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MLC quality assurance using EPID: A fitting technique with subpixel precision
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View: Figures


Image of FIG. 1.
FIG. 1.

(a) A strip test image acquired using an EPID. The dashed lines illustrate the effect of rotational correction (the rotational correction is exaggerated to highlight the influence of the rotational adjustment), black dashed vertical line indicates the position of the abutment; solid white horizontal lines indicate the position of interleaf leakage stripes.

Image of FIG. 2.
FIG. 2.

Typical intensity profile of a strip test image in the direction parallel to the leaf motion.

Image of FIG. 3.
FIG. 3.

Image rotation angle for 36 EPID images from the test series.

Image of FIG. 4.
FIG. 4.

Measured abutment peak and corresponding Lorentzian and Gaussian function fits.

Image of FIG. 5.
FIG. 5.

Measured abutment peak: (a) Peak height dependence on the nominal gap width. The labeled data points and corresponding solid lines represent the image pixel data and fits, respectively, for , , , , , and nominal gap widths, (b) Variation of peak position for a set of asymmetrically varying leaf positions.

Image of FIG. 6.
FIG. 6.

(a). RPH vs nominal gap width for the six abutment regions in the seven-field strip test. Both symmetric and asymmetric gaps are displayed as solid and dashed lines, respectively, for a series of measurements with varying gap widths. The standard deviations correspond to the variation in the RPH measurements for the 40 MLC leaf pairs, (b) Superimposed curves from Fig. 6(a), showing the spread of the NPH curves for the six abutment regions. Solid lines: Symmetric gap. Dashed lines: Asymmetric gap.

Image of FIG. 7.
FIG. 7.

Measured vs preset gap width for gap widths ranging from 0.4 to .

Image of FIG. 8.
FIG. 8.

vs asymmetric gap (upper) and symmetric gap for six abutments.

Image of FIG. 9.
FIG. 9.

Scatter plot of measured vs preset leaf position. Each cloud consists of 240 data points (40 leaf pairs six abutments).

Image of FIG. 10.
FIG. 10.

Frequency histogram of data presented in Fig. 9.


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Scitation: MLC quality assurance using EPID: A fitting technique with subpixel precision