Standards Watch | Multislice Challenges PACS

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The new generation of higher volume multislice CT scanners is greatly challenging the management of images, the radiology infrastructure, and requires new standards to meet these challenges. That's no secret. Only two years ago, a four-slice CT system was state of the art. Today, facilities are adjusting to the volume of images generated by 16-slice scanners as well as 64-slices that are generated in a third to half a second timeframe. And looking forward, CT manufacturers have 256-slice CT scanners in their development labs.

A PACS is essential in managing multislice CT images. Without PACS to view and archive the large volume of images and data, one might as well forget the purchase of these devices. Among the considerations for effectively managing CT images are throughput, workflow and DICOM support. So, given that we have a PACS, the following challenges exist.

Throughput: Imagine that a complete CT study has to be sent from the ER to a radiologist - who can be in the reading room, at his home and/or office, or even in another city or another continent when nighthawk services are being employed. A high-speed network connection is essential. In addition, potential bottlenecks in the application software become obvious. If a typical study in the past was 200 images, which might have taken five minutes to transfer, a 1,000-image study will than take close to half an hour - which is unacceptable for trauma cases. High-speed network connections using compression are a requirement. Proper configuration of network hubs and routers is getting critical as well. At this time, you may find out that you do not run full duplex, or are sharing bandwidth with other users; it is time to work with your IT department and/or network people to make sure the communication "pipe" you think you have is indeed allocated properly.

Workflow: Several institutions have been using QA stations and gateways as part of their PACS to verify the demographic information and match the CT study with the radiology order. Imagine that all these images are sent to a QA station first where they are verified and then sent along. This might cause unnecessary delay, especially if we are talking about thousands of images. Thus, revisiting the workflow is necessary.

DICOM support: New applications such as CT angiography and others were not envisioned at the time the DICOM standard was written for CT scanners, more than 10 years ago. The "old" DICOM CT definition is based on the old paradigm, whereby images were treated as slices. These new applications are much more efficiently encoded as so-called "multi-frame" objects, whereby the slices are packaged in a single "volume." This has resulted in the definition by the DICOM standardization committee of a brand-new DICOM CT object, similar to what has been done for MR and is being done for cardiology and angiography. It should be expected that vendors will start providing these new objects very soon, and it is highly recommended for users to request the "Enhanced CT" DICOM support.

Image management: How to group and/or split the studies is something that many users wrestle with. The problem is that there could be a discrepancy in the ordering, acquisition, and reporting process of diagnostic imaging procedures, i.e. multiple orders can result in one or more exams, which need to be viewed and reported by one or more radiologists. This is particularly the case for a whole body scan which can cover multiple body parts, such as a head, neck, chest, abdomen and pelvis. These body scans are typically ordered with multiple procedure codes and corresponding Accession Numbers. In the past, when the number of images for an exam were relatively low, say 100 or so, it was manageable for a radiologist to view these on a workstation. However, a neuro specialist who is merely interested in seeing the head images might not want to have to download yet another few thousand images of the chest and pelvis. The handling of these "composite studies" can be handled as follows:

From an order perspective:

  • The radiology information system itself can generate a "master order," with a special, internal CPT code identifying a whole body scan. In addition, the results of this master order can be reconciled with the multiple requests within the RIS.
  • If an institution uses a broker, which translates the HL7 orders into a DICOM modality Worklist, the master order can be provided in the broker, i.e. outside the RIS. This allows a single entry