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Massachusetts General Hospital APIII 2007 Harvard Medical School
Evaluation ofDICOM Supplement 122
at CWRU
Ashok Patel Rajnish Gupta John Gilbertson
Case Western Reserve University
Cleveland, Ohio
Massachusetts General Hospital APIII 2007 Harvard Medical School
CT Scanner
Archive
RIS
Dedicated Workstation
Radiology had a problem 1980s
CT Scanner
Archive
Dedicated Workstation
Massachusetts General Hospital APIII 2007 Harvard Medical School
Massachusetts General Hospital APIII 2007 Harvard Medical School
Massachusetts General Hospital APIII 2007 Harvard Medical School
Image Exchange Standard
CT Scanner
Archive
RIS
Dedicated Workstation
Two Important Inventions
CT Scanner
Archive
Dedicated Workstation
PACS
Massachusetts General Hospital APIII 2007 Harvard Medical School
DICOM – an Image Exchange Standard:
• 1985: ACR (American College of Radiology) and NEMA (National Electrical Manufactures Association) published the first ACR-NEMA standard for radiology
• 1993: DICOM Digital Image COmmunications in Medicine
CT Scanner
PACS
RIS
Workstation
Vendor 2Vendor 1
Vendor 4Vendor 3
DICOM
Massachusetts General Hospital APIII 2007 Harvard Medical School
DICOM
• A remarkably successful standard Is the basis for virtually all PACS and multi-specialty Clinical Image Archives…
• Very large client community
• Very strong vendor community
• Over time, it has been responsive to technical and practice changes
• It managed by NEMA through open, collaborative, international working groups
• Working Groups maintain and extend different parts of the standard
Massachusetts General Hospital APIII 2007 Harvard Medical School
Device(Archive)
Internal InformationModel and Protocols
Device(CT Scan)
Internal InformationModel and Protocols
“CT Working Group”
CT ScanInformation Object
Definition (IOD)
Defined
DICOM Protocol / Service “Store”
Working groups from different specialties can define IODs as needed…
Criminally Simplified DICOM
DICOM InformationModel and Protocols
DICOM InformationModel and Protocols
Transaction
Convert Convert
Image
Type: CTPatient IDStudy IDMachine IDDateSizeRadiologistEtc.
ImageObject
Image & standardized clinical data and metadataDifferent for each image object class
Multiple Modules
Made up of
Massachusetts General Hospital APIII 2007 Harvard Medical School
Pathology, DICOM and WG 26
• It was designed to be used by other (non-radiology) specialties and many have done so
• Initial work between Pathology and DICOM in the middle nineties
• October 2005: DICOM Strategic Planning Working Group (WG 11) invited a number of pathologist to Budapest to discuss the possibility a Pathology Working Group in DICOM
• December 2005: DICOM WG 6 established WG 26, with scope over all of pathology imaging
Massachusetts General Hospital APIII 2007 Harvard Medical School
LIS / HistologyBar coded
Slides
WSI Robot
ImageArchive / Server
“Virtual Microscope”On Pathologist’s PC
WSI Robot
ImageArchive / Server
“Virtual Microscope”On Pathologist’s PC
Pathology has a problem…
Massachusetts General Hospital APIII 2007 Harvard Medical School
WG 26
• It is made up of pathologists, the WSI industry and senior members of DICOM who act as mentors
• Anyone can join, show up (and work)
• Seven formal meetings - Phoenix January 06, Madrid, Vancouver, Chicago, DC., Cologne, Pittsburgh (plus conference calls)
Massachusetts General Hospital APIII 2007 Harvard Medical School
WG 26
• Major “initial findings””
– Most of DICOM could be used directly in Pathology, but
– for DICOM to work in Pathology, three main issues had to be solved…
Massachusetts General Hospital APIII 2007 Harvard Medical School
• Two of the three issues:
– “Sub image access”
– “Image size”
Are outside the scope of this study
• Members of WG 26 are working with other parts of the DICOM community to solve these problems
Image Server
Image Client
Entire Image
Current View
He’s panning to the left!
Here are the appropriate tiles
“Sub-image level access”
Massachusetts General Hospital APIII 2007 Harvard Medical School
Specimens
Massachusetts General Hospital APIII 2007 Harvard Medical School
Specimens in DICOM
• DICOM expects a Patient to be the subject of every image
• In pathology a Specimen is the subject of an image
• WG 26 has offered for public comment DICOM Supplement 122 which defines the place of a specimen in the DICOM information model as well as the specimen attributes that should be collected when a specimen is the subject of a DICOM image
Patient
Study
Series
Image
Bas
ic D
ICO
M
Hie
rarc
hy
Very Simplified DICOM
Specimen?
Massachusetts General Hospital APIII 2007 Harvard Medical School
WG 26: Specimens in the DICOM Model
Patient
Study
Series
Image
Criminally Simplified DICOM
Modality
Specimen
LIS
SpecimenInformation Object
Definition (IOD)
Pathology ModalityInformation ObjectsDefinitions? (IOD)
Second draft this summer
“Specimen” can be associated with any type of image
Relevant SpecimenIdentification and Processing data (expected to come from the LIS)
Massachusetts General Hospital APIII 2007 Harvard Medical School
Supplement 122: Specimen Attributes
SS.3.1 Scope• The Specimen Module (see PS3.3) defines formal DICOM attributes for the
identification and description of laboratory specimens when said specimens are the subject of a DICOM image. The Module is focused on the specimen and laboratory attributes necessary to understand and interpret the image. These include:
– Attributes that identify (specify) the specimen (within a given institution and across institutions).
– Attributes that identify and describe the container in which the specimen resides. Containers are intimately associated with specimens in laboratory processes, often “carry” a specimen’s identity, and sometimes are intimately part of the imaging process, as when a glass slide and cover slip are in the optical path in microscope imaging.
– Attributes that describe specimen collection, sampling and processing. Knowing how a specimen was collected, sampled, processed and stained is vital in interpreting an image of a specimen. One can make a strong case that those laboratory steps are part of the imaging process.
– Attributes that describe the specimen or its ancestors (see Section SS.1, above) when these descriptions help with the interpretation of the image.
• Attributes that convey diagnostic opinions or interpretations are not within the scope of the Specimen Module. The DICOM Specimen Module does not seek to replace or mirror the pathologist’s report.
Massachusetts General Hospital APIII 2007 Harvard Medical School
Device(Archive)
Internal InformationModel and Protocols
Device(WSI)
Internal InformationModel and Protocols
Working Group 26
Information ObjectDefinition (IOD)
Defined
DICOM Protocol / Service “Store”
Working groups from different specialties can define IODs as needed…
Very Simplified DICOM
DICOM InformationModel and Protocols
DICOM InformationModel and Protocols
Transaction
Convert Convert
Image
Type: CTPatient IDStudy IDMachine IDDateSizeRadiologistEtc.
ImageObject
Image & standardized clinical data and metadataDifferent for each image object class
Multiple Modules
Made up of
SpecimenModule
SPECIMEN ATTRIBUTES IN DICOM: SUPPLEMENT 122
Massachusetts General Hospital APIII 2007 Harvard Medical School
Table A.32.X-1SPECIMEN VL MICROSCOPIC IMAGE IOD MODULES
IEModule Reference Usage
Patient Patient C.7.1.1 M
Clinical Trial Subject C.7.1.3 U
Study General Study C.7.2.1 M
Patient Study C.7.2.2 U
Clinical Trial Study C.7.2.3 U
Series General Series C.7.3.1 M
Clinical Trial Series C.7.3.2 U
Equipment General Equipment C.7.5.1 M
Image General Image C.7.6.1 M
Image Pixel C.7.6.3 M
Acquisition Context C.7.6.14 M
VL Image C.8.12.1 M
Overlay Plane C.9.2 U
Specimen C.7.6.20 M
SOP Common C.12.1 M
Specimen Module areDefined in a document, Written by a working group,Called a Supplement
Massachusetts General Hospital APIII 2007 Harvard Medical School
Specimens in DICOM
• Supplement 122 asks for the following data elements:
1. Specimen Container Identifier
2. Container Identifier
3. Specimen Identifier
4. Short Description of the Specimen (Text)
5. Detailed Description of the Specimen (Text)
6. Coded Description of the Specimen
1. (code | code system | code meaning)
7. Processing History especially fixation, embedding and staining
1. Specimen ID of Specimen Processed
2. Date Time of Processing
3. Type of Processing
4. Description of Processing
Massachusetts General Hospital APIII 2007 Harvard Medical School
The study
• After the DICOM Supplement 122 became available for public comment, investigators at Case Western Reserve University attempted to implement the supplement in their LIS to determine if the LIS could provide the specimen attributes requested in Sup. 122 and if there was important LIS data that the Supplement should request but does not
• Essentially we tried to write an LIS (Cerner Copath) query/report that could retrieve the proposed DICOM specimen data on Gross Specimens and Slides
• Looked at 5000 cases (~ 30000 gross specimens and slides)
Massachusetts General Hospital APIII 2007 Harvard Medical School
Specimen ID
• Part and Block identifiers were not problem
• A unique slide identifier could be constructed, but it required joining two tables. The result was a x.x slide number
• S05-100 A 1 2.3
• A05-100 A 1 2.5
• A05-100 A 1 3.1
Massachusetts General Hospital APIII 2007 Harvard Medical School
Specimen Description
• Pathologists descriptions of parts and blocks were “hidden” in large, multi-specimen narrative field that required extensive parsing
• This was a serious problem – the “native” LIS could not reliably provide specimen descriptions
• Coded specimen descriptions (part types, etc) were available but were often non-specific and non-descriptive (‘Big – Other”)
Massachusetts General Hospital APIII 2007 Harvard Medical School
Specimen Processing
• How was it fixed? FIXATION and STAINING are from the same dictionary
• How was it Embedded? NO DATA
• How was it Stained? FIXATION and STAINING are from the same dictionary
• An slide stained in H&E and fixed in B5 was reported as “stain = B5”
• There were multiple ‘types” of H&E processes depending on when the staining was done: HE Initial, HE, etc.
Massachusetts General Hospital APIII 2007 Harvard Medical School
Conclusions
• Our LIS could not implement SUP 122 without major changes
• This is not about DICOM, this is about our LIS systems
• The study showed serious limitations in the information model and implementation of our LIS when it comes to specimen level information
• Narrative field that contain data on multiple specimens (parts and blocks) are serious problems
• Histology data is not stored in sufficient detail
• Dictionaries are poorly implemented