A Linear Scanning Digital Radiographic System for Chest lmaging

Abstract

A linear scanning digital radiographic system was developed using photodiode array as a detector. Images are collected using this linear photodiode array sensor of 1024 pixels after X-ray photons are converted to light photons by the image intensifying screen. Sensitive area of each photodiode cell of a linear array sensor is 0.63 mm by 1.3 mm. This linear array sensor scans with 0.65 mm increments along the scanning axis using a DC servo motor to form 1024 lines of image within 0.7 sec of scanning time. A fore-slit, located between the X-ray tube and the patient, converts an area beam to a fan beam and reduces the patient exposure and scattering effect. Also, this fore-slit scans syncronously with the detector assembly. Detected electrical signals are integrated to enhance the efficiency of X-ray exposure and multiplexed to four serial streams representing detected values of linear array. Then, it is calibrated to compensate for X-ray fluctuation, uneven sensitivity and bias of each pixel. Collected images are ND converted with 12 bit resolution, transferred to the computer and displayed on a high resolution monitor. Images can be processed by the image processing algorithms and all parts of the system are controlled by the computer. And, images are effectively compressed for storage and transmission via the local area network in the department of radiology and to clinical wards.