Data requirements

This page lists the data requirements for the Flywheel viewer to operate as expected.

DICOM requirements

Introduction

The Flywheel Hierarchy closely matches the DICOM Model of the Real World , but with slightly different nomenclature.

• Patient becomes Subject in Flywheel
• Study becomes Session in Flywheel
• Series (roughly) becomes Acquisition in Flywheel

Depending on how DICOM data is imported into Flywheel, the mapping between DICOM tags and Flywheel hierarchy fields might differ. Please check the following pages for more information:

• Bulk import.
• CLI.
• DICOM connector.

Assumptions

DICOM UIDs uniqueness

The V2 viewer relies on DICOM data to be indexed in the Flywheel's DICOM Web service. Since that DICOM Web service enforces the DICOM hierarchy, it means that there cannot be two DICOM files with the same SeriesInstanceUID or StudyInstanceUID within the same Flywheel project. If that's the case, the V2 Viewer will not open one of the files with a duplicate UID. See also Viewer indexing errors.

The V3 viewer relies on a different data service that does not have the constraints of the DICOM hierarchy, therefore there is no requirements about DICOM UIDS uniqueness for the V3 viewer.

Zip files

DICOM files sharing the same SeriesInstanceUID are expected to be zipped in a single zip archive and that zip archive must only contain DICOM files belonging to the same SeriesInstanceUID.

V2 Viewer

The V2 viewer requires the following tags:

V3 viewer

DICOM tags required for all images to open in the viewer

Note: Only standard SOPClassUIDs are supported. See the list of SOPClassUIDs currently supported by the viewer here.

DICOM tags required to render images in advanced layouts (MPR and 3D rendering)

All data

• Series must have more than 1 image.
• Series should not be a 4D dataset.
• All images should have Pixel Spacing (0028,0030) (some exceptions for multi-frame data, see below).

Single-frame data

• Rows (0028,0010) and Columns (0028,0011) must be the same for all instances.
• SamplePerPixel (0028,0002) must match across all instances.
• All instances must have ImageOrientationPatient (0020,0037) values within a small tolerance in vector directions, default is 0.01.
• ImagePositionPatient (0020,0032) should exist in all instances.
• The spacing between consecutive frames, as determined by the ImagePositionPatient value for each frame, should be equal to the average spacing between frames with a 0.2mm tolerance.
• If slice spacing is approximately an integer multiple of the average spacing (e.g., 2×, 3×), it is assumed that frames are missing. The dataset is still reconstructible and the missing frames are tracked.

Multi-frame data

• Pixel measurement information is required from any one of these tags:

  • PerFrameFunctionalGroupsSequence.[0].PixelMeasuresSequence(0028,9110)
  • SharedFunctionalGroupsSequence.PixelMeasuresSequence(0028,9110)
  • PixelSpacing(0028 0030) either with SliceThickness(0018,0050) or SpacingBetweenFrames(0018,0088)

• Orientation information is required from any one of these tags:

  • SharedFunctionalGroupsSequence.PlaneOrientationSequence(0020,9116)
  • PerFrameFunctionalGroupsSequence.PlaneOrientationSequence(0020,9116)
  • ImageOrientationPatient(0020,0037)
  • DetectorInformationSequence.[0].ImageOrientationPatient(0020,0037)

• Position information is required from any one of these tags:

  • PlanePositionSequence(0020,9113)
  • CTPositionSequence(0018,9326)
  • ImagePositionPatient(0020,0032)
  • DetectorInformationSequence.[0].ImagePositionPatient(0020,0032)

NM modality

• ImageType.[2] (0008,0008) should be either RECON TOMO or RECON GATED TOMO

DICOM tags required for segmentation overlay

Segmentation files (DICOM SEG and DICOM RTSTRUCT) cannot be loaded in the viewer without a reference image series. The reference image series for a segmentation file is defined as an image series that has SOPInstanceUIDs that match the ReferencedSOPInstanceUIDs from the ReferencedSeriesSequence of the segmentation file.

When loading a segmentation file into a viewport, the viewer will return an error message if no reference image series is found in the left-side panel.

Additionally segmentation files require specific tags/sequences:

DICOM SEG files

• FrameOfReferenceUID (0020,0052)

• sequences:

  • ReferencedSeriesSequence (0008,1115)
  • SharedFunctionalGroupsSequence (5200,9229)
  • PerFrameFunctionalGroupsSequence (5200,9230)

DICOM RTSTRUCT files

• FrameOfReferenceUID (0020,0052)

• sequences:

  • ROIContourSequence(3006,0039)
  • StructureSetROISequence(3006,0020)
  • ReferencedFrameOfReferenceSequence(3006,0010)

DICOM tags required for measurements

All modalities

• Pixel Spacing (0028,0030)

Ultrasound data

• SequenceOfUltrasoundRegions(0018,6011)

DICOM tags required for PET data conversion to SUV units

For PET data, pixel values will be displayed in SUV units if:

• Units (0054, 1001) = BQML, CNTS or GML

• Pixel values will be displayed according to the value of the Units (0054,1001) tag if the value is different from the three values above. See here for possible units values.

• Pixel values won’t have any unit if the Units (0054,1001) is missing or has no value.

If the condition above is met, the following DICOM tags are required to convert PET data in SUV units:

• RadiopharmaceuticalInformationSequence (0054,0016)
  • Radionuclide Half Life (0x0018,0x1075) (in seconds)
  • Radiopharmaceutical Start DateTime (0018,1078) or `Radiopharmaceutical Start Time (0x0018,0x1072)
  • Radionuclide Total Dose (0x0018,0x1074)
• SeriesDate (0008,0021)
• SeriesTime (0008,0031)
• CorrectedImage (0028,0051): needs to contain ATTN and DECY
• Units (0054, 1001)
• DecayCorrection (0054,1102)→ needs to be START
• AcquisitionDate (0008,0022)
• AcquisitionTime (0008,0032)
• PatientWeight (0010,1030)

SUVs are calculated from DICOM metadata based on the logic summarized by the Quantitative Imaging Biomarkers Alliance on their wiki page.

Known limitations and unsupported data

V3 viewer

Non-standard SOPClassUIDs

Non-standard SOPClassUIDs are currently not supported. Please refer to the list of supported SOPClassUIDs.

Series with multiple multi-frame images

A multi-frame image is defined as one file containing multiple images. The viewer currently does not support image series that consist in multiple multi-frame images.

Maximum number of images in a series

The viewer currently only supports series with a maximum number of 5,000 single images.

Ultrasound data

Data with PhotometricInterpretation (0028,0004) = PALETTE COLOR is currently not supported.