Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2002-09-18
2004-02-17
Imam, Ali M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06692440
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Japanese Application No. 2001-287989 filed Sep. 21, 2001.
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic imaging method and ultrasonic diagnostic apparatus, and more particularly to an ultrasonic imaging method and ultrasonic diagnostic apparatus that eliminate a problem that a good harmonic image cannot be obtained due to a fundamental component of received data for a previous ultrasonic pulse intruding into a fundamental component of received data for a current ultrasonic pulse at a considerable intensity.
FIG. 14
is an explanatory diagram showing timing of B-mode imaging in a conventional ultrasonic diagnostic apparatus. In
FIG. 14
, a fundamental component is indicated by a solid line and a harmonic component by a broken line because the fundamental component is principal and the harmonic component is subsidiary in the B mode.
When an ultrasonic pulse fs with a relatively shallow (e.g., 5 cm) focus is transmitted at a time t1, the fundamental component of received data (i.e., a component of received data having the same frequency as the transmission frequency) indicated by the solid line in
FIG. 14
has an intensity decreasing over time with a maximum at the time t1. The harmonic component (i.e., a component of received data having a frequency twice as high as the transmission frequency) of the received data indicated by the broken line has an intensity rapidly decreasing over time with a maximum slightly after the time t1.
A time t2 is a time point when the intensity of the fundamental component of the received data for the ultrasonic pulse fs transmitted at the time t1 decreases to a negligible level (e.g., the component becomes smaller than a noise component or a detection sensitivity).
When an ultrasonic pulse fm with a relatively intermediate (e.g., 10 cm) focus is transmitted at the time t2, the fundamental component of received data indicated by the solid line in
FIG. 14
has an intensity decreasing over time with a maximum at the time t2. The harmonic component of the received data indicated by the broken line has an intensity rapidly decreasing over time with a maximum slightly after the time t2.
A time t3 is a time point when the intensity of the fundamental component of the received data for the ultrasonic pulse fm transmitted at the time t2 decreases to a negligible level.
When an ultrasonic pulse fd with a relatively deep (e.g., 15 cm) focus is transmitted at the time t3, the fundamental component of received data indicated by the solid line in
FIG. 14
has an intensity decreasing over time with a maximum at the time t3. The harmonic component of the received data indicated by the broken line has an intensity rapidly decreasing over time with a maximum slightly after the time t3.
A time t4 is a time point when the intensity of the fundamental component of the received data for the ultrasonic pulse fd transmitted at the time t3 decreases to a negligible level.
When an ultrasonic pulse fs with a relatively shallow (e.g., 5 cm) focus is transmitted at the time t4, the fundamental component of received data indicated by the solid line in
FIG. 14
has an intensity decreasing over time with a maximum at the time t4. The harmonic component of the received data indicated by the broken line has an intensity rapidly decreasing over time with a maximum slightly after the time t4.
A similar operation is repeated thereafter.
The frame rate is 1/(&tgr;s+&tgr;m+&tgr;d)÷N, where the interval between the times t1 and t2 is represented by &tgr;s, the interval between the times t2 and t3 is represented by &tgr;m, the interval between the times t3 and t4 is represented by &tgr;d, the ultrasonic pulses fs, fm and fd gives one acoustic line, and the number of acoustic lines in one frame is N. Moreover, &tgr;s<&tgr;m<&tgr;d.
If the transmission intervals for the ultrasonic pulses fs, fm and fd are uniformly set to &tgr;s, the received data for the ultrasonic pulse fm remains at a considerable intensity when reception of received data for the ultrasonic pulse fd is started, compromising imaging. Moreover, the received data for the ultrasonic pulse fd remains at a considerable intensity when reception of received data for the ultrasonic pulse fs is started, compromising imaging.
If the intervals are uniformly set to &tgr;m, the received data for the ultrasonic pulse fd remains at a considerable intensity when reception of received data for the ultrasonic pulse fs is started, compromising imaging.
On the other hand, the intervals uniformly set to &tgr;d do no harm in imaging.
However, the frame rate is 1/(3·&tgr;d)÷N, which is lower than that in FIG.
14
.
In other words, the ultrasonic pulses fs, fm and fd are transmitted at timing as shown in
FIG. 14
so that a higher frame rate can be achieved.
FIG. 15
is an explanatory diagram showing timing of harmonic-mode imaging according to a filtering technique in the conventional ultrasonic diagnostic apparatus.
In
FIG. 15
, a harmonic component is indicated by a solid line and a fundamental component by a broken line because the harmonic component is principal and the fundamental component is subsidiary in the harmonic mode. Moreover, the gain is increased to acquire large harmonic components that are inherently small, and accordingly, the fundamental components become larger.
The timing for transmitting the ultrasonic pulses in
FIG. 15
is exactly the same as that in the B mode shown in FIG.
14
.
FIG. 16
is an explanatory diagram showing timing of harmonic-mode imaging according to a phase inversion technique in the conventional ultrasonic diagnostic apparatus.
When a first ultrasonic pulse fs+ with a relatively shallow focus is transmitted at a time t1, the fundamental component of received data indicated by the broken line in
FIG. 16
has an intensity decreasing over time with a maximum at the time t1. The harmonic component of the received data indicated by the solid line has an intensity rapidly decreasing over time with a maximum slightly after the time t1.
When a second ultrasonic pulse fs− with a relatively shallow focus and of a phase opposite to that of the first ultrasonic pulse fs+ is transmitted at a time t2 after a time period &tgr;s from the time t1 as in the B mode, the fundamental component of received data indicated by the broken line in
FIG. 16
has an intensity decreasing over time with a maximum at the time t2. The harmonic component of the received data indicated by the solid line has an intensity rapidly decreasing over time with a maximum slightly after the time t2.
Adding the first and second received data, the fundamental components are canceled out because their phases are opposite, and the harmonic components are doubled because they are in phase. That is, solely the harmonic components can be obtained.
When a first ultrasonic pulse fm+ with a relatively intermediate focus is transmitted at a time t3′ after a time period &tgr;s from the time t2 as in the B mode, the fundamental component of received data indicated by the broken line in
FIG. 16
has an intensity decreasing over time with a maximum at the time t3′. The harmonic component of the received data indicated by the solid line has an intensity rapidly decreasing over time with a maximum slightly after the time t3′.
When a second ultrasonic pulse fm− with a relatively intermediate focus and of a phase opposite to that of the first ultrasonic pulse fm+ is transmitted at a time t4′ after a time period &tgr;m from the time t3′ as in the B mode, the fundamental component of received data indicated by the broken line in
FIG. 16
has an intensity decreasing over time with a maximum at the time t4′. The harmonic component of the received data indicated by the solid line has an intensity rapidly decreasing over time with a maximum slightly after the time t4′.
Adding the first and second received data, the fundamental components are canceled
Amemiya Shin-ichi
Hashimoto Hiroshi
Armstrong Teasdale LLP
GE Medical Systems Global Technology Company LLC
Horton Esq. Carl B.
Imam Ali M.
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