Electricity: measuring and testing – Particle precession resonance – Using a nuclear resonance spectrometer system
Reexamination Certificate
2002-09-19
2004-08-10
Fulton, Christopher W. (Department: 2859)
Electricity: measuring and testing
Particle precession resonance
Using a nuclear resonance spectrometer system
Reexamination Certificate
active
06774629
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Japanese Application No. 2001-308133 filed Oct. 4, 2001.
BACKGROUND OF THE INVENTION
The present invention relates to a water/fat phase identifying method, image producing method and magnetic resonance imaging apparatus, and particularly to a water/fat phase identifying method for identifying the phases of water and fat in a complex image captured using magnetic resonance, an image producing method for producing a water image or a fat image, and a magnetic resonance imaging apparatus for suitably implementing these methods.
Japanese Patent Application Laid Open No. 2001-204711 discloses a method involving: capturing a complex image using magnetic resonance with the phase differentiated between water and fat; extracting separate signal regions in the complex image; generating respective phase histograms of the signal regions; and identifying the phases of water and fat based on the phase histograms.
The conventional technique disclosed in Japanese Patent Application Laid Open No. 2001-204711 conducts processing for extracting separate signal regions in a complex image.
The area of the signal region, however, varies because it depends on the image. If the area of the signal region is too small, the number of data points contained in the signal region is too small and the effect of noise becomes significant, whereby a good phase histogram cannot be obtained. On the contrary, if the area of the signal region is too large, the effect of inhomogeneity of the static magnetic field becomes significant, and again, a good phase histogram cannot be obtained. If a good phase histogram cannot be obtained, the phases of water and fat cannot be suitably identified.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a water/fat phase identifying method capable of suitably identifying the phases of water and fat without conducting the processing of extracting separate signal regions in a complex image, an image producing method for producing a water image or a fat image, and a magnetic resonance imaging apparatus for suitably implementing these methods.
In accordance with its first aspect, the present invention provides a water/fat phase identifying method characterized in comprising: capturing a complex image using magnetic resonance with the phase differentiated between water and fat; dividing said complex image into a multiplicity of sections; generating a phase histogram for each section; determining whether the phases of water and fat can be identified from the phase histogram of a section of interest; if the phases can be identified, obtaining the phases of water and fat in the section of interest from the phase histogram of the section of interest; if the phases cannot be identified, generating an additive phase histogram by adding phase histograms of sections in a predefined range proximate to the section of interest; and obtaining the phases of water and fat in the section of interest from said additive phase histogram.
In the water/fat phase identifying method of the first aspect, a complex image is divided into a multiplicity of sections; if the phases of water and fat can be identified from a phase histogram of a certain section, the phases of water and fat are obtained from the phase histogram of the section; and if the phases cannot be identified, phase histograms of proximate sections in a predefined range are added to obtain the phases of water and fat from an additive phase histogram. Since the area for which a phase histogram is generated is thus automatically changed, the phases of water and fat can be suitably identified.
In accordance with its second aspect, the present invention provides a water/fat phase identifying method characterized in comprising: capturing a complex image using magnetic resonance with the phase differentiated between water and fat; dividing said complex image into a multiplicity of sections; generating a phase histogram for each section; determining whether the phases of water and fat can be identified from the phase histogram of a section of interest; if the phases can be identified, obtaining the phases of water and fat in the section of interest from the phase histogram of the section of interest; if the phases cannot be identified, generating an additive phase histogram by adding phase histograms of sections in a predefined range proximate to the section of interest; determining whether the phases of water and fat can be identified from said additive phase histogram; if the phases can be identified, obtaining the phases of water and fat in the section of interest from said additive phase histogram; and if the phases cannot be identified, repeating the foregoing processing with stepwise enlargement of said predefined range to obtain the phases of water and fat in the section of interest.
In the water/fat phase identifying method of the second aspect, a complex image is divided into a multiplicity of sections; if the phases of water and fat can be identified from a phase histogram of a certain section, the phases of water and fat are obtained from the phase histogram of the section; and if the phases cannot be identified, phase histograms of proximate sections in a predefined range are added; if the phases of water and fat can be identified from the additive phase histogram, the phases of water and fat are obtained from the additive phase histogram; and if the phases cannot be identified, the same processing is repeated with stepwise enlargement of the predefined range. Since the area for which a phase histogram is generated is thus automatically changed, the phases of water and fat can be suitably identified.
In accordance with its third aspect, the present invention provides the water/fat phase identifying method having the aforementioned configuration, characterized in comprising: if the phases cannot be identified even when said predefined range is enlarged to a predefined limit range, terminating said repetition of the processing, and obtaining the phases of water and fat in the section of interest based on phases of water and fat of another section whose phases of water and fat could be obtained.
In the water/fat phase identifying method of the third aspect, the enlargement of the area for which a phase histogram is generated is terminated at a predefined limit range, and the phases of water and fat in a section of interest are obtained based on phases of water and fat of another section whose phases of water and fat could be obtained. This prevents unnecessarily lengthening of the processing time.
In accordance with its fourth aspect, the present invention provides the water/fat phase identifying method having the aforementioned configuration, characterized in that: when enlarged for an i-th (i=1, 2, . . . ) time, said predefined range is an range which has the section of interest surrounded by i layers of other sections.
In the water/fat phase identifying method of the fourth aspect, since the area for which a phase histogram is generated is enlarged so that a section of interest is surrounded by other sections, the section of interest is centered, and any first-order phase shift between the sections can be canceled out.
In accordance with its fifth aspect, the present invention provides a water/fat phase identifying method characterized in comprising: capturing a complex image using magnetic resonance with the phase differentiated between water and fat; dividing said complex image into a multiplicity of sections; generating a phase histogram for each section; determining whether the phases of water and fat can be identified from the phase histogram of a section of interest; if the phases can be identified, obtaining the phases of water and fat in the section of interest from the phase histogram of the section of interest; and if the phases cannot be identified, obtaining the phases of water and fat in the section of interest based on phases of water and fat of a section which lies proximate to the section of interest
Fulton Christopher W.
GE Medical Systems Global Technology Company LLC
Horton Esq. Carl B.
Vargas Dixomara
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