Regional Cerebral Blood Flow Imaging Research Articles

Alzheimer’s disease pattern derived from relative cerebral flow as an alternative for the metabolic pattern using SSM/PCA

Background2-Deoxy-2-[18F]fluoroglucose (FDG) PET is an important tool for the identification of Alzheimer’s disease (AD) patients through the characteristic neurodegeneration pattern that these patients present. Regional cerebral blood flow (rCBF) images derived from dynamic 11C-labelled Pittsburgh Compound B (PIB) have been shown to present a similar pattern as FDG. Moreover, multivariate analysis techniques, such as scaled subprofile modelling using principal component analysis (SSM/PCA), can be used to generate disease-specific patterns (DP) that may aid in the classification of subjects. Therefore, the aim of this study was to compare rCBF AD-DPs with FDG AD-DP and their respective performances. Therefore, 52 subjects were included in this study. Fifteen AD and 16 healthy control subjects were used to generate four AD-DP: one based on relative cerebral trace blood (R1), two based on time-weighted average of initial frame intervals (ePIB), and one based on FDG images. Furthermore, 21 subjects diagnosed with mild cognitive impairment were tested against these AD-DPs.ResultsIn general, the rCBF and FDG AD-DPs were characterized by a reduction in cortical frontal, temporal, and parietal lobes. FDG and rCBF methods presented similar score distribution.ConclusionrCBF images may provide an alternative for FDG PET scans for the identification of AD patients through SSM/PCA.

Influence of the Imaging Method on Regional Cerebral Blood Flow Value in Arterial Spin Labeling (ASL): Comparison of Pulsed-ASL with Two-dimensional Acquisition and Pseudo-continuous-ASL with 3D Spiral Acquisition

The purposes of this study were to compare regional cerebral blood flow (rCBF) images acquired by the pulsed arterial spin labeling with two-dimensional acquisition (PASL-2D) and the pseudo-continuous-ASL with three-dimensional spiral acquisition (pCASL-3D spiral), and to clarify the characteristics of rCBF values in both ASL methods. PASL-2D and pCASL-3D spiral were performed in five healthy volunteers with no history of brain disease using 3T scanners from two venders in the same center. 3D T1-weighted images and rCBF images were acquired by both ASL methods for a total of 3 sessions: twice at the initial visit (1st and 2nd), and 1 hour and 1 week later. The rCBF images calculated by each MR machine were anatomically standardized using SPM12. The regions of interest (ROIs) were set on the territory of the anterior cerebral artery (ACA), the middle cerebral artery (MCA), and the posterior cerebral artery (PCA). Mean and relative rCBF values were calculated at each arterial territory in each session. Reproducibility for rCBF value in each method was analyzed using Bland-Altman plots, the coefficient of repeatability (CR), and the repeatability index (RI). In all sessions, mean values of rCBF were the highest at PCA for PASL-2D and at MCA for pCASL-3D spiral. RIs of pCASL-3D spiral were lower than those of PASL-2D in all arterial territories. In the PASL-2D and the pCASL-3D spiral, we confirmed the characteristics of the mean and reproducibility of rCBF values in each arterial territory.

Clinical value of brain CT perfusion imaging combined with head and neck CTA in the diagnosis of acute ischemic stroke

Objective To investigate the clinical value of whole brain CT perfusion imaging combined with head and neck CTA in the diagnosis of acute ischemic stroke. Methods From November 2016 to November 2018, the clinical data and medical imaging data of 220 patients diagnosed as acute ischemic stroke in the Department of Neurology, Dajiangdong Hospital were selected.All patients underwent CT scan followed by a CT perfusion scan and a routine cranial CTA.The radiation dose was recorded.The ischemic lesions and their stenosis were analyzed by CTA.CT perfusion imaging was used to analyze regional cerebral blood flow imaging (rCBF), tissue perfusion (rCBV) and mean passage time (MTT) in all patients..And the test performance of the two inspection methods was compared. Results CTA was used to analyze vascular stenosis.The stenotic vessels were mainly distributed in the M1~M3 segment (3 cases of them were completely obstructed, 11 cases were obstructed ≥50%, 19 cases were 30% ≤ stenosis<50%), and A1~A3 segments (4 cases of them were obstructed, 7 cases were 30% ≤ stenosis<50%), and basilar artery (2 cases of them occlusion, 6 cases of ≥ 50%, 11 cases of 30% ≤ stenosis<50%). CT perfusion examination was performed in the whole brain.The rCBF of the control area was higher than that of the ischemic penumbra and higher than the infarct area.The rCBF values were (50.31±11.21)100 g/min, (34.45±22.17)100 g/min and (6.87±3.52)100 g/min, respectively, the difference was statistically significant (t=17.81, 19.14, all P<0.05). The region rCBV of the control area was higher than that of the ischemic penumbra and the infarct region, and the rCBV values were (3.35±1.01)mL/100g, (2.87±0.55)mL/100g and (6.87±0.51)mL/100g, respectively, the differences are statistically significant (t=6.47, 9.19, all P<0.05). The MTT in the control area was lower than that in the ischemic penumbra and the infarct area, and the MTT values were (4.52±1.21)s, (7.88±1.01)s and (11.81±1.18)s, respectively, the differences are statistically significant(t=10.50, 13.54, all P<0.05). The two methods were compared for consistency, and the kappa value was greater than 0.75, showed a high degree of consistency. Conclusion CT perfusion imaging and CTA have little difference in the diagnostic efficacy for patients with acute ischemic cerebral infarction, and can accurately diagnose the disease.CT perfusion imaging can determine the location of the ischemic penumbra, and CTA can be analyzed based on the stage of the diseased vessel.Both two methods can play different guiding role for individualized treatment. Key words: Tomography, spiral computed; Perfusion imaging; Angiography; Cerebrovascular disorders; Retrospective study

Synthesis of [1–11C]Butanol via a facile solid phase extraction protocol

A facile synthesis method for the preparation of [1–11C]butanol, a regional cerebral blood flow imaging agent, was developed. Using a solid phase extraction method, the highly polar and volatile molecule [1–11C]butanol was quickly concentrated, purified, and released as final product; boasting high radiochemical and chemical purities as well as high radiochemical yields. The final drug product was obtained as a sterile, pyrogen-free solution that conforms United States Pharmacopeia (USP) <823> requirements.

Comparison of simultaneous arterial spin labeling MRI and 15O-H2O PET measurements of regional cerebral blood flow in rest and altered perfusion states

Arterial spin labelling (ASL) is a non-invasive magnetic resonance imaging (MRI) technique that may provide fully quantitative regional cerebral blood flow (rCBF) images. However, before its application in clinical routine, ASL needs to be validated against the clinical gold standard, 15O-H2O positron emission tomography (PET). We aimed to compare the two techniques by performing simultaneous quantitative ASL-MRI and 15O-H2O-PET examinations in a hybrid PET/MRI scanner. Duplicate rCBF measurements were performed in healthy young subjects (n = 14) in rest, during hyperventilation, and after acetazolamide (post-ACZ), yielding 63 combined PET/MRI datasets in total. Average global CBF by ASL-MRI and 15O-H2O-PET was not significantly different in any state (40.0 ± 6.5 and 40.6 ± 4.1 mL/100 g/min, respectively in rest, 24.5 ± 5.1 and 23.4 ± 4.8 mL/100 g/min, respectively, during hyperventilation, and 59.1 ± 10.4 and 64.7 ± 10.0 mL/100 g/min, respectively, post-ACZ). Overall, strong correlation between the two methods was found across all states (slope = 1.01, R2 = 0.82), while the correlations within individual states and of reactivity measures were weaker, in particular in rest (R2 = 0.05, p = 0.03). Regional distribution was similar, although ASL yielded higher perfusion and absolute reactivity in highly vascularized areas. In conclusion, ASL-MRI and 15O-H2O-PET measurements of rCBF are highly correlated across different perfusion states, but with variable correlation within and between hemodynamic states, and systematic differences in regional distribution.

Diagnostic performance of regional cerebral blood flow images derived from dynamic PIB scans in Alzheimer\u2019s disease

BackgroundIn clinical practice, visual assessment of glucose metabolism images is often used for the diagnosis of Alzheimer’s disease (AD) through 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET) scans. However, visual assessment of the characteristic AD hypometabolic pattern relies on the expertise of the reader. Therefore, user-independent pipelines are preferred to evaluate the images and to classify the subjects. Moreover, glucose consumption is highly correlated with cerebral perfusion. Regional cerebral blood flow (rCBF) images can be derived from dynamic 11C-labelled Pittsburgh Compound B PET scans, which are also used for the assessment of the deposition of amyloid-β plaques on the brain, a fundamental characteristic of AD. The aim of this study was to explore whether these rCBF PIB images could be used for diagnostic purposes through the PMOD Alzheimer’s Discrimination Tool.ResultsBoth tracer relative cerebral flow (R1) and early PIB (ePIB) (20–130 s) uptake presented a good correlation when compared to FDG standardized uptake value ratio (SUVR), while ePIB (1–8 min) showed a worse correlation. All receiver operating characteristic curves exhibited a similar shape, with high area under the curve values, and no statistically significant differences were found between curves. However, R1 and ePIB (1–8 min) had the highest sensitivity, while FDG SUVR had the highest specificity.ConclusionrCBF images were suggested to be a good surrogate for FDG scans for diagnostic purposes considering an adjusted threshold value.

Regional Cerebral Blood Flow in [123]I-IMP Single-photon Emission Computed Tomography and the Wechsler Memory Scale-revised in Nondemented Elderly Subjects with Subjective Cognitive Impairment.

Objective Regional cerebral blood flow (rCBF) imaging with single-photon emission computed tomography (SPECT) is useful in the early diagnosis of dementia. We aimed to investigate the association between the rCBF and various domains related to the memory function in elderly subjects with subjective cognitive impairment (SCI). Methods Thirty-two subjects with SCI were included in the present study. Patients with dementia and mild cognitive impairment (MCI) were excluded based on the presence of logical memory impairment. N-isopropyl-p-[123I]-iodoamphetamine SPECT was performed and Wechsler Memory Scale-Revised (WMS-R) was administered to all subjects (mean age, 68.4 years; average Mini-Mental State Examination score, 27.6). The SPECT results were analyzed using the easy Z-score imaging system and the voxel-based stereotactic extraction estimation method. Correlation analyses were performed to investigate the correlation between the mean positive Z-scores in the decrease of the rCBF and the WMS-R indices. Results The SPECT study indicated marked hypoperfusion in some areas, including the bilateral temporal areas, the caudate, and the thalamus, in these subjects in comparison to the normal database. The decrease in the rCBF that was observed in several regions, including the left precuneus and left inferior frontal gyrus (LIFG), showed a significant negative correlation with several indices of the memory function, particularly visual memory. Conclusion The regional hypoperfusion observed in the study using the voxel-based stereotactic extraction estimation method suggest that the regional cerebral dysfunction is associated with the memory function of patients with SCI, even though the subjects in the present study were cognitively intact. The correlation analysis with the WMS-R suggested the contribution of the LIFG to the memory function and indicated the significance of visual memory dysfunction in the neuropsychological assessment to determine the stage of SCI.

Relationship between regional cerebral blood flow and neuropsychiatric symptoms in dementia with Lewy bodies.

This aim of this study was to examine the mechanisms underlying the neuropsychiatric symptoms in dementia with Lewy bodies by investigating regional cerebral blood flow. Participants were 27 patients who fulfilled the diagnostic criteria for probable dementia with Lewy bodies. All subjects underwent single-photon emission computed tomography scans using technetium-99 m hexamethylpropyleneamine oxime. Neuropsychiatric symptoms were evaluated by neuropsychiatric inventory. Multiple regression analyses using neuropsychiatric inventory and voxel-based analyses of covariance of the regional cerebral blood flow images between subjects with or without each neuropsychiatric symptom were performed. Additionally, similar voxel-based analyses of covariance between subjects with each neuropsychiatric symptom and normal subjects were performed. There were no significant correlations in any psychiatric symptoms in multiple regression analyses. All subjects had hallucination but none had euphoria. We analyzed eight neuropsychiatric symptom scores with the exception of hallucination and euphoria using voxel-based analyses of covariance. Significant differences of regional cerebral blood flow were shown in groups with agitation, disinhibition, and irritability. Subjects with agitation showed hypoperfusion in the parietal lobule, the precuneus, and the angular gyrus, and hyperperfusion in the fusiform gyrus, the lingual gyrus, and the thalamus. Subjects with disinhibition showed hypoperfusion in the left frontal gyrus. Subjects with irritability showed hyperperfusion in the right frontal gyrus. There were no significant differences in regional cerebral blood flow between subjects with any neuropsychiatric symptoms and normal subjects. This study reveals that dysfunction of specific brain regions is associated with various neuropsychiatric symptoms in dementia with Lewy bodies.

Impact of Methamphetamine on Regional Metabolism and Cerebral Blood Flow After Traumatic Brain Injury

Substance abuse is a frequent comorbid condition among patients with traumatic brain injury (TBI), but little is known about its potential additive or interactive effects on tissue injury or recovery from TBI. This study aims to evaluate changes in regional metabolism and cerebral perfusion in subjects who used methamphetamine (METH) prior to sustaining a TBI. We hypothesized that METH use would decrease pericontusional cerebral perfusion and markers of neuronal metabolism, in TBI patients compared to those without METH use. This is a single center prospective observational study. Adults with moderate and severe TBI were included. MRI scanning was performed on a 3 Tesla scanner. MP-RAGE and FLAIR sequences as well as Metabolite spectra of NAA and lactate in pericontusional and contralateral voxels identified on the MP-RAGE scans. A spiral-based FAIR sequence was used for the acquisition of cerebral blood flow (CBF) maps. Regional CBF images were analyzed using ImageJ open source software. Pericontusional and contralateral CBF, NAA, and lactate were assessed in the entire cohort and in the METH and non-METH groups. Seventeen subjects completed the MR studies. Analysis of entire cohort: pericontusional NAA concentrations (5.81 ± 2.0 mM/kg) were 12% lower compared to the contralateral NAA (6.98 ± 1.2 mM/kg; p = 0.03). Lactate concentrations and CBF were not significantly different between the two regions; however, regional CBF was equally reduced in the two regions. Subgroup analysis: 41% of subjects tested positive for METH. The mean age, Glasgow Coma Scale, and time to scan did not differ between groups. The two subject groups also had similar regional NAA and lactate. Pericontusional CBF was 60% lower in the METH users than the non-users, p = 0.04; contralateral CBF did not differ between the groups. This small study demonstrates that tissue metabolism is regionally heterogeneous after TBI and pericontusional perfusion was significantly reduced in the METH subgroup.

Schizophrenia with preserved insight is associated with increased perfusion of the precuneus.

Preserved insight into illness has been suggested to be predictive of outcome in patients with schizophrenia. We aimed to investigate the functional substrate underlying preserved insight in these patients. We recruited patients with paranoid schizophrenia and healthy controls matched for age and sex. Patients were grouped according to preserved or impaired insight into illness using the Scale to assess Unawareness of Mental Disorder (SUMD). Whole-brain technetium-99m ethyl cysteinate dimer single photon emission computed tomography regional cerebral blood flow was compared at the voxel level between the 2 groups using a statistical parametric map (voxel-level significance of p < 0.001, uncorrected; cluster level significance of p < 0.05, uncorrected). We enrolled 31 right-handed patients with schizophrenia and 18 controls in our study. Twenty-one (67.7%) patients had preserved insight. The 2 groups did not differ significantly in demographic and clinical characteristics or in treatment. Compared with controls, the whole group of patients showed bilateral frontotemporal hypoperfusions, with no statistical difference between patients with preserved or impaired insight for these areas. Patients with preserved insight showed significantly increased perfusion of the bilateral precuneus relative to those with impaired insight. Patients with subtypes other than paranoid schizophrenia have to be investigated to assess whether involvement of the precuneus in patients with preserved insight can be identified across the full spectrum of subtypes and symptoms of schizophrenia. Moreover, our study concerned only the central dimension (awareness of mental disorder) of 1 scale (SUMD); other dimensions of insight could be studied. Our results show that schizophrenia with preserved insight is associated with greater perfusion of the precuneus, a brain area known to be involved in self- consciousness, suggesting a compensatory mechanism of fronto-temporal impairment.

Returning from Oblivion: Imaging the Neural Core of Consciousness

One of the greatest challenges of modern neuroscience is to discover the neural mechanisms of consciousness and to explain how they produce the conscious state. We sought the underlying neural substrate of human consciousness by manipulating the level of consciousness in volunteers with anesthetic agents and visualizing the resultant changes in brain activity using regional cerebral blood flow imaging with positron emission tomography. Study design and methodology were chosen to dissociate the state-related changes in consciousness from the effects of the anesthetic drugs. We found the emergence of consciousness, as assessed with a motor response to a spoken command, to be associated with the activation of a core network involving subcortical and limbic regions that become functionally coupled with parts of frontal and inferior parietal cortices upon awakening from unconsciousness. The neural core of consciousness thus involves forebrain arousal acting to link motor intentions originating in posterior sensory integration regions with motor action control arising in more anterior brain regions. These findings reveal the clearest picture yet of the minimal neural correlates required for a conscious state to emerge.

Common and Differential Pathophysiological Features Accompany Comparable Cognitive Impairments in Medication-Free Patients with Schizophrenia and in Healthy Aging Subjects

Dysfunction of the dorsolateral prefrontal cortex (DLPFC) and parahippocampal region along with poor working memory are common neurophysiological and behavioral features associated with schizophrenia and normal aging. It is, however, unknown whether the associated patterns of neural activation differ between these two groups when their cognitive performance is closely matched in a pairwise manner. The authors sought to pinpoint common and differential pathophysiological features that accompany comparable working memory impairments in schizophrenia and healthy aging. Fifty-three subjects were scanned with oxygen-15 water positron emission tomography regional cerebral blood flow measurements during working memory. Seventeen medication-free patients with schizophrenia were individually matched for working memory performance with 17 healthy aging subjects. Brain activation of the two index groups were compared with each other and with 19 young healthy individuals. Patients with schizophrenia showed right DLPFC hypoactivation, both when compared with age-matched control subjects and after direct comparison with working memory performance-matched elderly subjects. Moreover, both groups with working memory deficits shared an inability to suppress parahippocampal and anterior medial prefrontal cortex activation. These results provide new insights into the mechanisms by which impaired working memory performance can arise by showing that both common (parahippocampal/anterior medial PFC) and differential (DLPFC) pathophysiological features accompany similar cognitive impairments. The aging data also demonstrate that poor performance is not necessarily accompanied by the DLPFC hypofunction that was seen in schizophrenia. Finally, these results more closely link the DLPFC functional abnormalities in schizophrenia to the pathophysiology of the disorder rather than to poor performance per se.

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.

Blood Flow Imaging of the Brain: 50 Years Experience

Blood Flow Imaging of the Brain: 50 Years Experience

Regional cerebral blood flow in a patient with Nasu-Hakola disease

We report a functional neuroimaging study of a 43-year-old woman with Nasu-Hakola disease (NHD). Regional cerebral blood flow (rCBF) images were measured with technetium-99m ethyl cysteinate dimer single photon emission computed tomography (SPECT). rCBF was decreased in the bilateral frontal lobes and thalamus. This finding was consistent with the known underlying neuropathology in patients with NHD. Brain SPECT is useful for demonstrating the pathophysiologic brain region in patients with NHD.

Chiral ligand-exchange chromatography as the screening method for proposed modifications in exametazime synthesis to enhance diastereoselectivity

99mTc(V)- d, l-HM-PAO complex is well-known radiopharmaceutical for regional cerebral blood flow imaging. The proposed modifications in exametazime, hexamethylpropyleneamine oxime (HM-PAO) (4,8-diaza-3,6,6,9-tetramethylundecane-2,10-dione bisoxime) synthesis, for reduction of intermediary reactant diiminebisoxime (DI) (4,8-diaza-3,6,6,9-tetramethylundecane-3,8-diene-2,10-dione bisoxime) concerned two reductants (NaBH 4 and KBH 4), two solvents (ethanol and 2-propanol), and three mole ratios of reactant/reductants (1:1, 1:1.5, and 1:2). The simultaneous analysis of diastereo–enantiomeric HM-PAO content, as well as the content of starting DI, in different reduction mixtures were performed using chiral ligand-exchange chromatography (CLEC). The separation of the samples of investigated reduction mixtures, obtained in the second step of HM-PAO synthesis, has been accomplished by using an achiral sorbent (RP-18) and a chiral mobile phase (CMP) containing copper(II) complex with N, N-dimethyl- l-phenylalanine ( l-DM-PhA) as initial complex for CLEC. With 12 different reduction conditions, the obtained ratios of diastereoisomers d, l-HM-PAO : meso-HM-PAO varied from 69.2:30.8 to 15.9:84.1, in comparison to the reduction in routine synthesis of HM-PAO which gives an equal mixture of diastereoisomers. The ternary mixed complexes formation recorded spectrophotometrically on addition of HM-PAO or DI to the mobile phase with binary complex Cu( l-DM-PhA) 2, due to the evidence of bathochromic shift of 46 nm for λ max with significant difference in absorptivity contributes to separation mechanism.

Brain temperature and cerebral blood flow imaging in patients with severe subarachnoid hemorrhage: report of two cases

Background Temperature reversal, which is defined as observation of higher brain temperature than systemic temperature followed by lower brain temperature than systemic temperature, implies a poor prognosis in patients with severe subarachnoid hemorrhage (SAH). Serial regional cerebral blood flow (CBF) imaging using single-photon emission tomography (SPECT) was performed in 2 patients with severe SAH who showed temperature reversal. Case description 54-year-old woman and a 55-year-old man with severe SAH underwent ventricular drainage using a catheter that allowed monitoring of the brain temperature. SPECT imaging in these two patients showed that CBF was preserved before the occurrence of the temperature reversal and was exhausted afterwards. These patients died within 2 to 3 days. Conclusions Temperature reversal may indicate the exact time when absence of brain perfusion occurs, causing irreversible brain damage.

Neurocognition and PET

In cognitive neuroscience regional cerebral blood flow (rCBF) imaging with positron-emission-tomography (PET) is a powerful tool to characterize different aspects of cognitive processes by using different data analysis approaches. By use of an n-back verbal working memory task (varied from 0- to 3-back) we present cognitive subtraction analysis as basic strategy as well as parametric and covariance analyses and discuss the results. Correlation analyses were performed using the individual performance rate as an external covariate, computing inter-regional correlations, and as network analysis applying structural equation modelling to evaluate the effective connectivity between the involved brain regions. Subtraction analyses revealed a fronto-parietal neuronal network also including the anterior cingulate cortex and the cerebellum. With higher memory load the parametric analysis evidenced linear rCBF increases in prefrontal, pre-motor and inferior parietal areas including the precuneus as well as in the anterior cingulate cortex. The rCBF correlation with the individual performance as external covariate depicted negative correlations in bilateral prefrontal and inferior parietal regions, in the precuneus and the anterior cingulate cortex. The network analysis demonstrated mainly occipito-frontally directed interactions which were predominantly left-hemispheric. Additionally, strong linkages were found between extrastriate and parietal regions as well as within the parietal cortex. The data analysis approaches presented here contribute to an extended and more elaborated understanding of cognitive processes and their different sub-aspects.

Statistical parametric mapping in brain single photon computed emission tomography after carbon monoxide intoxication.

The purpose of this retrospective study was to assess regional cerebral blood flow in patients after carbon monoxide intoxication by using brain single photon emission computed tomography and statistical parametric mapping. Eight patients with delayed neuropsychiatric sequelae and ten patients with no neuropsychiatric symptoms after carbon monoxide intoxication were studied with brain single photon emission tomography imaging with 99mTc-hexamethyl-propyleneamine oxime. Forty-four control subjects were also studied. We used the adjusted regional cerebral blood flow images in relative flow distribution (normalization of global cerebral blood flow for each subject to 50 ml x 100 g(-1) x min(-1) with proportional scaling) to compare these groups with statistical parametric mapping. Using this technique, significantly decreased regional cerebral blood flow was noted extensively in the bilateral frontal lobes as well as the bilateral insula and a part of the right temporal lobe in the patients with delayed neuropsychiatric sequelae as compared with normal volunteers (P< 0.005). In the patients with no neuropsychiatric symptoms, significantly decreased regional blood flow in the bilateral frontal lobes particularly on the left side was detected. There was a significantly decreased regional cerebral blood flow in the right frontal lobe and insula in the patients with delayed neuropsychiatric sequelae as compared to those with no neuropsychiatric sequelae. It is concluded that statistical parametric mapping is a useful technique for highlighting differences in regional cerebral blood flow in patients following carbon monoxide intoxication as compared with normal volunteers. The selectively reduced blood flow noted in this investigation supports the contention that the decrease following carbon monoxide intoxication may be prolonged and further worsen in the frontal lobe. In addition, the present study may help to clarify the characteristics of the pathophysiological alteration underlying delayed neuropsychiatric sequelae.

Central activation by histamine-induced itch: analogies to pain processing: a correlational analysis of O-15 H 2O positron emission tomography studies

The aim of this study was to identify the functional cerebral network involved in the central processing of itch and to detect analogies and differences to previously identified cerebral activation patterns triggered by painful noxious stimuli. Repeated positron emission tomography regional cerebral blood flow (rCBF) measurements using O 15-labeled water were performed in six healthy right-handed male subjects (mean age 32±2 years). Each subject underwent 12 sequential rCBF measurements. In all subjects a standardized skin prick test was performed on the right forearm 2 min before each rCBF measurement. For activation, histamine was applied in nine tests in logarithmically increasing concentrations from 0.03 to 8%. Three tests were performed with isotonic saline solution serving as a control condition. Itch intensity and unpleasantness were registered with a visual analogue scale during each test. Subtraction analysis between activation and control conditions as well as correlation analysis with covariates were performed. Itch induced a significant activation in the predominantly contralateral somatosensory cortex and in the ipsilateral and contralateral motor areas (supplementary motor area (SMA), premotor cortex, primary motor cortex). Additional significant activations were found in the prefrontal cortex and the cingulate gyrus, but not in subcortical structures nor in the secondary somatosensory cortex. In correlation analyses, several cortical areas showed a graded increase in rCBF with the logarithm of the histamine concentration (bilateral sensorimotor areas and cingulate cortex; contralateral insula, superior temporal cortex and prefrontal cortex) and with itch unpleasantness (contralateral sensorimotor cortex, prefrontal cortex and posterior insula; ipsilateral SMA). Induction of itch results in the activation of a distributed cerebral network. Itch and pain seem to share common pathways (a medial and a lateral processing pathway and a strong projection to the motor system). In contrast to pain activation studies, no subcortical (i.e. thalamic) activations were detected and correlation analyses suggest differences in subjective processing of the two sensations.