Image Properties Panel

The opportunity to modify parameters, such as spacing and the data offset and slope, is available in the Image Properties panel. In the Advanced Properties panel, you can modify an object's position in space and change its orientation.

Right-click the required data in the Data Properties and Settings panel and then choose Image Properties in the pop-up menu to view the Image Properties panel, shown below.

Image Properties panel

The information available for the selected dataset includes its geometry, physical size, and spacing values.

Image properties
  Description
Object Indicates the name of the selected dataset.
Geometry Indicates the dimensions of the selected dataset.

X, Y, Z… Indicates the number of pixels along each axis and the length of each axis. Length is calculated for each axis as [(number of pixels)*(spacing)].

T… Indicates the number of time steps in the dataset.

Note For information about cropping a dataset, refer to the topic Cropping Datasets.
Physical size Provides information about the physical size of the selected dataset.

Type*… Indicates the primitive data type, either Unsigned character (UBYTE), Unsigned short (USHORT), Unsigned integer (UINT), or Float. Refer to the topic Converting Image Data for information about converting image data.

Bytes*… Indicates the number of bytes for each voxel, either 1 for UBYTE, 2 for USHORT, or 4 for Float.

Total size*… Indicates the total byte count.

Volume… Indicates the total volume occupied by the dataset, which is calculated as voxels*(pixel size cubed).
Spacing Indicates the spacing between pixels along each axis. If required, image spacing can be modified (see Modifying Spacing).
Intensity* Indicates the offset and slope values, as well as the selected unit.

Offset*… Indicates the applied offset. Offset shifts the transfer function up or down while holding the slope constant to control the brightness of an image (see Modifying Data Offsets and Slopes).

Slope*… Indicates the applied slope. Slope changes the slope of the transfer function without shifting the black level established by the offset value. This controls the contrast of an image (see Modifying Data Offsets and Slopes).

Unit… Lets you assign dimension (physical) units to a dataset. For example, to images created from multi-ROIs with scalar values (see Assigning Units to Scalar Values). Units are available in the drop-down menu, as shown below.

Note Applying a dimension unit is not a calibration, it is just an assignment.

Reset Calibration… Resets calibrated values to their original values.
Advanced Properties Opens the Advanced Properties dialog, in which you can modify an object's position in space and change its orientation (see Advanced Dataset Properties).

* Available for image data only.

If required, you can modify spacing by entering new values for the X, Y, Z axes in the Spacing box on the Image Properties panel.

Changes to image spacing will be applied directly to the dataset and its dimensions will be modified.
How to Modify Spacing
  1. Right-click the required dataset in the top section of the Data Properties and Settings panel and then choose Image Properties in the pop-up menu.

    The Image Properties panel appears on the Dataset Tools tab.

  2. Enter the required spacing values for the X, Y, Z axes in the Spacing box.
  3. Click the Apply button.
  4. Save the modified file, if required.

Offset and slope are basic transfer functions. Offset shifts the transfer function up or down while holding the slope constant to control the brightness of an image while maintaining contrast. In this case, the output is computed as [(input) + (offset)]. Slope changes the slope of the transfer function without shifting the black level established by the offset value. This controls the contrast of an image and is computed as [ (input)*(slope)].

The effect of modifying an image's offset and slope is shown in the following intensity profile of the original image data and the image data with an offset and slope applied.

Intensity profile

Intensity profile

You should note that the nominal values for offset and slope are 0 and 1, respectively. However, you should also note that medical CT scanners are normally calibrated with reference to water and that image data from these devices is represented by the Hounsfield unit (HU) scale with a typical offset of -1000.

You can also apply an intensity calibration to ensure that the intensity values of different materials or tissue are consistent, regardless of the sample acquired (see Intensity Scale Calibration). Intensity calibration automatically computes a slope/offset transformation so that the selected standard intensity values will be obtained from the raw intensity values.
How to Modify Data Offsets and Slopes
  1. Right-click the required image data in the top section of the Data Properties and Settings panel and then choose Image Properties in the pop-up menu.

    The Image Properties panel appears on the Dataset Tools tab.

  2. Enter the required data offset and/or slope values in the Data box.
  3. Click the Apply button.
  4. Save the applied changes, if required.