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Head Motion (head + motion)

Distribution by Scientific Domains
Medical Sciences66%

Selected Abstracts

Natural head motion synthesis driven by acoustic prosodic features

COMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2005
Carlos Busso
Abstract Natural head motion is important to realistic facial animation and engaging human,computer interactions. In this paper, we present a novel data-driven approach to synthesize appropriate head motion by sampling from trained hidden markov models (HMMs). First, while an actress recited a corpus specifically designed to elicit various emotions, her 3D head motion was captured and further processed to construct a head motion database that included synchronized speech information. Then, an HMM for each discrete head motion representation (derived directly from data using vector quantization) was created by using acoustic prosodic features derived from speech. Finally, first-order Markov models and interpolation techniques were used to smooth the synthesized sequence. Our comparison experiments and novel synthesis results show that synthesized head motions follow the temporal dynamic behavior of real human subjects. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Prospective real-time correction for arbitrary head motion using active markers

MAGNETIC RESONANCE IN MEDICINE, Issue 4 2009
Melvyn B. Ooi
Abstract Patient motion during an MRI exam can result in major degradation of image quality, and is of increasing concern due to the aging population and its associated diseases. This work presents a general strategy for real-time, intraimage compensation of rigid-body motion that is compatible with multiple imaging sequences. Image quality improvements are established for structural brain MRI acquired during volunteer motion. A headband integrated with three active markers is secured to the forehead. Prospective correction is achieved by interleaving a rapid track-and-update module into the imaging sequence. For every repetition of this module, a short tracking pulse-sequence remeasures the marker positions; during head motion, the rigid-body transformation that realigns the markers to their initial positions is fed back to adaptively update the image-plane,maintaining it at a fixed orientation relative to the head,before the next imaging segment of k -space is acquired. In cases of extreme motion, corrupted lines of k -space are rejected and reacquired with the updated geometry. High-precision tracking measurements (0.01 mm) and corrections are accomplished in a temporal resolution (37 ms) suitable for real-time application. The correction package requires minimal additional hardware and is fully integrated into the standard user interface, promoting transferability to clinical practice. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source]

Artifact due to B0 fluctuations in fMRI: Correction using the k- space central line

MAGNETIC RESONANCE IN MEDICINE, Issue 1 2001
Emmanuel Durand
Abstract Magnetic resonance experiments require the main magnetic field, B0, to remain very stable. Several external sources, such as moving ferromagnetic objects and/or changing electromagnetic fields, can significantly change the value of B0 over time. This work describes an apparent displacement along the phase-encoding axis caused by a variation in B0. This artifact was observed in fMRI images acquired with EPI. The effect was characterized and tested using an immobile phantom. The image displacement motion along the phase-encoding axis closely followed the changes in B0. The phase of the central line in the Fourier space was successfully used to correct this artifact. Fluctuations in B0 may result in artifacts that mimic subject head motion, and must be appropriately corrected. Magn Reson Med 46:198,201, 2001. © 2001 Wiley-Liss, Inc. [source]

Abnormal vestibular responses to vertical head motion in cerebellar ataxia

ANNALS OF NEUROLOGY, Issue 2 2008
Ke Liao MS
Falls pose an important problem to neurologists caring for patients with cerebellar disorders. Normal human gait is characterized by prominent up-and-down linear head movements (vertical translations). Thus, we asked whether patients with cerebellar gait ataxia showed abnormal responses of otolithic vestibuloocular reflexes to this motion. Compared with healthy subjects, all cerebellar patients showed impaired otolith-ocular responses. Neurologists often test the rotational vestibuloocular reflexes in cerebellar patients, but our results indicate that vestibular responses to vertical linear motion are severely affected. Impairment of the corresponding otolith-spinal reflexes may contribute substantially to falls. Ann Neurol 2008 [source]

Natural head motion synthesis driven by acoustic prosodic features

COMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2005
Carlos Busso
Abstract Natural head motion is important to realistic facial animation and engaging human,computer interactions. In this paper, we present a novel data-driven approach to synthesize appropriate head motion by sampling from trained hidden markov models (HMMs). First, while an actress recited a corpus specifically designed to elicit various emotions, her 3D head motion was captured and further processed to construct a head motion database that included synchronized speech information. Then, an HMM for each discrete head motion representation (derived directly from data using vector quantization) was created by using acoustic prosodic features derived from speech. Finally, first-order Markov models and interpolation techniques were used to smooth the synthesized sequence. Our comparison experiments and novel synthesis results show that synthesized head motions follow the temporal dynamic behavior of real human subjects. Copyright © 2005 John Wiley & Sons, Ltd. [source]