Image processing apparatus, magnetic resonance imaging apparatus including the same, and magnetic resonance imaging system
A myelin image is generated with a stable contrast regardless of an imaging condition with an MRI apparatus that measures an echo signal generated from a subject by applying a high-frequency magnetic field and a gradient magnetic field to the subject placed in a static magnetic field according to a predetermined imaging sequence. A reconstructed image is obtained from the echo signal. A distribution of a quantitative value of the subject is estimated using a plurality of the reconstructed images, each of which is obtained by a plurality of types of imaging having different imaging conditions of the imaging sequence, and a signal function defining a relationship between the quantitative value of the subject and a signal value of the reconstructed image. An image generation unit generates an arbitrary image from the distribution of the quantitative value.
1. An MRI apparatus comprising:
a measurement unit comprising:
a magnet that generates a static magnetic field;
a gradient magnetic field coil that generates a gradient magnetic field;
a sequencer;
a gradient magnetic field power supply;
a high-frequency magnetic field generator;
a transmission/reception coil that irradiates a high-frequency magnetic field and detects a nuclear magnetic resonance signal from a subject; and
a receiver that detects the nuclear magnetic resonance signal from the subject;
a display; and
a computer coupled to the sequencer, the receiver, and the display, the computer programmed to:
control the sequencer to control the measurement unit to measure the echo signal for each of a plurality of predetermined parameter sets and acquire k-space data for each predetermined parameter set, each parameter set includes imaging parameters including a repetition time (TR), an echo time (TE), a setting intensity (flip angle (FA)) of the high-frequency magnetic field, and a phase (θ) of the high-frequency magnetic field, and each of the plurality of predetermined parameter sets has different imaging parameters,
reconstruct images by performing three-dimensional (3D) inverse Fourier transform on the collected k-space data,
estimate a subject parameter value using a predetermined signal function and the reconstructed images by estimating a longitudinal relaxation time T1 or a longitudinal relaxation speed R1=1/T1 and a transverse relaxation time T2 or a transverse relaxation speed R2=1/T2 as quantitative values for each pixel, and generating T1 and T2 maps,
generate a myelin image from the T1 map and the T2 map, and
display the generated myelin image on the display.
2. The MRI apparatus according to claim 1 , wherein the transverse relaxation speed includes an apparent transverse relaxation speed or includes a transverse relaxation speed calculated using the apparent transverse relaxation speed.
3. The image processing apparatus according to claim 1 , wherein the function includes a product of the longitudinal relaxation speed and the transverse relaxation speed.
4. The MRI apparatus according to claim 1 , wherein the computer is programmed to divide a pixel value of a T1-weighted image by a pixel value of a T2-weighted image, and the pixel value of the T1-weighted image and the pixel value of the T2-weighted image are calculated from the quantitative value.
5. The MRI apparatus according to claim 4 ,
wherein the T1-weighted image is obtained according to an expression for calculating a T1-weighted image from a T1 value, and
wherein the T2-weighted image is obtained according to an expression for calculating a T2-weighted image from a T2 value.
6. The MRI apparatus according to claim 1 , wherein the signal function is generated by interpolating a result obtained by executing a numerical simulation for each of combinations of a plurality of different imaging parameters and subject parameters.