Interactive 3D Rotation
Rotating and spinning
Any of the 3D views – volume view, MIP, MPR or cut-plane – may be rotated and/or spun using either the mouse, the thumbwheel controls in the border of the window, or the arrow keys on the keyboard.
Using the mouse
To rotate and/or spin the 3D view click and drag on the image with the LEFT mouse button. The image will rotate about its centre in the direction of your movement. Releasing the button stops the rotation and the image remains in that new orientation. Alternatively, if inertial spin is enabled (Edit / Options from the menu) and you release the mouse button before you have stopped dragging, the image will continue to spin with a speed proportional to the speed you moved the mouse. To stop the image from spinning either click and hold the LEFT mouse button briefly on the image until the spin has stopped, or click the Reset button on the toolbar.
Using the arrow keys
The arrow keys on the keyboard can be used to rotate the 3D view in the horizontal and vertical axes. Pressing an arrow key rotates the 3D view by approx 3 degrees. Holding down the arrow key produces a continuous series of steps. If a smaller step size is required, holding down the shift key while pressing the arrow key reduces step size by approx 10 times.
Using the thumbwheels around the border of the 3D window
The 3D view includes four thumbwheel controls. The bottom thumbwheel zooms the 3D view in or out as an alternative to the mouse-driven method. The remaining thumbwheels labeled X, Y and Z each control rotation about the corresponding axis. No inertial spin is imparted using the X, Y or Z thumbwheels.
Using the quick-alignment buttons
The 3D view also includes four pairs of buttons adjacent to the thumbwheels, used to effect the 3D view in a pre-defined manner. The buttons labeled 1 and 2 to the left of the zoom thumbwheel restore the original/default zoom level and the previous zoom level. Clicking button 1 will zoom back to the default position, and then clicking button 2 will restore the zoom level to its previous value.
The two buttons alongside the X, Y and Z thumbwheels activate preset rotations through +/- 180 degrees relative to the default position. The L and R buttons rotate the image to left and right, the T and B buttons to top and bottom, and the F and B buttons to front and back. The animation sequence used in these rotations may be disabled and/or adjusted via Edit / Options from the toolbar.
The following screenshot shows the location of the thumbwheels and the quick-alignment buttons:
Volume View
3D volume view
The 3D volume view is the default view that appears in the 3D window when Disect Pro imports a new data set. Its image is a reconstruction made by stacking the original tomographic slices in three dimensions and interpolating over the inter-slice gaps. Disect Pro computes that reconstruction entirely within the graphics processor to take advantage of the high speed and memory capacity of today’s technology.
To select volume view click the VOL button on the toolbar or select the volume view option from the View Menu. The whole image can be rotated into any orientation using the mouse, thumbwheel controls or keyboard arrow keys, and by adjusting the window level and width detail embedded within the volume can be progressively revealed.
An example of the volume view is shown below:
Maximum Intensity Projection (MIP)
What is MIP?
Maximum Intensity Projection (MIP) is a volumetric imaging technique in which the scanned object is rendered semi-transparent. In effect the resulting image is a 3D X-ray in which the voxels that represent the greatest density (e.g., for bone structures) appear brightest (hence maximum intensity). This visualisation method is ideal for viewing high-contrast data, and where it is important to easily see internal structure.
To select this view click MIP on the toolbar or select Maximum Intensity Projection from the View Menu.
The screenshot below shows an example MIP view:
Multi-Planar Reconstruction (MPR)
What is MPR?
Multi-Planar Reconstruction (MPR) was one of the first visualisation techniques widely used for viewing 3D medical images. It employs multiple 2D planes that are positioned and oriented in a 3D data set so that the projection of the data on each plane may be simultaneously viewed.
In Disect Pro the MPR view uses three orthogonal 2D planes, each corresponding to the images in the three 2D windows. Any of the planes can be moved along its axis and the whole image can be rotated into any orientation using the mouse, thumbwheel controls or keyboard arrow keys.
To select this view click MPR on the toolbar or select Multi-Planar Reconstruction from the View Menu.
To move any of the planes begin by selecting roam or scroll in the control panel, or by right clicking on the MPR image. Then with the middle button click on the desired plane and drag the mouse either up and down, or left and right, or forward and back, depending on the orientation of the plane being moved. While the plane is being moved the corresponding 2D view is automatically updated.
Note also that scrolling or roaming though the slices in any of the 2D views is automatically tracked by the position of the planes in the MPR view.
An example of MPR view is shown below. In this screenshot, one of the planes (outlined in red because it is active) is being moved using the mouse.
Orthogonal Cut Planes
What are cut planes?
A cut plane is in effect a flat 2D viewing surface that can be moved through a 3D data set to produce a 2D image at that location. That has the effect of removing from view the part of the 3D object that has been moved through. Disect Pro has six orthogonal cut-planes which can be moved using the middle button of the mouse to ‘cut into’ a 3D volume view of the scanned object, revealing internal detail.
Selecting and using cut planes
To select this view click the CUT button on the toolbar or select cut planes from the View Menu. The relevant section of the control panel will automatically expand to show the following options:
The default setting has all cut planes and ‘rotate all’ selected. In this mode left clicking on the 3D image and dragging will rotate the image and all cut planes as one object. Consequently the cut planes remain aligned with the X, Y and Z axes of the scanned subject.
To move the cut planes to an oblique angle relative to the scanned subject select ‘rotate cut’ in the control panel. Now when you left click on the 3D image and drag, only the cut planes rotate, the scanned subject remains stationary.
Individual cut planes can be activated or disabled using the tick boxes (see the diagram opposite).
To return all cut planes to their default positions and orientation, click the “Reset all” button.
The screenshot below shows the cut plane view with one of the cut planes being moved using the mouse. The blue lines indicate the border of the cut planes, and the red border lines highlight the cut plane that has been selected and is being moved into the scanned subject. The desired cut plane is selected by clicking and holding down the middle mouse button over the cut plane, at which point the border lines change from blue to red. Dragging the mouse while holding down the middle button then moves the cut plane.
Turning off the coloured border lines
The blue border lines can be removed from view by left clicking the ‘blue cube’ icon on the toolbar:
Even when the blue border lines are invisible the cut planes themselves are still active. Selecting any of the cut planes with the middle mouse button (see above) will bring back into view the border lines for that cut plane, now shown in red since the cut plane is active. The scanned object can then be cut into as normal. Removing the blue border lines from view does not disable any of the cutting features. The blue border lines can be restored by clicking again on the the ‘blue cube’ icon on the toolbar. That icon has a toggle action.
Removing the blue border lines can be advantageous when exporting the 3D image to a 3rd party document as that avoids any aspect of the image being obscured.