Patent Publication Number: US-2010121192-A1

Title: Method for imaging blood vessel, system for imaging blood vessel and program for imaging blood vessel

Description:
TECHNICAL FIELD 
     The present invention relates to a method for imaging blood vessels, a system for imaging blood vessels, and a program for imaging blood vessels. 
     BACKGROUND ART 
     Along with diversified lifestyles, progress of global aging, and diversified diet, arteriosclerosis has been progressing also among young people in recent years. Also, the number of patients receiving long-term therapy has been increasing due to vascular diseases such as myocardial infarction, cerebral infarction, and cerebral hemorrhage caused by arteriosclerosis. Mechanical integrity of vascular system, that is, flexibility of blood vessels (low rigidity and great breaking strain) is important in order to prevent the diseases. 
     A conventional method for measuring mechanical integrity of blood vessels in a noninvasive manner employs a pulse wave velocity measurement (PWM), blood vessel wall thickness measurement (intima-media thickness (IMT)) or the like as an arteriosclerosis examination. An elastic wave propagating through blood vessels is employed for the pulse wave velocity measurement because the propagation velocity of the elastic wave is proportional to an elastic coefficient of blood vessel. Further, the inner wall of blood vessel becomes gruel-like and if this state progresses, the inner wall expands. As a result, the blood vessel wall IMT increases and the inner diameter of the blood vessel decreases. The IMT (intima-media thickness) is examined at the first stage of the carotid echo examination. 
     Since the distance between two points used in the pulse wave velocity measurement is relatively great (for example, about ⅓ of the body height) when measuring these physical quantities, the measurement result takes an average value of measured lengths. In other words, it has been difficult to associate the progress status of locally occurred arteriosclerosis with the propagation velocity. For the blood vessel wall thickness measurement, special technique and knowledge are required for clear blood vessel imaging and wall thickness determination. Further, in recent years an acceleration pulse wave calculated from the 2nd order differential of a temporal change in blood stream of a fingertip or the like optically, but there is poor physical basis in which the arteriosclerosis can be measured from a change in blood stream near terminal blood vessels. Furthermore, a difference could be detected in PWM, IMT, acceleration pulse wave or the like when the arteriosclerosis was significantly advanced. Moreover, it is difficult to directly associate these measurement values with a rupture pressure of blood vessel hardened. 
     Patent Document 1 and Patent Document 2 do not disclose any technical feature for measuring a dynamic deformation behavior in a short time when the dynamic deformation behavior is measured for each measurement site in artery blood vessels. 
     Patent Document 1: Japanese Laid-Open Patent Publication No. 2005-185575 
     Patent Document 2: Japanese Laid-Open Patent Publication No. 2005-270351 
     DISCLOSURE OF THE INVENTION 
     Changes occur in diameter of an artery along with a pulsatile flow caused by dilatation and contraction of the heart.  FIG. 10(   a ) and  FIG. 10(   b ) show a state in which the diameter of a carotid artery K changes from upstream toward downstream along with a pulsatile flow. However, when the inner wall of blood vessel changes in its nature and arteriosclerosis (increase in rigidity) occurs due to local increase in IMT for aging and adult diseases, the change in diameter along with the pulsatile flow causes less variation. Further, the arteriosclerosis may locally occur and a blood vessel in a three-layered structure is a material that exhibits a strong viscoelastic character in terms of material science. Thus, the rigidity defined in a physiological blood pressure variation region at rest (generally on the order of 70 to 140 mmHg) and a dynamic deformation behavior at a high pulsation speed (stress test) are measured and compared with each other, which gives an important indicator. 
     However, the technique for imaging a carotid artery blood vessel and for measuring deformability based on the conventional method has been unable the problem of measuring the above in a short time. 
     It is an objective of the present invention to provide a blood vessel imaging system, a blood vessel imaging program, and a blood vessel imaging method capable of remarkably reducing stress on a test subject when the rigidity defined in a physiological blood pressure variation region at rest and the dynamic deformation behavior at a high pulsation speed (stress test) are measured and compared with each other. 
     In order to solve the problems, according to one aspect of the present invention, there is provided a blood vessel imaging system comprising an ultrasonograph, a moving body, control means, position information input means, storage means, image processing means, and image generation means. The moving body integrally moves a group of ultrasonic transducers along a row direction, the ultrasonic transducers being arranged two-dimensionally, that is, along a column direction and along the row direction, and including a plurality of column-directional array ultrasonic transducers for creating a tomographic echo image. The control means repeats intermittent movement control for the moving body within a shorter distance than a row pitch of the ultrasonic transducers along the row direction for each of a plurality of predetermined periods. The position information input means receives position information on a stop position of the moving body. The storage means stores a two-dimensional image and the position information on the stop position in association with each other, the two-dimensional image being generated by making original image information, which is obtained by the ultrasonic transducers within the plurality of predetermined periods, two-dimensional in the ultrasonograph. The image processing means performs three-dimensional image processing based on the two-dimensional image and the position information, or performs temporal changing of a three-dimensional image, that is, four-dimensional image processing based on the two-dimensional image, the position information, and temporal information on the plurality of predetermined periods. The image generation means generates at least one image from among the images of a maximum diameter, a minimum diameter, and the difference between the maximum diameter and the minimum diameter for each measurement site in an artery blood vessel, that is, for each stop position on the basis of the image information subjected to the image processing in the image processing means. 
     According to this configuration, when the rigidity defined in a physiological blood pressure variation region at rest and the dynamic deformation behavior at a high pulsation speed (stress test) are measured and compared with each other, a stress on a test subject is remarkably reduced on the examination. 
     Preferably, the blood vessel imaging system further comprises heartbeat information input means for receiving heartbeat information. In this case, the control means employs a heartbeat period based on the heartbeat information as the predetermined period. According to this configuration, the heartbeat period can be used as the predetermined period to reliably acquire information on the maximum diameter and the minimum diameter of an artery blood vessel along with a heartbeat at a measurement site. 
     Preferably, the control means stops intermittent drive of the moving body when the total movement distance of the intermittently-driven moving body becomes equal to or greater than the row pitch of the ultrasonic transducers. With this configuration, since the intermittent drive of the moving body stops when the total movement distance of the intermittently-driven moving body becomes equal to or greater than the row pitch of the ultrasonic transducers, it is possible to efficiently measure the necessary sites in artery blood vessels. In other words, if the intermittent drive of the moving body does not stop when the total movement distance becomes equal to or greater than the row pitch of the ultrasonic transducers, unnecessary measurement is made, which may be inefficient. 
     Preferably, the blood vessel imaging system further comprises calculation means for calculating an elastic modulus of a measurement site on the basis of the difference between the maximum diameter and the minimum diameter for each measurement site in an artery blood vessel, that is, for each stop position and a previously input blood pressure at rest. According to this configuration, the elastic modulus of the measurement site is obtained on the basis of the difference between the maximum diameter and the minimum diameter for each measurement site in an artery blood vessel and the previously input blood pressure at rest, thereby obtaining deformability (hardness, arteriosclerosis) of the measurement site. 
     Preferably, the moving body comprises an ultrasonic probe having a plurality of ultrasonic transducers arranged along the row direction and the column direction. In this case, the ultrasonic probe comprises a concave face corresponding to a surface shape of the cervical region, and the plurality of ultrasonic transducers are arranged on the concave face. According to this configuration, the plurality of ultrasonic transducers are arranged along the row direction and along the column direction, respectively, on the concave face corresponding to the surface shape of the cervical region in the ultrasonic probe, thereby providing a blood vessel imaging system suitable for a carotid artery blood vessel of the cervical region. 
     According to another aspect of the present invention, there is provided a blood vessel imaging program for working a computer to function as control means, position information input means, storage means, image processing means and image generation means. The control means performs movement control for a moving body which integrally moves a group of ultrasonic transducers along a row direction, the ultrasonic transducers being arranged two-dimensionally, that is, along a column direction and the row direction, and including a plurality of column-directional array ultrasonic transducers for creating a tomographic echo image. The control means repeats intermittent movement control for the moving body within a shorter distance than a row pitch of the ultrasonic transducers along the row direction for each of a plurality of predetermined periods. The position information input means receives position information on a stop position of the moving body. The storage means stores a two-dimensional image and the position information on the stop position in association with each other, the two-dimensional image being generated by making original image information, which is obtained by the ultrasonic transducers within the plurality of predetermined periods, two-dimensional in the ultrasonograph. The image processing means performs three-dimensional image processing based on the two-dimensional image and the position information, or performs temporal changing of a three-dimensional image with time, that is, four-dimensional image processing based on the two-dimensional image, the position information, and temporal information on the plurality of predetermined periods. The image generation means generates at least one image from among the images of a maximum diameter, a minimum diameter and the difference between the maximum diameter and the minimum diameter for each measurement site in an artery blood vessel, that is, for each stop position on the basis of the image information subjected to the image processing in the image processing means. 
     With this configuration, when the rigidity defined in physiological blood pressure variation region at rest and the dynamic deformation behavior at a high pulsation speed (stress test) are measured and compared with each other, a stress on the test subject is remarkably reduced on the examination. Further, a function of displaying an arteriosclerosis distribution diagram of arteries can be added to an existing ultrasonograph, thereby enabling an artery examination in a short time and diagnosis assistance. 
     Preferably, the blood vessel imaging program works the computer to function as heartbeat information input means for receiving heartbeat information. In this case, a heartbeat period based on the heartbeat information is employed as the predetermined period. According to this configuration, the heartbeat period may be used as the predetermined period to reliably acquire information on the maximum diameter and the minimum diameter of an artery blood vessel along with a heartbeat at a measurement site. 
     Preferably, the control means stops intermittent drive of the moving body when a total movement distance of the intermittently-driven moving body becomes equal to or greater than the row pitch of the ultrasonic transducers. With this configuration, since the intermittent drive of the moving body stops when the total movement distance of the intermittently-driven moving body becomes equal to or greater than the row pitch of the ultrasonic transducers, it is possible to efficiently measure the necessary sites in artery blood vessels. In other words, if the intermittent drive of the moving body does not stop when the total movement distance becomes equal to or greater than the row pitch of the ultrasonic transducers, unnecessary measurement is made, which may be inefficient. 
     Preferably, the blood vessel imaging program works the computer to function as calculation means for calculating an elastic modulus of a measurement site on the basis of the difference between the maximum diameter and the minimum diameter for each measurement site in artery blood vessels, that is, for each stop position and a previously input blood pressure at rest. According to this configuration, the elastic modulus of the measurement site is obtained on the basis of the difference between the maximum diameter and the minimum diameter for each measurement site in artery blood vessels and the previously input blood pressure at rest, thereby obtaining deformability (hardness, arteriosclerosis) of the measurement site. 
     According to still another aspect of the present invention, there is provided a blood vessel imaging method. The blood vessel imaging method comprises a step of repeating intermittent movement control for the moving body which integrally moves a group of ultrasonic transducers along a row direction, the ultrasonic transducers being arranged two-dimensionally, that is, along a column direction and along the row direction, and including column-directional array ultrasonic transducers for creating a tomographic echo image, the intermittent movement control for the moving body being performed in a shorter distance than a row pitch of the ultrasonic transducers along the row direction for each of a plurality of predetermined periods. In this case, the blood vessel imaging method comprises a step of inputting position information on a stop position of the moving body and a step of storing a two-dimensional image and the position information on the stop position in association with each other, the two-dimensional image being generated by making original image information, which is obtained by the ultrasonic transducers in the plurality of predetermined periods, two-dimensional in the ultrasonograph. The blood vessel imaging method comprises a step of performing three-dimensional image processing based on the two-dimensional image and the position information, or performing temporal changing of a three-dimensional image with time, that is, four-dimensional image processing based on the two-dimensional image, the position information, and temporal information on the plurality of predetermined periods. Further, the blood vessel imaging method comprises a step of generating at least one image from among the images of a maximum diameter, a minimum diameter and the difference between the maximum diameter and the minimum diameter for each measurement site in an artery blood vessel, that is, for each stop position on the basis of the image information subjected to the image processing. 
     According to this configuration, when the rigidity defined in a physiological blood pressure variation region at rest and the dynamic deformation behavior at a high pulsation speed (stress test) are measured and compared with each other, a stress on the test subject is remarkably reduced on the examination. Further, a function of displaying an arteriosclerosis distribution diagram of arteries can be added to an existing ultrasonograph, thereby enabling an artery examination in a short time and diagnosis assistance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing a configuration of a blood vessel imaging system according to a first embodiment; 
         FIG. 2  is a block diagram showing the blood vessel imaging system; 
         FIG. 3  is a schematic perspective view of a carriage and an ultrasonic probe; 
         FIG. 4  is a flowchart showing a processing of a blood vessel imaging program executed by a computer; 
         FIG. 5  is a diagram showing a three-dimensional image processing; 
         FIG. 6  is a graph showing changes in diameter of an artery blood vessel; 
         FIG. 7  is a schematic diagram showing a cross-sectional animation of an artery; 
         FIG. 8  is a schematic diagram showing a cross-sectional parallel image of an artery; 
         FIG. 9  is a diagram showing an arteriosclerosis analysis sheet; 
         FIGS. 10(   a ) and  10 ( b ) are diagrams showing a state in which the diameter of a carotid artery is changing due to pulsation; 
         FIG. 11  is a schematic perspective view of a carriage and an ultrasonic probe according to a second embodiment; and 
         FIG. 12  is a schematic perspective view showing a carriage and an ultrasonic probe according to another example. 
     
    
    
     BEST MODES FOR CARRYING OUT THE INVENTION 
     First Embodiment 
     A blood vessel imaging system according to a first embodiment of the present invention will be described below with reference to  FIGS. 1 to 10 . As shown in  FIGS. 1 and 2 , a blood vessel imaging system  11  according to the present embodiment comprises a computer  12 , a display  13 , a keyboard  15 , an ultrasonograph  16 , and an electrocardiograph  31 . 
     The blood vessel imaging system  11  analyzes the state of arteriosclerosis of a test subject on the basis of artery information of the test subject which is input from the keyboard  15  and the ultrasonograph  16  into the computer  12  or calculated by the computer  12 , and outputs the analysis result of the arteriosclerosis to the display  13  and a printer (not shown) as output means. The artery information of the test subject includes carotid artery animation, blood pressure information, name information, ID (Identification) information, age information, and position information. 
     The carotid artery animation is information indicative of dilatation, contraction, and deformation of a carotid artery of the test subject, which is an image-processed three-dimensional image or four-dimensional image. In other words, the carotid artery animation is information indicative of a temporal change for at least one period in the dilatation, contraction, and deformation of the carotid artery which successively repeats the dilatation, contraction, and deformation. As shown in  FIG. 1 , the animation is obtained by a known pulse reflection method using the ultrasonograph  16 . 
     An ultrasonic probe  21  connected to the ultrasonograph  16  will be described. As shown in  FIG. 3 , in the present embodiment, a plurality of ultrasonic probes  21  are attached to the carriage  20  as a moving body to be supported on the carriage  20 . The ultrasonic probe  21  comprises a probe body  22  constituted of a housing incorporating an ultrasonic transducer  24  for obtaining a tomographic image of a living body, and a cord  27  (see  FIG. 2 ) extending from the probe body  22 . The ultrasonic probe  21  is connected to the ultrasonograph  16  via the cord  27 . In order to illustrate an arrangement state of the ultrasonic transducers  24  for purposes of illustration,  FIG. 3  shows a state in which the ultrasonic transducers  24  are seen through from the ultrasonic probes  21 . 
     An end face of the probe body  22  constitutes an ultrasonic emission face and the end face is provided with an acoustic lens  25 . The ultrasonic transducer  24  of electronic scanning type made of piezoelectric device is arranged inside the probe body  22 . Specifically, the probe body  22  is configured in a linear arrangement in which a plurality of ultrasonic transducers  24  are arranged linearly, that is, in lines at a pitch A. The ultrasonic transducers  24  are arranged along the column direction indicated by an arrow shown in  FIG. 3 . The ultrasonic scanning is performed along the column direction of the probe body  22 . The adjacent ultrasonic probes  21  are arranged along the row direction orthogonal to the column direction to be separated at a pitch S, that is, at a row pitch. A value of the pitch S is on the order of 3 to 10 mm, for example. In this manner, each probe body  22  is provided with a column-directional array ultrasonic transducer made of a plurality of ultrasonic transducers for creating a tomographic echo image, and the plurality of ultrasonic probes  21  are arranged along the row direction. 
     The carriage  20  is supported on the rail  19  to be movable along the row direction, and is driven by a screw rod (not shown) rotated by a drive device  18 . Since the carotid artery blood vessel is to be measured, the rail  19  according to the present embodiment is arranged in a direction in which the carotid artery blood vessel extends. The drive device  18  according to the present embodiment is configured in a servo motor, but may be configured in a step motor, for example. 
     The ultrasonograph  16  comprises a display unit and an ultrasonic source (neither shown). The ultrasonograph  16  transmits a pulse wave into a living body from a distal face of the ultrasonic probe  21  and receives a reflection wave (echo) from a carotid artery  23  (see  FIG. 1 ) as original image information. The ultrasonograph  16  is configured such that the distal face of the ultrasonic probe  21  is formed in a rectangular shape, and a cross-sectional image of the carotid artery  23  is acquired as a tomographic echo image which is an echo animation acquired in the B/M mode. The display unit (not shown) of the ultrasonograph  16  displays thereon an animation as two-dimensional image when the carotid artery  23  of the test subject dilates, contracts or deforms. In other words, in the ultrasonograph  16 , the display unit (not shown) displays thereon an artery&#39;s cross-sectional animation (two-dimensional image) as animation for the schematically-shown carotid artery  23 , or the like. The artery&#39;s cross-sectional animation is an animation of the image indicative of the cross section in the diameter direction of the carotid artery  23 . 
     The ultrasonograph  16  is connected to the computer  12 , and the artery&#39;s cross-sectional animation (two-dimensional image, not shown) or the like acquired by the ultrasonograph  16  is input into the computer  12  and is stored in a storage device  44  as storage means to be associated with the ID information of the test subject. 
     A side of one ultrasonic probe  21  is provided with a movement detection device  30  as a position detection device. The movement detection device  30  comprises an image sensor (not shown) and a digital signal processor (DSP). The movement detection device  30  processes by the DSP an image of a test subject&#39;s body surface photographed by the image sensor to measure a movement distance from an arbitrary reference position on the test subject&#39;s body surface to the stop position of the ultrasonic probe  21 . The movement distance is input into the computer  12  as position information. The position information is information indicative of the position of the site where the arteriosclerosis state is analyzed, that is, the position of the site where an animation on the carotid artery is acquired in the test object&#39;s body. 
     When the arteriosclerosis state of the carotid artery is analyzed, it is simplest if a bifurcation at which the common carotid artery bifurcates into the internal carotid artery and the external carotid artery is set as a reference point, for example. In the blood vessel imaging system  11 , the reference point is previously input or stored in the computer  12 . Then, a reference position of the body surface corresponding to the reference point is detected by the movement detection device  30 , and the movement direction and the movement distance of the ultrasonic probe  21  relative to the reference position are detected by the movement detection device  30  so that the position information on the stop position is acquired. Further, the blood vessel imaging system  11  substantially successively acquires the position information on the stop position for one carotid artery  23  so that a detailed analysis result in which the position information and the arteriosclerosis analysis result for the carotid artery  23  are combined can be obtained. The information such as age information, name information, and ID information of the test subject is stored from the keyboard  15  into the storage device  44  of the computer  12  to be associated with each other. 
     The blood pressure information is configured with a maximum blood pressure (that is, maximum value) and a minimum blood pressure (that is, minimum value) at rest which are measured by a blood pressure measurement device (not shown). The blood pressure information is input into the computer  12  through the keyboard  15  or an electric signal relating to the blood pressure information from the blood pressure measurement device and is stored in the storage device  44  to be associated with the ID information of the test subject. 
     The heartbeat information is configured with an electrocardiogram measured by an electrocardiograph  31  whose electrodes  31   a  are attached to predetermined sites of the test subject&#39;s body as shown in  FIG. 1  in the present embodiment. The heartbeat information is input into the computer  12  via an A/D  32  and is stored in the storage device  44  to be associated with the ID information of the test subject. The heartbeat information is not limited to the electrocardiogram and includes pulse wave, heart sound and the like in addition to the electrocardiogram. When the pulse wave is input, a sphygmograph is employed as the heartbeat information input means, and when the heart sound is input, a phonocardiograph is employed as the heartbeat information input means. 
     As shown in  FIG. 1 , a basic model of the electrocardiogram is composed of a spike called PQRST, where P indicates atrial excitation, QRS indicates ventricular excitation process, and T indicates ventricular excitation withdrawal process. A temporal relationship of the spike changes depending on the size of the heart and the heart rate. However, the temporal relationship of the spike in the case of an adult is substantially constant, and specifically PQ is on the order of 0.12 to 0.20 seconds, QRS is on the order of 0.05 to 0.08 seconds, and QT is on the order of 0.3 to 0.4 seconds. 
     A time between R and R is detected on the basis of the heartbeat information, for example, thereby obtaining a heartbeat period. The detection for obtaining the heartbeat period is not limited to the time between R and R, and for example, a time between P and P may be detected and a time between Q and Q may be detected. The heartbeat period corresponds to the predetermined period. 
     As shown in  FIG. 2 , the computer  12  comprises a CPU  41  (central processing unit), a ROM  42  and a RAM  43 . The computer  12  executes a blood vessel imaging program stored in the ROM  42  to analyze an arteriosclerosis state based on the artery information, and performs an image processing on an animation as two-dimensional image when the carotid artery  23  of the test subject dilates, contacts or deforms to thereby generate a three-dimensional image or a four-dimensional image. The RAM  43  is a working memory when the program is being executed. The storage device  44  is configured with a hard disk or semiconductor storage device, for example, and is externally attached to the computer  12 . Various information described above can be read from or written into the storage device  44 . 
     The computer  12  having the storage device  44  corresponds to control means, position information input means, heartbeat information input means, storage means, image processing means, image generation means, and calculation means. 
     In the following, there will be described a processing of the blood vessel imaging program executed by the CPU  41  in the blood vessel imaging system  11  as configured above with reference to the flowchart of  FIG. 4 . The rail  19  is arranged in a direction in which the carotid artery blood vessel extends, each ultrasonic probe  21  is attached on the neck of the test subject, and the age information, the name information, the ID information and the blood pressure information of the test subject, for example, are input from the keyboard  15  to be stored in the storage device  44 . 
     (Step S 10 : Measurement and Recording for Several Times of Pulsation) 
     In step S 10 , the CPU  41  stores the image in the B/M mode from the ultrasonograph  16  and the position information from the movement detection device  30  into the storage device  44  for several times of pulsation, that is, for several heartbeats on the bases of the heartbeat information from the electrocardiograph  31 . The number of heartbeats may be arbitrarily set and may be appropriately preset through the input from the keyboard  15 . As a result, a tomographic image of an arbitrary position obtained by the ultrasonic probe  21  is used to record changes in blood vessel diameter for the several heartbeats along with pulsation (heartbeats) in the storage device  44 . Therefore, the storage device  44  records therein a heartbeat period for the several heartbeats. The heartbeat period for the several heartbeats corresponds to temporal information on a plurality of predetermined periods. In this manner, the storage device  44  stores therein spatial information (three-dimensional information) of cross-sectional image and position information, and four-dimensional information such as temporal information on the plurality of predetermined periods. 
     A plurality of ultrasonic probes  21  are provided. Thus, with reference to the ultrasonic probe  21  to which the movement detection device  30  is attached, the cross-sectional image acquired by another adjacent ultrasonic probe  21  is associated with the position information to which the respective separation distances from the ultrasonic probe  21  as the reference are added, and is stored in the storage device  44 . 
     (Step S 20 : Movement of Measurement Pitch Distance P) 
     In step S 20 , the CPU  41  synchronizes with the heartbeat period on the basis of the heartbeat information from the electrocardiograph  31 , outputs a control signal to the drive device  18 , and drives the drive device  18  to move the carriage  20  by a measurement pitch distance P. Consequently, each ultrasonic probe  21  synchronizes with the heartbeat period to move on the rail  19  along the row direction by the measurement pitch distance P. The measurement pitch distance P is set at a minute distance (for example, 0.5 mm) shorter than the pitch S (for example, about 3 to 10 mm in the present embodiment), but the minute distance is not limited to 0.5 mm. 
     (Step S 30 : Calculation of Total Movement Distance) 
     Next, the CPU  41  calculates a total movement distance nP. In the calculation of the total movement distance nP, in step S 30 , the measurement pitch distance P is added to the total movement distance nP previously calculated. An initial value of the total movement distance nP is set at 0, where n is the number of times of movement of the ultrasonic probe  21 . 
     (Step S 40 : Determination of Total Movement Distance) 
     Next, the CPU  41  determines whether or not the total movement distance nP is equal to or more than the pitch S (row pitch) in step S 40 . When the total movement distance nP is less than the pitch S (row pitch), the CPU  41  determines “NO” in step S 40  and the processing returns to step S 10 . In other words, the processing returns to step S 10  so that the processing in step S 10  is subsequently repeated. When the total movement distance nP is equal to or more than the pitch S (row pitch), the CPU  41  determines “YES” in S 40  and the processing proceeds to step S 50 . 
     Consequently, when the determination is “YES”, the four-dimensional information is stored in the storage device  44  for the entire region from the measurement site of the carotid artery blood vessel when the ultrasonic probe  21  is first positioned to the carotid artery blood vessel positioned in the pitch S. 
     (Step S 50 : Reconstruction of Image) 
     The CPU  41  performs three-dimensional image processing based on the two-dimensional image and the position information of the carotid artery blood vessel stored in the storage device  44 , or performs four-dimensional image processing based on the two-dimensional image and the position information of the carotid artery blood vessel as well as the temporal information. In the case of the three-dimensional image processing, as shown in  FIG. 5 , the three-dimensional image processing is performed by surface rendering or volume rendering of the two-dimensional image (including the images at the time of dilatation and contraction) acquired by the ultrasonic probe  21  so that the carotid artery image is acquired. Further, if four-dimensioning is previously set, the CPU  41  performs the surface rendering or volume rendering of the two-dimensional image of the carotid artery blood vessel on the basis of the position information and the temporal information on predetermined time, and adds the temporal information to perform the four-dimensional image processing, thereby acquiring the carotid artery image. Moreover, the CPU  41  calculates an elastic modulus Eth. 
     (Calculation of Elastic Modulus Eth) 
     The CPU  41  performs dimension analysis of the carotid artery for each site where each image is acquired on the basis of the carotid artery image. 
     (Dimension Analysis of Carotid Artery) 
     The dimension analysis of the carotid artery will be described. 
     1. A Case where the Cross Section of the Carotid Artery is Circular 
     First, the case where the cross section of the carotid artery is circular will be described. 
     As shown in  FIG. 7 , the CPU  41  extracts an artery cross-sectional image  51  from an artery cross-sectional animation  26 . The artery cross-sectional image  51  has a rectangular shape and a plurality of artery cross-sectional images  51  are extracted from the artery cross-sectional animation  26  for each constant time (for example, at an interval of about 0.05 seconds). Each artery cross-sectional image  51  is extracted such that the center of the carotid artery  23  is positioned on the center portion of the artery cross-sectional image  51 , and at least the inner diameter and the outer diameter of the carotid artery  23  are set in a displayable size. The width f in a shorter direction in each artery cross-sectional image  51  is set to be equal among the respective artery cross-sectional images  51 . The width f of the artery cross-sectional image  51  specifically corresponds to about several pixels (0.5 to 1 mm in the diameter direction of the carotid artery) on the display  13 . 
     As shown in  FIG. 8 , the CPU  41  arranges the lower ends of the carotid arteries  23  in the respective artery cross-sectional images  51  along a reference line  52  to create an artery cross-sectional parallel image  53  as a parallel image. In the artery cross-sectional parallel image  53 , each artery cross-sectional image  51  is arranged in parallel to be partially overlapped on another image in the order of extraction. The interval between the artery cross-sectional images  51  is set on the order of (width f)/2+several mm so that each artery cross-sectional image  51  is arranged such that the radius or diameter of the carotid artery  23  in the artery cross-sectional image  51  is displayed. 
     It is preferable that an image processing such as binarizing or contrast inversion is performed on the artery cross-sectional image  51 . The carotid artery wall is made clear by the image processing so that the accuracy of the image analysis is improved when the blood vessel diameter is measured. 
     The CPU  41  creates a change curve indicative of a temporal change in carotid artery diameter from the artery cross-sectional parallel image  53 . The CPU  41  connects midpoints  56  on the outer faces and midpoints  57  on the inner faces of the upper ends of the carotid arteries  23  in the respective artery cross-sectional images  51 , respectively, in the artery cross-sectional parallel image  53  shown in  FIG. 8  to create a lateral change curve as change curve indicated by broken lines in  FIG. 8 . Various numerical values for calculating the elastic modulus Eth are extracted from the lateral change curve  58 . In other words, the CPU  41  extracts an outer radius R′ 0  of the carotid artery  23  at the maximum dilatation, an outer radius R 0  and an inner radius R i  of the carotid artery  23  at the maximum contraction as well as the difference ΔR 0  between the outer radius of the carotid artery  23  at the maximum dilatation and the outer radius of the carotid artery  23  at the maximum contraction from the lateral change curve  58  (see  FIGS. 7 and 8 ). 
     2. A Case where the Cross Section of the Carotid Artery is Noncircular 
     The CPU  41  determines whether or not the cross section of the carotid artery  23  is noncircular, and when the cross section of the carotid artery  23  is noncircular, for example when the cross section thereof is oval, the CPU  41  calculates the radii (outer radius, inner radius) of the carotid artery  23  by the processing described later. In this case, when the distances from the center of gravity of the artery cross-sectional image  51  to a plurality of arbitrary points contained in the outer profile of the carotid artery  23  are equal to each other, the CPU  41  determines that the cross section is circular. A determination as to whether the cross section is circular or noncircular may be made by pattern matching. 
     The CPU  41  obtains an outer diameter area (area occupied by the outer profile of the carotid artery  23 ) of the carotid artery  23  from the cross-sectional image at the maximum dilatation and assumes a circle corresponding to the area. Then, the CPU  41  calculates a corresponding radius of the assumed circle and sets it to be the outer radius R′ 0  of the carotid artery  23  at the maximum dilatation. Further, the CPU  41  obtains the outer diameter area (area occupied by the outer profile of the carotid artery  23 ) of the carotid artery  23  from the cross-sectional image at the maximum contraction and assumes a circle corresponding to the area. Then, the CPU  41  calculates a corresponding diameter of the assumed circle and sets it to be the outer radius R 0  of the carotid artery  23  at the maximum contraction. Further, the CPU  41  obtains an inner diameter area (area surrounded by the blood vessel inner wall of the carotid artery  23 ) of the carotid artery  23  from the cross-sectional image at the maximum contraction and assumes a circle corresponding to the area. Then, the CPU  41  calculates a corresponding diameter of the assumed circle and sets it to be the inner radius R i  of the carotid artery  23  at the maximum contraction. Then, the CPU  41  extracts the difference ΔR 0  between the outer radius of the carotid artery  23  at the maximum dilatation and the outer radius of the carotid artery  23  at the maximum contraction. 
     (Calculation of Elastic Modulus Eth) 
     The elastic modulus Eth is a parameter indicative of a mechanical property of the carotid artery, that is, rigidity, and is obtained from the temporal change in the carotid artery diameter and the blood pressure variation value of the test subject. Specifically, the CPU  41  uses the following expression (1) to calculate the elastic modulus Eth of each site of the carotid artery  23 . The blood pressure variation value is calculated from the blood pressure information and indicates the difference between the maximum blood pressure (that is, maximum value) and the minimum blood pressure (that is, minimum value) of the test subject. 
     
       
         
           
             
               
                 
                   
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     As described above, R 0  indicates the outer radius of the carotid artery  23  at the maximum contraction, R i  indicates the inner radius of the carotid artery  23  at the maximum contraction, ΔP indicates the difference between the maximum blood pressure and the minimum blood pressure, and ΔR 0  indicates the difference between the outer radius of the carotid artery  23  at the maximum dilatation and the outer radius of the carotid artery  23  at the maximum contraction. The calculated elastic modulus Eth corresponds to the arteriosclerosis analysis result. 
     (Step S 60 ) 
     In step S 60 , the three-dimensional image or four-dimensional image subjected to the image processing in step S 50  and the elastic modulus Eth are displayed on the display  13 . In other words, the CPU  41  mutually combines and outputs the age information, the name information, the ID information as well as the elastic modulus Eth and the position information of the test subject and displays the elastic modulus Eth and the position information on the display  13 . In the present embodiment, an arteriosclerosis analysis sheet  71  shown in  FIG. 9  is displayed on the display  13 .  FIG. 9  exemplifies a case in which the right and left carotid arteries  23 R and  23 L are measured with 6 sites each. The carotid arteries  23 R and  23 L shown in  FIG. 9  are subjected to the image processing to be illustrated as one example of the three-dimensional image. 
     The arteriosclerosis analysis sheet  71  indicates therein the upper body  100  of a person, the right and left carotid arteries  23 R and  23 L, position information  77 , and the elastic modulus Eth indicated by a bar graph at each position where the carotid artery image is acquired as the arteriosclerosis distribution diagram. 
     In the present embodiment, the position information  77  is indicated at a position where the carotid artery image is acquired, that is, at a position of the measurement site (that is, the stop position of the carriage  20 ) with the bifurcation as a reference. The position information  77  is indicated so that the position of locally occurring arteriosclerosis can be easily identified. The arteriosclerosis analysis sheet  71  is printable by a printer (not shown) and the printed arteriosclerosis analysis sheet  71  can be provided to the test subject and doctors. 
     In the present embodiment, for the right and the left carotid arteries  23 R and  23 L, graphs  73  and  74  of the sites where the elastic modulus Eth is minimum are displayed in an easily viewable color different from the graphs of other sites so as to be paid more attention than other sites. The means for easy attraction is not limited to the display in a different color from other graphs. For example, the graph of a site where the elastic modulus Eth is minimum may be displayed in a blinking manner or may be displayed in a bar graph to be wider than other sites. 
     The arteriosclerosis analysis sheet  71  displays, for the right and left carotid arteries  23 R and  23 L, the graphs  73  and  74  for inner diameter displacement-time curve at the site where the elastic modulus Eth is minimum.  FIG. 9  shows the graphs  73  and  74  for inner diameter displacement-time curve at the site where the elastic modulus Eth is minimum. However, as shown in  FIG. 6 , the position information  77  of each measurement site may be indicated to be lined with each other with respect to the reference position and the graphs for inner diameter displacement-time curve of the respective sites may be displayed. 
     The arteriosclerosis analysis sheet  71  is provided with the maximum and minimum display regions  71   a  and  71   b  of the diameter. The maximum and minimum display region  71   a  displays a maximum diameter image  80  of the inner diameter and a minimum diameter  81  of the inner diameter for the right carotid artery in the three-dimensional images and a two-dimensional diagram  82  of changes in the maximum diameter and the minimum diameter. The maximum and minimum display region  71   b  of the diameter displays a maximum diameter image  90  of the inner diameter and a minimum diameter  91  of the inner diameter for the left carotid artery in the three-dimensional images and a two-dimensional diagram  92  of changes in the maximum diameter and the minimum diameter. The two-dimensional diagram of the diameter change in the maximum diameter and the minimum diameter represents deformability of a blood vessel at each position. The two-dimensional diagram of the diameter change in the maximum diameter and the minimum diameter corresponds to an image of the difference between the maximum diameter and the minimum diameter. 
     In this manner, the arteriosclerosis analysis result of the carotid artery of the test subject is presented by means of the arteriosclerosis analysis sheet  71 . When the arteriosclerosis analysis sheet  71  is printed by the printer (not shown), for the right and left carotid arteries  23 R and  23 L, the site where the elastic modulus Eth is minimum is printed in a easily viewable color different from the graphs of other sites in order to be paid more attention than other sites. 
     The present embodiment has the following advantages. 
     (1) The blood vessel imaging system  11  according to the present embodiment comprises the ultrasonograph  16  and the carriage  20  (moving body). The carriage  20  integrally moves a plurality of ultrasonic probes  21  along the row direction, which have a plurality of ultrasonic transducers  24  arranged along the column direction and are arranged along the row direction. The blood vessel imaging system  11  comprises the computer  12  (control means) for repeating intermittent movement control for the carriage  20  for each of a plurality of predetermined periods in a shorter distance than the pitch S (row pitch) of the ultrasonic transducer  24  along the row direction. The computer  12  comprises the storage device  44  to function as the position information input means, and the position information on the stop position of the carriage  20  is input into the computer  12 . 
     The computer  12  functions as the storage means for storing the two-dimensional image and the position information on the stop position in association with each other, the two-dimensional image being generated by making the original image information, which is obtained by the ultrasonic transducer  24  in the plurality of predetermined periods, two-dimensional in the ultrasonograph  16 . Further, the computer  12  functions as the image processing means for performing the three-dimensional image processing on the basis of the two-dimensional image and the position information or performing the four-dimensional image processing on the basis of the two-dimensional image, the position information and the temporal information on the plurality of predetermined periods. The computer  12  functions as the image generation means for generating the images of a maximum diameter, a minimum diameter and the difference between the maximum diameter and the minimum diameter for each measurement site in the carotid artery (artery blood vessel), that is, for each stop position on the basis of the image information subjected to the image processing. 
     As a result, the blood vessel imaging system  11  according to the present embodiment can make measurement of the elastic modulus Eth (rigidity) of the physiological blood pressure variation region (between the maximum blood pressure and the minimum blood pressure) at rest in a short time, thereby remarkably reducing a stress on the test subject. 
     Further, the blood vessel imaging system  11  according to the present embodiment can add to the existing ultrasonograph  16  the function of displaying an arteriosclerosis distribution diagram of arteries, that is, a distribution diagram in which the elastic modulus Eth and the position information  77  are combined as shown in  FIG. 9 , thereby enabling an artery examination in a short time and diagnosis assistance. 
     (2) In the present embodiment, the computer  12  of the blood vessel imaging system  11  receives the heartbeat information (electrocardiogram) as the heartbeat information input means, and the computer  12  functioning as the control means employs the heartbeat period based on the heartbeat information as a predetermined period. Consequently, the heartbeat period can be employed as a predetermined period to reliably acquire the information on the maximum diameter and the minimum diameter of the carotid artery (artery blood vessel) along with the heartbeat at the measurement site. 
     (3) In the present embodiment, the computer  12  functioning as the control means stops the intermittent drive of the carriage  20  when the total movement distance nP of the intermittently-driven carriage  20  becomes equal to or greater than the pitch S (row pitch) of the ultrasonic transducers  24 . 
     As a result, since the intermittent drive of the carriage  20  stops when the total movement distance nP of the intermittently-driven carriage  20  becomes equal to or greater than the pitch S (row pitch) of the ultrasonic transducers  24 , it is possible to efficiently measure the necessary sites of the carotid artery (artery blood vessel). In other words, if the intermittent drive of the carriage  20  does not stop when the total movement distance nP becomes equal to or greater than the pitch S of the ultrasonic transducers  24 , unnecessary measurement is made, which may be inefficient. 
     (4) In the present embodiment, the computer  12  of the blood vessel imaging system  11  functions as the calculation means to calculate the elastic modulus Eth of the measurement site on the basis of the difference between the maximum diameter and the minimum diameter for each measurement site in the carotid artery (artery blood vessel), that is, for each stop position, and the previously input blood pressure at rest. 
     Consequently, the elastic modulus Eth of the measurement site can be obtained on the basis of the difference between the maximum diameter and the minimum diameter for each measurement site in the carotid artery (artery blood vessel) and the previously input blood pressure at rest, thereby obtaining deformability (hardness, arteriosclerosis) of the measurement site. 
     (5) The blood vessel imaging program according to the present embodiment works the computer  12  to function as the control means for performing movement control for the carriage  20  which integrally moves a group of ultrasonic transducers along the row direction, the control means repeating intermittent movement control for the carriage  20  within a shorter distance than the pitch S of the ultrasonic transducers  24  along the row direction for each of a plurality of predetermined periods. Further, the blood vessel imaging program works the computer  12  to function as the position information input means for receiving the position information on the stop position of the carriage  20 . Moreover, the blood vessel imaging program works the computer  12  to function as the storage means for storing the two-dimensional image and the position information on the stop position in association with each other, the two-dimensional image being generated by making original image information, which is obtained by the ultrasonic transducer  24  within a plurality of predetermined periods, two-dimensional in the ultrasonograph  16 . 
     Further, the blood vessel imaging program works the computer  12  to function as the image processing means for performing three-dimensional image processing on the basis of a two-dimensional image and position information or performing four-dimensional image processing on the basis of the two-dimensional image, the position information and the temporal information on a plurality of predetermined periods. The blood vessel imaging program works the computer  12  to function as the image generation means for generating the images of a maximum diameter, a minimum diameter and the difference between the maximum diameter and the minimum diameter for each measurement site in the artery blood vessel, that is, for each stop position on the basis of the image information subjected to the image processing. 
     Consequently, the blood vessel imaging program is capable of remarkably reducing a stress on the test subject when the rigidity of the physiological blood pressure variation region at rest is measured. Further, the blood vessel imaging program according to the present embodiment can add to the existing ultrasonograph  16  the function of displaying an arteriosclerosis distribution diagram of arteries, thereby enabling an artery examination in a short time and diagnosis assistance. 
     (6) The blood vessel imaging program according to the present embodiment works the computer  12  to function as the heartbeat information input means for receiving heartbeat information, and a heartbeat period based on the heartbeat information is employed as a predetermined period. As a result, the heartbeat period is employed as a predetermined period to reliably acquire the information on the maximum diameter and the minimum diameter of the carotid artery (artery blood vessel) along with the heartbeat at the measurement site. 
     (7) The blood vessel imaging program according to the present embodiment works the computer  12  to function as the control means for stopping the intermittent drive of the carriage  20  when the total movement distance nP of the intermittently-driven carriage  20  becomes equal to or greater than the pitch S of the ultrasonic transducers  24 . As a result, since the intermittent drive of the carriage  20  stops when the total movement distance nP of the intermittently-driven carriage  20  becomes equal to or greater than the pitch S of the ultrasonic transducer  24 , measurement of the necessary sites of the carotid artery (artery blood vessel) can be efficiently made. In other words, if the intermittent drive of the carriage  20  does not stop when the total movement distance nP becomes equal to or greater than the pitch S of the ultrasonic transducer  24 , unnecessary measurement is made, which may be inefficient. 
     (8) The blood vessel imaging program according to the present embodiment works the computer  12  to function as the calculation means for calculating the elastic modulus Eth of the measurement site on the basis of the difference between the maximum diameter and the minimum diameter for each measurement site in the artery blood vessel, that is, for each stop position, and the previously input blood pressure at rest. As a result, the elastic modulus Eth of the measurement site can be obtained on the basis of the difference between the maximum diameter and the minimum diameter for each measurement site in the carotid artery (artery blood vessel) and the previously input blood pressure at rest, thereby obtaining deformability (hardness, arteriosclerosis) of the measurement site. 
     (9) The blood vessel imaging method according to the present embodiment comprises the step of repeating intermittent movement control for the carriage  20  which integrally moves a group of ultrasonic transducers along the row direction, the ultrasonic transducers including a plurality of ultrasonic transducers  24  arranged two-dimensionally, that is, along the column direction and the row direction, respectively, the intermittent movement control for the carriage  20  being performed within a shorter distance than the pitch S of the ultrasonic transducers  24  along the row direction for each of a plurality of predetermined periods. Further, the blood vessel imaging method comprises the step of receiving position information on a stop position of the carriage  20 , and the step of storing the two-dimensional image and the position information on the stop position in association with each other, the two-dimensional image being generated by making original image information, which is obtained by the ultrasonic transducer  24  within a plurality of predetermined periods, two-dimensional in the ultrasonograph  16 . 
     Moreover, the blood vessel imaging method comprises the step of performing three-dimensional image processing on the basis of a two-dimensional image and position information or performing four-dimensional image processing on the basis of the two-dimensional image, the position information and the temporal information on a plurality of predetermined periods. Additionally, the blood vessel imaging method comprises the step of generating the images of a maximum diameter, a minimum diameter and the difference between the maximum diameter and the minimum diameter for each measurement site in the artery blood vessel, that is, for each stop position on the basis of the image information subjected to the image processing. 
     Consequently, there can be provided the blood vessel imaging method capable of remarkably reducing a stress on the test subject when measuring the rigidity of the physiological blood pressure variation region at rest. Further, the function of displaying the arteriosclerosis distribution diagram of the arteries can be added to the existing ultrasonograph, thereby enabling an artery examination in a short time and diagnosis assistance. 
     Second Embodiment 
     In the following, a blood vessel imaging system according to a second embodiment of the present invention will be described with reference to  FIG. 11 . The same numerals are denoted to the same constituents as those in the first embodiment to omit the description thereof, and different configurations from the first embodiment will be mainly explained in the following description. 
     Specifically, in the second embodiment, the configurations of the ultrasonic probe  21  and the carriage  20  are different from those in the first embodiment and other configurations are the same as those in the first embodiment. Thus, the configurations of the ultrasonic probe  21  and the carriage  20  will be described. 
     As shown in  FIG. 11 , the ultrasonic probe  21  is formed into a concave cross-sectional shape extending along the surface shape of the cervical region. In the ultrasonic probe  21 , a plurality of groups of ultrasonic transducers  24 , in which a plurality of ultrasonic transducers  24  are arranged in lines at a pitch A to be configured in a linear arrangement, are arranged at a pitch S (row pitch) in the concave surface opposed to the surface of the cervical region. In other words, a plurality of ultrasonic transducers  24  are arranged along the column direction and along the row direction, respectively. In the following description, the concave face of the ultrasonic probe  21  opposed to the surface of the cervical region is referred to as inner face. The row direction is a direction in which the carotid artery  23  extends and the column direction is a direction extending along the curvature direction of the inner face of the ultrasonic probe  21 . 
     The ultrasonic probe  21  is provided with the carriage  20  at an outer face opposed to the inner face. A pair of rod-shaped guide rails  19   a  fixed on a fixing portion (not shown), which extends in parallel to the direction in which the carotid artery  23  extends, is slidably passed through the carriage  20 . A screw rod  19   b  arranged in parallel to the guide rail  19   a  passes through a nut portion (not shown) provided on the carriage  20  to be meshed with the nut portion. The screw rod  19   b  is connected with the drive device  18  via a decelerator  18   a . The ultrasonic probe  21  is provided with the movement detection device  30 . 
     The rotation of the drive device  18  is controlled by the computer  12  so that the ultrasonic probe  21  is subjected to the intermittent movement control along the row direction at the pitch S. 
     The second embodiment has the following advantage in addition to the above advantages of the first embodiment. 
     (10) In the second embodiment, the carriage  20  comprises the ultrasonic probe  21  having a plurality of ultrasonic transducers  24  arranged along the column direction and along the row direction, respectively. The ultrasonic probe  21  comprises a concave face corresponding to the surface shape of the cervical region, and the plurality of ultrasonic transducers  24  are arranged on the face along the column direction and along the row direction, respectively. As a result, the blood vessel imaging system suitable for the carotid artery blood vessel of the cervical region can be provided. 
     The respective embodiments described above may be changed as follows. 
     The configuration of the ultrasonic probe  21  according to the second embodiment may be changed as shown in  FIG. 12 . In the configuration shown in  FIG. 12 , the shape of the ultrasonic probe  21  is set similarly as in the second embodiment, and a plurality of groups of ultrasonic transducers  24  which are arranged in lines at pitch A to be configured in a linear arrangement are arranged at the inner face at the pitch S (row pitch). Specifically, a plurality of ultrasonic transducers  24  are arranged along the column direction and along the row direction. The column direction is a direction in which the carotid artery  23  extends and the row direction is a direction extending in the curvature direction of the inner face of the ultrasonic probe  21 . 
     A rack is formed on the outer face of the carriage  20  and a pinion  18   b  fixed on an output shaft of the drive device  18  is meshed with the rack. Then, the rotation of the drive device  18  is controlled by the computer  12  so that the ultrasonic probe  21  is subjected to the intermittent movement control in the row direction at the pitch S. Also with the configuration, similar operational effects as in the second embodiment can be obtained. 
     In the respective embodiments, for the measurement of the rigidity of the physiological blood pressure variation region at rest, the elastic modulus Eth is measured (calculated) using the maximum blood pressure (that is, maximum value) and the minimum blood pressure (that is, minimum value) at rest and is displayed. Instead, the dynamic deformation behavior in a state where a stress is imposed on the test subject, that is, at a high pulsation speed (stress test) may be measured and compared with the measurement result of the dynamic deformation behavior at rest with less stress, and the result may be displayed on the display  13 . In this case, the computer  12  receives the blood pressure information in a stress-added state similarly as in the above embodiments. According to this configuration, when the dynamic deformation behavior at the high pulsation speed (stress test) is measured to be compared, a stress on the test subject is remarkably reduced. 
     The respective embodiments described above employ the heartbeat period as predetermined time but the predetermined time is not limited to the heartbeat period and a period longer than the heartbeat period may be employed. 
     The arteriosclerosis analysis result may be output from either one of the display  13  or the printer (not shown). 
     The present embodiments employ bar graphs, but line plots may be employed. 
     In the respective embodiments, the externally-attached storage device  44  is provided so that the computer  12  functions as the storage means. However, a storage device incorporated in the computer  12  may be employed. Further, a hard disk or memory made of semiconductor device may be employed as the storage device. 
     The computer  12  according to the respective embodiments generates the images of a maximum diameter, a minimum diameter and the difference between the maximum diameter and the minimum diameter for each measurement site in the carotid artery (artery blood vessel), that is, for each stop position on the basis of the image information subjected to the image processing. Alternatively, there may be generated only the image of the maximum diameter of the inner diameter for each stop position of the measurement site in the carotid artery (artery blood vessel), only the image of the minimum diameter thereof, or only the image of the difference between the maximum diameter and the minimum diameter. Further, the images of the maximum diameter and the minimum diameter of the inner diameter for each stop position of the measurement site in the carotid artery (artery blood vessel) may be generated, the image of the maximum diameter of the inner diameter and the image of the difference between the maximum diameter and the minimum diameter may be generated, or the image of the minimum diameter of the inner diameter and the image of the difference between the maximum diameter and the minimum diameter may be generated. 
     It has been intended the carotid artery in the respective embodiments described above, however any arteries imaging by ultrasonograph can also be applied.