Faculty Collaboration Database

Feasibility of using PRESAGE® for relative 3D dosimetry of small proton fields. Phys Med Biol 2012 Nov 21;57(22):N431-43

Date

10/30/2012

Pubmed ID

23103526

Pubmed Central ID

PMC3844616

DOI

10.1088/0031-9155/57/22/N431

Scopus ID

2-s2.0-84869034689 (requires institutional sign-in at Scopus site)   25 Citations

Abstract

Small field dosimetry is challenging due to the finite size of the conventional detectors that underestimate the dose distribution. With the fast development of the dynamic proton beam delivery system, it is essential to find a dosimeter which can be used for 3D dosimetry of small proton fields. We investigated the feasibility of using a proton formula PRESAGE® for 3D dosimetry of small fields in a uniform scanning proton beam delivery system with dose layer stacking technology. The relationship between optical density and the absorbed dose was found to be linear through small volume cuvette studies for both photon and proton irradiation. Two circular fields and three patient-specific fields were used for proton treatment planning calculation and beam delivery. The measured results were compared with the calculated results in the form of lateral dose profiles, depth dose, isodose plots and gamma index analysis. For the circular field study, lateral dose profile comparison showed that the relative PRESAGE® profile falls within ± 5% from the calculated profile for most of the spatial range. For unmodulated depth dose comparison, the agreement between the measured and calculated results was within 3% in the beam entrance region before the Bragg peak. However, at the Bragg peak, there was about 20% underestimation of the absorbed dose from PRESAGE®. For patient-specific field 3D dosimetry, most of the data points within the target volume passed gamma analysis for 3% relative dose difference and 3 mm distance to agreement criteria. Our results suggest that this proton formula PRESAGE® dosimeter has the potential for 3D dosimetry of small fields in proton therapy, but further investigation is needed to improve the dose under-response of the PRESAGE® in the Bragg peak region.

Author List

Zhao L, Newton J, Oldham M, Das IJ, Cheng CW, Adamovics J

Author

Li Zhao PhD Associate Professor in the Radiation Oncology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Feasibility Studies
Humans
Proton Therapy
Protons
Radiometry
Radiotherapy Planning, Computer-Assisted
Scattering, Radiation