Dosimetric impact of tantalum markers used in the treatment of uveal melanoma with proton beam therapy

Wayne D. Newhauser, Nicholas C. Koch, Jonas D. Fontenot, Stanley J. Rosenthal, Dan S. Gombos, Markus M. Fitzek, Radhe Mohan

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


Metallic fiducial markers are frequently implanted in patients prior to external-beam radiation therapy to facilitate tumor localization. There is little information in the literature, however, about the perturbations in proton absorbed-dose distribution these objects cause. The aim of this study was to assess the dosimetric impact of perturbations caused by 2.5 mm diameter by 0.2 mm thick tantalum fiducial markers when used in proton therapy for treating uveal melanoma. Absorbed dose perturbations were measured using radiochromic film and confirmed by Monte Carlo simulations of the experiment. Additional Monte Carlo simulations were performed to study the effects of range modulation and fiducial placement location on the magnitude of the dose shadow for a representative uveal melanoma treatment. The simulations revealed that the fiducials caused perturbations in the absorbed-dose distribution, including absorbed-dose shadows of 22% to 82% in a typical proton beam for treating uveal melanoma, depending on the marker depth and orientation. The clinical implication of this study is that implanted fiducials may, in certain circumstances, cause dose shadows that could lower the tumor dose and theoretically compromise local tumor control. To avoid this situation, fiducials should be positioned laterally or distally with respect to the target volume.

Original languageEnglish (US)
Article number021
Pages (from-to)3979-3990
Number of pages12
JournalPhysics in Medicine and Biology
Issue number13
StatePublished - Jul 7 2007

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging


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