Abstract: A linear array silicon pixel detector has beendeveloped to perform digital radiology with synchrotronradiation: in this communication we present the firstresults obtained using a three layer prototype at theElettra Synchrotron Radiation Facility (Trieste,Italy). High efficiency (about 85% at 20 keV) isachieved by means of an Si strip detector irradiated inan 'edge-on' geometry: the pixel dimensions are 200$MUL 300 micrometer$+2$/. To obtain a sensitive area ofabout 50 $MUL 1 mm$+2$/ stack of three layers has beenassembled. Images are obtained by means of scanningtechniques and their spatial resolution is determinedby the scanning step. Detectors are read-out bydedicated, low noise VLSI CMOS chips in single photoncounting mode. The distance between each detector layerhas been measured to be 115 plus or minus 10 micrometerand the layers are parallel within a maximum tilt angleof 0.08 degrees. Cross-talk effects were found to bealways smaller than 2% of the counts of the neighboringlayers. The MTF in the scan direction has beenevaluated. The acquisition time needed to acquire animage of a mammographic test object is about 6 minutes.The mean glandular dose is about 30% of the dosedelivered at the conventional mammographic unit for thesame test object while the detail visibility iscomparable. These preliminary results indicate that alarge area linear array silicon pixel detector can bedeveloped: using this detector and a monochromaticsynchrotron radiation beam the delivered mean glandulardose is significantly reduced when compared toconventional mammographic examinations. !22
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