摘要:
Die Erfindung bezieht sich auf eine Schaltungsanordnung zur Erzeugung von Hochfrequenzsignalen für Kernspinuntersuchungen, mit einem Festwertspeicher, in dem ein Signal als Folge von Datenworten gespeichert ist, einem Adressengenerator zum Auslesen von Datenworten aus dem Festwertspeicher mit einer Taktfrequenz und einem dem Festwertspeicher nachgeschalteten Digital-Analog-Wandler. Zur Reduzierung des Speicherbedarfes ist vorgesehen, daß in dem Speicher ein sinusförmiges Signal als Folge von Datenworten gespeichert ist.
摘要:
A method for determining a signature index of an observed tissue comprises the step of providing (12) a generic attenuation model of a motion-probing gradient pulse MRI attenuated signal S(b), and providing (14) a reference model parameter vector (p R (i)) corresponding to a reference state of the tissue. On the basis of the evolution of the determined (16) partial differential sensitivities dS ¡ (b) of the model attenuated signal S(b) to each model parameter p(i) at the neutral state attenuated signal S N (b) versus b values, a discrete and narrow size set of key b is built (18) and a series of MRI images of the observed tissue are acquired (20) by using the key b values. Then, for each voxel a signature index (sADC(V), Sdist(V), SCdist(V), Snl(V), SI(V)) of the voxel V is determined (22) as a scalar function depending on a distance between the voxel signal pattern acquired at the key b values and the signal pattern of the reference state of the tissue at the same key b values. An apparatus is configured for implementing such a method.
摘要:
Die Erfindung betrifft Verfahren zum Betreiben einer Lokalspule (6) für einen Magnetresonanztomographen (2) mit , welche eine Empfangsantenne (16) und einen Signalumsetzer (18) aufweist und signaltechnisch mittels einer Signalleitung (8) mit einer Patientenliege (4) gekoppelt ist, wobei die Empfangsantenne (16) ein analoges Magnetresonanzsignal (22) in einem ersten Signalfrequenzbereich (24) empfängt, wobei das analoge Magnetresonanzsignal (22) mittels des Signalumsetzers (18) in ein digitales Magnetresonanzsignal (34) gewandelt und derart frequenzverschoben wird, dass das digitale Magnetresonanzsignal (34) in einen mit dem ersten Signalfrequenzbereich (24) nicht überlappenden, vorzugsweise gegenüber diesem höherfrequenten, zweiten Signalfrequenzbereich (38) versetzt wird.
摘要:
There are provided a magnetic resonance imaging device and a method of controlling a MRI device. The MRI device includes an RF transmitting coil configured to transmit an RF to an object on a table; an object scanning unit including a position detecting unit configured to detect a position of the object and a thickness detecting unit configured to detect a thickness of the object, and configured to recognize a body shape of the object; and a control unit configured to regulate the RF to be transmitted, thereby compensating an RF field based on the recognized body shape of the object.
摘要:
The invention provides for a magnetic resonance imaging system (100) for acquiring magnetic resonance data (142, 144) from an imaging zone (108). Execution of the instructions causes a processor (133) controlling the MRI system to: acquire (200) imaging magnetic resonance data (142) with radio frequency excitation of the radio frequency system enabled; acquire (202) noise radio frequency data (148) using at least one RF noise detection coil, wherein the noise radio frequency data is acquired simultaneously with the imaging magnetic resonance data; acquire (204) calibration magnetic resonance data (144) with radio frequency excitation of the radio frequency system disabled; acquire (206) reference radio frequency data (146) using the at least one RF noise detection coil, wherein the reference radio frequency data is acquired simultaneously with the calibration magnetic resonance data; and calculate (208) a noise calibration (150) using the reference radio frequency data and the calibration magnetic resonance data.
摘要:
Described here are systems and methods for improved magnetic resonance imaging ("MRI"} using a radio frequency ("RF"} system that establishes a Larmor frequency using a clock signal generated by the RF system to provide phase coherency and improved spectral quality among the RF pulses generated by the RF system. With this system, the conventionally relied-upon reference signal is no longer needed to maintain phase coherency. Instead, the system clock of the RF system is used to create the Larmor frequency used for pulse formation in the RF transmitter and for signal demodulation in the RF receiver.
摘要:
The invention relates to a magnetic resonance imaging system for acquiring magnetic resonance data from a subject within an imaging volume. The magnetic resonance imaging system comprises a transmitter for generating radio-frequency pulses (708) for exciting atomic nuclei within the imaging volume using a radio-frequency antenna. The transmitter has a fixed output amplitude and a modulated output. The transmitter is configured to generate the radio-frequency pulses by switching radio-frequency emissions at the fixed output amplitude on and off. The transmitter is further configured to generate the radio-frequency pulses by controlling the modulated output. The magnetic resonance imaging system further comprises a receiver for receiving radio-frequency emissions from the excited atomic nuclei using the radio-frequency antenna.
摘要:
Herein a method for slice selection is provided in an MRI process, the method involves controlling a transmit array by adding low flip angle RF pulses interspersed between refocusing pulses that are used to move a k-space weighting function with respect to one or more B 1 fields used to deposit energy according to a desired k-space weighting function. The low flip angle pulses deposit energy so that an envelope traced by the low flip angle pulses in the k-space weighting function is related to a desired spatially excited region of the sample volume, for example by a Fourier transform, if the phase encoding directions are linear axes that coordinatize the sample volume, and the B 1 fields have linear phase gradients.