Efficient Dynamic Focus Control for Three-Dimensional Imaging Using Two-Dimensional Arrays
Resource
lEEE TRANSACTIONS ON OLTRASONICS, FERROELECTRICS, AND FREQUENCY CONI'HOL, VOL. 49, NO. 9, SEPTEMBER 2002
Journal
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Journal Volume
VOL. 49
Journal Issue
NO. 9
Pages
-
Date Issued
2002-09
Date
2002-09
Author(s)
Huang, Jing-Jung
DOI
246246/200611150121604
Abstract
Dynamic receive focusing in ultrasonic array
imaging involves extensive real-time computations and data
communication. Particularly for three-dimensional imaging,
using fully sampled, two-dimensional arrays, implementation
of dynamic focusing can he extremely complicated hecause
of the large channel count. In this paper, an efficient
dynamic focus control scheme for a delay-and-sum-based
beamformer is proposed. The scheme simplifies dynamic
focus control by exploiting the range-dependent characteristics
of the focusing delay. Specifically, the overall delay
is divided into a range-independent steering term and a
range-dependent focusing term. Because the focusing term
is inversely proportional to range, approximation can be
made to simplify dynamic focus control significantly at the
price of minimal degradation in focusing quality at shallow
depths. In addition, the aperture growth controlled by
a constant fjnumbeFc an also be utilized to devise a nonuniform
quantization scheme for the focusing delay values.
Efficacy of thc proposed scheme is demonstrated using simulated
heam plots of a fully sampled, two-dimensional array.
Design procedures are also described in detail in this paper.
One design example shows that, with the proposed dynamic
focus control scheme, a 4096-element array only requires
227 independent controllers for the range-dependent
focusing term. Moreover, only 28 non-uniform quantization
levels are required to achieve the same focusing quality as
that of a conventional scheme with 784 uniform quantization
Icvels. The beam plots of a fully sampled array show
that sidelobes are slightly increased helow the -30 dB level
for imaging depths less than 3 cm. At greater depths, there
is no observable degradation.
Subjects
ear
bacteriology
methicillin resistance
Staphylococcus aureus
Publisher
Taipei:National Taiwan University Dept Elect Engn
Type
journal article
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