MR or CT Reference Image Loading

The layout of the second page depends on the Mask setting on the PET page. The situation illustrated below represents the selection of MR-based masking. The page is titled MR, and in the lower right the Mask options appear with a corresponding action button Mask by MR. The situation with CT-based masking is analogous.

With PET-based masking the page is labeled CT | MR, the image loading button Load Anatomical, and the action button Mask by PET.

Reference Image Loading

Please use the indicated button for loading an anatomical image series which is matched in space and resolution to the PET series. Appropriate images can easily be created using PMOD’s image fusion tool. Note that the loaded images are automatically cropped by the same box as the PET. The correspondence can be verified with the fusion slider.

MR-based Body Mask Definition

In the case of an MR-based mask selection the corresponding Mask options are available in the lower right:

• Otsu: This method iteratively looks for the best threshold to separate an object from a background assuming two main gray-level regions.
• Mean: Includes all pixels above the image mean.
• % max Value: Includes all pixels above the specified percentage of the image maximum.
• Threshold Value: Includes all pixels above the specified absolute value.
• Automatic: This procedure calculates the image log-values and derives a threshold from the histogram.

CT-based Body Mask Definition

In the case of a CT-based mask selection the corresponding Mask options are available in the lower right:

• Otsu: This method iteratively looks for the best threshold to separate an object from a background assuming two main gray-level regions.
• Mean: Includes all pixels above the image mean.
• % max Value: Includes all pixels above the specified percentage of the image maximum.
• Threshold Value: Includes all pixels above the specified absolute value.
• Automatic: This method applies a threshold, followed by morphological operations for removal of the bed, closing of the nostrils and filling of the lungs.

In addition to the procedure selected above, morphological opening/closing operations will be applied to remove isolated pixels and fill holes.

Please proceed with mask creation by activating the action button in the lower right.