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Influence of x‐ray pulse parameters on the image quality for moving objects in digital cardiac imaging
Author(s) -
Guibelalde Eduardo,
Vano Eliseo,
Vaquero Francisco,
González Luciano
Publication year - 2004
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1790091
Subject(s) - image quality , imaging phantom , motion blur , image intensifier , pulse (music) , signal (programming language) , physics , image resolution , noise (video) , bar (unit) , optics , contrast to noise ratio , contrast (vision) , signal to noise ratio (imaging) , focus (optics) , computer science , computer vision , image (mathematics) , detector , meteorology , programming language
The image quality of a single frame in a modern cardiac imaging x‐ray facility can be improved by adjusting the automatic pulse exposure parameters. The effects of acquisition rate on patient dose and the detectability of moving objects have been fully described in scientific literature. However, the influence of automatic pulse exposure parameters is still to be determined. Images of a moving wheel (with lead wires) were acquired using an H5000 Philips Integris cardiac x‐ray system. Poly(methylmethacrylate) plastic samples 20 and 30 cm thick were employed as the build‐up phantom to simulate a patient. The images were obtained using preset clinical parameters for cardiac imaging procedures. The signal detectability and motion blur of a contrast bar at a transversal speed in the range of 100 – 150 mm / s were evaluated with a cine pulse width of 3, 5, 7, and 10 ms under automatic mA kV regulation. Two levels of exposure at the image intensifier entrance were included in this study. Signal detectability was analyzed in terms of the signal‐to‐noise ratio (SNR) and the value ofSNR 2 /entrance surface dose. The blurring was modeled as a Gaussian‐shaped blurring function, and the motion blur was expressed in terms of the peak full width at half maximum and amplitude (apparent contrast) of the resolution functions. A contrast bar simulating a vessel in motion at the maximum velocities of typical cardiac structures was exposed. Severe loss of image quality occurred at pulse widths ⩾ 7 ms . It is also shown that below 5 ms static nonlinearities, likely caused by the need to use a large focus for cine acquisition, dominate the blurring process.