Abstract
Ultrasound scanners can be used for displaying the distribution
of velocities in blood vessels by finding the power spectrum of
the received signal. It is desired
to show a B-mode image for orientation and data for this has to
be acquired interleaved with the flow data. Techniques
for maintaining both the B-mode frame rate, and at the same
time have the highest possible $f_{prf}$ only limited by the
depth of investigation, are, thus, of great interest.
The power spectrum can be calculated from the Fourier
transform of the autocorrelation function $R_r(k)$.
The lag $k$ corresponds to the difference in pulse number,
so that for lag $k$ data from emission $i$ is correlated with $i+k$.
It is possible to calculate $R_r(k)$ for
a sparse set of emissions, as long as all combinations of
emissions cover all lags in $R_r(k)$. A
sparse set of emissions interleaved with B-mode emissions can,
therefore, be used for estimating $R_r(k)$.
The approach has been investigated using Field II simulation
of the flow in the carotid and femoral arteries.
A 5 MHz linear array transducer with
128 elements, a pitch of $\lambda$ and an element height
of 5 mm was simulated. The autocorrelation was calculated
from the sparse sequence and averaged over a pulse length.
The 1:2 sequence using 2 flow emission for one b-Mode emissions
showed a nearly indistinguishable
spectrum compared to a Fourier spectrum calculated on the full
data. The sparser sequences give a higher noise in the
spectrum proportional to the sparseness of the sequence.
The audio signal has also been synthesized from the autocorrelation
data by passing white, Gaussian noise through a filter designed
from the power spectrum of the autocorrelation function.
The results show that both the full velocity range can be maintained
at the same time as a B-mode image is shown in real time, where
the trade-off between B-mode frame rate and spectral accuracy can be
selected.
Original language | English |
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Title of host publication | 2005 IEEE Ultrasonics symposium |
Volume | 1-4 |
Publisher | IEEE |
Publication date | 2005 |
Pages | 141-145 |
ISBN (Print) | 0-7803-9382-1 |
DOIs | |
Publication status | Published - 2005 |
Event | 2005 IEEE Ultrasonics Symposium - Rotterdam, Netherlands Duration: 18 Sept 2005 → 21 Sept 2005 http://ieeexplore.ieee.org/xpl/mostRecentIssue.jsp?punumber=10674 |
Conference
Conference | 2005 IEEE Ultrasonics Symposium |
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Country/Territory | Netherlands |
City | Rotterdam |
Period | 18/09/2005 → 21/09/2005 |
Internet address |
Series | I E E E International Ultrasonics Symposium. Proceedings |
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ISSN | 1051-0117 |
Keywords
- Medical
- Velocity estimation
- Ultrasound