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Cedex HiRes Analyzer Operator’s Guide
D
D
Administrator Functions
The System Options
7.4.4. Turning off the Flow Chamber Prescan
Only cells that have settled down on the bottom of the chamber are well inside the focal plane of the scanner
and, therefore, can be analyzed with an optimal image quality. A default sedimentation time of 45 or 90 seconds,
depending on Cell Type, was selected to absolutely ensure that all of the cells from different Cell Types have
settled down to the bottom of the fl ow chamber. Larger Cell Types will settle to the bottom within 45 seconds.
However, many small Cell Types may require more time. Reducing the settings for sedimentation time will
reduce the overall measurement time. Reducing the sedimentation time, however, is not standard procedure. A
specifi c verifi cation process is required to confi rm the correct sedimentation time for a particular cell line. Local
Roche technical services needs to be consulted for detailed information on the verifi cation process.
During the sedimentation phase, a Prescan of the fl ow chamber is done and an image of the whole fl ow chamber
delivered. If the sedimentation time is reduced to below 45 seconds, the fl ow chamber Prescan may need to be
disabled since there may no longer be a suffi cient amount of time for a Prescan to be taken.
To disable the Flow Chamber Prescan, do the following:
1
Open the System Options and click on the Measurement tab.
2
Look for the parameter MeasurementPrescanRequired. Enter 0 in the Value column to disable the Prescan.
3
Click on Save to store the change.
■
If the Prescan should be enabled again, re-enter 1 in the Va l u e column of the parameter MeasurementPrescan-
Required.
The Cedex HiRes Software 2.2 requires one Prescan image to optimize the image brightness. It is necessary
to ensure that at least one Trypan blue stained sample has been run on the system before switching off the
Prescan feature.
The 45 second sedimentation time set by default for the Std. Size and Max. Size should generally allow enough
time for a prescan to be performed. In some cases of particularly slow computer systems, however, the prescan
may require slightly more time than the default sedimentation time. If this occurs, a message “Warning:
sedimentation time was exceeded” will appear in the main Cedex Control Center window. However, there
will be no effect on the measurement other than slightly longer sedimentation time. The sedimentation time
for the Std. Size and Max. Size can be increased, if desired, in order to have a sedimentation time that is
longer than the prescan time (see “Editing an Existing Cell Type”).
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