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Biomedical subjects

S Asenbaum

Publications and source records attributed to S Asenbaum.

At least 37 records · Page 2Linked to original sources
PubMed2001

A medial to lateral shift in pre-movement cortical activity in hemi-Parkinson's disease.

OBJECTIVE: Recent evidence suggests that cortical activity associated with voluntary movement is relatively shifted from medial to lateral premotor areas in Parkinson's disease. This shift occurs bilaterally even for unilateral responses. It is not clear whether the shift in processing reflects an overall change in movement strategy, thereby involving alternate cortical areas, or reflects a compensatory change whereby, given the appropriate conditions, less impaired cortical areas are able to provide a similar function in compensation for those areas which are more impaired. This issue was examined in patients with hemi-Parkinson's disease, in whom basal ganglia impairment is most pronounced in one hemisphere. METHODS: Fourteen patients with hemi-Parkinson's disease and 15 age-matched control subjects performed a Go/NoGo finger movement task and the contingent negative variation (CNV) was recorded from 21 scalp positions. RESULTS AND CONCLUSIONS: Maximal CNV amplitudes were found over central medial regions for control subjects, but were shifted more frontally for Parkinson's disease patients, reduced in amplitude over the midline and lateralized towards the side ipsilateral to the greatest basal ganglia impairment. This shift in cortical activity from medial to lateral areas in Parkinson's disease patients appears to reflect a compensatory mechanism operating predominantly on the side of greatest basal ganglia impairment.

Action Potentials↗
PubMed2001

Dopamine transporter availability in symptomatic depressed patients with seasonal affective disorder and healthy controls.

BACKGROUND: During recent years hypotheses about the pathophysiology of seasonal affective disorder/winter type (SAD) have focused monoaminergic mechanisms. There is substantial evidence that serotonergic systems play an important role. The potential role of catecholaminergic pathways has not been fully explored. METHODS: Eleven drug-free, symptomatic depressed patients with SAD and 11 healthy age- and gender-matched healthy controls were invited to participate in a 123Ibeta-CIT single photon emission computed tomography (SPECT) study to assess striatal density of dopamine transporters (DATs). The cerebellum was used as reference region. Ratios were calculated between mean counts in left and right striatum and cerebellum. These ratios minus I represent specific/non-displaceable binding and are assumed to be directly related to DAT availability at the time of binding equilibrium. RESULTS: Displaceable 153Ibeta-CIT binding in the area corresponding to the left striatum was significantly reduced in SAD patients compared to healthy controls (10.49+/-0.91 v. 1195+/-1.54, respectively; 2-tailed P = 0.017, Mann-Whitney U test). CONCLUSIONS: These data suggest reductions in the availability of striatal DAT binding sites in untreated symptomatic depressed SAD patients. It remains unclear whether these reductions represent a primary defect or an attempt to overcome a state of possible lowered dopamine availability in the synaptic cleft during a depressive episode of SAD. However, these findings provide evidence that brain dopaminergic systems may be involved in the pathophysiology of SAD.

Adult↗
PubMed2001

Nuclear medicine in the preoperative evaluation of epilepsy.

The clinical usefulness of nuclear medicine in the preoperative evaluation of epilepsy is highlighted with regard to non-lesional temporal lobe epilepsy, extratemporal epilepsy, bitemporal interictal epileptiform discharges (IEDs) and in dual pathology and cortical dysgenesis. Ictal single photon emission computed tomography (SPECT) shows good sensitivities in the correct lateralization of an electroencephalogram-defined epileptic focus in lesional and, to a lesser extent, non-lesional epilepsy. Positron emission tomography (PET) using 18F-fluorodeoxyglucose or 11C-flumazenil gives a good detection rate of the seizure onset zone in non-lesional cases and extratemporal epilepsy. The investigation of patients with bitemporal IEDs can confirm the existence of bitemporal seizure onset. For patients with a dual pathology or cortical dysgenesis nuclear medicine offers the opportunity to delineate the existence or extension of abnormalities possibly responsible for the seizure disorder.

Epilepsy↗
PubMed2000

[123I]-beta-CIT SPECT imaging shows reduced brain serotonin transporter availability in drug-free depressed patients with seasonal affective disorder.

BACKGROUND: Numerous findings indicate alterations in brain serotonin systems in seasonal affective disorder (SAD). [(123)I]-2-beta-carbomethoxy-3-beta-(4-iodophenyl)-tropane ([(123)I]-beta-CIT) labels serotonin transporters (5-HTTs) in the midbrain. We performed a [(123)I]-beta-CIT single photon emission computer tomography (SPECT) study under the hypothesis of lower [(123)I]-beta-CIT binding reflecting reduced central 5-HTT availability in depressed SAD patients. METHODS: Depressed SAD patients and healthy control subjects were investigated using [(123)I]-beta-CIT SPECT 4 hours and again 24 hours after tracer injection. Subjects had either never used psychotropic medication or had been drug-free for at least 6 months prior to the investigation. Specific-to-nondisplaceable partition coefficient (V(3)") was calculated for the thalamus-hypothalamus and the midbrain-pons; the cerebellum served as a reference region. RESULTS: Patients showed a reduction in V(3)" in thalamus-hypothalamus (2.41+/-0.3 vs. 2.84+/-0.4; p = .026) 24 hours post tracer injection (p.i.). No difference between patients and control subjects was found in midbrain-pons (1.31+/-0.2 vs. 1.42+/-0.2; p = .39). No differences were detected in the SPECT acquisitions 4 hours p.i. CONCLUSIONS: Depressed SAD patients showed lower specific-to-nondisplaceable [(123)I]-beta-CIT binding in the region of interest (ROI) thalamus-hypothalamus. The small size of the midbrain-pons ROI may have contributed to the failure to show a difference in this ROI as well. Similar to reduced midbrain 5-HTT availability in nonseasonal depression, depression in SAD seems to be associated with reduced 5-HTT availability to the thalamus-hypothalamus.

Adult↗
PubMed2000

Seasonal variation of availability of serotonin transporter binding sites in healthy female subjects as measured by [123I]-2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane and single photon emission computed tomography.

BACKGROUND: Previous studies have indicated annual variations in central and peripheral serotonergic activity. In the present study we studied five women in summer and six women in winter and evaluated possible differences in availability of brain serotonin transporters between summer and winter. METHODS: We employed the single photon emission computed tomography ligand [123I]-2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane ([123I] beta-CIT) to visualize binding to the serotonin transporter site in the human thalamus/hypothalamus midbrain area in vivo. Brain imaging studies were performed in one group between May and August and in the other between November and December. RESULTS: We found significant differences in displaceable [123I] beta-CIT binding in the region corresponding to thalamus/hypothalamus between the summer group and the winter group (1.9 +/- 0.3 vs. 1.4 +/- 0.2, respectively; p < .01). CONCLUSIONS: The results of the present study suggest reduced brain serotonin transporter availability in winter. This finding further substantiates evidence of seasonal variations in brain serotonergic function.

Adult↗
PubMed2000

[123I]beta-CIT SPECT in multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration.

Differentiation between Parkinson's disease (PD) and other neurodegenerative disorders with parkinsonian features, such as multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD), is difficult on clinical grounds. We studied the pattern of dopaminergic degeneration in 18 patients with probable MSA, 8 patients with PSP, 4 patients with CBD, 48 patients with PD and a similar degree of disability, and 14 control subjects performing single photon emission computed tomography (SPECT) 20 hours after injection of [123I]beta-CIT. Overall striatal binding was significantly reduced in MSA (-51% of normal mean), PSP (-60%), CBD (-35%), and PD (-58%), without overlap with control values. Asymmetry of striatal beta-CIT binding was significantly increased in patients with CBD and PD, as compared with control subjects. Although asymmetry seemed to be less pronounced in MSA and PSP than in PD, this was not statistically significant. Putamen-caudate nucleus ratios in patients with PD, MSA, and PSP, but not with CBD, were significantly reduced, as compared with control subjects. In conclusion, [123I]beta-CIT SPECT reliably enables the visualization of the presynaptic dopaminergic lesion in patients with MSA, PSP, and CBD. In most patients, however, it does not seem to be possible to differentiate these disorders from PD with this method.

Adult↗
PubMed2000

SPECT and PET imaging of the dopaminergic system in Parkinson's disease.

This paper gives an overview of the clinical importance of SPECT and PET imaging of the dopaminergic system in the differential diagnosis and for the determination of the progression rate of Parkinson's disease (PD). D2 receptor imaging can help to differentiate multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) from PD. In patients treated with neuroleptics it is possible to determine the rate of striatal D2 receptor blockade using this technique. This occupancy rate parallels the occurrence of parkinsonian side effects. Its measurement helps in the selection of newer atypical neuroleptics, which can be used to treat drug-induced psychosis in PD because they do not aggravate parkinsonian symptoms. Imaging of dopaminergic neurons with [123I]beta-CIT SPECT or [18F]DOPA PET is a way to visualize and quantify the nigrostriatal dopaminergic lesion in PD. Findings correlate with clinical rating scales and demonstrate the feasibility of detecting the preclinical lesion in patients with hemiparkinson or familial PD. [123I]beta-CIT SPECT can easily distinguish patients with essential tremor and patients with "lower body parkinsonism" due to a subcortical vascular encephalopathy. MSA and PSP cannot be separated from PD with this method alone. Longitudinal studies with [123I]beta-CIT SPECT and [18F]DOPA PET can quantify the progression rate in PD. SPECT results from our own group show a low rate of progression in patients with a long duration of disease and a more marked progression rate in patients with shorter disease duration. In the former group regions in the striatum with higher beta-CIT binding at the time of the first SPECT scan decline faster than regions with lower binding. These findings suggest a curvilinear course of progression which starts at different time points in different striatal regions and which levels off after several years of disease duration. These findings are in line with data from PET studies and underline the importance of an early start of neuroprotective strategies. Preliminary data from PET and SPECT studies in early PD suggest that dopamine agonists might have a slight neuroprotective effect and might slow down the rate of progression of the disease.

Dopamine↗
PubMed2000

Excessive daytime sleepiness in patients suffering from different levels of obstructive sleep apnoea syndrome.

Excessive daytime sleepiness (EDS) is a frequent symptom of patients with obstructive sleep apnoea (OSA). EDS is a high-risk factor for accidents at work and on the road. Thirty untreated patients with different levels of severity of OSA were studied concerning night sleep and EDS. The criterion for severity was the respiratory disturbance index (RDI): 15 patients were classified as 'moderately' apnoeic (RDI < 40), 15 as 'severely' apnoeic (RDI > 40). Following night-time polysomnography, objective and subjective aspects of EDS were studied. To assess objective EDS the Maintenance of Wakefulness Test (MWT) and a computer-based vigilance performance test were used. Subjective EDS was determined using the Stanford Sleepiness Scale (SSS), the Epworth Sleepiness Scale (ESS) and the Visual Analogue Scales for Performance (VAS-P) and Tiredness (VAS-T). Well-being was assessed using the Scale of Well-Being by von Zerssen (Bf-S/Bf-S'). Severe apnoea patients spent more time in stage 1 and less in slow-wave sleep. MWT latencies tended to be shorter in the severe apnoea group. Vigilance testing revealed no group differences. Patients with moderate apnoea described themselves as more impaired in all subjective scales, but only SSS scores reached statistical significance. Our results suggest that there is no simple correlation between polysomnographic and respiratory sleep variables at night on the one hand, and the extent of EDS on the other hand. Furthermore, subjective and objective evaluation of EDS does not yield the same results. New approaches which allow a more detailed analysis of night sleep and daytime function are required to identify high-risked patients.

Circadian Rhythm↗
PubMed2000

Imaging serotonin and dopamine transporters with 123I-beta-CIT SPECT: binding kinetics and effects of normal aging.

UNLABELLED: [123I]beta-carbomethoxy-3-beta-(4-iodophenyl)-tropane (CIT) is a useful ligand for dopamine transporters (DATs) and serotonin transporters (5-HTTs). Previous SPECT studies have shown a state of sustained equilibrium in the striatum on day 2 after injection that allows quantification of striatal DATs using a simple ratio of specific-to-nondisplaceable binding. The aim of this study was to investigate the kinetics of [123I]beta-CIT uptake in the thalamus, hypothalamus, and midbrain, areas known to contain 5-HTTs in high densities. METHODS: SPECT with a triple-head camera was performed on 16 healthy volunteers (13 women, 3 men; mean age [+/-SD], 32 +/- 11 y) after intravenous bolus injection of 130 +/- 20 MBq (3.5 +/- 0.5 mCi) [123I]beta-CIT. Two individuals were scanned 1, 2, 4, 7, 10, 13, 16, and 24 h after injection, and the remaining 14 were scanned 4, 7, 10, 20, and 24 h after injection. Values from 19 previously examined healthy volunteers (8 women, 11 men; mean age, 52 +/- 20 y) were included in the analysis to study the age dependency of beta-CIT binding in striatal and 5-HTT-rich brain areas in a larger control sample. RESULTS: Peak uptake 4 h after injection, followed by stable uptake until 10 h and a slow decrease until 24 h, was observed in the thalamus-hypothalamus region. Activity in the midbrain-pons region peaked 2 h after injection. Because of a concomitant slow but steady decline of uptake in reference regions starting 4 h after injection, a higher stability of binding ratios for 5-HTT-rich brain areas was observed on day 2, suggesting that a state of transient equilibrium is reached between 20 and 24 h but that conditions are only close to transient equilibrium between 4 and 10 h after injection for 5-HTT-rich brain areas. In addition to an age-related decline of striatal [123I]beta-CIT binding of 6.6% per decade, a significant age-associated decrease of beta-CIT binding of 3-4% per decade was found in 5-HTT-rich brain areas. The decline of beta-CIT binding in these regions may be explained, at least in part, by a loss of monoamine transporters with age but may also be related to age-associated morphologic changes. CONCLUSION: [123I]beta-CIT appears to be a suitable ligand for imaging serotonin transporters with SPECT. However, careful age matching is warranted for [123I]beta-CIT SPECT studies of 5-HTT changes in patients with neuropsychiatric disorders.

Adult↗
PubMed1999

Application of correlation dimension and pointwise dimension for non-linear topographical analysis of focal onset seizures.

For many patients who are candidates for epilepsy surgery, non-invasive evaluation fails to provide sufficient information to permit surgical treatment. Since there are also definite risks and considerable costs associated with invasive procedures, new (non-invasive) techniques are required. This study provides empirical evidence that a non-linear approach applied to ictal surface electroencephalograms (EEGs) can help to delineate the area of seizure onset and may prove useful in complementing visual analysis of the EEG. Multichannel EEGs, recorded from eight patients with different drug-resistant localisation-related epilepsies, were analysed using the concept of correlation dimension and two extensions based on the pointwise dimension. The latter also provided results in cases where assessment of the correlation dimension was not feasible. Comparative values between 2 and 6 were accepted as the result of the algorithms, mostly 3-4 for the EEG channels strongly reflecting epileptic activity, and 4-6 for the other signals. The proportion of accepted pointwise values was usually 200-800% for strong epileptic EEG activity compared to the other data. The approach permitted the characterisation of the scalp area reflecting epileptic activity. The results obtained were in perfect concordance with those obtained during pre-surgical work-up and confirmed by the post-operative outcome.

Adolescent↗
PubMed1999

In vivo 123I IBZM SPECT imaging of striatal dopamine-2 receptor occupancy in schizophrenic patients treated with olanzapine in comparison to clozapine and haloperidol.

We investigated the degree of striatal dopamine-2 (D2) receptor occupancy in six schizophrenic patients receiving clinically effective antipsychotic treatment with olanzapine 10-25 mg/day in comparison to patients treated with clozapine 300-600 mg/day (n = 6) or haloperidol 5-20 mg/day (n = 10). 123I Iodobenzamide (IBZM) and single photon emission computerized tomography (SPECT) were used for the visualization of striatal D2 receptors. For the quantification of striatal D2 receptor occupancy, striatal IBZM binding in patients treated with antipsychotics was compared to that in untreated healthy controls (n = 8) reported earlier. Olanzapine led to a mean striatal D2 receptor occupancy rate of 75% (range 63-85). Haloperidol-treated patients showed dose-dependently (Pearson r = 0.64; P < 0.05) a significantly higher (P < 0.05) mean occupancy rate of 84% (range 67-94). During clozapine treatment, the mean D2 receptor occupancy of 33% (range < 20-49) was significantly lower than with olanzapine (P < 0.005). The higher striatal D2 receptor occupancy of haloperidol was correlated with the incidence and severity of extrapyramidal motor side-effects (EPS). No clinical relevant EPS occurred during treatment with olanzapine or clozapine. There was no correlation between the degree of striatal D2 receptor occupancy and clinical improvement.

Adult↗
PubMed1999

In vivo visualization of serotonin transporters in the human brain during fluoxetine treatment.

Beta-CIT can be used as a tracer for SPECT to visualize serotonin transporters in the human brain. We present a case of bulimia nervosa and major depressive disorder, who had been treated with up to 60 mg/d fluoxetine for several weeks. Four hours after injection of the tracer more than 40% of serotonin transporters were blocked. To our knowledge, this is the first direct documentation of the pharmacodynamic action of fluoxetine in the human brain in vivo.

Adolescent↗
PubMed1999

Regional cerebral blood flow during temporal lobe seizures associated with ictal vomiting: an ictal SPECT study in two patients.

PURPOSE: Ictal vomiting represents a rare clinical manifestation during seizures originating from the temporal lobes of the nondominant hemisphere. The precise anatomic structures responsible for generation of ictal vomiting remain to be clarified. Ictal single photon emission computed tomography (SPECT), which allows one to visualize the three-dimensional dynamic changes of regional cerebral blood flow (rCBF) associated with the ongoing epileptic activity, should be useful to study the brain areas activated during ictal vomiting. METHODS: We performed ictal Tc-HMPAO SPECT scans in two patients with mesial temporal lobe epilepsy (MTLE) whose seizures were characterized by ictal retching and vomiting. MTLE was documented by typical clinical seizure semiology, interictal and ictal EEG findings, hippocampal atrophy on magnetic resonance imaging (MRI) scan, and a seizure-free outcome after selective amydalohippocampectomy. In both patients, seizures originated in the nondominant temporal lobe. We obtained accurate anatomic reference of rCBF changes visible on SPECT by a special coregistration technique of MRI and SPECT. We used ictal SPECT studies in 10 patients with MTLE who had seizures without ictal vomiting as controls. RESULTS: In the two patients with ictal vomiting, we found a significant hyperperfusion of the nondominant temporal lobe (inferior, medial, and lateral superior) and of the occipital region on ictal SPECT. In patients without ictal vomiting, on the contrary, these brain regions never were hyperperfused simultaneously. CONCLUSIONS: Ictal SPECT provides further evidence that activation of a complex cortical network, including the medial and lateral superior aspects of the temporal lobe, and maybe the occipital lobes, is responsible for the generation of ictal vomiting.

Adult↗
PubMed1998

Sertindole and dopamine D2 receptor occupancy in comparison to risperidone, clozapine and haloperidol - a 123I-IBZM SPECT study.

The striatal D2 dopamine binding was studied in schizophrenic patients treated with the novel atypical antipsychotic drug sertindole (n=10). Comparisons were obtained with haloperidol (n=8), clozapine (n=6), risperidone (n=11) and untreated healthy controls (n=8) of a dataset which has partly been reported previously. 123I-Iodobenzamide (IBZM) single photon emission computerized tomography (SPECT) was used for estimation of striatal dopamine D2 receptor binding. Sertindole-treated patients exhibited significantly (P < 0.001) lower levels of striatal D2 binding (BG/FC ratio:1.28) compared with those treated with haloperidol (BG/FC ratio:1.09) and risperidone (8 mg:1.18) but significantly (P < 0.005) higher levels compared with clozapine (BG/FC ratio: 1.49). However, if patients were pretreated with a depot neuroleptic, significantly (P < 0.05) higher striatal D2 binding (BG/FC ratio:1.12) has been obtained. Since sertindole has been shown to exert distinct clinical efficacy for treatment of positive and negative symptoms, our data are indicative that antipsychotic efficacy is not associated with a high degree of striatal D2 receptor occupancy in schizophrenic patients.

Adult↗
PubMed1998

[123I]beta-CIT and SPECT in essential tremor and Parkinson's disease.

UNLABELLED: Resting and postural tremor may occur in essential tremor (ET) and Parkinson's disease (PD). The aim of the present study was to investigate the cocaine derivative [123I]beta-CIT, which labels striatal dopamine transporters, and SPECT in differentiating these diseases. METHODS: 30 healthy volunteers, 32 patients with ET and 29 patients with idiopathic PD of Hoehn/Yahr stage I were investigated. Specific over nondisplaceable binding ratios (target/cerebellum-1) were calculated for the striatum, the caudate nucleus and the putamen separately as well as a ratio putamen/caudate and the percent deviation of each patient's ratio from age-expected control values. RESULTS: Striatal [123I]beta-CIT binding ratios in ET were within normal ranges and showed only a discrete elevation to age-expected control values (+14.6%). In PD significantly reduced specific binding was evident not only contralaterally to the clinically affected side (putamen: -62%, caudate nucleus: -35%), but also ipsilaterally (putamen: -45%, caudate nucleus: -22%). All investigated parameters differed significantly between PD and controls and ET respectively. CONCLUSION: Imaging striatal dopamine transporters with [123I]beta-CIT and SPECT could clearly distinguish between ET and PD in an early stage of the disease. Findings do not suggest a subclinical involvement of dopaminergic nigrostriatal neurons in ET.

Adult↗
PubMed1998

Monitoring of median nerve somatosensory evoked potentials in carotid surgery.

The purpose of this study was to compare median somatosensory evoked potentials (SEP) in patients undergoing carotid endarterectomy (CEA) with routine shunting and nonshunting (excluding the option of selective shunting) and to evaluate the significance of a decrease in the amplitude of the cortically generated waveforms of the SEP and/or an increase in the central conduction time (CCT) on the one hand, and that of a loss of the cortical SEP, on the other. Somatosensory evoked potentials were recorded in 32 patients before, during, and after CEA with routine shunting or nonshunting. The N13 and N20 latency, the CCT, and the N20/P25 amplitude were evaluated. In addition, a meta-analysis of 15 previous studies was performed comprising a total of 3,136 patients. The intraoperative cortical SEP showed no differences between shunted and nonshunted patients, apart from the preclamping value of the N20/P25 amplitude which was lower in the nonshunted subjects. The number of patients with decreased and/or delayed cortical SEP (findings frequently used as criterion for selective shunting) was similar in the two study groups. A loss of the cortical SEP occurred in one patient operated on without an indwelling shunt. None of these patients had a new neurologic deficit after surgery. In the meta-analysis, the positive predictive value of decreased and/or delayed cortical SEP was extremely poor, that of absent cortical SEP was poor to moderate and the prevalence of new neurologic deficits was similar in patients undergoing CEA with routine shunting-nonshunting and those with selective shunting-nonshunting. Our study suggests that decreased and/or delayed cortical SEP are unreliable predictors of the neurological outcome of CEA patients and consequently an unsuitable criterion for selective shunting. The meta-analysis confirms this finding and shows that the neurologic outcome is not improved by using an indwelling shunt selectively based on SEP monitoring.

Aged↗
PubMed1998

Imaging of cerebral blood flow with technetium-99m-HMPAO and technetium-99m-ECD: a comparison.

UNLABELLED: Because 99mTc-HMPAO and 99mTc-ECD are both used for SPECT imaging of cerebral blood flow, the question arises whether there are any differences in their respective regional cerebral distribution. For that purpose, visual and semiquantitative comparisons between 99mTc-HMPAO and 99mTc-ECD studies were performed. METHODS: Seventeen patients (4 women; 13 men; age 45-89 yr; mean age 71 yr) with various neurological diseases, except acute/subacute stroke, were investigated twice with 99mTc-HMPAO and 99mTc-ECD using a triple-headed rotating SPECT camera. After image reorientation, the two studies were evaluated visually. Seventy regions of interest (ROIs) were drawn manually and the same set of ROIs was applied in both studies. Regional indices (RI) normalized to individual brain values were calculated and first compared between two random patient groups. Second, for all patients, RI for 70 and later for 27 regions (gained after summing values of corresponding regions in different brain slices) were compared by using a paired Student's t-test applying Bonferroni's correction. RESULTS: Visual evaluation demonstrated relatively high 99mTc-ECD uptake in occipital and comparatively low uptake in mediotemporal regions. Calculation of RI revealed significantly higher values in the right cerebellum, brainstem, mediotemporal regions, right basal ganglia and the thalamus in the 99mTc-HMPAO SPECT studies and higher values in the occipital, supratemporal/inferior parietal and parietal cortex in the 99mTc-ECD SPECT studies, respectively. CONCLUSION: Significant differences in regional tracer distribution between 99mTc-HMPAO and 99mTc-ECD could be detected, probably caused by different tracer kinetics. The results indicate that direct comparisons of studies performed with 99mTc-HMPAO and 99mTc-ECD are not possible and the use of either tracer can be favorable in different clinical questions.

Aged↗