Transcript DICOM in Ophthalmology, an Example of a New Enhanced Multiframe Object DICOM INTERNATIONAL

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:
3\1\3
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
ID 2
1
1
ID 3
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, mAs….
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:
Other attributes
Shared Functional Groups Sequence
> Functional Group A Macro
Functional Group Macros
shared for all frames
É..
> Functional Group K Macro
Pe r-f rame Functional Groups Sequence
Ite m 1 (Frame 1)
> Functional Group B Macro
> Functional Group C Macro
Sequence of repeating
Functional Group Macros for
each individual frame
É..
> Functional Group M M acro
Ite m 2 (Frame 2)
É..
> Functional Group B Macro
> Functional Group C Macro
É..
> Functional Group M M acro
É..
Pixel Data
Frame 1
Item n (Frame n)
> Functional Group B Macro
> Functional Group C Macro
É..
> Functional Group M M acro
Other attributes
Frame 2
É..
Frame n
Note: The Functional Group Macros A , B, C, etc. are examples to illustrate the Multi-frame Functional Groups. The
actual F unctional Group Sequences are defined elsewhere.
Multiframe Functional Groups:
Shared attributes
Per-frame attributes
Pixel data
OPT multiframe image sample:
Ophthalmology:
IOD:
IE
Module
Reference
Usage
Patient
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.X1
M
Series
Ophthalmic Tomography Series
Frame of
Reference
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 7.6.4b
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.X2
M
Ophthalmic Tomography Acquisition
Parameters
C.8.17.X3
M
Ophthalmic Tomography Parameters
C.8.17.X4
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
(5200,92
29)
2
Attribute Description
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
(5200,92
30)
1
>Include one or more Functional Group Macros.
Sequence that contains the Functional Group
Macros corresponding to each frame of the Multiframe Image.
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:
[email protected]
www.otechimg.com