Importing outside studies into PACS avoids repeat imaging

By Erik L. Ridley, AuntMinnie staff writer

December 26, 2011 -- Repeat imaging studies can add unnecessary cost and radiation dose for patients. Importing outside imaging exams into PACS can significantly improve the odds of avoiding this source of overutilization, according to research from the University of California, San Francisco (UCSF).

In a retrospective review of 267 patients referred to their institution for transarterial chemoembolization (TACE), UCSF researchers found that only 11% of patients who had their outside imaging studies imported into PACS had a repeat study. In contrast, repeat imaging exams were performed in 72% of patients who did not have their outside imaging studies available and in 52% of patients who had outside imaging studies available but did not have them imported into PACS.

The American Board of Radiology has identified repeat imaging at the transfer of care between institutions as a key source of overutilization, and one solution to this problem is to import outside imaging studies into PACS, said Dr. Michael Lu. He presented the team's findings during a scientific session at the recent RSNA 2011 meeting in Chicago.

At UCSF, outside imaging studies have been imported into PACS since late 2006. Both the number of outside studies that are imported and the percentage of imported studies in comparison with exams performed at UCSF have doubled over the last three years, Lu said.

"And now, around 15% of the imaging studies that are archived to PACS each month are from the outside," he said.

While not every institution imports outside imaging exams, most radiologists would likely prefer to look at outside studies on their own PACS, Lu said.

"Once the imaging is imported, it's available enterprise-wide using a fast, familiar user interface," he said. "And the outside studies will never walk off in a ... pocket; they'll be a permanent part of that patient's electronic medical record."

To convince institutions that they should import outside studies to PACS, it's important to show clinical benefit to patients, however. In research published in the August issue of Radiology (Vol. 260:2, pp. 408-413), researchers from Brigham and Women's Hospital found that patients transferred to their emergency department had a lower rate of subsequent image utilization if their images were able to be imported into PACS from CDs.

The UCSF team sought to analyze the benefit of importing outside imaging studies for outpatients who come to the institution for a surgical procedure. In a retrospective review, the researchers studied 267 patients who had an abdominal CT or MR exam within four months of receiving TACE for treatment of hepatocellular carcinoma (HCC) at UCSF.

This group was chosen due to its homogenous nature, offering a common imaging workup (multiphase abdominal CT or MR) for the same disease (HCC) prior to a clear end point (TACE), Lu told AuntMinnie.com. This study population also allowed the researchers to assess the common situation in which outpatients are referred to the institution for a procedure.

The 267 patients were divided into four groups based on the availability of their outside imaging exams:

  1. Outside imaging studies unavailable
  2. Outside imaging studies available on CD or film but not imported
  3. Outside imaging studies imported to PACS
  4. No outside imaging studies (a control group who had all their imaging performed at UCSF)

The researchers then compared the rate of repeat CT or MRI exams between the four groups within four months before TACE. A second imaging study was not considered to be a repeat imaging exam if it was performed for a new, acute indication or because the original was judged to be technically inadequate.

Repeat imaging rates:

  1. Outside imaging studies unavailable: 13/18 (72%)
  2. Outside imaging studies available but not imported: 14/27 (52%)
  3. Outside imaging studies imported to PACS: 9/79 (11%)
  4. Control group with no outside imaging studies: 18/143 (13%)

Patients with outside imaging studies that were imported were significantly less likely to have repeat imaging than both groups whose outside exams were not imported (p < 0.001). The repeat imaging rate was similar to the control group that didn't have any outside imaging studies (p = 0.79).

In further statistical analysis that adjusted for potential confounders such as referring institution and the size and number of lesions, the group with imported studies had significantly lower odds of repeat imaging than both groups with unimported outside imaging (odds ratios [OR] 31 and 9.0, both with p < 0.001), Lu said. The odds ratio was similar to the control group (OR 0.71, p = 0.51).

"We hope that our results help inform institutions considering implementing import to PACS," Lu said. "Vendors should adhere to DICOM and IHE [Integrating the Healthcare Enterprise] standards to ensure that the portable media they generate is importable."


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