Bruce Beckwith, MD

Scanner

• Tissue (Surgical) Pathology
– Tissue from biopsies, resections & autopsies
• Cytology
– Individual cells from smears/scrapings or fluids
• Clinical laboratory
– Blood smears, protein electrophoresis, etc.

• Pathology workflow starts with a specimen
• Dissection
• Chemical processing
• Cut thin sections and place on glass slides
• Stain with a variety of techniques
– Chemical
– Immunochemical
– in-situ hybridization

• Location independence
• Sharing of images with clinicians
• Enables new analysis techniques
– Computerized screening of pap smears
– Image analysis for quantitation of special stains
– ? Computer aided diagnosis for other specimens

Radiology
• Digital acquisition
• Manageable file size
• Many clinician interpretable
• Cost savings compared to analog
• Computer aided detection for mammograms
Pathology
• Mainly analog data which is digitized
• Very large file size in pathology
• Some clinician interpretable
• Incremental costs in addition to analog
• Computer assisted screening for pap smears

1 focal plane
24 bit color
40x magnification
15 Gigabytes
10 focal planes
24 bit color
40x magnification
3.75 Terabytes

• Main challenge is rapid pan, zoom, focus, advancing to next slide
• Intuitive “driving” of the slide will help transition
• Some equipment is trying to recreate microscope “feel”

• D igital I maging and Co mmunications in
M edicine
• Voluntary standards organization
• Image exchange standard for CLINICAL images
• 27 working groups
• Anyone with a material interest may participate
• Version 3 of standard released 1992

• Communication standard
• High level standard, conceptual
• Facilitates interchange, doesn’t mandate internal storage formats within PACS
• Image object definitions are central
• Widely adopted in radiology
• Addresses workflow as well as images

• Visible light supplement approved 1999
– Incomplete and rarely used
– Doesn’t support the complexity of Pathology practice
• Pathology WG needed
– Created WG-26 Fall 2005
– Has met about 20 times
– Representatives from most major pathology imaging vendors
– Also pathologists, consultants and researchers
– 90+ subscribers to email listserve
• 60+ organizations
• >10 countries

• Initial goals:
– Extend minimal capabilities to describe specimens in
DICOM
– Create a mechanism to allow exchange and use of whole slide microscopic images within DICOM
• Long term goals:
– Other imaging modalities, such as multi-spectral images, electron microscopy, flow cytometry, clinical lab images

• Specifies a specimen description model which allows description of:
– Type of specimen
– Procurement and processing steps
– Sampling methods
– Physical attributes of slides
• Final text approved June 2008

Equipment
Modality
1
Patient
1
1 n
Has
Study
1
Is source of n
Base Std
Creates n
Contains n
Series
1 Supp 122
Component
Base, Coverslip n
Has
1 n
Image
1
Is acquired on
1
Container
Box, Block, Slide, etc.
1
Contains n
Specimen
Physical object n
Is child of
1
1
Has n
Preparation
Step
Collect, Sample,
Stain, Process

• Supp 122 has the needed data elements,
BUT most AP LIS Systems don’t have these data at the SPECIMEN level, if at all
– Unique slide ID may not be explicitly present
– No ability to identify subregions of a slide/block
– Staining and fixation information often co-mingled
– Specimen descriptions difficult to parse out from large text blocks
– Dictionaries may be poorly implemented

• Need a new DICOM Image Object Definition
• Challenges
– Vast size
– Need for intuitive and fast viewing interface
• DICOM specific issues
– Image pixel dimensions limited to 64k x 64k
– Image size description limited to 4GB
– Desirable to be backwards compatible
– Efficient sub-region access
– Most DICOM services assume entire image transmission

• Whole Slide Image divided into tiles
• Each tile encoded into a frame of multi-frame image object
• Per-frame header gives spatial location for each tile: X, Y, and Z (focal plane)
Multi-frame image object
Fixed Header Per-frame header
Dimension data Pixel data H Solomon GE

Thumbnail
Image
Intermediate
Image
Single frame image
Multi-frame image
(single object)
Multi-frame image
(single object) may include multiple
Z-planes, color planes
Baseline
Image
All image objects typically in 1 DICOM Series
H Solomon GE

• Thumbnail image (single frame) plus navigation links to each frame at each resolution
– Each tile of other resolution images has its corresponding area identified in thumbnail
• Full description of target tiles
– Object Unique ID and frame number
– Resolution
– Z-plane, color
• Multiple target frames can overlap
– Different resolution, Z-plane, color, etc.
• Presentation and any interactive behavior is not defined in standard
H Solomon GE

• Supplement approved August 2010
• DICOM is now able to handle most pathology and lab images
• Most slide scanner vendors have been involved, along with some PACS vendors
• Need to engage LIS vendors and publicize these changes

Pathology
Order &
Specimen info
Case info
Slide preparation Slide prep data
LIS /
APLIS
Slide ID
Scanning orders
Pathology
Workstation
Gross specimen accessioning
Surgical or biopsy procedure
Specimen
Images
Whole Slide
Scanner
Images w/ slide prep data
Images
PACS
Images – X-ray, U/S, optical, etc.
Adapted from H Solomon GE

• Currently some pathologists include snapshots in reports
– Tumors, specimen margins, unusual findings, etc
• WSI allows ability to review slides remotely with clinicians
• The ability to correlate slides with other images would be useful
– Gross specimen images
– Endoscopy images
– Radiology images

• Storage and bandwidth
– PACS storage is relatively expensive
– Don’t want to transfer entire huge files
• Pathology systems need to become more image centric (as opposed to report centric)
• EMR’s need to be able to accept or connect to images and display correctly
– Security, credentialing, optimized viewers, etc

• WG-26 has created supplements to incorporate modern digital pathology within DICOM
• The collaboration of DICOM, IHE and HL7 has led to a broad based standards effort for digital pathology
• The availability of a digital workflow for images will enable major changes in the practice of pathology
• DICOM support for radiology, pathology, surgery, and radiation therapy opens the door for true integration of data from these areas
26

• Members of DICOM WG-26
• Harry Solomon, mentor to WG-26
• IHE Anatomic Pathology WG
• HL7 Anatomic Pathology WG
• DICOM Website: http://medical.nema.org/