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A 66-year-old man with left pyriform fossa squamous cell carcinoma (T2N0) was treated with chemoradiation. Nine months later, an emergency tracheostomy was performed for respiratory distress. Contrast-enhanced neck and thorax CT demonstrated a right pyriform mass. FDG-PET/CT showed linear increased uptake extending superiorly from the tracheostomy to the right Eustachian tube and inferiorly to the posterior mediastinum. Postmortem examination confirmed a 7 × 2.2 cm abscess extending from the right parapharyngeal, peritracheal, and prevertebral structures to the mediastinum.

A 43-year-old woman presented with a nodular melanoma treated with wide excision, split skin graft, and sentinel node biopsy. At 2-year follow up, she was noted to have clinical recurrence at the excision site. FDG PET/CT demonstrated in-transit metastasis in her left thigh in addition to disease at the site of the sentinel node biopsy. Isolated limb infusion was performed with melphalan and dactinomycin. PET/CT at 5 weeks demonstrated resolution of the in-transit metastasis and the disease at the excision site. This report of PET/CT demonstrates the effectiveness of chemotherapy for malignant melanoma delivered by isolated limb infusion.

A rapidly emerging clinical application of positron emission tomography (PET) is the detection of tumor tissue at whole-body studies performed with the glucose analogue 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG). High rates of recurrence after partial hepatic resection in patients with colorectal cancer liver metastases indicate that current presurgical imaging strategies are failing to show extrahepatic tumor deposits. Although FDG PET cannot match the anatomic resolution of conventional imaging techniques in the liver and the lungs, it is particularly useful for identification and characterization of extrahepatic disease. FDG PET can show foci of metastatic disease that may not be apparent at conventional anatomic imaging and can aid in the characterization of indeterminate soft-tissue masses. Several sources of benign and physiologic increased activity at FDG PET emphasize the need for careful correlation with findings of other imaging studies and clinical findings. FDG PET can improve the selection of patients for partial hepatic resection and thereby reduce the morbidity and mortality associated with inappropriate surgery.

Objective: Many studies have reported the use of attenuation-corrected positron emission tomography with 18F-fluorodeoxyglucose (FDG PET) with full-ring tomographs to differentiate between benign and malignant pulmonary nodules. We sought to evaluate FDG PET using a partial-ring tomograph without attenuation correction., Methods: A retrospective review of PET images from 77 patients (range 38-84 years of age) with proven benign or malignant pulmonary nodules was undertaken. All images were obtained using a Siemens/CTI ECAT ART tomograph, without attenuation correction, after 185 MBq 18F-FDG was injected. Images were visually graded on a 5-point scale from "definitely malignant" to "definitely benign," and lesion-to-background (LB) ratios were calculated using region of interest analysis. Visual and semiquantitative analyses were compared using receiver operating characteristic analysis., Results: Twenty lesions were benign and 57 were malignant. The mean LB ratio for benign lesions was 1.5 (range 1.0-5.7) and for malignant lesions 5.7 (range 1.2-14.1) (p < 0.001). The area under the ROC curve for LB ratio analysis was 0.95, and for visual analysis 0.91 (p = 0.39). The optimal cut-off ratio with LB ratio analysis was 1.8, giving a sensitivity of 95% and a specificity of 85%. For lesions thought to be "definitely malignant" on visual analysis, the sensitivity was 93% and the specificity 85%. Three proven infective lesions were rated as malignant by both techniques (LB ratio 2.6-5.7)., Conclusions: FDG PET without attenuation correction is accurate for differentiating between benign and malignant lung nodules. Results using simple LB ratios without attenuation correction compare favourably with the published sensitivity and specificity for standard uptake ratios. Visual analysis is equally accurate.