2 Add/Subtract
Considerations:
•
Add/Subtract can process a maximum of 1,000 images. To select a range of images, select
the first image in the range, hold the shift key and select the last image in the range.
•
Add/Subtract images are displayed in the series type column of the Series list as either
processing pairs (Proc) or combination (Comb).
○
Proc is the result of processing pairs of images that have identical locations in the
patient’s body. Proc series can be used like any other series of acquisition images, for
example, geometrical measurements, reformatting, 3D reconstructions, etc.
○
Comb is the result of a combination of images having different locations in the patient’s
body. The absolute anatomical coordinates accompanying Comb series are not accurate
and therefore only relative geometrical measurements (for example, distance, angle or
area) made within a resulting image are accurate.
2.1 Add/Subtract basic terminology
Term Definition
Image addition Adds image intensity values pixel by pixel and is useful for adding thin slices together to get
a thicker slice.
Image subtraction Subtracts image intensity values pixel by pixel and is useful to evaluate contrasted vessels.
NOTE:
Patient movement and breathing between the images can affect the quality of
the subtraction.
Maximum pixel value extraction Locates maximum image-intensity values pixel by pixel. This is useful for contrasted vessels
or calcifications.
Minimum pixel value extraction Locates minimum image intensity values pixel by pixel. Useful when evaluating soft tissue.
Binding Series Creates a new series consisting of copies of selected images from one or more existing ser‐
ies. Useful if you have images in two separate series and want them in one series to perform
3D or Reformat.
NOTE:
Save State information is not maintained in the new series generated with
Binding Series.
Accept negative pixels Allows negative pixel values in the resulting image, otherwise all negative pixel values are
set to zero.
Ratio slider When both [Select Set] buttons are used during addition or subtraction, equal weighting is
applied to the two pixels in each pair. You can change that with the
Ratio
slider.
Disable Normalization Performs a pixel-by-pixel addition or subtraction. The images are not normalized.
2.2 Add/Subtract and Image Combination window
In File Manager, highlight the exam you want to work with, right click and select [Add/Sub].
Alternatively, highlight the series you want to work with, right click and select [Open with], then
[Add/Sub]. You can do the same for individual images. Highlight the image you want to work
with, right click and select [Open with], then [Add/Sub]
Revolution CT User Manual
Direction 5480385-1EN, Revision 1
412 2 Add/Subtract
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