1,723 research outputs found
Development of a Compact Piezoworm Actuator For Mr Guided Medical Procedures
In this research, a novel piezoelectric actuator was developed to operate safely inside the magnetic resonance imaging (MRI) machine. The actuator based on novel design that generates linear and rotary motion simultaneously for higher needle insertion accuracy. One of the research main objectives is to aid in the selection of suitable materials for actuators used in this challenging environment. Usually only nonmagnetic materials are used in this extremely high magnetic environment. These materials are classified as MRI compatible materials and are selected to avoid hazardous conditions and image quality degradation. But unfortunately many inert materials to the magnetic field do not possess desirable mechanical properties in terms of hardness, stiffness and strength and much of the available data for MRI compatible materials are scattered throughout the literature and often too device specific . Furthermore, the fact that significant heating is experienced by some of these devices due to the scanner’s variable magnetic fields makes it difficult to draw general conclusions to support the choice of suitable material and typically these choices are based on a trial-and-error with extensive time required for prototype development and MRI testing of such devices.
This research provides a quantitative comparison of several engineering materials in the MRI environment and comparison to theoretical behavior which should aid designers/engineers to estimate the MRI compatible material performance before the expensive step of construction and testing. This work focuses specifically on the effects in the MRI due to the material susceptibility, namely forces, torques, image artifacts and induced heating
Advancements and Breakthroughs in Ultrasound Imaging
Ultrasonic imaging is a powerful diagnostic tool available to medical practitioners, engineers and researchers today. Due to the relative safety, and the non-invasive nature, ultrasonic imaging has become one of the most rapidly advancing technologies. These rapid advances are directly related to the parallel advancements in electronics, computing, and transducer technology together with sophisticated signal processing techniques. This book focuses on state of the art developments in ultrasonic imaging applications and underlying technologies presented by leading practitioners and researchers from many parts of the world
Aerospace medicine and biology: A continuing bibliography with indexes (supplement 335)
This bibliography lists 143 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during March, 1990. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance
Computer- and robot-assisted Medical Intervention
Medical robotics includes assistive devices used by the physician in order to
make his/her diagnostic or therapeutic practices easier and more efficient.
This chapter focuses on such systems. It introduces the general field of
Computer-Assisted Medical Interventions, its aims, its different components and
describes the place of robots in that context. The evolutions in terms of
general design and control paradigms in the development of medical robots are
presented and issues specific to that application domain are discussed. A view
of existing systems, on-going developments and future trends is given. A
case-study is detailed. Other types of robotic help in the medical environment
(such as for assisting a handicapped person, for rehabilitation of a patient or
for replacement of some damaged/suppressed limbs or organs) are out of the
scope of this chapter.Comment: Handbook of Automation, Shimon Nof (Ed.) (2009) 000-00
Transcranial photoacoustic computed tomography based on a layered back-projection method
A major challenge of transcranial human brain photoacoustic computed tomography (PACT) is correcting for the acoustic aberration induced by the skull. Here, we present a modified universal back-projection (UBP) method, termed layered UBP (L-UBP), that can de-aberrate the transcranial PA signals by accommodating the skull heterogeneity into conventional UBP. In L-UBP, the acoustic medium is divided into multiple layers: the acoustic coupling fluid layer between the skull and detectors, the skull layer, and the brain tissue layer, which are assigned different acoustic properties. The transmission coefficients and wave conversion are considered at the fluid–skull and skull–tissue interfaces. Simulations of transcranial PACT using L-UBP were conducted to validate the method. Ex vivo experiments with a newly developed three-dimensional PACT system with 1-MHz center frequency demonstrated that L-UBP can substantially improve the image quality compared to conventional UBP
Ferroelastic-switching-driven colossal shear strain and piezoelectricity in a hybrid ferroelectric
Materials that can produce large controllable strains are widely used in
shape memory devices, actuators and sensors. Great efforts have been made to
improve the strain outputs of various material systems. Among them,
ferroelastic transitions underpin giant reversible strains in
electrically-driven ferro/piezoelectrics and thermally- or magneticallydriven
shape memory alloys. However, large-strain ferroelastic switching in
conventional ferroelectrics is very challenging while magnetic and thermal
controls are not desirable for applications. Here, we demonstrate an
unprecedentedly large shear strain up to 21.5 % in a hybrid ferroelectric,
C6H5N(CH3)3CdCl3. The strain response is about two orders of magnitude higher
than those of top-performing conventional ferroelectric polymers and oxides. It
is achieved via inorganic bond switching and facilitated by the structural
confinement of the large organic moieties, which prevents the undesired
180-degree polarization switching. Furthermore, Br substitution can effectively
soften the bonds and result in giant shear piezoelectric coefficient (d35 ~
4800 pm/V) in Br-rich end of the solid solution, C6H5N(CH3)3CdBr3xCl3(1-x). The
superior electromechanical properties of the compounds promise their potential
in lightweight and high energy density devices, and the strategy described here
should inspire the development of next-generation piezoelectrics and
electroactive materials based on hybrid ferroelectrics.Comment: 32 pages, 14 figures, 5 table
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