Fluke Biomedical 84-340 - Manual (Page 9)

Testing Procedures
Testing Procedures
2
2-1
Section 2
Testing Procedures
2.1 Testing Procedures
Dead-Zone Identification
The transducer should be placed firmly above the near field resolution target and perpendicular to the
wire plane. Dead-zone or the ring down distance can be defined as that distance between the
transducers face and the closest wire target to be resolved from the reverberation. If the first target to be
resolved is at 4 mm then the dead-zone distance is “something less than 4 mm.”
Assessment of Resolution
These measurements should be done at several sensitivities and depth levels to facilitate a thorough
evaluation. As defined by the AIUM standards committee, lateral resolution “at specified control settings
and range is the minimum lateral distance between two identical reflectors or scattering volumes at which
separate registrations can be clearly distinguished on the display.” Measurements should be made at
both 3 and 10 centimeters deep. Closer positioning of the transducers focal point to each target group
should result in better resolution. Assessment of vertical resolution should be done in the same manner
as assessment of lateral resolution using the vertical resolution target that is located approximately 30
mm from the scanning surface.
Depth Calibration
This measurement should be performed using the vertical plane targets. This group of wires should be
scanned linearly and perpendicular to the target plane. All wires should be displayed simultaneously
Measure the distance between two targets using the display markers and plot the values as a function of
true distance which is known to be 20 mm. Or, more simply, align the echoes to the display markers for
comparison.
Beam Width Measurement
A linear scan should be performed perpendicular to the vertical plane target. Some of the monofilament
wires are displayed as lines rather than points. The determined length of these displayed lines
demonstrates beam width as a function of depth in 2 cm increments.
Time-gain properties and sector scanner errors can be
evaluated using the vertical plane target in accordance
with suggested AIUM techniques. For targets with
minimum scattering, lower gain levels can be used,
however, higher gain settings enable evaluation at more
clinical type settings. When evaluating any machine,
settings should be recorded and remain consistent over
time. For further instruction on measuring performance
refer to Standard Methods for Measuring Performance of
Pulse-Echo Ultrasound Imaging Equipment, AIUM
Standards Committee, July 1990.
NOTE