Cirs ATS539 - Establishing a Baseline; System Settings for Each Measurement; Baseline Measurements; Allowable Deviation from Baseline Measurements

3
ESTABLISHING A BASELINE
Before performing routine quality assurance measurements, establish:
1. System settings for each measurement:
System setup can have a dramatic impact on the results obtained from quality as-
surance measurements. You must establish and record what system settings
should be used for each of the quality assurance tests. These same settings
should be used each time the test is performed. If not, then the conclusions
drawn may not be valid. CIRS recommends that you use the most commonly
used settings for the type of probe tested- i.e. the liver preset values for an abdominal
probe- which are called a "normal" technique in the sections that follow.
2. Baseline measurements:
The rst 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 inuence 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 determine.
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.