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Biomedical subjects

F Peeters

Publications and source records attributed to F Peeters.

At least 19 recordsLinked to original sources
PubMed2005

Cerebral metabolic correlates of four dementia scales in Alzheimer's disease.

Different scales can be used to evaluate dementia severity in Alzheimer's disease (AD). They do assess different cognitive or functional abilities, but their global scores are frequently in mutual correlation. Functional imaging provides an objective method for the staging of dementia severity. Positron emission tomography was used to assess the relationship between brain metabolism and four dementia scales that reflect a patient's global cognitive abilities (mini mental state), caregiver's evaluation of cognitive impairment (newly designed scale), daily living functioning (instrumental activities of daily living) and global dementia (clinical dementia rating). We wondered whether different clinical dementia scales would be related to severity of metabolic impairment in the same brain regions, and might reflect impairment of common cognitive processes. 225 patients with probable AD were recruited in a prospective multicentre European study. All clinical scales were related to brain metabolism in associative temporal, parietal or frontal areas. A factorial analysis demonstrated that all scales could be classified in a single factor. That factor was highly correlated to decrease of cerebral activity in bilateral parietal and temporal cortices, precuneus, and left middle frontal gyrus. This finding suggests that global scores for all scales provided similar information on the neural substrate of dementia severity. Capitalizing on the neuroimaging literature, dementia severity reflected by reduced metabolism in posterior and frontal associative areas in AD might be related to a decrease of controlled processes.

Activities of Daily Living↗
PubMed2004

Calculation of the renal perfusion and glomerular filtration rate from the renal impulse response obtained with MRI.

The aim of this study was to assess the importance of deconvolution for the calculation of renal perfusion and glomerular filtration rate (GFR) on the basis of concentration-time curves as measured with perfusion MRI. Six rabbits were scanned dynamically after injection of a gadolinium chelate. Concentration-time curves were generated by manually drawing regions of interest in the aorta and the renal cortex. To remove the dependency on the arterial input function, a regularized structured total least-squares deconvolution algorithm was used to calculate the renal impulse response. This curve was fitted by the sum of two gamma variate functions, corresponding to the passage of the contrast agent in the glomeruli and the proximal convoluted tubules. Tracer kinetics models were applied to these two functions to obtain the renal perfusion and GFR. For comparison, these two parameters were also calculated on the basis of the renal concentration-time curve before deconvolution. The renal perfusion values correlated well (r = 0.9, P = 0.014) with the values calculated by a validated upslope method. The GFR values correlated well (r = 0.9, P = 0.014) with the values obtained from the clearance of (51)Cr-EDTA. A comparison of the values obtained with and without deconvolution demonstrated the necessity of deconvolution.

Algorithms↗
PubMed2003

How psychotic are individuals with non-psychotic disorders?

BACKGROUND: The objective of this study was to compare, using a self-report questionnaire, the dimensions of psychosis across different patient groups in a community mental health service (CMHS) and in non-patients in the general population. METHODS: The Community Assessment of Psychic Experiences (CAPE) is a 40-item self-report instrument with positive, negative and depressive symptom dimensions. Seven hundred and sixty-two patients and 647 subjects in the general population filled in the CAPE. In 555 of the 762 patients, a DSM-IV diagnosis was made. The following DSM-IV categories were used in the analyses: 1. Schizophrenia and Other Psychotic Disorders (n = 72), 2. Mood Disorders (n = 214), 3. Anxiety Disorders (n = 129). The patient and non-patient groups were compared on the three dimensions of the CAPE using multivariate regression analysis. RESULTS: The patient groups scored significantly higher on the positive, negative and depressive dimensions than the non-patients. Patients with psychotic disorders had the greatest difference in positive psychosis items compared to non-patients (beta = 0.94, 95 % CI: 0.7-1.18), whereas patients with mood and anxiety disorders had the highest depressive symptom scores, and positive symptom scores that were intermediate to that of non-patients and patients with psychotic disorders (mood disorders: beta = 0.53, 95 % CI: 0.39-0.68; anxiety disorders: beta = 0.22, 95 % CI: 0.04-0.39). The CAPE distress score adjusted for the corresponding frequency score was not significantly different between the patient groups, but compared to the general population, patient status did contribute significantly to the level of distress. DISCUSSION: Patients with anxiety and mood disorders had elevated scores on positive psychosis items, indicating that expression of psychosis in non-psychotic disorders is common. The finding of elevated scores of the patient groups on all three dimensions compared to non-patients suggests that the psychopathology associated with psychotic disorders varies quantitatively across DSM-IV categories.

Adult↗
PubMed2003

Emotional reactivity to daily life stress in psychosis and affective disorder: an experience sampling study.

OBJECTIVE: To investigate the emotional reactivity to small disturbances in daily life in patients with non-affective psychosis (NAP), bipolar disorder (BD) and major depression [major depressive disorder (MDD)]. METHOD: Forty-two patients with NAP, 38 with BD, 46 with MDD, and 49 healthy controls were studied with the experience sampling method to assess (i) appraised subjective stress of small disturbances in daily life and (ii) emotional reactivity, reflected in changes in positive affect (PA) and negative affect (NA). RESULTS: Multilevel regression analyses showed an increase in NA in MDD, a decrease in PA in BD and both an increase in NA and a decrease in PA in NAP in association with the subjectively stressful situations, compared with the control subjects. CONCLUSION: Individuals with NAP, MDD and BD display differences in emotional stress reactivity. Type of mood disorder may exert a pathoplastic effect on emotional reactivity in individuals with MDD and BD. Individuals with NAP may be most vulnerable to the effects of daily life stress.

Activities of Daily Living↗
PubMed2002

Assessment of hepatic perfusion parameters with dynamic MRI.

Quantification of hepatic perfusion parameters greatly contributes to the assessment of liver function. The purpose of this study was to describe and validate the use of dynamic MRI for the noninvasive assessment of hepatic perfusion parameters. The signal from a fast T(1)-weighted spoiled gradient-echo sequence preceded by a nonslice-selective 90 degrees pulse and a spoiler gradient was calibrated in vitro with tubes filled with various gadolinium concentrations. Dynamic images of the liver were obtained after intravenous bolus administration of 0.05 mmol/kg of Gd-DOTA in rabbits with normal liver function. Hepatic, aortic, and portal venous signal intensities were converted to Gd-DOTA concentrations according to the in vitro calibration curve and fitted with a dual-input one-compartmental model. With MRI, hepatic blood flow was 100 +/- 35 mL min(-1) 100 mL(-1), the arterial fraction 24 +/- 11%, the distribution volume 13.0 +/- 3.7%, and the mean transit time 8.9 +/- 4.1 sec. A linear relationship was observed between perfusion values obtained with MRI and with radiolabeled microspheres (r = 0.93 for hepatic blood flow [P < 0.001], r = 0.79 for arterial blood flow [P = 0.01], and r = 0.91 for portal blood flow [P < 0.001]). Our results indicate that hepatic perfusion parameters can be assessed with dynamic MRI and compartmental modeling.

Animals↗
PubMed2001

Correlates of autobiographical memory specificity: the role of depression, anxiety and childhood trauma.

The present study examined the role of childhood trauma, major depressive disorder (MDD), and anxiety disorder (AD) in overgeneral autobiographical memory. Ninety-three outpatients and 24 healthy controls completed a childhood trauma questionnaire and an autobiographical memory test (AMT). Results showed that MDD diagnosis rather than trauma history predicted AMT-performance. Memory specificity was not related to AD diagnosis, recovered MDD, or self-rated depression severity. The present findings cast doubts on theories that emphasize the role of childhood trauma in overgeneral autobiographical memory.

Adult↗
PubMed2000

Palaeotemperature reconstruction from noble gases in ground water taking into account equilibration with entrapped air

Noble-gas concentrations in ground water have been used as a proxy for past air temperatures, but the accuracy of this approach has been limited by the existence of a temperature-independent component of the noble gases in ground water, termed 'excess air' whose origin and composition is poorly understood. In particular, the evidence from noble gases in a Brazilian aquifer for a cooling of more than 5 C in tropical America during the Last Glacial Maximum has been called into question. Here we propose a model for dissolved gases in ground water, which describes the formation of excess air by equilibration of ground water with entrapped air in quasi-saturated soils. Our model predicts previously unexplained noble-gas data sets, including the concentration of atmospheric helium, and yields consistent results for the non-atmospheric helium isotopes that are used for dating ground water. Using this model of excess air, we re-evaluate the use of noble gases from ground water for reconstructing past temperatures. Our results corroborate the inferred cooling in Brazil during the Last Glacial Maximum, and indicate that even larger cooling took place at mid-latitudes.

Journal Article↗
PubMed2000

Electrolyte and other blood serum abnormalities in normal weight bulimia nervosa: evidence for sampling bias.

OBJECTIVE: Sampling bias due to research settings might be responsible for reported high prevalence rates of electrolyte and serum abnormalities in bulimia nervosa. The aim of this study was to investigate the prevalence of electrolyte and other serum abnormalities in bulimia nervosa patients with normal weight seeking treatment in a community mental health center. METHOD: Diagnostic evaluations and laboratory tests were done for a consecutive series of 31 patients meeting DSM-III-R criteria for bulimia nervosa. RESULTS: The duration and clinical severity of the eating disorder were considerable and psychiatric comorbidity was high. None of the subjects showed electrolyte abnormalities. Hypomagnesemia was found in 9.7% and hypoalbuminemia in 6.4% of the population. The severity of the abnormalities was modest. DISCUSSION: The results suggest that previous reports on electrolyte abnormalities in bulimia nervosa were affected by sampling bias. Based on the results, there is no indication to perform routinely laboratory studies in ambulatory patients with normal weight.

Adolescent↗
PubMed1998

A rapid method for simultaneous detection of phenotypic resistance to inhibitors of protease and reverse transcriptase in recombinant human immunodeficiency virus type 1 isolates from patients treated with antiretroviral drugs.

Combination therapy with protease (PR) and reverse transcriptase (RT) inhibitors can efficiently suppress human immunodeficiency virus (HIV) replication, but the emergence of drug-resistant variants correlates strongly with therapeutic failure. Here we describe a new method for high-throughput analysis of clinical samples that permits the simultaneous detection of HIV type 1 (HIV-1) phenotypic resistance to both RT and PR inhibitors by means of recombinant virus assay technology. HIV-1 RNA is extracted from plasma samples, and a 2.2-kb fragment containing the entire HIV-1 PR- and RT-coding sequence is amplified by nested reverse transcription-PCR. The pool of PR-RT-coding sequences is then cotransfected into CD4+ T lymphocytes (MT4) with the pGEMT3deltaPRT plasmid from which most of the PR (codons 10 to 99) and RT (codons 1 to 482) sequences are deleted. Homologous recombination leads to the generation of chimeric viruses containing PR- and RT-coding sequences derived from HIV-1 RNA in plasma. The susceptibilities of the chimeric viruses to all currently available RT and/or PR inhibitors is determined by an MT4 cell-3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide-based cell viability assay in an automated system that allows high sample throughput. The profile of resistance to all RT and PR inhibitors is displayed graphically in a single PR-RT-Antivirogram. This assay system facilitates the rapid large-scale phenotypic resistance determinations for all RT and PR inhibitors in one standardized assay.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Interpretation of flow encoding and quantification in MRI: time domain versus frequency domain.

The traditional approach to flow effects in MRI is based on the gradient moment expansion. Recently, we have presented an alternative description by using linear response theory: the distortions of the velocity waveform induced by the gradient waveforms were analyzed in the frequency domain on the basis of the transfer function. In the present paper, we perform an analysis of flow encoding and quantification in the time domain, on the basis of the impulse response. The analysis shows that flow encoding should be interpreted as a weighted averaging process. Instantaneous flow encoding is determined by the centroid of the impulse response, but care should be taken regarding the physical meaning of the instant of encoding. The relationship of this approach to the frequency domain and gradient moment expansion approaches is clarified. By way of example, some interesting applications are investigated: asymmetrical phase encoding gradients to minimize misregistration and oscillating read-out gradients for flow quantification. A variety of new applications are expected to derive from the combination of both the time and frequency domains.

Magnetic Resonance Imaging↗
PubMed1995

Time resolved flow quantification with MRI using phase methods: a linear systems approach.

Phase-related unsteady (pulsatile) flow effects in MRI have been studied by means of linear response theory. These flow effects can be described in the frequency domain: the influence of the gradients on the phase shift is described by a transfer function, the spectrum of the gradient being the determining factor. An analysis of this transfer function is shown to provide information about the process of flow encoding: instant of encoding, induced distortions and how they are related to the gradient waveform. The connection with the traditional description in terms of the gradient moment expansion has also been investigated and clarified. This approach was applied to study the response of two time-resolved flow quantification techniques (Fourier flow method and phase mapping) by analyzing their amplitude and phase transfer functions. By simulation it is shown that a better interpretation of the measured velocity waveform is obtained and that Fourier analysis in combination with a correction by the inverse transfer function results in an accurate reconstruction of the velocity waveform studied.

Algorithms↗
PubMed1986

Myelography using iohexol (Omnipaque).

Myelography was performed in 30 patients using iohexol (Omnipaque) 240 mg I/ml for lateral C1C2 injections, or iohexol 300 mg I/ml for lumbar injections. The dose varied from 3 to 10 ml. The patients were observed for 48 h for possible adverse reactions. A complete neurological examination was repeated 24h after the investigation, and EEG recordings 3-24h after the investigation. Adverse reactions occurred in 4 patients, minor EEG changes occurred in 1 patient, and slight changes in the neurological status were seen in 2 patients.

Adult↗
PubMed1983

Treatment of vaginal candidosis with oral ketoconazole.

Results with ketoconazole were studied in 281 non-pregnant patients with acute and chronic Candida-vaginitis. Several dose regimens were evaluated. The 5-day regimens (200 mg b.i.d. or 400 mg once daily) seem to be the most appropriate schedules in this infection. Side effects were minor. Relapse rates are not different from those, historically known, with topical antifungals.

Administration, Oral↗
PubMed1983

Iopamidol for myelography. A clinical trial with a new non-ionic contrast medium.

289 myelographies with the non-ionic, water-soluble, contrast medium iopamidol were performed. These were subdivided into 153 lumbar, 49 ascending thoracocervical and 87 cervical myelographies. For the latter a lateral C1-C2 puncture was used. The iodine concentration given was 200 mg/ml for the lumbar examinations and 300 mg/ml for the cervical and thoraco-cervical examinations. The total iodine never exceeded 3 g. Image quality is not different to metrizamide of equal iodine concentration. Adverse reactions did not exceed those known for metrizamide. Mild and transient side effects occured in 45%.

Clinical Trials as Topic↗
PubMed1980

A shortened regime for the treatment of vulvovaginal candidosis with a new presentation of miconazole.

A new presentation of miconazole, in the form of soft gelatin capsules for intravaginal use, gave considerable therapeutic success in the treatment of vulvovaginal candidosis. Mycological cure rates greater than 85% and clinical cure rates greater than 90% were achieved by treatment with 7 miconazole capsules, regardless of whether these were used daily for 7 days or twice daily for 3 1/2 days. The new formulation seems to possess the dual advantage of ease of application and shorter duration of treatment.

Adolescent↗