Medical Biophysics 3503G Lecture Notes - Lecture 4: Medical Physics, Photon, Photodiode
5 Aug 2016
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Document Summary
Contrast-detail anaylsis object contrast = (physical property of feature) (physical property of backgound)/physical property of background. Detection limited by resolution idealized scenario: imaging systems a and b both have snr = infinity system b has finer spatial resolution than system a finer spatial resolution higher resolution (better) In graph, everything to the left (of b) is undetected. Realistic contrast-detail curve vertical line for snr = infinity system and diagonal line for perfect resolution system form asymptotes of realistic curve. Digital x-ray detectors consist of arrays of small photon sensory elements (photodiode) Increase element size increases average incident x-ray field decreases snr. Increase in element size measure x-ray field over larger area coarser resolution. Increase in snr causes decrease coarser resolution (b/c over larger area) System d has higher local snr than system a. Vertical line is moved to the left finer resolution. System a has finer spatial resolution than system d.
