Potential Sources Of Error During Scanning - Siemens ACUSON Cypress Operator's Manual

Safety, Technical Description, and Accuracy
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Potential Sources of Error During Scanning

Table 57 shows the potential sources of error when conducting scans.
Potential Sources of Error
TABLE 57.
Source Explanation of Error(s)
Patient The technical difficulty of patients varies widely. Greater care
Variability
must be taken with technically difficult patients to obtain the best
images possible with the most optimum system control settings.
Operator The skill, care, and experience of the person conducting the scan
Variability
is one of the most critical factors in obtaining accurate measure-
ments. Operator training should be consistent with the recom-
mendations of the relevant professional medical societies.
Speed of The image processing and measurement algorithms of diagnostic
Sound
ultrasound assume that the speed of sound in body tissue is
1540 meters per second. Different types of body tissue have dif-
ferent sound speeds. In soft tissue there is approximately a 2%
error; this may be as high as 5%, especially if fatty tissue is
present in the area of the image being measured.
Doppler When performing Doppler scans try to align the beam as close to
Alignment
parallel to flow as possible. Misalignment errors are typically
approximately ± 5%. Most cardiac clinical references assume
that the angle is under 20°.
Clinical Numerous clinical references and studies have been published
References
which establish the accuracy of calculations formulas and algo-
rithms. It is important to be familiar with these references and
their descriptions of accuracy issues and limitations. These stud-
ies also describe any assumptions that may be made in the
development of the clinical formula. The calculations formulas
used in the Cypress system are derived solely from such pub-
lished data, and references are provided in the calculations sec-
tion of the manual.
Screen The display screen provided in the Cypress system is comprised
Pixel
of a rectangular array of square picture elements (pixels). Mea-
Resolution
surement pixel resolution is assumed to be ± one pixel. The max-
imum potential error of this resolution accuracy is 0.4%.
ACUSON Cypress™ Operator's Manual