o_1977r8vv9vk1ts2ms0kd8pksa.pdf

a Chapter 34 Four-Dimensional B-Mode and Color Doppler Echocardiography of the Human Fetus 511
Fig. 34.3. Microscopic view of a matrix array transducer. Each
small square is an active ultrasound element. The size of a
human hair is shown for comparison (arrows). (From [9])
ume of data thus generated offer a formidable challenge
in real-time processing; however, the system resolves
this issue by devising a highly innovative technological
solution known as subarray beam forming
(Fig. 34.4). The elements are connected via layers of
wiring to several custom integrated circuits. The currently
marketed device uses many such circuits which
are located in the handle of the transducer which itself
still remains very modest in size. These circuits
perform the initial processing of the ultrasound signals
which are then transmitted to the main computer
system of the device where further fast processing results
in the real-time on-line generation of moving
cardiac images. The system allows color Doppler flow
depiction in real time in conjunction with the 4D depiction
of cardiac anatomy.
Fig. 34.4. Graphic depiction of the concept of subarray
beam forming
The system generates a 3D pyramid-shaped volumetric
sector restricted to an angle of about 308±508
(Fig. 34.5). No gating is needed for this volume. A
wider pyramidal sector image measuring 90 ´908 can
also be produced. This is accomplished by swift automatic
acquisition and integration of four sectors in real
time during consecutive cardiac cycles with each sector
measuring approximately 23 ´908; however, generation
of the extended sector requires some form of cardiac
gating which in the adult or pediatric patient is provided
by a modified type of electrocardiographic trigger.
Although this is not feasible to accomplish in the
fetus, an external electronic periodic trigger, which
Fig. 34.5. Two-dimensional matrix array:
the sector size. a On-line 3D scanning.
The sector size depends on chosen
image resolution or line density,
and is about 30 ´ 508. b Wide-angle
scanning. An arrow sector is scanned
during each of four consecutive heart
beats. The four sectors (shown with different
color coding) are integrated
automatically within a fraction of second.
(From [9])