Scatter-glare estimation for digital radiographic systems: comparison of digital filtration and sampling techniques.
The scatter and veiling glare distribution in images acquired with a digital subtraction angiography imaging system was estimated using a digital filtration and a beam-stop technique. The digital filtration technique utilizes exposure parameters and image gray levels to estimate scatter-glare intensity based on previous phantom measurements. The beam-stop technique uses an array of lead discs in order to sample scatter-glare intensity for each patient. To test the ability of digital filtration and beam-stop techniques to estimate the scatter-glare intensity, they were applied to images of postmortem swine animal models at different projections and beam energies. The systematic and root-mean-square (rms) percentage errors of these estimates were obtained by comparison to directly measured scatter-glare images using a scanning lead strip technique. The average rms percentage error for the digital filtration and beam-stop techniques were 8.07% and 6.67%, respectively. The changes in scatter-glare intensity due to contrast injection during coronary arteriography and ventriculography were also measured using the beam-stop technique. The maximum changes in scatter-glare intensities during coronary arteriography and ventriculography were 19 and 88%, respectively. The results indicate that the digital filtration technique is more suited for applications such as coronary arteriography and ventriculography where the iodinated contrast material significantly changes the scatter-glare intensity.
Molloi
S
S
Department of Radiological Sciences, Medical Sciences I, University of California, Irvine 92697, USA. SYMOLLOI@UCI.EDU
Zhou
Y
Y
Wamsely
G
G
D015901:Angiography, Digital Subtraction / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D000818:Animals; D017023:Coronary Angiography / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D005374:Filtration / Q000295:instrumentation / Q000379:methods; D019466:Glare; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D008433:Mathematics; D015203:Reproducibility of Results; D012494:Sampling Studies; D012542:Scattering, Radiation; D013552:Swine; D013997:Time Factors