5
2. Baseline measurements:
The first set of measurements taken will be the baseline measurements for the
combination of system settings and phantom. Record the system settings and
phantom serial number used to acquire each measurement along with
your measurement results. On subsequent scans, refer to the baseline results
to determine if the ultrasound system has drifted to an unacceptable level. It is
each facility's responsibility to establish the magnitude of drift allowed
before corrective action is warranted.
3. Allowable deviation from baseline measurements:
The difference between the original baseline measurements and subsequent
measurement should be calculated and recorded. At some point the difference
will be large enough that some action is required (call service, replace system,
etc.). Each facility needs to determine the action level for each test. You should
refer to the user’s manual of your ultrasound scanner and note the stated
accuracies of the system’s general imaging measurements. These stated ac-
curacies may greatly influence the conclusion made when evaluating the ultra
sound system. For example, if the measurement accuracy for your system
is 10% for distances up to 2 cm, the scanner may detect 2.0 cm as being any
where from 1.8 cm to 2.2 cm and still be functioning properly. The user is
responsible for establishing action levels.
4. Frequency of system assessment:
How often each system is evaluated is also up to each facility to deter
mine. CIRS recommends at least annually.
Reference the accreditation programs established by the ACR and AIUM at
www.acr.org or www.aium.org for further guidance on establishing a QA program.
TESTING PROCEDURES
The following sections outline procedures for performing routine quality control tests
with the imaging targets within the Model 055A. It may be useful to refer to the
target map, shown in the Specifications section, when reviewing these procedures.
DISTANCE
A vertical distance is defined as the distance along the axis of the beam. The verti-
cal wire targets are used to assess the accuracy of vertical distance measurements
as follows:
1. Apply coupling gel to the scanning surface or fill the water trough with tap
water.
2. Position the transducer in a vertical plane. (The wires should appear as dots,
not lines).
Do not apply excessive pressure as this may temporarily
compress the target and skew the measurements.
3. Adjust the instrument settings (gain, TGC, output, etc.) as for a “normal”
technique. Record these settings for use on subsequent testing.