CN107456225A - A kind of cerebral blood flow (CBF) partial volume effect bearing calibration - Google Patents

Abstract

The present invention relates to a kind of cerebral blood flow (CBF) partial volume effect bearing calibration, the purpose of the present invention is exactly to carry out partial volume correction using the CBF values obtained in ASL technologies, and accurate algorithm is provided for clear and definite AD diagnosis.Using the CBF values obtained in ASL and T1 values as inputting, the CBF values of full brain white matter of brain, ectocinerea and cerebrospinal fluid are drawn by PVE algorithms.The CBF values carried out according to this method after PVE corrections are divided into two groups of white matter of brain, ectocinerea pixel values.Compared with full brain CBF values, result of calculation is more accurate, is advantageous to the diagnosis and analysis of clinic.

Description

A Correction Method for Partial Volume Effect of Cerebral Blood Flow

technical field

The invention relates to the field of data processing, in particular to a method for correcting cerebral blood flow partial volume effects.

Background technique

Cerebral blood flow (CBF) is the blood flow that flows through a certain amount of brain tissue vascular structure per unit time. It is defined as the amount of blood delivered to a unit mass of human tissue per unit time, and the unit is ml/100g/min. The change of CBF is an early sign of brain activation and an important sign to evaluate the health status of the brain. It is the main basis for the diagnosis and treatment of cerebrovascular diseases such as Alzheimer's disease, cerebral infarction, cerebral hemorrhage, aneurysm and congenital arterial and venous malformations. Currently, methods for measuring cerebral blood flow mainly include PET, SPECT, and MRI techniques. With the continuous improvement of nuclear magnetic resonance imaging technology, nuclear magnetic arterial spin labeling sequence (Artery Spin Label, ASL) technology as a completely non-invasive new blood perfusion technology has been gradually used in the measurement of CBF. When using the CBF value obtained by magnetic resonance ASL technology to study Alzheimer's disease (AD), compared with cognitively normal elderly people, AD patients have different degrees of brain atrophy, especially the medial temporal lobe atrophy, while brain atrophy The difference in degree will affect the image registration, because most ASL images have a layer spacing of 3-4mm, and there are a lot of mixed voxels of gray matter and white matter. If the cerebral blood flow calculation method of gray matter or white matter is used for these voxels, it will inevitably cause errors, so it is necessary to perform partial volume correction (Partial VolumeCorrection, PVE) on these regions to obtain accurate CBF values.

Contents of the invention

The purpose of the present invention is to use the CBF value obtained in the ASL technique to perform partial volume correction, so as to provide a more accurate algorithm for the diagnosis of AD. The CBF value and T1 value obtained in ASL were used as input, and the CBF value of white matter, gray matter and cerebrospinal fluid of the whole brain was obtained by PVE algorithm. Due to the low pixel value of CBF, at the boundary of gray matter, white matter and cerebrospinal fluid of the whole brain, one pixel value may contain various components such as white matter, gray matter and cerebrospinal fluid, while cerebral blood flow is in each component (white matter, gray matter, cerebrospinal fluid) The value of the difference is very large, so after the partial volume correction, the CBF value of the boundary area is more accurate. The main formula is as follows:

CBF _pve = CBF/(P _GM *ΔM _GM + P _WM *ΔM _WM +P _CSF *ΔM _CSF ).

In the above formula, CBF is the cerebral blood perfusion value before correction, and P _GM , P _WM and _PCSF represent the probability maps of gray matter, white matter and cerebrospinal fluid. ΔM _GM , ΔM _WM and ΔM _CSF represent arterial spin-labeled perfusion-weighted signals of cerebral gray matter, white matter, and cerebrospinal fluid, where the value of ΔM _CSF is 0, because the arterial self-selected labeling signal of cerebrospinal fluid is almost 0. The CBF _gray value of an adult is about 3 times that of the WM _CBF . So the above equation can be simplified to:

CBF _pve = CBF/ (P _GM *3+ P _WM ).

Use this simplified formula to perform PVE correction on ASL data.

The present invention is achieved through the following technical solutions:

A method for correcting partial volume effect of cerebral blood flow, characterized in that it comprises the following steps:

Step 1) Obtain the cerebral blood flow value, cerebral gray matter value and cerebral white matter value of the whole brain through the detection results of the NMR arterial spin labeling sequence;

Step 2) Set the gray matter value of the area whose gray matter value is less than or equal to 0.25 to 0, and the obtained area whose gray matter value is not 0 is GM; set the white matter value of the area whose white matter value is less than or equal to 0.25 to 0, the area where the obtained white matter value is not 0 is WM;

Step 3) For each value point in the area GM, correct it according to the following formula

CBF _gray =CBF/(GM _gray +0.33*GM _white )

Among them, CBF _gray is the correction result of cerebral blood flow value in the gray matter of the point, CBF is the value of cerebral blood flow in the point, GM _gray is the value of gray matter in the point, and GM _white is the value of white matter in the point ;

For each value point in the area WM, the correction is performed according to the following formula

CBF _white =CBF/(WM _white +3*WM _gray )

Among them, CBF _white is the correction result of the cerebral blood flow value in the white matter of the point, CBF is the value of cerebral blood flow in the point, WM _white is the value of the white matter of the point, and WM _gray is the value of the gray matter of the point ;

Step 4) According to the value of CBF _gray , the brain gray matter brain blood flow map is made, and the white matter brain blood flow map is made according to the value of CBF _white .

Compared with the prior art, the present invention has the following advantages:

According to this method, the CBF value after PVE correction is divided into two groups of pixel values of brain white matter and brain gray matter. Compared with the whole brain CBF value, the calculation result is more accurate, which is beneficial to clinical diagnosis and analysis.

Description of drawings

Figure 1 is a CBF map of the whole brain;

Figure 2 is the corrected gray matter CBF map.

detailed description

Example 1

This method can be realized by matlab programming, and the matlab program is as follows:

function FG_PVE_correction_for_perfusiondata(Imgs, Grays, Whites, smooth_kernel)

Define a PVE function with four function variables (whole brain, white matter, gray matter, smooth kernel parameters)

sub=[1,2,3,4,5,6,7,….,n] (read image serial numbers one by one, n is the data number entering the program)

for k=1:x (x represents the number of data entering the program)

n=sub(k) (n represents the number of the data)

S=num2str(n); (change from character variable to numeric variable)

Imgs=strcat('local path\','means',S,'.img') Get the whole brain pixel value

Grays=strcat('local path'\','c1s',S,'.img') Get gray matter pixel values

Whites=strcat('local path\','c2s',S,'.img') Get white matter pixel values

smooth_kernel=[2 2 2]; Define smooth kernel number is 2

for i=1:size(Grays,1) read brain data

Vmat=spm_vol(Imgs(i,:)); Assign the whole brain pixel value to the Vmat variable

V=spm_read_vols(Vmat); Read the Vmat variable into the V variable

GM=spm_read_vols(spm_vol(Grays (i,:))); Gray matter data is assigned to GM

WM=spm_read_vols(spm_vol(Whites(i,:))); White matter data is assigned to WM

GM(find(GM<=0.25))=0; If the gray matter value is less than or equal to 0.25, set the gray matter to 0

WM(find(WM<=0.25))=0; If the white matter value is less than or equal to 0.25, set the white matter to 0

V21=zeros(size(V)); Define the V21 variable space size equal to V (brain space size), assign 0

V22=zeros(size(V)); Define the V22 variable space size equal to V (brain space size), assign 0

V21(find(GM))=V(find(GM))./(GM(find(GM))+0.4*WM(find(GM)));

V21 (gray matter)=gray matter/(gray matter+0.33*white matter)

V22(find(WM))=V(find(WM))./(WM(find(WM))+2.5*GM(find(WM))); V22(white matter)=white matter/(white matter+3*gray matter )

Vmat.fname=deblank(PVE_gray_imgs(i,:));

spm_write_vol(Vmat,V21);

Assign the value of V21 to PVE_gray_imgs

Vmat.fname=deblank(PVE_white_imgs(i,:));

spm_write_vol(Vmat,V22);

Assign the value of V22 to PVE_ white _imgs

end

fprintf ('\n-----PVE correction is done!......\n')

The GUI interface prompts that the PVE calibration has been completed

end

Figures 1 and 2 show the correction effect of this method. The CBF values after PVE correction according to this method are divided into two groups of cerebral blood flow images: white matter and gray matter. Figure 2 is the corrected gray matter cerebral blood flow map. Compared with the whole brain CBF value, the calculation result is more accurate, which is beneficial to clinical diagnosis and analysis.

Claims (1)

1. A cerebral blood flow partial volume effect correction method, is characterized in that, comprises the steps: Step 1) Obtain the cerebral blood flow value, cerebral gray matter value and cerebral white matter value of the whole brain through the detection results of the NMR arterial spin labeling sequence; Step 2) Set the gray matter value of the area whose gray matter value is less than or equal to 0.25 to 0, and the obtained area whose gray matter value is not 0 is GM; set the white matter value of the area whose white matter value is less than or equal to 0.25 to 0, the area where the obtained white matter value is not 0 is WM; Step 3) For each value point in the area GM, correct it according to the following formula CBF _gray =CBF/(GM _gray +0.33*GM _white ) Among them, CBF _gray is the correction result of cerebral blood flow value in the gray matter of the point, CBF is the value of cerebral blood flow in the point, GM _gray is the value of gray matter in the point, and GM _white is the value of white matter in the point ; For each value point in the area WM, the correction is performed according to the following formula CBF _white =CBF/(WM _white +3*WM _gray ) Among them, CBF _white is the correction result of the cerebral blood flow value in the white matter of the point, CBF is the value of cerebral blood flow in the point, WM _white is the value of the white matter of the point, and WM _gray is the value of the gray matter of the point ; Step 4) According to the value of CBF _gray , the brain gray matter brain blood flow map is made, and the white matter brain blood flow map is made according to the value of CBF _white .