Digital Reference Object Extension
Updated: 14 August 2014

DROe Description


The PET/CT Digital Reference Object Extension (DROe) is a set of synthetically generated DICOM image files of known voxel values for positron emission tomography (PET) and x-ray computed tomography (CT). The PET/CT DROe is intended to test three specific features of medical image viewing software:

SUV-peak computation: The DROe contains two 'blobs' of known voxel values that allow testing of SUV-peak calculations.

PET/CT Fusion Alignment: The DROe contains multiple test objects within the PET and CT DICOM volumes that are designed to test the PET/CT fusion alignment in the axial, sagittal, and coronal views.

ROI Fidelity: When an ROI is drawn around a lesion, it is not always clear which voxels are included in the ROI or how those voxels are used to compute ROI metrics. The DROe has test objects designed to help determine which voxels are included within an ROI drawn on the screen and intuit how those voxels are used in ROI computations.

The PET/CT DROe was developed at the University of Washington Imaging Research Laboratory and is supported by the Quantitative Imaging Biomarker Alliance (QIBA).



The PET and CT components of the Images of the DRO are each a set of DICOM format files, one file per image slice. Each set of files are typically grouped as a stack to form an image volume. Representative sections through the CT and PET image volumes are shown below. The synthetic test object is based on the body of the NEMA NU-2 PET test phantom [J Nucl Med, vol. 43 no. 10 1398-1409, 2002] with similar contrast levels, but with different internal structures.

DROe DROe DROe
Representative axial views through the DROe image volumes.
Left: PET/CT Fusion alignment test patterns
Center: SUV-peak calculation test objects
Right: ROI Fidelity test object


Users of the DROe are asked to download the package, import the PET and CT objects into their viewing software, perform the tests, and submit the results back to this website.