Advantages of using larger-diameter pinhole collimator for prompt X-ray imaging during irradiation with carbon ions

Seiichi Yamamoto*, Takuya Yabe, Takashi Akagi, Mitsutaka Yamaguchi, Naoki Kawachi, Kei Kamada, Akira Yoshikawa, Jun Kataoka

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


Prompt secondary electron bremsstrahlung X-ray (prompt X-ray) imaging using a low-energy X-ray camera is a promising method for observing a beam shape from outside the subject. However, the images measured within short times suffer from statistical noise. Consequently, we performed prompt X-ray imaging with higher sensitivity using a larger-diameter pinhole collimator and compared the results with those of a conventional collimator. Prompt X-ray imaging was conducted during irradiation with pencil beams of 241.5-MeV/n carbon ions to a water phantom. A newly developed X-ray camera with a 4-mm diameter as well as conventional 1.5-mm-diameter pinhole collimators was used for the imaging in list mode, and we compared the prompt X-ray images, energy spectra, and time count rate curves between 1.5-mm-diameter and 4-mm-diameter pinhole collimators. The prompt X-ray images taken with the 4-mm-diameter pinhole collimators had a1/47 times higher sensitivity with 70 % lower offset fractions originating from the prompt gamma photons. Furthermore, the ranges were more precisely estimated with the 4-mm collimator than with the 1.5-mm collimator. The energy spectra showed less contamination by tungsten-characteristic X-rays for the 4-mm pinhole collimator. Even for images measured with 0.1-s intervals, the beam shapes and time count rate curves could be obtained with less statistical noise using the 4-mm-diameter pinhole collimators. The use of the 4-mm-diameter pinhole collimator attached to the X-ray camera had advantages for prompt X-ray imaging with high sensitivity and low background, enabling us to image the beams even with short-Time measurements.

Original languageEnglish
Article numberP09006
JournalJournal of Instrumentation
Issue number9
Publication statusPublished - 2022 Sept 1


  • Gamma camera, SPECT, PET PET/CT, coronary CT angiography (CTA)
  • Gamma detectors (scintillators, CZT, HPGe, HgI etc)
  • Instrumentation for heavy-ion therapy
  • Instrumentation for particle-beam therapy

ASJC Scopus subject areas

  • Instrumentation
  • Mathematical Physics


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