No manufacturer is able to produce all batches of film with exactly the same speed, contrast, D-Max, Base+Fog, etc. From one batch to the next there will typically be some small shifts in the emulsion's reaction to exposure and processing. A crossover is performed to identify and compensate for these small inconsistencies. The Fall issue (1998) of "Mammography Matters" (Volume 5, Issue 4), includes a concise article by Orhan H. Suleiman, Ph.D., Chief Radiation Programs Branch, Division of Mammography Quality and Radiation Programs. In brief, Dr. Suleiman reminds us that crossovers are NOT performed to solve processor problems; rather the processor must be in control before a crossover is performed. Take a few minutes to visit the link and download a copy of this paper.
Begin the procedure by preparing a set of films as follows:
Expose and process 5 control strips from the old batch and 5 control strips from the new batch on the same day.
Select the channel normally used for daily processing.
Select [p1] to go to [p2] and then select [ref].
Press either [MENU] button that is under [x-over].
"Read OLD strips:" will temporarily display and then "READ REF STRIP #1".
Read the first of the five old control strips. When prompted to read the remaining four old strips, insert the strips.
"Read NEW strips:" will temporarily display and then "READ REF STRIP #1".
Read the first of the five new control strips. When prompted to read the remaining four old strips, insert the strips.
"INSTALLING CROSSOVER REFERENCE" will temporarily appear and then the new references.
View the new references if desired and then hit both [MENU] buttons to return to the "MAIN MENU" for measuring.
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