DICOM Supplement 188 Multi-Energy CT Imaging DICOM Working Group 21 Computed Tomography
Rationale Short introduction of Multi Energy (ME) s Overview: Imaging techniques, including scanning, reconstruction, processing, when the scanner utilizes multiple energies from the X-Ray beam spectrum, as opposed to the conventional CT imaging, when a single (accumulated) X-Ray spectrum is used. The existing CT and Enhanced CT (ect) IODs do not adequately describe the new CT multienergy imaging. Although different vendors apply different scanning and detection techniques to achieve multi-energy images, there is large commonality in the generated diagnostic images. Goals for ME implementation: provide new essential ME information (acquisition, reconstruction and processing attributes) within the IOD. facilitate fast and easy adoption of standard based ME imaging across the imaging community, both modalities and PACS/Displays. address (or at least to minimize) the risk of mis-interpretation when the ME images are displayed by a display does not support the new attributes of the ME-image, including incorrect measurements adapt existing attributes of the CT / Enhanced CT IOD to fit ME techniques. 2
Overview Multi Energy Imaging Standard CT Objective Quantification Labeling Visualization Virtual Monoenergetic (VMI) Effective Atomic Number (Z) Electron Density - Specific Iodine Map; Bone Density - Removed Virt. Non- Contrast; Virt. Non-Ca; Proportional Map Discrete Labeling Probability Map Value based Map Gout crystals CT IOD - Modified Highlighted; Partially- Suppressed Other IOD Color Overlay Color Blending Color Map
Organization Structure Multi-energy CT Macro (new added to CT IODs) Multi-energy Flag (Y/N) Multi-energy CT Acquisition Sequence (1C, 1 item) Multi-energy CT Acquisition Sequence (1-N) Multi-Energy Source Technique Multi-Energy Detection Technique Other ME-specific attributes Common CT Acquisition Macro Multi-energy CT Processing Sequence (1C, 1 item) Decomposition Method Decomposition Basis Sequence (2-N items, one for each basis) Other decomposition attributes Multi-energy CT Characteristics Sequence (1C) Monochromatic Energy Equivalent (for Virtual Monochromatic ) Multi-energy Quantification CT Macro Specific Code Sequence Modification Sequence Multi-energy Labeling CT Sequence (1 item) Labeling Type Modification Sequence 4
Multi-Energy CT Acquisition Techniques X-Ray Source Scanned Object Detector Generating different X-Ray Energies: Discriminating Energies: KVP Filter Other Parameters Multiple Layers Photon Counting Methods to separate at least two energies include Multiple Scans of the same area with diff parameters Multiple X-Ray Sources and/or Detectors Switch KVP during the rotation One source with Multi-Layer Detector One source with Photon Counting Detector
Objective s Data Acquisition Decomposition to Base Components Generation of Diagnostic images A1 A2 An M1 M2 Mn Virtual Monochromatic Effective Atomic Number Electron Density Acquisition Sequence Processing Sequence Characteristics Sequence (currently just kev for VMI)
s Data Acquisition Decomposition to and/or Classification of two or more s Generation of Diagnostic images A1 A2 An M1 M2 Mn Quantification Labeling Visualization Acquisition Sequence Processing Sequence Characteristics Sequence
s Generation M1 M2 Mn May be ignored / Not described -Specific Proportional Map Labeling s Examples:: - Iodine Map - Bone (Ca) Density Map Conventional CT or VMI o o o o o Subtract Suppress Highlight Compensate Recalculate M1 M2 Mn - Removed Visualization s Examples:: - Virtual Non-Contrast : COMPENSATED - Virtual Non-Calcium : COMPENSATED - Bone or Uric Acid Removed : SUBTRACTED (0) Examples:: - Tendon Enhancement: HIGHLIGHTED
Labeling s Discrete Labeling (most-probable material): Proportional: A BC 2 0: None 0.3 D 1: A 2: B contains 30% of material A 3: C Value based: Probability: 4 10 20 A = 0-15 B = 10-20 20% chance containing material A 0.2 A BC D 15 0 C = 18-50
Visualization s Color Overlay A B Overlay Blended C Structural A) A CT image that is windowed to highlight a particular material with a color map applied. It also may have a translucency applied to be able to see the image underneath. (E.g. Iodine image, Effective Z image) B) A structural image showing the anatomical structure. (E.g. Monochromatic image) C) The result image (combined information e.g. Secondary Capture, Blending, )