Image analysis – Applications – Biomedical applications
Reexamination Certificate
2001-06-12
2004-10-12
Patel, Jayanti K. (Department: 2625)
Image analysis
Applications
Biomedical applications
C378S004000, C600S410000
Reexamination Certificate
active
06804384
ABSTRACT:
TECHNICAL FIELD
This invention relates to color magnetic resonance imaging.
BACKGROUND
In traditional magnetic resonance imaging (MRI), a patient lies within a tubular structure where the patent is subjected to spatial and temporal magnetic field gradients. MRI uses the fact that atomic nuclei spin to collect image data. If the number of protons in a nucleus is even, their spins will cancel; however, if there is an odd number, there will be a net spin that can be used to conduct MRI, see, e.g., U.S. Pat. No. 5,397,987, which is incorporated by reference herein. Hydrogen nuclei have a single proton, and many MRI techniques utilize hydrogen nuclei since they are pervasive in human tissue. When a subject is placed in a main magnetic field, its nuclei align in the direction of the field (i.e., along the “magnetization axis”); the orientation of the nuclei can be represented by a magnetization vector, see, e.g., Horowitz,
MRI Physics for Radiologists: A Visual Approach,
1995, which is incorporated by reference herein. These spinning nuclei can precess in a conical manner around the magnetization axis, generally out-of-phase with respect to each other. To induce in-phase spinning at the resonance frequency of particular nuclei, a radio frequency (RF) excitation pulse is broadcast at that resonance frequency. This RF pulse also causes the nuclei to rotate with respect to the magnetization vector created by the main magnetic field, see, e.g., Horowitz,
MRI Physics for Radiologists: A Visual Approach,
1995, incorporated by reference herein. After the RF excitation pulse, free induction decay (FID) signals are collected and used to generate MR images.
There are two major forms of relaxation, or decay, in MRI: a longitudinal component and a transverse component, see, e.g., E. Fukushima and S. Roeder,
Experimental Pulse NMR—A Nuts and Bolts Approach,
1981, incorporated herein by reference. One form of relaxation is “de-phasing” of the nuclear spins over time after the RF pulse. This phenomenon is known as the “transverse relaxation” (or spin-spin relaxation), and the time constant for this relaxation is labeled T
2
. The other form of relaxation is the realignment of the magnetization vectors along the main magnetic field. This is known as the “longitudinal relaxation” (or spin-lattice relaxation), and the time constant for this relaxation is labeled T
1
. Both of these relaxation phenomena are characterized by exponential decay.
MR images are generated from the FID signals. These images are often in black and white. Techniques are also known for producing gray scale images using T
1
, T
2
, and proton density data, see, e.g., Ronald T. Droege et al., “Nuclear Magnetic Resonance: A Gray Scale Model for Head Images,”
Radiology,
148:763-771 (1983). There are also methods for generating color images. One approach is to convert a monochrome image into one that is in color, see U.S. Pat. No. 4,998,165. Other approaches to producing color images take both T
1
and T
2
data as inputs and use specified methods to render color images, see, e.g., U.S. Pat. Nos. 5,486,763; 5,410,250; 4,789,831.
SUMMARY
In one aspect of the invention, an article containing a computer-readable medium on which a computer program is stored has instructions for causing a processor to receive spatial magnetic resonance data obtained from a sample and generate color image data using the magnetic resonance data. The color image data reflect both a magnetic resonance property of the magnetic resonance data and a function of the magnetic resonance property. This invention permits a user to evaluate the magnetic resonance property of the sample to ascertain the spatial composition of the sample.
Embodiments of this aspect of the invention include one or more of the following features. The function can be selected to enhance the color image data. This enhancement is the result of providing greater informational content. For example, the function of the magnetic resonance property can enhance the color image by indicating the confidence level of the magnetic resonance property. The function can be selected to enhance at least one region of a color image produced from the color image data. This region is enhanced on the basis of hue, brightness, or saturation. By using hue, brightness, or saturation to enhance the color image by indicating, e.g., the confidence level of a magnetic resonance property, the color image facilitates quick and easily comprehension of this information by a researcher or clinician. The function can also be selected to distinguish at least one region of the color image on the basis of the composition of the material in the corresponding region of the sample. This is useful, e.g., to identify regions where a probe passes through tissue in a sample. In addition, the function can be selected to distinguish at least one region of the color image on the basis of the presence of material in the corresponding region of the sample. The function can be further selected to distinguish at least one region of the color image on the basis of the homogeneity of material in the corresponding region of the sample. Distinguishing on the basis of the homogeneity of material in a region of the sample permits a user of the color image to differentiate between regions containing homogenous tissue and regions containing a mixture of tissue.
The magnetic resonance data are obtained using a Fourier transform of free induction decay signals. The magnetic resonance property can be an estimate of T
2
, T
1
, or thermal relaxation. By using a single parameter, this technique exploits the particular advantages of that magnetic resonance property, such as the sensitivity T
2
to time-dependent changes. Since T
2
is affected by metabolic changes in the brain, T
2
can be used for functional MRI, e.g., to track changes over time, through treatment regimens, between or among subjects, or a combination thereof. For example, this approach can be used to monitor levels of drugs or other chemicals in the blood or other tissues over time. The estimate of T
2
, {circumflex over (T)}
2
, is calculated using:
T
^
2
=
σ
t
2
C
x
,
t
,
where
σ
t
=
N
-
1
∑
n
=
0
N
-
1
t
n
2
-
(
N
-
1
∑
n
=
0
N
-
1
t
n
)
2
,
I
N
=
N
-
1
∑
n
=
0
N
-
1
x
n
-
N
-
1
∑
n
=
0
N
-
1
t
n
T
^
2
,
and where N is a number of echo times, t
n
, and x
n
=ln(y
n
) for y
n
>0; otherwise, x
n
=−1, and where y
n
is an intensity of a signal at an echo time, t
n
. Using specially chosen echo times, direct values of signal intensity, y
n
, rather than their natural logarithms, can be used for x
n
, and a value other than −1 could be used for negative y
n
.
The function of the magnetic resonance property can be a function of fit of the T
2
data to a reference curve. Including this characteristic of the T
2
data in the color image allows a viewer to distinguish between a voxel with a single type of tissue with a particular T
2
and a voxel with different tissues that together yield that T
2
. This fit, E, can be calculated using:
E
=
(
σ
x
2
-
C
x
,
t
/
T
^
2
)
1
/
2
I
N
,
and the following additional relationships,
σ
x
=
N
-
1
∑
n
=
0
N
-
1
x
n
2
-
(
N
-
1
∑
n
=
0
N
-
1
x
n
)
2
,
C
x
,
t
=
N
-
1
∑
n
=
0
N
-
1
x
n
t
n
-
(
N
-
1
∑
n
=
0
N
-
1
x
n
)
(
N
-
1
∑
n
=
0
N
-
1
t
n
)
.
The function can also be a function of intensity. Display of intensity information permits one to distinguish readily between voxels containing mostly air and those containing tissue. The intensity, I
N
, can be calculated using:
I
N
=
N
-
1
∑
n
=
0
N
-
1
x
n
-
N
-
1
∑
n
=
0
N
-
1
t
n
T
^
2
.
The instructions can include both a function of fit of the first data to a reference curve and a function of intensity. The preceeding eq
Fish & Richardson P.C.
McLean Hospital Corporation
Patel Jayanti K.
LandOfFree
Color magnetic resonance imaging does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Color magnetic resonance imaging, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Color magnetic resonance imaging will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3302687