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

6
ABDOMINAL ULTRASOUND
A
B
Figure 1.9 Flow velocity waveforms of hepatic arteries. (A) High-resistance flow with low end-diastolic flow (EDF)
and a dichrotic notch (arrowhead). The clear ‘window’ during systole (arrow) indicates little variance, with the blood
flowing at the same velocity throughout the vessel. During diastole, the area under the envelope is ‘filled in’, indicating
greater variance in flow. (B) By contrast, this hepatic artery trace indicates low-resistance flow with good EDF and no
notch. Variance is apparent throughout the cycle.
Figure 1.10 On the left, the portal vein appears to
have no flow (arrow) when it lies at 90˚ to the beam—a
possible misinterpretation for thrombosis. When scanned
intercostally, the vein is almost parallel to the beam and
flow is easily demonstrated.
flow in difficult-to-access vessels. Doppler is
known to produce false-positive results for vessel
occlusion (Fig. 1.10) and the operator must avoid
the pitfalls and should ensure that the confidence
levels are as high as possible (see Box 1.2).
CHOOSING A MACHINE
The ultrasound practitioner is confronted with
a confusing range of equipment and choosing
the right machine for the job can be a daunting
task.
An informed and useful choice is more likely
when the purchaser has considerable experience
within the particular clinical field. Many machines,
purchased in the first enthusiastic flush of setting
up a new service, for example, turn out to be
unsuitable two or three years later.
Mistakes are made by insufficient forward planning.
A number of machines (usually at the
cheaper end of the market), though initially purchased
for specific, sometimes narrow, purposes,
end up being expected to perform more complex
and wider-ranging applications than originally
planned.
Take careful stock of the range of examinations
you expect your machine to perform. Future developments
which may affect the type of machine you
buy include:
●
Increase in numbers of patients calculated from
trends in previous years.