title: Evaluation of an application for intensity-based deformable image registration and dose accumulation in radiotherapy.
abstract: BACKGROUND
  Methods to accurately accumulate doses in radiotherapy (RT) are important for tumour and normal tissues being influenced by geometric uncertainties. The purpose of this study was to investigate a pre-release deformable image registration (DIR)-based dose accumulation application, in the setting of prostate RT.
  
  
  METHODS
  Initially accumulated bladder and prostate doses were assessed (based on 8-9 repeat CT scans/patient) for nine prostate cancer patients using an intensity-based DIR and dose accumulation algorithm as provided by the Dynamic Adaptive Radiation Therapy (DART) software. The accumulated bladder and prostate dose-volume histograms (DVHs) were compared on a range of parameters (paired Wilcoxon signed-rank test, 5% significance level) to DVHs derived using an in-house developed dose accumulation method based on biomechanical, contour-driven DIR (SurfaceRegistration). Finally, both these accumulated dose distributions were compared to the 'static' DVH, assessed from the planning CT.
  
  
  RESULTS
  Over the population, doses accumulated with DART were overall lower than those from SurfaceRegistration (p < 0.05: D2%, gEUD and NTCP (bladder); Dmin (prostate)). The magnitude of these differences peaked for the bladder gEUD with a population median of 47 Gy for DART versus 57 Gy for SurfaceRegistration. Across the ten bladder dose/volume parameters investigated, the most pronounced individual differences were observed between the 'accumulated' DVHs and the 'static' DVHs, with deviations in mean dose up to 22 Gy.
  
  
  CONCLUSIONS
  Substantial and significant differences were observed in the dose distributions between the two investigated DIR-based dose accumulation applications. The most pronounced individual differences were seen for the bladder and relative to the planned dose distribution, encouraging the use of repeat imaging data in RT planning and evaluation for this organ.
authors: Department of Medical Physics, Memorial Sloan Kettering Cancer Centre , New York City, New York , USA.
authors: Maria
authors: M
authors: Thor
authors: Else S
authors: ES
authors: Andersen
authors: Jørgen B B
authors: JB
authors: Petersen
authors: Thomas S
authors: TS
authors: Sørensen
authors: Karsten Ø
authors: KØ
authors: Noe
authors: Kari
authors: K
authors: Tanderup
authors: Lise
authors: L
authors: Bentzen
authors: Ulrik V
authors: UV
authors: Elstrøm
authors: Morten
authors: M
authors: Høyer
authors: Ludvig P
authors: LP
authors: Muren
mesh_terms: D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008297:Male; D058958:Organs at Risk / Q000528:radiation effects; D011467:Prostate / Q000000981:diagnostic imaging / Q000528:radiation effects*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods; D001743:Urinary Bladder / Q000000981:diagnostic imaging / Q000528:radiation effects*