Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Patent
1990-07-30
1992-06-16
Tokar, Michael J.
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
324322, G01R 3320
Patent
active
051227495
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a magnetic resonance imaging apparatus that reconstructs an image using magnetic resonance signals received by a plurality of radio frequency coils.
PRIOR ART
With the magnetic resonance imaging (MRI) apparatus, radio frequency magnetic resonance signals (MR signals) generated in an object body are received by radio frequency coils (RF coils). This process may operate on the so-called multiple coil method whereby a plurality of RF coils receive MR signals, as illustratively shown in FIG. 5. This figure depicts a prior art case where a tomogram is taken of a backbone 2 in an object body 1. A plurality of RF coils 3 are positioned on the back of the object body 1 along the backbone 2 in order to receive the MR signals from within the body. FIG. 6 highlights an RF signal receiving system of a prior art MRI apparatus operating on the multiple coil method. In FIG. 6, reference numerals 11 through N designate a plurality of RF coils arranged parallel to the slice plane of the object body 1. RF signals received by the RF coils are amplified respectively by preamplifiers 11a through Na. The amplified signals enter receivers 11b through Nb that perform such signal processes as frequency conversion, amplification, detection and analog-to-digital (A/D) conversion. The processed signals then enter an image reconstructing device 19. The image reconstructing device 19 reconstructs a plurality of images based on the multiple input signals, and combines these images into a single image. Reference numeral 20 is the object body's sensitive area corresponding to each of the RF coils 11 through N. Adjoining sensitive areas have a mutually overlapping portion therebetween. The images stemming from these sensitive areas are reconstructed by the image reconstructing device 19 into a single image. This multiple coil method is characterized by the fact that the overall sensitive region corresponding to the received MR signals is extensive in the field of view (crosswise) but shallow in the object body's depth direction. That is, the method is suitable for the imaging of backbones or like areas with good S/N ratios. One disadvantage of the multiple coil method is the need for an expanded hardware construction involving pluralities of preamplifiers and receivers associated with the multiple RF coils. Another disadvantage is that the image reconstructing device 19 is required to perform greater amounts of computations for image reconstruction because the device must reconstruct each one of the images associated with the sensitive areas of the coils based on the RF signals coming therefrom.
OBJECT AND SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a magnetic resonance imaging (MRI) apparatus which reduces the bulk of the hardware for MR signal reception and lowers the amount of computations for image reconstruction while operating on the multiple coil method for imaging.
In carrying out the invention, there is provided an MRI apparatus comprising a plurality of radio frequency (RF) coils, a plurality of signal composers (also called "preprocessors," with both terms being used interchangeably in the specification, claims and drawing; the functions thereof are set forth in greater detail hereinbelow.), a plurality of receivers, and an image reconstructing device. The RF coils are positioned on the surface of an object body to receive MR signals coming therefrom, the sensitive areas of the adjoining RF coils having a mutually overlapping portion therebetween. The signal composers are provided to address each group of RF coils whose sensitive areas do not overlap. One signal composer composes a single received signal out of the signals from the RF coils in one group. The receivers carry out such signal processes as detection and A/D conversion on the signals coming from the signal composers. The image reconstructing device reconstructs images based on the output signals from the receivers and puts these images together into a single reconstruct
REFERENCES:
patent: 4816765 (1989-03-01), Boskamp
patent: 4859947 (1989-08-01), Boskamp
patent: 4943775 (1990-07-01), Boskamp et al.
patent: 4973907 (1990-11-01), Bergman et al.
Kojima Moonray
Tokar Michael J.
Yokagawa Medical Systems, Limited
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