A quantitative approach to technetium-99m hexamethylpropylene amine oxime

Near-Infrared Time-Resolved Spectroscopy Shows Anterior Prefrontal Blood Volume Reduction in Schizophrenia but Not in Major Depressive Disorder

Previous studies using various brain imaging methods have reported prefrontal blood flow disturbances in psychiatric disorders, including schizophrenia and major depressive disorder. In both disorders, alterations of the resting blood flow, in addition to that of the activation in response to task load, have been shown, but the results are not consistent. The present study aimed to examine the anterior prefrontal hemoglobin concentration at the resting state in schizophrenia and depression using near-infrared time-resolved spectroscopy (NIR-TRS), which estimates the optical absorption coefficients and calculates the absolute concentrations of oxygenated (oxy-Hb), deoxygenated (deoxy-Hb), and total (total-Hb; sum of oxy-Hb and deoxy-Hb) hemoglobin. Their ratios to systemic blood hemoglobin concentration (blood-Hb) were also assessed. In agreement with our previous data, total-Hb and total-Hb/blood-Hb in schizophrenia were significantly lower. The present study further revealed that both oxy-Hb/blood-Hb and deoxy-Hb/blood-Hb in schizophrenia were reduced. In depression, total-Hb, total-Hb/blood-Hb, oxy-Hb, and oxy-Hb/blood-Hb were higher than in schizophrenia and were not different from the control. The oxygen saturation (oxy-Hb/total-Hb), in addition to the optical pathlengths, did not show group differences. Lowered oxy-Hb/blood-Hb and deoxy-Hb/blood-Hb together with unchanged oxygen saturation may indicate that the prefrontal blood volume is reduced in schizophrenia. The present findings suggest that NIR-TRS is useful in analyzing the hemodynamic aspects of prefrontal dysfunction in schizophrenia and differentiating schizophrenia from depression.

Relationship between motor learning and gambling propensity in Parkinson's disease

INTRODUCTION

The basal ganglia and related dopaminergic cortical areas are important neural systems underlying motor learning and are also implicated in impulse control disorders (ICDs). Motor learning impairments and ICDs are frequently observed in Parkinson's disease (PD). Nevertheless, the relationship between motor learning ability and ICDs has not been elucidated.

METHODS

We examined the relationship between motor learning ability and gambling propensity, a possible symptom for prodromal ICDs, in PD patients. Fifty-nine PD patients without clinical ICDs and 43 normal controls (NC) were administered a visuomotor rotation perturbation task and the Iowa Gambling Task (IGT) to evaluate motor learning ability and gambling propensity, respectively. Participants also performed additional cognitive assessments and underwent brain perfusion SPECT imaging.

RESULTS

Better motor learning ability was significantly correlated with lower IGT scores, i.e., higher gambling propensity, in PD patients but not in NC. The higher scores on assessments reflecting prefrontal lobe function and well-preserved blood perfusion in prefrontal areas were correlated with lower IGT scores along with better motor learning ability.

CONCLUSIONS

Our findings suggest that better motor learning ability and higher gambling propensity are based on better prefrontal functions, which are in accordance with the theory that the prefrontal cortex is one of the common essential regions for both motor learning and ICDs.

Validity of the γ-Ray Evaluation with iodoamphetamine for Cerebral Blood Flow Assessment (REICA) method for quantification of cerebral blood flow including acetazolamide challenge test

Objective

The γ-Ray Evaluation with iodoamphetamine for Cerebral Blood Flow Assessment (REICA) is a new method for quantifying cerebral blood flow (CBF) using single-photon emission computed tomography (SPECT) and [¹²³I]N-isopropyl-p-iodoamphetamine (¹²³I-IMP). The present study aimed to validate the REICA method using data including acetazolamide challenge test.

Methods

The REICA and Graph-Plot (GP) methods were used to calculate mean CBF (mCBF) for 92 acquisitions (rest: 57, stress: 35) and cerebrovascular reactivity (CVR) in 33 patients. To obtain stress data, 15 mg/kg of acetazolamide was injected intravenously 10 min before the administration of ¹²³I-IMP, and blood samples were collected under the same conditions as rest data. The reference standard was the Autoradiograph (ARG) method using arterial blood sampling, and the accuracy of the REICA method was analyzed by comparing it with each method.

Results

For mCBF, the correlation coefficients (r) were 0.792 for the REICA method and 0.636 for the GP method. For CVR, r values were 0.660 for the REICA method and 0.578 for the GP method. In both acquisitions, the REICA method had a stronger correlation with the ARG method than the GP method. For mCBF, there was a significant difference in the correlation coefficient between the two correlation coefficients (p < 0.01).

Conclusions

The REICA method was more accurate than the GP method in quantifying CBF and closer to the ARG method. The REICA method, which is a noninvasive method of cerebral blood flow quantification using ¹²³I-IMP, has great medical usefulness.

A new non-invasive graphical method for quantification of cerebral blood flow with[[Formula: see text]] IMP

Objective

[\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{123}\hbox {I}$$\end{document}123I] N-isopropyl-p-iodoamphetamine (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{123}\hbox {I}$$\end{document}123I-IMP) is an ideal perfusion tracer for single photon emission computed tomography, which shows good linearity between cerebral blood flow (CBF) and accumulation. However, quantification of CBF using \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{123}\hbox {I}$$\end{document}123I-IMP without arterial blood sampling has been challenging, with previous methods requiring empirically obtained regression formulae to estimate CBF. Furthermore, the CBF value obtained via some of the previous methods would be affected by the clearance rate of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{123}\hbox {I}$$\end{document}123I-IMP from the lungs. This paper introduces a new non-invasive quantification method for CBF using \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{123}\hbox {I}$$\end{document}123I-IMP and dynamic planar images.

Methods

We have developed a theory based on Microsphere model. This method does not involve regression formulae for estimation and allows for direct measurement of CBF, considering the clearance rate of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{123}\hbox {I}$$\end{document}123I-IMP from the lungs. The study method is executed as easily as conventional Graph-Plot method. We compared the CBF values obtained by our study method and the established autoradiograph (ARG) method.

Results

CBF values obtained using the new method demonstrated significant correlation with values determined using ARG method.

Conclusions

The novel method described presents a reliable and more simple way of determining CBF when compared to current methods.

Asymmetric oculomotor apraxia, optic ataxia, and simultanagnosia with right hemispatial neglect from a predominantly left-sided lesion of the parieto-occipital area

INTRODUCTION

Bálint's syndrome involves bilateral damage to the parieto-occipital area. The extent of the effect of unilateral damage on the Bálint's triad (oculomotor apraxia, optic ataxia, and simultanagnosia) remains unknown.

METHODS

We examined a 63-year-old, right-handed woman who developed right hemianopia, oculomotor apraxia, optic ataxia, simultanagnosia, and hemispatial neglect (HSN) for the right after a cerebral infarction, with detailed neuropsychological tests, magnetic resonance imaging, and single photon emission computed tomography (SPECT).

RESULTS

Neuropsychological examination showed that oculomotor apraxia, optic ataxia, and simultanagnosia were more pronounced in the right hemi-space, probably due to the limited eye movement in the right visual field, whereas HSN was restricted to the right hemi-space. Diffusion-weighted MR images revealed hyperintensity in the left parieto-temporo-occipital region, and several spotty areas of the bilateral frontal and parietal subcortical regions. SPECT revealed hypoperfusion in the left parieto-occipital region and frontal operculum and small areas of the right superior parietal lobule.

CONCLUSIONS

The case suggests that asymmetric (more pronounced in the right hemi-space) oculomotor apraxia, optic ataxia, and simultanagnosia occur in an extensive lesion of the left parieto-occipital cortices. Although HSN is not a prerequisite for simultanagnosia, the coexistence of HSN aggravates simultanagnosia in the hemi-space opposite the lesion.

Prediction of Cognitive Decline from White Matter Hyperintensity and Single-Photon Emission Computed Tomography in Alzheimer's Disease

BACKGROUND

While several studies support an association of white matter hyperintensity (WMH) volume and regional cerebral blood flow (rCBF) with cognitive decline in Alzheimer's disease (AD), no reports have simultaneously considered the effects of both factors on cognitive decline.

OBJECTIVE

The purpose of the present study was to compare WMH volume and rCBF in relation to cognitive function by developing a new software program to fuse magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT) data.

METHOD

We used MRI, SPECT, and neuropsychological data from 182 serial outpatients treated at the memory clinic of our hospital.

RESULTS

Twenty-nine AD patients fulfilled the inclusion criteria (18 females, mean age: 73.1 ± 7.9 years, mean Mini-Mental State Examination: 23.1 ± 3.0). Analysis of variance revealed that posterior deep WMH (DWMH) volume was significantly larger than both anterior periventricular hyperintensity (PVH) and DWMH, and posterior PVH volumes. Multivariate regression analysis showed that increased volumes of the anterior PVH and the posterior DWMH and decreased rCBF of the parietal cortex negatively affected cognitive function. The other areas had no significant negative effects on cognitive function.

CONCLUSION

Our findings show that the volume of the posterior WMH was significantly larger than that of other areas, and the increased posterior WMH volume and decreased rCBF of the parietal cortex negatively affected cognitive function. Therefore, the posterior WMH volume and the parietal rCBF are key parameters of cognitive decline in AD patients.

Influence of Attenuation Correction by Brain Perfusion SPECT/CT Using a Simulated Abnormal Bone Structure: Comparison Between Chang and CT Methods

Brain perfusion SPECT has physical phenomena such as attenuation, scatter, and degradation of resolution that impair accuracy on data acquisition. Chang and CT methods have spread application for attenuation correction (AC) and indicate the utility of AC using a brain phantom without a bone or with a normal bone structure. However, nonuniform AC of an abnormal bone structure such as postoperative bone defect after burr-hole surgery has not yet been evaluated. Therefore, we evaluated the influence of nonuniform AC of an abnormal bone structure between the 2 AC methods. Methods: We created 5 brain phantoms simulating an abnormal bone structure such as frontal, occipital, and right temporal bone defects as well as with and without a bone, which compared the influence among 3-dimensional ordered-subset expectation maximization (OSEM) incorporating scatter, attenuation, and resolution recovery corrections, and obtained 3 reconstruction processing images: OSEM (non-AC; NAC), OSEM (Chang), and OSEM (CTAC). The average counts of the 5 brain phantoms by OSEM (NAC), OSEM (Chang), and OSEM (CTAC) were evaluated by a count profile curve and counts ratio in the region of interest. Results: The counts of OSEM (NAC) and OSEM (Chang) with a bone were approximately 7% higher than those without a bone, whereas OSEM (CTAC) had a similar count ratio. The count ratio of frontal or occipital lobes with a bone defect on both OSEM (NAC) and OSEM (Chang) was 5%-10% higher than that in frontal or occipital lobes without a bone defect; however, OSEM (CTAC) had nearly identical frontal or occipital lobes with and without a bone defect. Conclusion: We conducted a phantom study simulated with and without a bone defect to demonstrate the influence of brain counts between 2 different AC methods. Although the Chang method did not correct the influence of the bone defect due to the use of a uniform attenuation coefficient, the CTAC method correctly conducted AC regardless of the presence of a bone defect.

Evaluation of average amount of cerebral blood flow measured by brain perfusion index in patients with neuropsychiatric systemic lupus erythematosus

We used the brain perfusion index (BPI), an indicator of the average amount of cerebral blood flow (CBF), to evaluate the usefulness of the average amount of CBF for neuropsychiatric systemic lupus erythematosus (NPSLE). Of the seventy three SLE patients examined in this study (total 100 scans), 16 patients (23 scans) had already been diagnosed with NPSLE based on clinical symptoms indicative of central nervous system involvement. In addition, 12 patients (17 scans) exhibited the antiphospholipid antibody syndrome (APS). BPI is significantly influenced by age and we therefore used the BPI ratio (ratio of age predicted BPI to measured BPI value) for each assessment. The mean BPI value of 100 scans was 11.2 + 2.79, and the mean BPI ratio was 0.99 + 0.24 in all SLE patients. The mean BPI ratio among NPSLE (0.84 + 0.19) was significantly lower than that of the non-NPSLE patients (1.04 + 0.24) (P, 0.0005). However, there was no difference in the mean BPI ratio between APS patients (0.98 + 0.24) and non-APS patients (0.99 + 0.25). These results indicate that the mean CBF assessed by the BPI ratio using SPECT is of use in the evaluation of central nervous system involvement in SLE patients.

[Prediction of hyperperfusion after carotid artery stenting based on preoperative estimation of the cerebral blood flow (according to the Kuroda grading system) by single photon emission computed tomography]

This study was conducted to investigate whether preoperative estimation of the cerebral blood flow (CBF) by single photon emission computed tomography (SPECT) can allow identification of patients at risk for hyperperfusion (HP) after carotid artery stenting (CAS). In 40 patients scheduled to undergo CAS, the CBF and cerebral vascular reserve (CVR) were measured prior to the intervention by resting and acetazolamide loading SPECT. The SPECT findings were classified into 4 types: Type 1, normal CBF in the resting state (CBFrest) and normal CVR; Type 2, normal CBFrest and reduced CVR; Type 3, reduced CBFrest and reduced CVR; and Type 4, reduced CBFrest and normal CVR. Four patients presented with HP after CAS. Patients with high proportions of Type 2 and Type 3 had high risk of HP after CAS. (ROC analysis: AUC=0.94, cutoff value of 75.8% had PPV of 75.0%, NPV of 97.2% and odds ratio of 105.0). The proportions of Type 2 and Type 3 in preoperative SPECT may identify patients at risk for the development of HP.

Evaluation of the difference-correction effect of the gamma camera systems used by easy Z-score Imaging System (eZIS) analysis

Objective

We examined the difference of the effect by data to revise a gamma camera difference. The difference-correction method of the camera is incorporated in eZIS analysis.

Methods

We acquired single photon emission computed tomography (SPECT) data from the three-dimensional (3D) Hoffman brain phantom (Hoffman), the three-dimensional brain phantom (3D-Brain), Pool phantom (pool) and from normal subjects (Normal-SPECT) to investigate compensating for a difference in gamma camera systems. We compared SPECT counts of standard camera with the SPECT counts that revised the difference of the gamma camera system (camera). Furthermore, we compared the “Z-score map (Z-score)”. To verify the effect of the compensation, we examined digitally simulated data designed to represent a patient with Alzheimer’s dementia. We carried out both eZIS analysis and “Specific Volume of interest Analysis (SVA)”.

Results

There was no great difference between the correction effect using Hoffman phantom data and that using 3D-Brain phantom data. Furthermore, a good compensation effect was obtained only over a limited area. The compensation based on the pool was found to be less satisfactory than any of the other compensations according to all results of the measurements examined in the study. The compensation based on the Normal-SPECT data resulted in a Z-score map (Z-score) for the result that approximated that from the standard camera. Therefore, we concluded that the effect of the compensation based on Normal-SPECT data was the best of the four methods tested.

Conclusions

Based on eZIS analysis, the compensation using the pool data was inferior to the compensations using the other methods tested. Based on the results of the SAV analysis, the effect of the compensation using the Hoffman data was better than the effect of the compensation using the 3D-Brain data. By all end-point measures, the compensation based on the Normal-SPECT data was more accurate than the compensation based on any of the other three phantoms.

Utility of early post-treatment single-photon emission computed tomography imaging to predict outcome in stroke patients treated with intravenous tissue plasminogen activator

It is important to predict the outcome of tissue plasminogen activator (tPA)-treated patients early after the treatment for considering the post-tPA treatment option. We assessed cerebral blood flow (CBF) of tPA-treated patients with single-photon emission computed tomography (SPECT) 1 hour after tPA infusion to predict the patient outcome. Technetium-99m-hexamethylpropyleneamine oxime SPECT was performed in 35 consecutive tPA-treated patients. Asymmetry index, a contralateral-to-ipsilateral ratio of CBF, was calculated to analyze CBF quantitatively. Hypoperfusion or hyperperfusion was defined as a decrease of 25% or more or a increase of 25% or more in asymmetry index, respectively. Of all 35 patients, 23 had only hypoperfusion, 8 had both hypoperfusion and hyperperfusion, 2 had only hyperperfusion, and 2 had no perfusion abnormality. When evaluating the association between hypoperfusion and outcome, hypoperfusion volumes were significantly correlated with the modified Rankin Scale at 3 months (r = .634, P < .001). Hyperperfusion was observed in 10 patients (28.6%) and they showed a marked National Institutes of Health Stroke Scale score improvement in the first 24-hour period, which were significantly greater than those of 25 patients without hyperperfusion (P = .033). Eight patients (22.9%) with intracerebral hemorrhage (ICH) were all asymptomatic. Most ICHs were located in hypoperfusion areas, and no ICH was related to hyperperfusion. The results of the present study demonstrated that hypoperfusion volume was associated with poor outcome, whereas the presence of hyperperfusion seemed to be predictive of symptom improvement but not of development of ICH. Taken together, early post-treatment SPECT imaging seems to be a useful biomarker of outcome in tPA-treated patients.

[Evaluation of shortened protocol of graph plot method with ¹²³I-IMP]

The (123)I-IMP Graph Plot is a convenient method of analyzing cerebral blood flow without blood sampling. Data acquisition requires 45 minutes after the infusion of (123)I-IMP because the method is matched to the protocol of autoradiography (conventional method). However, we think that those protocols do not have to be matched because those theories are different. Therefore, we contrived a protocol for shortening that time by beginning SPECT data acquisition earlier and shortening the acquisition time compared to the conventional method. We compared count ratios of the decreased area to an area of the healthy side, quantitative values, and results of statistical analysis of the shortened protocol and the conventional method for cases of cerebral infarction and of dementia with Lewy bodies (DLB). Some count ratios of the shortened protocol were inferior to those of the conventional method, but the degrees did not affect the clinical diagnosis. In the other areas and cases also, the differences did not affect the clinical diagnosis. In addition to the results of this study, some previous reports have described that early SPECT images after infusion show the true cerebral blood flow. Therefore, we judged that this shortened protocol can be used as a clinical protocol.

Regional cerebral blood flow in healthy volunteers measured by the graph plot method with iodoamphetamine SPECT

PURPOSE

The graph plot method, a technique that uses N-isopropyl-(123)I-p-iodoamphetamine (IMP) and single photon emission computed tomography (SPECT) for non-invasive measurement of regional cerebral blood flow (CBF), has been developed and applied in the clinical setting, although it has been performed without obtaining normal CBF values in normal, healthy subjects. The aim of this study was to measure normal regional CBF in older healthy subjects with IMP SPECT and the graph plot method.

SUBJECTS AND METHODS

Eleven healthy volunteers (mean age: 63.5 ± 8.9 years; six males and five females) were recruited and regional CBF was measured using IMP SPECT and the graph plot method.

RESULTS

The averaged global CBF was 45.4 ml/100 g/min. The distribution of regional CBF was almost homogenous in the cortices. There was no significant correlation between the global CBF and age in subjects aged 50-80 years.

CONCLUSION

We used the IMP graph plot method to measure regional CBF in normal healthy subjects, without arterial blood sampling, and obtained compatible CBF values. This method is non-invasive and convenient for determination of regional CBF in the clinical setting.

Usefulness of the automatic quantitative estimation tool for cerebral blood flow: clinical assessment of the application software tool AQCEL

OBJECTIVE

AQCEL enables automatic reconstruction of single-photon emission computed tomogram (SPECT) without image degradation and quantitative analysis of cerebral blood flow (CBF) after the input of simple parameters. We ascertained the usefulness and quality of images obtained by the application software AQCEL in clinical practice.

METHODS

Twelve patients underwent brain perfusion SPECT using technetium-99m ethyl cysteinate dimer at rest and after acetazolamide (ACZ) loading. Images reconstructed using AQCEL were compared with those reconstructed using conventional filtered back projection (FBP) method for qualitative estimation. Two experienced nuclear medicine physicians interpreted the image quality using the following visual scores: 0, same; 1, slightly superior; 2, superior. For quantitative estimation, the mean CBF values of the normal hemisphere of the 12 patients using ACZ calculated by the AQCEL method were compared with those calculated by the conventional method. The CBF values of the 24 regions of the 3-dimensional stereotaxic region of interest template (3DSRT) calculated by the AQCEL method at rest and after ACZ loading were compared to those calculated by the conventional method.

RESULTS

No significant qualitative difference was observed between the AQCEL and conventional FBP methods in the rest study. The average score by the AQCEL method was 0.25 ± 0.45 and that by the conventional method was 0.17 ± 0.39 (P = 0.34). There was a significant qualitative difference between the AQCEL and conventional methods in the ACZ loading study. The average score for AQCEL was 0.83 ± 0.58 and that for the conventional method was 0.08 ± 0.29 (P = 0.003). During quantitative estimation using ACZ, the mean CBF values of 12 patients calculated by the AQCEL method were 3-8% higher than those calculated by the conventional method. The square of the correlation coefficient between these methods was 0.995. While comparing the 24 3DSRT regions of 12 patients, the squares of the correlation coefficient between AQCEL and conventional methods were 0.973 and 0.986 for the normal and affected sides at rest, respectively, and 0.977 and 0.984 for the normal and affected sides after ACZ loading, respectively.

CONCLUSIONS

The quality of images reconstructed using the application software AQCEL were superior to that obtained using conventional method after ACZ loading, and high correlations were shown in quantity at rest and after ACZ loading. This software can be applied to clinical practice and is a useful tool for improvement of reproducibility and throughput.

A prospective study of cerebral blood flow and cerebrovascular reactivity to acetazolamide in 162 patients with idiopathic normal-pressure hydrocephalus

OBJECT

Cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) to acetazolamide were investigated prospectively in 162 patients with a proposed diagnosis of idiopathic normal-pressure hydrocephalus (NPH). The aim of this study was to assess the usefulness of the measurement of CBF and CVR in determining which patients would be likely to benefit from shunt placement.

METHODS

The mean CBF of the whole brain was measured according to the Patlak plot method by using technetium-99m hexamethylpropyleneamine oxime. The CVR value was obtained from the response to administration of 500 mg acetazolamide and calculated as the percentage change from the baseline mean CBF value.

RESULTS

One hundred forty-six patients (90.1%) responded to shunt placement ("responders"), but 16 patients (9.9%) did not ("nonresponders"). No significant difference in preoperative CBF was observed between responders and nonresponders. Preoperative CVR was significantly impaired (p<0.0025) in responders compared with healthy controls, but not in nonresponders. Responders with the incomplete triad had a significant reduction (p<0.001) in preoperative CVR, but not in preoperative CBF, compared with healthy controls. Responders with the complete triad had significantly lower preoperative CBF and CVR than those with the incomplete triad (p<0.01 and p<0.05, respectively). Postoperative CBF and CVR increased significantly (p<0.025 and p<0.001, respectively) in responders.

CONCLUSIONS

Both CBF and CVR decrease with the development of NPH, suggesting that hemodynamic ischemia may be responsible for manifestation of the symptoms. Impaired CVR and reduced CBF with the development of symptoms can be proposed as diagnostic criteria for idiopathic NPH.

Effects of cilostazol on cerebral blood flow, P300, and serum lipid levels in the chronic stage of cerebral infarction

The effects of cilostazol (Pletaal, Otsuka Pharmaceutical Co., Tokyo, Japan) on cerebral blood flow, P300 event-related potentials, and serum lipid levels were examined in patients in the chronic stage of cerebral infarction. This study included 20 patients (13 men and 7 women, mean age 67 +/- 11 years) with cerebral infarction who had taken ticlopidine (100 mg orally, twice a day). Quantitative cerebral blood flow measurements by Patlak plot analysis, ultrasound examinations of the common carotid arteries, and measurements of P300 event-related potentials and serum lipid levels were performed. Ticlopidine was then replaced with cilostazol (100 mg orally, twice a day) while other medications remained unchanged. The same examinations were performed again 3 months later. After replacement of ticlopidine with cilostazol, cerebral blood flow significantly increased in the frontal white matter, temporal cortex, and occipital cortex compared with cerebral blood flow before replacement with cilostazol. Ultrasonograms of the common carotid arteries showed no significant differences in intima-media thickness before and after replacement. However, peak systolic velocity, time-averaged peak velocity, and volume flow all significantly increased after replacement. Blood flow in the frontal white matter showed a significant negative correlation with P300 latency before and after replacement of ticlopidine with cilostazol. And P300 latency improved significantly after replacement with cilostazol. Regarding lipid levels, total cholesterol, triglycerides, and remnant-like particles-cholesterol all decreased significantly after replacement with cilostazol. Cilostazol, an inhibitor of platelet aggregation, was thus concluded to be effective in improving cerebral blood flow, cerebral function, and serum lipid levels in patients in the chronic stage of cerebral infarction.

Usefulness of fully automated constant ROI analysis software for the brain: 3DSRT and FineSRT

The positioning or selection of a region of interest (ROI) is an essential step for the quantification of brain images. However, so long as the ROIs were manually selected, results obtained fluctuated considerably with subtle changes in their positioning. To perform an ROI analysis of the brain with improved objectivity and excellent reproducibility, we recently established fully automated ROI-based analysis software for the brain, the so-called 3DSRT and the FineSRT. 3DSRT performed by consecutive analyzing process as follows: (1) anatomical standardization using the SPM99 algorithm; (2) analysis using constant 318 ROIs divided into 12 groups (segments) on each hemisphere; (3) calculation of the area-weighted average for each of the respective 24 segments; (4) display of the results followed by the saving of respective values of the 636 ROIs (both hemispheres). The processes of the FineSRT were fundamentally similar to that of 3DSRT, but on FineSRT more precise constant 1394 ROIs (both hemispheres) corresponding to the respective cerebral convolutions were used. Our programs have been useful for objective estimation of cerebrovascular reserve, especially for follow-up studies of an infant with moyamoya disease, because we could compare the results without consideration of the patient's growth during the follow-up period.

Contributing factors to changes of cerebral blood flow in major depressive disorder

BACKGROUND

Results of single photon emission computed tomography (SPECT) regarding mood disorders have been inconsistent. The aim of the study was to elucidate factors contributing to changes in cerebral blood flow in patients with major depressive disorder.

METHODS

A total of 89 consecutive patients diagnosed with major depressive disorder using DSM-IV semistructured interviews were evaluated using single photon emission computed tomography, the 17-item Hamilton Rating Scale for Depression (HRSD), and the Global Assessment of Function (GAF) scale. Nineteen of these patients also underwent the same tests during remission.

RESULTS

Global cerebral blood flow (gCBF) was significantly higher during remission than at the time of enrollment. Significant correlations were seen between gCBF and age, duration of previous episode of depression, and hypochondriasis. However, no correlation was seen between gCBF and HRSD, GAF, severity and duration of depressive episode, or melancholia-type depression. Correlations between gCBF and age were seen only at enrollment and disappeared during remission. No differences in regional cerebral blood flow at any site were seen between time of enrollment and remission for the same patient.

LIMITATION

Analysis that adequately accounts for these factors to changes of cerebral blood flow in major depressive disorder will require a large subject population.

CONCLUSIONS

These results suggest that although there is a decrease in gCBF in major depressive disorder, the level of the decrease is determined by conditions present before episode onset, rather than by the characteristics of the episode itself. The findings also suggest that the correlation between gCBF and age is state-dependent.

Effect of Perindopril on Cerebral and Renal Perfusion on Normotensives in Mild Early Ischaemic Stroke: A Randomized Controlled Trial

BACKGROUND AND PURPOSE

Blood pressure reduction is central to secondary prevention after stroke, but the optimal time to start therapy is unknown. Cerebral autoregulation is impaired early after ischaemic insult, and any changes in systemic blood pressure may be reflected in cerebral perfusion. However, early initiation in hospital may better assure continued long-term treatment. We have investigated the effect of the angiotensin-converting enzyme inhibitor perindopril on blood pressure, global and focal cerebral blood flow (CBF) and glomerular filtration rate (GFR) in a normotensive acute stroke population.

METHODS

Twenty-five patients within 4-8 days of mild ischaemic stroke/transient ischaemic attack and with diastolic blood pressure 70-90 mm Hg were randomized to receive perindopril 2 or 4 mg daily versus placebo according to estimated GFR. Mean arterial blood pressure (MABP), internal carotid artery (ICA) flow and middle cerebral artery velocity (MCAv) were measured prior to dosing, over the following 24 h and at 2 weeks. Brain hexamethyl propylene amino oxide single photon emission computed tomography (SPECT) was performed before dosing and at estimated time of peak drug effect (6-8 h after first dose). GFR measurement using a (51)Cr-ethylene diamine tetraacetic acid technique was undertaken prior to medication and repeated at 2 weeks.

RESULTS

MABP was reduced throughout the first 24 h with a mean MABP reduction of 9.3 mm Hg (95% CI 7.4-11.3 mm Hg), maximal placebo corrected fall of 12.5 mm Hg at 10 h post-dose, p = 0.005. No significant change occurred in ICA flow, MCAv or CBF measured by SPECT: change from baseline in symptomatic hemisphere CBF was -0.02 (SD 3.11) ml/100 g/min (treated group) compared with 0 (SD 3.01) (placebo group). Similarly, no significant change was observed in cortical CBF. Mean within-group change in GFR was 2.7 +/- 10.1 in the treated group and -4.3 +/- 6.7 in the placebo group (p = NS).

DISCUSSION

Antihypertensive therapy with perindopril may be introduced in the first week after mild ischaemic stroke in normotensive patients without affecting global or regional CBF or affecting GFR.

Psychomotor retardation correlates with frontal hypoperfusion and the Modified Stroop Test in patients under 60-years-old with major depression

Frontal hypoperfusion and frontal dysfunction have been reported in patients with major depression. It was also found that frontal hypoperfusion correlated with frontal dysfunction evaluated by neuropsychological tests in depressive patients aged 60 or over. These findings suggested that depression may cause frontal dysfunction and frontal hypoperfusion, and that these pathophysiological changes are manifested as psychomotor retardation. We performed single photon emission computed tomography and Modified Stroop Test on 35 patients with depression aged 25-83 to investigate association of depressive symptoms and psychological tests with cerebral blood perfusion. Additionally, we divided the patients into a younger (less than 60 years old) and an older (60 or over) group to examine the effect of age. Significant correlations were found between frontal perfusion, interference measure on Modified Stroop Test, and psychomotor retardation in all patients. These correlations were also found in the younger group. There was no significant difference on frontal perfusion, interference measure of the Modified Stroop Test, and psychomotor retardation between the two groups. The present findings suggest that frontal hypoperfusion, frontal dysfunction, and psychomotor retardation were associated with one another in not only the old but also the young patients with depression.

Spectral analysis of 99mTc-HMPAO for estimating cerebral blood flow: a comparison with H2(15)O PET

Cerebral blood flow (CBF) can be quantified non-invasively using the brain perfusion index (BPI), which is determined using radionuclide angiographic data obtained through the use of technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO). The BPI is generally calculated using graphical analysis (GA). In this study, BPI was measured using spectral analysis (SA), and the usefulness of SA was compared with that of GA. Thirteen patients with various brain diseases and four healthy male volunteers were examined using radionuclide angiography with 99mTc-HMPAO. The BPI was measured for each subject using both SA and GA. In the four healthy volunteers, the BPI was examined at rest and after the intravenous administration of 1 g of acetazolamide (ACZ). An H2(15)O PET examination was also performed in the 13 patients; the BPIS and BPIG values were compared with the CBF measurements obtained using H2(15)O PET (CBFPET). The BPI values obtained by SA (BPIS) (x) and by GA (BPIG) (y) were correlated (y = 0.568x + 0.055, r = 0.901) in the 13 patients and four healthy volunteers at rest, although the BPIG values were underestimated by 36.1 +/- 7.5% (mean +/- SD) compared with the BPIS values. The degree of underestimation tended to increase with increasing BPIS values. The increase in the BPIS was 32.1 +/- 8.0% after the intravenous administration of ACZ, while the increase in BPIG was only 8.1 +/- 2.8%. This discrepancy was considered to be the result of the BPIG values being affected by the first-pass extraction fraction of the tracer. Although both BPIS and BPIG values were significantly correlated with the CBFPET values, the correlation coefficient for BPIS was higher than that for BPIG (BPIS: r = 0.881; BPIG: r = 0.832). These results suggest that SA produces a more reliable BPI for quantifying CBF using 99mTc-HMPAO than the conventional method using GA. The SA method should be especially useful for activation studies involving pharmacological intervention and/or clinical cases with an increased CBF.

The effect of losartan on global and focal cerebral perfusion and on renal function in hypertensives in mild early ischaemic stroke

BACKGROUND

Secondary prevention of stroke with antihypertensive drugs is now standard practice, but it is unclear how soon after a cerebrovascular event antihypertensive therapy should be initiated or re-started. Due to impaired cerebral autoregulation, changes in systemic blood pressure may be reflected in cerebral perfusion, especially in hypertensive patients immediately post-stroke. Conversely, early initiation in hospital may better assure continued long-term treatment. We have investigated the effect of the angiotensin II receptor antagonist (ARA) losartan on mean arterial blood pressure (MABP), global and focal cerebral blood flow (CBF), and glomerular filtration rate (GFR) in hypertensive patients 2-7 days after stroke.

METHODS

Twenty-four patients without occlusive carotid disease but with MABP between 110 and 145 mmHg were studied within 2-7 days of ischaemic stroke/transient ischaemic attack (TIA). They were randomized to receive either placebo or losartan (25 or 50 mg daily). MABP and internal carotid artery (ICA) flow were measured at baseline, over the following 24 h and at 2 weeks. Brain hexamethylpropyleneamine oxime single photon emission computed tomography (HMPAO SPECT) was performed before dosing and at the estimated time of peak drug effect (6-8 h after the first dose). GFR was measured at baseline and at 2 weeks.

RESULTS

The mean National Institutes of Health (NIH) score of randomized patients was 2.6; losartan was generally well tolerated and no patient suffered a deterioration in neurological function. A mean placebo-corrected intra-subject reduction in MABP of 9.5 mmHg was observed in treated patients from 1-12 h (P = 0.0001), with a maximal fall of 18.1 mmHg at 9 h post-dose (P = 0.002). No change occurred in ICA flow, or cortical or hemispheric CBF measured by HMPAO SPECT. No significant change in GFR was seen within or between groups.

DISCUSSION

Losartan may be introduced within 2-7 days of mild stroke in hypertensive patients in whom significant carotid occlusive disease has been excluded without affecting global or regional CBF, or affecting GFR.

Role of brain perfusion single-photon emission tomography in traumatic head injury

This investigation examined the role of brain perfusion single-photon emission tomography (SPET) in traumatic head injury in 35 patients. The results were compared with those of X-ray computerized tomography (CT) and magnetic resonance imaging (MRI). CT and MRI detected brain contusions in seven patients, subarachnoid haemorrhage in one patient and both in nine patients. In 16 of the 17 subjects (94%), SPET with technetium-99m-hexamethylpropyleneamine oxime (Tc-HMPAO) revealed CT/MRI-negative abnormalities, such as hypoperfusion in the contre-coup region, frontal hypoperfusion related to personality change and cerebellar hypoperfusion associated with vertigo. In two patients presenting with diffuse axonal injury in the brainstem, hypoperfusion in the frontal cortex on the affected side was observed on SPET. SPET demonstrated hypoperfusion in the adjacent cortex, with no abnormality on either CT or MRI, in six of seven patients exhibiting acute epidural haematoma. SPET failed to provide additional information in two of five patients with acute subdural haematoma and in one of two patients displaying chronic subdural haematoma. In four of nine patients with post-traumatic amnesia, SPET detected hypoperfusion in the temporal lobe, with no abnormality on either CT or MRI. In five of eight patients with vertigo, SPET detected hypoperfusion in the morphologically normal cerebellum. In seven cases involving personality change, frontal hypoperfusion was observed in four; moreover, a markedly non-homogeneous pattern was evident in the remaining three. Overall, SPET afforded additional information in 26 patients (74%). CT possesses an advantage with respect to the detection of haemorrhagic lesions. MRI provides more precise information regarding contusions and axonal injury. Frequently, SPET may be the only examination to reveal perfusion abnormalities which are related to symptoms in the absence of other objective findings, such as post-traumatic amnesia, vertigo or personality change.

The relationship between cerebral blood flow and cognitive function in patients with brain insult of various etiology

The relationship between the mean cerebral blood flow (CBF) and cognitive function was investigated in patients with brain insult. This study included 72 patients aged 24-85 years treated for the following diseases: cerebral infarction (21), intracerebral hemorrhage (4), subarachnoid hemorrhage (2), brain tumor (14), cerebral contusion (12), normal pressure hydrocephalus (13), Alzheimer's disease (2), and others (4). First-pass radionuclide angiography using Technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) was performed for the measurement of the mean CBF, and the Sturb-Black Mental Status Examination for the neuropsychological evaluation. The mean CBF and the score of the neuropsychological test were significantly reduced compared with those of the age-matched controls. Regardless of etiology, the mean CBF and the score of neuropsychological test were significantly reduced, and a significant correlation was observed except for the patients with cerebral contusion. The quantitative measurement of CBF using 99mTc-HMPAO is reliable to estimate the neuropsychological state.

Cerebral blood flow SPET in transient global amnesia with automated ROI analysis by 3DSRT

The aim of this study was to determine the areas involved in episodes of transient global amnesia (TGA) by calculation of cerebral blood flow (CBF) using 3DSRT, fully automated ROI analysis software which we recently developed. Technetium-99m L, L-ethyl cysteinate dimer single-photon emission tomography ((99m)Tc-ECD SPET) was performed during and after TGA attacks on eight patients (four men and four women; mean study interval, 34 days). The SPET images were anatomically standardized using SPM99 followed by quantification of 318 constant ROIs, grouped into 12 segments (callosomarginal, precentral, central, parietal, angular, temporal, posterior cerebral, pericallosal, lenticular nucleus, thalamus, hippocampus and cerebellum), in each hemisphere to calculate segmental CBF (sCBF) as the area-weighted mean value for each of the respective 12 segments based on the regional CBF in each ROI. Correlation of the intra- and post-episodic sCBF of each of the 12 segments of the eight patients was estimated by scatter-plot graphical analysis and Pearson's correlation test with Fisher's Z-transformation. For the control, (99m)Tc-ECD SPET was performed on eight subjects (three men and five women) and repeated within 1 month; the correlation between the first and second sCBF values of each of the 12 segments was evaluated in the same way as for patients with TGA. Excellent reproducibility between the two sCBF values was found in all 12 segments of the control subjects. However, a significant correlation between intra- and post-episodic sCBF was not shown in the thalamus or angular segments of TGA patients. The present study was preliminary, but at least suggested that thalamus and angular regions are closely involved in the symptoms of TGA.

Interobserver variability of cerebral blood flow measurements obtained using spectral analysis and technetium-99m labeled compounds

Radionuclide angiography with technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) or technetium-99m ethyl cysteinate dimer (99mTc-ECD) enables the non-invasive estimation of absolute cerebral blood flow (CBF) to be determined by using spectral analysis (SA). We previously demonstrated the clinical use of SA; however, this method involves a few manual steps. The aim of this study was to evaluate the interobserver variability of CBF estimations made using SA and compare these results with those obtained by using graphical analysis (GA). In twenty patients with various brain diseases (27-74 years old), radionuclide angiography examinations were performed using 99mTc-labeled compounds (10 patients, 99mTc-HMPAO; 10 patients, 99mTc-ECD). Bilateral cerebral hemispheres were studied in all patients, and the brain perfusion index (BPI) values were estimated using SA and GA. The interobserver variability between two observers was then assessed. A good correlation between the BPI values assessed using both SA (BPI(S)) and GA (BPI(G)) was obtained. The correlation coefficient for BPI(S) (r = 0.987) was almost the same as that for BPI(G) (r = 0.982). The degree of interobserver variability was not affected by the measurement of elevated BPI values. Measurements carried out by two observers using both SA and GA exhibited a similar degree of interobserver variability. SA appears to have a satisfactory interobserver variability and may be more suitable for clinical applications.

Graphical analysis of 99mTc thyroid scintigraphy

A new non-invasive simple method for quantitative evaluation of thyroid was presented using graphical analysis of the transfer process of technetium-99m pertechnetate (99mTc) from the blood to thyroid. Thirty subjects were studied. After a bolus injection of 111 MBq of 99mTc, the data were recorded on a 128 x 128 matrix as 60 frames of 1.5-second duration. ROIs were placed over the aortic arch and bilateral thyroid lobes. The activity of the aorta was monitored instead of the arterial activity. Graphical analysis by plotting B(t)/A(t) versus integral(0)t A(tau)d tau/A(t) gave a straight line within the first 30 seconds in all subjects. The slope of the line was the unidirectional influx rate of 99mTc (k(u)). Thyroid perfusion index (TPI) was calculated to standardize where the ratio of ROI(thyroid) size to ROI(aorta) size was set as 10. K(u) and TPI showed good correlation with 99mTc thyroid uptake. Hyperthyroid patients showed high values of k(u) and TPI. Considering that these indices were determined at the first pass of 99mTc, this method may be helpful especially in the evaluation of thyroid perfusion.

Assessment of acetazolamide reactivity in cerebral blood flow using spectral analysis and technetium-99m hexamethylpropylene amine oxime

Cerebral blood flow (CBF) can be quantified noninvasively using the brain perfusion index (BPI), determined from radionuclide angiographic data generated with technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO). Previously, the BPI has been calculated using graphical analysis (GA); however, the GA method is greatly affected by the first-pass extraction fraction and retention fraction, which are not only variable, but lower in cases with an increased CBF, such as after the administration of acetazolamide. Thus, GA-calculated BPI values (BPIG) may not reflect the absolute CBF. The objective of this study was to use the spectral analysis of radionuclide angiographic data collected using 99mTc-HMPAO to examine changes in the BPI after the administration of acetazolamide. We studied the CBF of both cerebral hemispheres in six healthy male volunteers; the BPI was measured at rest and after the intravenous administration of 1 g of acetazolamide. In all participants, an H215O positron emission tomography (PET) examination was also performed, and the spectral analysis-calculated BPI values (BPIS) and BPIG values were compared with the actual CBF measured using H215O PET (mCBFPET). The BPIS was 1.070 +/- 0.051 (mean +/- SD) at rest and 1.497 +/- 0.098 after acetazolamide; the corresponding BPIG values were 0.646 +/- 0.073 and 0.721 +/- 0.107. The BPIS values were significantly correlated with the mCBFPET values, whereas the BPIG values were not. According to the BPIS values, the increase in BPI after the intravenous administration of acetazolamide was 40.1 +/- 8.4%, as opposed to an increase of only 11.3 +/- 6.5% according to the BPIG values. These results suggest that the spectral analysis of 99mTc-HMPAO-generated data yields a more reliable BPI than GA for the quantification of CBF after acetazolamide administration.

Measurement of cerebral blood flow using graph plot analysis and I-123 iodoamphetamine

PURPOSE

N-isopropyl-p[I-123]iodoamphetamin (IMP) is transiently taken up by the lungs after intravenous injection and its concentration in arterial blood varies depending on the degree of I-123 IMP uptake and subsequent washout. A method that does not require arterial blood sampling would be valuable to measure cerebral blood flow (CBF) using I-123 IMP.

METHODS

The authors developed a new theory and a convenient new method of CBF determination using I-123 IMP that does not require blood sampling. Dynamic images of the head and chest were acquired immediately after intravenous injection of I-123 IMP in a series of 42 consecutive patients with cerebrovascular disorders or other brain diseases (31 men, 11 women; mean age, 58 +/- 11 years). Changes in the I-123 IMP counts of the regions of interest set in the head and pulmonary trunk were analyzed by the graph plot method, and the F values (CBF index slope) determined were compared with the mean CBF levels obtained by simultaneous autoradiography.

RESULT

The F values correlated well with the mean CBF obtained by autoradiography (r = 0.818, P < 0.001).

CONCLUSIONS

This innovative I-123 IMP graph plot analysis method using the time-activity curve of the head and pulmonary trunk alone is a noninvasive, convenient way to measure CBF. It is expected to become the most useful clinical technique for measuring CBF with I-123 IMP. This method can be used for patient follow-up and for comparing different patient groups evaluated in regional CBF studies.

A case of general paresis showing marked treatment-associated improvement of cerebellar blood flow by quantitative imaging analysis

We describe a patient with general paresis who developed progressive dementia and a cerebellar syndrome including wide-based gait, slurred speech, and intention tremor. Quantitative analysis by means of a Patlak plot of single-photon emission computed tomography (SPECT) with 99mTc-ethyl cysteinate dimer showed generally low blood flow in the cerebrum and the cerebellum. After antisyphilitic therapy, blood flow in the brain, especially in the cerebellum, improved noticeably, as did the cognitive disorder and the cerebellar syndrome.

Non-invasive quantitative monitoring of cerebral blood flow in aneurysmal subarachnoid haemorrhage with 99mTc-ECD

The purpose of this prospective study was to detect symptomatic cerebral vasospasm in aneurysmal subarachnoid haemorrhage (SAH) by a non-invasive mean cerebral blood flow (mCBF) quantification using 99mTc-ethyl cysteinate dimer. Measurement of mCBF without blood sampling and single photon emission tomography (SPECT) were performed at 1 and 7 days after surgery in 35 consecutive SAH patients, of whom 16 were examined at day 30 as well. A decrease in mCBF of more than 10% on day 7 versus day 1 was considered to indicate vasospasm. On visual interpretation of SPECT, a perfusion decrease which appeared newly on day 7 was considered to indicate vasospasm. In total, nine of 35 patients had cerebral vasospasm confirmed by computed tomography (CT) and/or angiography. The mCBF measurement showed a 77.8% (7/9) sensitivity, a 88.5% (23/26) specificity, a 70.0% (7/10) positive predictive value, and a 92.0% (23/25) negative predictive value. SPECT yielded a 33.3% (3/9) sensitivity, a 73.1% (19/26) specificity, a 30.0% (3/10) positive predictive value, and a 76.0% (19/25) negative predictive value. On SPECT, decreased perfusion was observed in most of the patients at clipping sites, which might represent post-operative transient abnormal perfusion and should not be read as vasospasm. In conclusion, this mCBF measurement is more accurate than visual interpretation of SPECT for detecting vasospasm.

Cerebrovascular reactivity to acetazolamide in alert patients with cerebral infarction: usefulness of first-pass radionuclide angiography using 99m Tc-HMPAO in monitoring cerebral haemodynamics

Cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) were studied in 75 patients with cerebral infarction. All patients were alert with the symptoms of hemiparesis and/or aphasia, and were divided into two groups: 42 patients had occlusion or stenosis of >75% at the internal carotid artery or main trunk of middle cerebral artery; and 33 patients did not. Hemispheric mean CBF was measured by performing first-pass radionuclide angiography using 99mTc-hexamethylpropylene amine oxime. CVR was measured as the percentage change from the baseline mean CBF value after the administration of 500 mg acetazolamide. The CVR in both groups was significantly impaired (5.2+/-6.3%, P<0.001 and 7.7+/-6.1%, P<0.01, respectively) compared with normal controls (14.7+/-3.3%), although the mean CBF was not significantly reduced compared with age-matched controls. In the 12 patients with unilateral carotid occlusion, five patients with good collateral flow via the anterior communicating artery showed preserved CVR (11.0+/-7.8%), but those without did not (1.6+/-7.0%). CVR is impaired in alert patients with cerebral infarction, although the mean CBF is not reduced, and good collateral flow via the anterior communicating artery in patients with carotid occlusion may be a sign of well-preserved haemodynamic status.

Quantitative evaluation of cerebral metabolites and cerebral blood flow in patients with carotid stenosis

We examined the metabolic and hemodynamic status of patients with severe carotid stenosis and evaluated the effectiveness of carotid endarterectomy (CEA) by comparing pre- and post-operative results of quantitative proton magnetic resonance spectroscopy (1H-MRS) and single-photon emission computed tomography (SPECT). Quantitative 1H-MRS and SPECT were performed in 17 patients with severe carotid stenosis before CEA; in 10 patients the examinations were repeated after CEA. There was a significant correlation between the degree of internal carotid artery (ICA) stenosis and the N-acetyl-aspartate (NAA) concentration, and between CBFand NAA in the basal ganglia. In 10 of the 17 patients (58.8%) we noted a decrease of NAA on 1H-MRS. After CEA in these patients, NAA was significantly increased, and in 7 of 8 patients whose pre-operative SPECT had indicated impairment of cerebral vasoreactivity, it was improved. Quantitative 1H-MRS and CBF measurements can indicate the severity of metabolic and hemodynamic impairment in patients with severe carotid stenosis, and can help to assess the effectiveness of CEA.

Quantitative measurement of cerebral blood flow by (99m)Tc-HMPAO SPECT in acute ischaemic stroke: usefulness in determining therapeutic options

OBJECTIVE

Early recanalisation by thrombolysis is a conclusive therapy for acute ischaemic stroke. But this therapy may increase the risk of intracerebral haemorrhage or severe brain oedema. The purpose was to evaluate usefulness of quantitative measurement of cerebral blood flow by single photon emission computed tomography (SPECT) in predicting the risk of haemorrhage or oedema, and determining the therapeutic options in acute hemispheric ischaemic stroke.

METHODS

The relation was studied retrospectively between initial regional cerebral blood flow (rCBF) quantitatively measured by technetium-99m-labelled hexamethylpropyleneamine oxime ((99m)Tc-HMPAO) SPECT and final clinical and radiological outcome in 20 patients who presented hemispheric ischaemic stroke and were treated conservatively or received early recanalisation by local intra-arterial thrombolysis. The non-invasive Patlak plot method was used for quantitative measurement of rCBF by SPECT.

RESULTS

Regions where residual rCBF was preserved over 35 ml/100 g/min had a low possibility of infarction without recanalisation and regions where residual rCBF was preserved over 25 ml/100 g/min could be recovered by early recanalisation. However, regions where residual rCBF was severely decreased (< 20 ml/100 g/min) had a risk of intracerebral haemorrhage and severe oedema.

CONCLUSIONS

A quantitative assessment of residual rCBF by (99m)Tc-HMPAO SPECT is useful in predicting the risk of haemorrhage or severe oedema in acute ischaemic stroke. Therapeutic options should be determined based on the results of rCBF measurement.

Improving the measurement of the 99Tc(m)-ECD brain perfusion index by temporal analysis

Matsuda et al. have described a non-invasive method for brain perfusion quantification by computing the ratio of the cumulated counts in the cerebral hemispheres and aortic arch. The regions of interest (ROIs) are drawn manually and are observer dependent. The aim of this study was to develop a new method designed to minimize the intra- and interobserver variability when drawing the different ROIs. A dynamic study was performed as in Matsuda's method on 30 patients using technetium-99m ethyl cysteinate dimer (99Tc(m)-ECD) (ID: 800 MBq+/-33 MBq). The manual method of drawing ROIs was then compared with the following, automated one. A temporal analysis was performed on the cardiac first-pass study to obtain parametric images of the thorax. An ROI of the aortic arch was drawn automatically by means of an isocontour algorithm on the resulting views. The whole sequence was reframed and filtered by a temporal low-pass filter. Hemispheric brain ROIs were delineated on a summed image. Matsuda's algorithm was then applied. Intraobserver variability was evaluated for the classical Matsuda method. The correlation in brain perfusion index (BPI) measurements was r = 0.8976 for naive observers and r = 0.9443 for well-trained observers. Interobserver variability was also evaluated; the correlation was r = 0.7574 for naive observers and r = 0.9190 for well-trained observers. With our proposed method, the correlation in the measurements of BPI for evaluating the intraobserver variability was r = 0.9955 for naive observers and r = 0.9989 for well-trained observers. For interobserver variability, the results were r = 0.9234 for naive observers and r = 0.9230 for well-trained observers. We conclude that temporal analysis allows brain perfusion to be measured in a semi-automatic manner, and improves the reproducibility compared with the original method of Matsuda, particularly for naive observers.

Multiple myeloma showing increased accumulation of Tc-99m hexamethylpropylene amine oxime on brain SPECT

The authors report a case of multiple myeloma with increased accumulation of Tc-99m hexamethylpropylene amine oxime (HMPAO) on brain SPECT. Tc-99m HMPAO is a lipophilic compound that freely passes through the intact blood-brain barrier and cell membrane and is rapidly converted to a hydrophilic form by glutathione and then retained in the neuron for several hours. In general, Tc-99m HMPAO shows decreased accumulation in brain tumors. However, some reports of increased accumulation in brain tumors, such as meningioma, glioblastoma multiforme, high-grade astrocytoma, pituitary adenoma, and multiple myeloma, have been published. The Tc-99m HMPAO uptake in these tumors has been attributed to tumor blood flow or glutathione contents within the tumor. With regard to uptake to Tc-99m HMPAO in multiple myeloma, the tumor size is considered to be an additional factor.

Regional cerebral blood flow in male schizophrenic patients performing an auditory discrimination task

Regional cerebral blood flow (rCBF) was measured in 11 schizophrenic patients amid 10 normal controls, both at rest and while performing an auditory discrimination task. Single photon emission computed tomography with technetium-99m hexamethylpropylene amine oxime was used for quantitative evaluation of rCBF. The schizophrenic patients showed greater rCBF in the temporal and parietal regions at rest than the controls, but no abnormalities were found in frontal perfusion. During task performance. on the other hand, the patients showed a reduced frontal rCBF. whereas there was no group difference in rCBF in the temporal and parietal regions. In addition, the left> right hemisphere asymmetries of rCBF observed in the controls during task performance were not present in the patients. although there was no group difference in hemisphere laterality in rCBF at rest. These findings suggest that the employment of a cognitive task for neuroimaging studies is useful for detecting abnormalities of brain activation. such as hypofrontality and altered hemisphere laterality. in patients with schizophrenia.

Usefulness of cerebral blood flow (CBF) measurements to predict the functional outcome for rehabilitation in patients with cerebrovascular disease (CVD)

PURPOSE

The objectives of this study were to (1) elucidate the relationship between the mean CBF in the whole brain (Av.mCBF) before rehabilitation of CVD patients and the BI score before and after rehabilitation, (2) determine whether the efficacy of rehabilitation can be predicted by measurement of the Av.mCBF, and (3) investigate what part of the brain was most important to improving the BI score.

MATERIALS AND METHODS

The Av.mCBFs in 160 patients with CVD were calculated by Patlak plots with 99mTc-HMPAO before rehabilitation, and we determined the BI score before and after rehabilitation. Based on the BI scores before and after rehabilitation, patients were divided into four groups: Group A, BI = 100; Group B, 80 < or = BI < or = 99; Group C, 60 < or = BI < or = 79; Group D, 0 < or = BI < or = 59. We evaluated the relationship between the Av.mCBF and BI score before and after rehabilitation.

RESULTS

The Av.mCBF before rehabilitation showed a tendency to be more correlated with the BI score after rehabilitation (r = 0.414, p < 0.0001) than before rehabilitation (r = 0.272, p = 0.0006). After rehabilitation, there was a tendency for the Av.mCBF value to increase in direct proportion to the BI score of the group: it was highest in Group A and lowest in Group D. The strongest correlation was found between the frontal lobe regional CBF before rehabilitation and the BI score after rehabilitation (r = 0.343, p < 0.0001).

CONCLUSIONS

Measurement of the Av.mCBF before rehabilitation of CVD patients will permit prediction of the efficacy of rehabilitation. Also the regional CBF of the frontal lobe is most important for improving the BI score.

Impairment of cerebrovascular reactivity to acetazolamide in patients with normal pressure hydrocephalus

Cerebrovascular reactivity (CVR) to acetazolamide was investigated in 41 patients with normal pressure hydrocephalus (NPH). The aetiology was subarachnoid haemorrhage in 20 patients, trauma in nine, brain tumour in three and idiopathic in nine. Mean cerebral blood flow (CBF) of the whole brain was measured by performing first-pass radionuclide angiography using 99Tcm-hexamethylpropylene++ amine oxime. Cerebrovascular reactivity was measured as the percentage change from the baseline mean CBF value after the administration of 500 mg of acetazolamide. Cerebrovascular reactivity was significantly (P < 0.001) reduced in patients with the complete triad of NPH (1.4 +/- 3.1%), regardless of the aetiology, compared with normal controls (14.7 +/- 3.3%). Patients with the incomplete triad also showed significantly (P < 0.05) reduced CVR (9.6 +/- 5.4%). Patients with the complete triad had significantly (P < 0.001) lower CVR than those with the incomplete triad. Post-operative CVR in both groups (20 patients with the complete triad and 9 patients with the incomplete triad) increased significantly, from 1.5 +/- 3.5% to 10.0 +/- 5.5% (P < 0.001) and from 8.7 +/- 4.9% to 14.9 +/- 5.4% (P < 0.05), respectively. Cerebrovascular reactivity is impaired in patients with NPH regardless of the aetiology and improves after shunting.

Neuronal impairment of adult moyamoya disease detected by quantified proton MRS and comparison with cerebral perfusion by SPECT with tc-99m HM-PAO: a trial of clinical quantification of metabolites

We evaluated neuronal impairment of adult moyamoya patients by proton magnetic resonance spectroscopy (MRS) and cerebral perfusion scintigraphy. After evaluating two methods for compensating relaxation times, we selected a long TR, short TE sequence to achieve better reproducibility. The cerebral blood flow (CBF) value was measured by scintigraphy following the method of quantification reported in the previous literature. N-acetyl aspartate (NAA) concentrations and CBFs value were decreased statistically (P < 0. 05) compared with those of the age-matched normal controls. However, the decreased rate of NAA concentration was changed more than the CBF value, and no linear correlation was found between the two values. We considered that the NAA concentration was not always correlated with that of the present cerebral perfusion. The NAA concentration showed a more dispersive distribution in patients than in controls, indicating a large individual variation in neuronal impairment. We concluded that proton MRS may provide useful information about neuronal impairment in individual patients. J. Magn. Reson Imaging 1999;10:124-129.

Prediction of cerebral infarct sizes by cerebral blood flow SPECT performed in the early acute stage

Cerebral infarct due to embolic stroke without recanalization was examined by cerebral blood flow (CBF) SPECT in the early acute stage, and the possibility of predicting the size it will reach in the later stages was evaluated. Twenty patients (67 +/- 13 years) were examined by CBF SPECT with 99mTc-ECD 4.5 +/- 3.1 hours after the onset of cardiogenic cerebral embolism. The ratio of the anteroposterior length of the cerebral hemisphere to that of the severe ischemic region, which was defined as an area of clear-cut severe reduction in CBF as observed by SPECT, was calculated. One week after the onset, the cerebral infarct was measured in the same manner by CT, and the relationship between the two measurements was evaluated. The CBF in the region of severe ischemia and the surrounding region was determined by the Patlak plot method, and the affected/non-affected (A/NA) ratio was calculated. In severe ischemic regions the CBF ranged from 1.7 ml/100 g/min to 20 ml/100 g/min (mean, 11 +/- 5 ml/100 g/min), whereas the A/NA ratio ranged from 4% to 45% (mean, 26 +/- 11%). On the other hand, the CBF in the surrounding regions ranged from 20 ml/100 g/min to 52 ml/100 g/min (mean, 34 +/- 8 ml/100 g/min) whereas the A/NA ratio ranged from 52% to 104% (mean, 77 +/- 11%). The coefficient of correlation between the infarct size predicted by SPECT and that measured by CT was r = 0.986, and the correlation equation was Y = 1.047X - 2.969. CBF SPECT performed in the early acute stage can be used to predict the size of cerebral infarct.