GE Healthcare Brivo XR118 Service Manual page 152

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10.4 Background Material
1.) Definitions
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2.) PACS Test Image Features
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6
EVISION
The following are important terms or concepts
Window Center (WC): also known as Window Level (WL), controls the brightness of an image.
Typically a lower value gives a brighter image.
Window Width (WW): controls the contrast of an image. Typically a lower value gives more
contrast.
Look-up-Table (LUT): a table of input and output values that converts image pixel data to some
new value
Value-of-Interest Look-up-Table (VOI-LUT): a LUT used in many modalities to convert image
pixel data into values PACS systems can display. This table of input and output values is
stored in the DICOM header as a public field. The VOI-LUT used in DX images has an "S"
shape that mimics the H&D properties of X-Ray film. As the user changes WW or WC on the
acquisition workstation, a new VOI-LUT is calculated and saved into the DICOM header.
Linear LUT: a straight LUT where the input is linearly mapped to the output
Burn-on-Send (BOS): a mode on the acquisition workstation where the VOI-LUT is applied to
the pixel data and new pixel data is calculated. The new pixel data is sent in the DICOM image
without a VOI-LUT curve. Images are displayed on PACS with a Linear LUT, WC=8192,
WW=16383. BOS is can be configured on the Definium workstation.
DX vs. CR: the DICOM modality that images are sent as, either digital x-ray (DX) or computed
radiography (CR)
CR-Fallback: a mode on Definium workstations where if the PACS reject DX images, then CR
images are sent instead. This cannot be configured on the Definium workstation. It only occurs
if a PACS does not support DX modality images, or if the PACS is configured to reject DX
modality images.
The PACS Test Images include nine images. The pixel data in every test image is identical.
Only the DICOM headers, annotations, and WC/WW values are slightly different for each
pattern.
Each PACS Test Image consists of two aspects:
A clinical chest image on the right side with Image Number and a GE monogram watermark
A series of twelve vertical bands on the left side (Top six Dark Bands and Bottom six Bright
Bands)
Section 10.0 - PACS / Image Display Test Image
B XR118 S M
RIVO ERVICE ANUAL