Prog Med Phys.  2015 Mar;26(1):42-51. 10.14316/pmp.2015.26.1.42.

Development of Two-dimensional Prompt-gamma Measurement System for Verification of Proton Dose Distribution

• Park JH
• Lee HR
• Kim CH
• Kim SH
• Kim S
• Lee SB

• KMID: 2315777
• DOI: http://doi.org/10.14316/pmp.2015.26.1.42

Abstract

In proton therapy, verification of proton dose distribution is important to treat cancer precisely and to enhance patients\' safety. To verify proton dose distribution, in a previous study, our team incorporated a vertically-aligned one-dimensional array detection system. We measured 2D prompt-gamma distribution moving the developed detection system in the longitudinal direction and verified similarity between 2D prompt-gamma distribution and 2D proton dose distribution. In the present, we have developed two-dimension prompt-gamma measurement system consisted of a 2D parallel-hole collimator, 2D array-type NaI(Tl) scintillators, and multi-anode PMT (MA-PMT) to measure 2D prompt-gamma distribution in real time. The developed measurement system was tested with 22Na (0.511 and 1.275 MeV) and 137Cs (0.662 MeV) gamma sources, and the energy resolutions of 0.511, 0.662 and 1.275 MeV were 10.9%+/-0.23p%, 9.8%+/-0.18p% and 6.4%+/-0.24p%, respectively. Further, the energy resolution of the high gamma energy (3.416 MeV) of double escape peak from Am-Be source was 11.4%+/-3.6p%. To estimate the performance of the developed measurement system, we measured 2D prompt-gamma distribution generated by PMMA phantom irradiated with 45 MeV proton beam of 0.5 nA. As a result of comparing a EBT film result, 2D prompt-gamma distribution measured for 9x10(9) protons is similar to 2D proton dose distribution. In addition, the 45 MeV estimated beam range by profile distribution of 2D prompt gamma distribution was 17.0+/-0.4 mm and was intimately related with the proton beam range of 17.4 mm.

Keyword

Proton therapy; 2D proton dose distribution; Two-dimension prompt-gamma measurement system

MeSH Terms

Polymethyl Methacrylate
Proton Therapy
Protons*
United Nations
Polymethyl Methacrylate
Protons

Figure

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  Fig. 1. Development of two-dimension prompt-gamma measurement system consisted of multichannel signal processing device, 2D array-type NaI(Tl) scintillators, 2D photo sensors, pallel-holes collimator and data acquisition system.

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  Fig. 2. Experiment setting in 45 MeV proton beam utility facilities.

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  Fig. 3. Energy spectra and position of 22Na gamma source measured by two-dimension prompt-gamma measurement system.

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  Fig. 4. Energy spectra and position of 137Cs gamma source measured by two-dimension prompt-gamma measurement system.

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  Fig. 5. Energy spectra of Am-Be source measured by two-dimension prompt-gamma measurement system.

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  Fig. 6. Efficiency map of two-dimension prompt-gamma measurement system with 137Cs gamma source.

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  Fig. 7. Proton dose distribution with EBT film (left) and image registration between EBT film result and prompt gamma 2D distribution (right).

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  Fig. 8. Two-dimension images of prompt gamma rays measured by two-dimension prompt-gamma measurement system with 45 MeV proton beam of 0.5 nA.

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  Fig. 9. Prompt-gamma profile distribution with 45 MeV proton beam measured for 9×109 protons and sigmoidal curve fitting.

Reference

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