Measurement Tools
NavNX provides measurement tools for taking precise anatomical measurements on both 2D slices and the 3D bone model. Measurements are calibrated using the pixel spacing data embedded in the DICOM files.Bone 3D View
On the Bone 3D view, measurements are placed via the right-click context menu.Length (Distance)
1
Right-click on the bone surface
Right-click where you want to start the measurement. A context menu appears.
2
Select Measure distance
Click Measure distance from the menu. The first point is placed at the click location.
3
Left-click for the second point
A prompt appears: “Click on bone surface to place point 2/2”. Left-click on the bone surface to complete the measurement. The distance is displayed in millimetres.
Angle
1
Right-click on the bone surface
Right-click where you want to start the measurement.
2
Select Measure angle
Click Measure angle from the context menu. The first point is placed.
3
Left-click for two more points
Click the vertex (centre point), then the third point. The angle is displayed at the vertex in degrees.
Camera Interaction
When you orbit, zoom, or pan the 3D view, the on-screen measurement markers (lines and labels) are automatically hidden. This is intentional — screen-space markers become misleading when the perspective changes. Your measurement data is not lost. It remains visible in the properties panel sidebar and is saved with the case.Erasing Measurements
Right-click near a measurement and select Erase nearest to remove it. Alternatively, use the Clear all button in the measurement overlay or the × button next to each measurement in the sidebar.2D Slice Views (Stack / MPR)
On 2D slice views, measurements are placed using the toolbar tools.Length Tool
1
Activate the tool
Click the Length button in the toolbar (ruler icon) or press L.
2
Place the first point
Click on the viewport to set the start point.
3
Place the second point
Click again to set the end point. The measurement is displayed immediately in millimetres.
Angle Tool
1
Activate the tool
Click the Angle button in the toolbar (protractor icon) or press A.
2
Place three points
Click to set the first point, then the vertex (centre), then the third point. The angle is displayed at the vertex.
2D Annotations (Stack / MPR Views)
In addition to length and angle measurements, the toolbar provides three annotation tools for marking up 2D slices:Arrow
Click and drag to draw an arrow. A text label can be added to describe the annotation (e.g. “Lateral condyle landmark”).Circle ROI
Click and drag to draw a circle region of interest. After drawing, a dialog prompts you to enter a custom text label for the annotation. The label is displayed on the circle in the viewport.Rectangle ROI
Click and drag to draw a rectangular region of interest. As with circles, a dialog prompts for a custom text label after drawing.For both Circle and Rectangle annotations, statistics (area, mean density, standard deviation) are hidden by default to keep the view clean. Use the Show Metadata toggle in the properties panel to reveal them (see below).
Properties Panel Options
When a 2D annotation tool is active, the properties panel (right sidebar) shows additional controls:Annotated Slices
A collapsible Annotated Slices section in the properties panel lists every slice that contains at least one annotation. Each entry shows:- The slice number
- Colour-coded pills indicating annotation types present on that slice
Annotations
Each measurement can be annotated with a label (e.g. “PCL entry to plateau”):- In the sidebar, type in the label field below each measurement
- On the 3D overlay, click the ✎ icon next to a measurement
Persistence
All measurements and 2D annotations are saved as part of the case plan. They persist across:- Switching between view modes (e.g. Stack to MPR to Bone and back)
- Closing and reopening the case (annotations are saved with the plan and restored on reload)
- Camera changes on the 3D view (data preserved, markers refresh)
Measurements and 2D annotations are included in the pre-op report when you print or export it. The report shows a summary table with tool type, computed values, and slice location.