rCBF Single Photon Emission Computed Tomography Research Articles

Regional cerebral blood flow single photon emission computed tomography for detection of Frontotemporal dementia in people with suspected dementia.

Regional cerebral blood flow single photon emission computed tomography for detection of Frontotemporal dementia in people with suspected dementia.

From primary progressive aphasia to corticobasal syndrome: two clinical and rCBF functional reports

We describe two cases, both presenting with a 2-year history of isolated language disorders, one compatible with logopenic variant and the other with non-fluent variant of primary progressive aphasia (PPA). Afterwards, each developed a corticobasal syndrome (CBS) with alien limb phenomenon and a multi-domain cognitive impairment. Regional cerebral perfusion (rCBF) study using 99mTc-ECD single photon emission computed tomography (SPECT) revealed hypoperfusion patterns consistent with these aphasia types and with the presence of limb apraxia. We report two cases of PPA variants associated with CBS and we suggest that SPECT rCBF correlates can be useful in making a differential diagnosis within the PPA spectrum.

Comparison of Perfusion Weighted Magnetic Resonance Imaging and Single Photon Emission Computed Tomography for Assessment of Cerebrovascular Reserve in Symptomatic Carotid Territory Stenosis

Background: Perfusion Weighted Magnetic Resonance Imaging (PW-MRI) and HMPAO Single Photon Emission Computed Tomography (SPECT) are both cerebral perfusion measurement techniques. Imaging before and after acetazolamide administration can assess cerebrovascular reserve in symptomatic haemodynamic cerebrovascular disease. We compared SPECT and PW-MRI parameters in this patient group. Methods: We identified 10 patients with haemody-namically induced symptoms and intra- or extra-cranial arterial stenoses with back-to-back acetazolamide challenge SPECT and PW-MRI, 4 of whom had resting studies. Regions of interest (ROIs) were applied to parameter maps using an ASPECTS template and perfusion parameters expressed relative to contralateral ROIs, giving 118 challenge and 48 resting ROIs. Results: SPECT relative cerebral blood flow (rCBF) correlated with PW-MRI time to peak (TTP) (r = ?0.568), mean transit time (MTT) (r = ?0.317), regional cerebral blood flow (rCBF) (r = 0.299) and cerebral blood volume (CBV) (r = 0.224). Bias between SPECT and PW-MRI rCBF was small (?0.018) with wide limits of agreement and a systematic measurement error. Pre- to post-acetazolamide PW-MRI rCBF change showed poor sensitivity and specificity for detecting change in SPECT rCBF. SPECT and PW-MRI rCBF had stronger correlation and smaller bias in unilateral stenosis than with bilateral stenosis. Conclusion: Systematic bias between techniques limits interchange- ability in cerebrovascular reserve measurement in patients with cerebrovascular stenosis.

Neuropsychological functions and rCBF SPECT in Parkinson’s disease patients considered candidates for deep brain stimulation

In the present study, we examined relationships between neuropsychological functions and brain single photon emission computed tomography (SPECT) regional cerebral blood flow (rCBF) observed at presurgical evaluation for deep brain stimulation (DBS) of the subthalamic nucleus (STN) in advanced Parkinson's disease (PD) patients. Twenty advanced non-demented PD patients, candidates for DBS surgery, underwent perfusion brain SPECT study and neuropsychological assessment prior to surgery (range: 30-50 days). Patients were further assessed using the Unified Parkinson's Disease Rating Scale (UPDRS) and Hoehn and Yahr (H&Y) scale. During all assessments patients were "on" standard medication. NeuroGam software, which permits voxel by voxel analysis, was used to compare the brain perfusion of PD patients with a normal database adjusted for sex and age. Neuropsychological scores were compared to age, education and sex-adjusted normative databases. Our results indicated that the distribution of rCBF showed significant differences when compared to an age- and sex-adjusted normative database. We found impaired blood flow in 17 (85%) of our patients in the left prefrontal lobe, in 14 (70%) in the right prefrontal lobe and in 11 (55%) in the left frontal and right parietal lobes. Neuropsychological testing revealed that 18 (90%) of our patients had significant impairments in measures of executive functions (set-shifting) and 15 (75%) in response inhibition. Furthermore, we found significant correlations between measures of visual attention, executive functions and the right frontal lobe region. The presence of widespread blood flow reduction was observed mainly in the frontal lobes of dementia-free patients with advanced PD. Furthermore, performance on specific cognitive measures was highly related to perfusion brain SPECT findings.

Preliminary clinical study in patients with hemispatial neglect after stroke by neglect test battery and 99mTc-ECD single-photon emission computed tomography

To explore the presence, clinical characteristics, anatomical foci in image and mechanism of hemispatial neglect (HSN), neglect test battery and single-photon emission computed tomography (SPECT) regional cerebral blood flow (rCBF) imaging were performed on patients with stroke. Thirty dextromanual patients who were diagnosed as having unilateral stroke clinically were recruited. A neglect test battery including line bisection test, star cancellation test and drawing test was performed on the subjects. The severity of neglect was measured on neglect tests. The lowest rCBF, the range with decreased rCBF, number of the foci with decreased rCBF, the flow deficit size and the total number of pixels in the foci were measured on SPECT rCBF imaging. Twenty-five patients were diagnosed as having HSN by the neglect test battery. Contralateral neglect (CN) and ipsilateral neglect (IN) were observed in both right and left hemisphere strokes. On SPECT imaging, the patients with neglect had decreased rCBF in the frontal cortex most often; followed by the parietal, occipital and temporal cortices; and basal ganglia and thalamus in some cases. The patients who had two or more regions damaged showed neglect more often and severity. The correlation coefficients between rCBF in the foci, the decreased percentage of rCBF of the foci and the severity of neglect were -0.119 (P>.05) and 0.221 (P>.05). The correlation coefficients between the range, number of foci, the flow deficit size, the total number of pixels of the foci and the severity of neglect were 0.537 (P<.05), 0.493 (P<.05), 0.561 (P<.05), 0.466 (P<.05), respectively. No difference between CN and IN on SPECT images reached statistical significance. The severity of neglect did not correlate with rCBF and the decreased percentage of rCBF in the foci, while it was significantly correlated with the range, number of foci, the flow deficit size and the total numbers of pixels of the foci significantly. And the patients with CN and IN did not show any difference in the presence of HSN, the manifestation on the neglect test battery and SPECT images. HSN showed damage on multiple sites, with combined damages resulting in more severe neglect.

Statistical Parametric Analysis of Cerebral Blood Flow in Vascular Dementia with Small-Vessel Disease Using 99mTc-HMPAO SPECT

Background: Subcortical ischemic vascular dementia (SVD) caused by small-artery disease is a major cause of dementia. It still remains unclear, however, whether SVD may present with localized regional cerebral blood flow (rCBF) changes. We aimed to clarify the local rCBF changes associated with dementia in patients with early-stage SVD. Methods: The subjects consisted of 15 patients with early-stage SVD [Mini Mental State Examination (MMSE) score: 20 ± 3.5] without apparent brain atrophy (SVD group), 11 patients without dementia with white matter lesions (non-dementia-WML group) and 16 age-matched controls. All the subjects were right-handed and underwent brain perfusion single photon emission computed tomography (SPECT), magnetic resonance imaging and cognitive function testing. Statistical analysis of the differences in the SPECT rCBF was performed by SPM2. The degree of severity of the WMLs was evaluated based on the Scheltens rating scale. Results: The results of SPM analysis revealed that the rCBF in the SVD group was significantly decreased in the pulvinar nuclei of the thalamus of both sides as compared with that in the controls, and in the left pulvinar nucleus as compared with that in the non-dementia-WML group. On the other hand, SPM analysis revealed no significant reduction in rCBF in the non-dementia-WML group as compared with that in the controls. The WMLs in the left parietal region were severer in the SVD group than in the non-dementia-WML group. Conclusions: In patients with early-stage SVD without apparent brain atrophy, significant rCBF reduction in the bilateral pulvinar nuclei as compared with that in normal controls, and in the left pulvinar nucleus as compared with that in patients without dementia with WMLs was found.

Preliminary clinical study of regional cerebral blood flow and hemodynamics in patients with chronic cerebrovascular insufficiency

Objective To explore the changes in regional cerebral blood flow(rCBF)and cerebral hemodynamics in patients with CCVI.Methods Twenty patients diagnosed as CCVI were enrolled to undergo single photon emission computed tomography(SPECT)rCBF imaging or transcranial Doppler uhrasonography(TCD)examination.All the patients were free from cerebral structural abnormalities as demonstrated by X-CT or magnetic resonance imaging(MRI).Cranial arteries blood flow velocity,pulsating index(PI)were measured by TCD and compared with the mean of rCBF as measured by SPECT.Results On SPECT images, decreased rCBF lesions were found in 95 percent of patients(19/20).The areas of hypoperfusion were mainly located in frontal,temporal,parietal lobes and fondues nodus.Increased cranial arteries blood flow velocity was found in the anterior cerebral artery(ACA)and middle cerebral artery(MCA)in 80 percent of patients (16/20).There were no correlations among rCBF,the decreased percentage of rCBF,average velocity,and PI of cranial arteries.Conclusions By performing SPECT rCBF and TCD on CCVI patients,the degree of changes in rCBF and hemodynamics Can be evaluated easily,which is valuable for early clinical diagnosis and treatment of CCVI. Key words: Cerebrovascular disorders; Hemodynamic processes; Brain/BS

Radiopharmaceuticals in Neurological and Psychiatric Disorders

The development of functional brain nuclear medicine techniques and their application in the investigation of neuropsychiatric disorders, have contributed significantly in the illumination of the underlying pathophysiological processes of these disorders. Furthermore, Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) brain studies provide information in early diagnosis, differential diagnosis, development of new drugs, and monitoring the response to therapeutic management. SPECT and PET brain imaging require the use of radiopharmaceuticals that cross the intact Blood Brain Barrier (BBB). Such radiotracers have been used in regional Cerebral Blood Flow (rCBF) SPECT and PET imaging and brain metabolism imaging with PET; these are well established methods in the diagnosis and management of various cerebral vascular diseases (e.g. stroke, dementia, epilepsy). Advances in radiotracer chemistry have resulted in the development of molecular imaging which represents the molecular and cellular processes of neuropsychiatric diseases. SPECT and PET molecular imaging has become available for the study of acetylcholinergic, dopaminergic and serotonergic systems, as well as for benzodiazepine and opioid receptors, with promising results. More studies are needed to validate the role of molecular imaging in the clinical practice of neuropsychiatric disorders.

Evaluation of reconstruction techniques in regional cerebral blood flow SPECT using trade-off plots: A Monte Carlo study

The image quality of single photon emission computed tomography (SPECT) depends on the reconstruction algorithm used. The purpose of the present study was to evaluate parameters in ordered subset expectation maximization (OSEM) and to compare systematically with filtered back-projection (FBP) for reconstruction of regional cerebral blood flow (rCBF) SPECT, incorporating attenuation and scatter correction. The evaluation was based on the trade-off between contrast recovery and statistical noise using different sizes of subsets, number of iterations and filter parameters. Monte Carlo simulated SPECT studies of a digital human brain phantom were used. The contrast recovery was calculated as measured contrast divided by true contrast. Statistical noise in the reconstructed images was calculated as the coefficient of variation in pixel values. A constant contrast level was reached above 195 equivalent maximum likelihood expectation maximization iterations. The choice of subset size was not crucial as long as there were > or = 2 projections per subset. The OSEM reconstruction was found to give 5-14% higher contrast recovery than FBP for all clinically relevant noise levels in rCBF SPECT. The Butterworth filter, power 6, achieved the highest stable contrast recovery level at all clinically relevant noise levels. The cut-off frequency should be chosen according to the noise level accepted in the image. Trade-off plots are shown to be a practical way of deciding the number of iterations and subset size for the OSEM reconstruction and can be used for other examination types in nuclear medicine.

A comparison of the effects of citalopram and moclobemide on resting brain perfusion in social anxiety disorder

The serotonin specific reuptake inhibitor (SSRI) citalopram and the reversible mono-amine oxidase-A inhibitor (RIMA) moclobemide have both been used successfully for the treatment of social anxiety disorder (SAD). In this study we investigate the effects of these compounds on resting brain function using single photon emission computed tomography (SPECT). Subjects meeting DSM-IV criteria for SAD underwent regional cerebral blood flow (rCBF) SPECT using Tc-HMPAO at baseline and after 8 weeks of treatment with either citalopram or moclobemide. Using statistical parametric mapping brain SPECT studies were analysed to determine the effects of treatment on rCBF, to compare the effects of citalopram and moclobemide, and to detect correlations between changes in rCBF and clinical response. Subjects received citalopram (n=17) or moclobemide (n=14) as therapy. Subjects in both treatment groups demonstrated a significant improvement of SAD symptoms as measured by the Liebowitz Social Anxiety Scale total score. All subjects demonstrated a decrease in rCBF in the insulae post therapy. Subjects receiving citalopram had decreased superior cingulate rCBF after therapy compared to those receiving moclobemide. Both SSRI's and RIMA's decreased rCBF in the insulae during treatment of SAD; an effect that may be consistent with the role of these regions in processing internal somatic cues evoked by emotional stimuli. Citalopram had a greater effect on superior cingulate perfusion, an effect that is consistent with evidence of high levels of 5-HT transporters in this region.

The prediction of rapid conversion to Alzheimer's disease in mild cognitive impairment using regional cerebral blood flow SPECT

Mild cognitive impairment (MCI) comprises a heterogeneous group with a variety of clinical outcomes and they are at risk for developing Alzheimer's disease (AD). The prediction of conversion from MCI to AD using the initial neuroimaging studies is an important research topic. We investigated the initial regional cerebral blood flow (rCBF) measurements using single photon emission computed tomography (SPECT) in individuals with 76 amnesic MCI (52 subjects converted to AD and 24 subjects did not convert to AD at 3-year follow-up) and 57 age- and gender-matched controls. We sought functional profiles associated with conversion to AD, then evaluated the predictive value of the initial rCBF SPECT. As compared with controls, AD converters demonstrated reduced blood flow in the bilateral parahippocampal gyri, precunei, posterior cingulate cortices, bilateral parietal association areas, and the right middle temporal gyrus. Non-converters also demonstrated significant reduction of rCBF in the posterior cingulated cortices and the right caudate nucleus when compared to controls. As compared with non-converters, converters showed reductions of rCBF in the bilateral temporo-parietal areas and the precunei. The logistic regression model revealed that reduced rCBF in the inferior parietal lobule, angular gyrus, and precunei has high predictive value and discriminative ability. Although a cross-validation study is needed to conclude the usefulness of rCBF SPECT for the prediction of AD conversion in individuals with MCI, our data suggest that the initial rCBF SPECT studies of individuals with MCI may be useful in predicting who will convert to AD in the near future.

Combined 99mTc-ECD SPECT and neuropsychological studies in MCI for the assessment of conversion to AD

Identifying pre-clinical Alzheimer's disease (AD) in subjects with mild cognitive impairment (MCI) is a major issue in clinical diagnosis. Establishing a combination of predictive markers from different fields of research might help in increasing the diagnostic accuracy. Aim of this study was to evaluate the potential role of 99mTc-ECD single photon emission computed tomography (SPECT) and memory scores in predicting conversion to AD in MCI subjects. Thirty-one MCI subjects underwent a clinical and neuropsychological examination, and a regional cerebral blood flow (rCBF) SPECT scan at baseline. Subjects had been followed periodically through 2 years in order to monitor the progression of cognitive symptoms. Canonical variate analysis of principal components was able to separate all subjects who converted to AD from those who remained stable, the former being characterized by a specific hypometabolic pattern, involving the parietal and temporal lobes, precuneus, and posterior cingulate cortex. Canonical correlation analysis of combined baseline memory deficits and rCBF SPECT images identified pre-clinical AD with a sensitivity and specificity of 77.8%. The pattern of hypoperfusion 99mTc-ECD SPECT and the severity of memory deficits predict the risk of progression to probable AD dementia in MCI subjects.

Relation between medial temporal atrophy and functional brain activity during memory processing in Alzheimer’s disease: a combined MRI and SPECT study

Objective: To investigate the relation between atrophy of the hippocampal region and brain functional patterns during episodic memory processing in Alzheimer’s disease. Patients and methods: Whole brain structural magnetic resonance...

Electroencephalography and single photon emission computed tomography in dementia: a comparative study.

A series of elderly patients with dementia of Alzheimer type (AD), multi-infarct dementia (MID) and functional (non-organic) psychiatric illness (major depressive disorder) were selected according to DSM-III-R criteria and received: a battery of cognitive tests, EEG and Single Photon Emission Computed Tomography (SPECT) using 99mTc HMPAO. The EEG and SPECT scans were examined independently of the clinical data. The former were divided into two abnormal categories, those showing AD type change and vascular change respectively, and a normal group. The SPECT scans were classified as follows: a SPECT rCBF pattern showing bilateral temporoparietal perfusion deficits (AD type); those showing single focal perfusion deficits or multiple areas of low perfusion in the cerebral cortex suggestive of ischaemic change (vascular type SPECT picture); a mixed AD/MID pattern; and those with normal scan findings. There were significant associations between clinical diagnosis, EEG rating and SPECT rCBF pattern, approximately three-quarters of AD and MID patients having the predicted EEG and scan changes. Normal EEG recordings were more common in the MID patients. The two tests agreed in about two-thirds of cases, with no consistent pattern apparent in the cases with divergent findings. Each test misclassified a minority of dementia patients, but in only one patient were both investigations normal. Almost half of the so called 'functionally ill' patients had abnormal rCBF changes, showing mainly vascular changes while one-fifth had abnormal EEGs.

Brain single photon emission computed tomography: Newer activation and intervention studies

Single-photon emission computed tomography (SPECT) regional cerebral blood flow (rCBF) findings using non-xenon 133 tracers in combination with activation and intervention techniques are reviewed. Examination of the currently available data indicates that it is possible to detect the effects of a variety of activations and interventional procedures using SPECT rCBF with non-xenon 133 tracers. There are still many issues to be resolved before SPECT can reach the level of sophistication attained by xenon 133 and positron emission tomography in studying rCBF during activation or intervention. However, research to date indicates that SPECT rCBF studied with tracers other than xenon 133 has an excellent potential for increasing the ability to differentiate normal and pathological states.

Single photon tomography in Alzheimer's disease and the dementias

Measurements of brain blood flow has evolved over the past 50 years, and during the latter half of that time radionuclide techniques have been used to study this important function. Using Xenon 133 and scintillation multiprobe systems, several teams of investigators measured regional cerebral blood flow (rCBF), and noted that under many circumstances it could be equated with local brain physiological activity. The dementias were investigated using the scintillation multiprobe method, and posterior flow deficits were described in patients who were thought to have Alzheimer's disease. The multiprobe technique gave way first to planar, and then tomographic imaging, with initial favorable results achieved by positron emission tomography (PET). Soon investigators learned to measure rCBF with single-photon emission computed tomography (SPECT) using high-sensitivity systems and 133Xe as a tracer, or high-resolution systems with 123I-iodoamphetamine (IMP), and later, 99mTc-HMPAO. Three-dimensional tomographic imaging shows to advantage the flow patterns that characterize Alzheimer's disease, with rCBF reductions in temporal, parietal, and sometimes frontal areas, as opposed to randomly distributed deficits in multiinfarct dementia, reduced frontal flow in entities such as Pick's disease, and others. Herein we will review our own experience with high-sensitivity rCBF SPECT in 119 patients with dementia, and with high-resolution SPECT, using a new, three-camera scanner and 99mTc-HMPAO in an additional 39 patients. SPECT rCBF study of patients with dementia and Alzheimer's disease, will aid in separating patients with untreatable Alzheimer's from those patients who may have treatable causes of dementia, and will be useful in evaluating experimental drugs for the treatment of Alzheimer's disease.