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PXMOD Data Processing

Processing Overview

The processing of a data set in PXMOD consists of the following steps which are performed interactively:

Model selection

The first step of a pixel-wise processing is to select an adequate model from the model list. As a consequence, the user-interface elements are configured according to the model requirements.

Image data loading

As a next step the image data is defined and then loaded. During loading, image transformations such as smoothing may be applied.

Image masking

Optionally, a mask can be created interactively to restrict pixel-wise processing to the area of interest. Masking mainly serves for removing background pixels which might result in disturbing outliers. The created mask needs to be saved and is automatically added to the protocol definition. If a mask is applied, threshold-based masking within the model is disregarded.

VOI definition

Often, dedicated time-activity curves (TACs) are required for the preprocessing and/or the pixel-wise processing. In this case there is an optional step for outlining appropriate tissue VOIs interactively. The resulting VOI definitions or the related TACs need to be saved and are automatically added to the protocol definition.

Blood preprocessing

As a next step the tracer activity in arterial plasma (the input curve) is selected and loaded. It may require some corrections, for example to compensate for a delayed arrival and a dispersed shape at the site of activity measurement. For some models the whole-blood activity can also be supplied for blood spillover correction.

The result of blood preprocessing is shown on a separate pane. For all subsequent processing steps the corrected blood curve is used.

Note: Blood data is not required for reference models and some other models. In this case the blood-related panels are not active.

Model preprocessing

Depending on the model some preliminary calculations may be required, for example lookup tables or the derivation of initial parameters for the pixel-wise fits. These calculations are typically based on the TACs obtained in the VOI definition step. Usually the preprocessing results should be inspected to see that the model works properly with the prepared configuration. Therefore the results are shown on a separate panel.

Pixel-wise processing

Once the preprocessing was successful, the user can specify which of the parametric maps are to be calculated, and whether they should be restricted to a certain (physiological) value range. For the rapid processing during a prototyping phase, e.g. for determining the adequate table lookup range range, the pixel-wise calculations can be limited to the current slice.

Results explorations

The results may be explored in many different ways such as:

  • Comparison of the different maps in the included fusion tool.
  • Pixel-wise arithmetics among the maps in the included fusion tool.
  • Comparison of the pixel-wise outcome with results when analyzing the TACs interactively in the kinetic modeling tool (PKIN, optional tool).

Saving of the parametric maps

Each fitted model parameter results in a separate functional map. These quantitative images can be saved in any of the different formats available.

Saving of the protocol

PXMOD only uses explicit information for the calculation. Therefore, at the end of a processing, a protocol file can be saved which will allow to exactly reproduce the processing.

Working Mode using Initial Configuration

A suitable initial configuration can be used as an alternative to the step-wise processing outlined above. In this case all required data elements are specified beforehand with the Button Settings button from the taskbar, and then all processing steps executed with Button Locomotive. This, however, is only possible if all the elements such as the VOIs are already existing. Therefore it is better applicable for repeateing a processing with slightly changed parameters based on a protocol, rather than to the processing of a new data set.

How To Continue

There following sections describe the sequence of steps required for processing a data set.

In This Chapter

Model Selection

Image Data Loading

Image Masking

VOI Definition

Model Processing

Result Maps

Map Comparison

Interface to Kinetic Modeling (separate Option)

Using Protocol Files

Global Settings Modification

Batch Processing