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Projection imaging of photon beams by the Čerenkov effect
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10.1118/1.4770286
/content/aapm/journal/medphys/40/1/10.1118/1.4770286
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/40/1/10.1118/1.4770286

Figures

Image of FIG. 1.
FIG. 1.

In (a) the Čerenkov angle, ζ, (b) collisional and Čerenkov emission energy losses per unit path length, and (c) CSDA range for an electron traveling through water, tissue, and polystyrene plastic are plotted as a function of particle energy.

Image of FIG. 2.
FIG. 2.

A side view of the system is shown in (a) with the radiation beam vertically entering the tank and inducing Čerenkov light emission, which is captured by a camera placed at an imaging distance L = 45 cm from beam center. The definition of the polar angle of emission θ is shown with respect to the camera field of view. In (b) an aerial view of the system is shown, with the corresponding definition of the azimuthal angle of emission ϕ.

Image of FIG. 3.
FIG. 3.

In (a)–(c), the Monte Carlo derived histograms of Čerenkov emission, P(x, ϕ), for a 4 × 4, 10 × 10, and 20 × 20 cm2 6 MV beam. The histograms of Čerenkov emission, P(θ, z), for all three field sizes are shown in (d)–(f).

Image of FIG. 4.
FIG. 4.

In (a) the Monte Carlo derived phase function, P(z, θ), for Čerenkov emission from a 4 × 4, 10 × 10, and 20 × 20 cm2 6 MV beam at depths of z = d max , 10, 20, 30, and 40 cm. In (b) the normalized phase functions from (a) in comparison to the normalized phase function in the buildup region at z = 0.2 cm for all three field sizes is plotted.

Image of FIG. 5.
FIG. 5.

In (a)–(c) the Monte Carlo derived Čerenkov emission light profiles, P lens , z), as a function of depth for a 4 × 4, 10 × 10, and 20 × 20 cm2 6 MV beam at imaging distances of L = 45, 100, and 150 cm. In (d)–(f) lateral light profiles, P(x, ϕ lens ), for the same three field sizes and imaging distances. The solid lines denote the total light (i.e., angularly integrated emission profiles), expected to be a surrogate for the deposited dose in the medium.

Image of FIG. 6.
FIG. 6.

In (a)–(c) the horizontal calibration factor, C(x), is plotted for a 4 × 4, 10 × 10, and 20 × 20 cm2 6 MV beam at imaging distances of L = 45, 100, and 150 cm. In (b) the vertical calibration factor, C(z), for all three field sizes at each imaging distance is plotted.

Image of FIG. 7.
FIG. 7.

In (a)–(j) the full resolution captured images of a 10 × 10 cm2 FOV for a 4 × 4 cm2 6 MV beam after temporal median filtering of a various number of frames denoted by the numbers in the bottom right of each image. The scale bar in the bottom left of each image corresponds to 1 cm.

Image of FIG. 8.
FIG. 8.

The signal to noise ratio as a function of delivered dose is plotted for a 4 × 4 cm2 6 MV beam. The corresponding coefficient values after regression to a square root power law are shown.

Image of FIG. 9.
FIG. 9.

In (a) the PDD from the TPS and Čerenkov emission light profile before and after correction are plotted. The corresponding dose difference as a function of depth between the TPS and corrected signal is shown in (b). In (c) the lateral profile comparison between the TPS and corrected and uncorrected light profiles at a depth of d max is shown. The corresponding dose difference is shown in (d).

Tables

Generic image for table
TABLE I.

Relevant optical parameters of Čerenkov emission in water, tissue, and polystyrene plastic.

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/content/aapm/journal/medphys/40/1/10.1118/1.4770286
2012-12-19
2014-04-25
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Projection imaging of photon beams by the Čerenkov effect
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/40/1/10.1118/1.4770286
10.1118/1.4770286
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