X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
2001-03-08
2002-07-30
Bruce, David V. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S901000
Reexamination Certificate
active
06426987
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to Japanese Patent Application No. 2000-163899 filed on Jun. 1, 2000, whose priority is claimed under 35 USC § 119, the disclosure of which is incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an imaging system in a medical field, particularly to an imaging system which can construct an image from transverse images (tomograms) taken by a CT scanner about an imaging object having a periodically changing shape like a heart.
2. Description of the Related Art
An X-ray computer tomography system (hereinafter referred to as a CT scanner) has been used for taking medical images in a medical field.
The CT scanner is a system which irradiates a diagnosing subject with X-ray to collect projection data of the X-ray transmitted through the diagnosing subject. On the basis of the projection data, an image processing is carried out to reconstruct a transverse image (also referred to as a tomogram) of visceral organs of the diagnosing subject.
Furthermore, by processing a number of the reconstructed transverse images so as to be arranged in the direction perpendicular to the transverse plane at uniform intervals to form a stack, a cross sectional image (herein after referred to as an MPR (multi-planer reconstruction) image) is reconstructed. With three-dimensional information further collected on the basis of the MPR image, production of a three-dimensional image of the diagnosing subject is also carried out.
For producing such a three-dimensional image, a large amount of the transverse images must be collected with a high speed and high precision. For this purpose, a helical type CT scanner (hereinafter referred to as a helical scanning CT) has been recently used which collects data of a helical cross sectional plane.
The helical scanning CT is used for producing a transverse image or a three-dimensional image used for examining and diagnosing a function of a heart. The image of the heart is obtained as being in a diastolic phase or systolic phase. However, a heart repeats a diastole and systole with a certain personally different characteristic period (about 60 beats/minute). Therefore, no plurality of transverse images can be obtained about the heart in the diastolic phase, for example, only at one time scanning.
Thus, in general, an electrocardiograph is provided to select the transverse images supposed to be those in the diastolic or systolic phase in synchronism with data signal obtained from the electrocardiograph. From thus selected transverse images, there are produced the MPR images or the three-dimensional images in the diastolic or systolic phase.
FIG. 1
is a block diagram showing an outline of a configuration of a related synchronization system of an electrocardiograph with a helical scanning CT system.
The synchronization system comprises a helical scanning CT
130
, an electrocardiograph
141
outputting data of an electrocardiogram of a diagnosing subject, an electrocardiogram synchronization unit
140
analyzing electrocardiogram data of a diagnosing subject to transmit a synchronization signal to the helical scanning CT, and a computer carrying out an image processing.
In addition, the computer comprises a control unit
100
comprising a CPU and associated units, a storage unit
110
, a displaying unit
120
, and an inputting unit
121
.
In the storage unit
110
, there are stored collected signals
111
, transverse images
112
, MPR images
113
, and three-dimensional images
114
. The collected signals
111
are those of projection data obtained by the helical scanning CT, transverse images
112
are constructed from the collected signals
111
, MPR images
113
are produced from the transverse images
112
, and three-dimensional images
114
are produced on the basis of the MPR images
113
.
The control unit
100
is provided with various functions such as a signal collection function
101
, a transverse image construction function
102
, an MPR image production function
103
, and a three-dimensional image production function
104
. The signal collection function
101
is for driving the helical scanning CT
130
and storing the collected signals
111
of the projection data in the storage unit
110
. The transverse image construction function
102
is for constructing the transverse images
112
using the stored collected signals
111
. The MPR image production function
103
and a three-dimensional image production function
104
are for producing the MPR images
113
and the three-dimensional images
114
using the transverse images
112
and the MPR images
113
, respectively.
In such a related system used for constructing the image of a heart in a diastolic or systolic phase, data collection processing and imaging processing in the control unit
100
were generally carried out by either one of the following.
(1) Processing of driving the helical scanning CT in synchronism with a data signal of the electrocardiograph and obtaining projection data when the heart shows a little motion.
FIG. 2
is a waveform diagram showing a typical data signal of an electrocardiograph.
In general, in a waveform of the data signal of the electrocardiograph, it is well known that a wave form in the range between the T wave and the R wave exhibits a little variation. Here, for allowing the projection data to be obtained within the range, the electrocardiogram synchronization unit
140
transmits a trigger signal to the helical scanning CT
130
at a specified timing. The helical scanning CT
130
receiving the signal carries out a series of processing for obtaining projection data in a followed certain period.
Therefore, in the storage unit
110
, only the projection data in the range with a little variation from the T wave to the R wave are stored as the collected signals
111
.
After the scanning of the helical scanning CT
130
is over, the control unit
100
constructs a plurality of the transverse images
112
on the basis of the collected signals
111
.
Furthermore, there is carried out processing of selecting the transverse images from a plurality of the transverse images
112
in synchronism with the data signal of the electrocardiograph. The selected transverse images
112
, for example, those in a period corresponding to the systolic phase of the heart (a specified period after the T wave). On the basis of the selected images
112
, processing is further carried out for producing the MPR images
113
or 3 dimensional images
114
.
Also about the transverse images
112
in the diastolic phase, processing is carried out for selecting transverse images in a period corresponding to the diastolic phase (a specified period before the R wave).
(2) Processing of obtaining the projection data by the helical scanning CT without in synchronism with a data signal of the electrocardiograph, constructing transverse images on the basis of the obtained data, and selecting images corresponding to those in the diastolic or systolic phase of the heart with a measurer comparing the constructed transverse images and the waveform of the data signal of the electrocardiograph.
Here, the electrocardiogram synchronization unit
140
is not used. Namely, the control unit
100
separately stores the data signal obtained from the electrocardiograph
141
and the projection data obtained from the helical scanning CT
130
in the storage unit
110
as the collected signals
111
.
After this, the control unit
100
constructs the axial CT images (transverse images) on the basis of the projection data. The constructed axial CT images include those in both the diastolic and systolic phases.
There, the axial CT images and the waveform of the data signal of the electrocardiograph are displayed on a displaying unit or printed out. From thus displayed or printed out images and waveform, images corresponding to those in the diastolic or systolic phases within the range from the T wave to the R wave are manually selected in order by the measurer with correspondence of e
Azemoto Shogo
Hamada Seiki
Naito Hiroaki
Nakamura Hironobu
Yamamoto Shuji
Bruce David V.
Kanagawa & Co., Ltd.
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