Читать книгу Respiratory Medicine - Stephen J. Bourke - Страница 116

Positron emission tomography (PET) scanning is critical in the diagnosis and staging of lung cancer. It is based on the concept that neoplastic cells have greater metabolic activity and a higher uptake of glucose than normal cells. ¹⁸F‐fluoro‐2‐deoxyglucose (FDG) is a glucose analogue that is preferentially taken up by neoplastic cells after intravenous injection and then emits positrons. In lung cancer staging, PET scanning is used to detect metastases and to determine involvement of lymph nodes in patients being considered for radical treatment such as surgical resection or high‐dose radiotherapy (see Chapter 12). It is also particularly useful in the differential diagnosis of an indeterminate solitary pulmonary nodule. Often such a nodule is small and not amenable to biopsy. Calcification or lack of growth of the lesion over time suggest that the nodule is benign (e.g. hamartoma, healed tuberculous granuloma). If the patient is a smoker at high risk of cancer and otherwise fit, it may be advisable to proceed directly to surgical resection of such a lesion without preoperative histological confirmation. Active accumulation of FDG in the lesion on PET scanning suggests malignancy. False‐negative findings can occur in tumours <1 cm and false‐positive uptake can occur in inflammatory conditions such as tuberculosis, sarcoidosis, histoplasmosis and coccidioidomycosis.