DICOM conformance statements

What is DICOM?

Creating a Common Communication Standard

DICOM is a standard for transferring medical image data between different types of equipment in the diagnostic environment. The current release, DICOM Version 3.0 (1993), supports many different diagnostic imaging modalities, including CR, MR, CT, nuclear medicine, ultrasound, x-ray angiography and “secondary capture.” DICOM 3 provides:

• A specification for transferring medical images and related information between computers
• Emphasis on cross-vendor connectivity
• Use of existing communication standards

DICOM RT is an extension of the DICOM 3.0 standard that addresses radiotherapy.

Overview of DICOM by Merge

All information is grouped under a unique patient identity. A study generally contains one or more series that contain one or more images. The images in a series will usually consist of one or more images taken from a single modality such as CT or MR.

Each of the levels of information will have attributes that describe factors related to the information, for example, diagnosis notes, scaling values for the images or other important details required by staff or equipment used in diagnosis.

For each modality, specific useful attributes define characteristics or qualities that are often grouped together and referred to as an “object.”

Attributes may be mandatory, only required under certain conditions or completely optional. For two systems to transfer information, both systems must support the same modality object.

DICOM conformance statements

The definition of which data must be transferred for it to be received and usable at the receiving end must be compatible.

A DICOM conformance statement defines which modality, services and network protocols (e.g., TCP/IP) are supported and how each is used by the application. This is required to determine whether all essential information is provided, retained or used correctly and to determine theoretically whether two devices can transfer information accurately.

The system providing the information must have implemented the transmitting services (i.e., the service class user) and the receiving system must have implemented the receiving and storage services (i.e., the service class provider).

It is typical for two devices to transfer information in one direction, but not in the other. For example, most CT systems can send images to a treatment planning system, while few treatment planning systems can send images back to the CT.

Five objects define radiotherapy:

• RT image: Includes all the normal RT images, DRRs, portal images, simulator images and radiograms.
• RT plan: The geometric and dosimetric data for course of external beam treatment or brachytherapy.
• RT dose: The total dose distributions from the planning system – dose matrix, dose points, isodose curves and dose volume histograms.
• RT Treatment Record: Records all treatment session data.
• RT Structure Set: Patient related structures identified from diagnostic data, CT, virtual simulation and treatment planning system.