ASSESSMENT OF IMAGE POSTPROCESSING AND OF MEASURING ASSISTANCE TOOLS IN COMPUTED

Purpose: A system for the examination and measurement of the weight-bearing knee was adapted to computed radiography (CR) and to a picture archiving and communication system (PACS). The examination and measurement system was developed on examination equipment used for QUESTOR precision radiography (QPR). For an easier and more standardised localisation of bony landmarks on the screen, 4 measuring assistance tools (MATs) were developed. The aim of this study was to evaluate the usefulness of the tools developed and of image post-processing, specifically as madcation (zoom) and filtering (edge enhancement), by determining intra-observer variation in the measurement of angles and distances. Material and Methods: The original QPR measurement program, generating 19 angles and distances corrected for parallax and magnification, was converted and installed on a multi-modality workstation (Imtec Image 1200). A CR system (Fuji AC-2) was used for the generation of the related images and the measurements were made on the workstation. Four unilateral examinations of weight-bearing knees were undertaken. These examinations were measured twice under 5 different measurement conditions by 4 viewers. Results and Conclusions: The most important factor in reducing intra-observer variation was the ability to magnify (zoom) the images. The MATs also reduced variation. Filtering (edge enhancement), however, did not affect precision.