Abstract:
An arrangement to transmit magnetic resonance signals has at least two reception branches. Each reception branch contains a single antenna of a local coil as well as an amplifier connected with the single antenna, such that an amplified magnetic resonance signal is formed from a magnetic resonance signal that is acquired via the single antenna. In a multiplexer, each input is connected with a respective reception branch, such that the amplified magnetic resonance signals of the reception branch are combined by the multiplexer into a resulting signal using a time multiplexing method. A transmission path is connected on one side with an output of the multiplexer and on the other side with a receiver, such that the resulting signal is transmitted from the multiplexer to the receiver via the transmission path.
Abstract:
Circuit arrangement for the switchable amplification of variable electrical signals having at least one signal input and a signal output. A switchable amplifier is present between signal input and signal output and is provided with an input, with an output and with a negative feedback path having at least one resistor between input and output. The circuit arrangement further comprises a voltage source, the polarity of which can be reversed by a switching element. In this case, the negative feedback path has a switchable bypass connected in parallel with the at least one resistor. The signals fed in at the amplifier input are furthermore to be fed to the amplifier output in amplified fashion via a first signal path or in unamplified fashion via a second signal path depending on the polarity of the voltage source.
Abstract:
The push-pull amplifier with transformational negative feedback is provided for amplification of variable electrical signals. It includes a signal input and a signal output, a transformational negative feedback connected with the signal input and the signal output and an amplifier circuit. The amplifier circuit includes an input and an output as well as a first transistor and a second transistor. The input of the amplifier circuit is thereby connected with the signal input and the output of the amplifier circuit is thereby connected with the signal output via the transformational negative feedback.
Abstract:
A method is disclosed for determining positron emission measurement information in the context of positron emission tomography. The method includes carrying out a positron emission measurement, in a body area of a subject to be examined, to record positron emission measurement information with point resolution and determining a time frame of the measurement by, at the same time, generating images of the body area to be examined with a relatively higher time resolution and with point-resolved image data, using a second imaging method. Further, a local shift of points of individual images of the second imaging method is determined, caused by movement processes of the subject to be examined, and as a function thereof, of the positron emission measurement information for at least a part of the measurement period and of the body area to be examined. Finally, the positron emission measurement information is adjusted as a function of the determined shift.
Abstract:
In a dynamics compressor, an analog signal to be compressed is supplied to a first amplifier stage as an input signal, and the output signal thereof is supplied to the next amplifier stage as an input signal, and so on for a number of successive amplifier stages. Each amplifier stage amplifies its input signal with a stage amplification until it reaches a stage limit level. The analog signal and the respective output signals of the amplifier stages are summed in a summation stage to form a sum signal. Above a minimal level, the magnitude of the curve of the sum signalroughly corresponds to an exponent characteristic of the magnitude of the analog signal.
Abstract:
An ultrasound transmitting circuit includes an electrical transmitter from which electrical oscillations can be fed at an electrical transmission power level over a connecting line into an ultrasound transducer. The electrical oscillations are formed of a current signal and a voltage signal. The ultrasound transducer can be excited by the electrical oscillations to produce ultrasound oscillations. In order to allow ultrasound oscillation power to be controlled more accurately, the current signal and the voltage signal can be supplied to a phase regulator. A variable impedance, which is coupled to the connecting line, can be actuated by the phase regulator in such a manner that the current signal and the voltage signal are in phase.
Abstract:
A transmit/receive circuit employing passive elements. A transmit/receive circuit according to an embodiment of the present invention includes a transformer having a primary winding coupled to an input stage and an output stage. A transducer is coupled to the secondary winding of the transformer. A diode limiter is coupled to the input stage and a diode bridge is coupled to a node at the output stage. The input and output stages are alternatingly grounded. An output switch including an inverse parallel circuit of two diodes having opposite polarities may be connected at the output stage between a transmitter and the transformer. Alternatively, a complementary common emitter amplifier may be provided at the output stage. The circuit thus electrically couples the transducer element to the receiver during reception and electrically decouples both the transducer and the transmitter from the receiver during transmission. The circuit further electrically couples the transducer to the transmitter during transmission and electrically decouples both the transducer element and the receiver from the transmitter during reception.
Abstract:
A duplexer for an ultrasound imaging-system capable of selectively coupling a transducer element to either a transmitter or a receiver, depending on whether the imaging system is in the transmit mode or receive mode, contains a variable capacitance diode which is connected in a direction opposite that of transmit pulses emitted by the transmitter between the transducer element and the receiver. In this manner, one obtains an improved duplexer that operates with virtually no power loss, without drive circuits, without leakage currents, and with low noise.
Abstract:
A radio-frequency antenna for a magnetic resonance apparatus has an antenna conductor in the form of a ribbon conductor. The ribbon antenna conductor has interconnects arranged side-by-side. Neighboring interconnects are connected to one another via bridges that conduct radio-frequency currents.
Abstract:
A circuit for detuning a resonator in a nuclear magnetic resonance imaging apparatus has an output connected to a terminal of the resonator via a high-frequency line composed of two conductors. The resonator is shortened at this terminal with a shorting capacitor that can be short-circuited for detuning the resonator. The length of the high-frequency line is shorter than one-fourth of the wavelength of a high-frequency signal having the operating frequency of the nuclear magnetic resonance imaging apparatus on the high-frequency line. For detuning the resonator the high-frequency line can be terminated at the output with a further capacitor, so that the high-frequency line acts as a short-circuit at the terminal.