1. DICOM in Ophthalmology, an Example of a New Enhanced Multiframe Object
Herman Oosterwijk
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2. 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)

3. 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

4. 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)

5. 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

6. Sample application: Cardiac Imaging

7. 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…)

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

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

10. 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.

11. Functional groups:

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

13. OPT multiframe image sample:

14. IOD: Ophthalmology: IE Module Reference Usage Patient C.7.1.1 M Study
General Study
C.7.2.1
Patient Study
C.7.2.2 U
Series
General Series
C.7.3.1
Ophthalmic Tomography Series
C.8.17.X1
Frame of Reference
C.7.4.1
C – Required if Reference Image available
Synchronization
C.7.4.2
Equipment
General Equipment
C.7.5.1
Enhanced General Equipment
C.7.5.2
Image
Image Pixel
C.7.6.3
Enhanced Contrast/Bolus
C 7.6.4b
C – Required if contrast was administered
Multi-frame Functional Groups C
Multi-frame Dimension C
Acquisition Context C
Cardiac Synchronization C
C – Required if cardiac synchronization was used
Ophthalmic Tomography Image
C.8.17.X2
Ophthalmic Tomography Acquisition Parameters
C.8.17.X3
Ophthalmic Tomography Parameters
C.8.17.X4
Ocular Region Imaged C
SOP Common
C.12.1

15. MULTI-FRAME FUNCTIONAL GROUPS MODULE ATTRIBUTES
Attribute Name
Tag
Type
Attribute Description
Shared Functional Groups Sequence
(5200,9229) 2
Sequence that contains the Functional Group Macros that are shared for all frames in this SOP Instance.
>Include one or more Functional Group Macros that are shared by all frames.
Per-frame Functional Groups Sequence
(5200,9230) 1
Sequence that contains the Functional Group Macros corresponding to each frame of the Multi-frame Image.
>Include one or more Functional Group Macros.

16. 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
Cardiac Trigger
C – Required if Cardiac Synchronization Technique (0018,9037) equals other than NONE May be present otherwise.
Contrast/Bolus Usage
C – Required if Contrast/Bolus Agent Sequence (0018,0012) is used. May not be used as a Shared Functional Group
Ophthalmic Frame Location U

17. Implementation issues:
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

18. 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

19. Herman Oosterwijk: herman@otechimg.com www.otechimg.com
Thank you!
Herman Oosterwijk: