Evaluation of a selenium-based digital chest radiography system
Preliminary results are presented from an examination of a selenium based thoracic radiography system (Philips Thoravision). The system has been evaluated with four criteria: (1) systems repeatability, (2) digital linearity, (3) spatial resolution, and (4) scattered photon detection fractions. Phantoms were imaged at 120 kV. Repeatability was measured using a polystyrene phantom and evaluating the mean exposure value detected in a region of interest over a period of time. Digital linearity was examined by plotting the output digital value as a function of input exposure. Resolution was evaluated using a line pair phantom. To measure scatter fractions, an anthropomorphic phantom was exposed with a superimposed array of lead beam stops. Three configurations were examined: (1) the selenium system (including an air gap), (2) the system with an added 12:1 antiscatter grid, and (3) a photostimulable phosphor system (Philips PCR) for reference. For a 4 day interval, output varied less than 1%. Digital output of the system was linear with exposure (regression Rvalue of 0.998) over the range from 0.2 mR to 10 mR. The system resolved 2.5 line pair per mm. Resolution was comparable to phosphor plate systems. Scatter fractions were improved when a grid was included.
Floyd, CE; Chotas, HG; Ravin, CEMD
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