Thanks to its ability to provide radiologists with thin-slice MDCT data during interpretation, a thin-client PACS can allow for improved visualization of the adrenal gland and any abnormalities, according to research from Massachusetts General Hospital (MGH) in Boston.
"Thin-client PACS allows maximum exploitation of MDCT technology with easy transition between different slice thicknesses," said Dr. Minal Jagtiani Sangwaiya. "[It] permits radiologists to select slice thickness at the time of image interpretation, [which is] especially [useful] for smaller structures like the adrenal gland."
At MGH, routine abdominal CT studies are typically acquired at 1.25-mm thin slices with a detector collimation of 16 x 1.25 mm. However, interpretation is performed on 5-mm thick-slice data, which can lead to difficulty in visualizing and characterizing adrenal lesions, Sangwaiya said. In addition, storing all of the thin-section data (as well as the thick-slice data) can be problematic for an institution's PACS.
In response, the researchers sought to investigate the utility of using a thin-client, Web-based PACS (Visage Imaging, Andover, MA) in this application. Sangwaiya presented the research during a session at the annual meeting of the American Roentgen Ray Society (ARRS) in April.
The study team randomly selected 51 abdominal CT scans (102 adrenal glands) from March 2008 obtained on a 16-detector-row MDCT scanner (GE Healthcare, Chalfont St. Giles, U.K.) at a detector collimation of 1.25 mm. Images were acquired at both 1.25-mm and 5-mm slice thickness; both sets of studies were then routed to a thin-client PACS viewer.
Two experienced radiologists independently evaluated the adrenals randomly on either 5-mm or 1.25-mm contiguous images during two sessions. In the first session, each radiologist looked at 25 abdominal CT scans with 5-mm slice thickness and 26 abdominal CT scans with 1.25-mm slice thickness. The other sets of images were reviewed in the second session one week later.
The researchers evaluated whether any additional lesions were detected on thin slices, as well as whether there was any change in confidence from thick to thin slices and any improvement of definition in lesions. Readers were also asked to grade their confidence in the definition and characterization of adrenal lesions on thick and thin slices using a five-point scale (1 = definite lesion, 5 = no definite lesion).
For the purposes of the study, a third independent reader who had access to all image datasets, prior CT scans, and clinical information served as the gold standard.
Using the thin-slice data, reader 1 had improved confidence in 10% of the adrenals while reader 2 had improved confidence in 17% of the cases, Sangwaiya said. The first reader's confidence improvement was not statistically significant (p = 0.61), but the second reader's confidence gain was (p = 0.0025).
Reader 1 noted improved definition and conspicuity on the thin slices in three lesions, while reader 2 reported these benefits in 10 lesions. Reader 1 also detected 14 additional lesions (11 true positives), while reader 2 discovered 16 new lesions (15 true positives) from the thin-slice data. Substantial interobserver correlation (r2 = 0.7) was observed when using thin slices, she said.
"Use of thin-slice data enables improved definition of adrenal gland with enhanced detection of subtle abnormalities," she said. "However, thin-slice acquisition must be used with caution [due to a possibility of] overcalling lesions."
Interpretation of routine abdominal CTs with thick-slice data can lead to a substantial number of missed lesions, she said.
"Thin-client systems can help view thinner and thick images without overburdening PACS," she said.
By Erik L. Ridley
AuntMinnie.com staff writer
June 25, 2009
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