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Biomedical subjects

P Bartenstein

Publications and source records attributed to P Bartenstein.

At least 73 records · Page 4Linked to original sources
PubMed1999

Imaging of lung cancer with fluorine-18 fluorodeoxyglucose: comparison of a dual-head gamma camera in coincidence mode with a full-ring positron emission tomography system.

Dual-head gamma cameras operated in coincidence mode are a new approach for tumour imaging using fluorine-18 fluorodeoxyglucose (FDG). The aim of this study was to assess the diagnostic accuracy of such a camera system in comparison with a full-ring positron emission tomography (PET) system in patients with lung cancer. Twenty-seven patients (1 female, 26 males, age 62+/-9 years) with lung cancer or indeterminate pulmonary nodules were studied on the same day with a full-ring PET scanner (Siemens ECAT EXACT) and a coincidence gamma camera system (ADAC Vertex MCD). Sixty minutes after injection of 185-370 MBq FDG, a scan of the chest was performed with the full-ring system. Approximately 2 h p.i., the coincidence camera study was performed. Coincidence gamma camera (CGC) and PET images with (PETac) and without attenuation correction (PETnac) were analysed independently by two blinded observers. In addition, FDG uptake in primary tumours and involved lymph nodes was quantified relative to normal contralateral lung (T/L ratios). All primary tumours were histologically proven. The lymph node status was histologically determined in 23 patients. In four patients, no lymph node sampling was performed because of extensive disease or concurrent illnesses. In the 27 patients, 25 primary lung cancers and two metastatic lesions were histologically diagnosed. The number of coincidences per centimetre axial field of view was 3.33+/-0. 93x10(5) for the CGC and 1.09+/-0.36x10(6) for the dedicated PET system. All primary tumours (size: 4.6+/-2.6 cm) were correctly identified in the CGC and dedicated PET studies. T/L ratios were 4. 7+/-2.5 for CGC and 6.9+/-2.8 for PETnac (P <0.001). Histopathological evaluation revealed lymph node metastases in 11 of 88 sampled lymph node stations (size: 2.3+/-1.0 cm). All lymph node metastases were identified in the PETac studies, while PETnac detected 10/11 and CGC 8/11. For positive lymph nodes that were visible in CGC and PETnac studies, T/L ratios were 3.7+/-2.3 for CGC and 6.6+/-3.1 for PETnac (P=0.02). The diameters of false-negative lymph nodes in the CGC studies were 0.75, 1.5 and 2 cm. False-positive FDG uptake in lymph nodes was found in two patients with all three imaging methods. For all lesions combined, T/L ratios in CGC relative to PETnac studies decreased significantly with decreasing lesion size (r=0.62; P<0.001). In conclusion, compared with a full-ring PET system the sensitivity of CGC imaging for detection of lung cancer is limited by a lower image contrast which deteriorates with decreasing lesion size. Nevertheless, the ability of CGC imaging to detect pulmonary lesions with a diameter of at least 2 cm appears to be similar to that of a full-ring system. Both systems provide a similar specificity for the evaluation of lymph node involvement.

Aged↗
PubMed1999

Supraspinal metabolic activity changes in the rat during adjuvant monoarthritis.

Pain is a multi-dimensional experience including sensory-discriminative and affective-motivational components. The attribution of such components to a corresponding cerebral neuronal substrate in the brain refers to conclusions drawn from electrical brain stimulation, lesion studies, topographic mappings and metabolic imaging. Increases in neuronal metabolic activity in supraspinal brain regions, suggested to be involved in the central processing of pain, have previously been shown in various animal studies. The present investigation is the first to describe supraspinal structures which show increased metabolic activity during ongoing monoarthritic pain at multiple time-points. Experimental chronic monoarthritis of a hindlimb induced by complete Freund's adjuvant is one of the most used models in studies of neuronal plasticity associated with chronic pain. Such animals show typical symptoms of hyperalgesia and allodynia for a prolonged period. Metabolic activity changes in supraspinal brain regions during monoarthritis were assessed using the quantitative [14C]-2deoxyglucose technique at two, four, 14 days of the disease and, furthermore, in a group of 14-day monoarthritic rats which were mechanically stimulated by repeated extensions of the inflamed joint. Local glucose utilization was determined ipsi- and contralateral to the arthritic hindpaw in more than 50 brain regions at various supraspinal levels, and compared with saline-injected controls. At two and 14 days of monoarthritis significant bilateral increases in glucose utilization were seen in many brain structures, including brainstem, thalamic, limbic and cortical regions. Within the brainstem, animals with 14-day monoarthritis showed a higher number of regions with increased metabolic activity compared with two days. No differences between ipsi- and contralateral sides were detected in any of the experimental groups. Average increases ranged from 20 to 40% compared with controls and maximum values were detected in specific brain regions, such as the anterior pretectal nucleus, the anterior cingulate cortex and the nucleus accumbens. Interestingly, at four days of monoarthritis, the glucose utilization values were in the control range in almost all regions studied. Moreover, in monoarthritic rats receiving an additional noxious mechanical stimulation, the rates of glucose utilization were also comparable to controls in all brain areas investigated. Such patterns of brain metabolic activity agreed with concomitant changes in the lumbar spinal cord, described in the accompanying report. The present data show that a large array of supraspinal structures displays elevated metabolic activity during painful monoarthritis, with a non-linear profile for the time-points investigated. This observation most probably reflects mechanisms of transmission and modulation of nociceptive input arising from the monoarthritis and accompanying its development.

Analysis of Variance↗
PubMed1999

Metabolic activity changes in the rat spinal cord during adjuvant monoarthritis.

The development of chronic pain is associated with activity-dependent plastic changes in neuronal structures in the peripheral and central nervous system. In order to investigate the time-dependent processing of afferent noxious stimuli in the spinal cord we employed the quantitative autoradiographic 2-deoxyglucose technique in a model of chronic monoarthritic pain in the rat. Spinal metabolic activity was determined at various time-points (two, four and 14 days) after the injection of complete Freund's adjuvant into the left tibiotarsal joint. In addition, the effect of acute noxious mechanical stimulation of the arthritic joint was investigated at 14 days of monoarthritis. Local glucose utilization was determined in lumbar segments L2-L5, ipsi- and contralateral to the inflamed hindpaw, and compared with saline-injected controls. In general, monoarthritic animals had bilaterally increased metabolic activity in all laminae of the spinal cord. Detailing the time-course showed that in rats with two days of monoarthritis metabolic activity was significantly increased to a similar extent on both sides of all spinal laminae. In contrast, at four days, glucose utilization in deep laminae of the dorsal horn (laminae V-VI), the central gray area (laminae X) and the ventral horn (laminae VII-IX) tended to return to control levels. At 14 days of monoarthritis, however, metabolic activity showed a further increase in all laminae of the spinal cord. This increase was more pronounced on the side ipsilateral to inflammation, reaching 65% above corresponding control levels in laminae V, VI. Animals with 14 days of monoarthritis which were subjected to mechanical noxious stimulation of the arthritic joint displayed clear behavioral signs of acute pain. Although in this group metabolic activity was above control levels, it was lower than in animals with 14 days of monoarthritis that were not additionally stimulated. The data show not only a general increase of spinal cord metabolic activity during the time-course of the development of a chronic pain state, but also show a region-specific non-linear time profile. This may reflect the complexity of transducing and suppressive transmitter systems involved in the central processing of ongoing pain.

Animals↗
PubMed1999

Sensory processing in Parkinson's and Huntington's disease: investigations with 3D H(2)(15)O-PET.

There is conjoining experimental and clinical evidence supporting a fundamental role of the basal ganglia as a sensory analyser engaged in central somatosensory control. This study was aimed at investigating the functional anatomy of sensory processing in two clinical conditions characterized by basal ganglia dysfunction, i.e. Parkinson's and Huntington's disease. Based on previously recorded data of somatosensory evoked potentials, we expected deficient sensory-evoked activation in cortical areas that receive modulatory somatosensory input via the basal ganglia. Eight Parkinson's disease patients, eight Huntington's disease patients and eight healthy controls underwent repetitive H(2)(15)O-PET activation scans during two experimental conditions in random order: (i) continuous unilateral high-frequency vibratory stimulation applied to the immobilized metacarpal joint of the index finger and (ii) rest (no vibratory stimulus). In the control cohort, the activation pattern was lateralized to the side opposite to stimulus presentation, including cortical [primary sensory cortex (S1); secondary sensory cortex (S2)] and subcortical (globus pallidus, ventrolateral thalamus) regional cerebral blood flow (rCBF) increases (P < 0.001). Between-group comparisons (P < 0.01) of vibration-induced rCBF changes between patients and controls revealed differences in central sensory processing: (i) in Parkinson's disease, decreased activation of contralateral sensorimotor (S1/M1) and lateral premotor cortex, contralateral S2, contralateral posterior cingulate, bilateral prefrontal cortex (Brodmann area 10) and contralateral basal ganglia; (ii) in Huntington's disease, decreased activation of contralateral S2, parietal areas 39 and 40, and lingual gyrus, bilateral prefrontal cortex (Brodmann areas 8, 9, 10 and 44), S1 (trend only) and contralateral basal ganglia; (iii) in both clinical conditions relative enhanced activation of ipsilateral sensory cortical areas, notably caudal S1, S2 and insular cortex. Our data show that Parkinson's disease and Huntington's disease, beyond well-established deficits in central motor control, are characterized by abnormal cortical and subcortical activation on passive sensory stimulation. Furthermore, the finding that activation increases in ipsilateral sensory cortical areas may be interpreted as an indication of either altered central focusing and gating of sensory impulses, or enhanced compensatory recruitment of associative sensory areas in the presence of basal ganglia dysfunction. Altered sensory processing is thought to contribute to pertinent motor deficits in both conditions.

Adult↗
PubMed1999

18F-FDG PET studies in patients with extratemporal and temporal epilepsy: evaluation of an observer-independent analysis.

UNLABELLED: The aim of this study was to evaluate an observer-independent analysis of 18F-fluorodeoxyglucose (FDG) PET studies in patients with temporal or extratemporal epilepsy. METHODS: Twenty-seven patients with temporal epilepsy and 22 patients with extratemporal epilepsy were included in the study. All patients with temporal epilepsy and 7 patients with extratemporal epilepsy underwent surgical treatment. In patients who showed significant postoperative improvement (temporal, n = 23; extratemporal, n = 6), the epileptogenic focus was assumed to be located in the area of surgical resection. In extratemporal epilepsy patients who did not undergo surgery, the focus localization was determined using a combination of semiology, ictal and interictal electroencephalography, [99mTc]ethyl cysteinate dimer SPECT, MRI and [11C]flumazenil PET. Visual analysis was performed by two experienced and two less experienced blinded observers using sagittal, axial and coronal images. In the automated analysis after anatomic standardization and generation of three-dimensional stereotactic surface projections (SSPs), a pixelwise comparison of 18F-FDG uptake with an age-matched reference database (n = 20) was performed, resulting in z score images. Pixels with the maximum deviation were detected, summarized and attached to one of 20 predefined surface regions of interest. For comparison with 18F-FDG PET and MR images, three-dimensional overlay images were generated. RESULTS: In patients with temporal epilepsy, the sensitivity was comparable for visual and observer-independent analysis (three-dimensional SSP 86%, experienced observers 86%-90%, less experienced observers 77%-86%). In patients with extratemporal epilepsy, three-dimensional SSP showed a significantly higher sensitivity in detecting the epileptogenic focus (67%) than did visual analysis (experienced 33%-38%, each less experienced 19%). In temporal lobe epilepsy, there was moderate to good agreement between the localization found with three-dimensional SSP and the different observers. In patients with extratemporal epilepsy, there was a high interobserver variability and only a weak agreement between the localization found with three-dimensional SSP and the different observers. Although three-dimensional SSP detected multiple lesions more often than visual analysis, the determination of the highest deviation from the reference database allowed the identification of the epileptogenic focus with a higher accuracy than subjective criteria, especially in extratemporal epilepsy. CONCLUSION: Three-dimensional SSP increases sensitivity and reduces observer variability of the analysis of 18F-FDG PET images in patients with extratemporal epilepsy and is, therefore, a useful tool in the evaluation of this patient group. The benefit of this analytical approach in patients with temporal epilepsy is less apparent.

Adolescent↗
PubMed1999

Central pain after pontine infarction is associated with changes in opioid receptor binding: a PET study with 11C-diprenorphine.

Using 18F-fluorodeoxyglucose and 11C-diprenorphine positron emission tomography (PET), we investigated alterations in glucose metabolism and opioid receptor binding in a patient with central poststroke pain, which developed after a small pontine hemorrhagic infarction. In comparison with normal databases, reduced 11C-diprenorphine binding was more accentuated than the hypometabolism on the lateral cortical surface contralateral to the symptoms, and a differential abnormal distribution between the tracers was seen in pain-related central structures. These results show that 11C-diprenorphine PET provides unique information for the understanding of central poststroke pain.

Adult↗
PubMed1999

[Role of positron emission tomography (PET) and single photon emission tomography (SPECT) in so-called "multiple chemical sensitivity"].

Functional imaging with SPECT and PET is increasingly used to prove evidence for the existence of a syndrome "Multiple Chemical Sensitivity" (MCS) and plays a major role in legal trials to justify compensation for the exposure to solvents. This paper critically reviews the literature on the use of SPECT and PET for the determination of MCS. The authors come to the conclusion that the current data are not sufficient to justify the claim of the existence of such a syndrome. The low specificity of the observed PET and especially SPECT-findings makes it very difficult to establish a cause-result relationship and therefore makes the use of these methods in legal trials on this issue doubtful.

Humans↗
PubMed1998

The value of F-18-fluorodeoxyglucose PET for the 3-D radiation treatment planning of malignant gliomas.

PURPOSE: The aim of the study was to determine the impact of positron emission tomography using the glucose analogue fluorine-18-fluorodeoxyglucose (FDG-PET) on the delineation of the target volume in three-dimensional radiation treatment planning of primary brain tumors. METHODS AND MATERIALS: In 18 patients with histologically proven (8x biopsy, 10x subtotal resection) primary brain tumors (8 astrocytomas grade III, one mixed glioma grade III, and 9 glioblastomas), magnetic resonance imaging (MRI) with gadolinium-DTPA and FDG-PET were performed in radiation treatment position within the same week. A computer program was developed for fusion of the PET and MR images. On corresponding axial slices, FDG uptake was compared to contrast enhancement in T1-weighted and to signal hyperintensity in T2-weighted MR images. Based on PET and MRI data, three-dimensional treatment planning was performed. All patients underwent linear accelerator (LINAC) radiotherapy. RESULTS: In MRI, all tumors and the surrounding edema were visible as hyperintense lesions in the T2-weighted images. 17/18 tumors showed contrast enhancement. In FDG-PET, 16 tumors showed hypermetabolism compared to normal white matter, whereas only 8/18 tumors showed hypermetabolism compared to normal gray matter. White matter edema was associated with decreased FDG uptake in all patients. The area of increased FDG uptake correlated closely with contrast enhancement, only in one case the volume of increased FDG uptake was larger than the area of contrast enhancement. Mean tumor volumes obtained by MRI T1 + Gd, T2, and PET were 30, 106, and 10 ml, respectively. Survival was comparable to data in the literature with a 1-year survival of 39% and a median survival of 310 days. CONCLUSION: Only in a minority of patients did FDG-PET provide additional information for radiation treatment planning. This is mainly caused by the high intensity of FDG uptake in normal brain tissue. PET may be of greater value in the definition of regions that should obtain a radiation dose boost.

Adult↗
PubMed1998

Imaging brain activation induced by long trains of repetitive transcranial magnetic stimulation.

Using positron emission tomography (PET), we measured the relative changes in regional cerebral metabolic rate of glucose (rCMRglc) during 2 Hz repetitive transcranial magnetic stimulation (rTMS) of the left sensorimotor cortex (SM1) and during imitation of rTMS-induced arm movements. Such stimulation caused an rCMRglc increase of about 8% within the SM1. The relative rCMRglc increase within SM1 was significantly greater in magnitude and larger in area during voluntary imitation of rTMS-induced arm movements. Moreover, the rostral part of the SMA was significantly more activated by voluntary movements than during rTMS. Combining rTMS and PET has the potential to visualize rTMS-related net brain activation, and may open up new possibilities for functional network analysis by comparing willed brain activation with electromagnetic brain activation.

Adult↗
PubMed1998

[Tau protein. A potential biological indicator for early detection of Alzheimer disease].

In 40 patients with Alzheimer's disease (AD), in 5 patients with non-AD dementia and in 36 cognitively normal controls the concentration of protein tau was determined in the cerebrospinal fluid (CSF). Of the AD patients, 19 were very mildly demented (MMSE score from 25 to 28). Even in these patients, CSF tau was significantly more elevated than in controls. In the non-AD patients protein tau was less increased. Among the AD patients there was no association between CSF tau and severity of cognitive impairment or deficit in cerebral blood flow, determined by SPECT. Our findings suggest that CSF tau may be elevated even at the predementia stage of AD and be useful as a biological marker for the early recognition of the disease.

Adult↗
PubMed1998

[Clinical value of positron emission tomography in neuromedicine. Position paper on results of an interdisciplinary consensus conference].

To date, positron emission tomography (PET) is the most powerful method for the in-vivo investigation of human brain metabolism. Besides extensive application of this technology in the neurosciences, PET is also being increasingly used as a clinical tool. However, despite its acceptance in clinical practice a major obstacle is its high costs. The present article reviews the literature on the clinical use of PET in neurology, neurosurgery, and psychiatry in order to substantiate the clinical indications for PET in these specialties as established by an interdisciplinary conference.

Brain Diseases↗
PubMed1998

Ictal technetium-99m ethyl cysteinate dimer single-photon emission tomographic findings and propagation of epileptic seizure activity in patients with extratemporal epilepsies.

Although ictal single-photon emission tomography (SPET) with technetium-99m ethyl cysteinate dimer (ECD) has a well-established role in the diagnostic evaluation of patients with temporal lobe epilepsy who are being considered for epilepsy surgery, its use in cases of extratemporal epilepsy is still limited. We investigated the influence of the propagation of extratemporal epileptic seizure activity on the regional increase in cerebral blood flow, which is usually associated with epileptic seizure activity. Forty-two consecutive patients with extratemporal epilepsies were prospectively evaluated. All patients underwent ictal SPET studies with simultaneous electroencephalography (EEG) and video recordings of habitual seizures and imaging studies including cranial magnetic resonance imaging and positron emission tomography with 2-[18F]-fluoro-2 deoxy-d-glucose. Propagation of epilptic seizure activity (PESA) was defined as the absence of hyperperfusion on ictal ECD SPET in the lobe of seizure onset, but its presence in another ipsilateral or contralateral lobe. Observers analysing the SPET images were not informed of the other results. PESA was observed in 8 of the 42 patients (19%) and was ipsilateral to the seizure onset in five (63%) of these eight patients. The time between clinical seizure onset and injection of the ECD tracer ranged from 14 to 61 s (mean 34 s). Seven patients (88%) with PESA had parieto-occipital epilepsy and one patient had a frontal epilepsy. PESA was statistically more frequent in patients with parieto-occipital lobe epilepsies (58%) than in the remaining extratemporal epilepsy syndromes (3%) (P<0.0002). These findings indicate that ictal SPET studies require simultaneous EEG-video recordings in patients with extratemporal epilepsies. PESA should be considered when interpreting ictal SPET studies in these patients. Patients with PESA are more likely to have parieto-occipital lobe epilepsy than seizure onset in other extratemporal regions.

Adolescent↗
PubMed1998

Reciprocal inhibitory visual-vestibular interaction. Visual motion stimulation deactivates the parieto-insular vestibular cortex.

The vestibular system--a sensor of head accelerations--cannot detect self-motion at constant velocity and thus requires supplementary visual information. The perception of self-motion during constant velocity movement is completely dependent on visually induced vection. This can be linear vection or circular vection (CV). CV is induced by large-field visual motion stimulation during which the stationary subject perceives the moving surroundings as being stable and himself as being moved. To determine the unknown cortical visual-vestibular interaction during CV, we conducted a PET activation study on CV in 10 human volunteers. The PET images of cortical areas activated during visual motion stimulation without CV were compared with those with CV. Hitherto, CV was explained neurophysiologically by visual-vestibular convergence with activation of the vestibular nuclei, thalamic subnuclei and vestibular cortex. If CV were mediated by the vestibular cortex, one would expect that an adequate visual motion stimulus would activate both the visual and vestibular cortex. Contrary to this expectation, it was shown for the first time that visual motion stimulation with CV not only activates a medial parieto-occipital visual area bilaterally, separate from middle temporal/medial superior temporal areas, it also simultaneously deactivates the parieto-insular vestibular cortex. There was a positive correlation between the perceived intensity of CV and relative changes in regional CBF in parietal and occipital areas. These findings support a new functional interpretation: reciprocal inhibitory visual-vestibular interaction as a multisensory mechanism for self-motion perception. Inhibitory visual-vestibular interaction might protect visual perception of self-motion from potential vestibular mismatches caused by involuntary head accelerations during locomotion, and this would allow the dominant sensorial weight during self-motion perception to shift from one sensory modality to the other.

Adult↗
PubMed1998

Tau protein in cerebrospinal fluid is significantly increased at the earliest clinical stage of Alzheimer disease.

The concentration of tau protein in cerebrospinal fluid (CSF) was determined in 40 patients with clinically diagnosed probable Alzheimer disease (AD) and in 36 cognitively healthy controls. A significant increase of CSF tau was found in the AD patients, even in 19 subjects with very mild dementia as defined by a Mini-Mental State Examination score of 25 and above. Using a cutoff value of 260 pg/mL the sensitivity of elevated tau was 0.89, the specificity was 0.97, and the proportion of correctly allocated cases was 95%. In the AD groups there were no significant associations between CSF tau level and age, age at onset, duration of illness, apolipoprotein E genotype, severity of cognitive impairment, or deficit in regional cerebral blood flow as measured using 99Tm-ethyl cystein dimer single photon emission computed tomography. The findings demonstrate that CSF tau is significantly increased at the earliest clinical stage of AD and shows only minimal overlap with age-matched cognitively healthy controls. This finding suggests that CSF tau could be a biological marker of AD even before dementia has developed.

Adult↗
PubMed1998

PET and the effects of aging and neurodegeneration on brain function: basic principles.

In the first part of a three-part series on the role of positron emission tomography (PET) in the study of neurodegeneration and aging in the human brain, the authors review the historical development of the in vivo measurement of brain function resulting in recent advances in PET technology. An overview is presented of the physical principles of PET scanning and the inherent limitations of this technology to set the basis for the critical interpretation of PET data presented in the second and third parts and in the ever-increasing number of PET studies on the brain in different physiological and pathological conditions. Finally, the authors describe the ability to measure in vivo regional cerebral glucose metabolism with [(18)F]-FDG PET, regional cerebral blood flow and the distribution and binding capacity of neuroreceptors. They conclude with future perspectives of PET technology and its relevance, especially for neuropsychiatric research.

Journal Article↗
PubMed1997

Effects on bone mineral density of low-dosed oral contraceptives compared to and combined with physical activity.

A cross-sectional study was designed to examine the influence of exercise compared to and in combination with low-dosed oral contraceptives (OCs) on bone mineral density (BMD). One hundred twenty-eight women (20 to 35 years of age) were assigned to four groups with respect to the years of exercise and OC intake. Influence factors were determined by a detailed questionnaire and interview. BMD for L2-4 and the femoral neck was assessed by DXA. The highest BMD values were found in the group of women characterized by long-term exercise (9.45 +/- 4.32 yr) and short use of OC (1.6 +/- 1.69 yr). No beneficial effect of exercise on BMD was found in the group with a long exercise period (10.4 +/- 4.14 yr) and long-term intake of OC (8.2 +/- 4.14 yr). Differences in mean BMD values between the two groups were significant in all regions assessed (p < 0.05). No differences in mean BMD were found in the groups with short-term exercise but long or brief histories of OC. The question arises as to whether active women taking low-dosed OC at an earlier age will develop an adequate BMD.

Absorptiometry, Photon↗
PubMed1997

Central motor processing in Huntington's disease. A PET study.

Repeated PET cerebral blood flow measurements using H2(15)O were performed in 13 patients with confirmed Huntington's disease and nine age-matched controls. The activation paradigm consisted of an externally triggered finger opposition task (1.5 Hz) with the dominant hand, the control condition being the auditory input. In the patients with Huntington's disease, impaired activity of the striatum and its frontal motor projection areas (rostral supplementary motor area, anterior cingulate and premotor cortex) could be demonstrated along with enhanced activity mainly in parietal areas during movement. The results suggest that the pathology of Huntington's disease causes impairment of the output part of the basal ganglia-thalamo-cortical motor circuit and may induce a compensatory recruitment of additional accessory motor pathways involving the parietal cortex.

Adult↗