DICOM INTERNATIONAL CONFERENCE SEMINAR April 8 10 2008

DICOM INTERNATIONAL CONFERENCE & SEMINAR April 8 -10, 2008 Chengdu, China DICOM in Ophthalmology, an Example of a New Enhanced Multiframe Object Herman Oosterwijk Add logo if desired

Enhanced Multiframe • Objective: This presentation will answer the following question: – What are the major features of the new generation enhanced multiframe DICOM objects, how to understand this new type of object, and how does a typical enhanced multiframe look like, in particular OCT (Optical Coherence Tomography)

Enhanced multiframe: • Agenda: – Major features of the new generation of DICOM objects, i. e. enhanced multiframe – Steps to encode/decode this new type of object – OCT object, a sample enhanced multiframe

Traditional Multiframe objects: Vector • Single image, multiple frames • US, NM, XA, RF, SC, VL • Simple structure: – – # frames Frame rate Frame index pointer Frame increment pointer (NM)

Enhanced multiframe: • Why a new generation of objects: CT, MR, ophthalmology, mammography tomo, XA, RF – Imaging is moving from pixels in slices (2 -D) to voxels (3 -D) and beyond (n-D), i. e. time, space, frequency, flow: functional imaging (CTA, etc. ) – Simple “Study-Series-Image” hierarchy does not suffice anymore for organization, viewing, browsing, sorting using the appropriate hanging protocols – Text descriptions for Series leaves room for guessing

Sample application: Cardiac Imaging

Enhanced multiframe: • Solution: enhanced multiframe – Many Attributes are required (Type 1) – Where possible, Attribute contents are encoded – Definition of multiple dimensions – Header size reduction – Protocol efficiency: 1000 slice CT • 1000 times C-Store RQ…RS vs 1 time RQ…RS – ONE structure serving as a template for all new SOP Classes (CT, MR, XA, RF, OCT, MG…)

Dimension example: 313 Trigger Delay Time 5 4 3 2 1 Dimension Index Values ID 1 100 ms 5 4 50 ms 5 0 ms Time 4 3 3 2 2 1 ID 2 ID 3 1 1 Dimension Indexes (3): 1. Trigger Delay Time 2. Stack ID 3. Position

Enhanced multiframe encoding: • Split header: – Fixed information – Variable information (keep as minimum as possible) – Some information can be in both places (contrast) Header Part 1 Header Part 2 Pixels in frames Fixed per frame: Name, ID…. Accession #, Study ID… KV, m. As…. Orientation…. #rows, columns, bits Variable for one/more frames: Position Time Scab type

Enhanced multiframe: • Header part 2 (variable) definition: – Implemented as “functional groups”: SQ with zero, one, or more items – Documented as “macros” in Multi-Frame Functional Group Module – Common functional groups, used for multiple modalities, such as “Frame Content Macro” – Structure of dimensions, and concatenations is “generic”: Multi-frame functional group and dimension modules – Modality specific functional groups, e. g. for MR, ophthalmology, etc.

Functional groups:

Multiframe Functional Groups: Shared attributes Per-frame attributes Pixel data

OPT multiframe image sample:

Ophthalmology: IOD: IE Module Reference Usage Patient C. 7. 1. 1 M Study General Study C. 7. 2. 1 M Patient Study C. 7. 2. 2 U General Series C. 7. 3. 1 M C. 8. 17. X 1 M Series Ophthalmic Tomography Series Frame of Reference C. 7. 4. 1 C – Required if Reference Image available Synchronization C. 7. 4. 2 C – Required if Reference Image available Equipment General Equipment C. 7. 5. 1 M Enhanced General Equipment C. 7. 5. 2 M Image Pixel C. 7. 6. 3 M Enhanced Contrast/Bolus C 7. 6. 4 b C – Required if contrast was administered Multi-frame Functional Groups C. 7. 6. 16 M Multi-frame Dimension C. 7. 6. 17 M Acquisition Context C. 7. 6. 14 M Cardiac Synchronization C. 7. 6. 18. 1 C – Required if cardiac synchronization was used Ophthalmic Tomography Image C. 8. 17. X 2 M Ophthalmic Tomography Acquisition Parameters C. 8. 17. X 3 M Ophthalmic Tomography Parameters C. 8. 17. X 4 M C. 8. 17. 5 M C. 12. 1 M Image Ocular Region Imaged SOP Common

MULTI-FRAME FUNCTIONAL GROUPS MODULE ATTRIBUTES Attribute Name Shared Functional Groups Sequence Tag Type Attribute Description (5200, 9 229) 2 Sequence that contains the Functional Group Macros that are shared for all frames in this SOP Instance. 1 Sequence that contains the Functional Group Macros corresponding to each frame of the Multi-frame Image. >Include one or more Functional Group Macros that are shared by all frames. Per-frame Functional Groups Sequence (5200, 9 230) >Include one or more Functional Group Macros.

OPHTHALMIC TOMOGRAPHY FUNCTIONAL GROUP MACROS Function Group Macro Usage Pixel Measures M Frame Content M – May not be used as a Shared Functional Group. Plane Position C – Required if no Ophthalmic Photography Reference Image available Plane Orientation C – Required if no Ophthalmic Photography Reference Image available; May be present otherwise Referenced Image C – Required if Ophthalmic Photography Reference Image available. Derivation Image C – Required if the image or frame has been derived from another SOP Instance. Frame Anatomy M Cardiac Trigger C – Required if Cardiac Synchronization Technique (0018, 9037) equals other than NONE May be present otherwise. Contrast/Bolus Usage Ophthalmic Frame Location C – Required if Contrast/Bolus Agent Sequence (0018, 0012) is used. May not be used as a Shared Functional Group U

Enhanced multiframe: • Implementation issues: – Support by vendors, especially PACS archives and even more workstations: growing, but slowly – Mixed environments: new and old, especially for established modalities (CT, MR, XA, RF) – Handling very large files: concatenation (not allowed for OCT) – splitting up into mini-multi frames – Retrieval on frame level: to be added to standard

Conclusion: • New, enhanced multiframe objects are defined in DICOM, some for existing, some for new modalities • These new objects provide better interoperability for n-D (esp. dynamic) objects, allow for more sophisticated display protocols, and give better performance • Modalities, and to a lesser degree PACS systems are starting to support it; a mixed environment is inevitable

DICOM INTERNATIONAL CONFERENCE & SEMINAR April 8 -10, 2008 Chengdu, China Thank you! Herman Oosterwijk: herman@otechimg. com www. otechimg. com