JP2973643B2 - Quantitative measurement of substances - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a quantitative measuring device materials using radiation, in particular those concerning the bone density quantitative equipment.

[0002]

2. Description of the Related Art As a method of quantifying a specific substance contained in an object from the intensity of radiation passing through the object, conventionally,
An energy difference method using radiation composed of two energy bands is used.

When an object is composed of three substances, a specific substance is quantified as follows. Here, a case of measuring an object including three substances A, B, and C shown in FIG. 3 will be described.

In order to use the energy difference method, radiation 4 having two kinds of energies E1 and E2 is irradiated.

The intensities I _X1 and I _X2 of the radiation 4 having two energies E1 and E2 after passing through the object at x shown in FIG. 3 are expressed by (Equation 1) and (Equation 2).

[0006]

(Equation 1)

[0007]

(Equation 2)

Intensities I _Y1 and I _Y2 after transmission at Y in FIG.
Is represented by (Equation 3) and (Equation 4).

[0009]

(Equation 3)

[0010]

(Equation 4)

Similarly, the transmitted intensities I _Z1 and I _{Z2 at} Z shown in FIG. 3 are expressed by ( _Equation 5) and (Equation 6).

[0012]

(Equation 5)

[0013]

(Equation 6)

However, μ _A1 , μ _A2 , μ _B1 , μ _B2 , μ _C1 ,
μ _C2 is the mass attenuation coefficient at the energies E 1 and E ₂ of the substances A, B and C, and I ₀₁ and I ₀₂ are the radiation intensities of the energies E 1 and E 2 irradiating the substance, ρ _A , ρ _B and ρ _C are the substances A,
The density of substances B and C, T _A , T _B , T _C , is the substance A,
It represents the thickness of B and C. T _C ′ and T _C ″ are represented by the following equations, respectively.

T _C ′ = T _C −T _A T _C ″ = T _C −T _{B The} energy difference calculation is performed so that the calculation result of the substance C becomes zero, and the density of the substance A 1 is obtained (Equation 1). ),
From the two equations (Equation 2), the density m _A per unit area of the material A1 by the energy difference method is obtained as (7).

[0016]

(Equation 7)

[0017] (7) (Equation 3), applying equation (4), m _A is 0, it can be seen that the density of only material A is obtained.

Similarly, the density m per unit area of the substance B2
_B is obtained by (Equation 8).

[0019]

(Equation 8)

Conventionally, a quantitative measurement of a substance in an object has been performed by the above method.

[0021]

However, in the above-mentioned conventional method, the calculation formula has to be changed for each substance. For this reason, when a plurality of substances are contained, there is a problem in that each calculation cannot be performed by a single calculation.

The present invention solves the above drawbacks.
An object of the present invention is to provide a quantitative measurement device capable of quantifying a plurality of substances by one calculation formula.

[0023]

In order to achieve this object, in the present invention, a substance is quantified by using a negative value calculated by the energy difference method.

[0024]

By using both the positive value and the negative value after the energy difference, a plurality of substances can be quantified by one calculation formula.

Although the details will be described later, for example, the result of the energy difference calculation according to (Equation 7) has a negative value for the portion including the substance B and a positive value for the portion including the substance A. Is carried out, the substance contained therein can be easily determined.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the case of an object composed of three kinds of substances as shown in FIG. 3, the operation can be performed as follows.

Energy E1, E transmitted through each part of the object
The difference calculation of (Equation 7) is performed for the two radiation intensities I ₁ and I ₂ . That is, the difference calculation is also performed on the transmission intensity of the portion that is supposed to contain the substance B by the equation (Equation 7).

For the portion containing the substance B, instead of ln (I _X1 / I ₀₁ ) and ln (I _X2 / I ₀₂ ) in (Equation 7),
Ln (I _Z1 / I ₀₁ ) obtained from (Equation 5) and (Equation 6),
Substituting ln (I _Z2 / I ₀₂ ) results in (Equation 9).

[0029]

(Equation 9)

In the above equation, when μ _B1 / μ _B2 is smaller than Rc, m _A ′ as a result of the difference indicates a negative value. In the part of the substance A, since (Equation 7) is an energy difference calculation formula for quantifying the substance A, the value after the difference calculation is positive.

Therefore, the result of the energy difference calculation according to (Equation 7) is a negative value for the portion including the substance B and a positive value for the portion including the substance A. Determination of contained substances can be easily performed.

Generally, in the energy range not including the k-absorption edge, the ratio of the low-energy attenuation coefficient to the high-energy attenuation coefficient increases as the effective atomic number increases. Therefore, when the energy difference result indicates a positive value, the part includes a substance having an atomic number or an effective atomic number higher than that of the erased substance (here, the substance C), and the part indicating a negative value includes It can be identified that a substance having a small atomic number or effective atomic number is included.

The density m of the substance B per unit area
_B is obtained by (Equation 10).

[0034]

(Equation 10)

As described above, the densities of a plurality of substances can be obtained by the same equation (Equation 7). Hereinafter, the present invention will be described in detail based on examples.

In this embodiment, a case where the amounts of human bone and fat are determined will be described. FIG. 1 is a sectional view of a human waist. As shown in FIG. 1, the waist of the human body has bones 11 and muscles 1.
2. It is assumed that it is composed of three substances, fat 13 and fat 13.

Then, transmission information of X-rays is measured by the measurement system shown in FIG. This measurement system includes an X-ray source 21, an X-ray line sensor 22, and an arithmetic unit 23,
By scanning the X-ray line sensor 22 in synchronism with 1, two-dimensional measurement can be performed.

A k-edge filter 24 is provided immediately below the X-ray source 21. The k-edge filter 24 is Gd
The fan beam X-ray 26 emitted from the X-ray source 21 is separated into two energies, and is irradiated on the measurement target 25. X-ray tube voltage is 1
In the case of 00 kV, the effective energy is 45 keV and 75 kV.
eV. The X-ray intensity of each energy was measured by scanning the X-ray line sensor 22 using the photon counting method.

Table 1 shows the measurement results of the count number of each part at each energy. For simplicity, only three points shown in FIG. 1 are shown in (Table 1). Point X measures the muscle and bone, point Y measures the muscle only, and point Z measures the X-ray intensity transmitted through the muscle and fat.

[0040]

[Table 1]

From this measurement result, the energy difference calculation for eliminating the muscles as a reference and calculating the density m _bone per unit area of the _bone was performed for all the regions. That is,
The substance C in (Equation 7) is a muscle, the substance A is a bone,
It was calculated m _A (m _bone) using the attenuation coefficients shown in (Table 2). Table 2 also shows the X-ray intensities I ₀ and Rc before transmission through the object used for the calculation.

[0042]

[Table 2]

[0043] indicates the units of m _A obtained by (Equation 7) in (Table 3). The density of bone per unit area is 1.143 g / cm ²
And a positive value.
It has become. At the point Z, a negative value was shown. It can be seen that this point includes a substance having a smaller attenuation coefficient ratio than muscle, that is, a substance having a smaller effective atomic number. (Table 4) shows the attenuation coefficient of fat and the attenuation coefficient ratio R, and (Table 5) shows the muscle, bone,
Indicates the effective atomic number of fat.

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

[Table 5]

Both the fat attenuation coefficient ratio and the effective atomic number are smaller than the muscle of the reference substance. Thereby, it can be identified that fat exists in the negative value area after the difference calculation processing. After the difference calculation processing, a negative value was shown, and the fat density per unit area in the portion where the fat was present was calculated by (Equation 10) for the portion where the fat exists. As a result, the density of the Z portion was 4.55
It was 29 g / cm ² , and the fat could be quantified.

As described above, according to the present embodiment, not only the bones contained in the human body but also fat can be simultaneously detected and quantified by using the negative value after the difference calculation processing. did it.

As described above, according to the present invention, by using the negative part of the difference processing calculation processing result, one calculation formula can be obtained.
An object of the present invention is to realize a substance quantitative measurement device capable of simultaneously identifying and quantifying a plurality of substances in an object .

[Brief description of the drawings]

FIG. 1 is a sectional view of an object to be measured in one embodiment of a measuring method of the present invention.

FIG. 2 is a configuration diagram of a measurement device embodying the present invention.

FIG. 3 is an explanatory view of the principle of the present invention.

[Explanation of symbols]

 Reference Signs List 1 substance A 2 substance B 3 substance C 4 radiation 11 bone 12 muscle 13 fat 21 X-ray source 22 X-ray line sensor 23 arithmetic unit 24 k-edge filter 25 measurement object 26 fan beam X-ray

Claims (2)

(57) [Claims] 1. An X-ray source, an X-ray sensor, and an arithmetic unit
Comprising the X transparency information of an object to be measured with radiation of two or more energy or energy range
Measured by the line sensor, using said transmission information of the radiation
Identify and quantify the substances that make up the object with a computing device
In the substance quantitative measurement device, when the object is composed of three or more types of substances whose atomic number or effective atomic number is three or more, after a difference calculation process for eliminating the specific substance based on the specific substance among the substances, identification of at least two substances by the determination of the positive and negative atomic numbers or effective atomic number for the material using the code, at the same time before the quantitative
Quantitative measurement device for substances characterized by being operated by a computer
Place . 2. The apparatus for quantitatively measuring a substance according to claim 1, wherein the substance constituting the object to be measured is muscle, bone, or fat, which is a soft tissue.