bk ultrasound Flex Focus 1202, User Manual

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40 Chapter 2 December 2015 Flex Focus 1202 User Guide (BB1756-Q)
These setups have been optimized to give the best compromise between low acoustic
output and enough power to obtain the image features as quickly as possible. This is
part of the ALARA principle. The factory default setup for all transducers is B-Mode
to ensure the lowest acoustic output when you start imaging.
When you enter a new patient ID, by default the transducer setup will be reset to the
factory setup.
Fetal imaging
When you use transducers intended for fetal imaging, it is important to make sure
that the default settings are appropriate and to reset to the default setting before
imaging a new patient.
Clinical Measurements: Ranges and Accuracies
This section states the accuracies for measurements made using the BK Ultrasound
range of ultrasound systems. A table containing accuracies for specific transducers
can be found in the Technical Data (BZ2100) that accompanies this user guide.
The measurement accuracies are based on the assumption of “ideal” tissue, that is, a
tissue characterized by a sound velocity of 1540 m/s. When making clinical
measurements with ultrasound, errors may arise which are not taken into account in
this section. For example,
•
The sound velocity may vary from approximately 1450 m/s in fatty tissue to
1585 m/s in muscle. This can, in simple cases, give rise to errors of up to 6% for
linear measurements. This inaccuracy may be further increased by refraction
occurring at tissue boundaries.
•
The user can introduce errors when using approximate formulas, when
positioning the system’s calipers with respect to the ultrasound image and when
outlining structures in the image.
•
The ellipsoid volume approximation, described in this user guide, is only
applicable when the cross section of the structure being studied approximates an
ellipse (the circle being a special ellipse), and when the structure is roughly
symmetrical about the selected axis of rotation
NOTE:
The choice of the axis of rotation is important for the calculation of the
volume. A vertical axis gives a different volume than a horizontal axis.
The minimum requirement is that the cross section outlined by the user should be
convex. If the user draws a non-convex outline, an inaccuracy is introduced which is
not taken into account in this section. In this case, the system calculates and displays
the convex hull of the figure, that is, the smallest convex figure containing the non-
convex figure outlined by the user (see Fig 2-7). The system bases the calculation of
the ellipsoid volume on the convex hull.