title: Patient-specific online dose verification based on transmission detector measurements.
abstract: Since IMRT-techniques lead to an increasingly complicated environment, a patient specific IMRT-plan verification is recommended. Furthermore, verifications during patient irradiation and 3D dose reconstruction have the potential to improve treatment delivery, accuracy and safety. This study provides a detailed investigation of the new transmission detector (DTD) Dolphin (IBA Dosimetry, Germany) for online dosimetry.
  
  
  
  The clinical performance of the DTD was tested by dosimetric plan verification in 2D and 3D for 18 IMRT-sequences. In 2D, DTD measurements were compared to a pre-treatment verification method and a treatment planning system by gamma index and dose difference evaluations. In 3D, dose-volume-histogram (DVH) indices and gamma analysis were evaluated. Furthermore, the error detection ability was tested with leaf position uncertainties and deviations in the linear accelerator (LINAC) output.
  
  
  
  The DTD measurements were in excellent agreement to reference measurements in both 2D (γ3%,3mm=(99.7±0.6)% <1, ΔD±5%=(99.5±0.5)%) and 3D. Only a small dose underestimation (<2%) within the target volume was observed when analyzing DVH-indices. Positional errors of the leaf banks larger than 1mm and errors in LINAC output larger than 2% were identified with the DTD.
  
  
  
  The DTD measures the delivered dose with sufficient accuracy and is therefore suitable for clinical routine.
authors.affiliation: Department of Radiation Oncology, University Medical Center Mannheim, Medical Faculty Mannheim, University of Heidelberg, Germany. Electronic address: johannes.thoelking@medma.uni-heidelberg.de.
authors.forename: Johannes
authors.initials: J
authors.lastname: Thoelking
authors.affiliation: Department of Radiation Oncology, University Medical Center Mannheim, Medical Faculty Mannheim, University of Heidelberg, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Fleckenstein
authors.affiliation: Department of Radiation Oncology, University Medical Center Mannheim, Medical Faculty Mannheim, University of Heidelberg, Germany.
authors.forename: Yuvaraj
authors.initials: Y
authors.lastname: Sekar
authors.affiliation: St George's Cancer Care Center, Christchurch, New Zealand.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Boggula
authors.affiliation: Department of Radiation Oncology, University Medical Center Mannheim, Medical Faculty Mannheim, University of Heidelberg, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Lohr
authors.affiliation: Department of Radiation Oncology, University Medical Center Mannheim, Medical Faculty Mannheim, University of Heidelberg, Germany.
authors.forename: Frederik
authors.initials: F
authors.lastname: Wenz
authors.affiliation: Department of Radiation Oncology, University Medical Center Mannheim, Medical Faculty Mannheim, University of Heidelberg, Germany.
authors.forename: Hansjoerg
authors.initials: H
authors.lastname: Wertz
mesh_terms: D005720:Gamma Rays; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy*; D010315:Particle Accelerators; D011785:Quality Assurance, Health Care; D011874:Radiometry / Q000295:instrumentation*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods
keywords: Online dose verification; Quality assurance; Transmission detector