Biomedical subjects

G Bormans

Publications and source records attributed to G Bormans.

At least 37 records · Page 2Linked to original sources

PubMed1999

Additional value of whole-body positron emission tomography with fluorine-18-2-fluoro-2-deoxy-D-glucose in recurrent colorectal cancer.

PURPOSE: To assess the additional value of the whole-body [18F]-2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) scan as a staging modality complementing conventional diagnostic methods (CDM) in patients suspected of having recurrent colorectal adenocarcinoma. PATIENTS AND METHODS: In 103 patients, the discordances between FDG-PET and CDM results were identified and related to the final diagnosis obtained by histopathology or clinical follow-up (> 1 year). All FDG-PET studies were reviewed with full knowledge of the CDM findings. RESULTS: In a region-based analysis, discordances between CDM and FDG-PET findings were found in 40 of 412 regions (10%). In these, FDG-PET had additional diagnostic value in 14 of 16 locoregional, six of seven hepatic, seven of eight abdominal, and eight of nine extra-abdominal regions. In a patient-based analysis, CDM categorized a subgroup of 60 patients as having resectable recurrent disease limited to the liver (n = 37) or locoregional region (n = 23). In 13 of these patients, there were discordant FDG-PET findings, detecting additional tumor sites in nine patients and excluding disease in three patients and yielding an additional diagnostic value in 20% of the patients. A second subgroup consisted of 13 patients with inconclusive CDM findings (n = 5) or with elevated plasma carcinoembryonic antigen levels and an otherwise negative conventional work-up (n = 8). In these patients, FDG-PET results were correct in eight of nine discordances, yielding a positive additional diagnostic value in 62% of the patients. CONCLUSION: Whole-body FDG-PET can have a clear impact on the therapeutic management in the follow-up of patients with colorectal cancer.

Abdominal Neoplasms↗

PubMed1998

Measurement of skeletal flow with positron emission tomography and 18F-fluoride in femoral head osteonecrosis.

Positron emission tomography (PET) with 18F-fluoride was utilized to determine the regional blood flow to the femoral head in early osteonecrosis. Five patients with a history of unilateral hip trauma and a normal contralateral side were selected. Skeletal flow and fluoride uptake in the abnormal and normal hips were compared directly, and the relation between bone blood flow and final outcome, i.e., surgical replacement or conservative treatment, was evaluated. In this pilot study, a flow ratio of at least 2 between the abnormal and normal femoral head was necessary to predict a successful outcome with a conservative regimen. A minimum flow of 0.04 ml/min/ml was measured in one patient whose affected femoral head healed conservatively. Our preliminary study indicates that this type of highly technical investigation appears feasible in clinical practice and permits prediction of the outcome depending upon regional skeletal flow measurements in vivo.

Adult↗

PubMed1998

Regions in the human brain activated by simultaneous orientation discrimination: a study with positron emission tomography.

In order to compare regional cerebral activity involved in simultaneous as opposed to successive orientation discrimination, we used positron emission tomography to measure regional cerebral blood flow, in two threefold sets of conditions, in a large number of subjects. The first such triad involved simultaneous orientation discrimination, orientation identification and detection, with all tasks using the same pair of gratings. The second triad consisted of successive orientation discrimination with its corresponding identification and detection tasks. Comparisons between tasks within each triad isolate attention to orientation and, respectively, spatial or temporal comparison. The subtraction of detection from simultaneous discrimination revealed activation of right fusiform, right lingual, left precentral, left cingulate and left temporal cortex, in addition to right insula, cerebellum and left thalamus. Only the fusiform, insular and precentral activations remained when the corresponding identification was subtracted from simultaneous discrimination. In contrast, most of the non-visual activation sites remained when simultaneous discrimination was compared with successive discrimination, which also revealed a left lingual activation. These experiments provide further evidence for task-dependent processing in the human visual system and suggest that the right fusiform cortex is involved in spatial as much as temporal comparisons.

Adult↗

PubMed1997

Positron-emission tomography imaging of long-term shape recognition challenges.

Long-term visual memory performance was impaired by two types of challenges: a diazepam challenge on acquisition and a sensory challenge on recognition. Using positron-emission tomography regional cerebral blood flow imaging, we studied the effect of these challenges on regional brain activation during the delayed recognition of abstract visual shapes as compared with a baseline fixation task. Both challenges induced a significant decrease in differential activation in the left fusiform gyrus, suggesting that this region is involved in the automatic or volitional comparison of incoming and stored stimuli. In contrast, thalamic differential activation increased in response to memory challenges. This increase might reflect enhanced retrieval attempts as a compensatory mechanism for restoring recognition performance.

Adult↗

PubMed1997

Attention to one or two features in left or right visual field: a positron emission tomography study.

In human vision, two features of the same object can be identified concurrently without loss of accuracy. Performance declines, however, when the features belong to different objects in opposite visual fields. We hypothesized that different positron emission tomography activation patterns would reflect these behavioral results. We first delineated an attention network for single discriminations in left or right visual field and then compared this with the activation pattern when subjects divided attention over two features of a single object or over two objects in opposite hemifields. When subjects attended to a single feature, parietal, premotor, and anterior cingulate cortex were activated. These effects were strongest in the right hemisphere and were, remarkably, unaffected by the direction of attention. In contrast, direction of attention affected occipital and frontal activity: right occipital and left lateral frontal activity were higher with attention to the left, whereas right lateral frontal activity was higher with attention to the right. When subjects identified two features of the same object, parietal, premotor, and anterior cingulate activity was enhanced further, predominantly this time in the left hemisphere. Again, there was no direction sensitivity. Direction-sensitive activation of lateral frontal cortex also was increased. Finally, when subjects divided their attention over opposite hemifields, activity in the direction-sensitive occipital and frontal regions fell to a level midway between those seen during exclusively leftward or rightward attention. Thus, the behavioral efficiency with which we attend to multiple features of a single peripheral object is paralleled by enhanced activity in structures generally active during peripheral selective attention as well as in structures that depend on the specific direction of attention, most notably lateral frontal cortex. In addition, in the direction-sensitive regions, dividing attention over hemifields causes a compromise pattern between the extreme levels obtained during unilateral attention.

Adolescent↗

PubMed1997

Evaluation of carbon-11-labelled phenoxy bridged fatty acids for studying myocardial fatty acid metabolism with PET.

A phenylene moiety in the chain of fatty acids was expected to impair metabolic degradation. Three phenoxy-containing [11C]carboxyl-labelled fatty acids were synthesized and evaluated in mice and an in vivo tissue distribution study. Of these three, 1[11C]-3-(p-dodecyloxyphenyl)propionic acid (C12C3) showed the most favourable uptake in the myocardium: 1.2% of the injected dose at 30 min p.i., vs. 0.6% for [11C]palmitate. The metabolic stability of C12C3 and [11C]palmitate was assessed by determining the amount of exhaled [11C]CO2 during a 30-min interval after injection. It was found that the phenoxy moiety in the gamma-position did not prevent the metabolic degradation of C12C3: After 30 min 20.7% of the injected dose was exhaled as [11C]CO2 vs. 12.7% for [11C]palmitate.

Animals↗

PubMed1997

Importance of flow/metabolism studies in predicting late recovery of function following reperfusion in patients with acute myocardial infarction.

AIMS: Positron emission tomographic imaging is known to be a reliable indicator of viable myocardium in chronic heart disease. Its value in acute myocardial infarction has not been studied extensively. METHODS AND RESULTS: Sixty-two patients receiving thrombolytic therapy were studied. Myocardial tissue flow and metabolism were measured at 5 days and 3 months. Recovery of left ventricular function was investigated with echocardiography or radionuclide ventriculography. In eight patients, normal flow was found in the infarct area at 5 days with no significant changes in flow, metabolism or function over the next 3 months. In 54 patients, impaired regional myocardial blood flow in the infarct zone was observed at 5 days. In 39 patients, there was a matching positron emission tomographic pattern, while in 15 the pattern was mismatched. None of the patients with a TIMI flow grade < 3 revealed recovery of left ventricular function. In seven out of 11 patients with TIMI 3 flow and a mismatching pattern, additional angioplasty was performed with functional improvement in six. CONCLUSIONS: Recovery of ventricular function is exclusively found in patients with a TIMI flow grade 3. Patients with a positron emission tomographic mismatching pattern reveal functional recovery only after subsequent angioplasty.

Aged↗

PubMed1997

Human brain activity related to orientation discrimination tasks.

In order to relate regional activity in the human brain to the different components of discrimination tasks, we compared regional cerebral blood flow, measured with positron emission tomography, under four conditions: successive orientation discrimination, orientation identification, detection and passive viewing. By adding successive discrimination and passive viewing at a second, lower rate we were able to investigate the main effects and interaction between task and presentation rate. Four occipital regions--the posterior calcarine region bilaterally, the right lingual gyrus and the right interior occipital cortex--displayed a main effect of presentation rate. Two regions--a right posterolateral occipital region and a right posterior fusiform region--displayed a significant main effect of task. The involvement of this posterior fusiform region in successive discrimination was also revealed by the subtraction of detection from successive discrimination, as was that of the right middle fusiform gyrus. Finally, a more anterior right middle fusiform region was differentially active in successive discrimination compared to identification, suggesting that activity in this region is related to the temporal comparison of orientation.

Adult↗

PubMed1997

Positron emission tomography, magnetic resonance imaging and proton NMR spectroscopy of white matter in multiple sclerosis.

OBJECTIVE: To assess characteristics of MS lesions and normal appearing white matter (NAWM) with various imaging modalities. Glucose metabolism was investigated with FDG-PET, metabolite concentration with proton NMR spectroscopy, and lesion detection with routine brain MRI. METHODS: Thirteen patients were studied in a stable phase of their disease, and two during an acute episode. Nine healthy volunteers served as controls. RESULTS: Three patients had a normal brain MRI, 12 had typical lesions. MR images were registered to the PET planes. Lesions and contra-lateral control areas were analyzed, 10/15 lesions showed relative hyper-metabolism and 2 hypo-metabolism. NAA concentration was significantly decreased in both lesions and NAWM. CONCLUSION: In stable MS, most large lesions have a relatively increased glucose utilization and decreased NAA concentration. NAWM showed a significantly decreased NAA concentration compared to healthy subjects, but no difference in glucose metabolism. Active lesions in acute MS are also hyper-metabolic. This finding opens a new window on the classification of white matter lesions based on glucose utilization.

Acute Disease↗

PubMed1997

Fluoride kinetics of the axial skeleton measured in vivo with fluorine-18-fluoride PET.

UNLABELLED: The aim of this study was to quantify regional bone blood flow and influx rate with PET and [18F]fluoride in patients with metabolic bone disorders. METHODS: Dynamic imaging of the spine or pelvis was performed after administration of 300-370 MBq of 18F-. Plasma clearance of 18F- was determined in blood sampled from the radial artery. A three-compartment model was used to estimate the regional flow and fluoride influx rate. RESULTS: In this preliminary study, fluoride flux (in micromol/min/liter) could be measured regionally. The flux was consistent with the pathophysiology of the studied metabolic disorders and allowed the various disease states to be distinguished. Bone blood flow and influx rate were low in osteoporosis (in the "normal-appearing" bone) and high in Paget's disease. CONCLUSION: With PET and [18F]fluoride, local bone blood flow and fluoride influx rate can be quantified in patients in vivo. Metabolically active zones have an increased influx rate and an accordingly increased flow. In principle, this technique permits classification of bone disorders and has potential for the monitoring of therapy response in metabolic bone disease.

Adult↗

PubMed1996

Visualisation of loss of 5-HT2A receptors with age in healthy volunteers using [18F]altanserin and positron emission tomographic imaging.

We used [18F]altanserin and positron emission tomography (PET) to image serotonin 5-HT2A receptors in humans. The highest [18F]altanserin uptake is found in the cerebral cortex, with specific-to-nonspecific binding ratios varying from 0.53 to 1.91 in humans between 24 and 48 years of age. In all neocortical regions studied, [18F]altanserin uptake correlates negatively with age. No correlations were found between age and uptake in the cerebellum, the regional cerebral blood flow, or the time course of metabolization of [18F]altanserin. The reduction in cerebral 5-HT2A receptor binding thus directly reflects the loss of specific 5-HT2A receptors with age.

Adult↗

PubMed1996

Task dependency of visual processing in the human visual system.

In this review we contrast passive, attribute driven processing in the visual system with an active, task-dependent view and summarize the evidence from our Positron Emission Tomography (PET) work supporting the task-dependent view. The PET studies involved comparison of regional Cerebral Blood Flow (rCBF) in closely related detection and discrimination tasks. The major finding reported is that the same retinal input or input containing only a single cue activates different extrastriate areas depending on the task.

Adult↗

PubMed1996

Synthesis of carbon-11- and fluorine-18-labeled 1-methyl-4-piperidyl-4'-fluorobenzoate and their biodistribution in mice.

Carbon-11- and fluorine-18-labeled forms of 1-methyl-4-piperidyl-4'-fluorobenzoate were prepared as potential in vivo substrates for brain acetylcholinesterase. The 1-methyl-4-piperidyl-4'-[18F]fluorobenzoate was prepared by aromatic nucleophilic substitution using the nitro precursor and no-carrier added [18F]fluoride ion. The 1-[11C]methyl-4-piperidyl-4'-fluorobenzoate was synthesized by N-[11C]methylation of the appropriate nor-methyl precursor. Biodistribution studies in mice showed high brain uptake of these radiotracers followed by a fast washout with no significant retention of radioactivity in areas of high acetylcholinesterase enzymatic activity. This is contrasted with 1-[11C]methyl-4-piperidylacetate, which is rapidly trapped in brain tissues through hydrolysis by AChE. Further in vivo and in vitro studies demonstrated that 1-methyl-4-piperidyl-4'-fluorobenzoate was not a substrate for AChE, and thus not suitable as an in vivo radiotracer for studying this enzyme in the brain.

Acetates↗

PubMed1996

The influence of stimulus location on the brain activation pattern in detection and orientation discrimination. A PET study of visual attention.

This PET study concerns changes in regional cerebral blood flow (rCBF) associated with orientation discrimination tasks and with simple detection of the stimulus. The difference in rCBF between discrimination and detection represents the discrimination, or 'task', component of the response. We have examined how such differences are influenced by the position of the visual stimulus and also how they change when a peripheral distractor is added to a relevant central stimulus. We first determined the regions in which the task produced the main effect regardless of stimulus position or distraction with an additional stimulus. In these selected regions, we determined the interactions between task and stimulus position and the interactions between task and stimulus addition. Five regions were more active during orientation discrimination than during stimulus detection: the inferior occipital cortex, the right putamen, the superior parietal lobule, the anterior cingulate cortex and the left lower and the right upper premotor area. Stimulus addition interacted with task only in the lower premotor area. Interactions between the task and stimulus position occurred in the occipital and parietal cortex and in the putamen. When a central stimulus was presented instead of a peripheral one the difference between orientation discrimination and stimulus detection was significantly larger in the inferior occipital lobe and in the right putamen. Conversely, the difference between orientation discrimination and stimulus detection in the superior parietal lobule was significantly larger when a peripheral stimulus was presented instead of a central one.

Adult↗

PubMed1996

Three-dimensional correction for spillover and recovery of myocardial PET images.

UNLABELLED: PET permits the quantification of myocardial blood flow, but is hampered by the limited spatial resolution of PET images. METHODS: We evaluated two methods for the correction of resolution effects in PET perfusion 13NH3-ammonia images. In one model, the spillover and recovery coefficients are estimated in the kinetic modeling analysis. The new, second model uses an explicit delineation of the left ventricular wall and a convolution model for the system point spread function to compute the regional values of the spillover and recovery coefficients. RESULTS: The new method is validated with phantom measurements. The two methods are evaluated on animal experiments using 13NH3-ammonia. Both two- and three- compartment models were used to compute absolute flow values. Excellent linear correlations with microsphere data were obtained. The slope of the regression line was lower for corrections based on kinetic modeling as compared to convolution-based correction. In animal experiments, recovery coefficients of 59% for the myocardial wall and 86% for the blood pool were obtained. Spillover from the blood pool into the myocardial was was 14%. CONCLUSION: The new correction method strongly suppresses spillover and recovery effects due to limited resolution.

Algorithms↗

PubMed1995

Impaired myocardial tissue perfusion early after successful thrombolysis. Impact on myocardial flow, metabolism, and function at late follow-up.

BACKGROUND: Impaired tissue reperfusion after successful recanalization of an epicardial coronary artery has been documented both in animals and in patients with acute myocardial infarction. Whether this phenomenon can be demonstrated with positron emission tomography (PET) and whether it has an effect on late recovery of flow, metabolism, and function are unknown. METHODS AND RESULTS: Thirty patients with an acute myocardial infarction and TIMI flow grade 3 of the infarcted vessel at 90 minutes after thrombolytic therapy were studied. Within 24 hours after thrombolysis, at 5 days and at 3 months, myocardial blood flow was measured with 13NH3. 18FDG uptake was measured at 5 days. Radionuclide left ventricular angiograms were acquired at 5 days and at 3 months. In 11 patients (37%), regional myocardial flow was severely impaired (< 50% of normally perfused myocardium) despite successful thrombolysis. No recovery of left ventricular function occurred in any of these patients at 3 months. In 12 patients (40%), intermediate flows (50% to 75% of normal) were found, with functional improvement after angioplasty only in regions with a PET mismatch. Seven patients (23%) had high flow values early after successful thrombolysis (> 75% of normal) and showed preserved regional contractile function at 3 months. CONCLUSIONS: This study is the first demonstration with PET of impaired myocardial tissue perfusion in patients with an acute myocardial infarction after successful thrombolysis. Functional recovery of the reperfused myocardium is observed only when adequate tissue flow is restored. PET may be helpful in selecting patients in whom additional revascularization can improve recovery of left ventricular function.

Aged↗

PubMed1995

Blood flow in human anterior temporal cortex decreases with stimulus familiarity.

In this positron emission tomography investigation of human nonverbal visual memory, we determined the anatomical distribution of changes in regional cerebral blood flow (rCBF) reflecting familiarity of visual shapes. All stimuli consisted of relatively simple, abstract outlines generated by Fourier expansions. Subjects performed the same task twice, once using unfamiliar and once using familiar stimuli. The task was a modified version of delayed nonmatching-to-sample, consisting of one sample presentation prior to tracer injection and a sequence of test trials during which images were acquired. When this task was performed with familiar instead of unfamiliar stimuli, only decreases in rCBF were observed, which were localized to the left lateral anterior temporal neocortex, the left medial temporal pole, and the rostral anterior cingulate. The correlates of familiarity measured in this human brain mapping experiment may correspond with what has been measured in single neurons in monkeys. This correspondence holds both for the type and for the localization of changes.

Adolescent↗

PubMed1995

Regional myocardial blood flow, glucose utilization and contractile function before and after revascularization and ultrastructural findings in patients with chronic coronary artery disease.

In patients with chronic coronary artery disease, follow-up measurements of myocardial blood flow, metabolism and function were correlated with histology. In 41 patients with chronic coronary artery disease and a severely stenosed left anterior descending coronary artery, a positron emission tomographic (PET) flow/metabolism study and nuclear angiography were performed immediately before and 3 months after bypass surgery. Biopsies were taken from the left ventricular anterior wall at the time of surgery. Control biopsies were taken from donor hearts for cardiac transplantation and from hearts of patients with a defect of the atrial septum. A significant improvement of flow (P<0.01) and regional contractile function (P<0.01) was observed in the mismatch group. Glucose utilization was significantly lower (P<0.001) as compared to preoperative values. The group with preserved flow and the PET match group revealed no significant changes in flow, metabolism or function. Control biopsies revealed significantly less myolytic cells as compared to biopsies taken from both match and mismatch groups (P<0.01) and less fibrosis as compared to biopsies taken from the match group (P<0.01). Postoperatively, linear relationships were found between flow and both % fibrosis (r = 0.71, P<0.001) and regional anterior ejection fraction (r = 0.7, P<0.001). Only mismatch areas revealed significant recovery of both flow and function after revascularization with a disappearance of enhanced glucose uptake. The better linear correlation between flow and % fibrosis after surgery as compared to preoperatively was probably due to improvement of flow values in the mismatch group.

Coronary Artery Bypass↗