Geometric artifacts in line-pair modulations due to beam divergence. Note that these effects have been greatly exaggerated here for the sake of display. In reality, they are visually undetectable with typical imaging geometries.
Variation of the normalization value relative to the normalization condition for the phosphor screen only, and for and video EPIDs.
The typical arrangement of the three bars for MTF measurement. The center of the right edge of the uncut bar is aligned with the center of the field, while the two bars containing line pairs are symmetrically placed about the line passing through this edge (alignment requirements are only approximate). The above image was cropped for display purposes.
The LSF for the Elekta iViewGT system obtained from slit response measurements.
The LSF for the Elekta iViewGT system obtained from edge response measurements.
Bar-pattern images along with their modulation profiles are shown for the Elekta iViewGT system.
Correction of the bar-pattern normalization profile for baseline artifacts. The baseline profile was determined by imaging the bar patterns without the normalization bar. The above profiles were measured for the Elekta iViewGT system.
The MTF measured for the Siemens BEAMVTEW video EPID, Elekta iViewGT EPID, and the brass plate-Kodak X-OmatV film combination using the slit, edge, and bar-pattern methods. Also shown is the MTF for a Lanex Fast-B screen from LSF and bar response profiles generated using Monte Carlo simulations. Error bars indicate one standard error.
Comparison of MTFs obtained for the BEAMVIEW, iViewGT, and film systems with those reported for similar prototype systems. The italicized entries indicate our measurements. (A) Comparison with prototype EPIDs. (B) Comparison with prototype lens-coupled EPIDs. (C) Comparison with film.
Summary of statistical comparisons of MTF measurements. Boldface -values indicate significant difference. (A) Siemens BEAMVIEW. (B) Elekta iViewGT. (C) Brass build-up plate-Kodak X-Omat V film.
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