Cenova Image Analytics Server 3.0 Installation & Service Manual
Chapter 3: Installing the System
MAN-05205 Revision 003
Page 63
Note
Be aware of the following:
•
If DigitalNow HD has been configured to apply one of the image-
processing options to the digitized images, then the original images will be
lost unless they have been archived.
•
DigitalNow HD images in which image processing has been applied cannot
be reprocessed by DigitalNow HD.
Depending upon the preferences of site personnel, you can set DigitalNow HD to bypass
the image-processing options so that the pixel values in the output image are affected
only by the selected output resolution.
VOI LUTs
A value-of-interest look-up table (VOI LUT) is a transform that maps each grayscale pixel
value to a new value. DigitalNow HD can encode a set of four VOI LUTs into the DICOM
header of each image. The VOI LUTs help compensate for variations in film type, breast
composition, and film exposure, essentially fine-tuning the appearance of the images in a
study.
Note
Use of VOI LUTs during display requires a workstation that can apply them. Review
the documentation provided by the vendor to see if the site’s workstation make, model,
and version has this capability.
The four VOI LUT selections are intended for:
•
Normal breasts – Used to visualize most normal tissue, assuming the original film
was well exposed.
•
Dense breasts – Stretches image contrast in dense areas of the breast. It is used much
like a soft-tissue or bone window when viewing CT slices.
•
Overexposed films – Provides high contrast in the darker regions of a film image to
bring out otherwise hidden tissue.
•
Underexposed films – Provides high contrast in extremely bright regions of a film to
bring out otherwise hidden tissue.
The content of the VOI LUTs provided by DigitalNow HD is based on the image
processing selection (above) and the film scanner from which the source image was
created. The film scanner type is encoded in the header of the source DICOM image.
Workstations such as Hologic SecurView DX initially display DigitalNow HD images
with the Normal VOI LUT. To improve the appearance of the images, the reader can
apply an alternative VOI LUT to the study. With advanced workstations, the reader can
further modify the appearance by manually adjusting the window width / window
center values for each individual image
