dicomrt
TRANSCRIPT
DICOM Radiotherapy
Andrew J Reilly
Imaging PhysicistOncology PhysicsEdinburgh Cancer CentreWestern General HospitalEDINBURGH EH4 2XU
Phone: 0131 537 1161Fax: 0131 537 1092E-Mail: [email protected]
Overview• The DICOM standard• DICOM in Radiotherapy – DICOM-RT• DICOM Conformance• Advantages / Disadvantages• Anatomy of a DICOM file• DICOM in Edinburgh Cancer Centre• Useful DICOM tools• Practical examples of addressing DICOM issues
The DICOM Standard• DICOM 3.0
• Digital Imaging and COmmunications in Medicine• Successor to ACR-NEMA standards (1985,1988)• NEMA standard – voluntarily adhered to• Covers digital images and associated data
• CT, MR, PET, U/S• Radiotherapy data, RIS, HIS, patient reports, etc.
• Constantly evolving• Concurrently developed by multiple working groups• New version released approx every 2 months• Direction consolidated annually
Scope of DICOM• Standard divided into 16 parts• Standard data structures and services
• The DICOM ‘Data Dictionary’
• Transfer of data across a network• Negotiation of transfer protocol• Checks to ensure sender / receiver support same features
• Storage onto media• Physical specifications and formatting of storage media• Format of data on storage media (i.e. file format)
• Compatibility between systems – ‘Conformance’• Data compression• Security
• Encryption, digital signatures, audit trails
• Consistent standard for image display and output
DICOM Basics• Data Element
• Unit of information, with defined data type and structure• Standard elements are uniquely indexed by ‘tag’ and name• e.g. patient name, CT slice position, gantry angle
• Information Object• Set of elements which together describe a physical entity – like a document• e.g. CT scan, Radiotherapy Plan
• Service Class• Action which can be performed on information objects• e.g. transferring data between systems, archiving to media, printing
• Service Object Pair (SOP)• A defined action which can be performed on a particular object• e.g. CT image can be printed
DICOM-RT (1)• Radiotherapy extensions developed by RT working group (WG7)• Part of DICOM 3.0 standard since 1997• Most commonly encountered extensions:
• RT Structure Set• Patient-related structures• Outlined target volumes, organs at risk
• RT Plan• Geometric and dosimetric data relating to treatment plan• External Beam: treatment unit, isocentre, gantry/couch/collimator angles,
collimation• Provision for brachytherapy
• RT Image• Images relevant to RT acquired using conical geometry• Generated images: DRR, DCR, BEV, etc.• Other RT images: Simulator, portal images, etc.
DICOM-RT (2)• Other extensions, also part of DICOM 3.0
• RT Dose• Dose distributions calculated by planning system• 2D / 3D dose matrix and groups of point doses• Isodose curves• Dose-volume histograms (DVHs)
• RT Treatment Records• Treatment session data for external beam and brachytherapy• + summary of overall treatment
• Under development• RT worklist / workflow• RT dose calculation service
DICOM Conformance• ‘DICOM conformance’
• Minimum level of implementation is required• Additional compliance described by ‘conformance statement’
• ‘Conformance Statement’• Specifies supported information objects, service classes, SOPs,
communication protocols and storage protocols• Describes ‘private’ additional objects/classes which are vendor-
specific. Two systems implementing the same SOP classes should, for that application only, be compatible
• e.g CT image storage: 1.2.840.10008.5.1.4.1.1.2
• No guarantee that conforming systems will process incoming data in the same way
• How to guarantee compatibility?
DICOM Advantages• Widely accepted Standard format
• Should improve compatibility between applications and equipment supplied by different vendors
• Standard objects / services / protocols are well defined• Additional information stored with image data
• Patient demographics• Application parameters, geometrical information
• Robust, reliable format• In any given system, all images / structures / plans are
uniquely identifiable• Persistency of data• Technology on which standard is based is tried and tested
DICOM Disadvantages• Conformance does not guarantee compatibility
• May be difficult to determine whether two products are truly compatible
• Different systems may implement same features in different ways
• Complex standard and very broad scope• May be difficult to interpret standard requirements• Multiple elements with essentially same purpose
• e.g. CT image, RT image, MR image, etc.
• Use of private, proprietary elements
• Internal format may not be DICOM• May require complex local configuration
• Some vendor’s systems are more strict than others
Anatomy of DICOM File
Data Element n
…
Data Element 2
Data Element 1
Prefix (“DICM”)
Preamble (128 bytes)
Joe Bloggs10PN(0010,0010)
ValueValueLength
Value Representation
Tag
•Representation of patient name element•Physical encoding depends upon specified transfer / storage format.
Describes format and max length of value.OPTIONAL: May be implied by tag
Radiotherapy Example
Slices fromCT Scan(CT Image)
Target volumeand organsat risk(RT Struct)
Radiotherapy Example (2)RT Struct
Beam specifications(RT Plan)
DRRs(RT Image)
CT ScanTag Attribute Name VR Value
(0002,0013) ImplementationVersionName SH OFFIS_DCMTK_352
(0008,0008) ImageType CS ORIGINAL\PRIMARY\AXIAL
(0008,0016) SOPClassUID UI 1.2.840.10008.5.1.4.1.1.2
(0008,0018) SOPInstanceUID UI 1.2.840.113619.2.22.287.35138.2431.3.19.20031117.200530
(0008,0020) StudyDate DA 20031117
(0008,0032) AcquisitionTime TM 100450.674
(0008,0060) Modality CS CT
(0008,0070) Manufacturer LO GE MEDICAL SYSTEMS
(0008,0080) InstitutionName LO EDINBURGH CANCER CENTRE
(0018,0022) ScanOptions CS HELICAL MODE
(0018,0050) SliceThickness DS 5.0
(0018,5100) PatientPosition CS HFS
(0019,0010) Proprietary Tag LO GEMS_ACQU_01
(0020,0032) ImagePositionPatient DS -250.0\-250.0\25.0
(0020,0037) ImageOrientationPatient DS 1.0\0.0\0.0\0.0\1.0\0.0
(0020,1041) SliceLocation DS 25.0
(0027,0010) Proprietary Tag LO GEMS_IMAG_01
(0028,0030) PixelSpacing DS 0.9765625\0.9765625
(0028,0100) BitsAllocated US 16
(0028,0101) BitsStored US 16
(0028,1050) WindowCenter DS 20.0
(0028,1051) WindowWidth DS 350.0
(0028,1052) RescaleIntercept DS 0.0
(0028,1053) RescaleSlope DS 1.0
(7FE0,0010) PixelData OW|OB 24\ff\24\ff\24\ff\24\ff\24\ff\24\ff...
Unique identifier
Geometricalrelationshipto patient
CT image store
RT Structure Set
Repeated for each CT slice and structure
Tag Attribute Name VR Value (0008,0018) SOPInstanceUID UI 1.2.840.113619.2.832162544279.12377.1069165019.472
(0008,0060) Modality CS RTSTRUCT
(0008,103E) SeriesDescription LO Adv Sim RT Structure Sets
(0008,1090) ManufacturerModelName LO Advantage Sim
(0018,1000) DeviceSerialNumber LO 80e5ce97
(0018,1020) SoftwareVersion LO 5.0.13
(3006,0004) StructureSetName LO prostate
(3006,0008) StructureSetDate DA 20031118
(3006,0009) StructureSetTime TM 144014.000
>ITEM 1 null null null
>(3006,0084) ReferencedROINumber IS 5
>(3006,002A) ROIDisplayColor IS 135\206\235
>>(3006,0016) ContourImageSequence SQ null
>>>(0008,1155) ReferencedSOPInstanceUID UI 1.2.840.113619.2.22.287.35138.2431.3.19.20031117.200530
>>(3006,0042) ContourGeometricType CS CLOSED_PLANAR
>>(3006,0044) ContourSlabThickness DS 5.0
>>(3006,0046) NumberOfContourPoints IS 73
>>(3006,0050) ContourData DS 12.207\-65.918\25.156\13.184\-64.941\25.156\19.043\-64.941\25.156\20.02\-65.918\25.156\…
>(3006,0084) ReferencedROINumber IS 5
>(3006,0085) ROIObservationLabel SH rt_fh
>(3006,00A4) RTROIInterpretedType CS ORGAN
RT PlanTag Attribute Name VR Value
(0008,0060) Modality CS RTPLAN
(300A,0002) RTPlanLabel SH final_beams
(300A,0006) RTPlanDate DA 20031119
>(300A,00B2) TreatmentMachineName SH la4;1
>(300A,00B4) Source-AxisDistance DS 1000.0
>>(300A,00B8) RTBeamLimitingDeviceType CS MLCX
>>(300A,00BC) NumberOfLeafJawPairs IS 60
>>(300A,00BE) LeafPositionBoundaries DS -200.0\-190.0\-180.0\-170.0\-160.0\-150.0\-140.0\-130.0\-120.0\-110.0\-100.0…
>>(300A,00B8) RTBeamLimitingDeviceType CS ASYMY
>>(300A,00BC) NumberOfLeafJawPairs IS 1
>(300A,00C0) BeamNumber IS 1
>(300A,00C2) BeamName LO 1ant
>(300A,00C4) BeamType CS STATIC
>(300A,00C6) RadiationType CS PHOTON
>(300A,00CE) TreatmentDeliveryType CS TREATMENT
>(300A,00D0) NumberOfWedges IS 0
>(300A,00E0) NumberOfCompensators IS 0
>(300A,00ED) NumberOfBoli IS 0
>(300A,00F0) NumberOfBlocks IS 0
>(300A,010E) FinalCumulativeMetersetWeight DS 100.0
>(0008,1150) ReferencedSOPClassUID UI 1.2.840.10008.5.1.4.1.1.481.3
>(0008,1155) ReferencedSOPInstanceUID UI 1.2.840.113619.2.832162544279.12377.1069165019.472
Referenced structure set
DICOM in Edinburgh Cancer Centre1. Conventional External Beam
GE AdvantageSim
CT Scanner
GE AdvantageWindows
GE AdvantageFusion
MR Scanners
Other sources
Varian Eclipse
Varian VARiS/Vision
Cadplan
TreatmentUnit
DICOM Archives
DICOM link
Other link
DICOM in Edinburgh Cancer Centre2. Stereotactic Radiotherapy
CT Scanner
MR Scanner
In-HouseFusion Package XKnife TPS
VarianVARiS / Vision
TreatmentUnit
DICOM Archives
DICOM in Edinburgh Cancer Centre3. Brachytherapy
UltrasoundScanner
ScreenGrabber
NucletronPlato TPS
DICOM Archive
DICOM Issues• What to do when DICOM issues arise?• Definition of “Issue”
• Incompatibility between systems• Configuration problem• Unexpected results• Proposed development of service
• If problem for manufacturer, some preliminary local work can help aid in solution
• May be able to address issues locally
DICOM Tools (1)
• Many DICOM utilities are freely available• May enable local diagnosis and resolution of
problems• Types of utility
• DICOM image viewers• DICOM file editors• DICOM client/server applications
• Useful website: http://www.idoimaging.com
DICOM Tools (2)• ImageJ
• Robust viewer for almost all DICOM images• Java programming interface which can be extended• http://rsb.info.nih.gov/ij/
• Tiani JDicom• Server applications, including print server• Java – runs on all platforms• User-friendly graphical user interface• EditDicomObject program especially useful – allows direct
examination and editing of DICOM files• http://www.tiani.com/JDicom/ (Case sensitive!)
DICOM Tools (4)• OFFIS DICOM Toolkit
• Server applications• DICOM to bitmap conversion tools• http://dicom.offis.de/index.php.en
• Mallinckrodt Institute of Radiology Tools• Server applications / conversion programs, etc• Stores data to relational database• Provides query/retrieve facility so that database can be used
as archive• Used to provide archive servers in ECC• http://wuerlim.wustl.edu/DICOM/
DICOM Tools (5)• Conquest DICOM
• Server, viewer and conversion tools• Builds database which can queried / retrieved from• Microsoft Windows interface• http://www.xs4all.nl/~ingenium/dicom.html
• ITC DICOMpiler• Received DICOM communications over the network• Converts patient demographics to anonymous study IDs
suitable for use in clinical trials• Stores studies to CD in DICOM standard format• Microsoft Windows interface• http://rtog3dqa.wustl.edu/DICOMpiler/
DICOM Tools (6)
• MyDICOM Software Development Kit• Comprehensive C# .NET toolkit for processing
DICOM files• Allows access to DICOM objects at the lowest level• Allows addition of elements, as well as modification
of those already present• Very useful when all else fails!• http://www.thecriswells.net/MyDICOM/
Practical Examples1. Problems transferring RT Plan data between GE
Advantage Sim and Varian SomaVision / Eclipse
2. Problems interpreting data from multi-centre study
3. DICOM print server for CT scanner
Example 1: Problems sending RT Plans from AdvSim -> SomaVision & Eclipse• The problem:
• Outlining and addition of initial beams performed in Advantage Sim
• Transfer protocol established and tested from AdvSim -> SomaVision
• X and Y jaw positions transferred OK• X MLC data transferred OK (Varian 2100CD linac)
• When commissioning Eclipse, no X jaw position was transferred
• What happened to the X jaws?
AdvSim DICOM File• DICOM file sent to Linux workstation using OFFIS
DICOM and examined using JDicom’s EditDicomObject
• No X jaw positions were present• SomaVision automatically inserts X jaw positions,
whilst Eclipse does not• Conformance to same SOP but different outcome
>(300A,00B2) TreatmentMachineName SH la4;1
>(300A,00B4) Source-AxisDistance DS 1000.0
>>(300A,00B8) RTBeamLimitingDeviceType CS MLCX
>>(300A,00BC) NumberOfLeafJawPairs IS 60
>>(300A,00BE) LeafPositionBoundaries DS -200.0\-190.0\-180.0\-170.0\-160.0\-150.0\-140.0\-130.0\-120.0\-110.0\-100.0…
>>(300A,00B8) RTBeamLimitingDeviceType CS ASYMY
>>(300A,00BC) NumberOfLeafJawPairs IS 1
>(300A,00C0) BeamNumber IS 1
Example 2: Problem with Multi-centre Study Dataset
• Special software for analysing CT scans + RT structure sets and plans
• CD-ROMs received containing scans, structures and plans for ~50 patients
• Problem interpreting Patient ID number created when patients were anonymised
• Simple to fix using EditDicomObject, but >300 files to process!
• Corrected problem using MyDICOM• Fast and efficient solution
Example 3: DICOM Print Server for CT Scanner
• CT scanner only outputs hard copies to DICOM devices• Provided print facility was to Kodak DryView laser
imager, via dedicated mini PACS system.• System not ideal
• Expensive• Light box required to view films• Large films difficult to store in patient notes
• Solution• Use OFFIS DICOM and JDicom’s PrintServer to allow
printing directly to colour laser printers
Conclusions• DICOM is a wide-ranging, continually evolving NEMA Standard
for communication of medical images and related information, including RT structure sets, plans and images.
• Likely that new RT specific information objects and services will become widespread in the future
• “Standard” does not guarantee compatibility between systems. Compatibility depends upon:• mutual conformance, and• proprietary processing of data once received.
• With available tools, many problems can be diagnosed or overcome locally
• Available toolkits can be used to develop service