Frequency Dependence Of Resolution; Manually Guided B Image; Time-Motion Mode (M Mode) - 3B SCIENTIFIC PHYSICS U10010 Manuel De L'utilisateur

4.8 Frequency dependence of resolution

Two small discontinuities situated close together in a
specially manufactured test body (see section 4.9) can
be used to demonstrate the frequency dependence of
resolution.
The discontinuities are investigated using a 1-MHz and
a 4-MHz transducer and the ability to separate the two
locations is compared for the two frequencies. The
amplitude signals for both frequencies are shown in
the following diagrams. The top one is the display for
the 1-MHz transducer and the lower is for the 4-MHz
transducer.

4.9. Manually guided B image

A test body with discontinuities can be used along with
the built-in B-Image software feature to demonstrate
how a B (brightness) image is generated from an am-
plitude signal.
The 1-MHz transducer (U10015) is slowly and evenly
guided over the test body as in the following illustra-
tion.
The software converts the amplitude scan into a two-
dimensional brightness display.
At each of the various discontinuities, the focus of the
ultrasonic transducer, the position resolution and im-
age errors (such as sound shadows) can all be displayed.
4.10. Time-motion mode (M-mode)
So-called M-mode allows ultrasonic reflections from
moving boundary layers to be displayed. This can be
used, e.g. in an echocardiogram, to investigate the
valves of the heart. The heart itself can be simulated
using the heart valve model (U10029) with a rubber
membrane caused to move by a ball-shaped bellows.
The corresponding software option (M-mode) allows
the movements to be shown as a two-dimensional dis-
play.
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