Relevancy rules: Workflow applications

Managing cache space with prefetching

For administrators, relevancy rules help manage cache space on the computers by automatically prefetching prior studies that are considered relevant. This makes the most relevant studies quickly available to radiologists without overloading the system with priors that are likely not useful for diagnosis. Radiologists can work more quickly because when they sit down to interpret, the possible relevant priors are already available on the system instead of sitting in offline media, for example.

PACS Administrators must balance the need to reduce network traffic and cache space with the clinical requirements of radiologists. Some radiologists require very specific relevancy rules. For example, when radiologists are focusing on studies from oncology patients, prior studies from far different modalities and body parts are often considered relevant. This creates a situation in which many studies are considered relevant, increasing network traffic and the amount of cache space required for prefetching.

For all prefetching, the relevancy rules are defined in the Relevant Priors Manager in the Administration Tools. For details, refer to "Relevant Prior Manager" (topic number 9480) in the Administration Tools component of the IMPAX 6.5.1 Server Knowledge Base.

Managing large numbers of priors

After all the relevant priors have been prefetched using the rules defined in the Administration Tools, radiologists can further accelerate access to relevant priors by setting relevant priors to open automatically when the current study for the patient is opened or cycled to. PACS Administrators define relevancy rules for roles or users through the Configure area - Preferences section.

Understanding the relationship between Administration Tools and Client relevancy rules

The relevancy rules defined in the Relevant Priors Manager in the Administration Tools and in the Configure area in the Client, affect which priors are displayed for a patient and how fast. The following workflows outline this relationship.

Relevancy rules not defined in Administration Tools, but defined in the Client

1. In the List area, set relevant priors to automatically open by clicking the Relevance button.

2. Cycle a worklist.

   The current study opens in the Image area, along with all of its relevant priors as defined by the rules in the Client. This happens much more slowly than in the previous case, because the priors have not been prefetched. If studies are still being retrieved for a patient in the Image area, a little clock icon appears next to the patient name on the bottom navigation bar.

Relevancy rules defined in Administration Tools and in the Client

1. In the List area, set relevant priors to automatically open by clicking the Relevance button.

2. Cycle a worklist.

   The current study opens in the Image area, along with all of its relevant priors, as defined by the rules in the Client. If any of the cycled studies are from modalities or specialties not defined by Client rules, priors are opened according to any applicable rules in the Administration Tools. The relevant priors defined in the Administration Tools open more quickly because they were prefetched.

   For example, if a relevant prior rules is set up in the Client for CT/any specialty, that rule is used for all CT studies, and any Administration Tools rules are ignored. However, if rules are set up in Administration Tools for all other modalities, those rules are applied to non-CT studies.

Understanding that relevancy rules are non-merged

Relevancy rules can be inherited by a user from the role that user belongs to. But relevancy rules are non-merged. This affects at which levels, and which rules, administrators implement. For example, consider the following hierarchy of roles and users:

- Radiology        

    - Resident

        Chris Dels

If the Radiology role is assigned relevancy rules, but the Resident role and the user, Chris Dels, do not have rules assigned, they inherit the rules from Radiology. If you then assign relevancy rules to the Resident role, the Radiology rules no longer apply to the Resident role, and Chris Dels inherits the rules from the Resident role instead.

So, administrators can assign relevancy rules to a role, such as Radiology, but if a sub-role, such as Resident, has even more specific needs, the administrator must duplicate the applicable relevancy rules from the Radiology role at the Resident level.