title: Quantification in (68)Ga-DOTA(0)-Phe(1)-Tyr(3)-octreotide positron emission tomography/computed tomography: can we be impartial about partial volume effects?
abstract: OBJECTIVE
  In combined positron emission tomography/computed tomography (PET/CT) of neuroendocrine neoplasms using (68)Ga-DOTA(0)-Phe(1)-Tyr(3)-octreotide ((68)Ga-DOTATOC), partial volume effects (PVEs) may occur in smaller lesions. This study determined the lesional cutoff size for the occurrence of PVEs in a clinical setting.
  
  
  METHODS
  Retrospective assessment of 51 PET/CT examinations (16-slice PET/CT device) for malignant PET foci was carried out. In all foci, the maximal standardized uptake value (SUVmax) and maximal lesion diameter on axial CT was documented. Determined SUVmax and lesional sizes were correlated via LOESS regression. In the resulting curve, the cutoff point for SUVmax size dependency was determined visually and mathematically using 2 approximating straight lines.
  
  
  RESULTS
  In 45 patients, 313 of 413 PET foci found were malignant, measurable on CT and had a roughly spherical geometry (SUVmax: 2.5-103.3, mean ± SD 20.5 ± 15.18; CT diameter: 5-103 mm, mean ± SD 21.8 ± 13.1 mm). The cutoff lesional size for the occurrence of PVEs was 20.4 mm by the mathematical approach and 25 mm by visual assessment.
  
  
  CONCLUSIONS
  In (68)Ga-DOTATOC imaging, the clinical lesional size threshold is far larger than expected from systemic resolution only. Thus, tracer uptake quantification is only acceptable in sufficiently large lesions.
authors.affiliation: Klinik für Radiologie und Nuklearmedizin, Universitätsklinikum Magdeburg A.ö.R., Germany. juri.ruf @ uniklinik-freiburg.de
authors.forename: Juri
authors.initials: J
authors.lastname: Ruf
authors.forename: Jan
authors.initials: J
authors.lastname: Schiefer
authors.forename: Siegfried
authors.initials: S
authors.lastname: Kropf
authors.forename: Christian
authors.initials: C
authors.lastname: Furth
authors.forename: Gerhard
authors.initials: G
authors.lastname: Ulrich
authors.forename: Ortrud
authors.initials: O
authors.lastname: Kosiek
authors.forename: Timm
authors.initials: T
authors.lastname: Denecke
authors.forename: Marianne
authors.initials: M
authors.lastname: Pavel
authors.forename: Andreas
authors.initials: A
authors.lastname: Pascher
authors.forename: Bertram
authors.initials: B
authors.lastname: Wiedenmann
authors.forename: Holger
authors.initials: H
authors.lastname: Amthauer
mesh_terms: D000328:Adult; D000368:Aged; D016000:Cluster Analysis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods / Q000706:statistics & numerical data; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging* / Q000473:pathology*; D015282:Octreotide / Q000031:analogs & derivatives*; D009942:Organometallic Compounds; D049268:Positron-Emission Tomography / Q000379:methods* / Q000706:statistics & numerical data; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods* / Q000706:statistics & numerical data; D047368:Tumor Burden
chemical_list: C499142:Ga(III)-DOTATOC; D009942:Organometallic Compounds; D015282:Octreotide