title: (S)-4-(3-18F-fluoropropyl)-L-glutamic acid: an 18F-labeled tumor-specific probe for PET/CT imaging--dosimetry.
abstract: The glutamic acid derivative (S)-4-(3-(18)F-Fluoropropyl)-l-glutamic acid ((18)F-FSPG, alias BAY 94-9392), a new PET tracer for the detection of malignant diseases, displayed promising results in non-small cell lung cancer patients. The aim of this study was to provide dosimetry estimates for (18)F-FSPG based on human whole-body PET/CT measurements.
  
  
  METHODS
  (18)F-FSPG was prepared by a fully automated 2-step procedure and purified by a solid-phase extraction method. PET/CT scans were obtained for 5 healthy volunteers (mean age, 59 y; age range, 51-64 y; 2 men, 3 women). Human subjects were imaged for up to 240 min using a PET/CT scanner after intravenous injection of 299 ± 22.5 MBq of (18)F-FSPG. Image quantification, time-activity data modeling, estimation of normalized number of disintegrations, and production of dosimetry estimates were performed using the RADAR (RAdiation Dose Assessment Resource) method for internal dosimetry and in general concordance with the methodology and principles as presented in the MIRD 16 document.
  
  
  RESULTS
  Because of the renal excretion of the tracer, the absorbed dose was highest in the urinary bladder wall and kidneys, followed by the pancreas and uterus. The individual organ doses (mSv/MBq) were 0.40 ± 0.058 for the urinary bladder wall, 0.11 ± 0.011 for the kidneys, 0.077 ± 0.020 for the pancreas, and 0.030 ± 0.0034 for the uterus. The calculated effective dose was 0.032 ± 0.0034 mSv/MBq. Absorbed dose to the bladder and the effective dose can be reduced significantly by frequent bladder-voiding intervals. For a 0.75-h voiding interval, the bladder dose was reduced to 0.10 ± 0.012 mSv/MBq, and the effective dose was reduced to 0.015 ± 0.0010 mSv/MBq.
  
  
  CONCLUSIONS
  On the basis of the distribution and biokinetic data, the determined radiation dose for (18)F-FSPG was calculated to be 9.5 ± 1.0 mSv at a patient dose of 300 MBq, which is of similar magnitude to that of (18)F-FDG (5.7 mSv). The effective dose can be reduced to 4.5 ± 0.30 mSv (at 300 MBq), with a bladder-voiding interval of 0.75 h.
authors.affiliation: Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München, München, Germany. kamilla.smolarz@tum.de
authors.forename: Kamilla
authors.initials: K
authors.lastname: Smolarz
authors.forename: Bernd Joachim
authors.initials: BJ
authors.lastname: Krause
authors.forename: Frank-Philipp
authors.initials: FP
authors.lastname: Graner
authors.forename: Franziska Martina
authors.initials: FM
authors.lastname: Wagner
authors.forename: Christina
authors.initials: C
authors.lastname: Hultsch
authors.forename: Claudia
authors.initials: C
authors.lastname: Bacher-Stier
authors.forename: Richard B
authors.initials: RB
authors.lastname: Sparks
authors.forename: Susan
authors.initials: S
authors.lastname: Ramsay
authors.forename: Lüder M
authors.initials: LM
authors.lastname: Fels
authors.forename: Ludger M
authors.initials: LM
authors.lastname: Dinkelborg
authors.forename: Markus
authors.initials: M
authors.lastname: Schwaiger
mesh_terms: D005260:Female; D005971:Glutamates / Q000009:adverse effects; D006801:Humans; D007553:Isotope Labeling; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D009369:Neoplasms / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D011874:Radiometry; D012449:Safety; D014057:Tomography, X-Ray Computed
chemical_list: C569271:(4S)-4-(3-(18F)fluoropropyl)-L-glutamate; D005971:Glutamates
keywords: FSPG; PET; oncology; radiation dosimetry