1. A method for MRI imaging, the method comprising:
after administering a contrast agent, repeatedly acquiring image data, including modulating contrast enhancement of the contrast agent in time by applying a time-varying radio frequency saturation pulse to said contrast agent, the time-varying radio frequency saturation pulse having a known pulse time course;
reconstructing the image data into image pixels or voxels of at least one of images and a part of the images with contrast enhancements;
determining an intensity time course of the at least one of the images and the part of the images with contrast enhancement;
correlating said intensity time course with the pulse time course of the applied time-varying radio frequency saturation pulse for each image pixel or of the reconstructed images or parts of the images with contrast enhancement to determine a presence of said contrast agent in each image pixel or voxel; and
displaying on a display device at least one of the reconstructed images, the part of the images with contrast enhancement, and a depiction of the presence of contrast agent for a selected image pixel or voxel.
2. The method according to claim 1, wherein said contrast agent comprises at least one exchangeable entity having a nuclear spin and a nuclear spin resonance frequency and having a first and a second exchangeable position, wherein, as a result of the time-varying radio frequency saturation pulse, the exchangeable entity changes between the first and the second exchangeable position, thereby inducing a change in its nuclear spin resonance frequency.
3. The method according to claim 1, further including:
repeating acquisition of parts of the image until all parts of the image have been repeatedly acquired; and
reconstructing the image.
4. The method according to claim 2, wherein the contrast agent is a CEST contrast agent.
5. The method according to claim 1, wherein applying a time-varying radio frequency saturation pulse is performed by varying at least one of power, offset frequency, shape, multiplicity, duration or intervals between said radio frequency saturation pulses for modulating the contrast enhancement.
6. The method according to claim 1, wherein modulating the contrast enhancement comprises switching the contrast enhancement on and off.
7. A device for performing MRI imaging, the device comprising:
an input device which inputs parameter data for a time-varying radio frequency saturation pulse and a contrast agent to generate image data; and
a processor programmed to:
reconstruct the image data into image pixels or voxels of at least a part of images,
calculate an intensity time course of each reconstructed at least part of the images, and
correlate said calculated intensity time course with the input parameter data of the time-varying radio frequency saturation pulse, image pixel by image pixel or image voxel by image voxel, for determining a presence of said contrast agent in a selected one of the image pixels or voxels.
8. The device according to claim 7, wherein the input parameter data includes a time-varying radio frequency pulse time course.
9. A non-transitory machine readable data storage device storing the computer program which controls one or more processors to:
after administration of a contrast agent, repeatedly acquire an image data for at least part of an image, the acquiring of the image data including modulating contrast enhancement of the contrast agent in time by applying a time-varying radio frequency saturation pulse to said contrast agent, the time-varying radio frequency saturation pulse having a known pulse time course;
reconstruct at least a part of an image, with the intensity time course of the part of the image, the image including an array of image pixels or voxels;
correlate said intensity time course with the pulse time course of the applied time-varying radio frequency saturation pulse for at least one selected pixel or voxel of the at least part of the image to determine a presence of said contrast agent in the selected image pixel or voxel; and
display on a display device at least one of the reconstructed image part and an indication of the presence of the contrast agent in the selected at least one image pixel or voxel.
10. A controller for an MRI imaging device, the controller comprising:
an input device which obtains data relating to formation of a time-varying radio frequency saturation pulse,
a control device which controls the MRI imaging device to apply the time-varying radio frequency saturation pulse based on the obtained data to a subject to which a contrast agent has been administered to generate contrast enhanced image data; and
a computer programmed to correlate an intensity time course determined from the image data with a time course of the applied time-varying radio frequency saturation pulse to determine contrast agent influenced tissue parameters in image pixels or voxels of at least part of an image reconstructed from the contrast enhanced image data.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An optical signal monitoring method for measuring the characteristics of a wavelength division multiplexing (WDM) optical signal, comprising the steps of:
combining the WDM optical signal with reference lights to form a combined optical signal;
inputting the combined optical signal to a filter that has a variable transmission wavelength according to an applied driving voltage;
obtaining a linear approximated wavelength with respect to a driving voltage from predetermined wavelengths of the reference lights and driving voltages corresponding to the predetermined wavelengths; and
obtaining a non-linear compensated wavelength from a predetermined non-linear compensation formula with the driving voltage to compensate for a discrepancy between a transmission wavelength of the filter and the linear approximated wavelength.
2. The optical signal monitoring method of claim 1, wherein the linear approximated wavelength is determined by:
x
=
X
1
–
X
2
V
1
–
V
2
\u2062
(
v
–
V
1
)
+
X
1
(
5
)
where x is the linear approximated wavelength, X1 is a first predetermined wavelength, V1 is a first driving voltage, X2 is a second predetermined wavelength, V2 is a second driving voltage, and v is the driving voltage related with x.
3. The optical signal monitoring method of claim 2, wherein the non-linear compensation formula is expressed as:
y
=
x
+
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
Q
m
=
0
M
\u2062
\u2003
\u2062
a
m
\u2062
x
m
\u2062
Ax
+
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
P
M
\u2061
(
x
)
(
7
)
where y is the non-linear compensated wavelength, x is the linear approximated wavelength, X1 is a first predetermined wavelength, X2 is a second predetermined wavelength, M is an arbitrary integer, and am is an mth-order non-linear coefficient.
4. The optical signal monitoring method of claim 1, wherein the non-linear compensation formula is expressed as:
y
=
x
+
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
\u2211
m
=
0
M
\u2062
\u2003
\u2062
a
m
\u2062
x
m
\u2062
Ax
+
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
P
M
\u2061
(
x
)
(
6
)
where y is the non-linear compensated wavelength, x is the linear approximated wavelength, X1 is a first predetermined wavelength, X2 is a second predetermined wavelength, M is an arbitrary constant, and am is an mth-order non-linear coefficient.
5. The optical signal monitoring method of claim 1, wherein the filter is a fiber Fabry-Perot filter.
6. The optical signal monitoring method of claim 1, wherein the reference lights are combined at both sides of the WDM optical signal on the wavelength spectrum representing light intensities at particular wavelengths.
7. The optical signal monitoring method of claim 1, which further includes deriving a driving voltage-light intensity graph of a combined optical signal detected from the filter in the overall wavelength band of the combined optical signal.
8. An optical signal monitoring method for measuring the characteristics of an input wavelength division multiplexing (WDM) optical signal, comprising the steps of:
combining the WDM optical signal with reference lights to form a combined optical signal;
inputting the combined optical signal to a filter that has a variable transmission wavelength according to an applied driving voltage;
obtaining a linear approximated wavelength with respect to a driving voltage from predetermined wavelengths of the reference lights and driving voltages corresponding to the predetermined wavelengths;
sensing the operation temperature of the filter; and
obtaining a non-linear compensated wavelength from a predetermined non-linear compensation formula with the driving voltage and the operation temperature of the filter to compensate for a discrepancy between a transmission wavelength of the filter and the linear approximated wavelength.
9. The optical signal monitoring method of claim 8, wherein the linear approximated wavelength is determined by:
x
=
X
1
–
X
2
V
1
–
V
2
\u2062
(
v
–
V
1
)
+
X
1
(
8
)
where x is the linear approximated wavelength, X1 is a first predetermined wavelength, V1 is a first driving voltage, X2 is a second predetermined wavelength, V2 is a second driving voltage, and v is the driving voltage related with x.
10. The optical signal monitoring method of claim 9, wherein the non-linear compensation formula is expressed as:
\u03bb
=
x
+
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
\u2211
m
=
0
M
\u2062
\u2003
\u2062
\u2211
n
=
0
N
\u2062
\u2003
\u2062
c
m
,
n
\u2062
x
m
\u2062
t
n
\u2062
Ax
+
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
P
MN
\u2061
(
x
,
t
)
(
10
)
where \u03bb is the non-linear compensated wavelength, x is the linear approximated wavelength, X1 is a first predetermined wavelength, X2 is a second predetermined wavelength, M is an arbitrary integer, N is an arbitrary integer, cm, n is an (m, n)th-order non-linear coefficient, and t is the product of the driving voltage related with x and the operation temperature of the filter.
11. The optical signal monitoring method of claim 8, wherein the non-linear compensation formula is expressed as:
\u03bb
=
x
+
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
\u2211
m
=
0
M
\u2062
\u2003
\u2062
\u2211
n
=
0
N
\u2062
\u2003
\u2062
c
m
,
n
\u2062
x
m
\u2062
t
n
\u2062
Ax
+
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
P
MN
\u2061
(
x
,
t
)
(
9
)
where \u03bb is the non-linear compensated wavelength, x is the linear approximated wavelength, X1 is a first predetermined wavelength, X2 is a second predetermined wavelength, M is an arbitrary integer, N is an arbitrary integer, cm, n is an (m, n)th-order non-linear coefficient, and t is the product of the driving voltage related with x and the operation temperature of the filter.
12. The optical signal monitoring method of claim 8, wherein the filter is a fiber Fabry-Perot filter.
13. The optical signal monitoring method of claim 8, wherein the reference lights are combined at both sides of the WDM optical signal on the wavelength spectrum representing light intensities at particular wavelengths.
14. The optical signal monitoring method of claim 8, which further includes deriving a driving voltage-light intensity graph of a combined optical signal detected from the filter in the overall wavelength band of the combined optical signal.
15. An optical signal monitoring apparatus for measuring the characteristics of a wavelength division multiplexing (WDM) optical signal, comprising:
an optical coupler for combining the WDM optical signal with reference lights to form a combined optical signal;
a filter for passing only an optical signal at a predetermined wavelength from the combined optical signal received from the optical coupler according to a driving voltage;
a filter driver for feeding a driving voltage that linearly varies according to an input driving signal;
an optical detector for opto-electrically converting the optical signal received from the filter to an optical detection signal;
a temperature sensor for sensing the operation temperature of the filter and outputting a temperature sensed signal representing the sensed operation temperature; and
a controller for receiving the optical detection signal and the temperature sensed signal, outputting the driving signal to the filter driver, obtaining a linear approximated wavelength with respect to the driving voltage from predetermined wavelengths of the reference lights and driving voltages corresponding to the predetermined wavelengths, and obtaining a non-linear compensated wavelength from a predetermined non-linear compensation formula with the driving voltage and the operation temperature of the filter to compensate for a discrepancy between a transmission wavelength of the filter and the linear approximated wavelength.
16. The optical signal monitoring apparatus of claim 15, wherein the linear approximated wavelength is determined by:
x
=
X
1
–
X
2
V
1
–
V
2
\u2062
\u2003
\u2062
(
v
–
V
1
)
+
X
1
(
11
)
where x is the linear approximated wavelength, X1 is a first predetermined wavelength, V1 is a first driving voltage, X2 is a second predetermined wavelength, V2 is a second driving voltage, and v is the driving voltage related with x.
17. The optical signal monitoring apparatus of claim 16, wherein the non-linear compensation formula is expressed as:
\u03bb
=
\u2062
x
+
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
\u2211
m
=
0
M
\u2062
\u2211
n
=
0
N
\u2062
c
m
,
n
\u2062
x
m
\u2062
t
n
\u2062
Ax
+
\u2062
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
P
MN
\u2061
(
x
,
t
)
(
13
)
where \u03bb is the non-linear compensated wavelength, x is the linear approximated wavelength, X1 is a first predetermined wavelength, X2 is a second predetermined wavelength, M is an arbitrary integer, N is an arbitrary integer, cm, n is an (m, n)th-order non-linear coefficient, and t is the product of the driving voltage related with x and the operation temperature of the filter.
18. The optical signal monitoring apparatus of claim 15, wherein the non-linear compensation formula is expressed as:
\u03bb
=
\u2062
x
+
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
\u2211
m
=
0
M
\u2062
\u2211
n
=
0
N
\u2062
c
m
,
n
\u2062
x
m
\u2062
t
n
\u2062
Ax
+
\u2062
(
x
–
X
1
)
\u2062
(
x
–
X
2
)
\u2062
P
MN
\u2061
(
x
,
t
)
(
12
)
where \u03bb is the non-linear compensated wavelength, x is the linear approximated wavelength, X1 is a first predetermined wavelength, X2 is a second predetermined wavelength, M is an arbitrary integer, N is an arbitrary integer, cm, n is an (m, n)th-order non-linear coefficient, and t is the product of the driving voltage related with x and the operation temperature of the filter.
19. The optical signal monitoring apparatus of claim 15, wherein the filter is a fiber Fabry-Perot filter.
20. The optical signal monitoring apparatus of claim 15, wherein the reference lights are combined at both sides of the WDM optical signal on the wavelength spectrum representing light intensities at particular wavelengths.