DICOM Server Configuration

Definition of PMOD as a DICOM Server

PMOD can run a DICOM server process in the background which is able to receive data sent to it from modalities or a picture archiving system.

In general, a DICOM server is defined by three entities, the:

• IP-number (or host name) of the computer on which the DICOM server is running,
• Port number on which the server is listening,
• Application Entity Title (AET) which has been given to the server.

The last two entities for the operation of PMOD as a DICOM server are configured on the DICOM / DICOM SERVER pane.

Note: On Linux systems there exist reserved ports which require special permission to allocate. If such a port is defined as the PMOD DICOM server port, the server cannot be started from a user account and issues a message Permission denied. Starting as root will normally succeed, but this has the disadvantage that the saved files will all belong to the root. To prevent this situation a higher port number (typically >4000) should be used on Linux, rather than the default DICOM port 104. PMOD uses 4030 per default.

Besides the basic server information there are three checks relevant for the DICOM server operation:

• Accept incoming connections from any AE: If this box is not checked, the DICOM server only accepts remote systems which are configured as remote DICOM clients. If it is checked, any association request will be accepted.
• Do not sent implementation version name (server): Allows switching off sending the implementation version component. This is required if a client does not handle this exchange properly and connection to PMOD server fails.
• Force default transfer syntax for all incoming connections: Transfer syntax negotiation may fail when a client proposes only one transfer syntax which is not the DICOM default and a PMOD server prefers another. In such cases the option forces the PMOD server to always negotiate the default Little Endian Implicit transfer syntax which all DICOM applications are required to support.

Normally the DICOM server is receiving data over the network from DICOM clients. However, it is also possible to have the DICOM server scan a directory and treat found DICOM series in the same way as if they had arrived by the network. This functionality can be configured by the Check Incoming Folder box. If it is checked, the directory to be scanned can be entered as well as a scanning interval every ... seconds. This import feature can be used to convert from DICOM to any other output format, or to add DICOM images to a PMOD database. Note that after processing the images by the DICOM server they are removed from the incoming folder.

In the bottom section of the DICOM server configuration the following options are available:

• Start automatically: If this radiobutton is enabled, the DICOM server is started automatically with PMOD, independently of user login. Otherwise it must be started using the DICOM button in the PMOD toolbar, or as a background process from a script.
• Stand alone: if this radiobutton is enabled allows generating a script. This script can be use to start the Dicom server.
• Verbose commands: If this box is set detailed communication informations are send to the log file. This may be helpful in the case of connectivity problems. Note that enabling this checkbox slowdowns the server operations.
• Redirect output: If this checkbox is enabled the stand alone server output is redirected to a file.
• Save Starting Script button serves for generating a starting script for the DICOM server with the defined configuration. It shows a dialog window which allows naming the script, which is created in the Start folder within the Pmod3.3 directory.

  

• The advantage of using a script is that the DICOM server can continue running while PMOD is not in use. The -std flag indicates the standard communication port, while -tls would be used for specifying the secure port.

Saving the Images in a Database

The following configuration is recommended for all users who run a local database.

In this example the DICOM server, when run as user user 1, is receiving the images in the directory C:/Pmod3.3/data/dicom/tmp, saves them in the database Pmod, and then deletes the images in the temporary directory. When a remote DICOM client queries the PMOD DICOM server for studies, it will list all the studies in the Pmod database.

Support for Secure DICOM

Standard DICOM communication is not secure, and therefore is not recommended over public networks. To overcome this problem, a DICOM supplement has been finalized which allows implementing secure connections. PMOD supports one of the proposed variants called BASIC TLS SECURE TRANSPORT CONNECTION PROFILE. Of the three optional features (entity authentication, encryption, integrity check) encryption is implemented in the current release. As a consequence, the data transferred can only be interpreted by the target DICOM server with which the communication has been established.

The PMOD server may be configured to accept secure and insecure connections at the same time on two different ports. One port is designated for standard TCP/IP connection and the other for secure TLS connections. To enable secure DICOM, enable the Secure (TLS) checkbox, define a Port number, and the AET.

What happens with received DICOM Images

There are different possibilities what the PMOD DICOM server can do with the received images:

• Save them in a directory structure and update the DICOMDIR file (DICOM part 10 conformant).
• Save them in a database as the original DICOM objects.
• Convert them to any of the supported formats and save them as files, eg. as NiFTI files.
• Convert them to a JPEG file, and print a report page.

PMOD has the capability to configure different behaviors of the DICOM server. The configuration is not tied to the PMOD user who starts it. Therefore, the saving configuration is performed in the DICOM section of the PMOD configuration. So please select the DICOM tab and finally the DICOM SERVER sub-tab. Example configurations are shown below, but many other conversions are also possible.

Saving the Images as DICOM Part 10 Offline-Files

Alternatively, the received images can be saved in a DICOM Part 10 compliant manner. This behavior is configured as follows.

With this configuration, the images are stored in a directory hierarchy starting at Pmod3.3/data/dicom/storage. A DICOMDIR file will be maintained in the same root directory, and used to answer queries.

Note that you can use PMOD to create DICOM-compliant CDs. Just burn the DICOMDIR and the directory containing the DICOM files to a CD.

Filtering out Secondary Capture Images and Printing them

The configuration below illustrates the conversion capabilities.

With this configuration, the images are converted to JPEG (GRAPHIC), a report page is prepared (Print hard copy) and sent to the system default printer, but only if the incoming object is of type Secondary Capture (Convert SC objects only). The original DICOM files are deleted, but the JPEG images are retained in the directory Pmod3.3/data/dicom/graphic . The additional checks allow routing the SC DICOM objects to a remote DICOM server, and deleting the JPEG files after printing.

Recommendations

Note that DICOM serves can be started and operated without consuming a PMOD license. This allows moving them to a server machine that is continuously operating and has fast disks. On this server machine perform a standard PMOD installation, plug the USB license protection key in, and use the Config facility for the database configuration and DICOM server script generation. Then start each of the DICOM server scripts in a separate command window. The USB key is now not any more necessary.