JPH0815439A - Blood flow measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] Completely non-invasive measurement of accurate blood flow without collecting blood. [Structure] The head of the subject 4 is scanned by the SPECT apparatus 1, and time-series data of the radioactivity concentrations of the target site and the reference site in the brain are obtained in the data collection memory 2. The arithmetic unit 3 obtains the time integrated value from these data, and calculates the blood flow volume of the target region by the approximation method from the time elapsed data and the integrated value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of nuclear medicine, and more particularly to a device for measuring blood flow in organs such as the brain.

[0002]

2. Description of the Related Art Assuming that the behavior of ¹²³ I-IMP (tracer) in the brain follows a two-compartment model as shown in FIG. 4, the following basic differential equation is established.

[Equation 1] Here, Ca (t) and Cb (t) are the arterial blood radioactivity concentration and brain tissue radioactivity concentration, respectively, whose half-life has been corrected,
K1 represents the local cerebral blood flow, and k2 represents the washout coefficient from the brain to the blood pool. Therefore, conventionally, for Cb (t), data is collected by dynamic measurement using an emission CT device such as a SPECT (single photon emission type computer tomography) device or a PET (positron emission type computer tomography) device, and Ca (T) was obtained by collecting blood from the artery and measuring it with a radiation detector such as a well counter, and based on these data, K1, k2
The above two parameters are calculated.

In this case, about 10 to 30 per measurement
Since it is necessary to perform frequent blood collection about once, the burden on patients and doctors is large, and therefore it is desired to be able to perform non-invasive measurement. From this point, conventionally, Ca (t) is created as a standard function, and the standard function is calibrated by calibrating the standard function with radioactivity concentration data obtained by collecting blood once for an actual subject. It has been proposed to obtain personal Ca (t) etc. (Masahiro Nashinaka, Hidehiro Iida,
Matsutaro Murakami "N-isopropyl-p- [ ¹²³ I] iodoamphetamine (
¹²³ I-IMP) and rotary gamma camera for regional cerebral blood flow quantification ”, Nuclear Medicine Vol. 29, No. 2 (1992) p263-26.
7).

[0004]

However, there is a problem that the burden on the patient and the doctor is large if blood is collected frequently as in the conventional case. On the other hand, the conventional method of reducing the number of times of blood sampling is merely a simple method, and does not accurately obtain the arterial blood radioactivity concentration different for each individual, but has a problem that an error due to individual difference occurs.

In view of the above, it is an object of the present invention to provide a blood flow measuring device capable of completely non-invasively performing a test without collecting blood and minimizing an error.

[0006]

In order to achieve the above object, in the blood flow measuring device according to the present invention, means for measuring the time course of the radioactivity concentration in the target area and the reference area of the subject, and these objects are provided. The radioactivity concentration value at each time point for the reference region and the reference region and the integrated value of the radioactivity concentration for the two regions from the start of measurement to each time point were obtained, and these data and known blood distribution constants were used. It is characterized in that it comprises a calculation means for calculating the blood flow volume in the target region by an approximation method.

[0007]

The time course of the radioactivity concentration in the target region and the reference region of the subject can be measured by the emission type CT device. When the basic differential equations for the attention area and the reference area that hold in the two-compartment model are integrated by time and linearized, the term of the arterial blood radioactivity concentration is common in the equations related to these two areas. The terms can be eliminated to derive an equation. The radioactivity concentration measured at each time point for the above two areas, and the 2 from the start of measurement to that time point
If the integral value of the radioactivity concentration for one region is applied to the above formula and a known blood distribution constant is used, the blood flow volume in the target region can be calculated by the approximation method.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, ¹²³ I-IMP was intravenously injected to the subject 4, and the SPECT device 1
Gives a dynamic measurement of the head. As a result, the ECT image 5 of the head as shown in FIG. 2 is obtained every time the time passes. This ECT image 5 shows the distribution of radioactivity concentration (count) in a predetermined cross section of the head of the subject 4, and such ECT images 5 are sequentially obtained every hour. The ECT image 5 is stored in the data collection memory 2.
The total sum of the count values of all pixels in each of the narrow area 6 of interest and the appropriate reference area 7 is stored for each time. That is, the radioactivity concentrations Cb (t) and Cb of the attention area 6 and the reference area 7 at a certain time t, respectively.
ref (t) is collected in the data collection memory 2. Since Cb (t) and Cbref (t) are collected at each time t, Cb (t) and Cbref (t) are curves that change with time as shown in FIG.

The arithmetic unit 3 receives these data Cb (t),
Using Cbref (t), a calculation for obtaining the blood flow volume K1 in the attention area 6 is performed. First, assuming that the behavior of the tracer in the brain complies with the two-compartment model, the basic differential equation represented by the above mathematical formula 1 holds for each of the attention area 6 and the reference area 7. In order to eliminate the differential terms of the basic differential equation for the attention area 6 and the reference area 7, both sides thereof are time-integrated under the initial condition Cb (0) = 0 to obtain the following equations 2 and 3.

[Equation 2]

(Equation 3) In these formulas

[Equation 4] Is the integrated value from the start of measurement of the radioactivity concentration in arterial blood to a certain time t,

(Equation 5) Is the integrated value from the start of measurement of the radioactivity concentration for the attention area 6 to a certain time t,

(Equation 6) Is the integrated value from the start of measurement of the radioactivity concentration for the reference region 7 to a certain time t.

Here, when Vd is a cerebral blood distribution constant, k2 = K1 / Vd, k2ref = K1ref / Vdre
f holds. Now, there is no problem even if it is assumed that Vd = Vdref, so if this is introduced,

Since Eq. 4 is common, the following Equation 7 can be derived by eliminating it.

(Equation 7)

From the equation 7, the data Cb (t),
Cbref (t),

[Equation 5],

It can be seen that it is possible to calculate K1 / Vd by the approximation method using the integrated value expressed by the following equation. Here, C1 / Vd is calculated by the linear least square method by plotting Cb (t) and Cbref (t) and their integrated values on a graph. First, both sides of Expression 7 are divided by Cbref (t) to obtain Expression 8 below.

(Equation 8) here,

[Equation 9] ,

[Equation 10] Then, the equation 8 becomes the following equation 11.

[Equation 11] This formula 11 shows a simple linear function. Therefore,
X (t) and Y (t) are obtained from Cb (t) and Cbref (t) at each t and their integrated values, and each point on the X (t) -Y (t) coordinates indicated by them is determined. Plot,
A straight line in which each of the points rides on one straight line is approximated. Then, since this straight line expresses the above-mentioned formula 11, it can be seen that the inclination thereof represents K1 / Vd. Therefore, if the above approximate straight line is obtained by the linear least squares method, K
1 / Vd is required.

On the other hand, the cerebral blood distribution constant Vd is almost determined by the tracer. That is, when the tracer is ¹²³ I-IMP, it is about 30 ml / g, and when H ₂ ¹⁵ O is about 0.9 ml / g. Then, by substituting the value of Vd into K1 / Vd obtained as described above, the blood flow K related to the attention area 6
1 will be required.

Cb (t), Cbref
The calculation device 3 performs calculation of the integrated value of (t), calculation of an approximate straight line by the linear least squares method, calculation of the inclination of the straight line, and calculation of the blood flow K1 using the known value of Vd. .

The above description relates to one embodiment, and various modifications can be made without departing from the spirit of the present invention. That is, here, the radioactivity concentration Cb of the brain tissue is
Although (t) is measured by the ring type or detector rotating type SPECT apparatus 1, other emission type CT apparatus such as a PET apparatus may be used. Further, the calculation algorithm of the blood flow K1 regarding the attention area 6 performed in the arithmetic unit 3 is not limited to the above. That is, the method of calculating K1 / Vd by the approximation method using Equation 7 is not limited to the linear least square method as described above. Other types of tracers can be used. Furthermore, it is needless to say that the method can be applied to blood flow measurement in organs other than the brain.

[0015]

As described above with reference to the embodiments, according to the blood flow measuring device of the present invention, the blood is not collected at all and the burden on the subject can be reduced and the burden on the doctor can be reduced. . Moreover, an error due to an individual difference does not occur, and an accurate blood flow measurement can be performed.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of the present invention.

FIG. 2 is a diagram showing an ECT image.

FIG. 3 is a graph showing a radioactivity concentration curve of brain tissue.

FIG. 4 is a schematic diagram of a two-compartment model.

[Explanation of symbols]

 1 SPECT Device 2 Data Collection Memory 3 Computing Device 4 Subject 5 ECT Image 6 Area of Interest 7 Reference Area

Claims (1)

[Claims] 1. A means for measuring the time course of radioactivity concentration in a target region and a reference region of a subject, and a radioactivity concentration value at each time point for these target region and reference region and from the start of measurement to each time point thereof. And an arithmetic means for calculating an integrated value of the radioactivity concentration in the two regions of the target region and calculating the blood flow volume of the target region by an approximation method using these data and a known blood distribution constant. Blood flow measuring device.