CN102008308B - Multi-b value diffusion tensor imaging sampling method - Google Patents

Abstract

The invention relates to a multi-b value diffusion tensor imaging sampling method, which comprises the following steps: carrying out single-scanning on the whole visual field under a first b value, sampling to obtain the single-scanning signal-to-noise ratio under the first b value and the single-scanning signal strength under the first b value; obtain the number of multi-scanning under the first b value according to the single-scanning signal-to-noise ratio under the first b value and the designated multi-scanning signal-to-noise ratio under the first b value; calculating to obtain the single-scanning signal-to-noise ratio under a second b value according to the single-scanning signal-to-noise ratio under the first b value and the single-scanning signal strength under the first b value; and calculating to obtain the number of the multi-scanning under the second b value according to the single-scanning signal-to-noise ratio under the second b value and the designated multi-scanning signal-to-noise ratio under the second b value. The multi-b value diffusion tensor imaging sampling method can select the number of repeated scanning which is actually required by various b values in an adaptive manner by implementing the single pre-scanning on the first b value and referring to the relationship followed by the signal-to-noise ratios of the different b values, further reduce the total number of sampling, greatly reduce the sampling time and improve the diffusion tensor imaging speed.

Description

Many b value dispersion tensor imaging method of samplings

[technical field]

The present invention relates to the dispersion tensor imaging, relate in particular to a kind of many b value dispersion tensor imaging method of samplings.

[background technology]

Diffusing phenomenon relates to the Brownian movement of molecule in the fluid, and the size of diffusing capacity is represented through dispersion coefficient.In the liquid of homogeneity, dispersion coefficient is identical on all directions, that is to say under 3-D view, and disperse process should be a ball-type; But in bio-tissue, the dispersion coefficient on the different directions is different, and for example moisture is in bigger along the suffered disperse restriction of the direction of aixs cylinder perpendicular to the direction ratio of aixs cylinder at myelinated nerve fiber, and what disperse process demonstrated is spheroid shape.For each voxel in the imaging region, the disperse motor process of hydrone can be regarded as a spheroid.The disperse motor process of hydrone can be represented with a dispersion tensor.

The dispersion tensor imaging is the specific form of NMR-imaging, is to develop new mr imaging technique rapidly in recent years.The dispersion tensor imaging technique is to utilize the disperse anisotropy of hydrone to be carried out to picture, can provide disease condition at cell and molecular level from the integrity of the field evaluation of tissue structure of microcosmic, is an important component part of functional mri.In the dispersion tensor imaging, represent the disperse factor with b, the size of b depends on the waveform of the disperse gradient that applies.The size of b value has influence on the process of disperse.The b value is big more, and disperse is big more, and the signal to noise ratio of signal is just more little.Dispersion tensor is imaged in the practical application, the single index Changing Pattern that comes the match disperse process to be followed through a plurality of b values usually.In order to satisfy signal to noise ratio, traditional way scans to improve signal to noise ratio through all b values being adopted same number of repetition.Thereby cause the overlong time of sampling, influence the speed of dispersion tensor imaging.

[summary of the invention]

Based on this, be necessary to provide a kind of many b value dispersion tensor imaging method of samplings that can improve the dispersion tensor image taking speed.

A kind of many b value dispersion tensors imaging method of sampling may further comprise the steps: A1, under a b value the single sweep operation whole visual field, sampling obtains under the b value single sweep operation noise single sweep signal intensity under the b value when; A2, according to a said b value down the single sweep operation noise when time specified snr computation that repeatedly scans of a b value obtain under the b value repeatedly scanning times; A3, according to a said b value down the when said b value of single sweep operation noise time single sweep signal intensity calculate single sweep operation signal to noise ratio under the 2nd b value; A4, according to said the 2nd b value down the single sweep operation noise when time specified snr computation that repeatedly scans of the 2nd b value obtain under the 2nd b value repeatedly scanning times;

A b value described in the steps A 1 fitting formula of single sweep signal intensity down is:

$S_1=S_0{e}^{-b_{1}D}$

Wherein, S ₁Be single sweep signal intensity under the said b value, S ₀Signal intensity when not having the disperse gradient, b ₁Be a said b value, D is a dispersion coefficient;

Calculating under the b value repeatedly in the steps A 2, the formula of scanning times is:

$\frac{{\mathrm{SNR}}_1}{\sqrt{1}}=\frac{{\mathrm{SNR}}_{N1}}{\sqrt{N1}}$

Wherein, SNR ₁Be single sweep operation signal to noise ratio under the said b value, SNR _N1For a said b value repeatedly scans down signal to noise ratio, N1 is a scanning times repeatedly under the said b value;

Steps A 3 comprises the steps: A31, calculates single sweep signal intensity under the 2nd b value according to single sweep signal intensity under the said b value; A32, according to a said b value down the relation of single sweep signal intensity and said the 2nd b value time single sweep signal intensity calculate single sweep operation signal to noise ratio under said the 2nd b value;

The formula that calculates single sweep signal intensity under the 2nd b value in the steps A 31 is:

$\frac{\ln S_1-\ln S_0}{\ln S_2-\ln S_0}=\frac{-b_1}{-b_2}$

Wherein, b ₁Be a said b value, b ₂Be said the 2nd b value, S ₁Be single sweep signal intensity under the said b value, S ₂Be single sweep signal intensity under said the 2nd b value, S ₀Signal intensity when not having the disperse gradient;

The 2nd b value described in the steps A 31 fitting formula of single sweep signal intensity down is:

$S_2=S_0{e}^{-b_{2}D}$

Wherein, S ₂Be single sweep signal intensity under said the 2nd b value, S ₀Signal intensity when not having the disperse gradient, b ₂Be said the 2nd b value, D is a dispersion coefficient;

Calculate in the steps A 32 under the said b value single sweep operation signal to noise ratio and said the 2nd b value down the formula of the relation between the single sweep operation signal to noise ratio be:

$\frac{S_1}{S_2}=\frac{{\mathrm{SNR}}_1}{{\mathrm{SNR}}_2}$

Wherein, S ₁Be single sweep signal intensity under the said b value, S ₂Be single sweep signal intensity under said the 2nd b value, SNR ₁Be single sweep operation signal to noise ratio under the said b value, SNR ₂Be single sweep operation signal to noise ratio under said the 2nd b value;

Calculating under the 2nd b value repeatedly in the steps A 4, the formula of scanning times is:

$\frac{{\mathrm{SNR}}_2}{\sqrt{1}}=\frac{{\mathrm{SNR}}_{N2}}{\sqrt{N2}}$

Wherein, SNR ₂Be single sweep operation signal to noise ratio under said the 2nd b value, SNR _N2For said the 2nd b value repeatedly scans down signal to noise ratio, N2 is a scanning times repeatedly under said the 2nd b value.

Above-mentioned many b value dispersion tensor imaging method of samplings; Through the relation that the signal to noise ratio of b value enforcement single prescan and different b values is followed; Just can be adaptive the multiple scanning number of times of selected each b value actual needs; Thereby reduced total sampling number, greatly reduced the time of sampling, improved the speed of dispersion tensor imaging.

[description of drawings]

Fig. 1 is the flow chart of the many b value dispersion tensor imaging method of samplings among the embodiment;

Fig. 2 is for descending single sweep signal intensity to calculate the flow chart of single sweep operation signal to noise ratio under the 2nd b value according to the following when said b value of single sweep operation noise of a said b value in many b value dispersion tensors imaging method of samplings shown in Figure 1.

[specific embodiment]

Describe below in conjunction with accompanying drawing and concrete embodiment.

As shown in Figure 1, a kind of many b value dispersion tensor imaging method of samplings may further comprise the steps:

S100, single sweep operation whole visual field under a b value, sampling obtains the following single sweep operation noise of a b value following single sweep signal intensity of a b value when.The b value is the disperse factor.The visual field is meant with the region-of-interest to be the center, the zone that coil can scan, for example, focus zone, internal organs zone or the like.During sampling, the b value is fixed on the value, coil carries out single sweep operation to whole visual field then, obtains single sweep signal intensity under the b value.

S200, according to a b value down the when specified b value of single sweep operation noise time repeatedly scan snr computation and obtain under the b value repeatedly scanning times.According to a said b value down the when specified b value of single sweep operation noise time repeatedly scan snr computation and obtain under the b value repeatedly that the formula of scanning times is:

$\frac{{\mathrm{SNR}}_1}{\sqrt{1}}=\frac{{\mathrm{SNR}}_{N1}}{\sqrt{N1}}$

Wherein, SNR ₁Be single sweep operation signal to noise ratio under the said b value, SNR _N1For a said b value repeatedly scans down signal to noise ratio, N1 is a scanning times repeatedly under the said b value.

S300, according to a b value down the single sweep operation noise when a b value time single sweep signal intensity calculate single sweep operation signal to noise ratio under the 2nd b value.In the present embodiment, a b value b ₁Be 500 seconds/every square millimeter, the 2nd b value b ₂It is 750 seconds/every square millimeter.As shown in Figure 2, step S300 comprises the steps.

S310 calculates single sweep signal intensity under the 2nd b value according to single sweep signal intensity under the b value.Because the process of disperse is exponential damping, the fitting formula of single sweep signal intensity does under the b value,

$S_1=S_0{e}^{-b_{1}D}$

Wherein, S ₁Be single sweep signal intensity under the said b value, S ₀Signal intensity when not having the disperse gradient, b ₁Be a said b value, D is a dispersion coefficient.In like manner, the fitting formula of single sweep signal intensity is under the 2nd b value:

$S_2=S_0{e}^{-b_{2}D}$

Wherein, S ₂Be single sweep signal intensity under the 2nd b value, S ₀Signal intensity when not having the disperse gradient, b ₂Be the 2nd b value, D is a dispersion coefficient.The formula that calculates single sweep signal intensity under the 2nd b value according to single sweep signal intensity under the b value is:

$\frac{\ln S_1-\ln S_0}{\ln S_2-\ln S_0}=\frac{-b_1}{-b_2}$

Wherein, b ₁Be a b value, b ₂Be the 2nd b value, S ₁Be single sweep signal intensity under the b value, S ₂Be single sweep signal intensity under the 2nd b value, S ₀Signal intensity when not having the disperse gradient.

S320 descends the relation of single sweep signal intensity to calculate single sweep operation signal to noise ratio under the 2nd b value according to following single sweep signal intensity of a b value and the 2nd b value.The formula that descends the relation of single sweep signal intensity under single sweep signal intensity and the 2nd b value to calculate the relation between the single sweep operation signal to noise ratio under the 2nd b value according to a b value is:

$\frac{S_1}{S_2}=\frac{{\mathrm{SNR}}_1}{{\mathrm{SNR}}_2}$

Wherein, S ₁Be single sweep signal intensity under the b value, S ₂Be single sweep signal intensity under the 2nd b value, SNR ₁Be single sweep operation signal to noise ratio under the b value, SNR ₂It is single sweep operation signal to noise ratio under the 2nd b value.

S400, according to the 2nd b value down when specified the 2nd b value of single sweep operation noise time repeatedly scan snr computation and obtain under the 2nd b value repeatedly scanning times.According to the 2nd b value down when specified the 2nd b value of single sweep operation noise time repeatedly scan snr computation and obtain under the 2nd b value repeatedly that the formula of scanning times is:

$\frac{{\mathrm{SNR}}_2}{\sqrt{1}}=\frac{{\mathrm{SNR}}_{N2}}{\sqrt{N2}}$

Wherein, SNR ₂Be single sweep operation signal to noise ratio under said the 2nd b value, SNR _N2For said the 2nd b value repeatedly scans down signal to noise ratio, N2 is a scanning times repeatedly under said the 2nd b value.

Above-mentioned many b value dispersion tensor imaging method of samplings; Through the relation that the signal to noise ratio of b value enforcement single prescan and different b values is followed; Just can be adaptive the multiple scanning number of times of selected each b value actual needs,, thereby reduced total sampling number; Greatly reduce the time of sampling, improved the speed of dispersion tensor imaging.

The above embodiment has only expressed several kinds of embodiments of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to claim of the present invention.Should be pointed out that for the person of ordinary skill of the art under the prerequisite that does not break away from the present invention's design, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection domain of patent of the present invention should be as the criterion with accompanying claims.

Claims (1)

1. the dispersion tensor of b value more than kind imaging method of sampling may further comprise the steps:

A1, under a b value single sweep operation whole visual field, sampling obtain a b value down the single sweep operation noise when a b value descend single sweep signal intensity;

A2, according to a said b value down the single sweep operation noise when time specified snr computation that repeatedly scans of a b value obtain under the b value repeatedly scanning times;

A3, according to a said b value down the when said b value of single sweep operation noise time single sweep signal intensity calculate single sweep operation signal to noise ratio under the 2nd b value;

A4, according to said the 2nd b value down the single sweep operation noise when time specified snr computation that repeatedly scans of the 2nd b value obtain under the 2nd b value repeatedly scanning times;

A b value described in the steps A 1 fitting formula of single sweep signal intensity down is:

$S_1=S_0{e}^{-b_{1}D}$

Wherein, S ₁Be single sweep signal intensity under the said b value, S ₀Signal intensity when not having the disperse gradient, b ₁Be a said b value, D is a dispersion coefficient;

Calculating under the b value repeatedly in the steps A 2, the formula of scanning times is:

$\frac{{\mathrm{SNR}}_1}{\sqrt{1}}=\frac{{\mathrm{SNR}}_{N1}}{\sqrt{N1}}$

Wherein, SNR ₁Be single sweep operation signal to noise ratio under the said b value, SNR _N1For a said b value repeatedly scans down signal to noise ratio, N1 is a scanning times repeatedly under the said b value;

Steps A 3 comprises the steps:

A31, according to a said b value down single sweep signal intensity calculate single sweep signal intensity under the 2nd b value;

A32, according to a said b value down the relation of single sweep signal intensity and said the 2nd b value time single sweep signal intensity calculate single sweep operation signal to noise ratio under said the 2nd b value;

The formula that calculates single sweep signal intensity under the 2nd b value in the steps A 31 is:

$\frac{\ln S_1-\ln S_0}{\ln S_2-\ln S_0}=\frac{-b_1}{-b_2}$

Wherein, b ₁Be a said b value, b ₂Be said the 2nd b value, S ₁Be single sweep signal intensity under the said b value, S ₂Be single sweep signal intensity under said the 2nd b value, S ₀Signal intensity when not having the disperse gradient;

The 2nd b value described in the steps A 31 fitting formula of single sweep signal intensity down is:

$S_2=S_0{e}^{-b_{2}D}$

Wherein, S ₂Be single sweep signal intensity under said the 2nd b value, S ₀Signal intensity when not having the disperse gradient, b ₂Be said the 2nd b value, D is a dispersion coefficient;

The formula that calculates the relation between the single sweep operation signal to noise ratio under said the 2nd b value in the steps A 32 is:

$\frac{S_1}{S_2}=\frac{{\mathrm{SNR}}_1}{{\mathrm{SNR}}_2}$

Wherein, S ₁Be single sweep signal intensity under the said b value, S ₂Be single sweep signal intensity under said the 2nd b value, SNR ₁Be single sweep operation signal to noise ratio under the said b value, SNR ₂Be single sweep operation signal to noise ratio under said the 2nd b value;

Calculating under the 2nd b value repeatedly in the steps A 4, the formula of scanning times is:

$\frac{{\mathrm{SNR}}_2}{\sqrt{1}}=\frac{{\mathrm{SNR}}_{N2}}{\sqrt{N2}}$

Wherein, SNR ₂Be single sweep operation signal to noise ratio under said the 2nd b value, SNR _N2For said the 2nd b value repeatedly scans down signal to noise ratio, N2 is a scanning times repeatedly under said the 2nd b value.

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