9%20ECOGRAFIA%20ABDOMINAL%20COMO%20CUANDO%20DONDE

14
ABDOMINAL ULTRASOUND
include staff issues (such as education and training,
performance and continuing professional development),
patient care, the work environment (including
health and safety issues) and quality assurance
of equipment. Quality assurance checks on ultrasound
equipment, unlike most other aspects of an
ultrasound service, involve measurable and reproducible
parameters.
Equipment tests
After installation, a full range of equipment tests
and safety checks should be carried out and the
results recorded. This establishes a baseline performance
against which comparisons may later be
made. These tests should normally be carried out
by qualified medical physicists.
It is useful to take a hard-copy image of a tissuemimicking
phantom, with the relevant settings
marked on it. These images form a reference against
which the machine’s subsequent performance can
be assessed. If your machine seems to be performing
poorly, or the image seems to have deteriorated
in some way, you will have the proof you require.
A subsequent, regular testing regime must then
be set up, to ensure the standards of quality and
safety are maintained. This programme can be set
up in conjunction with the operators and the medical
physics department and relevant records
should be kept. The use of a tissue-mimicking
phantom enables the sonographer to perform certain
tests in a reproducible and recordable manner
(Fig. 1.12).
Checks should be carried out for all probes on
the machine.
Suggested equipment checks include:
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caliper accuracy
system sensitivity and penetration
axial and lateral resolution
slice thickness
grey scale
dead zone
checks on the various machine controls/functions
output power
safety checks: electrical, mechanical, biological
and thermal, including a visual inspection of all
probes and leads
imaging device checks for image quality, settings,
dynamic range, functionality and electrical
safety
A
B
Figure 1.12 Tissue-mimicking phantom. (A) When using a high-frequency linear array, cross-sections of the wires in
the phantom are clearly demonstrated as small dots. (B) When using a curved array of a lower frequency, such as that
used for abdominal scanning, the lateral resolution is seen to deteriorate in the far field as the beam diverges. The
wires are displayed correctly in the near field but appear as short lines in the far field. Spacing of the wires is known,
allowing caliper accuracy to be assessed.