Volume 3D

 

The 3D volume rendering plug-in module generates 3D volumes from 2D data sets and displaying them as direct volume rendered (DVR) images, MIP images, Raysum average projections and planar reconstructions using oblique angles. The tools include volume rotation and plane adjustment controls, cross referencing tools, linear and volume measurements, slab thickness controls, pseudo coloring, transfer function editor, dynamic resolution reduction, and dynamic ray under sampling. The plug-in applies to studies whose largest, contiguous segment of images share complementary spatial resolution characteristics, meaning they were acquired on a single machine as part of a single procedure.

 

The 3D volume rendering plug-in module has the following workstation requirements:

Attempts to use the 3D volume rendering plug-in module on a machine with insufficient resources may display one or more warnings or error messages. If this occurs, the plug-in may appear to process the data correctly but performance may be poor and results cannot be guaranteed.

 

When the viewer starts, it searches the server for the volume rendering plug-in license, 3dvol.plx. If a valid license exists and the user account is configured to use the plug-in module, the viewer prompts the user to download and install it on the workstation. Once downloaded the plug-in installs automatically and is ready to use.

 

To use the volume rendering plug-in module:

  1. Drop a series from the thumbnail panel into an image frame

  2. From the Extensions menu expand the Volume 3D submenu

  3. Select the rendering mode:

    1. 3D DVR

    2. 3D MIP

    3. 2D Axial, Coronal or Sagittal

If the data hasn’t downloaded to the workstation completely, a progress bar appears indicating the download status. When the data is completely loaded, the image frame becomes a plug-in frame with toolbar displayed on the border and the default layout appears.

 

Volume Frame Layout

 

The volume rendering plug-in consists of a viewing area and a toolbar.

 

 

 

 

Volume Rendering Frame

 

The 3D volume rendering plug-in frame consists of the areas described below:

 

Area Description

Image Area

Main area in the middle of the frame displaying the volume

Toolbar

Plug-in tools to easily adjust the orientation, projection mode, reconstruction type and other features and controls

Orientation Indicator

A wire-frame cube in the lower left corner showing the orientation of the volume displayed in the image area

Reconstruction Mode

Applied reconstruction mode displayed in the upper right corner

Pixel Value

Pixel value of the displayed pixel at the cursor’s focus point

 

Volume Rendering Toolbar

 

The toolbar defaults to the right side of the image frame. It can be detached and floated anywhere in the image frame.

 

Icon

Tool

Description

Axial alignment Display the transfer function editor panel.

Coronal alignment Define a region of interest in which you advance through the volume without affecting the image outside the region.

Sagittal alignment Measure the distance between two points in the volume.

Direct volume rendering Display the image as a fully rendered volume using the applied transfer functions.

Maximum intensity projection Display the image as a maximum intensity projection

Raysum average projection Display the image as a Raysum projection

Full reconstruction Reconstruct the data as a three dimensional volume

Thick slab reconstruction Reconstruct the data using the defined slab thickness

Planar reconstruction Reconstruct the data as a two dimensional planar image

Transfer function editor Display the transfer function editor panel

Spyglass Define a region of interest in which you advance through the volume without affecting the image outside the region

Linear measurement Measure the distance between two points in the volume

Modality value Define a sphere on the volume and report the area, mean pixel value and the standard distribution

Export image Create a screen shot of the current view and add it to the thumbnail panel

Export series Create a series of images centered around the current view and add it to the thumbnail panel

Show localizers Display and hide localizer lines indicating the plane of the displayed image on other volumes

 

 

Image Display Features

 

The 3D volume rendering plug-in module supports multiple projection modes, reconstruction modes, and pseudo color schemes.

 

Display Orientation

 

The first three icons in the toolbar adjust the perspective of the current view in the orientation cube displayed in the lower left corner of the frame.

 

Icon

Mode

Context Menu

Hot Key Description

Axial Alignment Axial A Display the volume in axial orientation

Coronal Alignment Coronal C Displays the volume in coronal orientation

Sagittal Alignment Sagittal S Displays the volume in sagittal orientation

 

Projection Modes

 

The 3D volume rendering plug-in module supports three projections modes: direct volume rendering, maximum intensity projection and Raysum average projection.

 

Icon Mode Context Menu Hot Key Description

Direct Volume Rendering DVR D Displays the image as a fully rendered volume using the applied transfer functions

Maximum Intensity Projection MIP M Displays the image as a maximum intensity projection

Raysum Average Projection AVG V Displays the image as a Raysum projection

 

Reconstruction Modes

 

The 3D volume rendering plug-in module supports three reconstruction modes: full reconstruction, thick slab reconstruction and planar reconstruction.

 

Icon Mode Context Menu Hot Key Description

Full reconstruction Full F Reconstruct the data as a three dimensional volume.

Thick slab reconstruction Thick T Reconstruct the data using the defined slab thickness

Planar reconstruction Planar P Reconstruct the data as a two dimensional planar image

 

The applied reconstruction mode is displayed in the upper, right corner of the image frame. When using thick slab mode, the applied slab thickness is displayed as well.

Slab thickness is adjustable using the mouse and keyboard.

 

Pseudo-Color Schemes

 

A number of predefined pseudo-color schemes can be applied to MIP and Raysum projection images. The default scheme is greyscale (white on black) and can be changed by the user. The other options include black on white greyscale, red, blue, red glow, blue glow, hot metal, ice water, and rainbow.

 

To change the applied color scheme:

  1. Position the mouse over the plug-in frame and click the right mouse button

  2. Click Pseudo-Coloring to display the submenu

  3. Select the color scheme from the submenu

To change the default color scheme:

  1. Position the mouse over the plug-in frame and click the right mouse button.

  2. Click Pseudo-Coloring to display the submenu.

  3. Click Save Current as Default.

When a color scheme is applied to the volume, use the window/level tool to adjust the palette range. You can also define the default color scheme from the configuration panel.

 

 

Image Manipulation

 

Image manipulation tools include rotation, panning, scrolling, zooming, windowing/leveling and color palette adjustments.

 

Window/Level

 

To adjust the window and level settings for the displayed image:

  1.  Press and hold down the right mouse button
    1. Drag the mouse to the left or right to increase or decrease window width
    2. Drag the mouse back and forth to increase or decrease the window center

Scrolling

 

Scrolling is available in slab and planar reconstruction modes.

 

There are two ways to scroll through the image stack:

Precasting

 

Precasting is the ability to hide the outer planes of a volume to reveal the structure behind it. Change the precaste depth to advance further into the reconstructed volume. Precasting is available in full reconstruction mode only.

 

To change the precaste distance:

  1. Position the mouse cursor over the image in the frame

  2. Press and hold down the middle mouse button

  3. Drag the mouse away forward or backward to increase or decrease the precaste distance (from the outer edge of the reconstructed volume)

The precaste distance is displayed along the bottom edge of the image frame.

 

Zooming

 

To magnify the images:

  1. Press and hold down both the left and right mouse buttons
  2. Drag the mouse forward or backward to increase or decrease the image size

Panning

 

To reposition the volume in the image frame, press and hold down the left mouse button and drag the mouse.

Rotating

Slab Thickness

 

When using thick slab reconstruction mode, you can adjust the slab thickness dynamically or by using some preset slab thicknesses.

To apply a custom slab thickness:

  1. Press and hold down the Shift key and the middle mouse button at the same time

  2. Drag the mouse away forward and backward to increase or decrease the thickness

Preset slab thicknesses are assigned to the following keys:  

Keyboard Key Applied Slab Thickness
1 1mm
2 2mm
3 3mm
4 4mm
5 5mm
6 6mm
7 7mm

 

The applied slab thickness is displayed in the upper, right corner of the image frame.

 

Spyglass Tool

 

The spyglass tool defines a region of interest through which you can precaste through a reconstructed volume. Spyglass is enabled when using a directly rendered volume in full reconstruction mode. The tool is available on the volume rendering toolbar.

Define a spyglass ROI as follows:

  1. Set the projection mode to Direct Rendered Volume

  2. Set the reconstruction mode to Full Reconstruction

  3. Define the spyglass ROI using either of the following methods:

    1. Using the Spyglass tool :

      1. Select the Spyglass tool on the volume rendering toolbar

      2.  Position the mouse where the top left corner of your region of interest

      3. Press the left mouse button and drag the mouse to define the ROI frame

    2. Using Ctrl and right mouse button:

      1. Position the mouse where the top left corner of your region of interest

      2. Press the left mouse button and drag the mouse to define the ROI frame

  4. Reposition the ROI frame by placing the mouse cursor in the center of the ROI frame, pressing the left mouse button and dragging the mouse

Note: If the starting position of the mouse cursor is inside the spyglass ROI frame, only the data inside the ROI is precaste. The precaste distance within the ROI is displayed along the bottom edge of the spyglass ROI frame. If you start precasting outside the spyglass ROI, only the data outside the ROI is precaste. The ROI frame remains displayed and repositionable until you select an alternative projection mode or right-click on the ROI border.

 

Transfer Functions

 

The transfer function editor defines the pixel range for selected opacity levels in the volume rendered image.

 

To configure the transfer functions:

  1. Select the transfer function editor tool to display the transfer function editor

  2. Check the box in the Material column for each transfer function applied to the rendered volume

    1. Selected transfer functions are applied immediately

  3. Close the transfer function editor when done

 The transfer function editor panel displays the following information and tools:

Section Field Description
Presets Material Settings label
  Range min. Minimum pixel range
  Range max. Maximum pixel range
  Add Add a new transfer function preset
  Remove Remove an existing transfer function preset
Pixel Range Mod Pixel value at which the red, green, blue and opacity settings start applying
  Red Red value for display
  Green Green value for display
  Blue Blue value for display
  Opacity Opacity for display
  Add Add a new transition point in the pixel range
  Remove Remove an existing transition point in the pixel range

 

To define a new transfer function preset:

  1. Click the Add button

  2. Enter a label

  3. Click Accept for the entry to appear in the preset list

  4. Select the new preset from the list

  5. Click the Add button in pixel range section

  6. Enter the pixel value, the red, green, blue and opacity for this transfer function

  7. Click Accept

To save a defined transfer function preset as the default:

  1. Configure the transfer function

  2. Right click on the image to display context menu

  3. Select DVR Transfer Function to display sub-menu

  4. Click Save Current as Default

To restore the currently applied transfer function settings to the saved default, click Restore Factory Defaults

 

Cross Correlation

 

Cross correlation is the ability to identify the same point in all orthogonal images and volumes. Cross correlation information is enhanced by displaying localizer lines on the image volumes. The 3D volume rendering plug-in module cross correlates 3D volumes and 2D series using the Magic X tool.

 

Magic X

 

Cross correlation is the ability to identify the same point in all orthogonal images and volumes. When active, the point under the mouse cursor is indicated in each frame with a Magic X graphic.

 

Note: Magic X requires images and volumes share the same frame of reference as defined by the imaging modality or an externally generated spatial resolution object. If this information does not exist, there is no spatial relationship between the images and Magic X will find no cross correlation points.

 

Magic X exists as two modes:

To use Magic X dynamically:

  1. Position the cursor over the point in a volume
  2. Press and hold down the Ctrl key
  3. Click the left mouse button to display the intersecting point in all volume frames

If you drag the mouse, the position updates in all volume frames.

 

To activate Magic X mode:

  1. Click the Magic X cursor icon in the Toolbox group
  2. Position the cursor over the point in a volume
  3. Click the left mouse button to display the intersecting point in all image frames
  4. Hold down the left mouse button and drag the mouse to dynamically refresh the point under the cursor in each of the other cells.

While the left mouse button is pressed, a Magic X graphic, appears at the correlating position in each image.

 

Localizer Lines

 

Orthogonal images in volume frames can include localizer lines showing the interesting image planes. To show and hide the localizer lines select the Show/Hide Localizer Lines icon in the volume rendering toolbar.

 

Annotations

 

The volume rendering plug-in module supports annotation tools that include linear and volume measurements.

 

Linear Measurements

 

The linear measurement tools measures distances across three dimensional spaces that can be temporary or defined as annotations and placed on images.

A measurement ruler is drawn in three dimensional space on a two dimensional image.  Linear measurement annotations are not saved when exporting reconstructed images. Two dimensional measurement annotations can be applied using the main viewer tools after the image is exported.

 

To create a temporary linear measurement:

  1. Position the cursor where the measurement will begin
  2. Press and hold down both the Shift key and the right mouse button
  3. Drag the mouse between two points on an image
    1. Distance appears alongside the drawn line
  4. Release the mouse button to erase the ruler and value

Use the image manipulation tools, such as rotate, to get the entire object you want to measure displayed on the image and create the measurement. As the image is rotated, the ruler will remain the same length and in the same position in the anatomical structure, but might appear different on the screen.

To annotate an image with a ruler and distance value:

  1. Press the linear measurement button

  2. Position the cursor where the measurement will begin

  3. Press and hold down the left mouse button

  4. Drag the mouse to the ending position

    1. Ruler and distance appears

 

Further instructions for a ruler and distance values:

 

Note: Measurements that are drawn cannot be modified. You must delete the existing annotation and draw a new one.

 

 

Volume Measurements

 

The volume measurement tools calculate the area in a sphere defined in three dimensional space and the average pixel value in the sphere along with the distribution’s standard deviation.

The volume annotation is drawn in two dimensional space as a circle but exists in the object as a sphere. Use the image manipulation tools, such as rotate, to get the center of the object you want to measure displayed on the image and create the measurement. As you scroll through the image, the displayed areas change representing the outer edges of the sphere, but the sphere remains in its original position and reported the total values regardless of which portion is displayed on the image.

 

To create a spherical annotation and calculate its volume, average pixel value and standard deviation:

  1. Press the modality value button n the volume rendering toolbar
  2. Position the cursor at the center of the sphere you want to define
  3. Press and hold down the left mouse button
  4. Drag the mouse to define the sphere

Further instructions for spherical annotations:

  1. Repeat steps 2-4 to measure another volume

  2. Right click on on the circle and select Delete selected from the menu to remove a volume annotation

  3. Click the modality value button in the toolbar to return to normal cursor mode

Volume measurement annotations are not saved when exporting reconstructed images. Two dimensional measurement annotations can be applied using the main viewer annotation tools after the image is exported.

 

Note: Spheres cannot be modified. You must delete the existing annotation and draw a new one.

 

Saving Images

 

Images created by the volume rendering module can be exported to the main viewer and sent to the archive for storage. Exported images can be attached to reports as key images as well.

Annotations applied to a volume image are removed when the image is converted from a three dimensional object to a two dimensional image.

 

Exporting an Image

 

To export a single volume image:

  1. Double click the volume rendering plug-in frame containing the image:

    1. Gives the option to terminate the volume rendering plug-in frame and load the exported image into a normal viewer frame.

  2. Select the volume rendering plug-in frame containing the image to export

  3. Click the Export Image button, , on the volume rendering toolbar.

The exported image is added to the series of exported volume rendered objects in the thumbnail panel. If this is the first exported image, a new series appears in the thumbnail panel.

 

Exporting a Series

 

To export a series of volume images:

  1. Select the volume rendering frame containing the images to export

  2. Click the Export Series button.

  3. Select the number of slices to export n the Export Options pop-up

  4. Select the slice spacing

  5. Press the Auto/Full button

  6. Click OK

By default, the exported series contain the displayed image and images projecting outward at intervals defined by the slice spacing. By selecting the Auto/Full button the volume will contain the displayed image, the first and last (outermost) image in the volume as defined by the number of slices. The exported series appears as a new series in the thumbnail panel.

 

Configuration

 

The volume rendering plug-in module configuration panel is available from the Volume 3D item in the Extensions menu. Select Configure to pop up the configuration window.

 

 

The configurable volume rendering plug-in module settings are defined in the table below:

 

Section Setting Default Description
General Maximum buffer resolution 4096 Defines the maximum number of rays cast
  Dynamic resolution reduction Disabled Reduce the screen space while the object is in motion. This will boost performance but degrade image quality.
  Dynamic ray undersampling Disabled When the object is in motion, increase the distance between sampling points. This will boost performance but degrade image quality.
  Default thickness 24mm Default slab thickness
  Default color White on black Default pseudo color applied to MIP and Raysum projection images.

 

 

Keyboard Control Summary

 

The following tables summarize the keyboard and mouse commands.

 

Mouse Controls

 

The table below defines the mouse control when the feature is supported by the applied mode(s).

 

Key Mouse Action Result
  Left Drag Repostion the image in the frame

Shift

Left Drag Rotate the image
Ctrl Left Drag

Cross correlate cursor point on all images

  Right Drag left/right

Change the window width

  Right Drag forward/backward

Change the window center

Shift Right Drag

Temporary linear measurement

Ctrl Right Drag

Define spyglass ROI frame

  Left+Right Drag

Resize image

  Middle Drag Precaste/Scroll through volume
  Middle Scroll

Scroll through images

Shift Middle Drag

Change slab thickness

 

Note: Some functions are unavailable in specific projection and reconstruction modes, resulting in mouse control being unavailable.

 

Keyboard Shortcuts

 

Functional Group Key Action
Planes A Display volume in axial plane
  S Display volume in sagittal plane
  C Display volume in coronal plane
Projection Modes D Direct volume rendering mode
  M Raysum average projection mode
  V Full reconstruction mode
Reconstruction Modes F

Full reconstruction mode

  T

Thick slab reconstruction mode

  P Planar reconstruction mode
Slab Thickness 1 Apply 1mm thick slab
  2 Apply 2mm thick slab
  3 Apply 3mm thick slab
  4 Apply 4mm thick slab
  5 Apply 5mm thick slab
  6 Apply 6mm thick slab
  7 Apply 7mm thick slab
Animation I Rotate volume 360-degrees