Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2002-02-26
2003-11-04
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C073S628000, C073S633000, C600S443000, C600S447000
Reexamination Certificate
active
06640633
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an ultrasonic imaging method and an ultrasonic imaging apparatus, capable of performing nondestructive tests by employing ultrasonic waves. More specifically, the present invention is directed to such ultrasonic imaging method and apparatus, capable of scanning a radial-shaped area contained in an object to be inspected (sector scanning) by employing ultrasonic waves so as to obtain an image information of this radial-shaped area.
2. Description of a Related Art
Normally, in ultrasonic imaging apparatuses utilized as ultrasonic diagnostic apparatuses or industrial-purpose flaw detecting apparatuses, ultrasonic probes are employed each contains a plurality of ultrasonic transducers and has ultrasonic transmission/reception functions. In one typical ultrasonic imaging apparatus equipped with such an ultrasonic probe, image information related to an object to be inspected may be obtained in such a manner that this object to be inspected is ultrasonically scanned by using ultrasonic beams, while the ultrasonic beams are produced by synthesizing ultrasonic waves transmitted from the plurality of ultrasonic transducers. Then, the ultrasonic imaging apparatus may reproduce images of either two-dimensional areas or three-dimensional areas contained in the object to be inspected based upon the obtained image information. As one of scanning methods for scanning an object to be inspected by way of such ultrasonic beams, a so-called “sector scanning operation” is carried out by which a two-dimensional fan-shaped region is ultrasonically scanned along angular directions.
FIGS. 7A
to
7
C are explanatory diagrams for illustratively explaining one typical example of the conventional sector scanning operation.
As shown in
FIG. 7A
, since ultrasonic waves transmitted to an object to be inspected from a plurality of ultrasonic transducers contained in an ultrasonic probe are synthesized with each other, an ultrasonic beam
101
is formed in the object to be inspected, while this ultrasonic beam
101
is extended from a transmission point
100
in a depth direction. Then, a fan-shaped two-dimensional area
103
which is contained in the object to be inspected is sequentially scanned by this ultrasonic beam
101
“N” times in a direction of an angle “&thgr;” in an equi-interval. It should be noted that symbol “N” is a natural number.
Furthermore, as illustrated in
FIG. 7B
, at a plurality of sampling points
102
, image information is sequentially sampled, while these plural sampling points
102
are distributed in an equi-interval in the depth direction along the ultrasonic beam
101
at the respective angles. As previously described, while the scanning operation by using one ultrasonic beam is carried out, image information related to a plurality of sampling points located on this single ultrasonic beam is sampled every time a predetermined time period has passed.
FIG. 7C
shows a time chart for explaining such a scanning process operation of the ultrasonic beam. As shown in
FIG. 7C
, in order to perform a scanning operation of a single ultrasonic beam, a constant repetition time PRT (namely, pulse repetition time period) is consumed. Furthermore, a total value of pulse repetition time period PRT which is consumed to execute scanning operations of a plurality of ultrasonic beams-constitutes imaging time required for scanning an entire portion of a two-dimensional area. With respect to one pulse repetition time period PRT, a plurality of ultrasonic waves are transmitted to an object to be inspected so as to form one ultrasonic beam within a pulse transmission time slot TP. Then, at time instants indicated by white-colored points (see FIG.
7
C), ultrasonic echoes are received which are reflected from a plurality of sampling points distributed along one ultrasonic beam, and then, image information related to the respective sampling points is sampled based upon these received ultrasonic echoes.
However, when such a sampling operation of the image information as shown in
FIG. 7B
is carried out, a total number of ultrasonic beams
101
(namely, density of ultrasonic beams) employed in a scanning operation of a unit area with respect to a deeper portion
105
within a two-dimensional area
103
becomes smaller than that of a shallower portion
104
thereof. As a result, an image quality of image information related to the deeper portion
105
becomes coarser than that related to the shallower portion
104
.
As a consequence, as shown in
FIG. 8A
, the following solution method is conceivable. That is, since a total time of scanning operations for the deeper portion
105
is made larger than that of the shallower portion
104
, density of sampling points
102
within the deeper portion
105
can be increased substantially equal to density of the sampling points
102
within the shallower portion
104
. In
FIG. 8A
, black-colored points indicate such sampling points which are newly added. In this case, as shown in
FIG. 8A
, a scanning operation only directed to the deeper portion
105
is carried out between a first scanning operation and a second scanning operation of the conventional sector scanning operations, and then, such a scanning process operation is repeatedly carried out.
FIG. 8B
is a time chart for explaining such a scanning process operation of the ultrasonic beam. In this time chart, black-colored points represent time instants when ultrasonic echoes reflected from the newly added sampling points are received.
However, even in such a scanning operation directed only to the deeper portion, a time duration is required for ultrasonic waves transmitted from an ultrasonic probe to reach these sampling points and return to the ultrasonic probe. As a result, even when the scanning operation directed only to the deeper portion is carried out, such a time duration substantially equal to the time duration required for a single scanning operation in the conventional sector scanning operation would be consumed. As a consequence, a total scanning number of the sector scanning operation as shown in
FIG. 8A
is equal to substantially two times as large as a total scanning number of the sector scanning operation as shown in FIG.
7
B. Thus, a frame rate of this sector scanning operation as shown in
FIG. 8A
, which corresponds to an inverse number of imaging time, would be lowered to a substantially half of a frame rate in the sector scanning operation as shown in FIG.
7
B.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-described problems, and therefore, has an object to provide an ultrasonic imaging method and an ultrasonic imaging apparatus, capable of increasing density of sampling points in accordance with a depth degree within an object to be inspected, while a frame rate is not necessarily decreased.
To achieve the above-described object, an ultrasonic imaging method according to one aspect of the present invention, of obtaining image information in such a manner that a predetermined area contained in an object to be inspected is divided into at least a first area located most shallowly and a second area located deeper than the first area so as to scan the first and second areas by employing ultrasonic waves, comprises the steps of: (a) transmitting and receiving ultrasonic waves focused in one focus direction within the first area by using a plurality of ultrasonic transducers included in an ultrasonic probe to take samples of an ultrasonic image at a plurality of points in the focus direction, and changing the focus direction to scan the first area; (b) sequentially transmitting ultrasonic waves focused in respective focus directions within the second area by using the plurality of ultrasonic transducers in a predetermined time period, thereafter receiving ultrasonic waves reflected from the respective focus directions by using the plurality of ultrasonic transducers to take samples of the ultrasonic image at a plurality of points in the respective focus d
Fuji Photo Film Co. , Ltd.
Miller Rose M.
Sughrue & Mion, PLLC
Williams Hezron
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