Bone Density Reporting and PACS

In our last post, The Evolution of Bone Density Reporting, we looked at how reporting for DXA progressed from manual reporting to cloud based solutions.  We skipped a method of reporting that utilizes Picture Archiving and Computer Systems (PACS).  Many radiologists use PACS for a variety of modalities, including DXA.  We’ll examine bone density reporting with PACS and make comparisons with DXA specific reporting solutions that were discussed in the prior post.

PACS is a key tool used by modern radiology departments.  A typical system consists of a large amount of digital storage, high fidelity DICOM display terminals, and software.  A variety of modalities (digital x-ray, CT, MRI, DXA, etc…) transmit scans to PACS utilizing DICOM.  The images are stored in PACS and can be viewed via DICOM displays.  The amount of storage determines how long images can be recalled and viewed.  After a period of time, images are typically archived and may not be immediately available.

Bone density reporting is often performed with PACS and dictation software.  Typically a radiologist will view a bone density scan on a DICOM display while also dictating or transcribing a report.  This process is consistent with how radiologists create reports for other modalities.

One disadvantage to dictation/transcription is quality.  In our last post we noted quality was addressed with the DXA manufacturer provided reporting software as well as BoneStation.  Bone density scans contain images plus quantitative data, such as BMD, t-score, and z-score.  DXA specific software extracts the data and places it in a report.  With dictation, the radiologist must speak these values in order to transfer them into the report.  This method of transferring numeric data into a report is reminiscent of manual reporting – errors may occur.

It is important to note that the bone density quantitative data is available in two ways within the DICOM transmission.  First, the data is burned into the bone density scan image.  When a radiologist views a bone density image in PACS, it is these values that are transcribed.  There is very little else that can be done with data burned into an image.  Second, and more importantly, bone density data (BMD, t-score, z-score, etc) is also available as values in private DICOM elements.  These values may be extracted, parsed, and placed in a report. Software may read these values and perhaps even aid in decision making.  Calculations, such as change in BMD may be performed in software.  A FRAX risk factor may also be calculated.

We have seen few systems that utilize the values in the private DICOM elements.  PACS is largely used for storing and displaying of images and while it works well with many modalities, it typically ignores BMD data in DXA scans.  The process of dictation/transcription represents a somewhat manual method of transferring the values from the scan into a report.

Another important capability of reading DXA scans is to follow a patient’s progress.  A reader of bone density scans typically compares a current scan with historical scans – by viewing scans side-by-side. Regions of interest (ROIs) are compared for consistency over time.  PACS usually retains images for a certain amount of time.  Historical scans may not readily be available, however.

In summary, PACS is a great tool for modalities that produce images only.  For DXA scans, however, there is a gap in handling of quantitative data that is available in the bone density scans.  In actuality, it lacks the capabilities of even the first generation of bone density software reporting tools.

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