Monte Carlo proton dose calculations using a radiotherapy specific dual-energy CT scannerfortissue segmentation and range assessment

Isabel P. Almeida, Lotte E. J. R. Schyns, Ana Vaniqui, Brent van der Heyden, George Dedes, Andreas F. Resch, Florian Kamp, Jaap D. Zindler, Katia Parodi, Guillaume Landry, Frank Verhaegen*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Proton beam ranges derived from dual-energy computed tomography (DECT) images from a dual-spiral radiotherapy (RT)-specific CT scanner were assessed using Monte Carlo (MC) dose calculations. Images from a dual-source and a twin-beam DECT scanner were also used to establish a comparison to the RT-specific scanner. Proton ranges extracted from conventional single-energy CT (SECT) were additionally performed to benchmark against literature values. Using two phantoms, a DECT methodology was tested as input for GEANT4 MC proton dose calculations. Proton ranges were calculated for different mono-energetic proton beams irradiating both phantoms; the results were compared to the ground truth based on the phantom compositions. The same methodology was applied in a head-and-neck cancer patient using both SECT and dual-spiral DECT scans from the RT-specific scanner. A pencil-beam-scanning plan was designed, which was subsequently optimized by MC dose calculations, and differences in proton range for the different image-based simulations were assessed. For phantoms, the DECT method yielded overall better material segmentation with >86% of the voxel correctly assigned for the dual-spiral and dual-source scanners, but only 64% for a twin-beam scanner. For the calibration phantom, the dual-spiral scanner yielded range errors below 1.2 mm (0.6% of range), like the errors yielded by the dual-source scanner (< 1.1 mm, <0.5%). With the validation phantom, the dual-spiral scanner yielded errors below 0.8 mm (0.9%), whereas SECT yielded errors up to 1.6 mm (2%). For the patient case, where the absolute truth was missing, proton range differences between DECT and SECT were on average in -1.2 +/- 1.2 mm (-0.5% +/- 0.5%). MC dose calculations were successfully performed on DECT images, where the dual-spiral scanner resulted in media segmentation and range accuracy as good as the dual-source CT. In the patient, the various methods showed relevant range differences.
Original languageEnglish
Article number115008
Number of pages14
JournalPhysics in Medicine and Biology
Issue number11
Publication statusPublished - 1 Jun 2018


  • proton dose calculations
  • tissue segmentation
  • dual-energy CT
  • proton range

Cite this