Performing perfusion / VAI analysis

Once tumor mask is deemed correct, the mask should be registered as the active mask by pressing the <Register> button on the Lesion segmentation menu:

This step will save the mask for further analysis and also reformat the mask to the perfusion data space.

The registered lesion mask can be toggled to be visible/invisible (including visible in the perfusion series) by pressing the <Show/Hide lesion mask > button the <Overlay> tab or by pressing <Ctrl+M >

Once a valid lesion mask has been registered and perfusion analysis has been performed, perfusion metrics from selected parametric maps can be analysed for voxels contained in selected lesion mask.  Perfusion analysis is initiated via the <Perfusion analysis> tab:

Figure 1: Perfusion analysis menu options.

Here you specify which perfusion/VAI maps should be generated and perfusion specific options. Description of the various options and output map types are covered in VAI-specific perfusion maps and Theoretical background - Vessel Architectural Imaging . Note that, if a VOI mask has been defined, then perfusion analysis can be limited to be performed in the selected VOI. This is generally not advisable since certain processing steps such as leakage correction requires information from the entire image volume.

When whole image volume is included in analysis, background voxels will be excluded from the analysis – the threshold for voxels to exclude can be visualized and modified by checking ‘show noise level’ and modify level using the slider.  Image stats can still be extracted from only the lesion VOI once the perfusion maps have been generated.

Pressing will initiate the perfusion analysis and once completed the generated output maps will be visible in the ‘parametric maps’ panel below the source dataset panel:

Figure 2: Addition of output parametric maps after completed VAI analysis.

Saving parametric maps: This needs to be done via the main nordicICE interface. All maps visible in the parametric maps list are also available in the main nordicICE workspace and can be viewed by reducing/minimizing the size of the VAI module GUI. The parametric maps can then be saved via the standard nordicICE image save options.

Generated parametric maps can be removed from the list by right-clicking the thumbnail and selecting <Close>. This will also close the corresponding parametric maps from the main nordicICE workspace (without saving the data).

The output parametric maps can now be visualized as overlays on the structural /functional data and statistics can be extracted .