This section discusses ways to obtain the optimum performance from this feature.
The performance of the feature can be directly affected by the different usage scenarios for implementation. This section discusses different elements that can affect performance.
The following factors can be used to measure performance:
number of images per second (for an image of fixed size) that the DICOM component can insert into Content Server for each checkin configuration option.
number of images per second (for an image of fixed size) that the DICOM adapter can serve to a DICOM client.
number of images per second (for an image of fixed size) that the DICOM adapter can retrieve from a DICOM client.
The performance of this feature can be impacted by the following elements:
the response time of Content Server
the response time of the DICOM client
the number of managed DICOM clients
the polling interval of each managed client
DICOM image size
The following list describes several key usage scenarios, with a discussion following about the performance impacts of each scenario:
The DICOM Crawler queries the set of managed DICOM clients (such as PACS), retrieves any new images, and the DICOM adapter uses the DICOM component to check the images into Content Server.
The DICOM adapter responds to a query from another DICOM client (such as a DICOM viewer), searches for relevant images and metadata stored in Content Server, and sends the result set back to the DICOM client.
A WebCenter Content application uses the DICOM component to directly check in a DICOM image to the Content Server.
A WebCenter Content application uses the DICOM component to create a new DICOM image by checking in a non-DICOM source image (such as a .jpeg file) and the corresponding DICOM XML metadata to the Content Server.
A WebCenter Content application queries the Content Server directly to search and retrieve DICOM images checked in using the DICOM component.
An HTTP client queries the WADO proxy to retrieve a DICOM image where Content Server only manages image metadata (but where the original image is stored in the PACS) via a WADO-formatted URL.
The following list discusses the performance impacts of the different scenarios:
Scenario 1: the performance is impacted by all of the performance elements listed above. In this case, the DICOM Crawler and DICOM adapter must communicate with both DICOM clients and WebCenter Content. Therefore, performance will be impacted by the responsiveness of the systems. The DICOM component must process each of the images added so the size of the images will impact processing such as thumbnail generation, metadata extraction, and check-in time. In addition, there may be many managed DICOM clients and the number of these clients will impact the load on the system (as well as how frequently these clients are polled).
Scenario 2: the DICOM adapter must issue a query to the content server, retrieve any relevant DICOM image data or metadata, and send this result set back to the DICOM client. The performance is primarily impacted by the content server response time (both search response and data exchange) and the DICOM client response time. The DICOM image size will also play a role because the image data must be transferred between the Content Server and the DICOM client.
Scenarios 3 and 4: the DICOM component must process an incoming DICOM image designated for check-in (where in case 4 the DICOM image is generated first). The service is responsible for processing the DICOM image. For example depending on configuration options and service parameters, the service must extract metadata from and generate a thumbnail image of the given DICOM image. The primary performance considerations in this scenario are Content Server response time and DICOM image size.
Scenario 5: a WebCenter Content application queries Content Server directly to retrieve DICOM image content (or metadata) that has been checked in by the DICOM component (or indirectly from the DICOM adapter). The performance considerations are similar to retrieving any type of image from Content Server.
Scenario 6: an HTTP client queries the WADO proxy to retrieve a DICOM image stored in a DICOM client (such as a PACS). In this case, the WADO proxy will first issue a DICOM request to retrieve the image from the DICOM client and then will return the image data to the HTTP client in response to its request. The performance for this type of request is influenced by the responsiveness of the DICOM client and the size of the image.
One tunable performance attribute is the managed DICOM client polling interval (see Section 2.3.2, "Configuring the DICOM Crawler"). For each managed DICOM client, this interval indicates how long the DICOM crawler must wait before querying the DICOM client for new images since the time the last query was initiated. As the value for this parameter is lowered, the load on the system, network, and DICOM client increases due to the increased frequency that the DICOM client is queried.
As this parameter is tuned, the indexing interval for Content Server may need to be modified in order to make the new images that have been checked in available for search.
Another tunable performance attribute are the options controlling what data is retained or generated by the DICOM component on checkin. Options include:
retain the original DICOM image
metadata-only checkin with no image checked into Content Server. Only Content Server metadata fields are populated.
image preview generation
DICOM XML metadata generation
The metadata-only checkin option yields the best performance for checkin, but may yield sub-optimal performance for image retrieval where it would be better if Content Server stores the original image). In either case, image preview generation and DICOM XML metadata generation will only impact checkin performance.
The Content Server administrator (or user) who manages the DICOM adapter suite should tune the managed DICOM client polling interval to balance responsiveness with the load of managed DICOM clients. Tuning cannot be performed automatically because the user may have a preference for how much load this component should impose on DICOM clients in the given setup.
The administrator or user should also tune the checkin options for DICOM images. This value cannot be tuned automatically because the user may require the usage of image preview and/or DICOM XML metadata generation features, or specific storage concerns may need to be addressed for the site where the product is installed.