JPH0379673B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to regional cerebral blood flow.
This invention relates to a CT device that can measure blood flow (r-CBF).

[Technical background of the invention and its problems]

Knowledge regarding blood flow in each part of the subject is
It has great clinical significance because it allows us to understand the function of that part. As blood flow observation, r-CBF measurement by the inhalation method has been performed for a long time using radioisotopes (RI). Methods for monitoring the tracer concentration in arterial blood in the brain r-CBF measurement method include a blood sampling method in which blood is collected from the artery over time to measure the tracer concentration in the blood, and a mass spectrometer is used to measure the tracer concentration in exhaled breath. There are mass spectrometry methods that take measurements, and shuttle methods that take tomographic images of the head and neck alternately and set an ROI in the carotid artery.

However, the blood sampling method causes a great deal of pain to the subject, the measurement process is complicated, and the measurement accuracy is relatively poor. The mass spectrometry method is
It requires an expensive mass spectrometer, and furthermore, it changes the tracer concentration over time [hereinafter abbreviated as Cb(t)] in the tissue of the subject. ] and temporal changes in tracer concentration in arterial blood [hereinafter abbreviated as Ca(t)]. ] It is difficult to maintain temporal synchronization with
Furthermore, since the shuttle method cannot measure Ca(t) and Cb(t) at the same time on the same slice plane, a time lag occurs. Furthermore, sufficient measurement accuracy cannot be achieved due to the thickness of the carotid artery.

[Purpose of the invention]

This invention has been made in view of the above circumstances, and it is possible to measure Ca(t) and Cb(t) simultaneously on the same slice surface, easily and accurately without causing pain to the subject. The purpose of this invention is to provide a CT device that can accurately measure cerebral blood flow.

[Summary of the invention]

The outline of this invention for achieving the above object is as follows:
An exhalation tube is placed in the tomography area, intersecting the slice plane of the subject, through which tracer-containing exhaled breath is discharged after being absorbed by the subject, and based on the data obtained from tomography, the It has an image reconstruction device that reconstructs an image including a tomographic image of a specimen and a tomographic image of an exhalation tube, and an image analysis device that measures local cerebral blood flow based on image data output from the image reconstruction device. It is characterized by this.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, an X-ray CT device for measuring r-CBF, which is an embodiment of the present invention, has an X-ray CT device section and a tracer inhalation device section.

The X-ray CT device section has an imaging hole 3 into which the head of a subject 2 lying on a bed top 1 can be inserted, and an X-ray tube (not shown) that rotates around the head of the subject 1. A gantry 5 that performs tomography on the slice plane 4 by irradiating X-rays, a data collection device 6 that collects data output from a detector (not shown) in the gantry 5 and compiles it into a large number of projection data. an image reconstruction device 7 that reconstructs a tomographic image of the slice plane 4 based on projection data output from the data acquisition device 6;
Based on image data of multiple tomographic images in chronological order output from the image reconstruction device
(t) and Cb(t);
The tomographic image constructed by the image reconstruction device 7 and/or analyzed by the image analysis device 8
It is configured to include an image display device 9 that displays Ca(f) and Cb(f).

The tracer inhaler section is a closed system as a whole in order to reuse the tracer, and the tracer inhaler section is a closed system as a whole in order to reuse the tracer.
a mixed gas tank 12 that mixes oxygen (containing gas) and oxygen supplied from an oxygen cylinder 11; and a mixed gas tank 12 that monitors the oxygen concentration in the mixed gas tank 12 and maintains the oxygen concentration in the mixed gas tank 12 constant. an oxygen concentration monitoring device 14 that automatically controls a control valve 13 that adjusts the amount of oxygen supplied;
A mask 15 that covers the nose and mouth of the subject 2, and a one-way check valve for supplying a mixed gas into the mask 15 and preventing the exhalation of the subject 2 from being mixed in, are provided near the mask 15, The mixed gas tank 1
2 and the mask 15; a buffer bag 17 attached to the mask 15 and buffering the mixed gas flow from the intake tube 16; while supplying it to the subject 2.
A one-way check valve for preventing backflow of exhaled air is provided near the mask 15, and is connected between the mask 15, the mixed gas tank 15, and the mixed gas tank 12 via a carbon dioxide adsorption device 18, which will be described later. and an exhalation tube 19 that penetrates the slice surface 4, and a carbon dioxide adsorption device 18 that adsorbs and removes carbon dioxide from exhaled breath.

Next, the operation of the X-ray CT apparatus for r-CBF measurement having the above configuration will be described.

The mixed gas with a constant oxygen concentration monitored by the oxygen concentration monitoring device 14 is passed through the exhalation tube 16.
and through the mask 15, the mixed gas tank 12
from the inside of the subject 2. In the subject 2, the tracer in the gas mixture is absorbed into the blood in the lungs, and then the tracer carried by the blood is distributed in the brain tissue. Additionally, tracers that have circulated in brain tissue are excreted during exhalation. The exhaled air containing the tracer is introduced into the exhaled air tube 19, and after the carbon dioxide in the exhaled air is adsorbed and removed by the carbon dioxide adsorption device 18, it is stored in the mixed gas tank 12.

On the other hand, the head of the subject 2 is placed in the imaging hole 3, and tomography of the head of the subject 2 is performed on the slice plane 4. Data output from a detector (not shown) in the gantry 5 is collected by a data collection device 6 and compiled into a large number of projection data. The projection data is output to the image reconstruction device 7. Based on a large amount of projection data obtained by the image reconstruction device 7 when the X-ray tube rotates around the body axis,
As shown in FIG. 2, an image is reconstructed according to the time series t ₀ , t ₁ . . _. t 0 . This image includes a tomographic image 20 of the head of the subject 2 and a tomographic image 21 of the exhalation tube 19. In FIG. 2, Pa(t) is the average CT value at time t when a circular or rectangular ROI is set in the tomographic image 21 of the exhalation tube 19, and Pbij(t) is the time of the tomographic image 20. This is the average CT value at t. Time-series image data regarding the images reconstructed by the image reconstruction device 7 is output to the image analysis device 8.
Ca(t) and Cbij(t) are analyzed by. Here, Ca(t) and Cbij(t) are the first
It can be expressed by the formula and the second formula.

Ca(t)=α{Pa(t)−Pa(o)} ……(1) Cbij(t)=Pbij(t)−Pbij(o) ……(2) However, Pa(o), Pbij( o) is the CT value before tracer inhalation, and α is a proportional coefficient determined from the hematocrit value of blood or the CT value of collected blood. Ca obtained from time series image data
An example of (t) and Cbij(t) is shown in FIG. The obtained Ca(t) and Cbij of each pixel (i, j)
The r-CBF of each pixel (i, j) is calculated by the image analysis device 8 by analyzing two types of time series data (t). Note that r-CBF is usually analyzed based on the following Fick principle.

(Fitske's principle) Cbij(t)=λijkij∫ ^T ₀ Ca(t) exp[−kij(T−t)]dt……(3) Or, d/dTCbij(T)=kij{λijca (T)− Cij(t)} ...(4) where, Cbij(T): Tracer concentration in a certain tissue (corresponding to pixel (i, j) in the tomographic image) at time T λij: Tracer concentration in a certain tissue (corresponding to pixel (i, j) in the tomographic image) (i, j)
kij: distribution coefficient kij at a certain tissue (pixel (i, j) in a tomographic image)
Rise rate Ca(T): Arterial blood tracer concentration at time T r-CBF(fij)=λij・kij...(5) Calculations for analysis are based on the integral form of the third equation above, This can be done by an appropriate method such as the differential form of the fourth equation or curve fitting using the least squares method. By performing this analysis for each (i, j), λij, kij, f
(ij) is calculated. The calculated λij, kij, f(i,
j), a tomographic image 20 of the head of the subject 2, and a tomographic image 21 of the expiratory tube 19 are displayed on the image display device 9. In addition to being displayed as numerical values on the cathode ray tube of the image display device 9, λij, kij, and f(i, j) may be displayed as a functional image that is modulated in brightness and expressed as light and shade. Because functional images contain functional information such as regional cerebral blood flow, they can provide new information in addition to the anatomical information provided by regular X-ray CT images, making them extremely useful for clinical diagnosis. It is beneficial for

Although one embodiment of this invention has been described in detail above, this invention is not limited to the above embodiment, and it goes without saying that it can be implemented with appropriate modifications within the scope of the gist of this invention. Nor.

Although the CT device in the above embodiment was an X-ray CT device, the CT device in the present invention can be a nuclear medicine diagnostic device, a positron, or other CT device.

In addition, as shown in FIG. 4A, the subject's head 2
2, rotate the upper arm 23 and scan the head 22 and the upper arm 23 with the slice plane 24 to obtain a tomographic image 25 of the head 22 and an image of the brachial artery 26 as shown in FIG. , image analysis device 8
However, during tomography, artifacts may occur in the tomographic image due to body movement of the upper arm, making accurate r-CBF measurement impossible.

〔Effect of the invention〕

According to the configuration of the present invention, the following effects can be achieved.

There is no need to separately prepare an expensive measuring device such as a mass spectrometer.

It is non-invasive to the subject, and local cerebral blood flow can be easily measured without causing pain to the subject.

The temporal changes in RI concentration in the subject tissue and the temporal changes in RI concentration in arterial blood can be measured simultaneously on the same slice plane, and the same number of measurement sample points can be obtained at the same time. Can be measured with high precision.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram showing an image reconstructed by the image reconstruction device in the embodiment, and FIG. 3 is an explanatory diagram showing an image reconstructed by the image analysis device in the embodiment. Calculated Ca
(t) and Cb(t), FIG. 4A is an explanatory diagram showing a state in which the subject's head and upper arm are tomographically photographed on the same slice plane, and FIG. 4B is the FIG. 2 is an explanatory diagram showing a tomographic image obtained by tomography. 2... Subject, 4... Slice surface, 7... Image reconstruction device, 8... Image analysis device, 19... Expiratory tube.

Claims (1)

[Claims] 1. Based on the data obtained from tomography and an exhalation tube placed within the tomography area, intersecting the slice plane of the test subject through which exhaled breath containing tracer is discharged after being absorbed by the test subject,
An image reconstruction device that reconstructs an image including a tomographic image of a subject and a tomographic image of an exhalation tube; and an image analysis device that measures local cerebral blood flow based on image data output from the image reconstruction device. A CT device for measuring local cerebral blood flow, characterized by comprising: