1. Introduction to DICOM Digital Imaging and Communication in Medicine
What is DICOM & why DICOM?
Hospital System Overview
Structure of the standard (IODs, Modules, SOP Class, attributes, data structures, …)
Consistent Image Presentation (Presentation States, Display Calibration …)
Structure of DICOM images (pixel representation, compression, …)
Conformance Statement
Data formats/medias and interpreting DICOM data sets
Security

2. What is DICOM?
The DICOM (Digital Imaging and Communications in Medicine) Standard is a set of rules that allows medical images and associated information to be exchanged between imaging equipment, computers, and hospitals. The standard establishes a common language that permits medical images and information produced on one vendor's machine to be available for use on the digital system of another vendor. interface which is used to transfer data in and out of an imaging device.

3. What is the DICOM Standard?
􀂙 World-wide medical imaging standard based on
“open systems networking” (TCP/IP)
􀂙 Thousands of “multi-vendor” network installations
via products such as:
􀂃 Modalities, Printers, Archives, Film Digitizers
􀂃 Teleradiology, Information Systems, Workstations,
Archives …..
􀂙 First released in 1993, with additional releases in
1996, 1998, 1999, 2000 ….
􀂙 DICOM is an international standard
Goal is to be “as close”
to plug and play as possible

4. Pointers to DICOM
The DICOM conformance statement comprises of 16 parts in 2008 standard
Part Introduction and Overview(explains what is contained in what & also explains the relationhsip)
Part Conformance
Part Information Object Definitions(masking information, required,optional or conditional)
Part Service Class Specifications (describes all dicom services and the exchanged information)
Part Data Structures & Encoding(specify value representation with the type eg: Standard format such as PN and DA )
Part Data Dictionary(list of individual attributes used to construct dicom objects)
Part Message Exchange (grammar of dicom language)
Part Network Communication Support for Message Exchange
Part 3.9 – Retired (point to point communication)
Part Media Storage and File Format for Data Interchange(10,11 & 12 deal with DICOM media exchange format)
Part Media Storage Application Profiles(specific application profiles such as cardiology,radiology,definition of specific subset of images & encoding possibilities to store these images)
Part Media Formats and Physical Media for Data Interchange
Part Grayscale Standard Display Function
Part Security Profiles
Part Content Mapping Resource(contains codes and templates)
Part Explanatory Information (How SOP Classes can be used in form of use cases, good for those who want to implement DICOM standard)
Part Web Access to DICOM Persistent Objects (WADO)(How DICOM objects can be accessed through standard internet means using web-friendly format such as JPEG)

5. DICOM for Layman
DICOM for Radiologists
Well. It saves your money. But how?
For example, the costly DICOM Printer system can be shared by multiple CT or MR or US or any imaging units manufactured by any vendor. If there  were no DICOM, you will need seperate Printer systems for each and every imaging unit ! DICOM will act as an universal standard between these  imaging equipments and the printer system.
The advantages you get:
    Reduce Cost in purchasing extra equipments.
    Reduce Difficulty of connecting equipments.
    Simplified Servicing.
    Since DICOM is an universal standard, you need not buy custom software for equipments from different Manufacturers.
    Better Patient management. You can process your patient's images using any DICOM compliant software that are readily       available!
    You can move your patient data readily to an DICOM compliant RIS / HIS software.
    The facility of connecting existing PACS to other information systems, particularly an RIS or HIS. The DICOM Work Groups have liaisons to the groups writing RIS and HIS interface standards and expect to work at harmonization with these efforts. 

6. Patient is registered and order is scheduled
Systems View
Patient is registered and order is scheduled
ADT / Orders
MWL
Pre - Acquisition
RIS
Acquisition
MODALITY
PACS
Reporting
Viewing WorkStation
Archive
Results Distribution 6

7. Patient exam is in progress and completed
Systems View
Patient exam is in progress and completed
Pre - Acquisition
MPPS
RIS
Acquisition
MODALITY
PACS
Reporting
Viewing Workstation
Archive
Results Distribution 7

8. Acquired images are stored in the Long Term Archive (LTA)
Systems View
Acquired images are stored in the Long Term Archive (LTA)
Pre - Acquisition
RIS
Acquisition
MODALITY
PACS
Reporting
Viewing Workstation
Archive
Results Distribution 8

9. Systems View Pre - Acquisition Acquisition Reporting
Images stored in the archive are routed to viewing workstation for diagnosis
Systems View
Pre - Acquisition
RIS
Acquisition
MODALITY
PACS
Reporting
Viewing Workstation
Archive
Results Distribution 9

10. Report is generated for the study after diagnosis
Systems View
Report is generated for the study after diagnosis
Pre - Acquisition
REPORTS
RIS
Acquisition
MODALITY
PACS
Reporting
Viewing Workstation
Archive
Results Distribution 10

11. Study with report is viewed offsite using web client
Systems View
Study with report is viewed offsite using web client
Pre - Acquisition
REPORTS
RIS
Acquisition
MODALITY
PACS
Reporting
Viewing Workstation
Archive
Results Distribution 11

12. Systems View Pre - Acquisition Acquisition Reporting
What happens when:
Systems View
Patient exam is complete
Report is generated for the study after diagnosis
Image data is diagnosed by the radiologist
Patient exam is in progress
Study with report is viewed offsite using web client
Patient is registered and order is scheduled
ADT/ORM Message
MWL
REPORTS
Pre - Acquisition
REPORTS
Messages are sent
ADT/ORM
MWL is
generated
MPPS
RIS
MPPS msg. sent to RIS and PACS
Acquisition
Dictated report is sent to RIS
Acquired images are stored to archive
MODALITY
PACS
Images are routed to Workstation (Client)
Reporting
Viewing Workstation UV
Archive
Reports are retrieved
Results Distribution
Image is retrieved 12

52. DICOM Image File Structure
DICOM image file consists of: 
             1. Header Information           2. Image Pixel data
  All the information about the image, patient, study, etc. are stored in the header. 

54. Dataset
In DICOM jargon, the entire DICOM image file is called a Dataset.
    A Dataset consists of:
1) Tag -  Uniquely identifies an information
A tag is a combination of Group No. And Element Number. For Example, In the tag (0010,0020): Group No. is 0010 and Element No. is 0020
          A Group No. Tells you about an entity.An Element No. Identifies the exact information in the group. For example, 
Group no tells you that the information is about PATIENT. Element No tells you that the information is about the PATIENT NAME.  Some Groups: (Group numbers are in Hexadecimal)
Group 2 : Contains File Meta information
Group 8 : General series info.
Group 10: Patient info.
Group 20 : General Study info.
Group 28 : Image info.
Group 7F : Image pixel data  
2) VR (Value Representation)- Tells you the data type of the value. It is an optional field.
3) VL - (Value Length) – Length of the value.
4) Value Field – Here is where the actual value is stored

55. In the figure above, you can see the data elements consisting of TAG, VR, Value Length and Value field  
Tag – An Hex value, that uniquely identifies an information
VR (Value Representation) – Optional field.
You can see VR only in an Explicit VR transfer syntax file. If the transfer syntax is Implicit VR, then VR field is empty.
VR is a 2-byte field. It denotes the data type of the value.
VL (Value Length) – Gives you the length in bytes of the following value.  

56. How do I Parse DICOM Header?
For Instance, how Patient name information is stored in an Explicit VR file?
4-Bytes | 2-bytes | 2-bytes | C bytes (in Hex) or 12 bytes PN OC
Sridhar Raja
Tag | VR | VL | Value Field   
Occupies 4 bytes. Denotes that the information is about Patient name
        PN – Occupies 2 bytes. 'PN' is ‘Person Name'. It denotes the data type of the value is Person name string.
        0C ( Hexadecimal value)  -  12 in Decimal, meaning the number of bytes for storing the value, 'Sridhar Raja'

57. How does a Patient name information is stored in an Implicit VR file?
4-Bytes | bytes | C bytes (in hex) or 12 bytes OO OC
Sridhar Raja
Tag | VL | Value Field
Note that the VR is missing in the above figure.
 Value Length occupies 4-bytes here. So, in an implicit VR file, VL occupies 4-bytes!

58. How Do I determine whether the File is an Explicit VR or Implicit VR?
                This is an important information you should know before parsing the file.
                This information is stored in (0002,0010) Transfer Syntax tag. 
                Note:    Group 2 elements are always Explicit.
  How Do I determine whether the File is a Little Endian or Big Endian?
        This information is stored in the same (0002,0010) Transfer Syntax tag.
        You will need to swap the bytes, if it is BIG ENDIAN. 
        Note: Group 2 elements are always in EXPLICIT VR LITTLE ENDIAN.
 I would like to find out the patient name information from the dataset.
How do I go about it?
       First determine the Transfer syntax.
       Search for the tag ‘ ’ inside the file. This tag is a 4-byte hex decimal
number. You will need to search this tag  through file to arrive at this tag. After
arriving at the tag, find out the value length and get the value. 

62. Steps for DICOM conformance
Compare the application from both devices
Compare the lists of supported DICOM SOP classes on both systems to make sure they match(older and newer SOP classes)
Match the communication roles of the two devices
Check the maximum number of associations allowed.
Match Presentation context

65. Security in DICOM HIPAA Anonymization Use of VPN
Use of secured protocol to transfer the images
Encryption of Image header data

66. DICOM TOOLS
JDICOM
DICOM Viewer

67. Questions?