title: The role of perfusion effects in monitoring of chemoradiotherapy of rectal carcinoma using diffusion-weighted imaging.
abstract: OBJECTIVE
  The aim of this study was to characterize and understand the therapy-induced changes in diffusion parameters in rectal carcinoma under chemoradiotherapy (CRT). The current literature shows conflicting results in this regard. We applied the intravoxel incoherent motion model, which allows for the differentiation between diffusion (D) and perfusion (f) effects, to further elucidate potential underlying causes for these divergent reports.
  
  
  METHODS
  Eighteen patients with primary rectal carcinoma undergoing preoperative CRT were examined before, during, and after neoadjuvant CRT using diffusion-weighted imaging. Using the intravoxel incoherent motion approach, f and D were extracted and compared with postoperative tumor downstaging and volume.
  
  
  RESULTS
  Initial diffusion-derived parameters were within a narrow range (D1 = 0.94 ± 0.12 × 10(-3) mm(2)/s). At follow-up, D rose significantly (D2 = 1.18 ± 0.13 × 10(-3) mm(2)/s; P < 0.0001) and continued to increase significantly after CRT (D3 = 1.24 ± 0.14 × 10(-3) mm(2)/s; P < 0.0001). The perfusion fraction f did not change significantly (f1 = 9.4 ± 2.0%, f2 = 9.4 ± 1.7%, f3 = 9.5 ± 2.7%). Mean volume (V) decreased significantly (V1 = 16,992 ± 13,083 mm(3); V2 = 12,793 ± 8317 mm(3), V3 = 9718 ± 6154 mm(3)). T-downstaging (10:18 patients) showed no significant correlation with diffusion-derived parameters.
  
  
  CONCLUSIONS
  Conflicting results in the literature considering apparent diffusion coefficient (ADC) changes in rectal carcinoma under CRT for patients showing T-downstaging are unlikely to be due to perfusion effects. Our data support the view that under effective therapy, an increase in D/ADC can be observed.
authors: Department of Radiology (E010), German Cancer Research Center, INF 280 69120 Heidelberg, Germany.
authors: Maria-Katharina
authors: MK
authors: Ganten
authors: Department of Radiology (E010), German Cancer Research Center, INF 280 69120 Heidelberg, Germany.
authors: Maximilian
authors: M
authors: Schuessler
authors: Department of Medical Physics in Radiology (E020), German Cancer Research Center, Heidelberg, Germany.
authors: Tobias
authors: T
authors: Bäuerle
authors: Department of Radiation Therapy, Ruprecht-Karls University, Heidelberg, Germany.
authors: Marc
authors: M
authors: Muenter
authors: Department of Radiology (E010), German Cancer Research Center, INF 280 69120 Heidelberg, Germany.
authors: Heinz-Peter
authors: HP
authors: Schlemmer
authors: Department of Radiation Therapy, Ruprecht-Karls University, Heidelberg, Germany.
authors: Alexandra
authors: A
authors: Jensen
authors: Department of Pathology, Ruprecht-Karls University, Heidelberg, Germany.
authors: Karsten
authors: K
authors: Brand
authors: Department of Surgery, Ruprecht-Karls University, Heidelberg, Germany.
authors: Margret
authors: M
authors: Dueck
authors: Department of Radiology (E010), German Cancer Research Center, INF 280 69120 Heidelberg, Germany; Department of Radiology, Massachusetts General Hospital, Boston MA, USA.
authors: Julien
authors: J
authors: Dinkel
authors: Department of Biostatistics (C060), Medical Biostatistics German Cancer Research Center, Heidelberg, Germany.
authors: Annette
authors: A
authors: Kopp-Schneider
authors: Medical and Biological Informatics (E130), German Cancer Research Center, Heidelberg, Germany; Quantitative Imaging Based Disease Characterization (E011), German Cancer Research Center, Heidelberg, Germany.
authors: Klaus
authors: K
authors: Fritzsche
authors: Quantitative Imaging Based Disease Characterization (E011), German Cancer Research Center, Heidelberg, Germany.
authors: Bram
authors: B
authors: Stieltjes
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059248:Chemoradiotherapy; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012004:Rectal Neoplasms / Q000473:pathology / Q000628:therapy*; D047368:Tumor Burden