Dose distributions of a proton beam for eye tumor therapy: Hybrid pencil-beam ray-tracing calculations
Density distribution across the slice phantom (see text) obtained by x-ray CT (solid line) and areometric measurements (dashed line).
(a) Transversal x-ray CT cut of a (nonspherical) eye with contours (lines) of the OCTOPUS eye model matched to CT structures. Note artifacts (light-black jets) emanating from the clip (position marked by cross wires) Superimposed are the isodose lines of the distribution calculated on the CT density distribution. Beam and/or eye axis inclination is 30°. (b) Same situation as in (a), quasi-CT density matrix constructed from the CT-matched OCTOPUS eye model (cross wires now in tumor iso-center). (c) Same as (a), but dose distribution calculated on the quasi-CT matrix of (b).
For the situation of Fig. 2, transversal CT cut, eye model (lines) and isodoses calculated on the quasi-CT density as in Fig. 2(c), but the model conjunctiva plane artificially withdrawn from the eye (see text). Lower part, zoom of the distal-edge region.
Dose distributions of a fully modulated standard proton beam, range (in water), diam, in the sugar solution slice phantom. Left, perpendicular incidence. Right, incidence under . Two-dimensional cuts, calculated isodose lines are superimposed to the CT density distributions (grey tones). One-dimensional transverse distributions: Dashed lines measured with a diode along the straight lines in the fourth slice. Solid lines, proton algorithm results.
Dependence of the 90%–10% falloff distance on traversed depth in water for a “sharp” proton beam (see text) with a SOBP of range and length. Points: measured values. Dashed curve, 2.56 times RMS lateral extension of pencil beam of entrance energy (range ). Solid curve, values obtained by quadratic addition of to entrance penumbra. Horizontal dashed straight line, EYEPLAN value.
(a) Transverse profile of a collimated diam therapy beam measured behind a 45° wedge perpendicularly to the edge through the collimator center. Shadowy areas indicate the 90%–10% dose falloff. Dashed curve, EYEPLAN prediction. (b) Radial 90%–10% dose falloff width as function of wedge material thickness at the collimator border (represented by its square root). Point symbols, measurements. Dashed line, interpolation of measured points. Solid line, result of calculation (see text). EYEPLAN value for HMI standard setup, .
(a) Calculated proton fluence distribution in the eye entrance plane with a 60° wedge covering 80% of the horizontal patient collimator extension. (b) Dose distribution on the central cut through the beam with the collimator-wedge situation of (a), on the phantom of Fig. 4, with penumbra widening taken into account.
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