Parametric Mapping

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Parametric Mapping

If the pixel-wise modeling tool PXMOD has been licensed, PNEURO includes a parametric Mapping page. This integration has the advantage, that the VOIs generated by PNEURO can be used during the PXMOD model configuration, and that the resulting parametric maps can directly be regionally analyzed.

Parametric mapping is started after the PNEURO VOI outlining step as illustrated below. The model to be applied is selected from a subset of the PXMOD models in the green area which initially shows NONE. Please refer to the PXMOD Users Guide for a description of the procedure and the models.

Note: If a PVC method is enabled which generates corrected images, parametric mapping will be applied to the PVC corrected images.

MappingModelSelection

As a consequence of model selection, the Statistics action button is replaced by a Mapping button. When continuing with Mapping, a model-dependent configuration utility is show. The example below illustrates the case of mapping the binding potential with the BPnd (6 Calc methods) model.

MappingModelSetting

It requires two tissue time-activity curves for a preprocessing step, one representing a receptor-rich region, and one a receptor-less reference region. There are three options to specify them: FILE, VOI and TAC(DB). VOI is the obvious choice, as the PNEURO-generated VOIs can be employed. Either, a VOI is selected from the list, or the Merge VOIs option is enabled for creating a VOI from a VOI subset.

There are two ways of defining a VOI subset: (1) by the specification of a list of VOIs or a pattern such as Cer* (select all VOIs with a heading "Cer" in the name) in the text field, or (2) by selecting the merge button indicated above. With the latter, predefined (Left Grey Matter, Right Grey Matter, Grey Matter, Cerebellum) VOI lists can be generated. Selected shows a dialog window for defining any VOI combination.

The Mask by options serve for restricting the mapping procedure within the VOIs or the brain tissue segments. This might speed calculation significantly up.

Note: Mapping is performed in the selected result space and can take much longer in a highly-resolved MR space than in the PET space.

After confirming with Yes the program enters the Mapping page which hosts the PXMOD functionality. In the example below mapping start at the Model Preprocessing page, because there is no blood data involved. Note that the VOI definitions are already configured according to the TAC1/TAC2 definition in the dialog window.

MappingModelingPreprocessing

The remaining processing steps are described in the PXMOD documentation. Basically, the action buttons in the lower right have to be activated one by one. After parametric mapping completes, the results are shown in the Parametric Maps page.

ParametricMappingStatisticOption

The VOIs action button opens the VOI page with the resulting parameteric maps and the VOIs loaded.

The Statistics action button calculates the regional average of all VOIs in all parametric maps and shows the resulting table in the main Statistics page. Note also the last column which lists the VOI volumes for convenience.

MappingStatisticsResults

As an alternative, the currently selected parametric map can be sent to the Compare to Norm functionality with the Compare action button. This is valuable, if a normal database has been established against which the result can be compared. Note that in this case the selected result space of PNEURO has to be compliant with the space of the normal database.