Is Migrating Your Annotations Necessary? It Depends…

When considering a migration or an interoperability solution, image annotations are a critical topic. You likely have plenty of images with annotations, but somewhere you’ve heard that annotations can be lost wholesale in migration. Perhaps you’ve not yet considered whether they even need to be saved. Be assured, migration Go Live will arrive sooner or later, so now is the time to assess clinical needs and options.

What are annotations?

Today’s PACS systems make extensive use of annotation and measurement tools. Of course there are the traditional “grease pencil” annotations for the convenience of radiologists and referring physician, but remember that annotations are also used for

  • conveying measurement results with graphics showing calipers and ROI boundaries
  • correcting erroneous laterality markings present in original images.

While numerical measurement results are recorded in diagnostic reports when deemed clinically significant, it is the visual presentation of measurement calipers that’s key for ensuring consistent measurement for trending of progressive disease.  Even more crucial is the need to preserve correction of wrong laterality markings.  Because the stakes are so high, the practice of using annotation to correct wrong literalities has already been discontinued at some institutions, but older images continue to carry this risk. For many PACS administrators, this risk becomes a reality when PACS migration appears on the horizon.

Annotations in migration

Just like the images they apply to, annotations are typically stored as DICOM data objects, whether as Grayscale Softcopy Presentation State (GSPS) or Group 60xx overlays embedded in the images. So why do annotations sometimes suffer in DICOM migration? The answer is twofold: (1) each PACS implements annotations in its own slightly idiosyncratic way, and (2) depending on the PACS, a DICOM C-MOVE migration may capture partial information or no information about annotations.

(1) Implementation differences. The DICOM GSPS standard provides for communication of information as presented on the screen, but the standard does not prescribe the meaning or style of any of the graphics.  Annotation may of course include text content that can convey meaning, but the format, placement and meaning of the text are not conveyed in standard form.  Some PACS vendors have therefore resorted to the use of private tags to convey some of this signification, but no other PACS necessarily honors those tags. Thus the whole meaning of an annotation can be lost in migration even if the annotation itself is preserved.

(2) C-MOVE Making matters worse, some modern PACS systems do not export annotations at all in their DICOM Query/Retrieve (C-MOVE) interfaces. In such cases, specialized migration software tools are required to extract annotations–if annotations are crucial to your migration.

How critical are your annotations?

The key question to ask yourself is: What is lost if annotations or their meaning is not preserved in migration? You’ll find the answer by looking into how your facility has been using annotations all along:

  • Have your radiologists only been using using annotations for the convenience of referring physicians, indicating features of interest that are adequately described in the report? Losing these annotations entirely would be unfortunate, but may not constitute much of a patient safety threat.
  • Have your doctors been using annotations to correct wrong laterality markings? Losing these annotations clearly risks patient safety.

It’s also worth looking at how your current PACS stores annotation information:

  • Are private tags used? If so, could a substantive change in clinical interpretation arise if those tags cannot be honored in your next PACS? Losing these annotations or their meanings clearly risks patient safety.
  • Is annotation information stored in a manner that is fully accessible to DICOM C-MOVE? If so, you may not need to worry about annotation loss in the first place.

Where to go from here

Hopefully you’re already feeling better about your annotations situation, or at least feeling more in control. But if you’re starting to see that your annotations are both clinically critical and potentially endangered, we encourage you to find out more about migration methods that can meet your needs and preserve crucial annotation data. Laitek’s connector-based rapid migration captures annotations from some of the most obfuscated PACS systems and delivers them in clean form to your target PACS. Contact Laitek today about a custom approach for your data.