2. Implementation Model

When bundled with the DICOM option, IMCO-RAD is an image database, storage, communication, and display facility. IMCO-RAD is a single application entity that stores images sent to it by service class users, allows queries based on several standard query models, retrieves requested images, and sends selected images to a storage SCP. When IMCO-RAD is first brought up, three threads of execution are instantiated which act as (1) a Connection Request Listener thread, (2) a DICOM Storage SCU thread, and (3) a File Reception processing thread.

The Connection Request Listener waits for association establishment requests to be received from external DICOM Application Entities that are issuing requests for storage service. When such a request is received, an additional thread (a DICOM Storage SCP thread) is created to handle DICOM objects delivered over the association; this thread remains extant until the association is terminated by the partner entity. Multiple such threads may be created and run concurrently, depending on limits established when the IMCO-RAD license was issued; the default is a maximum of two concurrent associations for reception of DICOM images.

As images are received over an association (embodied in one of the Storage SCP threads created by the Listener), they are placed into a specified directory (known as the DICOM "Holding Pen") in DICOM Part 10 format. The File Reception thread is designed to receive an event notification when a Part 10 file is written into the pen; it is "awakened" and initiates the process of parsing the DICOM tags and making the image accessible, and viewable, through the local IMCO-RAD database. This thread also moves the DICOM object into the currently active IMCO-RAD study directory, and compresses the image data, if need be, for transmission to another IMCO-RAD station.

The DICOM Storage SCU thread is used to deliver images to external DICOM Application Entities at user request, or as a result of an autorouting operation. IMCO-RAD maintains a queue of images to be sent to external destinations, and it is this queue that delivers images to this thread for delivery. This thread creates and tears down DICOM associations as needed with external DICOM entities.

An additional thread is created on an as-needed basis when a user issues a query against a remote DICOM image database. This thread implements a DICOM Query User, and is terminated upon successful delivery of the requested images to IMCO-RAD. No more than one such Query User thread may be active at a given time.

The IMCO-RAD AE is configured by means of several configuration files, which are typically created at installation time. These include IMCO-RAD.INI and DTK.INI. In addition, the DTK package is configured by means of a Microsoft Access Database which is installed on the user’s system as part of the IMCO-RAD installation process.

There are two local real world activities, Query Request and Send Request. Query Request causes the IMCO-RAD AE to initiate a DICOM association to a Query Class SCP. Query Request consists of an operator’s requesting a list of studies resident on the remote system and, upon receiving the response and seeing it displayed, requesting a download of a specified study using the C-MOVE service. Query Request interacts with the user via the native IMCO-RAD Graphic User Interface.

Send Request causes the IMCO-RAD AE to initiate a DICOM association to a Storage Class SCP. Send Request consists of an operator’s requesting a list of studies resident on the local system and, upon receiving the response and seeing it displayed, requesting an upload of a specified study using the C-MOVE service. Send Request interacts with the user via the native IMCO-RAD Graphic User Interface.

The IMCO-RAD AE, AEI, supports the following functions:

• Manually initiates a DICOM association to query the remote database.
• Manually initiates a DICOM association to send images to the remote database.
• Responds to DICOM associations with Presentation Contexts for SOP Classes of the Storage Service Class.
• Receives images on these Presentation Contexts, inserts them into the IMCO-RAD database, optionally compressing them at user-specified compression levels.
• Optionally sends studies to other IMCO-RAD or DICOM stations. The destination station is determined based on message content.

Query Request:

• The IMCO-RAD AE initiates a DICOM association.
• The AE selects the appropriate Abstract and Transfer Syntaxes from those accepted by the remote AE.
• The AE uses the C-FIND service to request information regarding all remote studies satisfying the specified criteria.
• The C-FIND response is used to create a Dialog Box from which the user may select a study of interest.
• The specified study is requested via the C-MOVE service. The remote AE uses the C-STORE service to send the requested study to the IMCO-RAD AE.

Send Request:

• The IMCO-RAD AE initiates a DICOM association.
• The user is presented with a Dialog Box from which the user may select a study of interest.
• The AE selects the appropriate Abstract and Transfer Syntaxes from those accepted by the remote AE.
• The specified study is sent to the remote SCP via the C-STORE service.

Image Receiver:

• The IMCO-RAD AE responds to a DICOM association initiation and accepts only the Abstract and Transfer Syntaxes specified in this document.
• At a later time, the AE responds to C-STORE requests and places received images, in DICOM Part 10 format, into a specified directory.
• As each image is received, the local AE processes the received image by creating or adding to IMCO-RAD studies with (optionally) compressed data.
• If the appropriate setting appears in the configuration file, the resulting study or studies are enqueued for sending to destination IMCO-RAD or DICOM stations. The IMCO-RAD AE determines the destination to send the studies based on elements in the DICOM messages. The studies are routed based on the contents of the AE-Title element (0002, 0016); the contents of this tag are used to look up a routing destination in the IMCO-RAD communications directory. This destination includes a protocol to be used during the routing operation; this protocol may be a IMCO-RAD-to-IMCO-RAD protocol, or DICOM if the destination is a non- IMCO-RAD DICOM Storage SCP. If the routing element does not appear in the received message but the configuration file specifies delivery to remote IMCO-RAD stations, then the study is sent to the IMCO-RAD station that had last received a study from this AE.
• The creation and enqueueing of studies for routing to remote sites are logged as events in a IMCO-RAD system log, including time, date, study instance UID, patient name and ID, and number of series and images.

3. AE Specifications

This Application Entity provides Standard Conformance to the following DICOM V3.0 Verification SOP Class as an SCP.

This Application Entity provides Standard Conformance to the following DICOM V3.0 Storage SOP Classes as an SCP.

IMCO-RAD provides DICOM V3.0 TCP/IP Network Communication Support as defined in Part 8 of the DICOM standard.

IMCO-RAD inherits its TCP/IP stack from the computer system upon which it executes. IMCO-RAD expects the host system to present a WINSOCK-style interface to its TCP stack.

5. Configuration

IMCO-RAD obtains configuration information from the following sources:

6. Support for Extended Character Sets

IMCO-RAD supports the following character sets:

• ISO-IR 6 (default) Basic G0 Set
• ISO-IR 100 (default) Latin Alphabet No. 1