Quantifying lateral penumbra advantages of collimated spot-scanning beam for intensity-modulated proton therapy

  • Chun-Bo Liu
  • Yun-Tao Song
  • Hong-Dong Liu
  • Hai-Zhou Xue
  • Han-Sheng FengEmail author


Intensity-modulated proton therapy (IMPT) is becoming essential for proton therapy and is under rapid development. However, for IMPT, the lateral penumbra of the spot-scanning proton beam is still an urgent issue to be solved. Patient-specific block collimators (PSBCs), which can block unnecessary doses, play a crucial role in passive scattering delivery technology but are rarely used in spot scanning. One objective of this study is to investigate the lateral penumbra variations of intensity-modulated spot scanning with and without a PSBC. For fields with varying degrees of sharpness and at varying depths in a water phantom, the lateral penumbral widths were calculated using a Monte Carlo-based dose engine from RayStation 6. The results suggest that the lateral penumbral widths can be reduced by more than 30% for uniform target volumes, regardless of whether a range-shifter is used, and that the maximum dose beyond the field edges can be reduced significantly. The results of patient cases show that the doses in organs-at-risk near the edge of the target volume decrease if a PSBC is implemented. This study demonstrates that intensity-modulated spot scanning with a PSBC can effectively reduce the lateral penumbra and block unnecessary doses and is therefore promising for clinical applications in spot-scanning proton therapy.


Lateral penumbra Patient-specific block collimator Monte Carlo Intensity-modulated proton therapy 


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Copyright information

© China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Chinese Nuclear Society and Springer Nature Singapore Pte Ltd. 2019

Authors and Affiliations

  • Chun-Bo Liu
    • 1
  • Yun-Tao Song
    • 1
    • 2
  • Hong-Dong Liu
    • 1
  • Hai-Zhou Xue
    • 3
  • Han-Sheng Feng
    • 2
    Email author
  1. 1.University of Science and Technology of ChinaHefeiChina
  2. 2.Institute of Plasma Physics, Hefei Institutes of Physical ScienceChinese Academy of SciencesHefeiChina
  3. 3.Hefei CAS Ion Medical and Technical Devices Co., LtdHefeiChina

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