Add/Subtract Images - GE Revolution CT User Manual

Allows negative pixel values in the images. If not enabled, all negative pixel values are set to
zero. This operation is useful on pre- and post-contrast studies of the same slice location. This
checkbox displays only when you press the minus button.
Illustration 8: Add/Subtract window with Minus mode button selected showing Accept Negative
Disable Normalization
Performs a pixel-by-pixel addition or subtraction. The images are not normalized.
•
Disable Normalization is available for both addition and subtraction.
• If Accept Negative Pixels is not selected the negative pixels are scaled to zero and the
resultant images are clipped to 16–bits if they go beyond the bounds of 16–bit images.
•
If both Accept Negative Pixels and Disable Normalization are selected, then Add/Subtract
accepts input of negative pixels and performs a true pixel-by-pixel subtraction. A message
displays if any overflow beyond the 16–bit image size occurs.
Clear Selection
Clears the values associated with the [Select Set] buttons.

2.3 Add/subtract images

To create a new image set, for example add thin slices together or subtract pre/post contrast
series, follow the steps below. Processed images will be annotated with the date.
1. In File Manager, highlight the exam you want to work with, right click and select [Add/Sub] to
Image Combination window. Alternatively, highlight the series you want to work
open the
with, right click and select [Open with], then [Add/Sub].
2. Select the images.
○
If one set is selected, each operation produces one resulting image.
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Pixel box
Revolution CT User Manual
2 Add/Subtract