DICOM Structure Basics
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DICOM Structure Basics Gunjan Patel MS - Medical software, BE-Biomedical Engineer PGD-Quality Management Email: [email protected]
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Digital Imaging and Communications in Medicine (DICOM) is a standard for handling, storing, printing, and transmitting information in medical imaging. It includes a file format definition and a network communications protocol. The communication protocol is an application protocol that uses TCP/IP to communicate between systems. DICOM files can be exchanged between two entities that are capable of receiving image and patient data in DICOM format.DICOM enables the integration of scanners, servers, workstations, printers, and network hardware from multiple manufacturers into a picture archiving and communication system (PACS). The different devices come with DICOM conformance statements which clearly state the DICOM classes they support. DICOM has been widely adopted by hospitals and is making inroads in smaller applications like dentists' and doctors' offices.
Transcript of DICOM Structure Basics
DICOM Structure Basics
Gunjan Patel
MS - Medical software, BE-Biomedical Engineer
PGD-Quality ManagementEmail: [email protected]
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Content
• History• Introduction • Why DICOM?• DICOM Services Class• Basic Terminology• Exa.- RIS connection• Uses of DIOCM
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History
• 1985-1988 : • Joint effort between Radiologist and Manufacturers to
specify ACR-NEMA 1.0 and 2.0– ACR : American College of Radiology– NEMA : National Electrical Manufacturer Association
• 1993 :• 9 parts of DICOM (3.0)
• 2007 :• 18 parts of DICOM - 126 Supplements
• DICOM is developed under joint efforts of– ACR (American College of Radiology) – NEMA (National Electrical Manufacturers Assoc.) …… also more than
25 vendors…
DICOM is continuously growing
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Introduction
• Digital Imaging and COmmunication in Medicine
DICOM is not just an image or file format. It is an all-encompassing data transfer, storage, and display protocol built and designed to cover all functional aspects of digital medical imaging
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Why DICOM ?
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Contin….
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Contin….
• Need for Digital Image Generation • More need for Digital Transfer/Archiving
(PACS) • More need for Post-Processing• More need for Cross-Vendor Compatibility • Need for Communication via
Networks/Media
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DICOM Services Class
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DICOM Terminology
• DICOM File Format• Information Object Definition (IODs)• Application Entity Title (AE Title)• Service Class User/Provider (SCU/SCP)• Unique IDentifier (UID)• Transfer Syntax• Value Representations (VR)
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DICOM File FormatDICOM File Format
DICOM FileMeta
Information
DICOMData Set
DICOM File Format (Ref: PS 3.10, Sec.7.1)
FilePreamble
DICOM Prefix
FileMeta
Eléments
128 Bytes(set to 00H by default)
DICMAttribute Name Tag Type
Group Length (0002,0000) 1
File Meta Information Version (0002,0001) 1
Media Storage SOP Class UID (0002,0002) 1
Media Storage SOP Instance UID(0002,0003) 1
Transfer Syntax UID (0002,0010) 1
Implementation Class UID (0002,0012) 1
Implementation Version Name (0002,0013) 3
Source Application Entity Title (0002,0016) 3
Private Information Creator UID(0002,0100) 3
Private Information
(0002,0102) 1C
ONEDICOM
SOPInstance
as sent during
networktransfer
Group 0002H elements are always encoded in
Explicit VR Little Endian
A DICOM Image File is morethan an image stored in a File
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Information Object Definition
Patient Entity
Study Entity
Series Entity
Image Entity
IOD Modules
General Image
Image Pixel...
Rows
Columns
Pixel Data
...
Data ElementsThe atomic piece of information in DICOM- Contains the actual information
Set of Data Elements that are semantically gathered- Modules may be general (e.g. General Image)- Modules may be specific (e.g. CT Image)
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DICOM Service and IOD
I am sending a CT Image to you“ “
A verb(an action)
A noun(an object)
Real world:
DICOM: Service IOD
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Application Entity Title (AE Title)
• AE is essentially the name of a DICOM device or program used to uniquely identify it (you cannot have two identical AEs in your PACS network)
• Even though DICOM does not have strict requirements for AE naming, AEs are typically labeled with numbers and uppercase characters only – no spaces, punctuation signs, or other characters. In fact, it is not uncommon to see DICOM units that would accept only uppercase alphanumeric AEs.
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Application Entity Title (AE Title)
John“ Hi . Can I send you a CT Image?“Tom , I am
Communicator’sNames
AE Title(s)
An AE Title must be UNIQUE on a given network
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Calling AE Title / Called AE Title
John“ Hi . Can I send you a CT Image?“Tom , I am
Calling AE Title Called AE Title
CommunicationInitiator Name
CommunicationRecipient Name
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Service Class User/Provider (SCU/SCP)
Service Class Userrole
Service Class Providerrole
SCPSCU
I am sending a CT Image to you“ “
User Provider
SCU’s are initiating the actions. Therefore, they are usually initiating the communication (i.e. the association)
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DICOM Storage
Storage (SCU)
Modality
Other services of DICOM • Verification• Query/Retrieve• Modality Worklist
• Allows a system to send object data to a remote node.
• Object data may be Images (e.g. CT images), Waveforms, Mammo CAD, etc.
Storage (SCP)
Remote Node
Image SendImage 1.2.840.15.1
Store ResponseResponse:Status = SUCCESS
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But a single zero component is OK
1.2.840.115621.2.0.456.632.478 – Format is correct
• No Leading zero’s in UID string components are allowed.
1.2.840.115621.4.3.0596632.726 – ill formatted
Unique IDentifier (UID)
• UIDs are an internal DICOM mechanism to uniquely identify:Studies, Series, Images, Equipments, SOP Classes, etc…
• A UID is a string of up to 64 Characters including digit numbers (“0” to “9”) and “.” e.g. SOP Instance UID = 1.2.840.113619.2.65.3.200583648570.2428.1178103577.1
• This string MUST be UNIQUE around the world. For instance:• A SOP Instance UID of an image shall never be equal to the SOP Instance UID of
another image
• An Image SOP Instance UID shall never be equal to a Series Instance UID
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Transfer Syntax
A transfer syntax is the encoding methodology used to send data over the network, or the methodology used to write data to a physical media
Rx II
Example:Two different Transfer Syntaxes to represent the same information
The same semantic is conveyed, but using different encoding mechanisms
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DICOM Transfer Syntaxes (cont’d)
Big Endian versus Little Endian byte ordering :
DICOM defines two different byte orderings that affect binary values sent on more than 1 byte (typically: short integer, long integer, float values).
Example on a 2 byte value: 0x3568
versus
1 Byte
6835
Big Endian
1 Byte
68 35
Little Endian
1 Byte 1 Byte
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DICOM Transfer Syntaxes (cont’d) Explicit VR versus Implicit VR
VR stands for Value Representation. It describes the type and the format of the information sent in a DICOM Data Element.
For instance, the Patient Date of Birth format is a 8 characters string following the format : YYYYMMDD (e.g. 19980625)
Explicit VR means that the VR is (explicitly) sent in the DICOM Message.
Implicit VR means that no VR is sent in the message. Therefore, to know the VR, a product will have to use its own internal dictionary.
In both cases, the VR used by products for Standard Elements shall be the same as the one defined in the DICOM Data Dictionary
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Value Representations (VR)
• Clinical data comes in a wide variety of formats.– Ex. Distances measured in millimeters, time in seconds,
• patient names are typically written in alpha-betic characters, and so on.
• The DICOM standard defnes 27 basic data types, known as value representations (VRs),
• which are designed to encapsulate all possible clinical data types.
• Each VR has its own abbreviated two-letter name, a defnition of what it represents, a description of what characters are allowed in its data, and a pre-scribed data length.
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A specific VR for each need
•Free Form Text VR:• SH: Short String• LO: Long String• ST: Short Text• LT: Long Text• UT: Unlimited Text
•Math VR:• IS: Integer String• DS: Decimal String• US: Unsigned Short• SS: Signed Short• UL: Unsigned Long• SL: Signed Long
•Fixed Format VR:• DA: Date• TM: Time• DT: DateTime• PN: Person Name
•Other VR:• OB: Other Byte• OW: Other Word• OF: Other Float • SQ: Sequence• …
DICOM defines a set of 27 VRs identified with two capital letters. For instance:
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DICOM Print Management
DIC
OM
A Standard Interfaceto Share Printers
Old Printer DICOMSpooler
• DICOM print (Grayscale and/or color) links Printers with Modalities and Workstations on a standard network
• A lot of flexibility to support all features available on various vendor’s printers
New Printer
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CD-ROMCD-R
130 mmMOD
(650 MB,1.2, 2.3, 4.1GB)
90 mm MOD(128, 230, 540, 640 MB, 1.3, 2.3 GB)
DVD-ROM -R/+R/-RW/+RW
MEDICALDIRECTORY
DICOM for Media Interchange
ALL DICOM
INFORMATION OBJECTS
The same image objects as defined for Network exchange are usable on physical media
The DICOM Directory (a.k.a. DICOMDIR) facilitates media browsing
USBMedia
ISO 9
660
UDFDOS
DOS
ISO 9
660
Leve
l 1FAT
16 F
S
DICOM Relies on Broadly Available Media Storage Technology
DICOM File Format
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Uses of DIOCM
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Feedback and
Query ???
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Referances
• DICOM Cook Book -for Implementations in Modalities• Digital Imaging and Communication in Medicine (DICOM)-
OS Priyankh• http://www.mediacy.com/index.aspx?
page=IQDICOM_Service• http://medical.nema.org/
