Use of BANG® polymer gel for dose measurements in a 68 MeV proton beam

• Published in: Medical physics (Lancaster) 2003-06, Vol.30 (6), p.1235-1240
• Main Authors: Heufelder, J., Stiefel, S., Pfaender, M., Lüdemann, L., Grebe, G., Heese, J.
• Format: Article
• Language: English
• Subjects: Anatomy and optics of eye; biomedical MRI; Cancer; Clinical applications; dosimetry; Dosimetry/exposure assessment; Equipment Failure Analysis; eye; Gas‐filled counters: ionization chambers, proportional, and avalanche counters; Gels; Gels - radiation effects; Gels and sols; Humans; Image scanners; ionisation chambers; Ionization chambers; Linear Energy Transfer; Magnetic resonance; Magnetic resonance imaging; Magnetic Resonance Imaging - instrumentation; Magnetic Resonance Imaging - methods; Models, Theoretical; polymer gel dosimetry; polymer gels; Polymers; Polymers - radiation effects; proton beams; proton detection; proton dosimetry; Proton therapy; Protons; Protons - therapeutic use; Quality assurance equipment; quality control; quality management; radiation therapy; Radiometry - instrumentation; Radiometry - methods; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - methods; Radiotherapy, High-Energy - methods; Reproducibility of Results; Sensitivity and Specificity
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.1575557

BANG polymer gel dosimetry using magnetic resonance imaging (MRI) was applied to an ophthalmologic 68 MeV proton beam. The object was to examine the use of BANG gel for the verification of proton fields in eye tumor therapy and to explore the applicability of polymer gel dosimetry in proton therapy under practical aspects. The gel phantoms were irradiated with monoenergetic and modulated proton beams. MRI analysis was carried out at clinical 1.5 and 3 T MR scanners. At constant LET, results show a linear relationship between spin–spin relaxation rates and dose. However, depth dose curves in BANG gel reveal a quenching of the Bragg maximum due to LET effects. The dose response of the gel for monoenergetic protons and spread-out depth dose distributions can be calculated based on ionization chamber measurements. Experiment and calculations show good agreement and indicate that BANG polymer gels might become a valuable tool in proton therapy quality assurance.