CN111481224B

CN111481224B - Bone/bone marrow diffuse lesion tumor load measurement method and system

Info

Publication number: CN111481224B
Application number: CN202010363157.6A
Authority: CN
Inventors: 罗亚平; 潘青青; 李方
Original assignee: Peking Union Medical College Hospital Chinese Academy of Medical Sciences
Current assignee: Peking Union Medical College Hospital Chinese Academy of Medical Sciences
Priority date: 2020-04-30
Filing date: 2020-04-30
Publication date: 2023-05-09
Anticipated expiration: 2040-04-30
Also published as: CN111481224A

Abstract

A bone/bone marrow diffuse lesion tumor load measurement method comprises a first step S1, obtaining PET/CT images; step S2, setting a first threshold value, and extracting an image with the CT value larger than the first threshold value as a first area; a third step S3 of setting a second threshold value and amplifying the first region by taking the second threshold value as a reference to obtain a second region; a fourth step S4 of shrinking the second region along the outline of the bone tissue by taking the second threshold value as a reference to obtain a third region; and a fifth step S5, extracting PET metabolic parameters, and calculating tumor load based on the third region. In the invention, the delineation of the ROI is realized by extracting the bone/bone marrow region by adopting the CT value based on the bone density, so that the measurement of the diffuse lesion tumor load of the bone/bone marrow is realized; can accurately extract bone tissues and bone marrow tissues, and is not affected by focus SUV value and target cost ratio.

Description

Bone/bone marrow diffuse lesion tumor load measurement method and system

Technical Field

The present invention relates generally to the fields of nuclear medicine and molecular imaging, and more particularly to a method and system for measuring bone/bone marrow diffuse lesion tumor burden.

Background

Methods for assessing tumor burden include structural imaging such as: CT, MRI, etc., and also functional imaging such as: PET. Especially, PET and CT are combined together, so that information on both tumor functions and structures can be provided, and the PET and CT combined type tumor diagnosis and treatment device has an important effect on diagnosis and treatment of diseases.

SUV (Standard uptake value) is the most common semi-quantitative parameter of PET when using PET for tumor burden detection. Furthermore, other PET parameters such as TLG focal total glycometabolism), MTV (tumor metabolic volume), etc. are further generated based on SUV. Wherein, MTV is defined by researchers or the volume of a tumor focus with increased metabolism is automatically sketched by a computer. The MTV of each lesion is multiplied by the average SUV value in the delineated volume and then the product of all lesions is added to obtain the TLG. MTV and TLG are widely used in studies of tumor burden assessment of solid tumors and partial hematological tumors.

Since MTV is the volume that delineates the lesion of the metabolically enhanced tumor, a threshold-based approach is generally adopted when determining the boundary of the ROI (region of interest), i.e., a lesion with SUV greater than a threshold is delineated into the ROI, and the determination of the threshold can be further classified into a fixed SUV absolute value approach and a fixed SUV relative value approach. SUVs above 2.5 are the most commonly used threshold in fixed absolute methods, which have the problem that the ROI cannot include a part of tumor tissue with lower metabolism and SUVs below 2.5, and in addition for lesions with abnormally elevated metabolism, tumor volume may be overestimated due to "extravasation effects". The most commonly used threshold in fixed SUV relative value method is 40% -42%, the main disadvantage is heterogeneity of tumor metabolic distribution, and the small focus volume can be overestimated by adopting fixed ratio because of low target cost ratio.

Therefore, the measurement of MTV and TLG is only suitable for single-focus or multi-focus lesions, and the lesion extraction can not be performed for diffuse bone/bone marrow-related lesions due to the wide and diffuse distribution of the lesions if the sketching mode based on SUV, namely MTV and TLG, is continuously adopted.

Disclosure of Invention

In order to solve the problems, the invention provides a bone/bone marrow diffuse lesion tumor load measurement method, which comprises the following steps of, a first step S1, obtaining PET/CT images; step S2, setting a first threshold value, and extracting an image with the CT value larger than the first threshold value as a first area; a third step S3 of setting a second threshold value and amplifying the first region by taking the second threshold value as a reference to obtain a second region; a fourth step S4 of shrinking the second region along the outline of the bone tissue by taking the second threshold value as a reference to obtain a third region; and a fifth step S5, extracting PET metabolic parameters, and calculating tumor load based on the third region.

According to one embodiment of the present invention, the second threshold is set according to the first threshold, and the relation is b=αa+c, where B is the second threshold; a is a first threshold; c is the width constant of bone marrow tissue; alpha is a correlation coefficient.

According to one embodiment of the invention, the first threshold value is in the range of CT values 200HU to 240HU.

According to one embodiment of the invention, the first threshold is: CT value 220HU.

According to one embodiment of the present invention, the second threshold value has a value ranging from: 0.5 to 3cm.

According to one embodiment of the present invention, the second threshold value is set as follows: 1cm.

According to one embodiment of the present invention, the fourth step S4 further includes adjusting the third region to remove the non-bone region having an abnormally high CT value.

According to another aspect of the present invention, there is provided a bone/bone marrow diffuse lesion tumor burden measurement system, comprising, a first module 1 for acquiring PET/CT images; a second module 2, configured to set a first threshold, and extract an image with a CT value greater than the first threshold as a first region; a third module 3, configured to set a second threshold, and amplify the first area with the second threshold as a reference, to obtain a second area; a fourth module 4, configured to shrink the second region along the outline of the bone tissue with reference to a second threshold value, to obtain a third region; a fifth module 5 for extracting PET metabolic parameters, calculating tumor burden based on the third region.

According to one embodiment of the present invention, the system further comprises a correction module, wherein the correction module is used for adjusting the third area and removing the non-bone area with the abnormally increased CT value.

In the invention, the delineation of the ROI is realized by extracting the bone/bone marrow region by adopting the CT value based on the bone density for the image of the diffuse increase of the bone/bone marrow community, so that the load measurement of the diffuse lesion tumor of the bone/bone marrow is realized.

The bone tissue region is extracted by setting the first threshold value, and the bone tissue region is enlarged and then reduced by setting the second threshold value, so that the bone tissue and the bone marrow tissue can be accurately extracted, and the influence of focus SUV value and target cost ratio is avoided.

Drawings

FIG. 1 is a schematic illustration of the steps of a method for measuring the burden of a bone/bone marrow diffuse tumor;

FIG. 2 is a schematic diagram of a bone/bone marrow diffuse tumor burden measurement system;

FIG. 3 is a diagram of steps for extracting a ROI in one embodiment.

Detailed Description

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein reference numerals refer to the components and techniques of the present invention so that the advantages and features of the present invention may be more readily understood in the proper environment for practice. The following description is a specific embodiment of the present claims, and other specific implementations not explicitly described in connection with the claims also fall within the scope of the claims.

Fig. 1 shows a schematic step diagram of a method for measuring the load of a bone/bone marrow diffuse tumor.

As shown in fig. 1, a method for measuring the load of bone/bone marrow diffuse lesion tumor comprises a first step S1 of acquiring PET/CT images; step S2, setting a first threshold value, and extracting an image with the CT value larger than the first threshold value as a first area; a third step S3 of setting a second threshold value and amplifying the first region by taking the second threshold value as a reference to obtain a second region; a fourth step S4 of shrinking the second region along the outline of the bone tissue by taking the second threshold value as a reference to obtain a third region; and a fifth step S5, extracting PET metabolic parameters, and calculating tumor load based on the third region.

The PET/CT is formed by organically combining two devices, namely the PET and the CT, and uses the same examination bed and the same image processing workstation, which are common in the prior art, and the invention is not repeated.

The PET/CT image refers to an image that includes all of the scanned area, and typically a computer automatically conforms the image to the contours of the human body.

The first threshold is set for extracting a region where bone tissue is located in a PET/CT image. Because the human skeleton density is higher than other tissue densities, a certain CT value can be set to distinguish the bone tissue from other tissues, namely, the region where the bone tissue is located is marked or extracted, so that a bone tissue region with the CT value higher than a first threshold value, namely, a first region, is obtained. The first region is typically a high density region bounded by a bone tissue contour.

The second threshold is set for processing the first region, and limits the range in which the edge of the first region where the bone tissue is located is widened. The first region is enlarged as defined by the second threshold for inclusion in the region of bone marrow tissue. The size of the second threshold can be adjusted according to the setting condition of the first threshold and the gap between the cancellous bone in the first area. Since the bone marrow is located in the cortical bone and between the cancellous bone, the first region is enlarged first, i.e. when the bone tissue contour is enlarged outwards, the region where the bone marrow tissue is located is covered, forming the second region. Thus, the second region includes a bone tissue region, a bone marrow region, and a bone tissue lateral region.

After the bone tissue and bone marrow are included, the second region is reduced based on a second threshold value to conform to the outline of the bone tissue, and the covered bone marrow region is not changed to obtain a third region. The third region excludes other tissue regions outside the bone tissue contour relative to the second region.

And finally, taking the obtained third region as the ROI, extracting metabolic parameters and calculating tumor burden. For example, based on the delineated ROI, the volume, TLG, SUV are automatically calculated _max And SUV (sports utility vehicle) _mean Etc.

In the present invention, although the defined ROI may encompass part of normal bone/bone marrow tissue, the effect on the final TLG is minimal since normal bone/bone marrow tissue has little radioactive uptake. Furthermore, since the invention is an ROI extracted based on CT values, it is theoretically applicable to all PET imaging agents and is not affected by lesion SUV values, target-to-cost ratios.

In the invention, the ROI of bone and marrow tissues is extracted from PET/CT image mainly by utilizing the characteristic that the bone density of human body is higher than that of other tissues. Typically, cancellous bone has a CT value greater than 250HU and cancellous bone is slightly lower than cortical bone. The CT value is set to be in the range of 200HU to 240HU, and the computer is utilized to automatically extract the tissues conforming to the CT value, so that the obtained main bone tissues are mainly obtained.

For example, by setting a CT value greater than 220HU (if there is severe osteoporosis, it can be set to 200 HU), the computer automatically extracts the tissue that matches the CT value, and marks the obtained region, i.e., the first region.

According to one embodiment of the invention, the first threshold is set as: CT value 220HU. When the value is 220HU, the obtained image is accurate in covering bone tissues, and a good foundation is determined for subsequent expansion and contraction.

According to one embodiment of the present invention, the second threshold is set according to the first threshold, and the relation is b=αa+c, where B is the second threshold; a is a first threshold; c is a correlation constant, related to bone marrow tissue width; alpha is a correlation coefficient and is a variable. The first and second thresholds are non-linearly related.

When the first region is enlarged, the second threshold may suitably take a smaller value, for example 0.5cm, when the first threshold is adapted to allow the first region to more accurately cover bone tissue. When the first threshold is high, so that an area thereof covers only a part of the bone tissue, the second threshold may suitably take a large value, e.g. 3cm. The invention preferably leaves 1cm, and on the premise of fully covering bone marrow tissues, the coverage of other tissues outside bones is reduced as much as possible, and the difficulty of image processing is reduced.

When the third region is obtained, it is usual that the third region further includes a non-bone region included in the ROI due to abnormal increase of the CT value, such as calcification, a metal implant, etc., and the third region is also required to be adjusted in order to achieve the purpose of precisely defining the ROI. According to one embodiment of the invention, manual adjustments may be made to remove areas that are significantly remote from bone tissue.

Fig. 2 shows a schematic diagram of a bone/bone marrow diffuse tumor burden measurement system.

As shown in fig. 2, a bone/bone marrow diffuse lesion tumor load measurement system includes a first module 1 for acquiring PET/CT images; a second module 2, configured to set a first threshold, and extract an image with a CT value greater than the first threshold as a first region; a third module 3, configured to set a second threshold, and amplify the first area with the second threshold as a reference, to obtain a second area; a fourth module 4, configured to shrink the second region along the outline of the bone tissue with reference to a second threshold value, to obtain a third region; a fifth module 5 for extracting PET metabolic parameters, calculating tumor burden based on the third region.

In the present invention, each of the first to fifth modules 1 to 5 may be composed of hardware loaded with a computer program, each of which has a corresponding function, and processes the acquired PET/CT image to calculate the tumor load. The modules may be combined and separated according to the functions described above, and the present invention is not limited thereto.

Examples

Fig. 3 shows a legend for each step of extracting the ROI.

The bright color portion of the upper diagram in fig. 3 is a selection area, which is more suitable for recognition for convenience of explanation, and the selected area in the upper diagram is highlighted in the lower diagram in fig. 3.

(a) PET MIP figures showing diffuse increases in bone marrow uptake;

(b) A whole-body ROI;

(c) Extracting a bone ROI;

(d) Expanding the ROI outwardly;

(e) The ROI is scaled down inwardly and manually trimmed to obtain the ROI, which includes all bone and bone marrow tissue.

The method comprises the following specific steps:

1. on the basis of the graph a, selecting all scanning areas as ROIs by using rectangular frames, and automatically conforming the scanning areas to human contours by a computer to obtain a graph b;

2. setting a CT value as 220HU on the basis of the graph b, and automatically extracting a bone ROI by a computer to obtain a graph c;

3. expanding the ROI 1cm outwards, which ROI already includes all bone and bone marrow tissue, resulting in map d;

4. shrinking the ROI inwards by 1cm to enable the contour of the ROI to conform to the contour of the skeleton, so as to obtain a graph e;

5. manually fine-tuning to remove non-bone tissues with increased CT values, including calcification, metal, calculus and the like;

6. obtaining the finally extracted bone and bone marrow tissue ROI, adjusting the analysis interface to the PET part, and calculating the metabolic parameters of the ROI.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Claims

1. A method for measuring the load of bone/bone marrow diffuse lesion tumor, which is characterized by comprising the following steps: tumor burden is measured based on PET metabolic parameters in PET/CT images, including,

a PET/CT image acquisition step (S1) of scanning a portion including bones by using a PET/CT device to acquire a PET/CT image;

a bone tissue region extraction step (S2) of setting a first threshold value according to bone density, and extracting a bone tissue region having a CT value greater than the first threshold value from the PET/CT image as a first region;

a region enlarging step (S3) of setting a second threshold according to the gap of the cancellous bone, enlarging the first region by taking the second threshold as a reference, and enlarging the outline of the bone tissue to cover the bone marrow tissue to obtain a second region;

a region shrinking step (S4) of shrinking the second region along the outline of the bone tissue by taking the second threshold value as a reference to obtain a third region;

and a tumor burden calculation step (S5) of extracting PET metabolic parameters in the PET/CT image from the third region and calculating a tumor burden.

2. The method according to claim 1, characterized in that: the second threshold is set according to the first threshold, and the relation is B=alpha A+C,

wherein B is a second threshold;

a is a first threshold;

c is the width constant of bone marrow tissue;

alpha is a correlation coefficient.

3. The method according to claim 1, characterized in that: the range of the first threshold is CT values 200HU to 240HU.

4. A method according to claim 3, characterized in that: wherein the first threshold is: CT value 220HU.

5. The method according to claim 1, characterized in that: the value range of the second threshold is as follows: 0.5 to 3cm.

6. The method according to claim 5, wherein: wherein, the value of the second threshold is: 1cm.

7. The method according to claim 1, characterized in that: the fourth step S4 further comprises adjusting the third region to remove non-bone regions with abnormally increased CT values.

8. A bone/bone marrow diffuse lesion tumor burden measurement system, characterized by: tumor burden is measured based on PET metabolic parameters in PET/CT images, including,

a PET/CT device (1) for scanning a portion containing bones to obtain a PET/CT image;

a bone tissue region extraction module (2) for setting a first threshold according to bone density, and extracting a bone tissue region with a CT value greater than the first threshold from the PET/CT image as a first region;

the region amplifying module (3) is used for setting a second threshold according to the gap of the cancellous bone, amplifying the first region by taking the second threshold as a reference, and expanding the outline of the bone tissue to cover the bone marrow tissue to obtain a second region;

the region shrinking module (4) is used for shrinking the second region along the outline of the bone tissue by taking the second threshold value as a reference to obtain a third region;

and a tumor load calculation module (5) for extracting PET metabolic parameters in the PET/CT image from the third region and calculating tumor load.

9. The system according to claim 8, wherein: the correction module is used for adjusting the third area and removing the non-bone area with abnormally increased CT value.