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Reducing the sensitivity of IMPT treatment plans to setup errors and range uncertainties via probabilistic treatment planning
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10.1118/1.3021139
/content/aapm/journal/medphys/36/1/10.1118/1.3021139
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/36/1/10.1118/1.3021139

Figures

Image of FIG. 1.
FIG. 1.

Paraspinal case: The thick contours correspond to the CTV, the spinal cord, and the esophagus.

Image of FIG. 2.
FIG. 2.

Sensitivity analysis of a conventional treatment plan: (a) dose distribution that results from a setup error posteriorly, (b) dose distribution realized for a setup error anteriorly, (c) color scale for cumulative dose distributions (left) and dose contributions of individual beams (right) in percent of the prescribed dose.

Image of FIG. 3.
FIG. 3.

Illustration of the effect of misaligned beams. In this schematic example, three pencil beams hit the patient surface at point A. For a setup shift , the three beams hit the patient surface at different points, and hence, yield a different dose distribution.

Image of FIG. 4.
FIG. 4.

Dose contributions of the individual beams for four treatment plans: (a)–(c) conventional IMPT plan, (d)–(f) IMPT plan optimized for range uncertainties alone, (g)–(i) IMPT plan optimized for setup errors alone and (j)–(l) IMPT plan optimized while accounting for both setup and range uncertainty. The color scale in Fig. 2(c) applies.

Image of FIG. 5.
FIG. 5.

Sensitivity analysis of the four treatment plans: (a)–(c) conventional IMPT plan, (d)–(f) IMPT plan optimized for range uncertainties alone, (g)–(i) IMPT plan optimized for setup errors alone, (j)–(l) IMPT plan optimized while accounting for both setup and range uncertainty; the three columns show the nominal dose distribution [(a), (d), (g), (j)], the dose distribution resulting from a systematic overshoot of in water equivalent range [(b), (e), (h), (k)], and a systematic setup error of rightwards [(c), (f), (i), (l)]. The color scale in Fig. 2(c) applies.

Image of FIG. 6.
FIG. 6.

DVH comparison of the four treatment plans for the nominal case, that is no range or setup error occurs. DVHs for the CTV and the spinal cord are shown.

Image of FIG. 7.
FIG. 7.

DVH comparison of the four treatment plans for an overshoot of in water equivalent range. DVHs for the CTV and the spinal cord are shown.

Image of FIG. 8.
FIG. 8.

DVH comparison of the four treatment plans for a setup error of rightwards. DVHs for the CTV and the spinal cord are shown.

Image of FIG. 9.
FIG. 9.

Standard deviation of the dose for three treatment plans discussed in Appendix B: (a) optimized for beamlet correlation model 2, (b) optimized for model 3, (c) conventional plan. The color scale is in percent of prescribed dose.

Image of FIG. 10.
FIG. 10.

SDVH comparison for CTV and spinal cord for the treatment plans discussed in Appendix B. The standard deviation of the dose is calculated using correlation model 2.

Image of FIG. 11.
FIG. 11.

SDVH comparison for CTV and spinal cord for the treatment plans discussed in Appendix B. The standard deviation of the dose is calculated using correlation model 3.

Image of FIG. 12.
FIG. 12.

Illustration of the improved static dose cloud approximation: For a setup error , the entrance point of the pencil beam is shifted by on the patient surface.

Image of FIG. 13.
FIG. 13.

Illustration of dose approximation using virtual beamlets: The dose distribution of the “real” beamlet marked by the central dot is approximated by the virtual beamlet marked by the dot at the lower left.

Image of FIG. 14.
FIG. 14.

Treatment plan optimized for a Gaussian setup error of while approximating dose distributions for setup errors by the improved static dose cloud approximation (Appendix C 1 b): (a)–(c) dose contributions of individual beams, (d) dose distribution for the nominal case, (e) dose distribution for a setup error rightwards predicted by the improved static dose cloud approximation, and (f) dose distribution for a setup error rightwards predicted by the virtual bixel approximation method. The color scale in Fig. 2(c) applies.

Tables

Generic image for table
TABLE I.

Summary of weighting factors, sampling rates, and number of voxels for all volumes of interest.

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/content/aapm/journal/medphys/36/1/10.1118/1.3021139
2008-12-12
2014-04-19
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Reducing the sensitivity of IMPT treatment plans to setup errors and range uncertainties via probabilistic treatment planning
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/36/1/10.1118/1.3021139
10.1118/1.3021139
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