MIRA2015 Lecture Notes - Lecture 1: Digital Image Processing, Unsharp Masking, Image Histogram

• School: Curtin University
• Department: Medical Imaging, Radiology & Radiography
• Course: MIRA2015
• Professor: Cat Kealley

Document Summary

Range of image densities: variation in x-ray absorption and transmission as x-ray beam passes through tissues. Pre-processing: depends on modality, initial steps applied to raw imaging data. Processing: manipulation of raw data just after acquisition. Usually proprietary and specific to dr vendor. Profound effect on image final appearance can also lead to artefacts unique to digital system. Does not involve alteration of raw data. Pre-processing in 2d detector arrays and ccd linear arrays. Methods account for defects, imperfections, and non-uniformity in the detection system. Initial steps applied to raw imaging data, generally no input from device operator and are usually built into each manufacturer"s system. Dead (non-functional) pixels: value is interpolated by averaging surrounding pixel values. Dark noise: electronic noise associated with each detector element in absence of radiation. To minimise, multiple are acquired, averaged, and subtracted from the actual image. Inherent variability between individual detector elements: banding pattern in different detector regions.