Comparison of Xe-CT/CBF and quantitative ECD-SPELT

We compared stable xenon enhanced X-ray computed tomography (Xe-CT) with Technetium-99m ethylsteinate dimer single-photon emission computed tomography (ECD-SPECT) in 12 patients. We evaluated the cerebral blood flow (CBF) values in the territory of the anterior, middle and posterior cerebral artery, and in the thalamus. The CBF values were higher in ECD-SPECT than in Xe-CT except for the values of the thalamus. The posterior cerebral artery territory showed a lower correlation and the thalamus had no correlation between two methods. We discussed causes of these differences.     

Regional cerebral blood flow values measured by Xe-CT during the attack of transient global amnesia: a case report]

A 50-year-old right-handed woman was referred to our hospital for further examination of sudden global amnesia. The patient had no history of epilepsy, head injury or cerebral vascular diseases. There were no neurological deficits except for recent memory disturbance. We examined her cerebral blood flow(CBF) immediately during transient global amnesia(TGA) by stable xenon enhanced CT scans(Xe-CT) and twice thereafter. Xe-CT during the attack showed a significant diminution of regional blood flow from the right posterior temporal lobe to the occipital lobe. Conventional MRI scans also had been performed serially but it could not detect the local ischemic event. The ischemic lesion was clearly divided and larger than those cases reported using PET, SPECT, and diffusion-weighted MRI. TGA happens suddenly, and recovery is immediate. It becomes very difficult to study CBF during TGA attack. However stable Xe-CT is capable of examining CBF easily, so we concluded that CBF examination by Xe-CT in TGA patients would be helpful to reveal the mechanism of TGA.     

Xe-CT对moyamoya病患者脑血流评价作用的初步研究(附2例报告)

目的 探讨Xe-CT在moyamoya病诊治中的应用价值.方法 对2例moymoya患者行Xe-CT检查,测定其脑血流情况,并制定相应治疗方案.结果 1例患者Xe-CT示双侧额叶、双侧枕叶及右侧顶叶缺血明显,给予针对性改善脑血流量的治疗,患者病情有所缓解;另外1例患者Xe-CT示没有明显缺血,暂时不给予治疗,观察病情变化.结论 Xe-CT可以提供moyamoya病患者脑血流图像,并可以定量检测区域脑血流量,为临床诊断和治疗提供重要的参考依据.     

Cerebral embolism: local CBF and edema measured by CT scanning and Xes inhalation

Serial CT scans were made in baboons after cerebral embolization during stable Xe inhalation for measuring local values for CBF and lambda (brain-blood partition or solubility coefficients), followed by iodine infusion for detecting blood-brain barrier (BBB) damage. Supplementary 133Xe CBF measurements were made at corresponding intervals. Persistent zones of zero flow surrounded by reduced flow were measured predominantly in subcortical regions, which showed gross and microscopic evidence of infarction at necropsy. Overlying cortex was relatively spared. Reduced lambda values attributed to edema appeared within 3--5 minutes and progressed up to 60 minutes. Damage to BBB with visible transvascular seepage of iodine began to appear 1--1 1/2 hours after embolism. In chronic animals, lambda values were persistently reduced in areas showing histologic infarction. Contralateral hemispheric CBF increased for the first 15 minutes after embolism, followed by progressive reduction after 30 minutes (diaschisis).     

注意缺陷多动障碍患儿的SPECT研究

目的 探讨注意缺陷多动障碍(ADHD)儿童脑血流改变与临床症状及智力的关系。方法用非采血法SPECT显像法测定65例ADHD及20例正常组全脑血流(CBF)、左右脑血流量及局部脑血流量,并分析其与临床症状及智力水平的相关性。结果 ①40％ADHD存在rCBF降低,降低区域分布频率为额叶>丘脑,尾状核>颞叶>枕叶、顶叶。②ADHD患儿临床症状越严重,CBF血流量降低越明显,两者呈正相关(r=0.4618,P<0.05)。③CBF血流量降低越显著,ADHD患儿智力水平越低下(r=0.5614,P<0.05)。结论 注意缺陷多动障碍患儿脑血流改变与临床症状及智力水平有一定相关性。     

Regional cerebral blood flow of the basal ganglia and thalamus measured using Xe-CT]

Cerebral blood flow (CBF) images obtained using Xe-CT have a much higher spatial resolution than SPECT or PET images. The regional CBF (rCBF) of deep brain regions, the basal ganglia and thalamus, was able to be measured using Xe-CT in 6 subjects. Average rCBF was 87.1 +/- 20.7 ml/100 g/min in the caudate nucleus, 83.5 +/- 15.8 ml/100 g/min in the putamen, 50.0 +/- 8.7 ml/100 g/min in the globus pallidus and 88.9 +/- 12.4 ml/100 g/min in the thalamus. The average rCBF value of the globus pallidus was lower than the values of the caudate nucleus, putamen and thalamus. These observations may be explained by reduced cellularity of the globus pallidus in comparison to the other regions. SPECT and PET are not able to clearly demonstrate the globus pallidus on CBF images. However, precise rCBF values can be measured in the globus pallidus using Xe-CT.     

The effect of sodium bicarbonate on CBF and intracellular pH in man: Stable Xe-CT and 31P-MRS

The effects of sodium bicarbonate on cerebral blood flow (CBF) and intracellular pH were studied in five normal volunteers. CBF and intracellular pH were measured by stable xenon computed tomography and phosphorus-31 magnetic resonance spectroscopy (³¹P-MRS) respectively. Each patient received 7% sodium bicarbonate (3.5 ml/kg body weight) infused intravenously for 15 minutes. Before and after this injection, CBF, intracellular pH and physiological parameters were measured. CBF and PaCO₂ were significantly increased. On the other hand, hematocrit and intracellular pH were decreased. These result suggests that three factors are thought to contribute to increase CBF during administration of sodium bicarbonate in humans: 1) arterial dilatation in response to carbon dioxide 2) an decrease of hematocrit 3) intracellular acidosis.     

Differential responses in CBF and CBV to cocaine as measured by fMRI: Implications for pharmacological MRI signals derived oxygen metabolism assessment

Introduction

Cognitive performance-induced brain oxygen metabolism has been successfully measured by functional magnetic resonance imaging (fMRI) in human studies. The measurement of the cerebral metabolic rate of oxygen consumption (CMRO₂) is typically achieved by assuming a fixed coupling of cerebral blood flow (CBF) and cerebral blood volume (CBV) and by performing a separate experiment to assess the vascular response to a hypercapnic challenge. Psychoactive drugs may have directly effect on the cerebral vasculature, potentially confounding the interpretation of pharmacological MRI (phMRI) data. In this study, we tested the assumptions of the standard CMRO₂ calculation following the administration of cocaine, in order to test the validity of this measurement in phMRI studies. The initial transient state and later steady state CBF and CBV responses to a hypercapnic challenge were measured.

Methods

CBF and CBV responses were directly measured by fMRI using continuous arterial spin-labeling (ASL) and contrast-enhanced fMRI, respectively. The coupling between changes in CBF and CBV during a hypercapnic challenge was examined under normal conditions and following the administration of cocaine.

Results

A decoupling of changes in CBF and CBV was observed during the transient state immediately following the administration of cocaine, and an altered coupling of CBF and CBV was found during the steady state after cocaine injection.

Discussion

These data suggest caution in interpreting CMRO₂ measurements from phMRI studies and may also lead to an improved understanding of the complex neuronal and vascular mechanisms of drug action.     

Estimation of baroreflex sensitivity using transfer function analysis: normal values and theoretical considerations

Human baroreflex sensitivity is traditionally derived from changes in heart rate due to alterations of the baroreceptor input (pharmacologically or physically induced blood pressure changes). Transfer function analysis (TFA) of changes in heart rate (output function) and physiological blood pressure oscillations (input function) at approximately 0.1 Hz (Mayer waves) has already been accepted as a measure of baroreflex sensitivity (BRS). Transfer function analysis provides gain and phase shift values for each frequency band and body position. We performed TFA in 50 normal subjects in the supine and tilted positions, at mid-frequency (0.05–0.15 Hz) and high-frequency (0.15–0.33 Hz) bands, recording heart rate and blood pressure continuously with a Finapres device. Gain values were in accordance with previous studies. Phase shifts lay within a narrow range for all frequency bands and positions. High correlations were found between phase shifts of the same frequency band, but not for those of the same position. This supports the idea that the transfer mechanisms for the two frequency bands may, in part, be different. There was a poor correlation between gain and phase values on the one hand and, on the other hand, further spectral measures and the results of standard autonomic tests. This suggests that TFA may not only be a measure of BRS, but also a complementary tool for evaluation of autonomic function.     

The lithiumeter: a measured approach

Malhi GS, Tanious M, Gershon S. The lithiumeter: a measured approach.
Bipolar Disord 2011: 13: 219–226. © 2011 The Authors.
Journal compilation © 2011 John Wiley & Sons A/S. Background: Lithium has long been recognised for its mood‐stabilizing effects in the management of bipolar disorder (BD) but in practice its use has been limited because of real and ‘imagined’ concerns. This article addresses the need for lithium to be measured with respect to its clinical and functional effects. It introduces a visual scale, termed lithiumeter, which captures the optimal lithium plasma levels for the treatment of BD. Methods: Key words pertaining to lithium’s administration, dosing, and side effects as well as its efficacy in acute and long‐term treatment of BD were used to conduct an electronic search of the literature. Relevant articles were identified by the authors and reviewed. Results: This paper outlines the considerations necessary prior to initiating lithium therapy and provides a guide to monitoring lithium plasma levels. Current recommendations for optimal plasma lithium levels in the management of BD are then discussed with respect to indications for use in the acute phases of the illness and maintenance therapy. The risks associated with lithium treatment are also discussed. Conclusions: The lithiumeter provides a practical guide of optimal lithium levels for the clinical management of BD.     

Somatosensory cortical potentials evoked by stimulation of leg nerves: analysis of normal values and variability; diagnostic significance

An attempt was undertaken to assess the diagnostic value of sensory potentials evoked by stimulation of leg nerves. Findings in normal persons were as follows. First, stimulation of the sural nerve was superior to other methods, especially stimulation of the tibial nerve. Second, variations in latency were considerable and not attributable to age, height, or skin temperature. In many normal persons latency was not stable in either short-time or long-time trials. Amplitudes varied to such an extent that they could not help in diagnosis with the possible exception of extreme side-to-side differences. Finally, both amplitudes and latencies varied in relation to stimulus intensity, repetition rate, and filtering. Since sensory potentials from the leg nerves varied considerably, normal values must extend over a range that is wide enough to avoid mistaken diagnosis of abnormality. Hence, slight disturbances of nerve conduction such as those found in certain neuropathies, root damage and many extramedullary intraspinal space-occupying lesions could not be identified, whereas extensive demyelination in all parts of the sensory neuronal chain was readily discovered.     

Comparative study of regional cerebral blood flow values measured by Xe CT and Xe SPECT

The regional cerebral blood flow (rBCF) values measured by stable xenon-enhanced computed tomography (Xe XT) and by radioactive xenon-133 single photon emission computed tomography (Xe SPECT) were compared in 16 patients with cerebral infarct. On the non-lesion side Xe SPECT recorded 10.7% higher rCBF values than Xe CT in the anterior cerebral artery territory while Xe CT recorded 9.6% higher values than Xe SPECT in the middle cerebral artery territory. These differences were not statistically significant. Although the rCBF values were almost the same no correlation was found between the two methods in the posterior cerebral artery territory and the basal ganglia. Only hemispheric CBF on the non-lesion side showed the same value and a good correlation between the Xe CT and the Xe SPECT. There was a good correlation in the hemispheric CBF values on the lesion side, too. The difference of rCBF between the non-lesion side and the lesion side was expressed smaller in the Xe SPECT than in the Xe CT. This is in agreement with the previous reports that Xe SPECT overestimates the flow in the low flow areas. The higher rCBF values in the anterior cerebral artery territory measured by the Xe SPECT was ascribed to the artifact from the radioactivities in the inhalation mask and the air passages as reported previously. In conclusion, there is no good correlation between the rCBF values measured by the Xe CT and by the Xe SPECT. Only hemispheric CBF shows a good correlation between the two methods.     

Personality profiles among normal aged individuals as measured by the NEO-PI-R

The revised Neuroticism (N), Extraversion (E), Openness (O) to experience Personality Inventory (NEO-PI-R) is a multidimensional measure of normal personality traits that is intended to assess five major personality dimensions or domains-N, E, O, Agreeableness (A), and Conscientiousness (C). Although several studies have been conducted examining N, E, and O factors in people 65 through to 85 years old, there has been little research examining all five-core domains of personality in individuals 85 and older. We compared the NEO-PI-R domains and facet traits in the middle-aged/young-old versus old-old normal subjects. Thirty-eight community-dwelling subjects (22 women, 16 men) free from major neuropsychiatric disorders were given the NEO-PI-R, a self-administered 240-item personality inventory, assessing 30 facet traits within the five domains. We compared the scores of 21 middle-aged and young-old (age 50-84) individuals, to those of 17 old-old (age 85-100) subjects. The personality profiles of the two groups were similar except that the old-old group had lower scores on Extraversion, and four of the 30 facet traits (warmth, positive emotions, impulsiveness, and order) compared to the middle-aged/young-old group. These results were limited by the cross-sectional design and small sample size. Nonetheless, the findings suggest that the middle-aged/young-old and the old-old normal subjects have fairly similar personality traits.     

Power spectral analysis of heart rate variability: normal values of subjects over 60 years old

Power spectral analysis of heart rate variability (HRV) provides a non-invasive method of estimating cardiac autonomic nerve activity. It has been reported that HRV decreases with age. The purpose of this study was to assess the values of and determine the reliability of HRV in healthy older people. The study found lower and highly variable values of HRV. It was concluded that the reliability of HRV in older subjects might need to be reinvestigated and only normalized values of HF and LF might be useful. Larger study groups and different recording periods of HRV are needed.