The EEG microstate topography is predominantly determined by intracortical sources in the alpha band.

Human brain electric activity can be measured at high temporal and fairly good spatial resolution via electroencephalography (EEG). The EEG microstate analysis is an increasingly popular method used to investigate this activity at a millisecond resolution by segmenting it into quasi-stable states of approximately 100 ms duration. These so-called EEG microstates were postulated to represent atoms of thoughts and emotions and can be classified into four classes of topographies A through D, which explain up to 90% of the variance of continuous EEG. The present study investigated whether these topographies are primarily driven by alpha activity originating from the posterior cingulate cortex (all topographies), left and right posterior cortices, and the anterior cingulate cortex (topographies A, B, and C, respectively). We analyzed two 64-channel resting state EEG datasets (N = 61 and N = 78) of healthy participants. Sources of head-surface signals were determined via exact low resolution electromagnetic tomography (eLORETA). The Hilbert transformation was applied to identify instantaneous source strength of four EEG frequency bands (delta through beta). These source strength values were averaged for each participant across time periods belonging to a particular microstate. For each dataset, these averages of the different microstate classes were compared for each voxel. Consistent differences across datasets were identified via a conjunction analysis. The intracortical strength and spatial distribution of alpha band activity mainly determined whether a head-surface topography of EEG microstate class A, B, C, or D was induced. EEG microstate class C was characterized by stronger alpha activity compared to all other classes in large portions of the cortex. Class A was associated with stronger left posterior alpha activity than classes B and D, and class B was associated with stronger right posterior alpha activity than A and D. Previous results indicated that EEG microstate dynamics reflect a fundamental mechanism of the human brain that is altered in different mental states in health and disease. They are characterized by systematic transitions between four head-surface topographies, the EEG microstate classes. Our results show that intra-cortical alpha oscillations, which likely reflect decreased cortical excitability, primarily account for the emergence of these classes. We suggest that microstate class dynamics reflect transitions between four global attractor states that are characterized by selective inhibition of specific intra-cortical regions.

The functional significance of EEG microstates--Associations with modalities of thinking.

The momentary, global functional state of the brain is reflected by its electric field configuration. Cluster analytical approaches consistently extracted four head-surface brain electric field configurations that optimally explain the variance of their changes across time in spontaneous EEG recordings. These four configurations are referred to as EEG microstate classes A, B, C, and D and have been associated with verbal/phonological, visual, subjective interoceptive-autonomic processing, and attention reorientation, respectively. The present study tested these associations via an intra-individual and inter-individual analysis approach. The intra-individual approach tested the effect of task-induced increased modality-specific processing on EEG microstate parameters. The inter-individual approach tested the effect of personal modality-specific parameters on EEG microstate parameters. We obtained multichannel EEG from 61 healthy, right-handed, male students during four eyes-closed conditions: object-visualization, spatial-visualization, verbalization (6 runs each), and resting (7 runs). After each run, we assessed participants' degrees of object-visual, spatial-visual, and verbal thinking using subjective reports. Before and after the recording, we assessed modality-specific cognitive abilities and styles using nine cognitive tests and two questionnaires. The EEG of all participants, conditions, and runs was clustered into four classes of EEG microstates (A, B, C, and D). RMANOVAs, ANOVAs and post-hoc paired t-tests compared microstate parameters between conditions. TANOVAs compared microstate class topographies between conditions. Differences were localized using eLORETA. Pearson correlations assessed interrelationships between personal modality-specific parameters and EEG microstate parameters during no-task resting. As hypothesized, verbal as opposed to visual conditions consistently affected the duration, occurrence, and coverage of microstate classes A and B. Contrary to associations suggested by previous reports, parameters were increased for class A during visualization, and class B during verbalization. In line with previous reports, microstate D parameters were increased during no-task resting compared to the three internal, goal-directed tasks. Topographic differences between conditions included particular sub-regions of components of the metabolic default mode network. Modality-specific personal parameters did not consistently correlate with microstate parameters except verbal cognitive style which correlated negatively with microstate class A duration and positively with class C occurrence. This is the first study that aimed to induce EEG microstate class parameter changes based on their hypothesized functional significance. Beyond the associations of microstate classes A and B with visual and verbal processing, respectively, our results suggest that a finely-tuned interplay between all four EEG microstate classes is necessary for the continuous formation of visual and verbal thoughts. Our results point to the possibility that the EEG microstate classes may represent the head-surface measured activity of intra-cortical sources primarily exhibiting inhibitory functions. However, additional studies are needed to verify and elaborate on this hypothesis.

[The demonstration of blood flow in focal breast lesions by power-Doppler sonography. A new approach to assessment?]. / Blutflussdarstellung in Herdbefunden der Mamma mittels der Power-Doppler-Sonographie. Ein neuer Ansatz zur Dignitätsbeurteilung?

PURPOSE: Power-Doppler sonography is regarded as a very sensitive method for detecting low-velocity and low-volume blood flows. The purpose of our study was to investigate whether increased vascularity in breast carcinoma can be visualized by power-Doppler sonography and whether new criteria for differentiating benign and malign lesions can be found. METHOD: 315 patients were examined with a 13-MHz high-resolution linear transducer. If a suspicious lesion was found, it was evaluated further by power-Doppler sonography. Compared to normal breast parenchyma (reference structure), a focal increase in blood flow signals was registered using a 3-step grading system with a 4th step for no flow increase. RESULTS: In 97 cases the sonographic findings were correlated with histology (n = 95) or cytology (n = 2). There were 50 benign lesions, 42 cases of invasive and 5 cases of in-situ carcinoma. 73.5% benign lesions showed no or just minimal increases in flow signal. 81% of invasive cancer presented middle- or high-flow increases compared to normal breast parenchyma. The extend of flow increase was linked to tumor size in invasive cancer. In stage T1b to T4, 94.3% of invasive carcinoma presented middle or high flow increases. CONCLUSION: Power-Doppler sonography is able to visualize vascularization in breast tumors. According to first clinical results PD sonography is a promising additional diagnostic tool which seems to offer new criteria for differential diagnosis in breast tumors.

[The clinical value of air sonography in the diagnosis of meniscus lesions. A prospective study of 50 knee joints]. / Klinische Wertigkeit der Luftsonographie bei der Diagnostik der Meniskusläsionen. Eine prospektive Studie an 50 Kniegelenken.

This paper shows the results of using air as a contrast medium in ultrasonography of the menisci (aerosonography). 100 menisci (50 knees) were examined with aerosonography and in 93 = 93% the findings were proven to be true by subsequent arthroscopy. 6% of the findings were false positive (2 medial menisci and 4 lateral menisci). One false negative finding concerned a lesion at the free inner edge of the lateral meniscus. Not one single lesion of the medial meniscus was totally missed. The sensitivity of aerosonography is 97.8%, the specificity 89.1%. The predictive value is 88%, the accuracy is 93%. Considering the medial meniscus alone the aerosonographic diagnosis proved to be true in 96% (sensitivity for the medial meniscus 100%, specificity 87.5%, predictive value 94.4%, accuracy 96%). 90% of the aerosonographic diagnosis concerning the lateral meniscus were confirmed by arthroscopy (sensitivity for the lateral meniscus 90.9%, specificity 89.1%, predictive value 71.4%, accuracy 90%).

[Imaging methods in diagnosis and differential diagnosis of breast cancer]. / Bildgebende Verfahren zur Diagnostik und Differentialdiagnostik des Mammakarzinoms.

The diagnosis of breast cancer is primarily based on X-ray mammography. Under optimal conditions, a sensitivity of approximately 90% can be achieved. When strict criteria of indication are observed for the additional use of ultrasound or contrast-enhanced MRI, the sensitivity can be increased to about 98%. In addition, the differential diagnosis between benign and malignant lesions can be improved and the rate of biopsies due to false-positive mammograms can be reduced. However, further investigation with ultrasound or MRI of dense or mastopathic breasts that are clinically asymptomatic is not indicated, since it reduces specificity without significant gain of sensitivity.

[Modern ultrasound diagnosis of the female breast. Possibilities and limits]. / Moderne Ultraschalldiagnostik der weiblichen Brust. Möglichkeiten und Grenzen.

PURPOSE: The rapid development of sonography made it seem advisable to reconsider the clinical value of breast ultrasound. Our experience with new techniques and current research will be presented. METHODOLOGY: Various indications for breast ultrasound will be discussed. New Doppler techniques extending the ability to detect low blood flow will be presented. RESULTS: The differentiation of suspicious areas seen on mammography and the detection of occult breast cancer are the major challenges in breast ultrasound. A limitation is its low capability to visualize microcalcifications. A promising approach is the development of highly sensitive, color-coded techniques for the detection of minimal blood flow. Another progress is the development of an ultrasound contrast medium that is not inactivated during first lung passage. CONCLUSION: Breast ultrasound provides complementary information to mammography. Using stable ultrasound contrast medium and highly sensitive color-coded Doppler techniques for the detection of minimal blood flow, we hope to find new criteria for the diagnosis of angioneogenesis in breast cancer.

13 MHz high-frequency sonography of the lateral ankle joint ligaments and the tibiofibular syndesmosis in anatomic specimens.

In this study, the ligaments of the ankle joint and the tibiofibular syndesmosis were examined in formalin-fixed anatomic specimens using a 13 MHz sonographic scanner. For this purpose, 48 specimens of the ankle joint were examined, and the anterior tibiofibular, anterior talofibular, and calcaneofibular ligaments were marked by sonographically guided dye injection. The markings were checked during the subsequent dissection. The number of identifications reached 89.6% for the anterior tibiofibular and talofibular ligaments and 87% for the calcaneofibular ligament. The results show that the most frequently injured ligaments of the ankle joint can be visualized reliably by use of 13 MHz high-frequency sonography.

Evaluation of breast lesions by power Doppler sonography.

The aim of this study was to determine the value of power Doppler sonography in the detection of tumor vascularity in breast lesions and to find new diagnostic criteria for differential diagnosis. Power Doppler sonography was prospectively performed in 102 patients with 118 histologic (n = 116) and cytologic (n = 2) results. A semisubjective scoring system for the intratumoral increase in blood flow compared with the flow in normal breast parenchyma (reference structure) was introduced and the flow pattern registered. The difference in the flow increase for benign and malignant breast disease was highly significant (p < or = 0.0001). This applied especially to invasive cancer above a maximum tumor diameter of 5 mm excluding cancer stage Tis and T1a. A positive correlation between cancer size and flow increase were found. The flow pattern was an additional feature. The sensitivity was calculated to be between 74.5 and 78.8%, and the specificity between 74.6 and 77.8%. The level of flow increase in Power Doppler sonography is an important feature in the differential diagnosis of breast lesions and should be considered together with the established criteria in B-mode ultrasound. The flow pattern might also add some important information.

[Comparison between current and high resolution ultrasound for diagnosis of breast lesions]. / Vergleich zwischen herkömmlicher und hochauflösender Sonographie für die Diagnostik von Mammaläsionen.

AIM: To assess the value of high-resolution ultrasound in the diagnosis of breast lesions. METHOD: Fifty women with a clinically suspicious breast mass were examined with mammography, conventional and high-resolution sonography. Ultrasound was performed with a linear-array 7.5-mHz transducer and an annular-array 13.0 MHz transducer. RESULTS: Histology showed carcinoma in 28 patients, fibrocystic changes in 20 and fibroadenoma in 2. High-resolution ultrasound characterized 18 lesions more accurately than conventional ultrasound, including 13 carcinomas, 3 fibrocystic changes and 2 fibroadenomas. The size of 8 carcinomas was measured more accurately with high-resolution ultrasound than with conventional ultrasound. CONCLUSION: High-resolution ultrasound is more valuable in the differentiation and size determination of breast lesions than conventional ultrasound.

[Diagnosis of the site and extent of breast carcinoma]. / Lokalisations- und Ausdehnungsdiagnostik beim Mammakarzinom.

The value of X-ray-mammography, ultrasound, and MRI are compared with regard to their results in localization, differential diagnosis, and staging of carcinomas of the breast. For microcalcifications that are only imaged by mammography, X-ray is superior to the other imaging modalities and remains method of choice. Ultrasound is the most useful to differentiate cystic and solid lesions. The value of MRI is not yet proved sufficiently except in conservative and plastic surgery of breast carcinoma.

Lateral ankle ligaments and tibiofibular syndesmosis. 13-MHz high-frequency sonography and MRI compared in 20 patients.

To test the ability of ultra-high frequency ultrasound (13 MHz scanner) to distinguish between intact and ruptured ligaments on the lateral side of the ankle, we examined 20 patients with an acute inversion injury with MRI and ultrasound. When judged by the MRI diagnosis, an injured anterior talofibular ligament was correctly diagnosed by ultrasound in 13 of 14 and an intact anterior talofibular ligament in 5 of 6 patients. In the case of the calcaneofibular ligament, 4 ruptured and 16 intact ligaments were diagnosed equally well with both methods. The injured anterior tibiofibular ligament was correctly diagnosed by ultrasound in 6 of 9 patients, while the intact ligament was correctly recognized in 10 of 11 patients. Our findings indicate that it is possible to distinguish injured from intact ligaments sonographically.

[13-MHc high frequency ultrasound of the lateral ligaments of the ankle joint and the anterior tibia-fibular ligament. Comparison and results of MRI in 64 patients]. / 13-MHz-Hochfrequenzsonographie der lateralen Bänder des oberen Sprunggelenkes einschliesslich der ventralen Syndesmose. Ein Vergleich mit den Ergebnissen der MRT bei 64 Patienten.

PURPOSE: Determination of the value of 13-MHz high-frequency ultrasound in the diagnosis of acute injuries of the lateral ankle ligaments and the anterior tibiofibular ligament by comparison with MRI. METHOD: Sonography was performed prospectively in 64 acutely injured patients using a mechanical 13-MHz sector probe; for diagnosis of the anterior tibiofibular ligament a 15-MHz sector probe was employed during the course of this trial. Using a 0.2-T unit for MRI examination, T1-weighted (TR 580 ms, TE 24 ms) and T2-weighted (TR 3000 ms, TE 80 ms) spin-echo sequences were obtained in various oblique axial imaging planes. RESULTS: In the differentiation of intact and injured ligaments, ultrasound and MRI agreed in 95.3% of cases for the anterior fibulotalar ligament, in 88.3% for the fibulocalcanear ligament and in 85.0% for the anterior tibiofibular ligament. CONCLUSION: Lesions of the anterior talofibular and fibulocalcanear ligament can be accurately demonstrated by ultrasound if a 13-MHz sector scanner is used. The detection of lesions in the anterior tibiofibular ligament is more difficult. With increasing experience and by using a 15-MHz sector scanner, better results can be expected for this ligament.