To compare the interobserver agreement and degree of confidence in anatomical localisation of lesions using 2-[fluorine-18]fluoro-2-deoxy- D -glucose ( 18 F-FDG) positron emission tomography (PET)/computed tomography (CT) and 18 F-FDG PET alone in patients with head and neck tumours. A prospective study of 24 patients (16 male, eight female, median age 59 years) with head and neck tumours was undertaken. 18 F-FDG PET/CT was performed for staging purposes. 2D images were acquired over the head and neck area using a GE Discovery LS™ PET/CT scanner. 18 F-FDG PET images were interpreted by three independent observers. The observers were asked to localise abnormal 18 F-FDG activity to an anatomical territory and score the degree of confidence in localisation on a scale from 1 to 3 (1=exact region unknown; 2=probable; 3=definite). For all 18 F-FDG-avid lesions, standardised uptake values (SUVs) were also calculated. After 3 weeks, the same exercise was carried out using 18 F-FDG PET/CT images, where CT and fused volume data were made available to observers. The degree of interobserver agreement was measured in both instances. A total of six primary lesions with abnormal 18 F-FDG uptake (SUV range 7.2–22) were identified on 18 F-FDG PET alone and on 18 F-FDG PET/CT. In all, 15 nonprimary tumour sites were identified with 18 F-FDG PET only (SUV range 4.5–11.7), while 17 were identified on 18 F-FDG PET/CT. Using 18 F-FDG PET only, correct localisation was documented in three of six primary lesions, while 18 F-FDG PET/CT correctly identified all primary sites. In nonprimary tumour sites, 18 F-FDG PET/CT improved the degree of confidence in anatomical localisation by 51%. Interobserver agreement in assigning primary and nonprimary lesions to anatomical territories was moderate using 18 F-FDG PET alone (kappa coefficients of 0.45 and 0.54, respectively), but almost perfect with 18 F-FDG PET/CT (kappa coefficients of 0.90 and 0.93, respectively). We conclude that 18 F-FDG PET/CT significantly increases interobserver agreement and confidence in disease localisation of 18 F-FDG-avid lesions in patients with head and neck cancers.

Tumour thrombus is a rare complication of many solid cancers including renal cell carcinoma, Wilms' tumour, testicular tumour, adrenal cortical carcinoma, lymphoma, pancreatic cancer, osteosarcoma and Ewing's sarcoma. We describe six patients who harboured occult tumour thrombus detected by fluorine-18 fluorodeoxyglucose (F-FDG) positron emission tomography (PET)/X-ray computerized tomography (CT) imaging as part of the staging investigations. Recognition of this rare complication by PET/CT can change the management plan and prevent unnecessary long-term anti-coagulation treatment because of wrong diagnosis of cancer-related venous thrombus.

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This novel, full bladder 99mtechnetium-mercaptoacetyltriglycine scintigraphic technique provides the ability to detect bladder volumes at which obstructive outflow patterns develop in patients with severe bladder dysfunction.