This paper applies a published version of signal detection theory to x-ray image intensifier fluoroscopy data and compares the results with more conventional subjective image quality measures. An eight-bit digital framestore was used to acquire temporally contiguous frames of fluoroscopy data from which the modulation transfer function (MTF(u)) and noise power spectrum were established. These parameters were then combined to give detective quantum efficiency (DQE(u)) and used in conjunction with signal detection theory to calculate contrast-detail performance. DQE(u) was found to lie between 0.1 and 0.5 for a range of fluoroscopy systems.
Two separate image quality experiments were then performed in order to assess the correspondence between the objective and subjective methods. First, image quality for a given fluoroscopy system was studied as a function of doserate using objective parameters and a standard subjective contrast-detail method. Following this. the two approaches were used to assess three different fluoroscopy units. Agreement between objective and subjective methods was good; doserate changes were modelled correctly while both methods ranked the three systems consistently.
Marshall NW. The practical application of signal detection theory to image quality assessment in x-ray image intensifier-TV fluoroscopy. Phys Med Biol, 2001; 46: 1631-1649.
Dr. Nick Marshall, NGH Unit, Newcastle upon Tyne. Tel: +44 (0)191-233-6161.
Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, NE7 7DN, UK.
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