Single Region Of Interest Research Articles

Extracting Information from Cortical Connectivity Patterns Estimated from High Resolution EEG Recordings: A Theoretical Graph Approach

Over the last 20 years, a body of techniques known as high resolution EEG has allowed precise estimation of cortical activity from non-invasive EEG measurements. The availability of cortical waveforms from non-invasive EEG recordings allows to have not only the level of activation within a single region of interest (ROI) during a particular task, but also to estimate the causal relationships among activities of several cortical regions. However, interpreting resulting connectivity patterns is still an open issue, due to the difficulty to provide an objective measure of their properties across different subjects or groups. A novel approach addressed to solve this difficulty consists in manipulating these functional brain networks as graph objects for which a large body of indexes and tools are available in literature and already tested for complex networks at different levels of scale (Social, WorldWide-Web and Proteomics). In the present work, we would like to show the suitability of such approach, showing results obtained comparing separately two groups of subjects during the same motor task and two different motor tasks performed by the same group. In the first experiment two groups of subjects (healthy and spinal cord injured patients) were compared when they moved and attempted to move simultaneously their right foot and lips, respectively. The contrast between the foot-lips movement and the simple foot movement was addressed in the second experiment for the population of the healthy subjects. For both the experiments, the main question is whether the "architecture" of the functional connectivity networks obtained could show properties that are different in the two groups or in the two tasks. All the functional connectivity networks gathered in the two experiments showed ordered properties and significant differences from "random" networks having the same characteristic sizes. The proposed approach, based on the use of indexes derived from graph theory, can apply to cerebral connectivity patterns estimated not only from the EEG signals but also from different brain imaging methods.

Sex differences in the cerebral BOLD signal response to painful heat stimuli

There are limited data addressing the question of sex differences in pain-related cerebral processing. This study examined whether pain-related blood oxygenation level-dependent (BOLD) signal change measured with functional magnetic resonance imaging (fMRI) demonstrated sex differences, under conditions of equivalent pain perception. Twenty-eight healthy volunteers (17 women, 11 men) were subject to a fMRI scan while noxious heat stimuli were applied to the dorsum of the left foot. Significant BOLD signal modulation was observed in several nociceptive processing regions of interest (ROIs) in all subjects. There were no sex differences in the spatial extent of BOLD signal change for any ROI, but the signal amplitude was lower for women in most ROIs and significantly so for the primary somatosensory cortex (S1), the midanterior cingulate cortex, and the dorsolateral prefrontal cortex (DLPFC). The BOLD signal response could be positive or negative, and frequently, both polarities were observed within a single ROI. In most ROIs, women show proportionately more voxels with negative signal change than men, and this difference was statistically significant for the S1 and the DLPFC. The time course of the negative signal change was very similar to that of the positive signal change, suggesting that the latter was not "driving" the former. The location of negative and positive clusters formed distinct patterns in several of the ROIs, and these patterns suggest something other than a local "steal" phenomenon as an explanation for the negative signal changes. Sex differences in baseline cerebral blood flow may contribute to the BOLD signal differences observed in this study.

In Situ Background Estimation in Quantitative Fluorescence Imaging

Fluorescence imaging of bulk-stained tissue is a popular technique for monitoring the activities in a large population of cells. However, a precise quantification of such experiments is often compromised by an ambiguity of background estimation. Although, in single-cell-staining experiments, background can be measured from a neighboring nonstained region, such a region often does not exist in bulk-stained tissue. Here we describe a novel method that overcomes this problem. In contrast to previous methods, we determined the background of a given region of interest (ROI) using the information contained in the temporal dynamics of its individual pixels. Since no information outside the ROI is needed, the method can be used regardless of the staining profile in the surrounding tissue. Moreover, we extend the method to deal with background inhomogeneities within a single ROI, a problem not yet solved by any of the currently available tools. We performed computer simulations to demonstrate the accuracy of our method and give example applications in ratiometric calcium imaging of bulk-stained olfactory bulb slices. Converting the fluorescence signals into [Ca 2+] gives resting values consistent with earlier single-cell staining results, and odorant-induced [Ca 2+] transients can be quantitatively compared in different cells. Using these examples we show that inaccurate background subtraction introduces large errors (easily in the range of 100%) in the assessment of both resting [Ca 2+] and [Ca 2+] dynamics. The proposed method allows us to avoid such errors.

Brain and behaviour in children with 22q11.2 deletion syndrome: a volumetric and voxel-based morphometry MRI study

In people with velo-cardio-facial syndrome [or 22q11.2 deletion syndrome (22qDS)], a single interstitial deletion of chromosome 22q11.2 causes a wide spectrum of cognitive deficits ranging from global learning difficulties to specific cognitive deficits. People with 22qDS are also at high risk of developing attention-deficit/hyperactivity disorder and autism spectrum disorders in childhood, and schizophrenia in adolescence or adult life. However, the neurobiology of 22qDS, and the relationship between abnormalities in brain anatomy and behaviour, is poorly understood. Thus, we studied the neuroanatomy of 22qDS children using fully automated voxel-based morphometry (VBM) and manually traced single region-of-interest (ROI) analysis. Also, we investigated whether those brain regions that differed significantly between groups were related to behavioural differences within children with 22qDS. We compared the brain morphometry of 39 children and adolescents with 22qDS (mean age: 11 years, SD +/-3, IQ = 67, SD +/-10) and 26 sibling controls (mean age: 11 years, SD +/-3, IQ = 102, SD +/-12). Using VBM, we found, after correction for IQ, that individuals with 22qDS compared with controls had a significant reduction in cerebellar grey matter, and white matter reductions in the frontal lobe, cerebellum and internal capsule. Using single ROI analysis, we found that people with 22qDS had a significant (P < 0.05) reduction in bulk volume bilaterally in the occipital-parietal lobes, but a larger right caudate nucleus and lateral ventricles. Further, within people with 22qDS, there was a significant positive correlation between severity of (i) schizotypy score and grey matter volume of the temporo-occipital regions and the corpus striatum; (ii) emotional problems and grey matter volume of frontostriatal regions; and (iii) social behavioural difficulties and grey matter in frontostriatal regions. Thus, subjects with 22qDS have widespread changes in brain anatomy, particularly affecting white matter, basal ganglia and cerebellum. Also, within 22qDS, regionally specific differences in brain development may partially underpin behavioural differences. We suggest that there is preliminary evidence for specific vulnerability of the frontostriatal and cerebellar-cortical networks in 22qDS.

Clinicopathological examination of glioma by proton magnetic resonance spectroscopy background

Automation of proton magnetic resonance spectroscopy (MRS) in recent years has made it possible for MRS measurement to be performed in a shorter time than before, and the number of reports of its usefulness for the assessment of glioma malignancy has been increasing in the past several years. We studied the efficacy of proton MRS when used for glioma and conducted clinicopathological examination of glioma. The subjects were 15 patients who had received a pathological diagnosis of glioma at our hospital (6 cases of glioblastoma, 1 case of anaplastic astrocytoma, 4 cases of low-grade astrocytoma, and 4 cases of radiation necrosis); Siemens Magnetom Vision 1.5T was used for the study. Regions of interest (ROIs) were defined as the areas where abnormal signals were found on magnetic resonance imaging (MRI). Areas of primary peaks, such as choline (Cho), N-acetylaspartate (NAA), and lactate (Lac), were measured, and the ratios to normal brain tissue were examined. This study revealed a tendency of increased malignancy of glioma with a decrease in NAA. Some cases also displayed a decrease in Cho with an increase in malignancy. Assessment of malignancy must not be based on a single ROI alone, but several ROIs should be assessed comprehensively. Measurement was difficult when the tumor volume was small. Because diagnosis of very early glioma by MRS seemed difficult, other adjunctive diagnoses may be necessary. Proton MRS is very useful for diagnosis of glioblastoma.

Relationship between right ventricular ejection fraction and maximum exercise oxygen consumption: a methodological study in chronic heart failure patients

Background Peak oxygen consumption at maximum exercise (peak VO 2) predicts survival in chronic heart failure (CHF) patients. Right ventricular ejection fraction (RVEF) at rest has been reported to correlate with peak VO 2. We evaluated the strength and consistency of the association between peak VO 2 and RVEF measured by different radionuclide ventriculography (RNV) techniques in a prospective cohort study. Methods and results In 58 consecutive CHF patients (mean age, 53 years; 39 patients with dilated cardiomyopathy; 48 men), upright symptom-limited bicycle ergometry was performed. During exercise, ventilatory and gas exchange data were recorded and peak VO 2 was calculated. RVEF was calculated by use of first-pass (FP) RNV with single and dual region of interest (ROI) acquisition and planar multigated acquisition (MUGA). Irrespective of the method used, RVEF showed no relevant correlation with the corresponding peak VO 2 value ( r = 0.11 for FP single ROI, r = 0.06 for FP dual ROI, r = 0.16 for MUGA). Peak VO 2 or changes in peak VO 2 after 6 and 12 months of follow-up were not determined by RVEF measurements. Conclusion In CHF patients no association was found between peak VO 2 at maximum exercise and RVEF at rest with different RNV techniques. Changes in exercise capacity are not reliably reflected by changes in RVEF measurements at rest.

Effect of hypertonic saline on cerebral blood flow in poor-grade patients with subarachnoid hemorrhage.

The goal of this study was to examine the effects of hypertonic saline on cerebral blood flow (CBF) in poor-grade patients with subarachnoid hemorrhage. We administered 23.5% hypertonic saline (2 mL/kg IV) 1 time to 10 patients, 2 times to 7 patients, and 3 times to 1 patient. All patients had transcranial Doppler (TCD), intracranial pressure (ICP) monitoring, and analysis of serum sodium and osmolality; 6 had xenon CT (XeCT). Data were used to characterize the changes in CBF, cerebral vascular resistance (CVR), ICP, cerebral perfusion pressure (CPP), and potential rheological mechanisms of action. In the first treatment episode, CPP increased 26.8% (P=0.0003, at 28.3 minutes) from a rise in mean arterial blood pressure (ABP) of 10.5% (P=0.02, at 22.2 minutes) and a fall in ICP (-74.7%, P=0.002, at 60.0 minutes). Flow velocity (FV) of the middle cerebral artery increased 70.8% (P=0.00005, at 20.0 minutes), resulting in a corresponding fall in estimated CVR (-26.6%, P=0.01, at 16.3 minutes). The half-lives of effects on ABP, CPP, ICP, FV, and estimated CVR were 20.0, 53.6, 139.1, 42.7, and 27.1 minutes, respectively. In the second treatment episode, all these parameters had the same response except estimated CVR, which did not reach statistical significance. XeCT confirmed the increase in CBF (22.9%, P=0.02) without regional differences. A fall in CBF after hypertonic saline was identified in only a single region of interest in a patient in whom baseline flow was low but not infarcted. Serum sodium rose by 11.4 and 8.8 mmol/L, and osmolality rose by 26.7 and 16.3 mosm/L in the first and second treatment episodes, respectively. Hemoglobin decreased by 0.7 and 0.6 g/L and hematocrit decreased by 1.9% and 2.4% in the first and second treatment episodes, respectively. We found that 23.5% hypertonic saline increases CBF in poor-grade patients with subarachnoid hemorrhage. These effects are associated with improved indexes of blood rheology. Potential therapeutic benefits are discussed.

Functional MRI in Epilepsy

*Department of Neurology, Medical College of Wisconsin, Milwaukee, Wisconsin, U.S.A.; †University Hospital Gent, Gent, Belgium; ‡Departments of Diagnostic Radiology and Neurosurgery, Yale University, New Haven, Connecticut; §Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania; Clinical Epilepsy Section, National Institutes of Health, Bethesda, Maryland; ¶Department of Radiology, Mayo Clinic, Rochester, Minnesota; and **Department of Neurology, Medical College of Georgia, Augusta, Georgia, U.S.A.

Optimizing the method to calculate right ventricular ejection fraction from first-pass data acquired with a multicrystal camera.

The advantage of radionuclide angiographic techniques used to measure right ventricular ejection fraction (RVEF) is geometry independence, but the weakness is right atrial (RA) overlap. To minimize the effect of RA counts on right ventricular time activity curve (TAC), two regions of interest (ROI), one drawn for the end-diastolic image and one for the end-systolic image, are used for the calculation of RVEF from equilibrium gated blood pool scans (GBPS) and from gated first-pass studies with an Anger camera. A multicrystal camera offers both temporal separation of the bolus to the right side of the heart and good count statistics; therefore first-pass studies performed on a multicrystal camera theoretically should yield the most accurate measurements of RVEF, but few studies have been performed to validate RVEF against a reliable gold standard. To develop and validate an accurate method to measure RVEF from multicrystal first-pass data, 25 patients underwent sequential cine-MRI, first-pass radionuclide angiography, and gated equilibrium imaging. Five additional healthy volunteers underwent cine-MRI alone. Right and left ventricular volumes were measured from serial short axis cine-MRI views according to Simpson's rule. Three methods were used to calculate RVEF from first-pass data: a single ROI method, a dual ROI method, and a method in which a single ROI is applied to RA subtracted first-pass dynamic data. Five additional healthy volunteers underwent cine-MRI alone. When right ventricular stroke volume was plotted versus left ventricular stroke volume for the 5 volunteers and the 15 patients without valvular regurgitation, the regression line was not significantly different from the line of identity, supporting the accuracy of cine-MRI to measure RVEF. The RVEF by cine-MRI ranged from 34% to 59%; first-pass RVEF with a single ROI from 26% to 48%; first-pass RVEF with two ROIs from 31% to 59%; first-pass RVEF with RA subtracted single ROI from 29% to 60%; and RVEF from GBPS with multiple ROIs from 28% to 55%. The regressions for all three of the first-pass methods versus cine-MRI were significant (p < 0.01) as was the regression for the equilibrium GBPS versus cine-MRI but the correlation was weaker. The regressions for the 2-ROI method and for the RA subtracted single ROI method were not significantly different from the line of identity, whereas the regressions for both the single ROI method and for equilibrium GBPS were significantly different from the line of identity (p < 0.01). Cine-MRI can be used to validate radionuclide algorithms. Of the four radionuclide methods for measuring RVEF that were assessed, the first-pass 2-ROI method and the first-pass RA subtracted single ROI are the most accurate, the first-pass single ROI method underestimates RVEF, and the RVEF values measured from GBPS are less accurate.

CT Diagnosis of Renal Angiomyolipoma: The Importance of Detecting Small Amounts of Fat

Six patients were reviewed who had renal angiomyolipoma (1.2-4.0 cm) in which only minimal amounts of fat were evident on CT. The fat content of the lesion was appreciated because tissue attenuation measurements of small areas of low attenuation within the tumors were performed and because thin-section (5-mm) and nonenhanced CT scans were used. The fat content of the lesions could be identified on 10-mm sections in three cases but only on 5-mm sections in three others. In two cases, fat was seen only on the nonenhanced 5-mm thin sections. Careful sampling of low-density regions within the mass must be performed because a single region of interest over the entire tumor will produce an average attenuation in the soft-tissue range. The use of 5-mm thin sections and thin, nonenhanced CT sections increases spatial and density resolution and decreases susceptibility to partial-volume effects. In a correlative study, no areas of fat were detected in a review of 100 well-circumscribed (4.0 cm or smaller) renal cell carcinomas. Detecting the existence of fat in a renal lesion will establish the diagnosis of angiomyolipoma and is the only radiologic finding that can differentiate it from renal cell carcinoma. Thus, unnecessary surgery will be avoided in these cases.

CT diagnosis of renal angiomyolipoma: the importance of detecting small amounts of fat.

Six patients were reviewed who had renal angiomyolipoma (1.2-4.0 cm) in which only minimal amounts of fat were evident on CT. The fat content of the lesion was appreciated because tissue attenuation measurements of small areas of low attenuation within the tumors were performed and because thin-section (5-mm) and nonenhanced CT scans were used. The fat content of the lesions could be identified on 10-mm sections in three cases but only on 5-mm sections in three others. In two cases, fat was seen only on the nonenhanced 5-mm thin sections. Careful sampling of low-density regions within the mass must be performed because a single region of interest over the entire tumor will produce an average attenuation in the soft-tissue range. The use of 5-mm thin sections and thin, nonenhanced CT sections increases spatial and density resolution and decreases susceptibility to partial-volume effects. In a correlative study, no areas of fat were detected in a review of 100 well-circumscribed (4.0 cm or smaller) renal cell carcinomas. Detecting the existence of fat in a renal lesion will establish the diagnosis of angiomyolipoma and is the only radiologic finding that can differentiate it from renal cell carcinoma. Thus, unnecessary surgery will be avoided in these cases.

Scintigraphic diagnosis of tricuspid regurgitation.

The authors describe a simple technique for diagnosis of tricuspid regurgitation. Red blood cells were labeled in vivo with 99mTc and 22 patients were studied with ECG-gated blood-pool imaging of the liver. A single region of interest was manually drawn around the liver and a time-activity curve obtained. The per cent change in liver counts during the cardiac cycle was found to be significantly higher in the 12 patients with tricuspid regurgitation (Group I) (mean, 4.04 +/- 1.6%; range, 1.3-21.4%) compared with the 10 controls (Group II) (mean, 0.35 +/- 0.16%; range, 0.013-1.3%) (p less than 0.05). Using a 1% change in liver counts as the criterion of a positive study, all 12 cases in Group I were diagnosed correctly, but there was one false positive in Group II; thus the sensitivity was 100% and the specificity 90%.

TEM Specimen Preparation from Micro-Areas of Metallurgical Interest

Most metallurgical phenomena of industrial interest can trace their origin to specific regions in operating components. Determining the microstructural changes that accompany the origins of these metallurgical phenomena helps considerably in their overall understanding. Examples include studies of microstructural changes at crack tips, surface oxidation effects on base material, and narrow reaction zones in suitably heat treated material. For such microareas, only a single region of interest is usually available for microstructural examination, making TEM specimen preparation procedures extremely critical.304 austenitic steel is susceptible to intergranular stress corrosion cracking when subjected to a corrosive environment in the presence of stress and a sensitized microstructure. The latter is characterized by chromium carbide, Cr23C6, at the grain boundaries. Confirmation of the presence of these carbides at the tip of an intergranular crack created in an environment can be provided by TEM examination. The microarea of interest can be pinpointed by using selective platinum washers during electropolishing, yielding electron-transparent regions of the type shown in figure 1.