Image Properties

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

Dataset Properties panel

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

Image properties
  Description

Name

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, which is calculated as X*Y*Z*T.

Volume… Indicates the total volume occupied by the dataset, which is calculated as voxels*(pixel size cubed).

Spacing

Indicates the spacing between voxels along each axis. If required, image spacing can be modified (see Modifying Spacing).

Data*

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. 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.

* Available for image data only.

The distance between any two slices within a volumetric dataset is referred to as the interslice distance, or spacing. If required, you can modify spacing by entering new values for the X, Y, and Z axes in the Spacing box on the Image Properties panel.

Changes to image spacing will be applied directly to the dataset and the dimensions of the volume will be modified.
  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, and/or Z axes in the Spacing box.
  3. Click the Apply button.
  4. Save the modified file, if required (see Exporting Objects).

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.
  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 (see Exporting Objects).

In the Advanced Properties dialog, shown below, you can modify an object’s position in space (also known as the point of origin) and change its orientation. You can also apply these parameters to a series of datasets to maintain consistency in the position and orientation of multiple datasets for fusion or image processing purposes.

Advanced Properties dialog

Advanced Dataset Properties dialog

If required, you can change an object’s position in 3D space or translate it along any axis.

Changes applied to the position in space of a dataset can be undone by clicking the Undo button in the Move panel (see Translating and Rotating Objects).
  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. Click the Advanced Properties button on the Image Properties panel.

    The Advanced Properties dialog appears.

  3. Enter the required coordinates in the Position in space box.
  4. Click the Apply button.
  5. Save the modified file, if required (see Exporting Objects).

If required, you can change the visual orientation of image data. regions of interest, and multi-ROIs. For example, in the case of TIFF files that do not appear as expected when opened.

Changes applied to the orientation of a dataset can be undone by clicking the Undo button in the Move panel (see Translating and Rotating Objects).
  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. Click the Advanced Properties button on the Image Properties panel.

    The Advanced Properties dialog appears.

  3. Enter the required directions for the X, Y, and Z axes in the Axis direction edit boxes.
  4. Click the Make Orthogonal button.
  5. Click the Apply button.
  6. Verify the result, and, if necessary, make any required modifications.
  7. Save the modified file, if required (see Exporting Objects).

The parameters available in the Advanced Properties dialog — position in space and dataset orientation — can be saved to a file that can be reloaded and then used to standardize other like datasets.