title: Factors affecting tumor (18) F-FDG uptake in longitudinal mouse PET studies.
abstract: BACKGROUND
  Many biological factors of 2-[(18) F]fluoro-2-deoxy-d-glucose ((18) F-FDG) in blood can affect (18) F-FDG uptake in tumors. In this study, longitudinal (18) F-FDG positron emission tomography (PET) studies were performed on tumor-bearing mice to investigate the effect of blood glucose level and tumor size on (18) F-FDG uptake in tumors.
  
  
  METHODS
  Six- to eight-week-old severe combined immunodeficiency mice were implanted with glioblastoma U87 (n = 8) or adenocarcinoma MDA-MB-231 (MDA) (n = 11) in the shoulder. When the tumor diameter was approximately 2.5 mm, a 60-min dynamic (18) F-FDG PET scan was performed weekly until the tumor diameter reached 10 mm. Regions of interests were defined in major organs and tumor. A plasma curve was derived based on a modeling method that utilizes the early heart time-activity curve and a late-time blood sample. The (18) F-FDG uptake constant K i was calculated using Patlak analysis on the tumors without an apparent necrotic center shown in the PET images. For each tumor type, the measured K i was corrected for partial volume (PV), and multivariate regression analysis was performed to examine the effects of blood glucose level ([Glc]) and tumor growth. Corrected Akaike's information criterion was used to determine the best model.
  
  
  RESULTS
  The regression model that best fit the PV-corrected K i for U87 data was K i /RC = (1/[Glc]) × (0.27 ± 0.027) mL/min/mL (where [Glc] is in mmol/L), and for MDA, it was K i /RC = (0.04 ± 0.005) mL/min/mL, where K i /RC denotes the PV-corrected K i using an individual recovery coefficient (RC). The results indicated that (18) F-FDG K i /RC for U87 was inversely related to [Glc], while [Glc] had no effect on (18) F-FDG K i /RC of MDA. After the effects of PV and [Glc] were accounted for, the data did not support any increase of (18) F-FDG K i as the tumor (of either type) grew larger in size.
  
  
  CONCLUSIONS
  The effect of [Glc] on the tumor (18) F-FDG K i was tumor-dependent. PV- and [Glc]-corrected (18) F-FDG K i did not show significant increase as the tumor of either type grew in size.
authors.affiliation: Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Rm. B2-085H CHS, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Sha
authors.affiliation: Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Rm. B2-085H CHS, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA.
authors.forename: Hu
authors.initials: H
authors.lastname: Ye
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
authors.forename: Keisuke S
authors.initials: KS
authors.lastname: Iwamoto
authors.affiliation: Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Rm. B2-085H CHS, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA.
authors.forename: Koon-Pong
authors.initials: KP
authors.lastname: Wong
authors.affiliation: Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Rm. B2-085H CHS, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA ; Department of Biomathematics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
authors.forename: Moses Quinn
authors.initials: MQ
authors.lastname: Wilks
authors.affiliation: Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Rm. B2-085H CHS, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA.
authors.forename: David
authors.initials: D
authors.lastname: Stout
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
authors.forename: William
authors.initials: W
authors.lastname: McBride
authors.affiliation: Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA, Rm. B2-085H CHS, 10833 Le Conte Avenue, Los Angeles, CA 90095, USA ; Department of Biomathematics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
authors.forename: Sung-Cheng
authors.initials: SC
authors.lastname: Huang
keywords: F-FDG; Glucose; Kinetic; PET; Tumor