Users may need help reading their phantom with the 390/391
When the X-Rite 390 and 391 scanning medical densitometers were introduced they touted a new feature - the ability to read the MQSA required Mammographic Accreditation Phantoms in a single pass. This was possible due to the fact that ACR recommended that the acrylic disk (phantom disk) was to be placed in the geometric center of the phantom. Placement of the disc has changed to a location between the first two fibers as shown in the image below. As a result, two passes will be required to successfully read the current Mammographic Accreditation Phantom. Follow these steps:
From the densitometer's Main Menu, press [p1] and then [p2] to access the Function Menu. Select [QC] and then [phtm]. If prompted to "Select Phantom", press the first key until "N. American" appears and then select [ok].
In the resulting "Phantom" menu, select [read]. "Insert Strip" will appear on the display.
Perform the first pass measurement thru the center of the acrylic disk as indicated in the image below. The film should be inserted with the emulsion side down. It might be necessary to trim the top of the film in order to adjust the Film Guide to center the acrylic disk image under the Alignment Line. There are a few important points to consider when reading phantoms:
There must be at least one inch of leader from the film edge to the phantom edge.
Path to the acrylic disk image must be unobstructed! That is, there cannot be any artifact of any kind in the measurement path to the disk image.
Path thru the Center Background must be unobstructed as well.
After successfully reading the acrylic disk, the display will prompt the user to "Insert Strip" once again. Set the Film Guide to allow an unobstructed path thru the Center Background as indicated in the image below.
Disk Density, Near Disk Density, Density Difference, and Center Background Density will be reported.Select [next] in each window to toggle to the next data field.
Enter the appropriate number of Fibers, Specks, Masses, and Total Number of Objects to complete the process.
If unable to successfully read a Mammographic Accreditation Phantom with this suggested procedure, using the 390/391 spot reading technique might be the only available procedure to follow. Click on the link on the bottom of this page entitled: "Taking Spot Readings with the 391" for instructions on how to spot read with the 390/391.
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