title: Post-PET ultrasound improves specificity of 18F-FDG-PET for recurrent differentiated thyroid cancer while maintaining sensitivity.
abstract: BACKGROUND
  Positron emission tomography (PET) using fluor-18-deoxyglucose (18F-FDG) with or without computed tomography (CT) is generally accepted as the most sensitive imaging modality for diagnosing recurrent differentiated thyroid cancer (DTC) in patients with negative whole body scintigraphy with iodine-131 (I-131).
  
  
  OBJECTIVE
  To assess the potential incremental value of ultrasound (US) over 18F-FDG-PET-CT.
  
  
  METHODS
  Fifty-one consecutive patients with suspected recurrent DTC were prospectively evaluated using the following multimodal imaging protocol: (i) US before PET (pre-US) with or without fine needle biopsy (FNB) of suspicious lesions; (ii) single photon emission computed tomography (≥3 GBq I-131) with co-registered CT (SPECT-CT); (iii) 18F-FDG-PET with co-registered contrast-enhanced CT of the neck; (iv) US in correlation with the other imaging modalities (post-US). Postoperative histology, FNB, and long-term follow-up (median, 2.8 years) were taken as composite gold standard.
  
  
  RESULTS
  Fifty-eight malignant lesions were identified in 34 patients. Forty lesions were located in the neck or upper mediastinum. On receiver operating characteristics (ROC) analysis, 18F-FDG-PET had a limited lesion-based specificity of 59% at a set sensitivity of 90%. Pre-US had poor sensitivity and specificity of 52% and 53%, respectively, increasing to 85% and 94% on post-US, with knowledge of the PET/CT findings (P < 0.05 vs. PET and pre-US). Multimodal imaging changed therapy in 15 out of 51 patients (30%).
  
  
  CONCLUSIONS
  In patients with suspected recurrent DTC, supplemental targeted US in addition to 18F-FDG-PET-CT increases specificity while maintainin sensitivity, as non-malignant FDG uptake in cervical lesions can be confirmed.
authors.affiliation: Nuclear Medicine/PET Center, Department of Radiology, Haukeland University Hospital, Bergen/Norway Department of Clinical Medicine, University of Bergen, Bergen/Norway martin.biermann@k1.uib.no.
authors.forename: Martin
authors.initials: M
authors.lastname: Biermann
authors.affiliation: Department of Clinical Medicine, University of Bergen, Bergen/Norway Section for Neuroradiology, Department of Radiology, Haukeland University Hospital, Bergen/Norway.
authors.forename: Jostein
authors.initials: J
authors.lastname: Kråkenes
authors.affiliation: Section for Endocrine Surgery, Haukeland University Hospital, Bergen/Norway.
authors.forename: Katrin
authors.initials: K
authors.lastname: Brauckhoff
authors.affiliation: Department of Pathology, Haukeland University Hospital, Bergen/Norway.
authors.forename: Hans Kristian
authors.initials: HK
authors.lastname: Haugland
authors.affiliation: Institute of Biostatistics and Clinical Research, University of Münster, Münster/Germany.
authors.forename: Achim
authors.initials: A
authors.lastname: Heinecke
authors.affiliation: Department of Clinical Medicine, University of Bergen, Bergen/Norway Centre for Cancer Biomarkers CCBIO, University of Bergen, Bergen/Norway.
authors.forename: Lars A
authors.initials: LA
authors.lastname: Akslen
authors.affiliation: Section for Endocrine Surgery, Haukeland University Hospital, Bergen/Norway Department of Clinical Science, University of Bergen, Bergen/Norway.
authors.forename: Jan Erik
authors.initials: JE
authors.lastname: Varhaug
authors.affiliation: Section for Endocrine Surgery, Haukeland University Hospital, Bergen/Norway Department of Clinical Science, University of Bergen, Bergen/Norway.
authors.forename: Michael
authors.initials: M
authors.lastname: Brauckhoff
mesh_terms: D000328:Adult; D000368:Aged; D044963:Biopsy, Fine-Needle; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: Head/neck; PET; computed tomography (CT); neoplasms; thyroid; ultrasound