On measuring depth-dose distribution of range-modulated proton therapy fields

Area of Science:

• Medical Physics
• Radiation Oncology
• Particle Therapy

Background:

• Depth-dose profile measurements are crucial for characterizing proton therapy treatment fields.
• Measured profiles often exhibit significant noise, necessitating smoothing that can distort data.
• Understanding the noise origin is key to improving measurement accuracy.

Purpose of the Study:

• To investigate the source of persistent noise in depth-dose profile measurements for proton therapy.
• To determine the impact of sampling duration on measurement error and noise magnitude.
• To identify optimal sampling parameters for noise reduction in proton therapy.

Main Methods:

• Analysis of the scanning algorithm's sampling process in proton therapy beams.
• Comparison of signal time characteristics between proton and photon therapy beams.
• Evaluation of the relationship between sampling duration and noise magnitude.

Main Results:

• Signal time characteristics in proton therapy differ significantly from photon beams.
• Measurement error is highly sensitive to the chosen sampling duration.
• Inappropriate sampling durations are the primary cause of observed noise, not the dose distribution.
• Arbitrarily increasing sampling duration can paradoxically increase noise.

Conclusions:

• Noise in proton therapy depth-dose profiles is primarily an artifact of sampling duration.
• Optimizing and accurately controlling sampling duration can significantly reduce noise.
• Noise reduction is achievable without increasing overall measurement time.