Tutorial: Re-Associating DICOM Objects


Sometimes your DICOM objects may not be associated correctly, causing an errant hierarchy of data objects in the patient module. This article explains why that might happen, and how you can use built-in tools to rectify it.

DICOM Object Associations

Within a patient record, ProKnow will automatically determine the associations of DICOM objects (e.g., image set, structure set, plan, and dose) based on the file content. These associations will determine the default organizational hierarchy within a patient record, such as:

  • The image set to which an RT Structure Set is assigned
  • The RT Structure Set to which an RT Plan is assigned
  • The RT Plan to which an RT Dose is assigned

A typical hierarchy in ProKnow's Browse module will look like the following figure. Notice that the root object is the image set under which is organized the RT Structure Set, RT Plan, and RT Dose.


What Causes DICOM Associations To Be Broken?

If DICOM associations in the DICOM source files have been broken (or are wrong or invalid), then you will not see DICOM objects as you expect in the patient module. The most common error is if an RT Plan is not associated with the RT Structure Set, but you can also have failures of an RT Structure Set to be associated with its image set, or RT Dose with its plan. This will result in failure to be able to analyze your data. For instance, structures will not be displayed with the imageset, or DVH data will not be calculated if an RT Dose is not downstream of an RT Structure Set.

If you transfer data directly from your TPS (or other system), you will not see this problem unless there is an error in how that system writes DICOM data.

If errors are found, it is most often because some data have been stripped from or changed in the DICOM files after their creation (e.g., a poorly designed anonymization/de-identification process can sometimes break DICOM associations). If this happens, you can establish entity associations across multiple patients at once or manually re-associate the objects from the patient module.

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