Pathology in DICOM – Progress from Working Group 26 and IHE

1. Pathology in DICOM – Progress from Working Group 26 and IHE Bruce BECKWITH(1), Christel Daniel LE BOZEC(2), Marcial GARCIA-ROJO(3), John GILBERTSON(4), Harry SOLOMON (5) 1) Department of Pathology, North Shore Medical Center, Salem, MA. 2) INSERM UMRS 872, Université René Descartes Paris, France. 3) Department of Pathology, Hospital General de Ciudad Real, Spain. 4) Department of Pathology, Massachusetts General Hospital, Boston, MA. 5) GE Healthcare Integrated IT Solutions, Barrington, IL, USA Presenter: Marcial García Rojo

2. Before Now Pathology • Pathology (understanding the basis of the disease) is a visually rich medical specialty • Led by Radiology it is quickly moving toward extensive use of digital images. • Important differences between the imaging processes in the two specialties. • Adapt current DICOM standard to accommodate unique aspects of imaging in Pathology.

3. Pathology Images • Gross images: • biopsies, surgical specimens, autopsy. Videos. • Microscopic images: • Histological sections (biopsies, cell blocks, autopsies). Staining and special techniques. • Cytology, dispersions. • Molecular Pathology: • FISH, CISH, SISH (microscopy). • Agarose gels. • Sequencing.

4. DICOM Service Consistent Presentation Print Acquired Display

5. Medical images web service

6. Tools in image viewer

7. Original Image & Presentation State Area Of Interest Area Of Interest The Pathologist’s Transformations Are Saved Original Image The Pathologist’s Transformations Are Lost Image Consistent Presentation What the Pathologist sees: What the Reviewing Physician Sees: Annotate Annotate Prepared Image Zoom Flip Window Level Original Image Original Image

8. DICOM and Pathology • Specific DICOM objects (“Information Object Definitions”) are defined for Pathology • Modification and/or extension are necessary for two main reasons: • DICOM model did not provide a strong mechanism for describing the specimen being imaged or associating a particular specimen with a particular image. • Some pathology-related image formats (whole-slide images, multispectral images, flow cytometry, etc) do not have applicable DICOM Information Object Definitions.

9. Working Group 26 • It was established in September 2005 with the two immediate aims: • Update and extend the data model used to describe pathologic specimens which are the subject of imaging procedures. • Create a mechanism to store, retrieve and view microscope whole slide images within the DICOM framework.

10. WG26. Participants • Representatives from pathology professional societies in Europe, Japan and the US. • Liaison with the HL7 Anatomic Pathology, IHE-pathology and Laboratory Special Interest Groups (e.g. European COST IC0604).

11. DICOM Supplement 122 • Defines a specimen data model to accommodate a wide variety of relevant information needed to interpret pathology images: • type of specimen, • procedure used to obtain specimen, • physical and chemical processing, • sampling and sub-sampling methods, etc.

12. Unifying concepts • An important part of the Supplement is establishing uniform definitions for the major concepts. • Specimen is defined as a physical object considered by the laboratory as a single discrete, uniquely identified unit that is the subject of one or more steps in the diagnostic workflow. • Objects at all levels of processing (from fresh tissue to sections made from embedded tissue, or dispersions). • Container: Where specimens (1 or multiple) are physically placed. • Buckets, cassettes, vials, and slides.

13. DICOM Model for Specimens

14. Compatibility • The Supplement also addresses compatibility between the new Specimen Module and the Specimen Identification Module currently defined in the standard • The decision was: To retire the old DICOM specimen identification module

15. Whole Slide Imaging • Unique challenges: • In terms of size (they may contain billions or even trillions of pixels) • Over 1 GB compressed file / slide. • Access functionality • Mimic the experience of viewing a physical microscope slide.

16. Viewing large images • Sending small subsets of the image data in response to interactive user commands. • Proposed solution for incorporating these whole slide images into the DICOM standard in a manner that will enable interoperability and support rapid and dynamic viewing.

17. Universidades de Tampere y Helsinki

18. Universidades de Tampere y Helsinki

19. Revised specimen module • Supplement 122 provides for “Specimen Module and Revised Pathology SOP Classes.” • While DICOM Supplement 15 added the concept of specimens, the location of specimens in the DICOM information model had not been explicitly stated, and current specimen identification is at the Patient level. • New Specimen Module at the level of the Image. • Specimen that forms the immediate subject of the image is identified, together with critical specimen information, such as description, specimen ancestry and processing, necessary to interpret the image.

20. Required changes in DICOM • The Specimen Module has been harmonized with the HL7 v2 SPM segment and the HL7 v3 draft Specimen Domain Information Model. • Existing Accession Number at the study level may be reused. • No changes to the information or real world models in DICOM are required . • An extension of the DICOM information model for specimen-related information is provided. • Old Specimen Identification Module is retired from all IODs. Does it affect existing implementations? Probably not, since there were few, if any, actual implementations that used the old specimen identification module. Minimal problems expected.

21. Modalities • Modalities Worklist • Modalities must obtain the specimen identificationand include it in the acquired images. • Pathology information system provides the attributes of the Specimen Module for each specimen being imaged (IHE profile). • In radiology, the imaging subject is the patient; in pathology, the imaging subject is the specimen derived from the patient. • Modality Performed Procedure Step • Laboratory Information System can obtain the list of images created for each specimen (IHE Profile).

22. Virtual Slides in DICOM • “As PACS vendor we see the WSI as one of the major adventures of the next years.” • “For Pathology it is of great importance that images sent from the scanner are already formatted for efficient distribution out of the PACS.” • “A Pathology PACS will have to manage the "through-streaming" of the scanner device to the viewing clients.” (Ralf Zwönitzer. August, 2006. WG26 mailing list)

23. Advantages of DICOM in Pathology • Organization: Central repository of medical images for all medical specialties: PACS. • Integration with e-Health Record. • One viewer for all medical images. • Independence of • devices manufacturers. • proprietary file formats.

24. Standards: IHE. Actors & Transactions

25. An example of DICOM implementation in Pathology

26. Conclusions • Digital images and virtual slides are already being commonly used in Pathology, mainly for second opinion and continuing education. • Virtual slides are a important challenge to existing standards. • DICOM standard in Pathology is needed for interoperability and long term solutions. • PACS should be able to manage over 50 TB per year. • JPEG 2000 (JPIP) has been considered as an alternative by some groups.