title: Positron detection for the intraoperative localisation of cancer deposits.
abstract: OBJECTIVE
  The study investigated the feasibility of a positron-sensitive hand-held detector system for the intraoperative localisation of tumour deposits resulting from intravenous [(18)F]FDG administration.
  
  
  METHODS
  A total of 17 patients (12 receiving preoperative [(18)F]FDG PET imaging) with various histologically proven malignancies were included. Radioactivity from tumours and surrounding normal tissue was measured on average 3 h after administration of 36-110 MBq [(18)F]FDG and the tumour-to-background (T/B) ratio was calculated. In addition, phantom studies were performed to evaluate the spatial resolution and sensitivity of the probe.
  
  
  RESULTS
  All known targeted tumour sites were identified by the positron probe. T/B ratios were generally high, with a mean T/B ratio of 6.6, allowing easy identification of most tumour sites. In one case of a hepatic metastasis, the T/B ratio of 1.34 was below expectations, since the preoperative [(18)F]FDG PET scan was positive. The probe was instrumental in the localisation of three additional tumour lesions (two lymph nodes, one anastomotic ring) that were not immediately apparent at surgery. Phantom studies revealed that [(18)F]FDG-containing gel (simulating tumour tissue), having 10 times more [(18)F]FDG than surrounding "normal" background gel, was clearly detectable in quantities as low as 15 mg. As measured in two cases, the absorbed radiation doses ranged from 2.5 to 8.6 microSv/h for the surgical team to 0.8 microSv/h for the aesthetician.
  
  
  CONCLUSIONS
  [(18)F]FDG-accumulating tumour tissues can be localised with positron probes intraoperatively with a low radiation burden to the patient and medical personnel. The methodology holds promise for further clinical testing.
authors: Department of Nuclear Medicine, Technische Universität München, Ismaningerstrasse 22, 81675 Munich, Germany. mpiert@umich.edu
authors: Morand
authors: M
authors: Piert
authors: Maria
authors: M
authors: Burian
authors: Günther
authors: G
authors: Meisetschläger
authors: Hubert J
authors: HJ
authors: Stein
authors: Sibylle
authors: S
authors: Ziegler
authors: Jörg
authors: J
authors: Nährig
authors: Maria
authors: M
authors: Picchio
authors: Andreas
authors: A
authors: Buck
authors: Joerg R
authors: JR
authors: Siewert
authors: Markus
authors: M
authors: Schwaiger
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D015902:Gamma Cameras; D006801:Humans; D007430:Intraoperative Care / Q000295:instrumentation* / Q000379:methods; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery*; D049268:Positron-Emission Tomography / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D025321:Surgery, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D014159:Transducers; D016896:Treatment Outcome