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A nonlinear lag correction algorithm for a-Si flat-panel x-ray detectors
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10.1118/1.4752087
/content/aapm/journal/medphys/39/10/10.1118/1.4752087
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/39/10/10.1118/1.4752087

Figures

Image of FIG. 1.
FIG. 1.

(a) Flow chart for the LTI deconvolution algorithm and (b) flow chart for the NLCSC algorithm. An important modification made for the NLCSC algorithm is changing the state variable to the estimated stored charge.

Image of FIG. 2.
FIG. 2.

Flowchart of the NLCSC calibration algorithm.

Image of FIG. 3.
FIG. 3.

Stored charge estimates Q n for (a) the longest time constant and (b) the second longest time constant charge traps. Data points were fit with a fourth-order polynomial.

Image of FIG. 4.
FIG. 4.

Exposure-dependent lag rates for (a) the longest time constant and (b) the second longest time constant charge traps. Data points were fit with an exponential function. The form of the function ensures that a 2,n (0) = 0.

Image of FIG. 5.
FIG. 5.

The uncorrected and corrected RSRF found during the global search for the optimal a 2,n (x) at x = 27%.

Image of FIG. 6.
FIG. 6.

Uncorrected and corrected FSRFs for step-response data at several different exposures, (a) LTI corrections derived from a 27% step-response, (b) NLCSC correction which takes into account the exposure dependence, and (c) the intensity weighted only non-LTI correction.

Image of FIG. 7.
FIG. 7.

1 × 1 × 5 mm3 reconstructions of a pelvic phantom (42 × 26 cm2) with (a) no lag correction, (b) best LTI correction, (c) worst LTI correction, (d) intensity weighted lag correction, and (e) NLCSC correction. Window, level = 200, −25 HU.

Image of FIG. 8.
FIG. 8.

0.5 × 0.5 × 5 mm3 reconstructions of a pelvic phantom (20 × 16 cm2) with (a) no lag correction, (b) best LTI correction, (c) worst LTI correction, and (d) NLCSC correction. Window, level = 100, −25 HU.

Tables

Generic image for table
TABLE I.

Percent of a-Si FP saturation signal for different exposure intensities at 125 kVp with 0.5 mm Ti.

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TABLE II.

LTI IRF parameters from calibration FSRF data at an exposure level of 27%. The base lag rates a 1, n have units of frames −1 and the lag coefficients b n have units of (detector counts with lag/detector counts without lag).

Generic image for table
TABLE III.

Summary of 1st and 50th frame residual lag for uncorrected, LTI, and NLCSC algorithms.

Generic image for table
TABLE IV.

Summary of ROI reconstruction errors for different lag correction algorithms.

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/content/aapm/journal/medphys/39/10/10.1118/1.4752087
2012-09-18
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A nonlinear lag correction algorithm for a-Si flat-panel x-ray detectors
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/39/10/10.1118/1.4752087
10.1118/1.4752087
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