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At least 1,531 records · Page 85Linked to original sources
PubMed2005

Comparison of manual vs. automated multimodality (CT-MRI) image registration for brain tumors.

Computed tomgoraphy-magnetic resonance imaging (CT-MRI) registrations are routinely used for target-volume delineation of brain tumors. We clinically use 2 software packages based on manual operation and 1 automated package with 2 different algorithms: chamfer matching using bony structures, and mutual information using intensity patterns. In all registration algorithms, a minimum of 3 pairs of identical anatomical and preferably noncoplanar landmarks is used on each of the 2 image sets. In manual registration, the program registers these points and links the image sets using a 3-dimensional (3D) transformation. In automated registration, the 3 landmarks are used as an initial starting point and further processing is done to complete the registration. Using our registration packages, registration of CT and MRI was performed on 10 patients. We scored the results of each registration set based on the amount of time spent, the accuracy reported by the software, and a final evaluation. We evaluated each software program by measuring the residual error between "matched" points on the right and left globes and the posterior fossa for fused image slices. In general, manual registration showed higher misalignment between corresponding points compared to automated registration using intensity matching. This error had no directional dependence and was, most of the time, larger for a larger structure in both registration techniques. Automated algorithm based on intensity matching also gave the best results in terms of registration accuracy, irrespective of whether or not the initial landmarks were chosen carefully, when compared to that done using bone matching algorithm. Intensity-matching algorithm required the least amount of user-time and provided better accuracy.

Algorithms↗
PubMed2004

Multimodal integration of EEG, MEG and fMRI data for the solution of the neuroimage puzzle.

In this paper, advanced methods for the modeling of human cortical activity from combined high-resolution electroencephalography (EEG), magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) data are presented. These methods include a subject's multicompartment head model (scalp, skull, dura mater, cortex) constructed from magnetic resonance images, multidipole source model and regularized linear inverse source estimates of cortical current density. Determination of the priors in the resolution of the linear inverse problem was performed with the use of information from the hemodynamic responses of the cortical areas as revealed by block-designed (strength of activated voxels) fMRI. Examples of the application of these methods to the estimation of the time varying cortical current density activity in selected region of interest (ROI) are presented for movement-related high-resolution EEG data.

Algorithms↗
PubMed2006

Multimodal imaging of the sonic organ of Porichthys notatus, the singing midshipman fish.

The sonic midshipman fish, Porichthys notatus, is a bottom-dwelling species whose swim bladder has evolved into a highly specialized, sound-producing organ. The males of this species exist in two distinct morphs with different physical characteristics and sexual strategies. The Type I males have a much larger sound organ and are capable of generating a loud approximately 100 Hz tone continuously for over an hour to attract females. This sound is produced by sonic muscle and represents one of the most superfast and super-enduring striated muscles found in nature. Each fiber contains a hollow, tubular contractile apparatus composed of radially arranged myofibrils with extremely broad Z-bands that are supported by a desmin-rich cytoskeleton. We have used micro computed tomography (CT) imaging and magnetic resonance (MR) imaging to visualize the location of the sonic organ in an intact male fish. We have also obtained high-resolution MR images of the excised swim bladders from both male types. The images of the Type I sonic organ are strikingly detailed and high-contrast, revealing both the internal organization of the bladder and the crisscrossing muscle fibers and their mode of attachment to the underlying bladder. The high-contrast variation in these images is due to different T(2) values for fiber bundles and the spaces between the bundles. Direct MR imaging of intact Type I sonic organ in Type I midshipman fish is a powerful approach to understanding the contraction of this superfast muscle and the oscillation of its bladder to produce mating calls, and how placement of the sonic organ in the body of the fish sheds light on its prodigious ability to produce and transmit its loud mating call.

Air Sacs↗
PubMed2006

Investigations on multimodal sensory integration: texture, taste, and ortho- and retronasal olfactory stimuli in concert.

Perceptual interactions between odour and oral texture were explored in a study in which a cream odour was presented ortho- or retronasally at well-defined moments whilst milk-like foods with different viscosities, produced by adding a thickener, were present in the mouth. Gaseous (odour) and liquid (texture) pulses were presented using a specially-developed computer-controlled system of air-dilution olfactometry and pumps. Odour pulses, lasting 2 s, were presented either during a 3-s period in which a liquid filled the oral cavity, during a 3-s period in which the liquid was manipulated orally or during the swallowing of the liquid. Subjects rated the intensity of overall flavour, thickness and creaminess. Perceived flavour intensity was reduced with increasing viscosity of the liquid, irrespective of whether or not the odour was presented ortho- or retronasally. The odour stimulus increased the intensities of thickness and creaminess, but only when the odour was presented retronasally that is as if the odour would have originated from the liquid. Furthermore, this enhancement was most pronounced when odours coincided with swallowing, less pronounced when odours coincided with oral manipulation and absent when presented during mouth filling. The results suggest that cross-modal interactions are the rule rather than the exception, provided that multi-modal sensory integration has occurred.

Adult↗
PubMed2004

Multimodal assessment of cortical activation during apple peeling by NIRS and fMRI.

An intriguing application of neuroimaging is directly measuring actual human brain activities during daily living. To this end, we investigated cortical activation patterns during apple peeling. We first conducted a pilot study to assess the activation pattern of the whole lateral cortical surface during apple peeling by multichannel near-infrared spectroscopy (NIRS) and detected substantial activation in the prefrontal region in addition to expected activations extending over the motor, premotor and supplementary motor areas. We next examined cortical activation during mock apple peeling by simultaneous measurement using multichannel NIRS and functional magnetic resonance imaging (fMRI) in four subjects. We detected activations extending over the motor, premotor and supplementary motor areas, but not in the prefrontal cortex. Thus, we finally focused on the prefrontal cortex and examined its activation during apple peeling in 12 subjects using a multichannel NIRS. We subsequently found that regional concentrations of oxygenated hemoglobin significantly increased in the measured region, which encompassed portions of the dorsolateral, ventrolateral and frontopolar areas of the prefrontal cortex. The current study demonstrated that apple peeling as practiced in daily life recruited the prefrontal cortex but that such activation might not be detected for less laborious mock apple peeling that can be performed in an fMRI environment. We suggest the importance of cortical study of an everyday task as it is but not as a simplified form; we also suggest the validity of NIRS for this purpose. Studies on everyday tasks may serve as stepping stone toward understanding human activities in terms of cortical activations.

Activities of Daily Living↗
PubMed2005

Estimation of the cortical functional connectivity with the multimodal integration of high-resolution EEG and fMRI data by directed transfer function.

Nowadays, several types of brain imaging device are available to provide images of the functional activity of the cerebral cortex based on hemodynamic, metabolic, or electromagnetic measurements. However, static images of brain regions activated during particular tasks do not convey the information of how these regions communicate with each other. In this study, advanced methods for the estimation of cortical connectivity from combined high-resolution electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) data are presented. These methods include a subject's multicompartment head model (scalp, skull, dura mater, cortex) constructed from individual magnetic resonance images, multidipole source model, and regularized linear inverse source estimates of cortical current density. Determination of the priors in the resolution of the linear inverse problem was performed with the use of information from the hemodynamic responses of the cortical areas as revealed by block-designed (strength of activated voxels) fMRI. We estimate functional cortical connectivity by computing the directed transfer function (DTF) on the estimated cortical current density waveforms in regions of interest (ROIs) on the modeled cortical mantle. The proposed method was able to unveil the direction of the information flow between the cortical regions of interest, as it is directional in nature. Furthermore, this method allows to detect changes in the time course of information flow between cortical regions in different frequency bands. The reliability of these techniques was further demonstrated by elaboration of high-resolution EEG and fMRI signals collected during visually triggered finger movements in four healthy subjects. Connectivity patterns estimated for this task reveal an involvement of right parietal and bilateral premotor and prefrontal cortical areas. This cortical region involvement resembles that revealed in previous studies where visually triggered finger movements were analyzed with the use of separate EEG or fMRI measurements.

Adult↗
PubMed2007

Multimodal fMRI tractography in normal subjects and in clinically recovered traumatic brain injury patients.

In this study, we defined an operator-independent protocol for reconstructing the anatomical connections originating from fMRI activations in order to demonstrate that results obtained with this protocol are affected by alterations of functional activations. Seven healthy volunteers and two patients who sustained traumatic brain injury underwent an fMRI with a finger tapping task and a DTI scan. Cortical fMRI activations were used directly as seed mask for tractography for the reconstruction of individual motor pathways. On patients we observed a different motor network if compared to healthy subjects. However, when the activations of healthy subjects were used as seed masks for the tractography in patients, we observed for the patients a pattern of connectivity more similar to what was observed for healthy subjects. At the same time, when the activations of patients were used for the tractography on healthy subjects, we obtained patterns of connectivity similar to those obtained for patients. These results show the potential of the integration of fMRI and tractography for clarifying the mechanisms of cortical plasticity in the recovery of motor functions.

Adult↗
PubMed2005

Memory strength and repetition suppression: multimodal imaging of medial temporal cortical contributions to recognition.

Declarative memory permits an organism to recognize stimuli that have been previously encountered, discriminating them from those that are novel. One basis for recognition is item memory strength, which may support the perception of stimulus familiarity. Though the medial temporal lobes are known to be critical for declarative memory, at present the neural mechanisms supporting perceived differences in memory strength remain poorly specified. Here, functional MRI (fMRI) and anatomically constrained magnetoencephalography (MEG) indexed correlates of graded memory strength in the human brain, focusing on medial temporal cortex. fMRI revealed a decrease in medial temporal cortical activation that tracked parametric levels of perceived memory strength. Anatomically constrained MEG current estimates revealed that strength-dependent signal reductions onset within 150-300 ms. Memory strength appears to be rapidly signaled by medial temporal cortex through repetition suppression (activation reductions), providing a basis for the subjective perception of stimulus familiarity or novelty.

Adult↗
PubMed2006

Progesterone and its derivatives are neuroprotective agents in experimental diabetic neuropathy: a multimodal analysis.

One important complication of diabetes is damage to the peripheral nervous system. However, in spite of the number of studies on human and experimental diabetic neuropathy, the current therapeutic arsenal is meagre. Consequently, the search for substances to protect the nervous system from the degenerative effects of diabetes has high priority in biomedical research. Neuroactive steroids might be interesting since they have been recently identified as promising neuroprotective agents in several models of neurodegeneration. We have assessed whether chronic treatment with progesterone (P), dihydroprogesterone (DHP) or tetrahydroprogesterone (THP) had neuroprotective effects against streptozotocin (STZ)-induced diabetic neuropathy at the neurophysiological, functional, biochemical and neuropathological levels. Using gas chromatography coupled to mass-spectrometry, we found that three months of diabetes markedly lowered P plasma levels in male rats, and chronic treatment with P restored them, with protective effects on peripheral nerves. In the model of STZ-induced of diabetic neuropathy, chronic treatment for 1 month with P, or with its derivatives, DHP and THP, counteracted the impairment of nerve conduction velocity (NCV) and thermal threshold, restored skin innervation density, and improved Na(+),K(+)-ATPase activity and mRNA levels of myelin proteins, such as glycoprotein zero and peripheral myelin protein 22, suggesting that these neuroactive steroids, might be useful protective agents in diabetic neuropathy. Interestingly, different receptors seem to be involved in these effects. Thus, while the expression of myelin proteins and Na(+),K(+)-ATPase activity are only stimulated by P and DHP (i.e. two neuroactive steroids interacting with P receptor, PR), NCV, thermal nociceptive threshold and intra-epidermal nerve fiber (IENF) density are also affected by THP, which interacts with GABA-A receptor. Because, a therapeutic approach with specific synthetic receptor ligands could avoid the typical side effects of steroids, future experiments will be devoted to evaluating the role of PR and GABA-A receptor in these protective effects.

20-alpha-Dihydroprogesterone↗
PubMed2006

Evaluation of a multimodal management of prematurity-related spasticity.

To examine the efficacy of a rehabilitation protocol, focusing on spasticity management through botulinum toxin A injections in the lower limbs, an etiologically homogeneous group of 57 prematurely born children with cerebral palsy was prospectively evaluated (minimum follow-up 18 months) under pragmatic conditions. Gross Motor Function Classification System categories were: I = 12, II = 9, III = 16, IV = 15, V = 4. Outcome was evaluated with goniometry, Gross Motor Function Measure, functional goal attainment at baseline and in subsequent months, the Gross Motor Function Classification System, functional mobility status, and parents' satisfaction at more than 18 months after first botulinum toxin. Goniometry demonstrated significantly improved range of movement in lower limbs at 10 days and 1 month after botulinum toxin. Differences persisted >18 months at the popliteal angles (P < 0.001). Gross Motor Function Measure changed significantly in 20 children (8 points in total score) at 3 months after first botulinum toxin (P < 0.0001) with less significant results thereafter. Predetermined functional goals were achieved in 61% at >18 months. Parents were satisfied in approximately 90% of the cases. Eighteen of 57 children (31.57%) changed Gross Motor Function Classification System status over a mean of 33.8 months (18-48) follow-up. Most significant gains were recorded in the severely involved group IV, where 10 of 15 (66.66%) improved. The high percentage of change in group IV implies the importance of gained sitting balance due to spasticity management.

Adolescent↗
PubMed2003

Evaluation of a multimodality image (CT, MRI and PET) coregistration procedure on phantom and head and neck cancer patients: accuracy, reproducibility and consistency.

BACKGROUND AND PURPOSE: In radiotherapy planning of head and neck tumors, coregistration of various anatomical (e.g. CT and MRI) and functional (e.g. PET) images is a promising way to improve the delineation of the target volumes. In this paper, we report data on accuracy, reproducibility and consistency of an interactive coregistration procedure in a specifically designed phantom and in a group of patients with primary head and neck tumors. PATIENTS AND METHODS: A phantom and a group of four patients with pharyngo-laryngeal tumors were imaged by CT scan (taken as the reference image), MRI (T1- and T2-weighed sequences) and PET (transmission and FDG emission). Sets of images were coregistered using an interactive rigid coregistration method based on interactive surface segmentation. Translational and rotational displacements relative to the reference CT scan were measured and expressed in terms of accuracy, reproducibility (inter- and intra-observer variation) and consistency (between T1- and T2-weighed MRI). RESULTS: Coregistration accuracy was in the range of 0.8-6.2 mm and 1.2-4.6 mm for the phantom and the patients, respectively. Accuracy was slightly worse in the z direction, and was significantly correlated with the spatial resolution of the imaging modalities, at least for the phantom. Inter- and intra-observer variations were very small and always far below the residual variance. Consistency was perfect except in the y direction. CONCLUSION: Providing adequate set-up is chosen, accurate coregistration of CT, MR and FDG-PET images can be obtained in the head and neck area. Coregistration was consistent and highly reproducible among observers.

Head and Neck Neoplasms↗
PubMed2005

Multimodality treatment of esophageal cancer.

Stage specific management of non-small cell lung cancer is widely accepted. The use of pretreatment disease stage to guide therapy for esophageal cancer is an intellectually appealing concept. To date, there isa relative lack of data upon which one may base stage specific treatment decisions for esophageal carcinoma. This is because thorough pretreatment TNM staging is not universally practiced. As a result, stage-specific treatment varies widely. Based upon the available data, surgery alone may be appropriate for resectable, node-negative disease. In the case of clearly un-resectable disease, definitive chemoradiation is indicated.The value of neoadjuvant or adjuvant treatment modalities in the case of clearly resectable node-negative disease (TlN0 or T2N0) is questionable;however, in the presence of lymph node involvement (N1), or in the case of a marginally resectable primary tumor (T3 or T4), neoadjuvant chemoradiation is probably indicated. Although the achievement ofa complete pathologic response following chemoradiation may obviate surgical resection, even microscopic residual cancer can result in local recurrence. To date, there is no reliable method of ascertaining a complete pathologic response before surgical resection. Therefore, when feasible, the addition of surgical resection following chemoradiation is warranted. Future treatment trials for esophageal cancer should include rigorous pretreatment staging protocols to elucidate stage-specific results of therapy.

Combined Modality Therapy↗
PubMed2004

Multimodality therapy in mesothelioma: role of chemotherapy.

The few long-term survivors of MPM have been cured with radical surgical extirpation often followed by radiation therapy and adjuvant chemotherapy. The combination of pemetrexed and cisplatin recently was shown to improve survival over treatment with cisplatin alone. Given the size and robustness of that trial, the combination should be the new standard treatment for this cancer. Combined modality approaches to therapy, including surgery, radiation, and chemotherapy, are becoming the standard of care in patients with resectable mesothelioma. Two phase II studies have demonstrated that neoadjuvant chemotherapy is safe and apparently effective. A third phase II trial will use the combination of pemetrexed plus cisplatin preoperatively followed by surgery and radiation for patients with T1-3 N0-2 mesothelioma. If the statistical analysis of this study shows a measurable pathologic complete response rate and a median survival that exceeds the current expected value of 20 to 24 months, a phase III trial comparing surgery and radiation to surgery, radiation, and chemotherapy will be considered.

Antineoplastic Agents↗
PubMed2006

Development of an advanced multimode automatic ultrasonic texture measurement system for laboratory and production line application.

We present work on the development of an ultrasonic texture measurement system for sheet metals using non-contact transducers, suitable for use both in the laboratory and on the production line. Variation of the velocity of the zero-order symmetric (S0) Lamb wave is used to determine the crystallographic texture of polycrystalline metal sheets ranging in thickness from 0.1 to 3 mm. This system features improvements on previous state-of-the-art ultrasonic technology in that it probes velocity over a continuous range of angles using only two electromagnetic acoustic transducers (EMATs). This is demonstrated to offer a significant improvement in accuracy and allows the detection and investigation of asymmetric anisotropies in the sheets. Another advantage of the system is its potential for combining several different measurements using a single pair of transducers. The capability is demonstrated for through-thickness shear wave measurements as well as the zero-order symmetric Lamb wave measurements which are the primary means of determining the texture. The change between generating Lamb and through-thickness bulk waves can be made entirely by changing the electrical circuit connected to the EMATs without modifying the transducer assembly in any way. Measurement of all of the above waves can provide information on the sheet thickness and other physical properties of the sheet in addition to texture. Certain texture parameters can be calculated from both Lamb and shear wave velocities, allowing self-calibration of the system.

Electromagnetic Phenomena↗
PubMed2006

Identification and analysis of multimode guided waves in tibia cortical bone.

The hollow cylinder model filled with viscous-liquid is performed to simulate tibial bone shape in this paper. Short time Fourier transform (STFT) was applied to identify and analyze guided wave modes of a series of ultrasonic signals acquired at various transmitter-receiver positions for a fixed transmitter. Experimental results were compared with theoretical simulation. The high correlation values for group velocity were obtained between results of experiment and theory for L(0,2) (r=0.89, p<10(-5)), and L(0,3) (r=0.87, p<10(-5)). The experimental group velocities correlated strongly with cortical thickness (cortTh) for L(0,2) (r(2)=0.79, p<10(-5)) and L(0,3) (r(2)=0.74, p<10(-5)) at 0.5 MHz center frequency. The results showed that the STFT is an effective method to identify the propagating modes and derive dispersion information. The experimental results were in good agreement with theoretical predictions. This study suggests that the guided wave L(0,2) mode is a promising mode to assess change in cortical thickness.

Algorithms↗
PubMed1998

Phasic flow events at the aortic isthmus-ductus arteriosus junction and branch pulmonary artery evaluated by multimodal ultrasonography in fetal lambs.

OBJECTIVES: We assessed the phasic flow and interaction between the pulmonary trunk and aortic isthmus flow at their junction in the lamb fetus in late gestation and also assessed the interaction of the left pulmonary artery branch. STUDY DESIGN: With echocardiographic and Doppler ultrasonographic and saline-contrast techniques, we studied 7 fetal lambs with arterial and venous catheters in place to assess direction, velocity, and timing of flow at the aortic isthmus, ductus arteriosus, and proximal left pulmonary artery. RESULTS: At the isthmus-ductus junction, ductus systolic flow occurred later (0.048 +/- 0.006 second, mean +/- SD) and accelerated more slowly than isthmus flow but with higher velocities (peak 70.7 +/- 7.1 vs 63.1 +/- 6.3 cm/s, velocity time integral 5.7 +/- 1.2 vs 4.5 +/- 1.3 cm, respectively; P <.001). There was a small degree of late systolic flow reversal and admixture from both sources. Signals from the left pulmonary arterial branch showed a sharp, brief systolic forward flow with a peak velocity of 48.8 +/- 9.1 cm/s, followed by late systolic and diastolic flow reversal with a peak velocity of 23.5 +/- 8.7 cm/s. CONCLUSION: The differences in the flow timing may be the result of different timing of ventricular contraction, resistances in the vascular beds, and ductus constriction, both anatomic and physiologic.

Animals↗