CTP Configuration for Study Distribution

This article describes how the CTP application can be configured to distribute patient studies to referring physicians and researchers. The intended audience for this article is system administrators. There are several articles on CTP on the RSNA MIRC wiki. All would be useful references when reading this article.

1 Requirements

Many hospitals distribute digital examinations to referring physicians by producing DICOM CDs. The cost and time to produce and distribute these CDs, along with the lack of standardization of the software viewers for them, has limited their acceptance by referring physicians, although most people acknowledge the need to make such information available quickly and conveniently.

This section describes a CTP configuration with these features:

• Studies are received from modalities or PACS via the DICOM protocol.
• Studies are partially anonymized to remove unnecessary PHI (though not all PHI).
• Studies are stored.
• A user account is automatically created, if necessary, for the patient when a study is received.
• Patients can view their studies at a web browser.
• Patients can download and/or delete their studies.
• Patients can make their images available to their physicians, either by providing their credentials to their physicians or by granting their physicians guest access to their studies.
• Administrators can grant physicians guest access to a patient's studies on behalf of the patient.
• The system can automatically remove studies older than a specified age.

2 The Configuration File

The configuration of a CTP instance is specified by an XML file called config.xml located in the same directory as the program. See the main wiki article for details on how CTP processes data objects and all the standard pipeline stages that are available. This section describes only those standard stages which are necessary to implement this application, and only those attributes which are required to provide the necessary features.

<Configuration>

   <Server port="1080" />

   <Pipeline name="Pipeline">

        <DicomImportService 
            name="DICOM Import Service"
            class="org.rsna.ctp.stdstages.DicomImportService"
            root="roots/dicom-import" 
            port="104" />

        <DicomAnonymizer
            name="DICOM Anonymizer"
            class="org.rsna.ctp.stdstages.DicomAnonymizer"
            root="roots/anonymizer"
            script="roots/anonymizer/scripts/da.script"
            quarantine="quarantines/anonymizer" />

        <FileStorageService
            name="File Storage Service"
            class="org.rsna.ctp.stdstages.FileStorageService"
            root="storage"
            timeDepth="90"
            fs-name-tag="00080020"
            auto-create-user="yes"
            port="80"
            require-authentication="yes"
            quarantine="quarantines/storage" />

    </Pipeline>

</Configuration>

2.1 Server

The configuration file places the CTP admin web server on port 1080. This web server is used by administrators to monitor the status of the system. The choice of 1080 rather than the standard port 80 is made to preserve port 80 for the FileStorageService's web server.

2.2 DicomImportService

The configuration file puts the DicomImportService on the standard well-known DICOM port, (104). The DicomImportService accepts all Application Entity Titles, so when configuring the transmitting systems (modalities or PACS), any AE Title can be used.

2.3 DicomAnonymizer

This stage is included in the pipeline to allow unnecessary PHI to be removed before storage. An example of what might be done is to replace the patient's name with his initials (using the @initials function. The DicomAnonymizer provides many functions. See The CTP DICOM Anonymizer for the excruciating details. If anonymization is not required, this stage can be removed from the configuration file.

2.4 FileStorageService

The root attribute can point to any location where the FileStorageService can build its directory structure. It is shown in the configuration above as a relative path from the CTP directory (the directory in which the CTP application runs) to the storage directory. An absolute path may be specified instead, and that path can be on a shared drive on another computer if so desired.

The fs-name-tag attribute is critical to the operation of this application. It is specified to point to the DICOM PatientID attribute. This causes the FileStorageService to create a separate tree of directories for each patient and to store all the patient's studies in that tree. Since access is restricted by such trees, this ensures that each patient can only see his own studies. For more information on the organization of directories, see the notes in FileStorageService.

The timeDepth attribute is included with its value set to 90. Studies older than 90 days will then automatically be deleted. If permanent storage is desired, the attribute should be set to zero.

The FileStorageService web server is enabled in this configuration by specifying a port attribute. The value, 80, assumes that this will be the most convenient port for users.

The require-authentication attribute is required to ensure that only authorized users can view studies. More information on access to studies is contained in The CTP FileStorageService Access Mechanism.

The auto-create-user attribute is included so that the system will create user accounts for users as their studies are received. This is only an administrative convenience. Administrators can use the User Manager servlet on the main admin web server to create and manage accounts at any time.