Mammography Acquisition Workflow - Detailed Proposal

1. Proposed Profile: Mammography Acquisition Workflow

• Proposal Editor: John Paganini/Ron Hitzelberger
• Profile Editor:
• Date: N/A (Wiki keeps history)
• Version: N/A (Wiki keeps history)
• Domain: Radiology

2. Summary

Mammography Acquisition Workflow is about handling scheduled and unscheduled image acquisition in Mammography. Acquired images serve as input to potentially any other subsequent event such as post-processing/ CAD, interpretation/ reporting, and billing. Optimal integration of acquisition steps into the overall workflow is critical.

After initial image acquisition re-takes, additional views or CAD results may be appended to the imaging study subsequently. Studies are not complete until the Radiologist is satisfied.

There are common practices in digital mammography which can have a wide variety of workflow results. Despite technical means defined in the Scheduled Workflow and Mammography Image Profiles, variances in the way users and systems behave can lead to department inefficiencies, ambiguous data, special cases for automated billing, and less than optimal acquisition and reading environments.

Because additional views are common in mammography, there is no easy, practical mechanism within mammography to declare a scheduled procedure complete. Performed Procedure Steps can continually be added to a study. MPPS complete messages and PACS distribution mechanisms can inhibit access to images, CAD result reports, and study annotations. Inconsistent study statuses and study structures have also been an issue with many PACS.

Different implementations of workflow functions and semantics can be reduced by guiding or defining which data and semantics is exchanged and used by interacting systems. IHE can facilitate the exchange of information required for efficient workflow especially for solving the problem of additional views. One approach might be to define how to apply more generalized Scheduled Workflow use cases (e.g. Append Case) to mammography practices. IHE may re-use existing IHE work, add IHE specification based on existing standards, or identify gaps in standardization that could be handed off to the appropriate resources (i.e. DICOM committees).

3. Use Cases

1. A patient comes in for a screening mammogram which is converted to a diagnostic exam upon the technologist discovering a lump. The technologist adds an extra view, but no exam type, so the hanging protocol at the workstation is unacceptable.

• Additional views may effectively change the type of the exam (i.e. screening to diagnostic, or uni-lateral to bi-lateral). The resulting final exam type is not evident to systems and users.

2. A radiologist views a screening exam and toggles on CAD which indicates findings. The radiologist requests additional images to better demonstrate the abnormality. Should the technologist add the views to the existing order? Does it depend upon whether or not the patient is still available for imaging that day? How should the exam type (and billing) change from screening to diagnostic if this is necessary?

• Using another study or accession number to add the views leads to archiving, billing, and display presentation problems.

3. A patient comes in for a follow-up exam on one breast. Since she is close to her yearly exam date, the radiologist calls for imaging of the other breast too, while the patient is waiting. The original room is unavailable, so another machine is used. The technologist generates a new study and accession number. The right and left breasts do not hang together at the diagnostic workstation. The following year, the prior images are hung as two prior studies, not as one complete comparison study.

• Additional views can later be mistaken for complete prior exams.

4. The technologist labels a view incorrectly and doesn’t realize it until after the case is completed and sent to PACS. The view information is corrected at the acquisition modality and resent. The images do not hang properly on the workstations and multiple copies of the same image exist, one which is labeled incorrectly.

• Additional views may be data corrections or retakes on previously acquired views. Image Managers and Workstations do not have a mechanism to understand and properly treat images produced as a result of such conditions. • Additional views may generate additional CAD result reports. This creates confusion as to which objects should be considered for case level processing and which CAD reports should be considered when reading.

5. A PACS will not distribute images until a study is complete. A technologist wants the radiologist to view the images before completing the exam. The radiologist can not access the images from the local workstation.

• Some workstation behaviors are incompatible with the needs of mammography, such as not allowing the addition of images to studies that are open or have already been viewed.

6. CAD objects and markups are persistant. Many sites want to have them available until after the study is completed then they no longer wish to keep or store them.

• ACR does not require that mammography facilities archive CAD objects and image markups (overlays or Presentation States). • PACS vendor assumes responsibility. • Deletion is possible based on SOP Class but maybe there is a better way to deal with this situation.

7. Study objects (images, CAD SR, digitized films) for the same patient can arrive at a PACS from multiple stations, creating a ‘mixed’ station name.

• Mixed station names complicate the ability to address the individual needs of stations, i.e. body part mapping, specialty mapping, compression and archiving, etc

8. Not all mammography modalities create markers that are ‘burnt’ into the image data per the ACR QC Manual. It states that the view and laterality should be placed on the image near the axilla.

• Radiologists are used to the ‘look’ of conventional markers and dislike the variability that exists. They prefer that this information is not hidden amongst other demographic information.

9. Workstations often include a means to indicate to a radilogist that there are additional views during dictation.

• A standardized means of indicating wheteher images, objects, and presentation states have been viewed would be useful to radiologists one they begin dictation.

4. Standards & Systems

Existing standards and mechanisms to consider include:

• DICOM <Be specific>
• Existing IHE profiles, actors, and transactions <Be specific>

Existing systems that could be involved in the problem/solution include: FFDM modalities, Mammography CAD servers, Diagnostic and Technologists’ workstations, PACS, and RIS.

5. Technical Approach

<This section can be very short but include as much detail as you like. The Technical Committee will flesh it out when doing the effort estimation.>

<Outline how the standards could be used/refined to solve the problems in the Use Cases. The Technical Committee will be responsible for the full design and may choose to take a different approach, but a sample design is a good indication of feasibility.>

<If a phased approach would make sense indicate some logical phases. This may be because standards are evolving, because the problem is too big to solve at once, or because there are unknowns that won’t be resolved soon.>

Existing actors

<Indicate what existing actors could be used or might be affected by the profile.>

New actors

<List possible new actors>

Existing transactions

<Indicate how existing transactions might be used or might need to be extended.>

New transactions (standards used)

<Describe possible new transactions (indicating what standards would likely be used for each. Transaction diagrams are very helpful here. Feel free to go into as much detail as seems useful.>

Impact on existing integration profiles

<Indicate how existing profiles might need to be modified.>

New integration profiles needed

<Indicate what new profile(s) might need to be created.>

Breakdown of tasks that need to be accomplished

<A list of tasks would be helpful for the technical committee who will have to estimate the effort required to design, review and implement the profile.>

The original profile proposal, “Mammography Acquisition and CAD Workflow” has been separated into two different IHE proposals, although there are several overlapping concerns.

The following options and issues need to be clarified and resolved:

• What mechanisms solve which part of the problem:
  • Dataflow: reliably get images to a CAD box, workstation, PACS, etc. This includes clarifying the data lifecycle, e.g. retaining acquired images (or relevant data) on the modality so that in the append case, this previous Study and Procedure information can be re-used.
  • Workflow: tell another system to do something, including references to input data. Which systems query for worklists (CAD worklist)? Which systems send and receive work status (MPPS to CAD and PACS)?
  • Internal logic of querying/ sending and receiving actors in order to determine when all images are available. For instance, compare MPPS references to available images, or query/ send image availability status.
• Besides specifying technical solutions, how valuable is it to describe the different Mammo-specific workflow scenarios informatively for education? This is especially relevant as it does not seem realistic to assume that IHE Technical Specifications can solve all variability in the field. Thus, users and vendors need to know how local practices and habits impact system use and departmental efficiency.
• In acquisition and subsequent steps - how to access the images:
  • Pull: query/ retrieve, e.g. by CAD. This implies that PACS is required to retrieve images that match the query, irrespective of "Study complete" internal logic.
  • Push: store to one/ more receivers. This implies that the modality has internal logic to know when to send images or appended images, e.g. by using a waiting queue, by providing an interactive function for a user to manually send images.
• For Workflow: prefer re-use and established things.
  • SWF
    • normal case - for scheduled acquisitions without re-takes or additional views
    • unscheduled case - is it relevant in Mammography at all?
    • append case - for re-takes or additional views (unscheduled or scheduled cases)
    • group case - is it relevant in Mammography at all?
  • There are no other relevant IHE workflow profiles to be reused for acquisition workflow (PWF, RWF do other things).
  • If Modality Worklist and SWF do not solve the Mammo acquisition problems, is it worth while looking for less-established mechanisms? E.g. opportunities and risks of using UPS (still not finalized); dataflow (push images and MPPS to CAD).
• Study complete - define the concept, i.e. relation of MPPS and "all images available". Only a human user can finally reliably state that a study is complete. If additional views are taken at a 2nd, different modality, does IHE need to cover this case (is it 80% routine?)? If a CAD system receives an MPPS from one modality, how sure can it be that there won't follow another MPSP from a 2nd modality notifying the CAD box of additional images/ views?
• Exam type - clarify what this means exactly (screening <--> diagnostic). What are implications and required behavior?

6. Support & Resources

<List groups that have expressed support for the proposal and resources that would be available to accomplish the tasks listed above.>

7. Risks

<List technical or political risks that will need to be considered to successfully field the profile.>

8. Open Issues

<Point out any key issues or design problems. This will be helpful for estimating the amount of work and demonstrates thought has already gone into the candidate profile.>

9. Tech Cmte Evaluation

<The technical committee will use this area to record details of the effort estimation, etc.>