JPS62112538A - Evaluation of bone - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a bone evaluation method. More specifically, the present invention involves determining the bone density pattern by measuring the X-ray intensity of the bone obtained by X-ray imaging of the cancellous bone, or determining the bone density pattern from the cancellous bone by photon absorptioniometry. The present invention relates to a bone evaluation method that evaluates cancellous bone by determining a density pattern and Fourier transforming the waveform spectrum.

<Prior Art> Human bones are classified into cortical bone and cancellous bone. Cortical bone is a dense bone tissue, typically found in the long bone shafts of limbs, and takes a pipe-like shape. Cancellous bone is bone tissue distributed in a network called trabeculae, and is located at the epiphyses of long bones, vertebrae 2 carpal bones, @
It is seen in bones, talus and other bones. Compared to cortical bone, cancellous bone has a larger area of bone tissue in contact with soft tissue, including the vascular system, and is therefore characterized by rapid bone turnover and rapid changes due to bone lesions or treatment.

The MD method is known as a method for evaluating cortical bone, that is, the growth state of cortical bone, the degree of aging, and the type of bone lesions such as osteoporosis and osteomalacia [bone metabolism, Vol. 13, pp. 187-195 (1980): Bone Metabolism, Vol. 14, pp. 91-104 (1981), etc.]. As an improved method of the MD method, the ellipse model method [Handbook of Bone Morphometric Measurement, Vol. 5, pp. 36-46 (1985)] is known.

A method for evaluating cancellous bone requires a method of examining and evaluating changes in the trabecular bone from plain X-ray photographs of cancellous bone. In other words, the trabeculae of cancellous bone are distributed according to the stress distribution applied to the bone, with thick trabeculae that support the body weight (main trabeculae) and thin trabeculae that connect them (secondary trabeculae). However, when bone mass decreases due to bone diseases such as osteoporosis, there is a regularity in that the accessory trabeculae are resorbed first, and the main trabeculae are relatively well preserved. Therefore, as a method for determining the degree of bone atrophy from plain X-ray photographs using this regularity, the Jikei University classification is used for the vertebrae, the Singh classification is used for the femoral neck, and the classification is used for the calcaneus. For cal canea 1ind
ex et al. “Osteoporosis (Basic and Clinical),” Takuo Fujita et al.

p331-337. Kyowa Kikaku Tsushin S, 58.11. Published by: The Journal of Bone and Joint-+1- J, Bone and Joint
Joint 5urlJ, ) Volume 65B, No.
2.195-198 (1983): J, Bon
e andJoint Surg, Volume 52, 45
7 (1970)] is known.

<Problems to be Solved by the Invention> However, all of these methods of determining the degree of bone atrophy from plain X-ray photographs are based on visual inspection of plain X-ray photographs, and are therefore lacking in objectivity. It is not accurate enough to deal with changes in lesions. Therefore, it is desired to develop a more objective and quantitative bone evaluation method for cancellous bones such as the calcaneus and vertebrae.

Means for Solving the Problems As a result of intensive research into objective and quantitative evaluation methods for cancellous bone, the present inventors have determined that the X-ray density of cancellous bone obtained by X-ray imaging of cancellous bone Measure the density pattern of the bone to obtain the degree pattern of the bone, or obtain the density pattern of the bone using photon absorption geometry from the cancellous bone, Fourier transform the density pattern to obtain the power spectrum, and then determine the density pattern of the cancellous bone based on the power spectrum. The present invention was completed by discovering that cancellous bone can be evaluated objectively and quantitatively by analyzing the trabecular bone of the patient and evaluating the bone.

That is, the present invention provides bone X-ray imaging obtained by X-ray imaging of cancellous bone.
The Ii1 degree pattern of the bone is determined by measuring the line yA degree, or the density pattern of the bone is determined from the cancellous bone using photon absorption geometry, and the density pattern of the cancellous bone is determined based on the power spectrum obtained by Fourier transform. This is a bone evaluation method characterized by analyzing the trabecular bone of the bone and evaluating the bone.

In the present invention, first, X-ray imaging of cancellous bone is performed.
Measure the line density to find the bone density pattern, or use a photon absorption saw from cancellous bone to find the bone opening pattern.

Cancellous bones include the calcaneus, the vertebrae, and the long carpal bones.

The epiphyseal end of the tarsal bone is suitable. These 2FIJ trabecular bones are X-rayed, and the X-ray image is taken 1Q. The X-ray density of the bone obtained by X-ray imaging is measured to determine the bone density pattern. The density pattern can be determined in the same manner as, for example, the conventional MD method.

In other words, the shading degree of the X-ray image is, for example, 2 with a height of 1 mm.
Measure with an X-ray image of a 0 step (minimum height 1 mm, maximum height 20 mm) aluminum staircase or aluminum slope using a meter. The obtained shading degree is converted and corrected to the number of steps of the aluminum stairs to obtain a density pattern. Alternatively, the bone density pattern can be determined by reading the X-ray image of the bone together with the X-ray image of the aluminum stairs and aluminum slope using a television camera.

When reading the X-ray density of the bone obtained by X-ray imaging in order to obtain the density pattern, it is preferable to read it perpendicularly to the main trabecular bone of the cancellous bone.

This is because by reading in a manner perpendicular to the main trabeculae, a strength pattern that best reflects the main trabeculae of cancellous bone can be obtained. This will be explained using the calcaneus as an example. FIG. 1 schematically shows an X-ray photograph of the calcaneus.

In order to obtain a waveform spectrum that best reflects the main trabecular bone of the calcaneus, connect the center points of A and B of the X-ray photograph and the center points of C and D, and measure the center part of straight line a, for example 10
The density pattern is determined by reading the shading degree of the mm section. In this case, the density pattern that best reflects the main trabecular bone is shown in FIG.

On the other hand, the bone density pattern can also be determined from cancellous bone by photon absorptiometry. Photon absorptiometry is a method that uses gamma rays instead of X-rays and measures and quantifies the amount of gamma rays that have passed through bone with a detector [Xience, No. 142
Vol., p. 23G (1963)], in this method, a cross section of cancellous bone is skimmed with gamma rays, and the number of counts of comma rays that have passed through the bone is plotted as an image as shown in FIG.

Next, the density pattern is Fourier transformed to obtain a power spectrum.

To perform Fourier transformation, the density pattern may be directly Fourier transformed, but for example, if the maximum value of the density pattern is 1. The Fourier transform may be performed after converting so that the minimum value becomes O, or after removing the DC component of the density pattern. Fourier transform transforms the density pattern into a periodic function f (
X), the Fourier series O f (x) = 1/2ao + Σ(Ancosnx +B
nsinnx ) n=1 to obtain the Fourier coefficient An, 8n6, and then C
It is necessary to obtain Cn (power spectrum) from n=n+n]'. These operations can use computer fast Fourier transforms. The power spectrum has a value that reflects the increase and decrease of the trabecular bone of the cancellous bone.

In Figure 3, the straight line a in Figure 2 is slightly translated,
The density patterns of a 10 mm area were found 10 times (it is preferable to find many density patterns.) Each of these density patterns was Fourier transformed, each Cn value was found, and the sum of these was found. be. Also, in order to find the density pattern of the i omm part, 2
56 density data are read (it is preferable to read as much data as possible). Figure 3 shows the power spectrum (CD, solid line) from the density pattern of the calcaneus of a healthy person and the senile bone phase. The power spectrum of stimulation (Cn, wavy line) is shown. As can be seen from this figure, the cn value differs between healthy subjects and osteoporosis patients around n=10.

Therefore, by performing Fourier transformation from the density pattern, obtaining the 0 mouth value, and comparing and examining a specific Cn value, for example, the C1o value, it is possible to analyze the trabecular bone of cancellous bone, and to determine the type of bone lesion, the degree of progression, etc. can be evaluated.

In addition, in order to make the evaluation from the power spectrum more objective, for example, the ratio of the sum of the power spectra from n=5 to n=20 and the sum from n=40 to n=127 is calculated, and this ratio is calculated. Bones can also be evaluated by comparing them. That is, in the case of senile osteoporosis, n=5 to n=20
The sum of the power spectra from n-40 to n = 1
The ratio to the sum of up to 27 shows a considerably lower value than that of healthy subjects.

On the other hand, bones can be evaluated more objectively and quantitatively by combining the power spectrum obtained from the density pattern and the bone density fraction A5 obtained by the conventional MD method.

<Effects of the Invention> The present invention provides a method for evaluating cancellous bone. According to the method of the present invention, by evaluating the bone of the calcaneus in particular, the condition of the bone can be objectively evaluated more accurately. Therefore, the present invention is of great significance.

<Example> Example 5 An X-ray image of the calcaneus of a 55-year-old female patient with senile osteoporosis was obtained. From this X-ray image, draw an auxiliary line a as shown in Figure 1, read the X-ray opacity at the center of this auxiliary line a 1 0 mm by densitometry, and determine the bone density pattern in Figure 2 at 1q. . A similar operation is auxiliary
Translate a slightly and perform -C'IO times to create a density pattern (
It was.

These) Nomaro patterns are each Fourier transformed and c
The n value was determined, these cn values were summed, and the result of Fourier transformation was shown in a graph as shown in FIG. Similarly, cn values from the calcaneus of healthy subjects were determined.

As is clear from FIG. 3, the power spectrum values of senile osteopathia patients around n=10 are lower than those of healthy individuals. In addition, the ratio of the sum of the power spectra up to n=20 and the sum from n=40 to n=127 is 0.07 for patients with senile osteopathy, and 0.12 for healthy people. Ta. This shows that bones can be evaluated using the power spectrum obtained by Fourier decomposition of the waveform spectrum.

[Brief explanation of drawings]

FIG. 1 shows an X-ray photograph of the calcaneus. Second
The figure shows a total density pattern obtained from an X-ray photographic image of the calcaneus, and FIG. 3 shows a power spectrum obtained by Fourier transformation of the density pattern.

Claims (1)

[Claims] 1. Obtain the bone density pattern by measuring the X-ray density of the bone obtained by taking X-rays of the cancellous bone, or obtain the bone density pattern from the cancellous bone by photon absorptiometry, and calculate the density pattern. A bone evaluation method characterized by analyzing the trabecular bone of cancellous bone and evaluating the bone based on a power spectrum obtained by Fourier transformation.