Pitfalls and artifacts in the interpretation of oncologic PET/CT of the chest

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.

Keywords:
Pitfalls; Chest; PET/CT; Oncology

Authorship

Gustavo de Souza Portes Meirelles Mailing address: Dr. Gustavo de Souza Portes Meirelles, Rua Cincinato Braga, 282, Bela Vista, São Paulo, SP, Brazil, 01333-010. E-mail: gustavo.meirelles@grupofleury.com.br

MD, PhD, Postdoctoral work in PET/CT, Medical Coordinator of the Grupo Fleury, São Paulo, SP, Brazil.Grupo FleuryBrazilSão Paulo, SP, BrazilMD, PhD, Postdoctoral work in PET/CT, Medical Coordinator of the Grupo Fleury, São Paulo, SP, Brazil.

Julia Capobianco

MD, Specialist in PET/CT, Radiologist for the Grupo Fleury, São Paulo, SP, Brazil.Grupo FleuryBrazilSão Paulo, SP, BrazilMD, Specialist in PET/CT, Radiologist for the Grupo Fleury, São Paulo, SP, Brazil.

Marco Antônio Condé de Oliveira

Nuclear Medicine Physician for the Grupo Fleury, São Paulo, SP, Brazil.Grupo FleuryBrazilSão Paulo, SP, BrazilNuclear Medicine Physician for the Grupo Fleury, São Paulo, SP, Brazil.

Mailing address: Dr. Gustavo de Souza Portes Meirelles, Rua Cincinato Braga, 282, Bela Vista, São Paulo, SP, Brazil, 01333-010. E-mail: gustavo.meirelles@grupofleury.com.br

SCIMAGO INSTITUTIONS RANKINGS

Nuclear Medicine Physician for the Grupo Fleury, São Paulo, SP, Brazil.Grupo FleuryBrazilSão Paulo, SP, BrazilNuclear Medicine Physician for the Grupo Fleury, São Paulo, SP, Brazil.

Figures

Figures (13)

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Figure 1
Causes of physiological FDG uptake in the thorax.A: A 6-year-old boy, with normal metabolic activity in the thymus. The strategy for differentiating between focal uptake in the anterior mediastinum and a lesion is to look at the normal aspect of the thymus on CT images. B: A 56-year-old man with lung cancer and a forceful cough during the PET/CT examination. FDG PET/CT shows increased metabolic activity in the thoracic muscles, due to vigorous coughing. C: A 31-year-old lactating woman, with normal FDG uptake in the breast. Lactation induces higher metabolic activity in the breasts, which should not be interpreted as disease. D: A 28-year-old man with testicular cancer. Multiple areas of FDG uptake in the supraclavicular regions and in the upper mediastinum, consistent with increased metabolic activity in brown fat, which regulates body weight and temperature and can be activated by satiety or cold environments.

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Figure 2
A 57-year-old female with cough, fever, and multiple centrilobular pulmonary nodules in the superior segment of the left lower lobe (arrows). PET/CT was performed and showed increased FDG uptake (arrow) in the lung nodules. A CT-guided pulmonary biopsy confirmed the diagnosis of pulmonary tuberculosis.

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Figure 3
A 57-year-old man, current smoker, with non-Hodgkin lymphoma and a spiculated pulmonary nodule (arrows) in the left upper lobe, with high FDG uptake. Surgical resection confirmed the diagnosis of pulmonary cryptococcosis.

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Figure 4
A 74-year-old man with esophageal cancer and multiple areas of ground-glass opacities with FDG uptake in the right lung, consistent with bacterial pneumonia.

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Figure 5
A 42-year-old man with a lobulated pulmonary nodule in the right lower lobe (arrows), indeterminate on CT. PET/CT was performed and showed increased metabolic activity (arrow) in the lung nodule, which was surgically resected and was found to be consistent with pulmonary meningioma.

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Figure 6
A 81-year-old man with an occupational history of asbestos exposure. PET/CT images demonstrate high metabolic activity in the left lower lobes, especially in the cortical regions. CT images depict interstitial lung abnormalities, with ground-glass opacities, reticulation, and mild bronchiolectasis.

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Figure 7
A 78-year-old woman submitted to PET/CT for the staging of a cervical carcinoma, with increased FDG uptake in bilateral subscapular masses (arrows), consistent with elastofibroma dorsi.

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Figure 8
Postoperative PET/CT of a patient with history of cardiac tumor. Note the diffuse FDG uptake in the sternum, consistent with inflammatory changes induced by the surgical procedure (arrows). Also note the increased metabolic activity in areas of brown fat in the supraclavicular and paravertebral regions (dashed arrows).

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Figure 9
A 64-year-old woman submitted to PET/CT for the restaging of lung cancer. Multiple foci of FDG uptake are seen in the right pleura (arrows), consistent with an inflammatory process induced by pleurodesis. A careful analysis of CT images demonstrates the high-attenuation pleural thickening, characteristic of pleurodesis.

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Figure 10
A 41-year-old woman with a history of Hodgkin lymphoma and paramediastinal opacities with FDG uptake (arrows), consistent with inflammatory lesions induced by radiation therapy.

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Figure 11
A 63-year-old male, current smoker, with a ground-glass nodule in the right lung (arrow), which had consistently increased in size over the years. PET/CT was performed and was negative. Surgical resection confirmed the diagnosis of adenocarcinoma in situ (formerly known as bronchoalveolar carcinoma). PET/CT is limited for these conditions and should not be used for small nodules with groundglass attenuation, due to the high pretest probability of false-negative results.

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Figure 12
A 57-year-old woman with breast cancer and focal FDG uptake in a left axillary lymph node (arrow). That uptake is consistent with extravasation of FDG in the left arm, draining to the ipsilateral axillary region.

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Figure 13
A 78-year-old man with a pacemaker in his left hemithorax (arrow). A PET attenuation-corrected image shows FDG uptake in the left hemithorax, consistent with an artifact induced by attenuation correction. In cases of uncertainty, the non-attenuation-corrected image can be used in order to avoid misinterpretation.

Figure 1 Causes of physiological FDG uptake in the thorax.A: A 6-year-old boy, with normal metabolic activity in the thymus. The strategy for differentiating between focal uptake in the anterior mediastinum and a lesion is to look at the normal aspect of the thymus on CT images. B: A 56-year-old man with lung cancer and a forceful cough during the PET/CT examination. FDG PET/CT shows increased metabolic activity in the thoracic muscles, due to vigorous coughing. C: A 31-year-old lactating woman, with normal FDG uptake in the breast. Lactation induces higher metabolic activity in the breasts, which should not be interpreted as disease. D: A 28-year-old man with testicular cancer. Multiple areas of FDG uptake in the supraclavicular regions and in the upper mediastinum, consistent with increased metabolic activity in brown fat, which regulates body weight and temperature and can be activated by satiety or cold environments.

Figure 2 A 57-year-old female with cough, fever, and multiple centrilobular pulmonary nodules in the superior segment of the left lower lobe (arrows). PET/CT was performed and showed increased FDG uptake (arrow) in the lung nodules. A CT-guided pulmonary biopsy confirmed the diagnosis of pulmonary tuberculosis.

Figure 3 A 57-year-old man, current smoker, with non-Hodgkin lymphoma and a spiculated pulmonary nodule (arrows) in the left upper lobe, with high FDG uptake. Surgical resection confirmed the diagnosis of pulmonary cryptococcosis.

Figure 4 A 74-year-old man with esophageal cancer and multiple areas of ground-glass opacities with FDG uptake in the right lung, consistent with bacterial pneumonia.

Figure 5 A 42-year-old man with a lobulated pulmonary nodule in the right lower lobe (arrows), indeterminate on CT. PET/CT was performed and showed increased metabolic activity (arrow) in the lung nodule, which was surgically resected and was found to be consistent with pulmonary meningioma.

Figure 6 A 81-year-old man with an occupational history of asbestos exposure. PET/CT images demonstrate high metabolic activity in the left lower lobes, especially in the cortical regions. CT images depict interstitial lung abnormalities, with ground-glass opacities, reticulation, and mild bronchiolectasis.

Figure 7 A 78-year-old woman submitted to PET/CT for the staging of a cervical carcinoma, with increased FDG uptake in bilateral subscapular masses (arrows), consistent with elastofibroma dorsi.

Figure 8 Postoperative PET/CT of a patient with history of cardiac tumor. Note the diffuse FDG uptake in the sternum, consistent with inflammatory changes induced by the surgical procedure (arrows). Also note the increased metabolic activity in areas of brown fat in the supraclavicular and paravertebral regions (dashed arrows).

Figure 9 A 64-year-old woman submitted to PET/CT for the restaging of lung cancer. Multiple foci of FDG uptake are seen in the right pleura (arrows), consistent with an inflammatory process induced by pleurodesis. A careful analysis of CT images demonstrates the high-attenuation pleural thickening, characteristic of pleurodesis.

Figure 10 A 41-year-old woman with a history of Hodgkin lymphoma and paramediastinal opacities with FDG uptake (arrows), consistent with inflammatory lesions induced by radiation therapy.

Figure 11 A 63-year-old male, current smoker, with a ground-glass nodule in the right lung (arrow), which had consistently increased in size over the years. PET/CT was performed and was negative. Surgical resection confirmed the diagnosis of adenocarcinoma in situ (formerly known as bronchoalveolar carcinoma). PET/CT is limited for these conditions and should not be used for small nodules with groundglass attenuation, due to the high pretest probability of false-negative results.

Figure 12 A 57-year-old woman with breast cancer and focal FDG uptake in a left axillary lymph node (arrow). That uptake is consistent with extravasation of FDG in the left arm, draining to the ipsilateral axillary region.

Figure 13 A 78-year-old man with a pacemaker in his left hemithorax (arrow). A PET attenuation-corrected image shows FDG uptake in the left hemithorax, consistent with an artifact induced by attenuation correction. In cases of uncertainty, the non-attenuation-corrected image can be used in order to avoid misinterpretation.

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Métricas

Pitfalls and artifacts in the interpretation of oncologic PET/CT of the chest

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Mensagem

[1] Mailing address: Dr. Gustavo de Souza Portes Meirelles, Rua Cincinato Braga, 282, Bela Vista, São Paulo, SP, Brazil, 01333-010. E-mail: gustavo.meirelles@grupofleury.com.br