Radiation dose in digital chest radiography: comparison among three technologies

To compare the Entrance Surface Dose (ESD) for a normal patient, measured on three types of dedicated digital equipment for chest radiography: an amorphous selenium system, a CR (Computed Radiography) system, and a system for direct radiography (DR) based on an amorphous silicon active matrix (a-Si) connected to a CsI(T1) detector.

The ESD values were measured with different dosimeters placed in the air parallel to the detector plane, and at a distance equal to the thickness of a normal-build patient. The measurements were taken with the radiological parameters (Posterior-Anterior projection (PA) and Lateral projection (L)) used in diagnostic practice to obtain high-quality diagnostic radiographic images. The measurements taken with the DR equipment were repeated after the manufacturer added a 0.2 mm-thick Cu filter. The ESD values obtained by this series of measurements were reported as mean and standard deviation values (M+/-SD).

With the PA projection, the doses measured for the different devices were the following: amorphous selenium system 0.12+/-0.06 mGy, CR system 0.3+/-0.05 mGy, DR system 0.05+/-0.02 mGy. With the L projection: amorphous selenium system 0.40+/-0.13 mGy, CR system 0.9+/-0.17 mGy, and DR system 0.21+/-0.15 mGy.

The use of digital systems allows a significant reduction of the patient dose. In particularly the Direct Radiography system, based on a CsI/a-Si detector, administers the lowest patient dose.