Schemes for the optimization of chest radiography using a computer model of the patient and x-ray imaging system
2001 (English)In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 28, no 10, 2007-2019 p.Article in journal (Refereed) Published
A computer program has been developed to model chest radiography. It incorporates a voxel phantom of an adult and includes antiscatter grid, radiographic screen, and film. Image quality is quantified by calculating the contrast (?OD) and the ideal observer signal-to-noise ratio (SNRI) for a number of relevant anatomical details at various positions in the anatomy. Detector noise and system unsharpness are modeled and their influence on image quality is considered. A measure of useful dynamic range is computed and defined as the fraction of the image that is reproduced at an optical density such that the film gradient exceeds a preset value. The effective dose is used as a measure of the radiation risk for the patient. A novel approach to patient dose and image quality optimization has been developed and implemented. It is based on a reference system acknowledged to yield acceptable image quality in a clinical trial. Two optimizations schemes have been studied, the first including the contrast of vessels as measure of image quality and the second scheme using also the signal-to-noise ratio of calcifications. Both schemes make use of our measure of useful dynamic range as a key quantity. A large variety of imaging conditions was simulated by varying the tube voltage, antiscatter device, screen-film system, and maximum optical density in the computed image. It was found that the optical density is crucial in screen-film chest radiography. Significant dose savings (30%-50%) can be accomplished without sacrificing image quality by using low-atomic-number grids with a low grid ratio or an air gap and more sensitive screen-film system. Dose-efficient configurations proposed by the model agree well with the example of good radiographic technique suggested by the European Commission. ⌐ 2001 American Association of Physicists in Medicine.
Place, publisher, year, edition, pages
2001. Vol. 28, no 10, 2007-2019 p.
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-26764DOI: 10.1118/1.1405840Local ID: 11364OAI: oai:DiVA.org:liu-26764DiVA: diva2:247314