Design of a Simple Digital Radiography Prototype

Abstract

The aim of this work was to design and implement a simple digital radiography imaging prototype. This prototype is light-tight, pyramid-like structured with dimensions 30x25cm2 in the front and 2x3cm2 output opening, its length is 40cm.The system is simple, cheap, designed locally utilizing intensifying screen to convert X-rays that pass through patients ,body representing patients body image, converting it into visible light image, and the image captured by charge couple device (CCD) camera that is connected to a computer for image contrast enhancement by removing noise. The prototype designed and tested, many radiographs were taken using classical radiographic X-ray machine, installed in Khartoum Teaching Hospital , Khartoum, Sudan in 2002 .The tube used is dual focus, o.6mm fine focus and 1.2mm broad focus, maximum penetrating power is up to 150 KVP and maximum milliamp ere is 500, time start from 0.01second to 5 seconds. Images were taken using tube voltage varies between 60kv and75kv and the Milliampere/second varies between 10mAs and28mAs. The obtained images were processed by using wavelet image processing tools, composed of three steps, first ,second ,third decomposing image into 4 levels with mlti-resolutions, selecting initial estimate for threshold, threshold is frequency higher than white light frequency, because most noise has frequency equal to frequency of white light and then suppressing image parts that has frequency lower than threshold, this part contains noise and finally image was reconstructed to original form. A modified system implemented by inserting lens to concentrate light image and camera put at focal distance, images taken showed more enhanced contrast as proved by using five methods for assessing image quality, the five methods are (1) Histogram equalization (2) Image quality metrics (3) Modulation transfer function (4) Entropy, these four methods used algorithms and the fifth method by ten expert Radiologists viewing.