Managing PET-CT Images

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The Integrating the Healthcare Enterprise joint activity by HIMSS and RSNA, which defines profiles based on standards such as DICOM and HL7, just released the new PDI (Portable Data for Imaging) integration profile as one of several supplements in their draft for trial implementation.

This integration profile specifies how images and related information can be exchanged among imaging devices using CDs. In addition, there is an invitation for vendors to participate in an RSNA demonstration. The interesting part of this demo is that attendees of RSNA 2004 will receive a sample IHE-conformant CD with sample medical images and patient information. Vendors participating as so-called IHE Integration profile Media Creator actors also will be able to generate sample CDs on site in their exhibit booths to show their capabilities to create IHE-conformant media. Vendors participating as Media Reader actors will be able to show their capabilities to import IHE-conformant media. RSNA will truly show IHE in action.

The creation of CDs for the exchange of images in a standard, DICOM manner, has been defined for many years. Initially, this was mostly used for niche applications, such as to store cardiology runs, or for cine loops from portable ultrasound. However, this application has become suddenly very popular. The reason is simple: cost reduction. If you have the images available in digital format, burning a CD costs very little, and you can easily train your file room personnel to do it. For example, a major hospital in the Dallas-Fort Worth area will gladly provide a copy of an exam for a

Among the considerations for effectively managing PET-CT images are: how do you deal with raw data? (and how long do you save it?); how will you handle reconstructed images?; and how will physicians access prior studies? For some solutions, read on.

The PET-CT business is booming. Experts predict that sales of PET-CT scanners will overtake sales of PET scanners this year and could completely replace PET scanners in the next several years. As sites clamor to deploy these high-power hybrids, it is critical to develop a plan for handling PET-CT images.

These plans can be logistically and technically challenging. Nuclear medicine departments tend to be distinct entities that aren't necessarily integrated with radiology departments - or enterprise PACS. Unlike other scans which can be reviewed as they load, all data from PET-CT studies must be loaded before fusion images can be generated, which can stress the PACS and network infrastructure. Furthermore, raw PET-CT data is memory intensive (400 to 600 megabytes per study) which can stress even the most powerful PACS. Key questions to consider as the PET-CT image management plan is developed include:

  • Will the site save raw data? If so, how and for how long?
  • How will the hospital provide access to reconstructed data?
  • How will physicians access prior exams for comparison?

Currently, hospitals rely on a variety of solutions for PET-CT image management. The 'right' solution for any given site partially depends on the technology in place. Another key factor, of course, is the budget. Common image management options include CD or optical disk, and many sites do rely on good-old fashioned film for image distribution. PACS, single-modality PACS and network solutions are utilized less often, but do hold promise for streamlining the process, cutting down on film and providing more complete 3D views than film.

RAW DATA: TO SAVE OR NOT TO SAVE

The first image management hurdle to cross with PET-CT image management is the vast amount of raw data this technology brings. With PET-CT scanners yielding unwieldy raw data sets of 400 to 600 megabytes per study, some sites archive raw data with the rationale that physicians may want to reconstruct or fuse images after the initial processing has taken place. Others save raw data for a short time after verifying that reconstructed data meet clinical needs.

Raw data can be a real drag on most PACS, so hospitals rely on other media to save raw data, in the short or long term. The Nuclear Medicine Department at Walter Reed Army Medical Center (Washington, D.C.) saves all raw data from its Siemens biograph PET-CT scanner on CDs. Jaime Montilla, MD, chief of nuclear medicine, says this solution is less than ideal. His primary concerns with the CD approach are long-term survival of data and turnaround time. CDs may degrade over time, and they can be lost or scratched.

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