imaging news

Portable CT goes to ICU patients



Portable CT scanners can now provide valuable abdominal diagnostic information for intensive care unit patients without forcing them to leave the unit, according to a study in the September issue of the American Journal of Roentgenology.

The first portable CT scanners were deployed at several large institutions in the late 1990s. Little is known, however, about their performance and use in addition to cranial imaging, which remains portable CT's main application. Unlike cranial CT, an abdominal scan requires moving patients from their beds onto the scanning table. But portable scans acquired at the bedside can reduce well-documented risks associated with transport of ICU patients to other hospital locations.

Dr. Michael M. Maher and colleagues at Massachusetts General Hospital retrospectively reviewed spiral portable abdominal CT scans from 107 patients obtained between June 1999 and December 2000. They compared portable CT's image quality and diagnostic value with that of available stationary CT scans.

Although image quality from portable abdominal CT did not match stationary CT, the researchers found they were able to obtain important diagnostic information without moving patients from the ICU.

Researchers obtained 122 portable and 41 stationary CT scans, with 47 and 15, respectively, enhanced by contrast. Intravenous contrast improved portable CT scan quality. Quality scores for portable CT scans, however, were consistently lower than those for stationary CT, both with and without contrast.

Findings on portable CT confirmed 33 conditions suspected before scanning. Portable scanning also detected evidence of infection in 18 patients and hemorrhage in 16, led to seven laparotomies and six percutaneous drainage procedures, and influenced a change in patient management in 33 cases. Surgery or autopsy results confirmed portable CT findings in 12 of 17 cases.

The spiral portable CT scanning protocol included two 285 to 355-mm-long volumes acquired with 5-mm slice thickness during 70 sec at 120 to 130 kVp, 30 to 40 mAs, and a 1 to 1.5-sec pitch. Patient condition and imaging indication determined IV contrast use. Stationary scanning was performed with single- and four-detector spiral scanners.

Interpretation of portable CT studies must proceed with caution, however. Some portable CT parameters, such as accuracy and negative predictive value, were unknown. While portable scanning is useful in many cases, patients who require valuable diagnostic information should be moved to more sophisticated imaging installations whenever possible, researchers said.