Managing the Medical Web Viewer Cache

Summary

Caching is an important element in implementing LEAD’s Multi-Resolution and Tiled Image (MRTI) SDK technology. Using MRTI, images as large as 1 TB can be streamed. A low resolution image is loaded while the large image is being retrieved. Large images can be stored on the server, and only the region-of-interest and near neighbors are sent to the client. The result is a nimble viewer that saves memory resources on both servers and clients.

The Leadtools.Medical.WebViewer.WCF.dll uses the Storage Server as a plugin to process OnStore requests. It then adds the tasks to a private message queue called the “storageserver”. The Leadtools.Tasks.ServerProcess.exe processes what is in the queue and creates the MRTI.

There are two ways MRTI caching can be disabled when DICOM files are imported:

  • From the Storage Server manager, open the Storage Settings menu and then select Options. Clear the Use Message Queue check box.
  • From the Web service, open the web.config file, and edit the value of (caching.OnStore) to be false

The C:\LEADTOOLS 20\Examples\DotNet\PACSFramework\MedicalWebViewer\Leadtools.Medical.WebViewer.WCF\web.config file has several settings in the appSettings section that can be used to manage caching, as shown in the following code:

<!-- enable/disable caching--> 
    <add key="Caching.Enabled" value="false"/> 
    <!-- location for storage, leave blank to use storage server's default location--> 
    <add key="Caching.Storage" value="d:\ltcache"/> 
    <!-- when to start caching frames threshold, any frame that has dimensions larger than valueXvalue will be cached--> 
    <add key="Caching.Threshold" value="600"/> 
    <!-- maximum percentage of disk space to use for caching --> 
    <add key="Caching.DiskQuota" value="70"/> 
    <!-- enable caching when files are stored to the storage server--> 
    <add key="Caching.OnStore" value="false"/> 
    <!-- enable fast low quality resize for huge frames, saves processing time, recommended to be set to true--> 
    <add key="Caching.FastResizeHugeFrames" value="true"/> 
    <!-- delete cached files after the specified time has elapsed--> 
    <!--format is days.hh:mm:ss--> 
    <!--use 00:00:00 to disable cache cleanup--> 
    <add key="Caching.Lifetime" value="1.00:00:00"/> 

Note that the Caching.Enabled setting must be true in order for any of the other caching settings to be recognized.

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