title: Functional imaging to monitor vascular and metabolic response in canine head and neck tumors during fractionated radiotherapy.
abstract: Radiotherapy causes alterations in tumor biology, and non-invasive early assessment of such alterations may become useful for identifying treatment resistant disease. The purpose of the current work is to assess changes in vascular and metabolic features derived from functional imaging of canine head and neck tumors during fractionated radiotherapy. Material and methods. Three dogs with spontaneous head and neck tumors received intensity-modulated radiotherapy (IMRT). Contrast-enhanced cone beam computed tomography (CE-CBCT) at the treatment unit was performed at five treatment fractions. Dynamic (18)FDG-PET (D-PET) was performed prior to the start of radiotherapy, at mid-treatment and at 3-12 weeks after the completion of treatment. Tumor contrast enhancement in the CE-CBCT images was used as a surrogate for tumor vasculature. Vascular and metabolic tumor parameters were further obtained from the D-PET images. Changes in these tumor parameters were assessed, with emphasis on intra-tumoral distributions. Results. For all three patients, metabolic imaging parameters obtained from D-PET decreased from the pre- to the inter-therapy session. Correspondingly, for two of three patients, vascular imaging parameters obtained from both CE-CBCT and D-PET increased. Only one of the tumors showed a clear metabolic response after therapy. No systematic changes in the intra-tumor heterogeneity in the imaging parameters were found. Conclusion. Changes in vascular and metabolic parameters could be detected by the current functional imaging methods. Vascular tumor features from CE-CBCT and D-PET corresponded well. CE-CBCT is a potential method for easy response assessment when the patient is at the treatment unit.
authors.affiliation: Department of Medical Physics, Oslo University Hospital , Oslo , Norway.
authors.forename: Jan
authors.initials: J
authors.lastname: Rødal
authors.forename: Espen
authors.initials: E
authors.lastname: Rusten
authors.forename: Åste
authors.initials: Å
authors.lastname: Søvik
authors.forename: Hege Kippenes
authors.initials: HK
authors.lastname: Skogmo
authors.forename: Eirik
authors.initials: E
authors.lastname: Malinen
mesh_terms: D000818:Animals; D054893:Cone-Beam Computed Tomography; D004283:Dog Diseases / Q000175:diagnosis* / Q000378:metabolism / Q000532:radiotherapy; D004285:Dogs; D019583:Dose Fractionation, Radiation; D019788:Fluorodeoxyglucose F18; D006258:Head and Neck Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000532:radiotherapy; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18