Monday, February 25, 2008

Stacks of Tiles

I like some degree of flexibility in my PACS display, but I like it simple. This has been a very difficult concept to convey to Agfa in the process of my occasionally-welcome attempts to help with Impax 6.x development. (I do have to tell you that Impax has been behaving quite a bit better these days, with crashes occuring only very rarely.) I have had a really hard time convincing them that any series should be deployable in any viewport. In other words, if I want to put the same CT series on the screen in 10 places, that should be possible. This idea just hasn't yet penetrated. The only way to do anything like this now is to create a "clone window", which can be set up to display multiple instances of the same series. However, I cannot link a "regular" series to one in the clone window, and there are some glitches in the implementation of window and level adjustments, rendering the clones limited at best.

Why is this important to me? An article that I rediscovered recently from the American Journal of Roentgenology by Drs. Kim and Lee, et. al., gives one possible answer. These radiologists from the Department of Radiology of Seoul National University looked at scans of hepatocellular carcinoma in two different modes. First, they used the old "tile" mode, showing a dozen slices from the scan on screen at once. Frankly, nobody does it this way anymore. Secondly, they used "multisynchronized stack" mode to view the multiphasic dynamic CT. While they didn't include any pictures in the article, I'm assuming the stack display looked something like this:

The key here is that you have multiple phases (with different series) of the same study, synchronized to the same level. A dynamic study of this type means that the patient was scanned as IV contrast was injected, and then at several fixed delay times thereafter. Thus, if the reader does stumble upon a lesion, he/she can see how the contrast material enters and exits the lesion, which yields a better depiction of the contents of the mass. With this display, you have all phases of the study up at the same time, and synchronization allows you to scroll through the study and view the lesion on all of the phases at once. This is much easier than trying to view "tiles" of all the series, and even better than viewing one stacked series at a time.

The flexible display lends itself to other approaches. I like to view abdominal and chest studies in this 4-up configuration with soft-tissue, bone, and lung windows, as well as the scout, all on-screen at once.

I do the same thing with head CT's, adding in a "blood" and a very narrow windowed viewport to aid in detecting subtle CVA's.

I guess the point of all this is that every rad reads just a little bit differently (although no one uses tile-mode much anymore). For my 30 rads, I need something that will adapt to our various ways of doing things. Many, if not most, other systems have the any-series-any-viewport approach these days. Most can actually handle the linked scrolling of the images, although our older installation of Centricity slows down markedly when windows are linked. Agfa still has its own version...send in the clone windows! Maybe we'll see the "any viewport" thing in Impax 7.x?

1 comment :

Dave27th said...

There is a wizard that can be made in Impax that will allow you to view a CT with 4 different window levels along with displaying the scout in a separate window. As long as one of the images displayed in the wizard window is clicked, the level line will scroll with the image. The scout can be free floating, so it can be placed anywhere on the screen.