Comparison of vessel contrast measured with a scanning-beam digital x-ray system and an image intensifier/television system.
Vessel contrast was measured in the fluoroscopic images produced by a scanning-beam digital x-ray (SBDX) system and an image intensifier/television (II/TV) based system. The SBDX system electronically scans a series of pencil x-ray beams across the patient, each of which is directed at a distant small-area detector array. The reduction in detected scatter achieved with this geometry was expected to provide an increase in image contrast. Vessel contrast was evaluated from images of a phantom containing iodinated tubes. The vessels were inserted into an acrylic stack to provide a patient-mimicking scattering medium. Vessel diameter ranged from 0.3 to 3.1 mm. Images were acquired at 100 kVp with the SBDX and II/TV systems and averaged to reduce x-ray noise. The II/TV system was operated in the 6-in. image intensifier mode with an anti-scatter grid. The increase in contrast in the SBDX images, expressed as a ratio of the measured SBDX and II/TV contrasts, ranged from 1.63 to 1.79 for individual vessels. This agreed well with a prediction of the contrast improvement ratio for this experiment, based on measurements of the scatter fraction, object-plane line spread functions, and consideration of the source spectrum and detector absorption properties. The predicted contrast improvement ratio for SBDX relative to II/TV images was 1.62 to 1.77.
Speidel
M A
MA
Department of Medical Physics, University of Wisconsin-Madison 53706, USA.
Wilfley
B P
BP
Heanue
J A
JA
Betts
T D
TD
Van Lysel
M S
MS
D000792:Angiography / Q000009:adverse effects / Q000379:methods* / Q000706:statistics & numerical data; D055592:Biophysical Phenomena; D001703:Biophysics; D005471:Fluoroscopy / Q000009:adverse effects / Q000379:methods; D006801:Humans; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000379:methods*; D012542:Scattering, Radiation; D012867:Skin / Q000528:radiation effects; D013690:Television; D014963:X-Ray Intensifying Screens