Cortical Thickness Mapping Visualisation

This page is used to visualise the results of the estimation of bone cortical thickness from CT data. This visualisation is automatically selected when the 'thickness' task page is selected.

In the middle of the visualisation controls are some text messages that show whether the current estimate was successful, what the various results are and what the average (least mean square) error was between the modelled and measured CT values along the displayed line, in HU.

At the top, there is a dropdown list for determining what is mapped to the surface, i.e. thickness, mass, density (CT value), FWHM blur (image resolution), endocortical thickness, trabecular density, joint space or soft tissue. These various properties may or may not be available, depending on what technique was used to measure the cortex. If the particular value is not available, then the surface will be shown entirely coloured gray.

After this, there is another dropdown list which selects the colour map to be used to display this data. Various colour maps are available: the best choice will depend on the specific application.

The following four sliders control the range of values used for the colour scales when mapping these values. After this, the smoothing slider can be used to smooth any of these estimates over the surfaces. The 'fill missing data' slider controls to what extent this smoothing should be used to replace missing values as well.

The 'reject outliers' slider controls the outlier rejection used when smoothing the surface on creation of a cortical or joint space surface. This is the maximum acceptable angle between the normal used to make the measurement, and the normal of any neighbouring triangle in the created surface.

The bottom three checkboxes control what is displayed in the visualisation window below the image and 3D windows. This contains a graph of CT values in HU against distance along the currently defined line in mm. The graph can display the 'original data' (in blue), which are just the CT values along the line through the data. It can also display the 'optimised blurred model' (in red), which is what the optimisation process attempts to match as closely as possible with the original data. The 'deconvolved model' (also in red) is the unblurred CT value distribution from which the optimised blurred model is created, and it is this which gives the cortical properties. The default is to display all three graphs.

The range of CT values (in HU) on the vertical axis is the same as the range of CT values that can actually be seen in the CT image data. Hence to change this range, use the rotate tool to change the windowing parameters in the top left image window, and the graph will also be updated dynamically.

When cortical thickness is mapped over an entire surface, the results are updated dynamically as the calculation progresses, but at not more than 5 updates per second. It is likely that the actual calculation will proceed at a much faster rate than this.