Siemens XA30 software platform and OHIF viewer compatibility issue

[Ajay Kurani]

Hi OHIF Experts,

I wanted to bring up a compatibility issue with the new Siemens XA30 software platform and OHIF viewer in case there are any suggestions.  Currently each slice is output as a separate dicom image.  This is especially problematic for resting state images as the viewer will try to load 20,000 images for our high resolution scans and end up timing out.  GE scanners also output images in a similar fashion.  I wanted to bring this up as it looks like this is the format Siemens will be using for the foreseeable future, in case this can be handled differently in the OHIF viewer such that the images can be loaded in mosaic format or at least per volume instead of individual slices.  

I think we would like to keep the outputs the way they are instead of exporting legacy on Siemens, especially as we are planning more advanced pipelines that can take advantage of individual slice dicom information for corrections. Similarly, GE data has this same issue.  Are any planned updates to OHIF viewer on XNAT such that not all 20,000 images are loaded into memory upon project load such that the page is more responsive.  For example, if there is a 500 volume buffer (or some value that makes sense) per image modality, this will allow all structural scans to be loaded just as they normally are, and legacy DTI and resting state scans without issue.  However, the newer XA30/GE data will only keep 500 volumes (or some value that makes sense) in buffer at a time such that the OHIF page loads quickly you can scroll through volumes.  Or perhaps the 500 volume buffer is the limit when the page is opened and when you actually click on the resting state or diffusion scan it begins to load a larger set into memory.  

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Thanks,

Ajay

[Mo Alsad]

Hi Ajay,

The viewer employes a stack prefetching mechanism to load and cache images. Stack prefetching is enabled for the active scan. When you switch to another scan, the stack prefetch is stopped on the previous scan and enabled/resumed on the current scan.

The stack prefetch has a property (maxImagesToPrefetch) that can control the number of images to be loaded. This property is set to Infinity by default. As a simple and straightforward fix, I can expose this property to be set by a site admin at project-level. If that seems as a reasonable solution, then I may be able to support it in the next release of the viewer.

Kind regards,

Mo

[Ajay Kurani]

Hi Mo,

1. I think this would be great if it can be exposed as it can help us fine-tune the loading for our system. I think this limit will help once you are in the viewer itself so that larger series can load smaller chunks.
2. Another related problem is loading the viewer from the session level page once you click view images button on the XNAT interface. I have attached screenshots of an example session scan protocol/data sizes so you can get an idea of the absurd number of images generated with the GE system (as well as the new Siemens XA30). Essentially it is one image per slice per timepoint, so a resting state scan ended up being over 76,000 images! The session level is a typical scan sequence for this project, and once I clicked view images it took 5-7 minutes before the viewer opened. This does not happen on other projects, so I suspect the prefetch of all images (infinity limit you mentioned) also occurs once you click view images and it generates the layout. I am hoping for this exposed limit also fixes this separate, though related issue of initially opening the OHIF viewer.
3. When in the viewer, I get a warning that a dataset is 4D and that the dataset is not a reconstructable 3D volume. MPR mode is unavailable. I would think the slices would stack to make a 3D volume for the viewer and navigated with up and down arrows and then you could toggle between timepoints with left and right fo a given slice. Is this something that would be possible to implement?

Best, Ajay