54 results about "Power deposition" patented technology

A magnetic resonance imaging “MRI” method and apparatus for lengthening the usable echo-train duration and reducing the power deposition for imaging is provided. The method explicitly considers the t1 and t2 relaxation times for the tissues of interest, and permits the desired image contrast to be incorporated into the tissue signal evolutions corresponding to the long echo train. The method provides a means to shorten image acquisition times and / or increase spatial resolution for widely-used spin-echo train magnetic resonance techniques, and enables high-field imaging within the safety guidelines established by the Food and Drug Administration for power deposition in human MRI.

An electrosurgical system and method for performing an electrosurgical procedure are disclosed. The electrosurgical system includes a high frequency generator to supply energy, the generator including one or more electrical connections. The system also includes one or more instruments configured to be inserted into tissue of the patient's body having a hardened tissue volume. The instruments are configured to penetrate the hardened tissue volume to create at one or more orifices defined therein. The instruments are also configured to selectively encapsulate one or more active electrodes that are coupled to the electrical connections. Each of the electrodes has an elongated shaft terminating in an exposed, conductive tip. The electrodes are configured to be inserted into the tissue of the patient's body and into the hardened tissue volume through the orifices to subsequently apply energy from the high frequency generator to the exposed, conductive tip to induce a coherent heating effect in the hardened tissue volume from power deposition therein, thereby producing a heat ablation volume in the hardened tissue volume.

A method for calculating a flip angle schedule for a train of refocusing radio frequency (RF) pulses with reduced flip angles allows control of RF power deposition and use of a longer echo train. A target signal is defined for each echo in the echo train, and flip angles are then calculated from the target signals. The target signal schedule includes two phases. In the first phase, the target signals drop asymptotically to efficiently establish a pseudo-steady state at a pre-defined minimum signal level, Smin. In the second phase, the target signal is increased monotonically for the remainder of the train to a pre-defined maximum signal level, Smax. By increasing the target signal, the effect of relaxation may be reduced, decreasing blurring and ringing artifacts. Flip angles are then calculated from the target signal schedule, using a simplified method that requires no information about the tissues' relaxation properties.

A system composed of multiple transmit coils with corresponding RF pulse synthesizers and amplifiers is disclosed. A method of designing RF pulses specific to each transmit coil to dynamically control RF power deposition across an imaging volume is also disclosed, where parallel excitation with the transmit coils allows for management of RF power deposition on a subject while facilitating faithful production of a desired excitation profile. The present invention also supports reduction in scan time and is applicable to any coil array geometry.

Systems and methods for controlling a magnetic resonance imaging system are provided. In one embodiment, a magnetic resonance imaging system includes a radio frequency coil with a plurality of conductive coil elements, control circuitry that determines, based at least in part on a measurement of scattering parameters, a plurality of forward voltages that will cause power deposition into an object within a predetermined specific absorption rate, and an amplifier configured to apply the determined plurality of forward voltages respectively to the plurality of coil elements. The control circuitry may determine the plurality of forward voltages based at least in part on an unloaded measurement of scattering parameters and a loaded measurement of scattering parameters.

The invention relates to a low-temperature vapor deposition method for a carbon-based super-lubricating thin film with an onion structure. The method comprises the following steps of (1) carrying out ultrasonic cleaning on silicon substrate by using acetone and absolute ethyl alcohol, and transferring the silicon substrate to a coating cavity; (2) vacuumizing until the vacuum degree is smaller than 4.0*10<-3> Pa; (3) cleaning under the following conditions: introducing Ar until the air pressure is 2-3 Pa, applying a negative bias voltage of -1000 to -1200 V to the silicon substrate to carry out plasma glow cleaning for 10 min; and (4) depositing the carbon-based super-lubricating thin film with the onion structure, namely keeping the bias voltage at -500 to -1000 V, the frequency at 3.5 KHz and the duty ratio at 15-25%; and keeping the air flow of Ar at 80-200sccm, the CH4 flow at 40-50sccm, the air pressure at 0.45-0.5 Pa, the target power at 800-900 W, the deposition time within 1 h and the deposited thin film thickness at about 1 mu m in the deposition process. The carbon-based super-lubricating thin film with the onion structure, prepared by using the low-temperature vapor deposition method, has the advantages of high hardness, excellent chemical inertness, low frictional coefficient, good wear resistance and the like.

A half-volume quadrature TEM coil high field (>3 T) imaging applications. This novel coil produces a sufficiently large homogeneous B1 field region for the use as a volume coil. It provides superior transmission efficiency, resulting in significantly lower power deposition, as well as greater sensitivity and improved patient comfort and accessibility compared with conventional full-volume coils. Additionally this coil compensates the RF penetration artifact that distorts high-field images recorded with linear surface and volume coils. These advantages make it potentially possible to apply the device as an efficient transmit / receive body coil at high fields, where the use of the full-volume coils is complicated by the excessive power deposition and low sensitivity.

An apparatus for exposing a region of interest of an object, animal or person to an alternating magnetic field has a source of radio-frequency electromagnetic radiation arranged to provide the alternating magnetic field in an exposure volume defined by the apparatus, and a shield arranged between the source of radio-frequency electromagnetic radiation and the exposure volume. The shield includes a material that has a sufficient thickness and arrangement to reduce power deposition to at least regions outside of the region of interest of the object, animal or person during exposure in the exposure volume.

Featured is a dosimeter device that measures SAR deposited by RF power deposition during MRI of a specimen. Such a dosimeter device includes a transducer that is configured to present a load to the MRI scanner in which the transducer is located and to provide an output representative of signals induced in the transducer. The transducer also is configured so that the presented load is substantially equivalent to another load which would be presented by the specimen during MRI of the specimen. Such a transducer also is configured so as to generate an MRI signal that is sufficient to allow the MRI scanner to adjust the RF power to a value substantially equal to that of the specimen. Also featured are methods for measuring SAR deposited by RF power deposition and apparatuses or system embodying such a dosimeter device.

The present invention describes a magnetic resonance imaging method wherein spatially resolved frequency sensitive image data are collected by means of free precession sequences employing very small radio frequency (RF) excitation pulses per unit time which result in highly frequency selective steady-state signals dominated by linear properties of the system, for which the superposition principle holds. By appropriate linear combination of steady state signals of N different frequencies, N resonance lines can be acquired simultaneously. This method allows spectroscopic recordings with very low RF power deposition which renders the method suitable for applications at high static magnetic field strengths.

Methods for forming a photovoltaic device include adjusting a deposition power for depositing a buffer layer including germanium on a transparent electrode. The deposition power is configured to improve device efficiency. A p-type layer is formed on the buffer layer. An intrinsic layer and an n-type layer are formed over the p-type layer.