquired with pulse angle 45 degrees and repetition times (TR) of 5 and 0.5 seconds. Peak area ratios of phosphomonoesters (PME), inorganic phosphate (Pi), and phosphodiesters (PDE) relative to beta ATP, and of PME relative to PDE were calculated from spectra acquired at TR 5 seconds. Estimates of saturation effects for individual resonances were obtained by dividing the peak height at TR 5 seconds by that at TR 0.5 seconds to yield a T1-related signal height ratio (SHR). When compared with reference values, the patients with liver disease showed a significantly higher PME/ATP (P < .0001), PME/PDE (P < .0001), PME SHR (P < .001), and Pi SHR (P < .02), and a lower PDE/ATP (P < .001) and PDE SHR (P < .001). The magnitude of these changes increased significantly and progressively with increasing functional impairment. In patients with compensated cirrhosis spectral appearances varied with etiology; thus, patients with postviral cirrhosis showed a significantly higher Pi/ATP; those with alcoholic cirrhosis, a significantly lower PDE/ATP; and those with cirrhosis secondary to primary sclerosing cholangitis, a significantly lower Pi/ATP than the healthy volunteers or other etiological groups. However, spectral appearances did not vary with etiology in patients with decompensated disease. In vitro 31P MRS of perchloric extracts of samples of liver tissue obtained from 10 patients with cirrhosis at transplant hepatectomy showed increases in levels of the soluble PME metabolites, phosphorylcholine and phosphorylethanolamine, and reductions in the levels of the soluble PDE metabolites, glycerophosphorylcholine and glycerophosphorylethanolamine. These changes suggest regenerative activity in cirrhotic livers. The increases in soluble phosphomonoesters in the aqueous extracts accounted for the increased PME/ATP ratio seen in the in vivo spectra, and might account for the increase in PME SHR. The reduction in soluble phosphodiesters in the aqueous extracts did not entirely account for the reduction PDE/ATP ratio seen in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗
PubMed1994

Regional variations in cerebral proton spectroscopy in patients with chronic hepatic encephalopathy.

Regional variations in proton magnetic resonance spectroscopy (MRS) were assessed in 26 patients and 14 healthy volunteers using a two dimensional chemical shift imaging technique. Patients were classified as being neuropsychiatrically unimpaired, or as having subclinical or overt chronic hepatic encephalopathy (CHE). Peak area ratios of choline (Cho), glutamine and glutamate (Glx) and N-acetylaspartate (NAA) relative to creatine (Cr) were measured. Significant reductions in mean Cho/Cr and elevations in mean Glx/Cr were observed in the patient population, which correlated with the severity of CHE. There were significant regional variations in these metabolite ratios with the mean Cho/Cr lowest in the occipital cortex and the mean Glx/Cr highest in the basal ganglia. NAA/Cr remained relatively constant in all areas of the brain analysed. The regional variation in the metabolite ratios suggests that spectral information from more than one voxel may be useful in the assessment of patients with CHE.

Adult↗
PubMed1994

Cerebral phosphorus-31 magnetic resonance spectroscopy in patients with chronic hepatic encephalopathy.

Cerebral phosphorus-31 magnetic resonance spectroscopy was undertaken in 33 patients with biopsy-proven cirrhosis: 6 had no evidence of neuropsychiatric impairment on standard clinical, psychometric and electrophysiological testing; 8 had evidence of subclinical hepatic encephalopathy; and 19 were classified as having overt hepatic encephalopathy. The reference population comprised 15 healthy volunteers. Unlocalized spectra were acquired from the entire head with a 45-degree pulse angle and repetition times of 1 and 5 sec. Spectra localized to the basal ganglia were acquired with a 45-degree pulse angle and a repetition time of 1 sec. Peak area ratios of phosphomonoesters, inorganic phosphate, phosphodiesters and phosphocreatine relative to beta-ATP were measured in the spectra acquired. We noted no consistent change in the ratios of inorganic phosphate to ATP and phosphocreatine to ATP. Mean values of the ratios of phosphomonoesters to ATP and phosphodiesters to ATP were significantly lower in the total patient population than in the reference population, and they correlated with the patients' neuropsychiatric status. Thus we found no significant reductions in the mean ratios of phosphomonoesters to ATP and phosphodiesters to ATP in patients who were neuropsychiatrically unimpaired, but significant reductions were observed in the mean ratios of phosphomonoesters to ATP and phosphodiesters to ATP in patients with both subclinical and overt hepatic encephalopathy. The most marked reductions in these metabolite ratios were observed in patients with overt encephalopathy.

Adult↗
PubMed1993

A 31P and 1H-NMR investigation in vitro of normal and abnormal human liver.

Spectral changes in human hepatic tumours and possible systemic effects of tumour on host liver were assessed by 31P and 1H in vitro NMR spectroscopy. The 1H and 31P spectra from liver tumour biopsies showed significant elevation in phosphoethanolamine, phosphocholine, taurine, citrate, alanine, lactate and glycine, and significant reduction in GPE (glycerophosphoethanolamine), GPC (glycerophosphocholine), creatine and threonine compared to histologically normal tissue. 31P-NMR spectra obtained from histologically normal tissue within tumour-bearing livers showed significant elevation in phosphoethanolamine and phosphocholine compared to data from liver biopsies from nontumour-bearing patients (pancreatitis). These results suggest that alterations in membrane metabolism in host liver can be detected by 31P-NMR.

Biopsy↗
PubMed1993

In vivo fluorine-19 magnetic resonance spectroscopy of cerebral halothane in postoperative patients: preliminary results.

This study reports the use of 19F MRS to study halothane in the brain of eight patients recovering from halothane anesthesia of short duration. Resonances attributable to halothane were observed up to 90 min after withdrawal of the anesthetic agent. The signal-to-noise ratio for an unlocalized spectrum acquired using a 6 cm surface coil was typically 20 with data collection times of 2 min. In seven patients a single resonance was seen with a mean (+/- SD) chemical shift of +43.3 (+/- 1.8) ppm, referenced to NaF at 0 ppm. This resonance exhibited a T1 value of between 0.5 and 1 s, and a T2* (estimated from the linewidth of the resonance) between 3.5 and 10 ms. In one patient two resonances were observed with chemical shifts of +38 and +41 ppm. Because we cannot exclude the possibility that this was due to field inhomogeneity, the significance of the last finding is uncertain. However, phantom studies show that the chemical shift of halothane in different environments (such as water, olive oil, methanol, and lecithin) can vary to an extent that accounts for the two resonances seen in our patient. These results demonstrate the feasibility of in vivo 19F MRS studies of fluorinated volatile agents in humans. The potential for clinical 19F MRS of fluorinated anesthetics is discussed.

Adult↗
PubMed1993

Proton spectroscopy of the neonatal brain following hypoxic-ischaemic injury.

Proton magnetic resonance spectroscopy was used to examine, within the first month of life, the brains of 11 infants born at term--10 with signs of hypoxic-ischaemic encephalopathy (HIE) and one who was neurologically normal at birth. All the infants had peak resonances on their spectra which could be assigned to N-acetyl-aspartase (NAA), choline-containing compounds (Cho) and creatine plus phosphocreatine (Cr). When neurodevelopmental outcome at one year was correlated with initial spectroscopy findings, the NAA/Cho and NAA/Cr ratios reflected clinical outcome. This study suggests that proton spectroscopy not only provides new information about biochemical changes occurring in the brains of infants with HIE, but also may help to predict outcome within the first month of life.

Brain↗
PubMed1992

Phosphorus-31 magnetic resonance spectroscopy of the human liver using chemical shift imaging techniques.

Phosphorus-31 magnetic resonance spectroscopy of the human liver was undertaken in 28 healthy adult individuals and in 49 patients with liver disease of varying aetiology. Data localised to the liver were obtained using chemical shift imaging techniques. The mean (+/- 1 S.D.) of the peak area ratio phosphomonoesters (PME)/phosphodiesters (PDE) in healthy adult individuals, from spectra obtained with pulse angle 45 degrees and repetition time 1 s, was 0.24 +/- 0.07. The intra-examination variability of this ratio was 20%, the intra-subject variability 27% and the inter-subject variability 32%. An increase in the PME/PDE was observed in the 31P hepatic MR spectrum from primary or secondary tumours in all 17 patients studied, which invariably represented an increase in PME/ATP and, in some cases, a reduction in PDE/ATP. The spectra did not show aetiological characteristics. A non-specific elevation in PME/PDE was also observed in the 31P hepatic MR spectra of 10 (40%) of 25 patients studied who had diffuse liver diseases, such as cirrhosis and infiltrating malignancies. The spectral pattern did not distinguish between diseases of varying aetiologies, but there was a linear correlation between increasing PME/PDE and a reduction in plasma albumin concentrations (p = 0.03). In three patients with hepatic malignancy and abnormal hepatic 31P-MRS, marked spectral changes were observed after successful treatment to debulk the tumour. Only minor changes were observed in the abnormal spectrum of a fourth patient in whom treatment was unsuccessful. Hepatic 31P-MR spectroscopy may prove useful for monitoring disease processes and treatment effects in well characterised patient populations.

Adenocarcinoma↗
PubMed1992

Effect of L-alanine infusion on 31P nuclear magnetic resonance spectra of normal human liver: towards biochemical pathology in vivo.

1. 31P n.m.r. spectroscopy in vivo was used to study the effect of L-alanine infusion on the concentrations of gluconeogenic intermediates in normal human liver. Studies were performed in six healthy male subjects (34-44 years, fasted overnight) using a chemical shift imaging pulse sequence on a whole-body n.m.r. system operating at 1.6T. Hepatic 31P n.m.r. spectra were obtained from 10 min before to 70 min after intravenous administration of 0.70 (n = 2), 1.40 (n = 3) or 2.80 (n = 5) nmol of L-alanine/kg body weight over 4.5 min. Concentrations of phosphomonoesters, Pi and phosphodiesters relative to ATP were calculated from peak areas in the n.m.r. spectra, using the beta-ATP peak as a reference. 2. Dose-dependent spectral changes were observed for [phosphomonoesters]/[ATP] and [Pi]/[ATP]. At the highest dose given, maximal changes in [phosphomonoesters]/[ATP] (mean +/- SEM: 98 +/- 12%, P < 0.005) and [Pi]/[ATP] (-33 +/- 3%, P < 0.001) were observed approximately 45 min after the L-alanine infusion. [Phosphodiesters]/[ATP] showed a maximal increase of 24 +/- 6% (P < 0.05), which was independent of the L-alanine dose. Hepatic ATP levels and pH did not change. 3. To identify the metabolites responsible for the changes observed in vivo, male Wistar rats were infused with 11.2 mmol of L-alanine/kg body weight. After 15 min, livers were freeze-clamped and were extracted according to standard procedures. In vitro, 31P n.m.r. spectra obtained at 8.4 or 11.7 T revealed sharp increases in the concentrations of 3-phosphoglycerate and phosphoenolpyruvate after L-alanine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1992

Magnetic resonance for the anaesthetist. Part I: Physical principles, applications, safety aspects.

Anaesthetists are being increasingly involved in magnetic resonance (MR) procedures, both in patient care and as a research tool. This paper outlines the physical basis of nuclear magnetic resonance and describes its application in magnetic resonance imaging and spectroscopy. Principles of magnet design and safety relevant to anaesthetic practice in a magnetic resonance environment are discussed and guidelines for anaesthetic practice suggested. Some recent clinical magnetic resonance studies of anaesthetic interest are reviewed.

Anesthesiology↗
PubMed1992

Magnetic resonance for the anaesthetist. Part II: Anaesthesia and monitoring in MR units.

Anaesthetists are increasingly involved in patient care during magnetic resonance imaging and spectroscopy. This paper describes a system which has been developed for the management of critically ill patients and the conduct of anaesthesia in a magnetic resonance unit with a 1.6 tesla whole body magnet. Difficulties which arise from working in a confined space in a high magnetic field are highlighted. Different approaches to anaesthesia, sedation and the modification of equipment for use in this environment are reviewed. The problems associated with patient monitoring within a magnetic field are discussed and some solutions are suggested. A transport system for critically ill patients is described and a protocol for management is outlined.

Anesthesia↗
PubMed1991

Saturation effects in phosphorus-31 magnetic resonance spectra of the human liver.

Phosphorus-31 liver spectra were recorded from 6 controls and 12 patients with liver disease using TR values of 0.5 and 5 s and a pulse angle of 45 degrees. One of the control subjects was also examined at seven TR values ranging from 0.5 to 20 s. Spectra from one additional patient were collected at TRs of 0.5, 1, and 2 s only. There was a significant increase in the mean ratio of peak areas phosphomonoesters (PME)/beta-ATP in 9 of the 13 patients and a decrease in phosphodiesters (PDE)/beta-ATP in 3 of the patients, compared with controls, at the longer TR values. The saturation factors for PME and PDE were greater than those for Pi and beta-ATP, and spectral abnormalities in disease were often more evident as the TR value was increased from 0.5 to 5 s. Acquisition parameters need to be chosen with a knowledge of the impact that saturation effects have on metabolite quantification and spectral contrast.

Adenosine Triphosphate↗
PubMed1989

31P magnetic resonance spectroscopy of the normal human brain: approaches using four dimensional chemical shift imaging and phase mapping techniques.

The use of four-dimensional chemical shift imaging to monitor phosphorus metabolites within the human brain is illustrated. Saturation effects are described, and acquisition conditions are discussed in relation to quantification and sensitivity. The effects of magnetic field variations on spectral parameters are assessed and the use of a field mapping technique is illustrated.

Adult↗
PubMed1988

Four-dimensional phosphorus-31 chemical shift imaging of carcinoid metastases in the liver.

Four-dimensional chemical shift imaging was used to map spatial variations in phosphorus metabolites in a patient with carcinoid metastases in the liver. The results were compared to those from an age and sex matched volunteer, with no known previous history of liver disease. In the patient local abnormalities were observed. These included elevated phosphomonoester and decreased phosphodiester concentrations relative to adenosine triphosphate. The regions of abnormality corresponded to regions containing metastases identified with x-ray computed tomography and magnetic resonance imaging.

Adult↗
PubMedDate not supplied

Effects of fish oil on phospholipid metabolism in human and rat liver studied by 31P NMR spectroscopy in vivo and in vitro.

The effect of omega 3 fatty acids on the metabolism of the normal liver was studied using 31P NMR spectroscopy. Human subjects were examined before and after 1, 3 and 7 days of supplementation with 50 mL fish oil per day (12 g omega 3 fatty acids). 31P NMR spectra (1.6 T) revealed a significant increase in phosphodiester (PDE) to ATP ratios after 1 and 3 days of fish oil. After 7 days, [PDE]/[ATP] ratios at a TR of 1 s had returned to baseline levels, but [PDE]/[ATP] at a TR of 5 s appeared to remain high. Rats were fed diets containing 50% of the energy from fish oil or normal rat chow (controls) for 14 days. 31P NMR liver spectra in vivo (4.7 T) confirmed increased [PDE]/[ATP] in rats fed fish oil compared to controls, although the difference was only statistically significant at a TR of 1.5 s but not at a TR of 8 s. 31P NMR spectra of rat liver extracts (8.7 T) suggested that increased concentrations of glycerophosphocholine and possibly glycerophosphoethanolamine were responsible for rising PDE levels in vivo. Phosphocholine (PC) concentrations were markedly reduced in rat liver after fish oil. The combined rise in glycerophosphocholine and reduction in PC would be consistent with a shift from the phospholipase C to the phospholipase A1/A2 pathway of phosphatidylcholine breakdown after fish oil consumption.

Adult↗
PubMedDate not supplied

Proton MR spectroscopy in herpes simplex encephalitis: assessment of neuronal loss.

We present here the case of an 11-year-old boy with herpes simplex encephalitis diagnosed on the basis of clinical features, serology, and response to acyclovir, who relapsed after 3 weeks of therapy. In vivo proton magnetic resonance spectroscopy (1H MRS) of the brain, at 8 and 16 weeks after the onset of symptoms, showed abnormalities, most prominently a reduction in the N-acetylaspartate/choline ratio. The role of 1H MRS in assessing disease activity is discussed.

Aspartic Acid↗
PubMedDate not supplied

Proton MR spectroscopy of the brain in infants.

Proton magnetic resonance spectroscopy (MRS) was used to study the brain of 2 normal and 15 abnormal infants aged from 33 weeks postmenstrual age (PMA) to 14 months postnatal age. Eleven of the infants were examined on at least two occasions. The principal clinical diagnoses in the abnormal infants were perinatal ischemic and hemorrhagic brain injury. All proton spectra demonstrated peaks that were assigned to N-acetylaspartate (NAA), choline containing compounds (Cho), and creatine plus phosphocreatine (Cr). The NAA/Cho and NAA/Cr ratios increased with age, while the Cho/Cr ratio decreased with age in the majority of infants. The NAA/Cho ratio was generally lower in abnormal infants, but the difference was not apparent before 40 weeks (PMA). This ratio was lowest in infants with the severest degree of neurological abnormality. Proton and phosphorus MRS was compared in seven infants. In those with severe brain lesions, early phosphorus spectra were abnormal. On follow-up the phosphorus spectra became normal, but the proton spectra showed persistently low NAA/Cho and NAA/Cr ratios. Proton MRS provides new information that may be complementary to phosphorus MRS in the diagnosis and monitoring of brain development in normal and neurologically damaged infants.

Asphyxia Neonatorum↗