My PET/CT Experience: Adding a New Modality to PACS

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It was a Tuesday afternoon when I received the call. The new PET/CT scanner was installed, and acceptance testing was about to begin, but my medical physicist informed me that PACS was not listed as a destination. The installation team had not configured the scanner to communicate with PACS. Not too concerned, I asked to speak with the modality vendor’s field service engineer (FSE), who was working on-site. A sinking feeling set in as I learned that he was new to the company, and that he did not know how to set up DICOM.

The first question posed by the FSE was whether we had purchased the required licenses for the DICOM services that I was requesting. Confidently, I replied, “Yes.” My purchasing agent had called me during the contracting phase to ask what requirements needed to be included for PACS. I provided my typical list: DICOM Modality Image Store, DICOM Print, Modality Worklist, Storage Commitment, and Modality Performed Procedure Step. Unfortunately, there was no Integrating the Healthcare Enterprise (IHE) specification available during the procurement phase, so IHE-compliance statements were not included in the purchasing contract.

Next, the FSE asked the standard questions that had already been provided to his preinstallation team via email: “What is the make, model, and software version of your PACS?” That was immediately followed by, “What is the IP address assigned for this scanner?” These questions were answered quickly. I then requested that the Application Entity Title (AET) be defined according to a naming convention that I established as a standard a long time ago. I also asked if the computer’s station name could be named similarly.

The FSE called his technical support with the information, and was able to begin work on the DICOM setup later that afternoon. I was told that the computer’s station name cannot be changed. There are other components in the scanner that have been set up using this name and so it must remain as defined. I learned that I must live with s37gikx22789chlmc23 as a station name. The good news was that the AET can be customized, so the AET is set up according to convention. My naming convention includes the general location of the device, a vendor identifier, modality identifier, and a number as a counter (for example, ERVENDRNAMCT3).

The modality was configured to communicate with the PACS test server and vice versa. Connectivity testing was performed, and the testing went smoothly. The DICOM syntax was set up to negotiate using DICOM Implicit Little Endian, and soon data were being stored on the test server. A check of the DICOM image header indicated that all the DICOM tags needed for my site’s PACS workflow were filled in, and so these studies should follow established PACS workflow nicely. A check of the image data was unremarkable. The PET/CT scanner was set up to communicate with production PACS.

The production DICOM installation went smoothly, and acceptance testing was completed successfully. With applications personnel on-site, training of our technologist staff began.

It didn’t take long to notice that the DICOM worklist did not include all of the scheduled patients being examined on the scanner. The worklist had been set up so that only ordered PET/CT studies were listed whenever a worklist query was performed from this scanner. This was not enough. The worklist also needed to include other scheduled studies that were converted from the initial request to a more appropriate PET/CT study. The worklist was modified to include studies that were scheduled on our more generic PET scanners.

Acquisition Issues

The acquisition procedures developed on a new modality typically start out conservatively. At first, routine procedures are defined using familiar acquisition parameters, with some adjustments made at the recommendation of applications personnel. Once a new modality is familiar to both the technologists and the radiologists, changes in procedure often follow. Most changes are typically accommodated well by our PACS, even as some study sizes have increased to thousands of images per study. Once in a while, however, a new challenge presents itself.

The PET/CT scanner had been online for some time, and studies were flowing through our PACS fairly seamlessly (except for the occasional study set of 7,000 or more images). Then a new research protocol was developed. This protocol included the acquisition and storage of PET list mode data, and a request was made