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Method for measuring liver magnetic resonance crosswise relaxation rate R2* parameter

A technology of transverse relaxation rate and measurement method, which is applied in the field of magnetic resonance transverse relaxation parameter R2* measurement, can solve the problems of poor repeatability, inaccuracy, and large difference in operation, and improve accuracy, reduce noise, and repeatability Good results

Inactive Publication Date: 2013-07-24
SOUTHERN MEDICAL UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In this method, since magnetic resonance images are always noisy, especially in the case of high noise and high iron content, the T2* value calculated by using a single exponential fitting model pixel by pixel is inaccurate, resulting in inaccurate extraction of liver parenchyma
Moreover, due to the influence of partial volume effect, the T2* distribution of liver parenchyma and non-hepatic parenchyma may not have a clear boundary in the histogram, and it is difficult to accurately determine the threshold in this case
The selection of the threshold is also subjective, and the results calculated by different operators will vary greatly. Not only the transverse relaxation rate R2* is inaccurate, but also the operation repeatability is poor.

Method used

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  • Method for measuring liver magnetic resonance crosswise relaxation rate R2* parameter
  • Method for measuring liver magnetic resonance crosswise relaxation rate R2* parameter
  • Method for measuring liver magnetic resonance crosswise relaxation rate R2* parameter

Examples

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Embodiment 1

[0038] A method for measuring a liver magnetic resonance transverse relaxation rate R2* parameter, comprising the following steps in sequence:

[0039] (1) Using a multi-echo gradient echo sequence to obtain a magnetic resonance liver image, and drawing the region of interest of the whole liver on the obtained magnetic resonance liver image. The area of ​​interest in the whole liver can be drawn manually, or automatically drawn by program control, or first automatically drawn by the program and then fine-tuned by manual drawing to improve the accuracy.

[0040] (2) Using the non-local mean filtering method to denoise the obtained magnetic resonance liver image and calculate the R2* map of the whole liver;

[0041]Specifically, the non-local mean filter method is used to denoise the magnetic resonance liver image to obtain the denoised magnetic resonance liver image; and then obtain the gray level of each pixel in the region of interest of the whole liver of the denoised magnet...

Embodiment 2

[0051] A method for measuring a liver magnetic resonance transverse relaxation rate R2* parameter comprises the following steps in sequence.

[0052] (1) Using a multi-echo gradient echo sequence to obtain a magnetic resonance liver image, and drawing the region of interest of the whole liver on the obtained magnetic resonance liver image.

[0053] The magnetic resonance liver image obtained by the multi-echo gradient echo sequence method has the characteristics of strong applicability, easy operation, low cost, and fast acquisition speed.

[0054] It should be noted that the method of obtaining the magnetic resonance liver image is not limited to the multi-echo gradient echo sequence method in this embodiment, and methods such as acquiring multiple times of a single echo can also be used.

[0055] (2) The non-local mean filtering method is used to denoise the obtained magnetic resonance liver image. Specifically, the following parameters are used in the non-local filtering me...

Embodiment 3

[0069] A method for measuring a liver magnetic resonance transverse relaxation rate R2* parameter takes human liver as a measurement object, and specifically includes the following steps.

[0070] Step 1: Acquire 12-echo liver magnetic resonance images, and the imaging parameters are set as follows: the echo time is respectively selected as 0.93, 2.27, 3.61, 4.95, 6.29, 7.63, 8.97, 10.4, 11.8, 13.2, 14.6 and 16 ms, and the repetition time is is 200 ms, the slice thickness is 10 mm, the matrix size is 64×128, and the flip angle is 20 o .

[0071] Step 2: On one of the echo liver magnetic resonance images, take a ROI of an appropriate size (such as 40 pixels) in the black background area, and use the following formula ( ), calculate the standard deviation of the background noise.

[0072]

[0073] Step 3. Manually draw the ROI of the whole liver along the edge of the liver image, such as image 3 shown. It should be noted that the method of drawing the region of interest...

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Abstract

A method for measuring a liver magnetic resonance crosswise relaxation rate R2* parameter includes the steps: (1) obtaining a magnetic resonance liver image, and drawing a full-liver region-of-interest; (2) obtaining a magnetic resonance liver image which is denoised, re-obtaining a gray level of each pixel within the full-liver region-of-interest of the magnetic resonance liver image which is denoised, enabling the gray level of each pixel and echo time to be matched on a first moment model formula (I) of a single-index model under the influences of non-central Chi noise, and then obtaining a full-liver R2* image; (3) dividing a R2* value of the full-liver region-of-interest into two types, enabling the two types to respectively correspond to liver parenchyma and blood vessels, and re-obtaining a liver parenchyma region-of-interest; and (4) a calculating gray level average value and echo time of the liver parenchyma region-of-interest of each echo image and enabling the gray level average values and the echo time to be matched on the formula (1), and then obtaining a final liver parenchyma R2* value. The method can improve precision of the crosswise relaxation rate R2* parameter and is good in repeatability.

Description

technical field [0001] The invention relates to the technical field of magnetic resonance transverse relaxation parameter R2* measurement, in particular to a method for measuring the liver magnetic resonance transverse relaxation rate R2* parameter. Background technique [0002] Magnetic resonance transverse relaxation rate R2* value (that is, the reciprocal of transverse relaxation time T2*) measurement technology, as a non-invasive means to evaluate the iron content of tissues and organs, especially human tissues and organs, has become the main image of liver iron overload study diagnostic methods. In the study of liver iron content, the R2* value of the liver is usually measured first, and then the existing calibration function is used to convert R2* into iron content to evaluate the iron content. [0003] So far, there are two main methods for measuring the R2* value of the liver. [0004] The first one is to calculate the average gray value in the small ROI of each ...

Claims

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Application Information

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IPC IPC(8): G06T5/00
Inventor 冯美燕冯衍秋陈武凡
Owner SOUTHERN MEDICAL UNIVERSITY
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