Clarrification needed: Pre fetch of WADO objects and Query Retrieve with Series Metadata

[Amms]

Hello,

 Any body please explain the use case of Pre fetch of WADO objects ( https://github.com/dcm4che/dcm4chee-arc-light/wiki/Pre-fetch-of-WADO-objects )  and  Query Retrieve with Series Metadata (https://github.com/dcm4che/dcm4chee-arc-light/wiki/Query-Retrieve-with-Series-Metadata )

[Jon Ander Zuccaro]

Some viewers use WADO-URI to retrieve a JPEG representation of the image in order to display it.

Creating this JPEG requires reading and interpreting the DICOM image data and constructing the JPEG file in order to serve it.

Since the image data will not change after it was received, you can "pre create" this JPEG and cache it before any viewer requests it so when and if a request is made you can serve the JPEG directly. This will allow the user to receive the image a little bit faster since the heavy lifting of reading the DICOM file was done previously.

For subsequent calls to the same image you can return the same cached JPEG avoiding the costly operation of having to read the DICOM file and create the same JPEG over and over again.

The trade-off is that you need additional drive space to store these JPEG files.