196,133 research outputs found
Measurement of the weighted peak level for occupational exposure to gradient magnetic fields for 1.5 and 3 tesla mri body scanners
No full textThe purpose of this work is to give a contribution to the construction of a comprehensive knowledge of the exposure levels to gradient magnetic fields (GMF) in terms of the weighed peak (WP), especially for 3 Tesla scanners for which there are still few works available in the literature. A new generation probe for the measurement of electromagnetic fields in the range of 1 Hz-400 kHz was used to assess the occupational exposure levels to the GMF for 1.5 and 3.0 Tesla MRI body scanners, using the method of the WP according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) approach. The probe was placed at a height of 1.1 m, close to the MRI scanners, where operators could stay during some medical procedures with particular issues. The measurements were performed for a set of typical acquisition sequences for body (liver) and head exams. The measured values of WP were in compliance with ICNIRP 2010 reference levels for occupational exposures
Relation Between Reading Performance and White-Matter Alteration and Reorganization in Neurosurgical Patients
No full textReading abilities and diffusion tensor imaging (DTI) parameters were retrospectively analyzed in a group of neurosurgical patients to investigate (Study 1) the role of white matter-in particular the arcuate fasciculus (AF)-in preserved vs. impaired reading; 4 months after surgery, we explored the plasticity processes (Study 2). Study 1 involved 40 patients with brain glioma (23 low-grade and 17 high-grade gliomas). We compared preoperative DTI parameters of language-related fascicles between patients who developed a reading impairment after surgery (n = 23) and patients with preserved reading (n = 17). Besides lower fractional anisotropy (FA), patients with impaired reading also displayed lower number and density of streamlines of a direct (i.e., directly connecting temporal and frontal lobes) AF segment. In Study 2, we longitudinally tested at follow-up-when reading performance had generally improved-13 patients diagnosed with low-grade glioma. The most relevant finding was a significant increase in length of streamlines of the direct AF segments in both hemispheres. From a neurosurgical perspective, our preliminary findings suggest the clinical importance of sparing direct AF segments for the involvement they showed in reading; however, the results also suggest the reorganization potential of these segments, possibly compensating of the right homologs as well
Understanding Body Language Does Not Require Matching the Body's Egocentric Map to Body Posture: A Brain Activation fMRI Study
No full textBody language (BL) is a type of nonverbal communication in which the body communicates the message. We contrasted participants' cognitive processing of body representations or meanings versus body positions. Participants (N = 20) were shown pictures depicting body postures and were instructed to focus on their meaning (BL) or on the position of a body part relative to the position of another part (body structural description [BSD]). We examined activation in brain areas related to the two types of body representation—body schema and BSD—as modulated by the two tasks. We presumed that if understanding BL triggers embodiment of body posture, a matching procedure between the egocentric map coding the position of one's body segments in space and time should occur. We found that BL (vs. BSD) differentially activated the angular gyrus bilaterally, the anterior middle temporal gyrus, the temporal pole, and the right superior temporal gyrus, the inferior frontal gyrus, the superior medial gyrus, and the left superior frontal gyrus. BSD (vs. BL) differentially activated the superior parietal lobule (Area 7A) bilaterally, the posterior inferior temporal gyrus, the middle frontal gyrus, and the left precentral gyrus. Sensorimotor areas were differentially activated by BSD when compared with BL. Inclusive masking showed significant voxels in the superior colliculus and pulvinar, fusiform gyrus, inferior temporal gyrus, superior temporal gyrus, the intraparietal sulcus bilaterally, inferior frontal gyrus bilaterally, and precentral gyrus. These results indicate common brain networks for processing BL and BSD, for which some areas show differentially stronger or weaker processing of one task or the other, with the precuneus and the superior parietal lobule, the intraparietal sulcus, and sensorimotor areas most related to the BSD as activated by the BSD task. In contrast, the parietal operculum, an area related to the body schema, a representation crucial during embodiment of body postures, was not activated for implicit masking or for the differential contrasts
Anticipatory simulation of implied actions in the human motor system
No full textMemory for the final position or configuration of amoving object is distorted forward along its actual or implied path of motion representational momentum). This may allow humans to anticipate the forthcoming position of moving objects or creatures. By using single-pulse transcranial magnetic stimulation (TMS), we tested whether mirror motor facilitation is higher during extrapolation of dynamic information about forward than backward action paths. The results show that motor facilitation is specific for the observation of snapshots evoking ongoing but incomplete actions. This suggests that the motor cortico-spinal component of the observation-execution matching system is preferentially activated by the inner anticipatory simulation of the deployment of an action in the future
What do we know about intratumoral functional activity: a scoping review of imaging and intra-surgery results
No full textIntratumoral functional tissue represent a challenge in neurosurgery, as its resection may induce a permanent postoperative deficit. Only little is said in literature about this pattern. Currently this issue is receiving increased attention and in the last few years, the number of reports on intratumor functionality has increased. Aim of the current review was to provide a comprehensive overview of intratumoral area functionality patterns and of how much frequently this pattern is reported. PRISMA guidelines were followed. We identified 107 papers, but only 24 articles on 1220 patients were included for having reported intratumoral activation data. Within this framework, we aimed to shed light on some issues, including whether i) it is expressed only as fMRI activation within the mass, or whether it impacts on distant areas via functional connectivity, ii) it is found in slow growing tumors such as low grade glioma or also for fast infiltrative processes such as for high grade glioma, and iii) inhomogeneity of the tumor structure and morphological appearance or the tumor histology are key factors determining intratumoral area functionality. Key methods suitable for detecting intratumour function included MEG (in 7 studies), resting-state fMRI and task-active fMRI (in 8 studies) and intra-surgery direct cortical stimulation (in 8 studies). The type of patients were patients with astrocytoma (321 cases) and oligodendroglioma (255 cases) with tumor grade II (252 cases) and isocitrate dehydrogenase (IDH) mutation. Their mean tumor volume was 53.11 ± 19.23, and the affected hemisphere was mainly the left one (895 cases); lesion site most frequently involved the frontal cortex (435 cases). We discussed the clinical implications of these aspects, as a functional intratumoral area has a high impact on both planning and outcome, and we addressed the role of intra-surgery cognitive monitoring that should encompass a wide variety of functions
Effective nucleon-nucleon interaction and low-lying nuclear magnetic statesContribution to the XII workshop on problems in Theoretical Physics
No full textSimulating the Future of Actions in the Human Corticospinal System
No full textPerception of the final position of a moving object or creature is distorted forward along its actual or implied motion path, thus enabling anticipation of its forthcoming position. In a previous research, we demonstrated that viewing static snapshots that imply body actions activates the human motor system. What remains unknown, however, is whether extrapolation of dynamic information and motor activation are higher for upcoming than past action phases. By using single-pulse transcranial magnetic stimulation, we found that observation of start and middle phases of grasp and flick actions engendered a significantly higher motor facilitation than observing their final postures. Differential motor facilitation during start and end postures was independent of finger configuration at the different hand apertures. Subjective ratings showed that modulation of motor facilitation was not due to the amount of implied motion per se but to the forward direction of the motion path toward upcoming phases. Thus, motor facilitation proved maximal for the snapshots evoking ongoing but incomplete actions. The results provide compelling evidence that the frontal component of the observation-execution matching system is preferentially activated by the anticipatory simulation of future action phases and thus plays an important role in the predictive coding of others' motor behaviors
Effects of inhomogeneous radiofrequency power depositino on the apparent diffusion coefficient of the normal breast at 3.0 T.
No full textNormal-appearing naming-related functional activation in incidentally discovered lowgrade gliomas: a single institution study
No full textBackground: Incidentally discovered low-grade gliomas (iLGGs) represent a rare neurological condition, which is associated with a good clinical status and usually preserved - or borderline - cognitive functions; only recently, knowledge has increased on their development and clinical features. Better understanding these aspects is fundamental to set up the most appropriate clinical protocol.
Methods: We used fMRI to conduct an exploratory investigation of the effects of iLGG growth on the brain and the potential occurrence of early rearrangement in the functional network associated with object naming. We compared this group of 13 patients with an iLGG in the left hemisphere (maximum lesion overlap in the left inferior frontal gyrus and median tumor volume 12 cm3) and with preserved naming skills with that of a healthy control group.
Results: No significant differences were observed in the functional activations between the two groups, but a cluster in the controls vs. patients contrast mainly located in the right lateral visual cortex. As this region is unspecific for object naming and no significant changes emerged in the affected hemisphere nor in naming-specific homologues of the contralesional hemisphere, we concluded that iLGG growth did not affect the functional network and plasticity-related reorganization did not occur yet. We attributed this finding to iLGG features, such as small tumor size at the diagnosis and lack or minimal infiltration.
Conclusions: These findings are preliminary and we recommend future investigation to replicate them and test generalizability to other functional networks. Understanding the potential functional effects of iLGG growth is fundamental for the choice of the most appropriate treatment
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