title: Focal uptake of 68Ga-DOTATOC in the pancreas: pathological or physiological correlate in patients with neuroendocrine tumours?
abstract: OBJECTIVE
  Neuroendocrine tumours are frequently located in the upper abdomen and especially in the pancreas. Imaging of the abdomen with somatostatin analogs such as (68)Ga-DOTA-Phe(1)-Tyr(3)-octreotide (DOTATOC) is a standard approach for imaging neuroendocrine cancer, but is still challenging due to physiological and technical considerations in this area. Therefore, the aim of this study was to further investigate the origin of (68)Ga-DOTATOC findings in the pancreas.
  
  
  METHODS
  Forty-three consecutive patients with neuroendocrine tumours were examined by (68)Ga-DOTATOC positron emission tomography (PET)/CT for staging or restaging. As imaging of the upper abdomen is frequently affected by breathing artefacts, PET and CT data were analysed for misalignment and rearranged if necessary. Any noticeable uptake in the pancreas was described. Tracer uptake in the head of the pancreas and the liver was measured by means of maximum and average standard uptake value (SUV(max), SUV(av)). The reference standards (malignant versus benign) for correlation with PET findings were clinical and radiological follow-up (mean follow-up time 14 months) (n = 37) or histological confirmation (n = 6).
  
  
  RESULTS
  In 23 of 43 studies (54%) misalignment between PET and CT data was found with a mean value of 1.4 cm. Visual assessment demonstrated that 20 of 43 scans (46.6%) showed no uptake in the head of the pancreas. Of 43 scans, 23 (53.4%) showed noticeable uptake with focal pattern in the head of the pancreas in 10 scans and irregular pattern in 13 scans. Follow-up indicated malignant pancreatic lesions in three patients. The pancreatic head to liver SUV(av) ratios in these patients ranged from 1.62 to 6.85, whereas in cases of uptake without known malignancy ratios ranged from 0.56 to 1.19. Considering SUV(max), the ratio ranged from 3.24 to 9.1 and from 0.84 to 1.47, respectively. No statistically significant difference was noted between uptake in the head of the pancreas and the liver in patients without malignant pancreatic tumours (p > 0.05).
  
  
  CONCLUSIONS
  (68)Ga-DOTATOC uptake in the head of the pancreas is a common finding in patients undergoing (68)Ga-DOTATOC PET/CT. However, this finding most likely represents a physiological condition, especially if the uptake in the pancreatic head is similar to the uptake in the liver (uptake ratio head to liver SUV(av) < 1.4). Therefore, quantification is recommended to avoid false-positive diagnosis. Misalignment due to respiratory motion must always be taken into account.
authors.affiliation: Nuklearmedizinische Klinik und Poliklinik, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Str. 22, 81675, Munich, Germany.
authors.forename: Akram
authors.initials: A
authors.lastname: Al-Ibraheem
authors.forename: Ralph Alexander
authors.initials: RA
authors.lastname: Bundschuh
authors.forename: Johannes
authors.initials: J
authors.lastname: Notni
authors.forename: Andreas
authors.initials: A
authors.lastname: Buck
authors.forename: Anna
authors.initials: A
authors.lastname: Winter
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Wester
authors.forename: Markus
authors.initials: M
authors.lastname: Schwaiger
authors.forename: Klemens
authors.initials: K
authors.lastname: Scheidhauer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001692:Biological Transport; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging / Q000378:metabolism*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000378:metabolism; D009942:Organometallic Compounds / Q000378:metabolism*; D010179:Pancreas / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology / Q000502:physiology; D049268:Positron-Emission Tomography; D014057:Tomography, X-Ray Computed
chemical_list: C499142:Ga(III)-DOTATOC; D009942:Organometallic Compounds; D015282:Octreotide