Digital selenium radiography: detection of subtle pulmonary lesions on images acquired with and without an additional antiscatter grid

Objective: the objective of this ROC-study was to evaluate the diagnostic e fficacy of images acquired with a grid in digital selenium radiography comp ared to that on images obtained with the integrated air gap only. Materials and Methods: seven types of simulated lesions were superimposed onto an an thropomorphic chest phantom. Selenium radiography images were obtained eith er with or without an additional antiscatter grid. For images acquired with a grid either a similar or increased exposure level was used. Both normal and obese patients were simulated. Results: When a grid was used with an eq uivalent detector dose and a higher exposure, diagnostic performance was si gnificantly improved as compared to images obtained with only the air gap. ROC curve areas for mediastinal nodules and catheters were substantially hi gher for images acquired with a grid and the same exposure level compared t o images obtained without a grid However, detection of linear, net-shaped a nd reticulonodular structures in peripheral lung regions was significantly worse when a grid was used with an equivalent exposure level. Concerning th e interpretation of images obtained from the normal and obese phantom model s, no substantial differences were observed. Conclusion: a marked improveme nt in diagnostic performance could be achieved by means of the use of an ad ditional antiscatter grid and an equivalent detector dose. However, when th e same exposure was used, images acquired with the grid allowed a better de tection of mediastinal structures although a worse performance was evident in radiolucent lung regions. Therefore, the routine use of a grid without i ncreased exposure is not recommended. (C) 2000 Elsevier Science Ireland Ltd . All rights reserved.