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Wednesday, December 04, 2013

Digital Tomosynthesis Improves Lung Nodule Detection

James T. Dobbins III, Ph.D.

Digital tomosynthesis (DT) is significantly more sensitive than conventional radiography at detecting lung nodules and its advantages are evident among general radiologists as well as thoracic radiologists, according to a study presented Tuesday.

DT is a relatively new technology that uses X-rays to create slice-based views from inside the body. Previous studies have shown that it is more sensitive than radiography at detecting lung nodules, but those studies have largely relied on radiologists with expertise in thoracic imaging, said James T. Dobbins III, Ph.D., associate professor of radiology at Duke University.

For the new study, Dr. Dobbins and colleagues had both thoracic and general radiologists assess DT and radiography referenced to CT for the detection of lung nodules. The study group included 158 subjects at three institutions in the U.S. and one in Sweden who were imaged by chest CT, two-view conventional radiography (CXR), dual-energy radiography (DE), and DT on a flat-panel imaging device.

Three experienced thoracic radiologists confirmed the presence and location of nodules by CT and determined the appropriate management approach using Fleischner Society guidelines, rules created to improve follow-up and management of small lung nodules detected by CT. In addition, five general radiologists marked the nodules and then determined the appropriate course of action using CXR alone, CXR plus DE, DT alone, and DT plus DE.

In all, 516 nodules were identified by CT. Overall detection sensitivity for all nodules was 3.8 percent for CXR, compared with 13.5 percent for DT. "The threefold improvement in sensitivity with tomosynthesis is consistent with previous studies," Dr. Dobbins noted. "What's unique about our study is that we're including the role of dual-energy imaging and also looking at a broader range of expertise among radiologists."

DT also outperformed CXR for determining the best course of action using Fleischner Society criteria. The addition of DE improved nodule detection when paired with CXR but not when paired with DT.

"Our results clearly demonstrate that tomosynthesis is far superior to conventional radiography for looking at lung nodules," Dr. Dobbins said. "DT shows significantly improved clinical performance over CXR for pulmonary nodule detection and case management when evaluating nodules greater than three millimeters in diameter."

The clinical role for DT is still evolving, Dr. Dobbins said, as researchers try to determine the best implementation strategy. One promising option for DT is as a problem-solving tool for suspicious findings on radiography. Dr. Dobbins said this attribute would be particularly useful in healthcare environments where patients remain in the clinic until imaging results are complete.

DT also has a potential role as an alternative to CT for tracking changes in nodules over time, although further studies will be required to validate that approach. "While DT has marginally higher radiation doses than two-view chest radiographs, it exposes the patient to considerably less radiation than the current generation of CT techniques," Dr. Dobbins said.

A third, speculative application would involve using DT as a lower dose, lower cost lung cancer screening paradigm, he suggested. "We'll need to demonstrate outcomes comparable with CT before that can happen," he said.

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© 2013 RSNA. The RSNA 2013 Daily Bulletin is the official publication of the 99th Scientific Assembly and Annual Meeting of the Radiological Society of North America. Published Sunday, December 1 - Thursday, December 5.

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