Stereotactic Breast Imaging - Brief Proposal

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1. Proposed Workitem: Stereotactic Breast Imaging

  • Proposal Editor: Paul Morgan / DICOM Working Group 15
  • Editor: DICOM Working Group 15 (Mammography and CAD)
  • Date: N/A (Wiki keeps history)
  • Version: N/A (Wiki keeps history)
  • Domain: Radiology


2. The Problem

Stereotactic Breast Imaging is a technique using “stereo” pairs of X-ray exposures acquired at predetermined angles to one another for a radiologist (breast imaging physician) to ascertain the proper placement of breast biopsy instruments. Review of the images (2D projections) as related pairs is critical to determining the target tissue’s 3rd dimension (“Z coordinate”), providing the radiologist’s confidence in the accurate placement of the biopsy instrument, and in the effectiveness in removing the correct target tissue.

Currently, only the vendor-dependent acquisition stations for the Stereotactic imaging systems permit selection and display of image pairs. Lack of DICOM header information currently results in limited ability to archive the necessary information and to optimally visualize these images on downstream workstations, with respect to hanging protocols, image enhancement, and targeting information.

Users desire interoperability between Acquisition Modalities, Image Manager/Archives and Image Displays.


3. Key Use Case

A patient is scheduled for a Stereotactic Breast Biopsy procedure for the extraction of a suspect mammographic abnormality (e.g., microcalcifications). During the procedure, the technologist acquires stereotactic paired digital mammography images on the modality at prescribed plus and minus angles to a scout image. The radiologist utilizes these images to determine the location coordinates for introduction of a biopsy instrument and extraction of tissue from the site of abnormality. Additional stereo paired images are obtained to confirm needle positioning, subsequent placement of a tissue marker, and documentation of successful extraction of the targeted tissue. These image pairs are commonly referred to as “Scout”, “Pre-fire Plus / Minus”, “Post-fire Plus / Minus”, “Post-biopsy Plus / Minus”, “Post-marker Plus / Minus”, and single Post-biopsy or Post-marker images. After the procedure is completed the images are archived. If there is subsequent question as to the accuracy of removal of the targeted abnormality, a radiologist needs to be able to view these images on a non-modality workstation for problem-solving and/or second opinion. In order to provide for second opinion at a non-performing institution, optimal digital data is currently not available for transfer and display.

In order to maintain a record of the procedure and its outcome, one current known workaround is to print the stereo paired images on a film printer from the modality, where the film contains the targets and image enhancement. The films are scanned into DICOM Secondary Capture Images and archived on a PACS, with some degradation to the information due to scanning.

The modality should record the Image Type values defined in the DICOM Digital Mammography X-Ray Image IOD for identifying the stereotactic images. They should then be stored to the PACS and to the Image Display, where they can be hung as pairs and sorted using their Image Type identifiers. In addition, the targeting information and image enhancements applied at the modality should be recorded for downstream display.


4. Standards and Systems

In 2009, DICOM’s Working Group 15 introduced identifiers for each of the well-known exposures used in stereotactic imaging (CP-889, additional to DICOM 2008). These were defined as Enumerated Values to be placed in the third value of Image Type (which for non-stereotactic images continues to be specified as NULL).

Three additional identifiers are defined in CP-1250, currently in work, to distinguish micromarker placement images from other post-biopsy, which previously was not deemed necessary. (CP-1250 also introduces changes applicable to Breast Tomosynthesis, which are not pertinent here)

In addition, a new DICOM CP is drafted (Sep. 2012) that proposes additional attributes for the exchange of target information, which will enable visualization on the Image Display.


5. Discussion

The functionality desired is essentially the same sort of refinement and clarification provided by the Mammography Image profile, but at that time the need for stereotactic imaging interoperability was not as pressing. In addition, the profile was defined before CP-889 was submitted.

It is desired that a new Integration Profile be developed that focuses on the Acquisition Modality’s population of image attributes and the Image Display’s utilization of those attributes. The requirements will reside primarily in the Modality Images Stored and Retrieve Images transactions. Other system interactions (e.g., SWF, print) will be considered.

Recognizing that Stereotactic Breast Imaging seems like a logical extension to MAMMO, perhaps as an Option, it is a specialized clinical practice that is separable from the core business of breast imaging. It is important that the required interoperability solution be clearly marketable by IHE and its proponents in the Breast Imaging community, something named options cannot provide.

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