Detectability of Anatomical Changes With Prompt-Gamma Imaging: First Systematic Evaluation of Clinical Application During Prostate-Cancer Proton Therapy

Research output: Contribution to journalResearch articleContributedpeer-review



PURPOSE: The development of online-adaptive proton therapy (PT) is essential to overcome limitations encountered by day-to-day variations of the patient's anatomy. Range verification could play an essential role in an online feedback loop for the detection of treatment deviations such as anatomical changes. Here, we present the results of the first systematic patient study regarding the detectability of anatomical changes by a prompt-gamma imaging (PGI) slit-camera system.

METHODS AND MATERIALS: For 15 patients with prostate cancer, PGI measurements were performed during 105 fractions (201 fields) with in-room control computed tomography (CT)acquisitions. Field-wise doses on control CT scans were manually classified as whether showing relevant or non-relevant anatomical changes. This manual classification of the treatment fields was then used to establish an automatic field-wise ground truth based on spot-wise dosimetric range shifts, which were retrieved from integrated depth-dose (IDD) profiles. To determine the detection capability of anatomical changes with PGI, spot-wise PGI-based range shifts were initially compared with corresponding dosimetric IDD range shifts. As final endpoint, the agreement of a developed field-wise PGI classification model with the field-wise ground truth was determined. Therefore, the PGI model was optimized and tested for a subcohort of 131 and 70 treatment fields, respectively.

RESULTS: The correlation between PGI and IDD range shifts was high, ρ pearson = 0.67 (p < 0.01). Field-wise binary PGI classification resulted in an area under the curve of 0.72 and 0.80 for training and test cohorts, respectively. The model detected relevant anatomical changes in the independent test cohort, with a sensitivity and specificity of 74% and 79%, respectively.

CONCLUSIONS: For the first time, evidence of the detection capability of anatomical changes in prostate-cancer PT from clinically acquired PGI data is shown. This emphasizes the benefit of PGI-based range verification and demonstrates its potential for online-adaptive PT.


Original languageEnglish
Pages (from-to)718-729
Number of pages12
JournalInternational journal of radiation oncology, biology, physics
Issue number3
Early online dateSept 2023
Publication statusPublished - 1 Nov 2023

External IDs

Scopus 85160514491
ORCID /0000-0002-7017-3738/work/146646043
WOS 001084379500001
ORCID /0000-0002-7922-3041/work/147143041
PubMed 37160193
ORCID /0000-0003-4261-4214/work/147143114


Research priority areas of TU Dresden

Subject groups, research areas, subject areas according to Destatis

Sustainable Development Goals


  • Male, Humans, Proton Therapy/methods, Prostate/diagnostic imaging, Tomography, X-Ray Computed/methods, Radiometry, Prostatic Neoplasms/diagnostic imaging, Radiotherapy Planning, Computer-Assisted/methods, Slit-camera, Range verification, Sensitivity, Interfractional variations, Pencil beams