Regional brain cerebral glucose metabolism and temperament: a positron emission tomography study

Personality, and in particular temperament, is thought to have a biological basis. In the present study, the relationships between regional brain glucose metabolism and temperament have been investigated. Regional brain glucose metabolism was measured using [18F] fluorodeoxyglucose positron emission tomography in 31 healthy subjects. Temperament was assessed using the Temperament and Character Inventory. Temperament dimensions were observed to be significantly correlated with specific brain regions. In particular, novelty seeking was significantly correlated with the superior temporal gyrus, inferior parietal lobule, and the precuneus, which have been reported to be related with impulsiveness, while reward dependence was significantly correlated with the caudate head, which has been shown to be associated with reward processing. The various aspects of temperament may have biological bases in the specific brain regions. The accumulation of results from studies of this kind should provide further evidence connecting personality traits with their biological bases.     

Generalized Gibbs priors based positron emission tomography reconstruction

Bayesian methods have been widely applied to the ill-posed problem of image reconstruction. Typically the prior information of the objective image is needed to produce reasonable reconstructions. In this paper, we propose a novel generalized Gibbs prior (GG-Prior), which exploits the basic affinity structure information in an image. The motivation for using the GG-Prior is that it has been shown to be effective noise suppression, while also maintaining sharp edges without oscillations. This feature makes it particularly attractive for the reconstruction of positron emission tomography (PET) where the aim is to identify the shape of objects from the background by sharp edges. We show that the standard paraboloidal surrogate coordinate ascent (PSCA) algorithm can be modified to incorporate the GG-Prior using a local linearized scheme in each iteration process. The proposed GG-Prior MAP reconstruction algorithm based on PSCA has been tested on simulated, real phantom data. Comparison studies with conventional filtered backprojection (FBP) method and Huber prior clearly demonstrate that the proposed GG-Prior performs better in lowering the noise, preserving the image edge and in higher signal noise ratio (SNR) condition.     

Image reconstruction for positron emission tomography using fuzzy nonlinear anisotropic diffusion penalty

Iterative algorithms such as maximum likelihood-expectation maximization (ML-EM) become the standard for the reconstruction in emission computed tomography. However, such algorithms are sensitive to noise artifacts so that the reconstruction begins to degrade when the number of iterations reaches a certain value. In this paper, we have investigated a new iterative algorithm for penalized-likelihood image reconstruction that uses the fuzzy nonlinear anisotropic diffusion (AD) as a penalty function. The proposed algorithm does not suffer from the same problem as that of ML-EM algorithm, and it converges to a low noisy solution even if the iteration number is high. The fuzzy reasoning instead of a nonnegative monotonically decreasing function was used to calculate the diffusion coefficients which control the whole diffusion. Thus, the diffusion strength is controlled by fuzzy rules expressed in a linguistic form. The proposed method makes use of the advantages of fuzzy set theory in dealing with uncertain problems and nonlinear AD techniques in removing the noise as well as preserving the edges. Quantitative analysis shows that the proposed reconstruction algorithm is suitable to produce better reconstructed images when compared with ML-EM, ordered subsets EM (OS-EM), Gaussian-MAP, MRP, TV-EM reconstructed images.     

Regional cerebral oxidative and total glucose consumption during rest and activation studied with positron emission tomography

The relationship between regional oxidative and total rCMR in five healthy volunteers in activated and non-activated areas of the brain has been investigated with positron emission tomography (PET). The tracers [l-^uC]-D-glucose and [2-¹⁸F]2-fluoro-2-deoxy-D-glucose were used. A previous study has shown that the former may be used to measure the rate of glucose oxidation while the latter tracer is used to measure the total rate of glucose consumption. Regional activation was performed (voluntary finger movements). Use of a computerized brain atlas enabled comparison between the regional oxidative and total rCMR_glc in each volume element of the brain for the group of subjects. The values of total and oxidative rCMR_gle, when calculated for each volume element of the brain and displayed in a scatter plot, were found to be symmetrically grouped around a straight line which passes close to the origin. The slope of this line varied between the subjects. This indicates that, on the average, the fraction of non-oxidative glucose utilization is constant within each subject, regardless of the value of rCMR_gle and, further, that the fraction of non-oxidative glucose utilization varies between subjects. The total and oxidative CMR_glc in the activated left hand area were 23.4 + 0.9% (mean + SEM) and 11.7 + 0.3%, respectively, higher than in the contralateral homologous non-activated area. Our interpretation of the difference is that regional activation increases the fraction of non-oxidative glucose consumption. This interpretation is supported by a previous PET study using [¹⁵0]O_a, and by studies using MRS technique.     

Hyperbaric oxygen treatment attenuated the decrease in regional glucose metabolism of rats subjected to focal cerebral ischemia: a high resolution positron emission tomography study

Cerebral hypoxia may be the main component of cell damage caused by ischemia. Previous studies demonstrated a neuroprotective effect of early hyperbaric oxygen (HBO) treatment in various animal models of focal cerebral ischemia. Neuropathologic study showed that exposure of HBO may prevent cell death in ischemic cortex. In the present study, we aimed to assess cellular function of ischemic rat brain after HBO treatment by means of a high-resolution positron emission tomography scanner (microPET) used specifically for small animal imaging. The male Sprague-Dawley rats were subjected to permanent middle cerebral artery occlusion (MCAO), with the regional cerebral blood flow monitored in vivo by laser Doppler flowmetry. One hour after ischemia, HBO therapy (3 atm absolute, 1 h) was initiated. Local cerebral glucose utilization in the ischemic area was measured before, 1 h and 3 h after ischemia, with 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG) as a tracer. Neurological deficits and infarct volumes were assessed at 24 h after ischemia. Our study showed that early HBO therapy significantly reduced infarct volume of brain 24 h after ischemia. Moreover, glucose utilization in the ischemic area underwent a severe decrease during 1-3 h after MCAO, while the early HBO treatment significantly attenuated the decrease in cerebral metabolic rate of glucose in the ischemic core of the cortex compared with controls. We report for the first time the application of microPET to quantify the rates of glucose metabolism in the ischemic core of rats exposed to HBO. Our results suggest that the early exposure of HBO can partially reverse the downward trend for glucose utilization in the ischemic core, which might contribute to the reported beneficial effects of early HBO therapy on permanent cerebral ischemia.     

Within-arm somatotopy in human motor areas determined by positron emission tomography imaging of cerebral blood flow

Within-arm somatotopy was identified in multiple motor areas of six normal human subjects who performed a visuomotor tracking task during positron emission tomography (PET) measurement of relative cerebral blood flow (relCBF). A randomly moving target, presented on a computer monitor, was continuously followed with the index finger (movement at the metacarpopha-langeal joint), thumb, fist (movement at the wrist), forearm (movement at the elbow), elbow (movement at the shoulder), and eyes alone (control task) during sequential imaging. Segmental limb movements were associated with relCBF responses in the contralateral motor, supplementary motor, cingulate, and parietal cortex, and in the ipsilateral cerebellum. Localization of responses after stereotaxic transformation into Talairach atlas space, as well as within-subject analysis without anatomic deformations, demonstrated an overlapping somatotopic distribution in the motor cortex, with thumb responses most ventrolateral and shoulder responses most dorsomedial. Proximal limb movements induced relCBF responses of greater magnitude than distal movements. Somatotopy was also identified in the supplementary motor area, with index finger responses dorsal and anterior to shoulder responses. An additional set of somatotopic responses were located in the cingulate cortex, also with finger responses anterior to shoulder responses. Somatotopy was not identified in the anterior cerebellum. The distribution of relCBF responses is concordant with electrophysiologic studies in nonhuman primates that demonstrate a fractured somatotopy on a fine scale and a general somatotopic scheme of the limb on a large scale in multiple discrete motor areas.     

Functional brain imaging of episodic and semantic memory with positron emission tomography

 Human memory is composed of several independent but interacting systems. These include a system for remembering general knowledge, semantic memory, and a system for recollection of personal events, episodic memory. The results of positron emission tomography (PET) studies of regional cerebral blood flow indicate that networks of distributed brain regions subserve episodic and semantic memory. Some networks seem to be generally engaged in memory processes whereas the involvement of others is specific to factors such as the type of information to be remembered or the level of retrieval success. The PET findings help to understand memory dysfunction (a) by showing that multiple brain regions are involved in different memory processes and (b) by sharpening the interpretation of the functional role of different brain regions. Received: 31 January 1997 / Accepted: 28 May 1997     

Feasibility study of the use of similarity maps in the evaluation of oncological dynamic positron emission tomography images

A preliminary study is presented on the potential role of similarity mapping (SM) in the evaluation of oncological dynamic¹⁸F-fluorodeoxyglucose positron emission tomography studies, mainly in lesion localisation and detectability. Similarity maps were calculated using previously described (correlation coefficient (COR) and normalised correlation coefficient (NCOR) and newly introduced similarity measures (sum of squares coefficient (SSQ), squared sum coefficient (SQS), sum of cubes coefficient (SC) and cubed sum coefficient (CS)). The results were evaluated using simulated and clinical data. The study revealed that the best-suited similarity measure for such applications was the CS similarity coefficient, which provided the best parametric images, delineating structures of interest and supporting the visual interpretation of data sets. It was shown that SM and standardised uptake value (SUV) images had comparable diagnostic performance, although SM was able to offer additional time-related information in a single image. For the case of colorectal recurrences (17 cases), the measured contrast values for the CS and SUV images were 2.36±0.47 and 4.12±0.42, respectively, whereas, for three cases of giant cell tumours, these values were 11.6±2.1 and 11.9±1.8, respectively.     

利用Micro-PET显像技术分析阿尔茨海默病小鼠模型的脑糖代谢

目的 利用小动物PET（Micro-PET）影像技术18氟-脱氧葡萄糖（¹⁸F-FDG）摄取率分析阿尔茨海默病(AD)小鼠模型的脑糖代谢,探索评价治疗AD药物的影像分析技术。 方法 正常对照组、APP^swe/PSΔE9转基因模型组和安理申［2 mg/(kg•d)］治疗组小鼠共9只,自腹腔注射放射性示踪剂¹⁸F-FDG,采集脑部Micro-PET图像,通过软件IRW计算并比较各组小鼠大脑与额叶、颞叶感兴趣区（ROI）每克组织¹⁸F-FDG的摄取率。 结果 利用¹⁸F-FDG 的Micro-PET影像分析可以检测AD小鼠模型的脑糖代谢,并发现APP^swe/PSΔE9转基因小鼠的脑糖摄取明显降低,与人类AD患者表现的脑糖摄取降低一致,安理申治疗可以提升APP^swe/PSΔE9转基因小鼠的脑糖摄取。 结论 ¹⁸F-FDG Micro-PET影像分析可以用于小鼠AD模型脑葡萄糖代谢水平的检测,并可以作为阿尔茨海默病治疗药物提升脑糖代谢作用的分析技术。     

Desmoplastic fibroma of the scapula with fluorodeoxyglucose uptake on positron emission tomography: a case report and literature review

We present a case of desmoplastic fibroma (DF) arising from the right scapula that was incidentally identified by fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging performed to evaluate the presence of metastasis due to a history of surgical treatment for endometrioid adenocarcinoma. A 65-year-old woman was admitted to our hospital for consultation about a bone lesion in the right scapula although she was asymptomatic. FDG-PET revealed moderate focal ¹⁸F-FDG uptake in the right scapula with a maximal standardized uptake value of 3.2. The lower angle of the scapula was unclear on plain radiology. Needle biopsy was performed to make a differential diagnosis between primary bone and metastatic tumor. Pathologically, the tumor was composed of a relatively sparse proliferation of spindle-shaped fibroblastic/myofibroblastic cells in a dense collagenous background. Therefore, the diagnosis was a primary fibrous bone tumor. Wide excision was performed, because of the possibility of malignant tumors such as low-grade fibrosarcoma in light of the FDG-PET uptake. Pathologically, the resected tumor was composed of a proliferation of less atypical spindle cells in the collagenous stroma with focally myxoid change; no mitotic figures were observed. Immunohistochemically, β-catenin nuclear/cytoplasmic staining was not observed, and no β-catenin genetic mutations were detected. Therefore, the tumor was diagnosed as DF. DF is a tumor that exhibits FDG-PET uptake. There were no signs of recurrence 6 months after surgery.     

Amyloid and metabolic positron emission tomography imaging of cognitively normal adults with Alzheimer's parents

This study examines the relationship between fibrillar beta-amyloid (Aβ) deposition and reduced glucose metabolism, a proxy for neuronal dysfunction, in cognitively normal (NL) individuals with a parent affected by late-onset Alzheimer's disease (AD). Forty-seven 40–80-year-old NL received positron emission tomography (PET) with ¹¹C-Pittsburgh compound B (PiB) and 18F-fluoro-2-deoxy-d-glucose (FDG). These included 19 NL with a maternal history (MH), 12 NL with a paternal history (PH), and 16 NL with negative family history of AD (NH). Automated regions of interest, statistical parametric mapping, voxel-wise intermodality correlations, and logistic regressions were used to examine cerebral-to-cerebellar PiB and FDG standardized uptake value ratios across groups. The MH group showed higher PiB retention and lower metabolism in AD regions compared with NH and PH, which were negatively correlated in posterior cingulate, frontal, and parieto-temporal regions (Pearson r ≤ −0.57, p ≤ 0.05). No correlations were observed in NH and PH. The combination of Aβ deposition and metabolism yielded accuracy ≥ 69% for MH vs. NH and ≥ 71% for MH vs. PH, with relative risk = 1.9–5.1 (p values < 0.005). NL individuals with AD-affected mothers show co-occurring Aβ increases and hypometabolism in AD-vulnerable regions, suggesting an increased risk for AD.     

Comparison of regional brain metabolism in bulimia nervosa and affective disorder assessed with positron emission tomography

Women with bulimia often present with symptoms of depression in addition to bingeing and purging behavior. Brain metabolism in eight women with bulimia nervosa was compared to that in eight women with major affective disorder and eight normal women, using positron emission tomography and 18-fluoro-2-deoxyglucose. Normal women have higher right than left cortical metabolic rates and active basal ganglia. Bulimics lost the normal right activation in some areas, but maintained basal ganglia activity. Depressives retained right hemisphere activation, but had decreased metabolism in basal ganglia. This suggests that although women with bulimia frequently present with symptoms of depression, the pathophysiologic changes associated with bulimia differ from major effective disorder.     

Rapid measurement of regional cerebral blood flow in the baboon using15O-labelled water and dynamic positron emission tomography

The sensitivity and reproducibility of rapid measurements of regional cerebral flow (rCBF) using a bolus injection of H₂ ¹⁵O and dynamic positron emission tomography (PET) were investigated in anaesthetised baboons. The cerebrovascular reactivity to changes in arterial pCO₂ was used as an experimental support. PET data were acquired over 4 min following a single bolus intravenous injection of H₂ ¹⁵O, while arterial blood was withdrawn for continuous activity counting. Images were reconstructed with a dynamic sequence of 45×2s+15×10s, including a correction for decay. Regional values of CBF were derived from non-linear least-squares fits of the time activity curves using a four-parameter two-compartment model. The results obtained with a four-parameter fitting method were compared with those obtained with two other rapid estimation methods, first fitting two parameters only, CBF and partition coefficient (p), and secondly autoradiography (with p fixed at 0·95 ml brain ml blood⁻¹). Twelve regions of interest were analysed. The values for the basal CBF obtained from 13 measurements in two baboons were close to published values obtained with other techniques. Reproducibility checks showed a mean variation of 9·7 per cent. The CBF measurements performed in hypercapnic conditions gave results similar to published data in other animal species, showing a 4·5±0·9 per cent increase in CBF per mm Hg p_aCO₂. The results obtained with the three estimation techniques were closely correlated. The dynamic bolus H₂ ¹⁵O method appeared to be suitable for high blood flow measurements.     

Relations between PET-derived measures of thalamic glucose metabolism and EEG alpha power

Electroencephalogram (EEG) alpha power has been demonstrated to be inversely related to mental activity and has subsequently been used as an indirect measure of brain activation. The thalamus has been proposed as an important site for modulation of rhythmic alpha activity. Studies in animals have suggested that cortical alpha rhythms are correlated with alpha rhythms in the thalamus. However, little empirical evidence exists for this relation in humans. In the current study, resting EEG and a fluorodeoxyglucose positron emission tomography scan were measured during the same experimental session. Over a 30-min period, average EEG alpha power across 28 electrodes from 27 participants was robustly inversely correlated with glucose metabolic activity in the thalamus. These data provide the first evidence for a relation between alpha EEG power and thalamic activity in humans.     

A possible association between the Val158Met polymorphism of the catechol-O-methyl transferase gene and the personality trait of harm avoidance in Japanese healthy subjects

Catechol-O-methyltransferase (COMT) is an enzyme that degrades various biogenic amines, which have been hypothesized to be associated with personality traits. We investigated a possible relationship between the COMT Val158Met polymorphism and personality traits assessed by the Temperament and Character Inventory (TCI) in 139 healthy subjects in a Japanese population. The number of Met alleles of the COMT Val/Met genotype tended to relate to harm avoidance (HA) scores parametrically, while no significant difference was observed between genotype groups in either novelty seeking, reward dependence, persistence, self-directedness, cooperativeness or self-transcendence. These results suggest that the Val/Met polymorphism of the COMT gene may play a role in HA in Japanese population.     

Treatment response monitoring in patients with gastrointestinal stromal tumor using diffusion‐weighted imaging: preliminary results in comparison with positron emission tomography/computed tomography

We compared the parameters derived from diffusion‐weighted imaging (DWI) and positron emission tomography/computed tomography (PET/CT) for treatment response evaluation and response prediction in patients with gastrointestinal stromal tumor (GIST). Seven patients with histologically proven metastatic disease were enrolled. DWI and PET/CT data were collected from all patients at diagnosis and from six at follow‐up. All 37 lesions were identifiable in DWI with a sensitivity of 100%. To achieve higher accuracy, we used the apparent diffusion coefficient (ADC) of liver and background noise as thresholds for the measurement of the ADCs of lesions. Significant inverse correlations were found between ADC_{mean_thr} (ADC_mean with thresholds) and SUV_mean (mean standardized uptake value) (R² = 0.523, p < 0.001 at diagnosis, and R² = 0.916, p < 0.001 at follow‐up), between ADC_{mean_thr} and SUV_max (maximum SUV) (R² = 0.529, p < 0.001 at diagnosis, and R² = 0.761, p < 0.001 at follow‐up), between ΔADC_{mean_thr} (percentage change in ADC_{mean_thr}) and ΔSUV_mean (percentage change in SUV_mean) (R² = 0.384, p < 0.001), and between ΔADC_{mean_thr} and ΔSUV_max (percentage change in SUV_max) (R² = 0.500, p < 0.001). In lesion‐based analysis, pre‐treatment ADC_{mean_thr} outperformed SUV_mean and SUV_max in treatment response prediction, with an area under the receiver operating characteristic curve of 0.706. These results show that DWI can provide a quantitative assessment comparable with PET/CT in GIST lesion characterization, treatment response evaluation and response prediction. Copyright © 2012 John Wiley & Sons, Ltd.     

Sentence comprehension and word repetition: a positron emission tomography investigation.

Using positron emission tomography, visual presentation of sentences was shown to cause increased regional cerebral blood flow relative to word lists in the left lateral anterior superior and middle temporal gyri, attributable to cognitive processes that occur during sentence comprehension in addition to those carried out during word comprehension. Additional comparisons showed that repeating words (in a different context, when subjects did not attempt to learn the initial lists) led to significant patterns of both increased blood flow (left putamen and right caudate) and decreased blood flow (left posterior temporal lobe). Increases are argued to reflect retrieval of memory traces, whereas decreases reflect diminished necessity for processing of input. A decrease in the left inferior parietal lobe was attributable to other factors.     

No association between the -3081A/T polymorphism in the norepinephrine transporter gene promoter and personality traits in healthy subjects

There have been several data suggesting that norepinephrine neurotransmission is involved in the characterization of personality traits. Recently, the -3081A/T polymorphism in the promoter region of the norepinephrine transporter (NET) gene affecting promoter activity has been reported. In the present study, we studied the association between this NET polymorphism and personality traits in 553 Japanese healthy subjects. Personality traits were assessed by the Temperament and Character Inventory (TCI), and the NET genotypes were identified by a PCR-RFLP method. Multivariate two-factor analysis of covariance with genotype and gender as factors and with age as a covariate showed no association between the NET genotypes and the TCI dimension scores. The present study thus suggests that the -3081A/T polymorphism in the NET gene promoter is not involved in the characterization of personality traits in healthy subjects.     

A cerebral functional imaging study by positron emission tomography in healthy volunteers receiving true or sham acupuncture needling

Our recent studies have demonstrated that needling in Baihui, Shuigou and Shenmen enhances glucose metabolism in the frontal lobes, thalamus, temporal lobe, and the lentiform nucleus in vascular dementia. This study examined the effect of true, sham and overt needling in Waiguan (TE5) on cerebral changes by positron emission tomography (PET) technique. Eighteen healthy volunteers were randomized to receive overt control, true or sham needling therapy. To manipulate true needling, a needle was inserted into 15 ± 2 mm into Waiguan and “deqi” was achieved by proper needle manipulation. For sham needling, needles with a blunt tip were pushed against the skin as the shaft moved into the handle, giving an illusion of insertion. For overt placebo, blunt needles were used and subjects did not receive any needling penetration. The tracer used was ¹⁸fluoride-deoxygluocse. PET images obtained were processed and analyzed by the SPM2 software. Compared with overt needling, brain areas BA7, 13, 18, 19, 21, 22, 27, 38, 40, 42 and 45 in Waiguan true needling group were significantly activated and areas BA4, 6, 7, 19, 22 and 41 in sham needling group showed obvious activation. Compared to sham needling group, marked activation points were found in the areas of BA13 and 42 and left cerebellum in true needling group. Our study revealed a marked difference in brain metabolic changes between true and sham needling in Waiguan. Further studies are needed to explore the cerebral changes in patients with acupuncture and the pathological implications.