Abstract: A pressure compensation assembly for a drill bit having a cavity to receive the pressure compensation assembly, a mud port connected to the cavity, and a lubricant passageway connected to the cavity, is disclosed. The pressure compensation assembly includes a relief mechanism having a selected operating pressure. The pressure compensation assembly is movable from a first position to a second position within the cavity. The pressure compensation assembly may receive lubricant at a pressure exceeding the selected operating pressure to permit the flow of lubricant into the lubricant passageway while substantially preventing the release of lubricant into the mud port while in the first position. The pressure compensation assembly is operable to limit a pressure differential within the drill bit while in the second position.

Abstract: A compound bow, recurve bow, long bow, or crossbow with two idler pulleys that allow for a faster decrease in bowstring angle in relation to the arrow thereby increasing the amount of stored energy during the draw stroke and decreasing the distance required to reach peak draw weight. The two idler pulleys also allow the force draw curve to be designed around the human body kinematic strengths as opposed to the limitations of the bow geometry.

Abstract: A valve system for use in a subterranean well, the valve having multiple closure devices, or a closure device and a device for protecting the closure device. A valve system includes a valve with a closure assembly. The closure assembly has a closure device and a protective device which alters fluid flow through a flow passage of the valve prior to closure of the closure device to thereby protect the closure device. A safety valve system includes a safety valve with a closure assembly having at least two closure devices arranged in series for controlling flow through a flow passage of the safety valve. Another safety valve system includes a safety valve assembly including multiple safety valves arranged in parallel. One portion of fluid from a fluid source flows through one of the safety valves, while another portion of fluid from the fluid source flows through another safety valve.

Abstract: A pressure compensation assembly for a drill bit having a cavity to receive the pressure compensation assembly, a mud port connected to the cavity, and a lubricant passageway connected to the cavity, is disclosed. The pressure compensation assembly includes a relief mechanism having a selected operating pressure. The pressure compensation assembly is movable from a first position to a second position within the cavity. The pressure compensation assembly may receive lubricant at a pressure exceeding the selected operating pressure to permit the flow of lubricant into the lubricant passageway while substantially preventing the release of lubricant into the mud port while in the first position. The pressure compensation assembly is operable to limit a pressure differential within the drill bit while in the second position.

Abstract: An insert for an earth boring drill bit, such as a PDC rock bit or a roller cone rock bit, is provided. The insert includes a base integrally joined to a top section, the top section having a first flank that curves in a substantially helical manner about a longitudinal axis of the insert to join a crest.

Abstract: A system and method for decoupling coils in a medical imaging system are provided. The coil system includes a first coil of a medical imaging system, a second coil of the medical imaging system, and a balun device connected to the first and second coils. The balun device is configured to decouple the first and second coils of the medical imaging system.

Abstract: A detuning circuit for an MRI coil having a series tuning capacitor includes: a detuning inductor and a PIN diode in parallel communication with the tuning capacitor, where the tuning capacitor has a tuning inductor node and a PIN diode node; a first diode and a second diode in parallel communication with the PIN diode, where the first, second and PIN diodes are arranged with the same serial polarity and the first and second diodes have a common node; and a reactance in communication between the common node and the tuning inductor node. The circuit detunes the MRI coil in response to an MRI transmit pulse. A detuning circuit for an MRI coil having a series tuning capacitor includes a detuning inductor; and a detuning switch in parallel combination with a secondary tuning capacitor, the detuning inductor and the parallel combination being in parallel communication with the series tuning capacitor. The secondary tuning capacitor acts to reduce current during detuning of the MRI coil.

Abstract: A system and method for decoupling coils in a medical imaging system are provided. The coil system includes a first coil of a medical imaging system, a second coil of the medical imaging system, and a balun device connected to the first and second coils. The balun device is configured to decouple the first and second coils of the medical imaging system.

Abstract: A multi-channel RF cable trap (70) blocks stray RF current from flowing on shield conductors (114) of coaxial RF cables (60) of a magnetic resonance apparatus. An inductor (116) is formed by a curved semi-rigid trough (80) constructed of an insulating material coated with an electrically conducting layer. Preferably, the inductor (116) and the cable follow an “S”-shaped path to facilitate good electromagnetic coupling therebetween. The RF cables (60) are laid in the trough (80) and the shield conductors inductively couple with the inductor (116). A capacitor (82) and optional trim capacitor (83) are connected across the the trough of the inductor (116) to form a resonant LC circuit tuned to the resonance frequency. The LC circuit inductively couples with the shield conductors (114) to present a high, signal attenuating impedance at the resonance frequency. The resonant circuit is preferably contained in an RF-shielding box (84) with removable lid.

Abstract: An RF coil construction (40, 40′) includes removable, relocatable, and/or detachable sections (42, 44) that are inherently decoupled. The sections can be relocated, removed, or exchanged with sections having different coil sizes or coil configurations, allowing the coil configuration to be tailored to a desired imaging procedure and region of the brain. The coil construction provides space for stimulation devices and adjusting patient access and comfort. Since the operator can select coil removal or placement to reduce the amount of data outside the region of interest, the coil construction can also reduce scanning and reconstruction time, reduce artifacts, and provide increased temporal resolution and image throughput.

Abstract: A multi-channel RF cable trap (70) blocks stray RF current from flowing on shield conductors (114) of coaxial RF cables (60) of a magnetic resonance apparatus. An inductor (116) is formed by a curved semi-rigid trough (80) constructed of an insulating material coated with an electrically conducting layer. Preferably, the inductor (116) and the cable follow an “S”-shaped path to facilitate good electromagnetic coupling therebetween. The RF cables (60) are laid in the trough (80) and the shield conductors inductively couple with the inductor (116). A capacitor (82) and optional trim capacitor (83) are connected across the the trough of the inductor (116) to form a resonant LC circuit tuned to the resonance frequency. The LC circuit inductively couples with the shield conductors (114) to present a high, signal attenuating impedance at the resonance frequency. The resonant circuit is preferably contained in an RF-shielding box (84) with removable lid.

Abstract: A pair of quadrature radio frequency coils (32, 34) disposed adjacent an imaging region (10) are typically loaded differently due to factors such as subject geometry, subject mass, and a relative distance from the subject. A tip angle adjustment circuit (50) monitors a combined tip angle adjacent a mid-plane of the examination region, such as by analyzing delivered and reflected power to each of the coils. An adjustment circuit (54) adjusts relative RF power or amplitude to produce a selected, combined tip angle in the examination region.

Abstract: A pair of quadrature radio frequency coils (32, 34) disposed adjacent an imaging region (10) are typically loaded differently due to factors such as subject geometry, subject mass, and a relative distance from the subject. A tip angle adjustment circuit (50) monitors a combined tip angle adjacent a mid-plane of the examination region, such as by analyzing delivered and reflected power to each of the coils. An adjustment circuit (54) adjusts relative RF power or amplitude to produce a selected, combined tip angle in the examination region.

Abstract: A method of magnetic resonance imaging includes supporting a subject in an examination region of an MRI scanner(A). An MRI pulse sequence is applied to produce a detectable magnetic resonance signal (100) in a selected region of the subject. The magnetic resonance signal (100) includes a plurality of echos (102a-h) which are received. The plurality of received echos (102a-h) are subjected to a controllable gain factor such that at least two echos are subjected to different gain factors. In this manner, for example, a multi-contrast acquisition and imaging experiment may be achieved with each set of acquired echos and/or each image having a separately optimized (e.g., optimized for SNR considerations) gain factor individually selected and/or set therefor.

Abstract: A tunable radio frequency birdcage coil (26, 34) has an improved tuning range for use with a magnetic resonance apparatus. The coil includes a pair of end ring conductors (60, 62) which are connected by a plurality of spaced leg conductors (L2, L4, . . ., L26) to form a generally cylindrical volume. Both the end rings and the leg conductors contain reactive elements, preferably capacitors (C2, C4, . . ., C124). The radio frequency coil also includes a pair of tuning rings (100, 120) for tuning the reactive elements (C2, C4, . . ., C124), which each include a non-conductive support cylinder (110, 130) and a plurality of tuning bands (120, 122, . . ., 142 and 150, 152, . . ., 172) which extend axially along the outer surface of the support cylinder (110, 130). The tuning rings (100, 120) are rotated or translated with respect to the leg conductors (L2, L4, . . ., L26) in order to vary capacitance and inductance of the coil (26, 34) to tune the (26, 34) coil to the desired resonant frequency.

Abstract: A magnetic resonance apparatus includes a multi-mode receiver assembly which facilitates operation in both a quadrature combination mode and phased array mode. The multi-mode receiver assembly includes a receiver coil assembly (30) comprising a first RF coil assembly (32) and a second RF coil assembly (34). A signal combining circuit, which includes a switch means, performs at least one of combining and splitting magnetic resonance signals received by the first and second RF coil assemblies (30, 32). The application of a DC bias potential to the switch means switches the multi-mode receiver assembly into the quadrature combination mode in which the received magnetic resonance signals are phase shifted and combined into a quadrature signal and an anti-quadrature signal. The absence of a DC bias potential to the switch means switches the multi-mode receiver assembly into the phased array mode in which the received magnetic resonance signals are phase shifted and passed individually to corresponding receivers.

Abstract: A magnetic resonance imaging system includes a patient couch (10) which selectively positions a patient relative to an examination region (14). An imaging coil (B) is disposed adjacent to a region of interest for receiving magnetic resonance signals emanating from the patient. A processor (48) both controls the imaging event and processes received signals from the imaging coil. A plug and socket assembly (24, 26) having a proximal component and a distal component relative to the imaging coil provides selective electrical connectivity between the imaging coil (B) and the processor (48). A non-volatile memory device (86), such as a 1-WIRE™ EEPROM, is affixed to the proximal component of the plug and socket assembly (24, 26) for storing a variety attributes associated with the imaging coil. The memory device is most conveniently mounted to a coaxial connector (110).

Abstract: A gradient amplifier (20), for driving a gradient coil (22) of an MRI scanner, includes a plurality of first modules (60). The first modules (60) provide unipolar PWM control of an input supplied thereto to generate a unipolar waveform. A high voltage DC power supply (64) electrically connected to the first modules (60) supplies the input to the first modules (60). At least one second module (140a, b) is electrically connected to the first modules (60). The second module (140a, b) selectively provides polarity switching of the unipolar waveform output from the first modules (60) to generate a bipolar waveform which drives the gradient coil (22).

Abstract: A multi-channel balun (70, 72) blocks stray RF current from flowing on shield conductors of coaxial RF cables of a magnetic resonance apparatus. The balun comprises a parallel combination of an even number of helical coils of shielded transmission cable (L10, L12; L14, L16, L18, L20) wound in alternate directions such that voltages iduced by their external RF fields cancel. One capacitor (C10; C16, C18) is connected in parallel symmetrically with each pair of helical coils, with trim capacitors (C12; C22) fixed in the coil plug (86, 90) to retune the balun as required. The multi-channel balun (70, 72) accommodates magnetic resonance systems with an odd or even number of channels without requiring shielding. Preferably, the balun (70, 72) is constructed on a single circuit board in a close-packed relationship that is compact and space efficient, yet provides better decoupling from the transmit field.

Abstract: A subsurface safety valve has a tubular valve housing, a valve closure member movable between an open and a closed position, an axially shiftable flow tube for opening the valve closure member. Hydraulic pressure from the control line is used to move a piston, which in turn moves an axially shiftable opening prong through the closure member. A balance line, or second hydraulic line is also used to make the valve well insensitive. An isolation valve is placed in the flow path of the second hydraulic line. The isolation valve prevents gas migration into the balance line. It also provides volume control for the fluid displaced when the piston is moved by pressure from the control line. Further, the valve can be closed by the application of sufficient pressure through the second hydraulic line.