User Conformance Profile: DICOM Version 3.0 Compliance

STATUS: Release 1.5 - February 21, 1994

SOURCE:

    Fred Prior, Ph.D. 
    Chief, Section of Radiologic Computing and Imaging Science
    Department of Radiology
    The Pennsylvania State University
US Army Contract: DAMD17-93-M-4464


Table of Contents


Forward

The ability to acquire image information from medical imaging devices is critical to the success of Picture Archive and Communication Systems (PACS). The acquisition of information implies much more than simply transferring bits over a network. Medical image data must be associated with other information to permit the receiving system to fully exploit the images (e.g. display, analyze process, reformat, correlate).

While image transfer from a modality to a PACS is necessary, it is not sufficient. A PACS is an information system. It may include or be interfaced to a Radiology Information System and in addition may be interfaced to a Hospital Information System. Data integrity and consistency between and among these interconnected information systems is critical for the functioning of a medical treatment facility. Medical imaging modalities must be capable of accepting key patient and study identification information, associating this information with sets of images, and then transmitting both the image sets and associated information to a storage device.

To meet all of the above listed requirements, it is necessary that medical imaging modalities include a functional, digital image communication interface.

In 1983 the American College of Radiology and the National Electronic Manufacturers Association (ACR-NEMA) established a joint committee to develop a US standard for medical image communication. This effort culminated in the ACR-NEMA Digital Imaging and Communications Standard 300-1985. A second, updated version of the standard was published in 1988 (NEMA 300-1988).

Work began on a third version of the ACR-NEMA standard in 1988. To foster international collaboration it was decided to give the ACR-NEMA standard a new name, DICOM, thereby giving it a degree of independence from the standards body. DICOM is a nine part document which specifies both an ISO compliant profile (e.g., U.S. GOSIP) and an industry standard (TCP/IP) protocol stack. Application layer support is provided for both basic image communication and higher level information system interface functions. An object-oriented data model underlies the application layer service definitions.

DICOM has the advantage of being applicable to networked environments. The standard provides a mechanism for manufacturers to claim conformance and in so doing specify clearly what DICOM functions are supported.

This document specifies requirements to be met by vendors of DICOM 3.0 compliant medical imaging products. Specific requirements are included to ensure functional digital image communication between a piece of medical imaging equipment and the MDIS PACS.

1. Introduction

Vendors of medical imaging equipment who wish to claim conformance to any part of the DICOM 3.0 standard shall provide a written conformance statement with any technical description of their equipment. Such a conformance statement shall be structured according to the specification set forth in DICOM Part 2.

This document represents a User Conformance Profile. It is a conformance statement drafted by a potential purchaser of medical imaging equipment to state clearly the subset of DICOM functionality that shall be provided by a potential vendor. This document is also structured in accordance to DICOM Part 2 in as much as possible owing to the differing nature of its intended use i.e., this document defines the required minimum content of a vendors' DICOM conformance statement and does not, in itself, represent a conformance claim.

This document assumes that potential readers are fully conversant with the concepts and nomenclature of the DICOM 3.0 standard. No material of an explanatory or tutorial nature will be included beyond that contained in the forward.

This document does not specify a formal testing/validation procedure to assess an implementation's conformance to the DICOM standard or this profile. It is the purpose of this User Conformance Profile to form the basis upon which such a validation procedure can be constructed.

This document does not specify requirements to be met by a PACS or other information system. Certain functions of one or more Service Class Providers are assumed.

All conformance requirements specified in the DICOM V3.0 standard shall be met. In the case of conflict between the standard and this User Conformance Profile, the requirements of the User Conformance Profile shall take precedence.

2. Normative References

The following documents contain provisions which, through reference in this text shall be considered to be provisions of this document.

3. Definitions

Conformance Statement: a formal statement associated with a specific implementation of the DICOM Standard. It specifies the Service Classes, Information Objects, and Communication Protocols supported by the implementation.

User Conformance Profile: a formal statement of requirements defined by a potential user of DICOM conformant equipment that must be satisfied by a specific implementation of the DICOM Standard. It specifies the Service Classes, Information Objects, and Communication Protocols to be supported by the implementation.

4. Symbols and Abbreviations

The following symbols and abbreviations are used in this conformance specification.

5. Conventions

A diagram is used below to describe the application model that forms the basis of this User Conformance Profile. The conventions used in this diagram are described in figure 5-1.

6. Implementation Model

For purposes of this discussion two DICOM application entities will be defined: Study Management and Image Management. A conforming implementation may choose a different number of application entities. The specified functionality shall be met regardless of the structure of the implementation. The actual number and titles of all application entities shall be specified in the vendor's conformance statement.

6.1 Application Data Flow Diagram

Figure 6-1 illustrates the application model which is assumed by this User Conformance Profile.

The goal of this User Conformance Profile is to close the loop between modalities and information systems. To be specific, using DICOM tools this User Conformance Profile specifies a means to communicate patient and study identification information as well as patient demographics and study procedure descriptions from an information system (HIS/RIS/PACS) to an imaging modality. This User Conformance Profile also specifies the means whereby the modality returns sets of images that relate to the ordered study, with each image containing all information needed to fully exploit it in a PACS environment. Finally, this User Conformance Profile specifies that a modality must indicate the completion of what it sees as the study, including a list of the images that it believes to have been successfully acquired and stored. This final mechanism is structured so that the information system may view a study as a collection of image series generated by one or more modalities over an extended period of time, while the modality views a study as simply the set of images that it collected during a contiguous time period.

6.2 Functional Definition of Application Entities

Application Entity 1, Study Management

shall support the following functions:

Application Entity 2, Image Management

shall support the following functions:

6.3 Sequencing of Real World Activities

In the normal operation of an imaging modality the functions defined in section 6.1 will logically occur in a particular order. The following order of events and communications shall be supported by an imaging modality:

  1. Receive Event Report of scheduled study,
  2. Initiate Get of related patient information,
  3. Initiate Create of Study Component (indicating all acquired images that are to be stored),
  4. Initiate Store operations (one per image),
  5. Initiate update (N-SET) of final Study Component values.
  6. Application Entity Specifications

All providers of DICOM compliant equipment shall acquire an Organization Identifier as defined by ISO 9834-3 and DICOM Part 8, Annex A. This Identifier shall be used as a root to define Unique Identifiers.

All Associations shall be established using the DICOM 3.0 Application Context. A single DICOM Application Context Name is defined for this version of the DICOM Standard. This name is "1.2.840.10008.3.1.1.1".

7. Application Entity Specifications

7.1 Study Management Application Entity

7.1.1 Association Establishment Policies

The Study Management Application Entity shall initiate Associations for the following purposes:

The Study Management Application Entity shall accept Associations for the following purposes:

7.1.1.1 General Policies

The Maximum Length PDU negotiation shall be included in all Association establishment requests.

The SOP Class Extended Negotiation shall not be supported.

The SCU/SCP Role Selection Negotiation shall be supported for all Association establishment requests.

7.1.1.2 Number of Associations

The Study Management AE shall be capable of supporting up to four simultaneous Associations for processing N-EVENT-REPORT transactions. This AE is not required to initiate multiple simultaneous transactions.

7.1.1.3 Asynchronous Nature

The default, synchronous mode of operation shall be used on all Associations. The Asynchronous Operations Window negotiation is not required.

7.1.1.4 Implementation Identifying Information

The Implementation Identification Notification shall be supported on all Associations.

7.1.2 Association Initiation by Real-World Activity

The Study Management AE acting as an SCU of the Detached Patient Management SOP class shall initiate all Associations for the purpose of invoking N-GET service elements.

The Study Management AE acting as an SCU of the Study Component Management SOP class shall initiate all Associations for the purpose of invoking N-CREATE and N-SET service elements.

7.1.2.1 Real-World Activity 1: Receipt of Study Scheduled Event Report

When the Study Management AE acting as an SCU of the Detached Study Management SOP class receives a Study Scheduled Event Report it shall establish an Association with a SCP of the Detached Patient Management SOP class and invoke an N-GET service element to acquire patient identification and demographic information. The Referenced SOP Class UID and Referenced SOP Instance UID provided in the Referenced Patient Sequence attribute of the Study Scheduled Event Report shall be used to identify the patient SOP instance in the N-GET.

7.1.2.1.1 Presentation Contexts

Each time an Association is initiated the initiator shall propose one or more Presentation Contexts to be used on the Association. Table 7.1.2.1.1-1 lists the Presentation Contexts that shall be supported by the Study Management AE in the context of support for Real-World Activity 1.

Table 7.1.2.1.1-1 Presentation Contexts for the Receipt of Study Scheduled Activity:

7.1.2.1.1.1 SOP Specific Conformance Statement for the Detached Patient Management SOP

The N-EVENT-REPORT service element is mandatory but its use is not required by this conformance statement.

The N-GET optional service element shall be supported.

The following attributes shall be supported by both the SCU and SCP of Detached Patient Management:

Additional attributes that are defined as optional by the DICOM 3.0 standard may be included in the N-GET operation if these attributes are defined in the conformance statements of both the SCU and SCP.

The Referenced SOP Class UID and Referenced SOP Instance UID of the Referenced Patient Sequence (from the Study Scheduled Event Report) shall be used by both SCU and SCP to uniquely identify the patient. Other attributes of the Patient SOP instance are for display purposes and shall be used were required as attributes of related image information objects.

7.1.2.2 Real-World Activity 2: Study Started/All Series Stored

The Study Management AE is informed by an internal event when acquisition of images associated with a scheduled study has begun. The AE shall initiate an Association with an SCP of the Study Component Management SOP class for the purpose of invoking the N-CREATE service element. Valid values for all required attributes (type 1) associated with the N-CREATE shall be provided. The Study Component Status ID attribute shall be set to CREATED.

When all series associated with the scheduled study have been acquired and successfully stored to a device acting as an SCP of the Storage Service Class, the Study Management AE shall initiate an Association with an SCP of the Study Component Management SOP class for the purpose of invoking the N-SET service element. Valid values for all required attributes associated with the Referenced Series Sequence shall be provided. The Study Component Status ID attribute shall be set to VERIFIED if quality assurance review has been performed by the imaging modality or COMPLETED if no quality assurance review has been performed.

7.1.2.2.1 Presentation Contexts

Each time an Association is initiated the initiator shall propose one or more Presentation Contexts to be used on the Association. Table 7.1.2.2.1-1 lists the Presentation Contexts that shall be supported by the Study Management AE in the context of support for Real-World Activity 2.

Table 7.1.2.2.1-1 Presentation Contexts for the Study Started/All Series Stored Activity:

7.1.2.2.1.1 SOP Specific Conformance Statement for the Study Component Management SOP

The N-SET optional service element shall be supported.

The N-GET optional service element shall not be supported.

No optional attributes shall be supported.

The Detached Study Management SOP Instance UID that identifies a particular Normalized Study Instance (included in the Study Scheduled Event Report) shall be used to define the Study Instance UID in the related Composite SOP Instances. This same UID shall also be used in the Referenced Study Sequence Attribute of associated Study Components to link them back to the originally Study (i.e., Detached Study Management SOP instance).

The N-SET operation shall update the Referenced Series Sequence to accurately reflect the number of series and images that were successfully stored by a Storage SCP. If the Storage operation was only partially successful, the N-SET operation shall set the value of the Study Component Status ID to INCOMPLETE.

7.1.3 Association Acceptance Policy

The SCP of Detached Study Management shall initiate all Associations for the purpose of issuing N-EVENT-REPORT service elements. The Study Management AE shall only be required to support the Study Scheduled event (event 2).

7.1.3.1 Real-World Activity 1: Study Scheduled Event

When a study is scheduled by a departmental information system an event report is transmitted to the device or devices upon which the scheduled study is to be performed. The information system may optionally transmit this event report to all devices of the appropriate class (e.g., same modality).

7.1.3.1.1 Presentation Contexts

Table 7.1.3.1.1-1 lists the Presentation Contexts that shall be supported by the Study Management AE in the context of support for Real-World Activity 1.

Table 7.1.3.1.1-1 Presentation Contexts for the Study Scheduled Event Activity:

7.1.3.1.1.1 SOP Specific Conformance Statement for Detached Study Management SOP

The N-SET optional service element shall not be supported.

The N-GET optional service element shall not be supported.

Support shall be required only for event type 2, Study Scheduled.

7.1.3.1.2 Transfer Syntax Selection Policies

The DICOM Big Endian Transfer Syntax is preferred and shall be preferentially selected. The DICOM Implicit VR Little Endian Transfer Syntax is the default and therefore, shall also be supported.

7.2 Image Management Application Entity

7.2.1 Association Establishment Policies The Image Management Application Entity shall initiate Associations for the following purpose:

7.2.1.1 General Policies

The Maximum Length PDU negotiation shall be included in all Association establishment requests.

The SOP Class Extended Negotiation shall not be supported.

The SCU/SCP Role Selection Negotiation shall not be supported for all Association establishment requests.

7.2.1.2 Number of Associations

This AE is not required to initiate multiple simultaneous transactions.

7.2.1.3 Asynchronous Nature

The default, synchronous mode of operation shall be used on all Associations. The Asynchronous Operations Window negotiation is not required.

7.2.1.4 Implementation Identifying Information

The Implementation Identification Notification shall be supported on all Associations.

7.2.2 Association Initiation by Real-World Activity

An Association established with a Storage Abstract Syntax shall be used to transfer all images that comprise the series generated by the Image Management AE for a single study.

7.2.2.1 Real-World Activity 1: Series of Images Acquired

When a series of images have been acquired, or when all series corresponding to a study have been acquired, an Association shall be established with an SCP of the appropriate Storage Information Object SOP class and a C-STORE service element invoked to store each image information object.

7.2.2.1.1 Presentation Contexts

Each time an Association is initiated the initiator shall propose one or more Presentation Contexts to be used on the Association. Table 7.2.2.1.1-1 lists the Presentation Contexts that shall be supported by the Image Management AE in the context of support for Real-World Activity 1. A modality will normally only generate one class of image information object and, therefore, offer only a single presentation context.

No other Storage SOP classes shall be supported. Table 7.2.2.1.1-1 will require extension with subsequent releases of the DICOM standard.

Table 7.2.2.1.1-1 Presentation Contexts for the Series of Images Acquired Activity:

7.2.2.1.1.1 SOP Specific Conformance Statement for the Computed Radiography Image Storage SOP

The attributes of the Computed Radiography Image Storage SOP shall be specialized according to Table 7.2.2.1.1.1-1.

Table 7.2.2.1.1.1-1 Specialization of CR Attributes:

Additional attributes that are defined as optional by the DICOM 3.0 standard may be included in instances of the Computed Radiography Image Storage SOP if these attributes are defined in the conformance statement of the SCU.

Attributes of the Overlay Plane module shall only be included in a CR image information object instance if a graphic overlay is present.

Attributes of the Curve module shall not be included in any CR image information object instance.

7.2.2.1.1.2 SOP Specific Conformance Statement for the CT Image Storage SOP

The attributes of the CT Image Storage SOP shall be specialized according to Table 7.2.2.1.1.2-1. Table 7.2.2.1.1.2-1 Specialization of CT Attributes:

Additional attributes that are defined as optional by the DICOM 3.0 standard may be included in instances of the CT Image Storage SOP if these attributes are defined in the conformance statement of the SCU.

Attributes of the Overlay Plane module shall only be included in a CT image information object instance if a graphic overlay is present.

7.2.2.1.1.3 SOP Specific Conformance Statement for the MR Image Storage SOP The attributes of the MR Image Storage SOP shall be specialized according to Table 7.2.2.1.1.3-1. Table 7.2.2.1.1.3-1 Specialization of MR Attributes:

Additional attributes that are defined as optional by the DICOM 3.0 standard may be included in instances of the MR Image Storage SOP if these attributes are defined in the conformance statement of the SCU.

Attributes of the Overlay Plane module shall only be included in a MR image information object instance if a graphic overlay is present.

7.2.2.1.1.4 SOP Specific Conformance Statement for the Nuclear Medicine Image Storage SOP

The attributes of the Nuclear Medicine Image Storage SOP shall be specialized according to Table 7.2.2.1.1.4-1.

Table 7.2.2.1.1.4-1 Specialization of Nuclear Medicine Attributes:

Additional attributes that are defined as optional by the DICOM 3.0 standard may be included in instances of the Nuclear Medicine Image Storage SOP if these attributes are defined in the conformance statement of the SCU.

In addition to a presentation context based on the Nuclear Medicine Image Storage SOP, a compliant device shall be capable of offering a second presentation context based on the Secondary Capture Image Storage SOP. This alternate presentation context shall be considered as the minimum default compliance level.

7.2.2.1.1.5 SOP Specific Conformance Statement for the Ultrasound Image Storage SOP

The attributes of the Ultrasound Image Storage SOP shall be specialized according to Table 7.2.2.1.1.5-1.

Table 7.2.2.1.1.5-1 Specialization of Ultrasound Attributes:

Required attributes included in the Ultrasound Region Calibration Module shall be included in all Ultrasound Image information objects.

Attributes of the Audio module shall not be included in Ultrasound Image information objects.

Additional attributes that are defined as optional by the DICOM 3.0 standard may be included in instances of the Ultrasound Image Storage SOP if these attributes are defined in the conformance statement of the SCU.

In addition to a presentation context based on the Ultrasound Image Storage SOP, a compliant device shall be capable of offering a second presentation context based on the Secondary Capture Image Storage SOP. This alternate presentation context shall be considered as the minimum default compliance level.

7.2.2.1.1.6 SOP Specific Conformance Statement for the Secondary Capture Image Storage SOP

The Secondary Capture Image Storage SOP class shall be used to store images generated by film digitization, video frame grab, and workstation screen dump. This SOP shall also be used for images converted from a non-DICOM format when there is insufficient information available to utilize one of the other defined Storage SOP classes.

The attributes of the Secondary Capture Image Storage SOP shall be specialized according to Table 7.2.2.1.1.6-1. Table 7.2.2.1.1.6-1 Specialization of Secondary Capture Attributes:

Additional attributes that are defined as optional by the DICOM 3.0 standard may be included in instances of the Secondary Capture Image Storage SOP if these attributes are defined in the conformance statement of the SCU.

If overlays are present they shall be stored in group 7FE0. Corresponding instances of the attributes of the Overlay Plane module shall also be included in instances of the Secondary Capture Image information object.

The Modality LUT module shall not be included in instances of the Secondary Capture Image information object.

7.2.2.1.1.6.1 Minimum Image Format Conformance

The DICOM 3.0 Storage Service Class includes SOP classes for the storage of a subset of existing imaging modalities. The standard permits the list of supported modalities to be extended using private SOP classes.

Private Image Storage SOP classes shall not be used to meet the requirements of this User Conformance Profile. The Secondary Capture Image Storage SOP class shall be used for all unspecified imaging modalities. In addition the Secondary Capture Image Storage SOP class shall be used as an alternate minimum conformance level for Ultrasound and Nuclear Medicine.

7.2.3 Association Acceptance Policy

The Image Management AE shall not be required to accept Associations.

8. Communication Profile

8.1 TCP/IP Stack

All implementations shall conform to DICOM V3.0 TCP/IP Network Communication Support as specified in DICOM Part 8.

8.2 Physical Media Support

The Media Access and Physical layer protocols shall conform to ANSI (IEEE) 803.2 (Ethernet). The preferred physical medium is unshielded twisted pair (10Base-T).

9. Extensions/Specializations/Privatizations

Private SOP Classes and Transfer Syntaxes may be supported by a conforming device but they shall not be used as a replacement for any requirements defined in this User Conformance Profile.

No extensions or specializations beyond those defined in this User Conformance Profile shall be permitted

10. Configuration

10.1 AE Title/Presentation Address Mapping

A local (i.e., supported on the imaging modality) mechanism shall be provided to configure an AE Title/Presentation Address mapping table.

The SCP of the Detached Study Management SOP Class shall maintain a table of SCUs to which events are to be reported. This table shall be organized by modality. Other parameters may also be used to further define possible recipient categories. Study Management Event Reports shall be limited to only those SCUs that match the characteristics of the study. The SCP shall employ the Scheduled Study Location Application Entity Title attribute to specify the device upon which the study has been scheduled.

11. Support for Extended Character Sets

Extended character sets shall not be used in any operations covered by this User Conformance Profile.