title: In vivo quantitation of intratumoral radioisotope uptake using micro-single photon emission computed tomography/computed tomography.
abstract: OBJECTIVE
  This study was undertaken to determine the ability of micro-single photon emission computed tomography (micro-SPECT)/computed tomography (CT) to accurately quantitate intratumoral radioisotope uptake in vivo and to compare these measurements with planar imaging and micro-SPECT imaging alone.
  
  
  METHODS
  Human pancreatic cancer xenografts were established in 10 mice. Intratumoral radioisotope uptake was achieved via intratumoral injection of an attenuated measles virus vector expressing the NIS gene (MV-NIS). On various days after MV-NIS injection, (123)I planar and micro-SPECT/CT imaging was performed. Tumor activity was determined by dose calibrator measurements and region-of-interest (ROI) image analysis. Agreement and reproducibility of tumor activity measurements were assessed by Bland-Altman plots and Lin's concordance correlation coefficient (CCC).
  
  
  RESULTS
  Intratumoral radioisotope uptake was detected in all mice. Scatterplots demonstrate strong agreement (CCC = 0.93) between micro-SPECT/CT ROI image analysis and dose calibrator tumor activity measurements. The differences between dose calibrator activity measurements and those obtained with ROI image analysis of micro-SPECT alone and planar imaging are less accurate and more variable (CCC = 0.84 and 0.78, respectively).
  
  
  CONCLUSIONS
  Micro-SPECT/CT can be used to accurately quantify intratumoral radioisotope uptake in vivo and is more reliable than planar or micro-SPECT imaging alone.
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 559005, USA. scarlson@mayo.edu
authors.forename: Stephanie K
authors.initials: SK
authors.lastname: Carlson
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Classic
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Hadac
authors.forename: Claire E
authors.initials: CE
authors.lastname: Bender
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Kemp
authors.forename: Val J
authors.initials: VJ
authors.lastname: Lowe
authors.forename: Tanya L
authors.initials: TL
authors.lastname: Hoskin
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Russell
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D051379:Mice; D008819:Mice, Nude; D013382:Subtraction Technique; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods* / Q000592:standards
chemical_list: D007457:Iodine Radioisotopes