title: Assessing treatment response of osteolytic lesions by manual volumetry, automatic segmentation, and RECIST in experimental bone metastases.
abstract: OBJECTIVE
  Aim of the study was to compare between volumetric and unidimensional approaches for treatment response monitoring in a nude rat model of experimental bone metastases. For the volumetric approach, an automated segmentation algorithm of osteolytic lesions was introduced and compared to manual volumetry.
  
  
  METHODS
  Nude rats bearing osteolytic metastases were treated with zoledronate and sunitinib and compared to controls. Treatment response was assessed longitudinally in vivo using flat-panel volumetric computed tomography at days 30, 35, 45, and 55 after tumor cell inoculation. The mean sizes and volumes of osteolytic lesions were determined according to response evaluation criteria in solid tumors (RECIST) and by automated and manual volumetry (software: MITK [The Medical Imaging Interaction Toolkit, Heidelberg, Germany] and VIRTUOS, Heidelberg, Germany).
  
  
  RESULTS
  In contrary to RECIST, the manual volumetric approach indicated a significant decrease in osteolytic lesion volume in response to treatment. The presented automatic segmentation algorithm for treatment monitoring identified bone metastases adequately and assessed changes in the osteolytic lesion volume over time according to manual volumetry.
  
  
  CONCLUSIONS
  In an animal model, volumetric treatment response assessment of osteolytic bone metastases is superior to unidimensional measurements, and automated volumetric segmentation may be a valuable alternative to manual volume determination.
authors.affiliation: Department of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Maren
authors.initials: M
authors.lastname: Bretschi
authors.affiliation: Department of Medical Physics in Radiation Oncology, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Fränzle
authors.affiliation: Department of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany; Department of Hematology, Oncology, and Rheumatology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Merz
authors.affiliation: Department of Hematology, Oncology, and Rheumatology, University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Hillengass
authors.affiliation: Department of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Wolfhard
authors.initials: W
authors.lastname: Semmler
authors.affiliation: Department of Medical Physics in Radiation Oncology, German Cancer Research Center, Heidelberg, Germany; Department of Medical Informatics, Heilbronn University, Heilbronn, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Bendl
authors.affiliation: Department of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany; Institute of Radiology, University Hospital Erlangen, Maximiliansplatz 1, 90154 Erlangen, Germany. Electronic address: tobias.baeuerle@uk-erlangen.de.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bäuerle
mesh_terms: D000465:Algorithms; D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use; D050071:Bone Density Conservation Agents / Q000627:therapeutic use; D001859:Bone Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D004164:Diphosphonates / Q000627:therapeutic use*; D004195:Disease Models, Animal; D005500:Follow-Up Studies; D007093:Imidazoles / Q000627:therapeutic use*; D007211:Indoles / Q000627:therapeutic use*; D011758:Pyrroles / Q000627:therapeutic use*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D051381:Rats; D011923:Rats, Nude; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D000077210:Sunitinib; D016896:Treatment Outcome; D000077211:Zoledronic Acid
chemical_list: D000970:Antineoplastic Agents; D050071:Bone Density Conservation Agents; D004164:Diphosphonates; D007093:Imidazoles; D007211:Indoles; D011758:Pyrroles; D000077211:Zoledronic Acid; D000077210:Sunitinib
keywords: Bone metastases; CT; RECIST (response evaluation criteria in solid tumors); therapy response; volumetric analysis