[Coded excitation medical ultrasound imaging]
Pulse compression techniques were developed mainly for radar systems. And the technology allows a radar to utilize a long pulse to achieve radiated energy, but simultaneously to obtain the range resolution of a short pulse. It accomplishes this by employing frequency or phase modulation to widen the signal bandwidth. Coded excitation is an ultrasound technique which has only been made commercially available in the last 3 years. It improves SNR without loss of resolution by transmitting a long binary phase-encoded pulse sequence and then compressing its echo into a short, high-amplitude pulse on receive. Different types of codes, e.g. Golay, may be used to suppress range side lobes. And a new technique called B-Flow for imaging blood flow also uses advanced digital signal encoding/decoding techniques to provide direct visualization of blood echoes. Coded excitation together with tissue equalization forms the basis for B-Flow, which extends the wideband resolution and high frame rate capabilities of B-mode to flow and tissue imaging. A key aspect of B-Flow is tissue equalization, which uses decoding to preferentially reduce non-moving tissue signals to the level of the flow signal such that both may be displayed simultaneously without machine prioritization and overlay (as in color flow).
Jibiki
Takao
T
Ultrasound Laboratory, GE Yokogawa Medical Systems, Ltd. takao.jibiki@gemsa.med.ge.com