Massachusetts General Hospital APIII 2007Harvard Medical School Evaluation of DICOM Supplement 122 at CWRU Ashok PatelRajnish GuptaJohn Gilbertson Case

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


CT Scanner

Archive

RIS

Dedicated Workstation

Radiology had a problem 1980s

CT Scanner

Archive





Image Exchange Standard

CT Scanner

Archive

RIS


Two Important Inventions

CT Scanner

Archive


PACS


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


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


Device(Archive)

Internal InformationModel and Protocols

Device(CT Scan)


“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


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


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


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…


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)


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…


• 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”


Specimens


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?


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)


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.


Device(Archive)


Device(WSI)


Working Group 26

Information ObjectDefinition (IOD)

Defined

DICOM Protocol / Service “Store”

Working groups from different specialties can define IODs as needed…

Very Simplified DICOM



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


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


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


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)


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


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”)


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.


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

Documents

Massachusetts General Hospital APIII 2007Harvard Medical School Evaluation of DICOM Supplement 122 at CWRU Ashok PatelRajnish GuptaJohn Gilbertson Case