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A procedure for calculation of monitor units for passively scattered proton radiotherapy beams
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10.1118/1.2992055
/content/aapm/journal/medphys/35/11/10.1118/1.2992055
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/35/11/10.1118/1.2992055

Figures

Image of FIG. 1.
FIG. 1.

Schematic description of the nozzle components of passively scattered proton beamlines at the Proton Therapy Center in Houston.

Image of FIG. 2.
FIG. 2.

Variation of measured SOBPF as a function of SOBP widths (nominal) for: (a) large snout options, (b) medium snout options, and (c) small snout options.

Image of FIG. 3.
FIG. 3.

Examples of the variation of measured SOBPF with range shifter thickness for (option 1) and (option 11) proton beams. Range shifter thickness of corresponds to distal beam range of 25 and for options 1 and 11, respectively.

Image of FIG. 4.
FIG. 4.

Examples of variation of measured RSF as a function of RS thickness for different SOBP widths (nominal) for: (a) proton beam (option 1), (b) proton beam (option 11), and (c) proton beam (option 21).

Tables

Generic image for table
TABLE I.

(a)–(c) ROF for 24 options for passively scattered beams in each of the three beamlines of the Proton Therapy Center in Houston. Each option is identified by the snout size for the maximum allowed field size, associated energy and the deepest range . Output factors are relative to that for beam with a range of (option 9) with an aperture producing a open field at the isocenter. The open field sizes for the medium and small snouts are also . It is for the large snout options. All the measurements are made with an ionization chamber both at the center of the respective SOBP widths and at the isocenter with a SDD of .

Generic image for table
TABLE II.

(a)–(c) SOBPE for 24 options for passively scattered beams in each of the three beamlines of Proton Therapy Center in Houston. Each option is identified by the snout size for the maximum allowed field size, associated energy and the deepest range . In each option, the SOBPF for different SOBP widths are relative to reference width used for measurements of ROF given in Table I. The open field size at the isocenter is same as that used for ROF measurements. All the measurements are made with an ionization chamber both at the center of the respective SOBP widths and at the isocenter with SDD of . The reference SOBP width for BEAM IS with .

Generic image for table
TABLE III.

(a) RSF for a proton beam (option 1) with the deepest range of in water for three different SOBP widths (nominal). (b) RSF for a proton beam (option 11) with the deepest range of in water for three different SOBP widths (nominal). (c) RSF for a proton beam (option 21) with the deepest range of in water for three different SOBP widths (nominal). The RSF for zero range shifter is used as the reference with a value of 1.0.

Generic image for table
TABLE IV.

Field size factors relative to the aperture used in the medium snout for nominal SOBP width of

Generic image for table
TABLE V.

Examples of calculated CPSF, PSF, CSF, and the measured CSF. The VPNC and VPC refer to the verification plan in water phantom without the range compensator and with range compensator. All the doses are computed at point of interest located at the isocenter with a source to point distance of and are in cobalt equivalent cGy.

Generic image for table
TABLE VI.

Comparison of calculated and measured d/MU in a homogeneous water phantom without compensator for a sample of beam parameters used in patient treatment fields. The SOBP widths are nominal.

Generic image for table
TABLE VII.

Results of analysis of difference between the calculated and measured d/MU for patient treatment fields

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/content/aapm/journal/medphys/35/11/10.1118/1.2992055
2008-10-21
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A procedure for calculation of monitor units for passively scattered proton radiotherapy beams
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/35/11/10.1118/1.2992055
10.1118/1.2992055
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