摘要:
A magnetic resonance imaging method is provided in which the magnetic resonance signals are acquired by sampling a selected region in the k-space. The selected region in the k-space is chosen in dependence on the object or structure to be imaged. In particular an anisotropic central sector in the k-space is chosen, its axis being dependent on the spatial orientation of the object or structure to be imaged. The magnetic resonance imaging method in accordance with the invention is particularly suitable for imaging arteries separately from veins in magnetic resonance angiography.
摘要:
The invention relates to a method of MR imaging of at least a portion of a body (110) of a patient placed in an examination volume of a MR device, the method comprising the steps of:—subjecting the portion of the body (110) to an imaging sequence comprising at least one RF pulse, the RF pulse being transmitted toward the portion of the body (110) via a RF coil arrangement (109) to which RF signals are supplied by two or more RF power amplifiers the RF power amplifiers being activated alternately during the imaging sequence in a time-multiplexed fashion, wherein the imaging sequence requires a RF duty cycle and/or a RF pulse duration exceeding the specification of at least one of the RF power amplifiers;—acquiring MR signals from the portion of the body (110); and—reconstructing a MR image from the acquired MR signals. Moreover, the invention relates to a method of MR spectroscopy involving the alternating use of RF power amplifiers in a time-multiplexed fashion.
摘要:
The invention relates to a method of MR imaging of at least a portion of a body (110) of a patient placed in an examination volume of a MR device, the method comprising the steps of:—subjecting the portion of the body (110) to an imaging sequence comprising at least one RF pulse, the RF pulse being transmitted toward the portion of the body (110) via a RF coil arrangement (109) to which RF signals are supplied by two or more RF power amplifiers the RF power amplifiers being activated alternately during the imaging sequence in a time-multiplexed fashion, wherein the imaging sequence requires a RF duty cycle and/or a RF pulse duration exceeding the specification of at least one of the RF power amplifiers;—acquiring MR signals from the portion of the body (110); and—reconstructing a MR image from the acquired MR signals. Moreover, the invention relates to a method of MR spectroscopy involving the alternating use of RF power amplifiers in a time-multiplexed fashion.
摘要:
A novel magnetic resonance imaging method is described, for forming an image of an object from a plurality of signals sampled in a restricted homogeneity region of a main magnet field of a magnetic resonance imaging apparatus. A patient disposed on a table is moved continuously through the bore of the main magnet and spins in a predetermined area of the patient are excited by an excitation pulse from a transmitter antenna, such that an image is formed over a region exceeding largely the restricted region. Data is undersampled in the restricted region by means off at least one receiver antenna in a plurality of receive situations being defined as a block of measurements contiguous in time having preserved magnetisation and presaturation conditions within the excited area of the patient. Fold-over artefacts due to said undersampling are unfolded by means of the known sensitivity pattern of the receiver antenna and/or the properties of selected factors determining said receive situations.
摘要:
The invention relates to a method for obtaining MRI images in a vertical main field while using a sub-sampling scheme like SENSE. The invention proposes a number of coil arrangements such that the advantages of SENSE (high speed acquisition) and vertical field (open view for the patient so as to avoid sensations of fear and claustrophobia) are combined. The coil arrangements preferably include butterfly coils and are arranged in such a way that they offer access to the patient and also allow the patient to be moved into and out of the imaging volume without interference by the RF coils.
摘要:
In order to provide a magnetic resonance imaging system and method which allows an optimal timing of the imaging sequence at minimal procedure cost, a magnetic resonance imaging system and method is proposed, wherein a first MR scan of a structure of interest is performed for detecting the arrival of a contrast bolus in the structure of interest, the first MR scan using a first resonance frequency corresponding to first MR sensitive nuclei, the first performing step is repeated at least until the bolus arrival in the structure of interest has been detected, and a second MR scan of the structure of interest is performed for acquiring a MR image, the second MR scan using a second resonance frequency corresponding to second MR sensitive nuclei, the second nuclei being different from the first nuclei.
摘要:
The invention relates to a method for magnetic resonance imaging (MRI) of at least a portion of a body placed in a stationary and substantially homogeneous main magnetic field. The method comprises the steps of subjecting the body to a diffusion-weighting sequence (DW1), generating a train of MR echoes (E1, E2, E3, E4, E5) by an imaging sequence (EPI1), and measuring this train of MR echoes. These steps are repeated until a complete imaging data set with a sufficient number of phase-encoding steps is measured. Thereafter, the imaging data set is corrected for macroscopic motions by means of an individual phase-correction of each train of MR echoes. Finally, an image is reconstructed from the imaging data. In order to provide a method for diffusion-weighted imaging, which requires a minimum additional measurement time for determining the phase errors of the imaging signals and which also guarantees a robust compensation of image artifacts caused by macroscopic motions of the body of the examined patient, the invention suggests to select the phase-encoding scheme of the imaging sequence such that each train of MR echoes (E1, E2, E3, E4, E5) comprises at least one initial MR navigator echo (E1), which forms and integral part of the imaging data set, wherein the phase-correction is derived from the MR navigator echo.
摘要:
A magnetic resonance imaging method is proposed wherein the MR signal acquisition is performed by separate scanning of central (40) and peripheral (70) sectors. Central and peripheral sectors are selected in an individual plane in the k-space and optionally an intermediate sector (50) between the peripheral and central sectors is also selected. The center (O) in the k-space in the individual plane at issue is situated within the central sector. The scanning of the k-space commences outside the center of the k-space and before or during increasing contrast. Preferably, the scanning is timed such that the center of the k-space is reached at maximum contrast (MR angiography) or at the value zero of the longitudinal magnetization (MR inversion recovery). The central sector is advantageously scanned in a stochastic order. The peripheral sector may be scanned along a spiral-shaped trajectory, radial trajectories or along high-low ordered lines.
摘要:
A therapeutic apparatus comprising a radiotherapy apparatus for treating a target zone and a magnetic resonance imaging system for acquiring magnetic resonance imaging data. The radiotherapy apparatus comprises a radiotherapy source for directing electromagnetic radiation into the target zone. The radiotherapy apparatus is adapted for rotating the radiotherapy source at least partially around the magnetic resonance magnet. The magnetic resonance imaging system further comprises a radio-frequency transceiver adapted for simultaneously acquiring the magnetic resonance data from at least two transmit-and-receive channels. The therapeutic apparatus further comprises a processor and a memory containing machine executable instructions for the processor. Execution of the instructions causes the processor to: calibrate the transmit-and-receive channels; acquire the magnetic resonance data; reconstruct a magnetic resonance image; register a location of the target zone in the image; and generate radiotherapy control signals using the registered image.
摘要:
A magnetic resonance method of electric properties tomography imaging of an object includes applying an excitation RF field to the object via a coil at a first spatial coil position (402), acquiring resulting magnetic resonance signals via a receiving channel from the object, determining from the acquired magnetic resonance signals a first phase distribution and a first amplitude of a given magnetic field component of the excitation RF field of the coil at the first coil position (402), repeating these steps with a coil at a second different spatial coil position (404), to obtain a second phase distribution, determining a phase difference between the first and second phase distribution, determining a first and a second complex permittivity of the object, the first complex permittivity comprising the first amplitude of the given magnetic field component and the second complex permittivity comprising the second amplitude of the given magnetic field component and the phase difference, equating the first complex permittivity and the second complex permittivity for receiving a final equation and determining from the final equation a phase of the given magnetic field component for the first coil position (402).