GammaVision
®
v7 (A66-BW) 783620H / 1013
3) Analyzing the QA database and generating reports. This includes GammaVision’s Status and
Control Chart features, which allow you to view the current status of measurements for the
Detector and/or view and print the data stored in the database as a control-chart display.
8.2.1. Settings...
The QA settings include the upper and lower radionuclide activity limits which, when exceeded, indicate that the system is not operating correctly. There are two levels of limits. The
warning
limits are determined by the settings in the Low and High fields in the Quality Assurance Settings dialog in Fig. 281. The alarm limits those outside of the Minimum and Maximum fields.
If the result of a QA measurement is outside the warning limits, a warning dialog is displayed. If the QA result is outside the alarm limits, a violation dialog is displayed. Moreover, if the Lock
Acquire on Violation(s) box is marked, the violation must be corrected and the QA measurement repeated before the out-of-limits Detector can be used to collect more data.
Generally, after setup, these levels should not be changed without careful consideration.
NOTE
If the “Unable to Access QA Database” message is displayed when you issue the
Settings... command, the QA database file
GvQa32.Mdb
is not currently located in the folder in which it was originally created (i.e., it has been moved, renamed, or deleted).
See Section 8.4.
8.2.1.1. Establishing QA Settings
Click Settings... to open the Quality Assurance Settings dialog shown in Fig. 281. This dialog contains three main data-entry areas:
! BACKGROUND Acquisition time and Count Rate Limits
! SAMPLE Type Analysis Settings File
! SAMPLE Analysis Parameter Limits
Several preliminary steps must be taken to determine the QA settings:
1) Backgrounds must be counted to determine reasonable levels.
2) Samples must be counted for total activity to obtain expected values, since total activity is detector and QA source dependent.
3) A QA library containing only the nuclides in the QA source must be created using the nuclide library editor (see Section 5.6).
362
783620H / 1013 8. QUALITY ASSURANCE
4) A sample type settings file (
.SDF
) must be created which contains the defaults for the QA acquisition and analysis (see Section 5.5.1.1).
Fig. 281. QA Settings Dialog.
5) A QA database file must exist. The GammaVision QA database,
GvQa32.Mdb
, is installed as part of the standard GammaVision installation, and should be located in the
\User
directory on the drive where GammaVision was installed. However, if you select the Settings... command and GammaVision cannot find
GvQa32.Mdb
(or if the database file cannot be used for some reason), a warning message will ask if you wish to create a QA database. Click OK to start the QA database setup wizard and go to Section 8.4 for instructions. When the database has been successfully created, you will be automatically returned to the Quality Assurance
Settings dialog.
All the information gathered in preliminary Steps 1–4 can be entered in the Quality Assurance
Settings dialog.
The BACKGROUND Acquisition time and Count Rate Limits are entered using the information gathered in Step 1 above. Enter the Real time or Live time in seconds; for background spectra, the dead time is near zero, so these are usually equal.
363
GammaVision
®
v7 (A66-BW) 783620H / 1013
The Minimum and Maximum count-rate limits are the acceptance thresholds for the alarm limit. Acceptance thresholds are used to indicate that the system is operating far from the expected conditions, and can be used to prevent data acquisition from being performed at all until the condition is corrected. If the Lock Acquire on Violation(s) box is marked and an acceptance threshold is exceeded, the Detector is automatically locked out from use until the problem is corrected and QA is rerun. The Low and High count-rate limits are the warning limits, and exceeding them will cause warning messages to be displayed.
The Background Report is printed after the analysis if you mark the Create Background
Report checkbox. The report can either be saved to disk or printed.
The SAMPLE Type Analysis Settings File is the
.SDF
file created for QA in Step 4 using
Analyze/Settings/Sample Type.... Click Browse... to select the
.SDF
file. To edit the
.SDF
file, click Edit.... This will open the Analysis Options dialog (see Section 5.5.1.1). Especially relevant sample type settings include:
! Sample type description
! Acquisition presets
! QA nuclide library file (the one created in Step 3)
If you wish to save or print a SAMPLE Report after the analysis, mark the Create SAMPLE
Report box.
On the left of the SAMPLE Analysis Parameter Limits section are checkboxes for marking the limits to be tracked. Total Activity (Bq), Average Peak Shift (keV), Average FWHM Ratios, and Average FWTM Ratios are the choices. Mark the limits to be tracked. The first time
GammaVision QA is set up, click the Suggest button (on the right) to enter factory-set limits.
After this, use the Suggest button with caution, because clicking on it again will reset all the limits to the previously defined settings. The actual limits can be determined from the samples counted in Step 2 above.
Click OK. GammaVision will check the measurement limits to determine if they are set consistently. If they are, the dialog will close; if not, a message will be displayed on the Marker
Information Line and the dialog will remain open so the limits can be changed. QA data can now be collected using Acquire/QA/Measure Background and Acquire/QA/Measure Sample.
364
