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Inertial Enhancement to Mechanical Isolation of MR Gradient Coils

IP.com Disclosure Number: IPCOM000012217D
Publication Date: 2003-Apr-17
Document File: 2 page(s) / 95K

Publishing Venue

The IP.com Prior Art Database

Abstract

Magnetic Resonance Imagers employ electrically excited coils to impose time varying magnetic fields on the larger, steady primary field provided by the main magnet. Since the imposed currents exist within a magnetic field, they produce corresponding forces on the conductors, which result in dynamic motions that propagate throughout the scanner. Repetitive pulses impart vibrational energy within the audio frequency range, resulting in pronounced acoustic noise. Those vibrations also transmit and propagate throughout the building site where they can emerge as noise sources in other rooms. In the MR suite, acoustic noise causes discomfort to the patient and operator and interferes with communication. Beyond the MR suite, acoustic noise can also interfere with clinical procedures, such as listening for irregularities in a patient's heart. This invention adds significant inertia to the coil support so that its motion is reduced, with respect to the gradient coil, without increasing the rigid body motion of the coil. This will reduce the acoustic emissions from the enclosure as well as structure-borne transmission through the cryostat into the floor and then into the site building structure.

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FIELD OF TECHNOLOGY: 

Magnetic Resonance Imaging (MRI)

INVENTION TITLE: 

Inertial Enhancement to Mechanical Isolation of MRI Gradient Coils

PROBLEM/BACKGROUND: 

Magnetic Resonance Imagers employ electrically excited coils to impose time varying magnetic fields on the larger, steady primary field provided by the main magnet. Since the imposed currents exist within a magnetic field, they produce corresponding forces on the conductors, which result in dynamic motions that propagate throughout the scanner. Since typical current waveforms contain repetitive pulses with fast transitions, they impart vibrational energy within the audio frequency range and in turn radiate sound pressure waves at solid to air interfaces, resulting in pronounced acoustic noise. Those vibrations also transmit through the cryostat into the floor and then propagate throughout the building site where they can emerge as noise sources in other rooms. In the MR suite, acoustic noise causes discomfort to the patient and operator and interferes with communication. Beyond the MR suite, acoustic noise causes irritation but can also interfere with clinical procedures, such as listening for irregularities in a patient’s heart. Finally, very high-speed scans in high field magnets can generate noise levels beyond acceptable exposure levels. Prior attempts at noise reduction almost always depend upon vibration isolation of the gradient coil in order to attenuate the motions and the acoustic emissions. However, classical isolation methods often lead to increased rigid body motion of the coil and/or cryostat, which has an adverse effect on image quality. This invention would improve the mechanical isolation of the gradient coil without increas...