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PET/CT is widely used for the evaluation of patients with thoracic malignancies. Although the levels of 18F-fluorodeoxyglucose (FDG) uptake are usually high in neoplastic diseases, they can also be physiological, due to artifacts. In addition, FDG uptake can occur in benign conditions such as infectious, inflammatory, and iatrogenic lesions. Furthermore, some malignant tumors, such as adenocarcinoma in situ (formerly known as bronchoalveolar carcinoma) and carcinoid tumors, may not show FDG uptake. Here, we illustrate the main pitfalls and artifacts in the interpretation of the results of oncologic PET/CT of the chest, outlining strategies for avoiding misinterpretation.
PET/CT é amplamente utilizada para avaliação de pacientes com neoplasias torácicas. Altos níveis de captação de 18F-fluordesoxiglicose (FDG) são geralmente vistos em neoplasias, mas também podem ser fisiológicos, decorrentes de artefatos ou ocorrerem em condições benignas, como lesões infecciosas, inflamatórias e iatrogênicas. Por outro lado, alguns tumores malignos podem não captar FDG, como o adenocarcinoma in situ (anteriormente denominado de carcinoma bronquioloalveolar) e tumores carcinoides. Os autores ilustram as principais armadilhas e artefatos na interpretação dos exames torácicos de PET/CT oncológicos, com estratégias para evitar erros de interpretação.
Positron emission tomography/computed tomography (PET/CT) imaging has been the subject of a series of recent publications in the radiology literature in Brazil(1-10). PET/CT is an integral part of the management of patients with thoracic neoplasms, improving staging, monitoring of therapy, and prognostic assessment. However, many artifacts and pitfalls can be seen on the examination, such as normal variants, physiological areas of 18F-fluorodeoxyglucose (FDG) uptake, acquisition or reconstruction artifacts, and false-positive or false-negative results.
The purpose of this essay was to describe and illustrate the main pitfalls and artifacts in the interpretation of oncologic PET/CT examinations of the chest and to present strategies for avoiding their ‘misinterpretation.
FDG uptake in PET/CT can be seen in active tissues with high glucose metabolism. High physiological uptake of FDG typically occurs in the brain, lymphoid tissue, liver, spleen, kidneys, and urinary tract(11). In the thorax, normal metabolic activity can be seen in the myocardium(12), great vessels, esophagus, thymus, breast (especially of lactating females), bone marrow, muscles, and brown fat (Figure 1)(13).
False-positive FDG uptake can occur in infections, inflammatory lesions, benign tumors, and iatrogenic conditions such as surgical manipulation, pleurodesis, radiation therapy, and granulocyte-colony-stimulating factor administration, as well as after chemotherapy (Figures 2--1010)(13-17).
Awareness of normal FDG distribution, physiological FDG uptake, and their variants is mandatory for interpreting oncologic PET/CT examinations of the chest. False-positive and false-negative results can be avoided if the reader has knowledge of their main aspects and interprets the CT and PET findings carefully. When these points are well known by the radiologist, PET/CT is a powerful imaging technique for characterizing pulmonary lesions, providing accurate staging for lung neoplasms and contributing to better evaluation of the effectiveness of therapy and prognostic assessment.
Study conducted by the Grupo Fleury, São Paulo, SP, Brazil.