The standard for Digital Imaging and Communications in Medicine.

1. DICOM FORMAT
 BY:LOKENDER YADAV

2. What is DICOM?
 The standard for Digital Imaging and
Communications in Medicine.
 Developed by the National Electrical
Manufacturers Association (NEMA) in conjunction
with the American College of Radiology (ACR).
 Covers most image formats for all of medicine.
 Specification for messaging and communication
between imaging machines.

3. A little history
 The first version was ACR-NEMA, released in 1985.
 Its goal in developing a standard was
 To enable users to retrieve images and
associated information from digital imaging
equipment in a standard format using point-to-
point connection.
 To hide differences same across multiple image
equipment manufacturers.
 To handle developing network and image standarts,
a new standart, DICOM, was proposed in 1981.

4. DICOM Application Domain
MAGN
ETOM
Information Management System
Storage, Query/Retrieve,Storage, Query/Retrieve,
Study ComponentStudy Component
Query/RetrieveQuery/Retrieve
Results ManagementResults Management
Print ManagementPrint Management
Media ExchangeMedia Exchange
LiteBox

5. Summary of DICOM Features
 NETWORK PROTOCOL
●
DICOM incorporates negotiation to permit peers
to agree on the functions to be performed
 MESSAGE ENCODING
●
DICOM defines 24 data types (V2.0 had 4)
●
DICOM message encoding includes JPEG
compression (17 varients)
●
DICOM supports multiple character repertoires

6. Summary of DICOM Features
 OBJECT DATA MODEL
●
DICOM is based on a completely specified data
model
●
DICOM includes a robust UID mechanism
 DATA DICTIONARY
●
DICOM includes a large number of new data
elements
 SERVICE CLASSES
●
DICOM defines classes of service for specific
applications (e.g. image management, printing)
and conformance levels

7. DICOM Objects
 Things such as images, reports, and patients are all
objects and are called information objects.
 Two kinds of objects in DICOM:
 Composite objects (Old objects inherited from NEMA).
 Normalized objects (New objects defined in DICOM).
 All objects and their format constitutes Data Dictionary.
 DICOM uses UIDs to identify information objects, such as
the images, reports, or transfer syntaxes.
 The form of the UID conforms to an international
standard.
 1.2.840.10008 is the root and the same for every DICOM
UID.
 Example: UID for the DICOM explicit VR little endian
transfer syntax is 1.2.840.10008.1.2.1

8. DICOM Service Classes
 Composite
●
Verification
●
Storage
●
Query/Retrieve
●
Study Content Notification
 Normalized
●
Patient Management
●
Study Management
●
Results Management
●
Basic Print Management

9. DICOM Service Elements
 Complex services are built using service elements,
called DICOM message service elements, or DIMSEs.
 There are both composite and normalized services for
composite and normalized information objects.
 There are 5 DIMSEs that are used for composite
information objects (called DIMSE-C) and 6 that are
used for normalized information objects (called DIMSE-
N).
 Two categories of DIMSEs:
 operations (such as "store")
 notifications (such as "event report”)

10. DIMSE-C Services
 DIMSE-C services:
 Operations:
 C-Store
 C-Get
 C-Move
 C-Find
 C-Echo
 No notification services

11. DIMSE-C Services
The C-STORE service is invoked by a DIMSE-service-user to
request the storage of Composite SOP Instance information
by a DIMSE-service-user.
The C-FIND service is invoked by a DIMSE-service-user to
match a series of Attribute strings against the Attributes of
the set of SOP Instances managed by a DIMSE-service-user.
The C-FIND service returns for each match a list of requested
Attributes and their values.
The C-GET service is invoked by a DIMSE-service-user to
fetch the information for one or more information objects
from a DIMSE-service-user, based upon the Attributes
supplied by the invoking DIMSE-service-user.

12. DIMSE-C Services
The C-MOVE service is invoked by a DIMSE-
service-user to move the information for one or
more Composite SOP Instances from a DIMSE-
service-user, to a third party DIMSE-service-user,
based upon the Attributes supplied by the
invoking DIMSE-service-user.
The C-ECHO service is invoked by a DIMSE-
service-user to verify end-to-end
communications with a DIMSE-service-user.

13. DIMSE-N Services
 DIMSE-N services:
 Operations:
 N-Get
 N-Set
 N-Action
 N-Create
 N-Delete
 Notifications:
 N-Event-Report

14. DIMSE-N Services
 N-EVENT-REPORT service is invoked by a DIMSE-
service-user to report an event about a SOP Instance
to a DIMSE-service-user.
N-GET service is invoked by a DIMSE-service-user to
request the retrieval of information from a DIMSE-
service-user.
N-SET service is invoked by a DIMSE-service-user to
request the modification of information by a DIMSE-
service-user.

15. DIMSE-N Services
N-ACTION service is invoked by a DIMSE-service-
user to request a DIMSE-service-user to perform an
action.
N-CREATE service is invoked by a DIMSE-service-
user to request a DIMSE-service-user to create an
instance of a information object.
N-DELETE service is invoked by a DIMSE-service-
user to request a DIMSE-service-user to delete an
instance of a information object.

16. DICOM Service-Object Pair (SOP)
 The service classes and information objects are
combined to form SOP.
 The SOP class is the elemental unit of DICOM.
 Everything that DICOM does is based on the use of
SOP classes.

17. DICOM Service-Object Pair (SOP)
SOPSOP
Data DictionaryData Dictionary
Information ObjectInformation Object DIMSE Service ElementDIMSE Service Element

18. DICOM File Format (Overview)
A single DICOM file contains:
 A header (which stores information about
the patient's name, the type of scan, image
dimensions, etc)
 Image data (in compressed (bitmap) or
uncompressed form (jpeg, gif...))

19. DICOM File Header
 DICOM requires a 128-byte preamble (usually set to zero).
 'D', 'I', 'C', 'M' letters comes next.
 The rest is the real header information in groups.
 For example: group 0002hex is the file meta information group.

20. DICOM File Header

21. DICOM File Header
 The meaning of some fields:
 0002:0010 --> Reports the structure of the image data
 0028:0002 --> Samples Per Pixel
 0028:0004 --> Photometric Interpretation
 0028:0100 --> Bits Allocated
 ...

22. Association Services
 Before everything, Association establishment
must be done.
 During Association establishment, A DIMSE-
service-user exchanges initialization
information.
The initialization information includes:
 Application context
 DIMSE-specific user information
 DIMSE service information
 Presentation and session requirements

23. Association Services
 A-ASSOCIATE Service is invoked by a DIMSE-
service-user with related parameters to establish
an Association with another DIMSE-service-user.
 Association release is done using A-RELEASE and
A-ABORT services.