title: In vivo alanine/EPR dosimetry in daily clinical practice: a feasibility study.
abstract: OBJECTIVE
  The objective of this study was evaluation of accuracy of in vivo dosimetry using electron paramagnetic resonance (EPR) in alanine. Additionally, we aimed to identify sources of uncertainty in dose determination and quantitative assessment of physical factors that may result in discrepancies between the measured and planned single-fraction doses.
  
  
  METHODS
  The measurements were performed using detectors in a form of 1.6 cm x 1.6 cm polyethylene sachets filled with powdered L-alanine. The detectors were taped to the patient's skin and measured the entrance doses for (60)Co and electron beams. Some detectors were covered with buildup material, and some measured the "skin dose." The EPR measurements were performed with a Varian E-4 spectrometer.
  
  
  RESULTS
  The calculated uncertainty of EPR measured doses was dependent on measured doses and varied from 6.6% for 0.5 Gy to 3.2% for 2 Gy. The calculated uncertainty was in concordance with experimentally determined reproducibility of EPR signals. However, the deviations between measured and planned doses exceeded the uncertainty range of EPR measurements, which can be attributed to uncertainty in determination of actually delivered doses to the detectors, on the basis of treatment planning data.
  
  
  CONCLUSIONS
  The accuracy of dose determination by EPR measurements was shown to be achievable within the 5% limit recommended by the ICRU for doses above 0.7 Gy. The accuracy of in vivo verification of radiotherapy doses by in vivo EPR dosimetry can be improved by meticulous selection of measurement conditions, i.e., radiation fields and detector positions, ensuring accurate calculation of doses delivered to the dosimeters.
authors.affiliation: Department of Physics, Medical University of Gdansk, Gdansk, Poland. bciesiel@amg.gda.pl
authors.forename: Bartlomiej
authors.initials: B
authors.lastname: Ciesielski
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Schultka
authors.forename: Anna
authors.initials: A
authors.lastname: Kobierska
authors.forename: Renata
authors.initials: R
authors.lastname: Nowak
authors.forename: Zofia
authors.initials: Z
authors.lastname: Peimel-Stuglik
mesh_terms: D000409:Alanine; D000465:Algorithms; D003037:Cobalt Radioisotopes / Q000627:therapeutic use; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005240:Feasibility Studies; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy*; D011874:Radiometry; D011879:Radiotherapy Dosage
chemical_list: D003037:Cobalt Radioisotopes; D000409:Alanine