1- List of modalities and study types 2- CT/US/DX Study Structure 3- DICOM composite instance IOD information module 4- Storage of DICOM image in PACS server 5- Imaging Data 6- Query and Retrieval from PACS 7- Window Width/ Window Center 8- DCM File Sections

1. DICOM
Digital Imaging Communications
in Medicine

2. Session Outline
 List of modalities and study types
CT/DX/US study structure
 Structure of DICOM image
DIOCM composite insatnce IOD information
Module
 How the dicom study came to PACS server
Transfer syntax for transfer study to PACS
 Storage of DICOM in PACS
Storage Services
 Query/Retrieve from PACS
Pre Fetch Data
 dcm File sections
 Imaging Data
 Imaging fundamental
 WW/WC
 Brightness and contrast

3. List of Modalities and study types
• Modality Types
• Modality CT
• Modality CR
• Modality US
• Modality XA
• Modality MR
• Modality DX
• Modality NM
• Modality RF
• Study Types-
• CT
• CR
• US
• XA
• MR
• DX
• NM
• RF
• BI
• DG
• ECG
• EM
• ES
• GM
• HC
• VL
• MG
• OP
• OPM
• OPR
• OPV
• PR
• PX
• RD
• RG
• RP
• RS
• RT
• RTIMAG
• SC
• SM
• SR
• LS
• TG
• VL
• XC

4. CT Study:
Study
Series
Instances

5. DX Study:
Study
Series
Instances

6. US study:
Study
Series
Instances & Frames

7. Structure of DICOM Study
• The data model defines Information Entities (IE’s)
• Patient
• Study
• Series
• Image
• The classes of the DICOM Objects however are composites
made of modules from different entities.
• The classes of the DICOM static data model are called SOP
(Service Object Pair) Classes and are defined by IOD’s –
Information Object Definition.

8. DICOM Composite Instance IOD Information Model

9. Secondary Capture Image IOD:
IE Module Usage
Patient Patient M
Clinical Trial Subject U
Study General Study M
Patient Study U
Clinical Trial Study U
Series General Series M
Clinical Trial Series U
Equipment General Equipment U
SC Equipment M
Image General Image M
Image Pixel M
Device U
Specimen U
SC Image M
Overlay Plane U
VOI LUT U
Modality LUT U
SOP Common M

10. Attribute Name Tag Type Attribute Description
Patient's Name (0010,0010) 2 Patient's full name.
Patient ID (0010,0020) 2 Primary hospital identification number or code for
the patient.
Patient's Birth Date (0010,0030) 2 Birth date of the patient.
Patient's gender (0010,0040) 2 Gender of the patient.
STUDY MODULE ATTRIBUTES:
PATIENT MODULE ATTRIBUTES:
Attribute Name Tag Type Attribute Description
Study Instance UID (0020,0008) 1 Unique identifier for the Study.
Study Date (0008,0020) 2 Date the Study started.
Study Time (0008,0030) 2 Time the Study started.
Referring Physician's Name (0008,0090) 2 Name of the patient's referring physician
Study ID (0020,0010) 2 User or equipment generated Study
identifier.
Accession Number (0008,0050) 2 A RIS generated number that identifies the
order for the Study.

11. Attribute Name Tag Type Attribute Description
Modality (0008,0060) 1 Type of equipment that originally acquired the data used to
create the images in this Series.
Series Instance UID (0020,000E) 1 Unique identifier of the Series.
Series Number (0020,0011) 2 A number that identifies this Series.
Laterality (0020,0060) 2C Laterality of (paired) body part examined.
SERIES MODULE ATTRIBUTES:
Attribute Name Tag Type Attribute Description
Conversion Type (0008,0064) 1 Describes the kind of image conversion
Modality (0008,0060) 3 Source equipment for the image.
SC EQUIPMENT MODULE ATTRIBUTES:

12. GENERAL IMAGE MODULE ATTRIBUTES:
Attribute Name Tag Type Attribute Description
Instance Number (0020,0013) 2 A number that identifies this image.
Patient Orientation (0020,0020) 2C Patient direction of the rows and columns of the
image.
Content Date (0008,0023) 2C The date the image pixel data creation started.
Content Time (0008,0033) 2C The time the image pixel data creation started.

13. IMAGE PIXEL MACRO ATTRIBUTES:
Attribute Name Tag Type Attribute Description
Samples per Pixel (0028,0002) 1 Number of samples (planes) in this image
Photometric
Interpretation
(0028,0004) 1 Specifies the intended interpretation of the pixel data
Rows (0028,0010) 1 Number of rows in the image
Columns (0028,0011) 1 Number of columns in the image
Bits Allocated (0028,0100) 1 Number of bits allocated for each pixel sample. Each
sample shall have the same number of bits allocated.
Bits Stored (0028,0101) 1 Number of bits stored for each pixel sample. Each
sample shall have the same number of bits stored.
High Bit (0028,0102) 1 Most significant bit for pixel sample data. Each sample
shall have the same high bit.
Pixel Representation (0028,0103) 1 Data representation of the pixel samples. Each sample
shall have the same pixel representation.
Pixel Data (7FE0,0010) 1C A data stream of the pixel samples that comprise the
Image.
Planar Configuration (0028,0006) 1C Indicates whether the pixel data are sent color-by-plane
or color-by-pixel.

14. SOP COMMON MODULE ATTRIBUTES:
Attribute Name Tag Type Attribute Description
SOP Class UID (0008,0016) 1 Uniquely identifies the SOP Class
SOP Instance UID (0008,0018) 1 Uniquely identifies the SOP Instance
Specific Character Set (0008,0005) 1C Character Set that expands or replaces the Basic
Graphic Set.

15. How the DICOM study send from modality to PACS
• Auto forward is a configuration in modalities which facilitate the
automatic transfer of images to the desired DICOM destination
once the technician completes the study.
• In real life technologists may not want to send the complete
study to the PACS or they may want to add another series which
could be for example a series containing lung window or bone
window of acquired study.

16. Transfer Syntax for transfer study to PACS
• When sharing objects with other applications,
everyone should be able to use the same object. The
common solution for such problems is serialization.
• Serialization is the process of writing a data structure
or object state to a format that can be stored in a file
or transmitted across a network so it can be read on
the other side of the same or by another process.

17. Storage of DICOM study in PACS
• The modality acquires the images in full resolution, i.e.,
uncompressed, and the PACS typically compresses the
images in a lossless compressed format.
• Compression will be of 2 types-
– Lossy: lossy compression reduces a file by permanently
eliminating certain information, especially redundant
information.
– Lossless: This will compress every single bit of data that
was originally in the file remains after the file is
uncompressed. Ex-
• JPEG2000
• RLE
• Even JPEG-LS

18. Storage Services of DICOM in PACS
• The DICOM Storage service is a fundamental service in
DICOM, as it allows exchange of data among multiple
devices over the DICOM network.
• In DICOM Storage Commitment service SCU(Service
class user) issues a normal DICOM Storage request to a
SCP (service class provider) in order to transfer some
DICOM data, and the SCP accepts this Storage request by
returning a successful C-STORE-RSP message, there is
the guarantee that the SCP has simply accepted the
transferred DICOM data.

19. Query/Retrieve Service
• The Query phase:
During the Query phase, the SCU sends a C-FIND-RQ
(request) message to the SCP, also including eventual
search parameters, and the SCP is expected to answer
returning one or more C-FIND-RSP (response) messages
to the SCU, conveying the items matching the search
criteria.
• The Retrieve phase:
During the Retrieve phase, the SCU sends a C-MOVE-
RQ (request) message to the SCP, specifying the items to
be retrieved (normally, a Patient, a Study, a Series or a
Instance). This request will trigger the transfer of the
appropriate DICOM data through the DICOM Storage
service (through C-STORE messages)

20. Pre-fetch Data:
Workflow automation mechanism, for fetching relevant prior
studies of the Patient from Image Archives (PACS).This
service is able to retrieve the DICOM objects back from the
archive to a specific local file system.
Why Prefetch:
– Required for diagnostic scenarios which need
comparison of studies acquired over time.

21. dcm file sections :
In a dcm file 3 sections will come-
• Header- It stores demographic information about the patient,
study (imaging study, image dimensions) and information
required by the computer to correctly display the image.
• Meta Data- It provide the information about image data, such as
the size, dimensions, bit depth and equipment settings used to
capture the image.
• Look up Table(LUT)- LUT transformation transforms the modality
pixel values into pixel values which are meaningful for the user
or the application. There are 3 types of lookup table (LUT) in
dicom:
• Modality LUT
• VOI LUT
• Presentation LUT

22. Imaging Data
• Study components:
– Imaging data- A medical image is
the representation of the internal
structure or function of an
anatomic region in the form of an
array of picture elements called
pixels.
– Non imaging data -
• A DICOM data object consists of
number of attributes-patient, study
and series.
• It contains Structured Report(SR)
also. This report is generate in
modality.

23. Imaging Fundamental
• Modality units- For instance, the original pixel values could
store a device specific value that has a meaning only when
used by the device that generated it.
• Imaging Units
• Transformation-
• Linear- The rescale intercept and slope are applied to
transform the pixel values of the image into values that
are meaningful to the application.
• Non-Linear- When the transformation is not linear, then
a LUT (lookup table) is applied.

24. What is WW/WC
• Window Center contains the input value that is the center of the
window. Window Width contains the width of the window.
• The window width/center specify which pixels should be visible:
all the pixels outside the values specified by the window are
displayed as black or white.
• To calculate the pixels to display using the window center/width:
1.) lowest_visible_value = window_center - window_width / 2
2.) highest_visible_value = window_center + window_width / 2
• For instance, if the window center is 100 and the window width
is 20 then all the pixels with a value smaller than 90 are
displayed as black and all the pixels with a value bigger than 110
are displayed as white.

25. What is Brightness Contrast
• Up to decrease brightness
(window level goes up)
• Down to increase
brightness(Window level
goes down)
• Left to increase contrast
(window width shrinks)
• Right to decrease contrast
(window width expands)

26. Thank You!