DICOM Structure Basics
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The document provides an overview of DICOM (Digital Imaging and Communications in Medicine), including its history, purpose, and basic terminology related to medical imaging protocols. It explains the structure of DICOM files, the importance of unique identifiers, and the roles of application entity titles in the communication between devices. Additionally, it highlights the need for compatibility and standardization in digital medical imaging, as well as the continuing evolution of DICOM standards.
DICOM Structure Basics
- 1. DICOM Structure Basics Gunjan PatelMS - Medical software, BE-Biomedical EngineerPGD-Quality ManagementEmail: gunjannpatel@gmail.com
- 2. ContentHistoryIntroduction Why DICOM?DICOM Services ClassBasic TerminologyExa.- RIS connectionUses of DIOCM2
- 3. History1985-1988 : Joint effort between Radiologist and Manufacturers to specify ACR-NEMA 1.0 and 2.0ACR : American College of RadiologyNEMA : National Electrical Manufacturer Association1993 :9 parts of DICOM (3.0)2007 :18 parts of DICOM - 126 SupplementsDICOM is developed under joint efforts ofACR (American College of Radiology) NEMA (National Electrical ManufacturersAssoc.) ……also more than 25 vendors…3DICOM is continuously growing
- 4. IntroductionDigital Imaging and COmmunication in Medicine4DICOM 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 imagingWhy DICOM?5
- 5. Contin….6
- 6. Contin….Need for Digital Image Generation More need for Digital Transfer/Archiving (PACS) More need for Post-ProcessingMore need for Cross-Vendor Compatibility Need for Communication via Networks/Media7
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- 10. DICOM TerminologyDICOM File FormatInformation Object Definition (IODs)Application Entity Title (AE Title)Service Class User/Provider (SCU/SCP)Unique IDentifier (UID)Transfer SyntaxValue Representations (VR)11
- 11. Attribute NameTagTypeGroup Length(0002,0000)1File Meta Information Version(0002,0001)1Media Storage SOP Class UID(0002,0002)1Media Storage SOP Instance UID(0002,0003)1Transfer Syntax UID(0002,0010)1Implementation Class UID(0002,0012)1Implementation Version Name(0002,0013)3Source Application Entity Title(0002,0016)3Private Information Creator UID(0002,0100)3Private Information (0002,0102)1CDICOM File FormatFilePreamble128 Bytes(set to 00H by default)DICOM FileMetaInformationDICOM PrefixDICMFileMetaElémentsONEDICOMSOPInstanceas sent duringnetworktransferDICOMData SetGroup 0002H elements are alwaysencoded in Explicit VR LittleEndianDICOM File Format (Ref: PS 3.10, Sec.7.1)A DICOM Image File is morethan an image stored in a File12
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- 13. Patient EntityRowsStudy EntityColumnsGeneral ImageSeries Entity...Image PixelPixel Data...Image EntityModulesIODData ElementsInformation Object Definition Set of Data Elements that are semantically gathered Modules may be general (e.g. General Image)
- 14. Modules may be specific (e.g. CT Image)The atomic piece of information in DICOM- Contains the actual information14
- 15. “Iam sendingaCT Imagetoyou“A verb(an action)A noun(an object)ServiceIODDICOM Service and IODReal world:DICOM:15
- 16. 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.16
- 17. Application Entity Title (AE Title)17JohnTom, I am“ Hi. Can I send you a CT Image?“Communicator’sNamesAE Title(s)An AE Title must be UNIQUE on a given network
- 18. JohnTom, I am“ Hi. Can I send you a CT Image?“CommunicationInitiator NameCommunicationRecipient NameCalling AE Title / Called AE TitleCallingAE TitleCalledAE Title18
- 19. “am sending a CT Image toIyou“UserProviderService Class User/Provider (SCU/SCP)SCPSCUServiceClass UserroleService Class ProviderroleSCU’s are initiating the actions. Therefore, they are usually initiating the communication (i.e. the association)19
- 20. Allows a system to send object data to a remote node.
- 21. Object data may be Images (e.g. CT images), Waveforms, Mammo CAD, etc. RemoteNodeModalityImage 1.2.840.15.1Image SendResponse:Status = SUCCESSStore ResponseStorage (SCU)Storage (SCP)DICOM StorageOther services of DICOMVerification
- 22. Query/Retrieve
- 24. Unique IDentifier (UID)UIDs are an internal DICOM mechanism to uniquely identify:Studies, Series, Images, Equipments,SOP Classes, etc…
- 25. 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
- 26. No Leading zero’s in UID string components are allowed.1.2.840.115621.4.3.0596632.726 – ill formatted But a single zero component is OK1.2.840.115621.2.0.456.632.478 – Format is correctThis string MUST be UNIQUE around the world. For instance:
- 27. A SOP Instance UID of an image shall never be equal to the SOP Instance UID of another image
- 28. An Image SOP Instance UID shall never be equal to a Series Instance UID21
- 29. Transfer SyntaxA transfer syntax is the encoding methodology used to send data over the network, or the methodology used to write data to a physical mediaExample:Two different Transfer Syntaxes to represent the same informationRx IIThe same semantic is conveyed, but using different encoding mechanisms22
- 30. Big EndianLittle Endian683568351 Byte1 Byte1 Byte1 ByteDICOM 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: 0x3568versus23
- 31. DICOM Transfer Syntaxes (cont’d)Explicit VRversus Implicit VRVRstands 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 VRmeans that the VR is (explicitly) sent in the DICOM Message.Implicit VRmeans 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 Dictionary24
- 32. 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.25
- 33. A specific VR for each needDICOM defines a set of 27 VRs identified with two capital letters. For instance:Fixed Format VR:
- 34. DA: Date
- 35. TM: Time
- 36. DT: DateTime
- 37. PN: Person Name
- 38. Other VR:
- 39. OB: Other Byte
- 40. OW: Other Word
- 41. OF: Other Float
- 42. SQ: Sequence
- 43. …
- 44. Free Form Text VR:
- 45. SH: Short String
- 46. LO: Long String
- 47. ST: Short Text
- 48. LT: Long Text
- 50. Math VR:
- 54. SS: Signed Short
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- 61. New Printer DICOMSpooler Old Printer DICOM Print ManagementA Standard Interfaceto Share PrintersDICOMDICOM print (Grayscale and/or color) links Printers with Modalities and Workstations on a standard network
- 62. A lot of flexibility to support all features available on various vendor’s printers31
- 63. MEDICALDIRECTORYDICOM for Media Interchange The DICOM Directory (a.k.a. DICOMDIR) facilitates media browsingThe same image objects as defined for Network exchange are usable on physical mediaALL DICOMINFORMATION OBJECTSDICOM File FormatISO 9660 UDFFAT 16 FSISO 9660Level 1DOSDOS130 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/+RWCD-ROMCD-RUSBMediaDICOM Relies on Broadly Available Media Storage Technology32
- 64. Uses of DIOCM33
- 65. Feedback and Query ???34
- 66. “Save Paper, Save Earth, Save US”Thank you !!!Email : gunjannpatel@gmail.comwww.bmeportal.ning.com35
- 67. ReferancesDICOM Cook Book -for Implementations in ModalitiesDigital Imaging and Communication in Medicine (DICOM)- OS Priyankhhttp://www.mediacy.com/index.aspx?page=IQDICOM_Servicehttp://medical.nema.org/36
Editor's Notes
- #24: grows to become either (Little Endian): F E D C B A 9 8 7 6 5 4 3 2 1 0 0000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 43 21or (Big Endian) F E D C B A 9 8 7 6 5 4 3 2 1 0 0000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 21 43