1. DICOM explained in the context of Structured Reporting
NEMA workshop, Washington DC
March 29-30, 2000
Herman Oosterwijk,
OTech Inc.

2. Objective:
To get a basic understanding of DICOM services and objects in the context of Structured Reporting:
DICOM objects (IOD’s)
DICOM encoding: Data elements, VR, sequences, Codes
DICOM exchange media

3. Parts of the Standard: 1. Overview 2. Conformance
3. Information Objects
4. Services Class Specifications
5. Data Structures and Semantics
6. Data Dictionary
7. Message Exchange

4. Parts of the Standard: 8. Network Support 9. Point to point
10. Media Storage and File format
11. Media Storage Application Profiles
12. Physical Media
13. Point to point Print mgt
14. Greyscale display function standard
xx. Supplements!!!

5. DICOM key parts: Common Information Model
Conformance claims to define functionality:
Matching is critical
Roles: SCU/SCP
Unique Identification of objects:
Each DICOM object is unique
Documentation tools such as Macros

6. Key DICOM concept==SOP Class
(Service defn + Information Object Defn):
DIMSE C-Store
Service Elt.
Info Object SR Object
Defn (IOD)
SOP Class C-Store SR
SOP Instance C-Store Mrs. Smith SR

7. Relationship between:
Service Class
Information Object Definition(IOD)
DIMSE Service Elements
Service Object Pair (SOP) Class
Service Elements:
N-Create
N-Set
N-Get
N-Delete
N-Action
N-Event-rep
C-Store
C-Get
C-Find
C-Move
C-Echo
SVC Classes:
Verification
Storage
Study notf.
Print Mgt
Patient Mgt
Study Mgt
Results Mgt
Storage Commnt
Query/Retrieve
BasicWlist Mgt
DCM 7
(=SOP Class)
IOD-->Module-->Attrib
DCM 3
DCM 5,6
DCM 4

8. Information Object Definition (IOD):
IOD Description; i.e. what is the real world object (Information Entities-IE) that is represented. Can be one or more IE’s (Composite, Normalized)
Examples:
Image IOD: Patient, Study, Equipment, Image ----> Composite
Patient IOD: Patient info ---->Normalized

9. Information Object Definition (IOD):
IOD Entity-Relationship model; provide the context (relationships) between the IE’s
This information model is critical!
IOD Module table; which modules provide the attributes for the IOD
Modules are defined for “convenience reasons” (all patient info together, all image info together....)
Modules contain Attributes (Pat. name, etc.)

10. SR Information Model: Patient 1 is the subject of 1,n Study 1 contains
spatially
defines
Series
creates
1,n 1 1 1
Frame of Reference
Equipment
contains
0,n
0,n
0,1
0,n
Presentation
Curve
Modality
Image
State
LUT
0,n
0,1
0,n
0,n SR
Stored
VOI LUT
Overlay
Document
Print

13. Module Definition:
Attribute Name, Tag, Type, Description

14. Value of data elements can belong to a Set:
Defined Terms:
Can be extended (e.g. Modality: CT,MR, ES, SR, etc.)
Enumerated values:
No extensions, additions (e.g. Patient Sex: M, F, O)
Value Multiplicity:
More than one value, requires separator (e.g. Other Patient Names)

15. Type Designation: 1: Required (e.g. pixel spacing)
1C: Required when condition met (e.g. pixel aspect ratio)
2: Required, can be “0” if unknown (e.g. Patient Name, Accession number)
2C: Conditional (e.g. patient positioning)
3: Optional (e.g. Other Patient Name)

16. DICOM Part 5-6 Data set and structures:
Data Element Tag, Optional Value Representation, Length, Value Field
Data
Elem
Data
Elem
Data
Elem
Data
Elem
Tag VR
Value
Length
Value Field

17. Data set and structures (ctd):
Tag: Identifies Attribute
Value representation (VR): Groups similar attributes for identification and definition purposes, e.g.:
Patient name, Physician name, Other Patient names, etc.: VR is “PN”
Birth date, Exam date, etc.: VR is “DA” VR syntaxes specified in part 5

18. Data set and structures (ctd):
Implicit VR: Assumed based on tag
Explicit VR: Explicitly specified
Note: VR is negotiated during association!
Explicit VR: 0010,0010 PN 10 Smith^John
Implicit VR: 0010, Smith^John

19. Example of a DICOM Message:

20. Sequences:
VR =“SQ”
Sequence contains zero or more items, which contains a set of Data Elements
Used to encode repeating sets
Accommodates multilevel nesting (recursion)
Explicit length SQ: value of bytes in length field
Undefined length SQ: requires flag in length field and SQ and item delimiters (sppt rqd)

21. SR Example: * contains contains contains selected from
Document Root Node CONTAINER
Leaf Node CODE
"
Chest X-ray
" (Document Title)
has concept mod
"
Views = PA and Lateral
"
contains
contains
contains
contains
Content Node CODE
Leaf Node IMAGE
Heading Node
Heading Node
"
finding
= mass"
"
Baseline
"
CONTAINER
CONTAINER "
Specific
"
Conclusions
"
Image Findings
"
margination
infiltrative"
has properties
Leaf Node CODE
has properties
contains
contains
Leaf Node NUM
Content Node CODE
Content node SCOORD
" =
"
conclusion
= probable
"
diameter
= 1.3 cm"
"
best illustration of
malignancy"
findings
"
inferred from
inferred from
selected from
Leaf Node IMAGE
Has
obs context
Has
obs context
Has
obs context
Content Node PNAME
Content Node UIDREF
Content Node PNAME
"
Recording Observe
r =
"
Study Instance UID of
"
Patient-Data-Acquisition
Smith^John^^Dr^"
Evidence Directly Examined
Subject =
Homer^Jane^^^"
by RO
= " *
Relationship Modes
= By-value
= By-reference

22. SR Example:
margination
infiltrative"
has properties
Leaf Node CODE

23. Codes:
SNOMED: Systematized Nomenclature for Human and Veterinary Medicine; maintained by College of American Pathologists (CAP); anatomic identifiers, observations, etc.
Requires license fee
LOINC: Logical Observation Identifiers, Names and Codes (LOINC); measurements
No license (free)
CPT, ICD9: Procedure Codes
BI-RADS: Mammography
99SDM, SDM, DTMR

24. Codes, Why?:
Human language is not exact, many variations are possible:
e.g. Exam type is:
Chest
Thorax
Chest PA/LAT
chest

25. Codes, where, how to encode:
From CAP, DUKE website, in supplements, eventually in new DICOM Supplement 53.
Encoding:
Coding Scheme
Version #
Code
Meaning
Optional Extended coding for context information

26. Example from Digital X-Ray (DX) IOD:
Makes extensive use of Coded data entries using standard vocabulary:
Instead of specifying “sagittal” for View Code, one specifies:
Code Value : R
Coding Scheme : SNOMED
Scheme Version: Version 1.0
Meaning : Sagittal

27. Modality Worklist Management
DICOM Services:
Information System
Modality Worklist Management
Storage
Storage Commit
Query/Retrieve MR
Print
Performed Procedure Step
Verification

28. Storage Service class (ctd):
SCP level of conformance:
Level 0 (local): user defined subset will be stored only
Level 1 (base): Type 1 and 2 attributes will be stored, others may be discarded. SCP is not required to validate the Attributes
Level 2 (full): Type 1,2,3 will be stored SCP is not required to validate Attributes
Patient ID, Study Instance UID and Series Instance UID may be coerced (negotiated)

29. Waveforms: Why yet another way of encapsulating waveforms ?
Current mechanisms are proprietary; timing seems ripe for standardization
Relationship between images and waveforms is key
Existing Curve specification in DICOM was not sufficient

30. Waveforms: Relate Images

31. DICOM Media Specifications:
Medical Imaging Application
DICOM Application Entity
OSI Upper layer svc boundary
DICOM File svc boundary
DCM
Presn. A B C
Media
Format
Media
Format
Media
Format
OSI
50 pin
TCP/IP
Phys.
Medium
Phys.
Medium
Phys.
Medium

32. DICOM Media Specifications (ctd):
DICOM Application Entity
Basic Dir.
Service / Object Pairs
part 10
DICOM File Format
part 11
Media Formats: e.g. File data structures
part 12
Physical Media: e.g. CD-R; 90 mm MOD, etc.

33. FILE SET DICOM SOP Instance DICOM SOP Instance DCM File Meta Info
Data
Set
DCM
File
Meta
Info
DICOM
Data
Set
FILE SET