title: Spatiotemporal analysis of tumor uptake patterns in dynamic (18)FDG-PET and dynamic contrast enhanced CT.
abstract: BACKGROUND
  Molecular and functional imaging techniques such as dynamic positron emission tomography (DPET) and dynamic contrast enhanced computed tomography (DCECT) may provide improved characterization of tumors compared to conventional anatomic imaging. The purpose of the current work was to compare spatiotemporal uptake patterns in DPET and DCECT images.
  
  
  METHODS
  A PET/CT protocol comprising DCECT with an iodine based contrast agent and DPET with (18)F-fluorodeoxyglucose was set up. The imaging protocol was used for examination of three dogs with spontaneous tumors of the head and neck at sessions prior to and after fractionated radiotherapy. Software tools were developed for downsampling the DCECT image series to the PET image dimensions, for segmentation of tracer uptake pattern in the tumors and for spatiotemporal correlation analysis of DCECT and DPET images.
  
  
  RESULTS
  DCECT images evaluated one minute post injection qualitatively resembled the DPET images at most imaging sessions. Segmentation by region growing gave similar tumor extensions in DCECT and DPET images, with a median Dice similarity coefficient of 0.81. A relatively high correlation (median 0.85) was found between temporal tumor uptake patterns from DPET and DCECT. The heterogeneity in tumor uptake was not significantly different in the DPET and DCECT images. The median of the spatial correlation was 0.72.
  
  
  CONCLUSIONS
  DCECT and DPET gave similar temporal wash-in characteristics, and the images also showed a relatively high spatial correlation. Hence, if the limited spatial resolution of DPET is considered adequate, a single DPET scan only for assessing both tumor perfusion and metabolic activity may be considered. However, further work on a larger number of cases is needed to verify the correlations observed in the present study.
authors.affiliation: Department of Medical Physics, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway. eirik.malinen@fys.uio.no
authors.forename: Eirik
authors.initials: E
authors.lastname: Malinen
authors.forename: Jan
authors.initials: J
authors.lastname: Rødal
authors.forename: Ingerid Skjei
authors.initials: IS
authors.lastname: Knudtsen
authors.forename: Åste
authors.initials: Å
authors.lastname: Søvik
authors.forename: Hege Kippenes
authors.initials: HK
authors.lastname: Skogmo
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D003287:Contrast Media; D004285:Dogs; D005260:Female; D019788:Fluorodeoxyglucose F18; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000532:radiotherapy; D006801:Humans; D008297:Male; D049268:Positron-Emission Tomography; D011379:Prognosis; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted; D012984:Software; D014057:Tomography, X-Ray Computed; D055815:Young Adult
chemical_list: D003287:Contrast Media; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18