DTS clears up chest lesion questions left by x-ray, may curb follow-up CT

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 - digital tomosynthesis
A 45-year-old woman with a focal ectasia in the left chest cavity that was incorrectly identified as a pulmonary lesion on chest radiography. (a) Posteroanterior chest radiography in the upright position shows one suspected pulmonary nodule in the left lung (arrow). (b) Digital tomosynthesis image clarifies that the same opacity was due to vascular ectasia.
Source: Acad Rad 2013;20:546-553

Digital tomosynthesis (DTS) could be utilized as a companion study to chest x-ray radiography (CXR) for imaging suspected thoracic lesions, as it resolves doubtful CR findings in roughly three-quarters of cases without the need for follow-up CT, according to a study published in the May issue of Academic Radiology.

“In this study, DTS proved to be decisive in confirming or ruling out the vast majority of pulmonary lesions and to differentiate true pulmonary opacities from those due to pleural or thoracic wall lesions or pulmonary pseudolesions, with a clear improvement in diagnostic accuracy, confidence, and interreader agreement in comparison to CXR and with a modest increase in the radiation dose and interpretation time,” wrote Emilio Quaia, MD, of University of Trieste, Italy, and colleagues.

True pulmonary lesions can be difficult to differentiate from pseudolesions because of their small size, explained the authors. Pseudolesions result from other anatomical structures mistaken for pulmonary lesions, such as overlapping bone structures, vascular kinking, osteophytes, among others. Up to 20 percent of suspected pulmonary nodules on CXR could represent other lesions, according to Quaia and colleagues.

Because of this challenge, radiologists often report doubtful or equivocal findings and suggest further evaluation on CT, with its added costs and radiation exposure.

To assess whether DTS could help exclude potential lesions on CXR, the authors conducted a prospective study of 465 patients, average age of 72 years old, with suspected thoracic lesions. All patients underwent DTS in addition to initial onsite CXR, and two independent readers analyzed images on a 1-5 scale as definite benign lesions, definite pulmonary lesions requiring further workup, or indeterminate.

Results revealed a total of 229 pulmonary lesions and 236 pseudolesions, and DTS allowed readers to correctly classify the vast majority of these lesions. Quaia and colleagues reported 73 percent of 465 doubtful CXR findings were resolved by DTS, meaning the need for CT was reduced to 27 percent of the 465 patients who would have otherwise undergone CT.

The authors noted that while DTS is similar to CT, it delivers a lower radiation dose and can be easily implemented in conjunction with CXR as it uses the same equipment.

“For the radiologist, DTS studies took longer to read than CXR, principally because of multiple image scrolling, but the overall interpretation time was lower than CT because of the lower number of images evaluated,” wrote the authors. “Even though DTS increased the interpretation time, it could be easily introduced in the routine diagnostic workflow as a case-solving technique in those patients with suspected or equivocal pulmonary lesions on CXR.”