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FDG-PET/CT pitfalls in oncological head and neck imaging.

Purohit BS, Ailianou A, Dulguerov N, Becker CD, Ratib O, Becker M - Insights Imaging (2014)

Bottom Line: The commonly encountered false-positive PET/CT interpretation pitfalls are due to high FDG uptake by physiological causes, benign thyroid nodules, unilateral cranial nerve palsy and increased FDG uptake due to inflammation, recent chemoradiotherapy and surgery.False-negative findings are caused by lesion vicinity to structures with high glucose metabolism, obscuration of FDG uptake by dental hardware, inadequate PET scanner resolution and inherent low FDG-avidity of some tumours.The interpreting physician must be aware of these unusual patterns of FDG uptake, as well as limitations of PET/CT as a modality, in order to avoid overdiagnosis of benign conditions as malignancy, as well as missing out on actual pathology. • Knowledge of key imaging features of physiological and non-physiological FDG uptake is essential for the interpretation of head and neck PET/CT studies. • Precise anatomical evaluation and correlation with contrast-enhanced CT, US or MRI avoid PET/CT misinterpretation. • Awareness of unusual FDG uptake patterns avoids overdiagnosis of benign conditions as malignancy.

View Article: PubMed Central - PubMed

Affiliation: Department of Imaging, Division of Radiology, Geneva University Hospital, Rue Gabrielle Perret Gentil 4, 1211, Geneva 14, Switzerland.

ABSTRACT

Objectives: Positron emission tomography-computed tomography (PET/CT) with fluorine-18-fluorodeoxy-D-glucose (FDG) has evolved from a research modality to an invaluable tool in head and neck cancer imaging. However, interpretation of FDG PET/CT studies may be difficult due to the inherently complex anatomical landmarks, certain physiological variants and unusual patterns of high FDG uptake in the head and neck. The purpose of this article is to provide a comprehensive approach to key imaging features and interpretation pitfalls of FDG-PET/CT of the head and neck and how to avoid them.

Methods: We review the pathophysiological mechanisms leading to potentially false-positive and false-negative assessments, and we discuss the complementary use of high-resolution contrast-enhanced head and neck PET/CT (HR HN PET/CT) and additional cross-sectional imaging techniques, including ultrasound (US) and magnetic resonance imaging (MRI).

Results: The commonly encountered false-positive PET/CT interpretation pitfalls are due to high FDG uptake by physiological causes, benign thyroid nodules, unilateral cranial nerve palsy and increased FDG uptake due to inflammation, recent chemoradiotherapy and surgery. False-negative findings are caused by lesion vicinity to structures with high glucose metabolism, obscuration of FDG uptake by dental hardware, inadequate PET scanner resolution and inherent low FDG-avidity of some tumours.

Conclusions: The interpreting physician must be aware of these unusual patterns of FDG uptake, as well as limitations of PET/CT as a modality, in order to avoid overdiagnosis of benign conditions as malignancy, as well as missing out on actual pathology.

Teaching points: • Knowledge of key imaging features of physiological and non-physiological FDG uptake is essential for the interpretation of head and neck PET/CT studies. • Precise anatomical evaluation and correlation with contrast-enhanced CT, US or MRI avoid PET/CT misinterpretation. • Awareness of unusual FDG uptake patterns avoids overdiagnosis of benign conditions as malignancy.

No MeSH data available.


Related in: MedlinePlus

Axial (a) and coronal (b) PET/CT images illustrate high FDG uptake of the right submandibular gland (arrows) and soft tissues of the neck (asterisk) in a patient investigated for histiocytosis. The left submandibular gland (arrowhead) shows moderate FDG uptake. Note that the hypermetabolic submandibular gland can be easily mistaken for lymphadenopathy unless coronal images are carefully analysed. Corresponding axial (c) and coronal (d) CECT images reveal slightly increased enhancement of the right submandibular gland (arrows), reticulated aspect of subcutaneous fatty tissue (asterisk) and thickening of the right platysma muscle due to sialadenitis with phlegmon. Dashed arrows in d point at the phlegmon extending cranially in the masticator space. US revealed lithiasis as the cause of sialadenitis
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Fig8: Axial (a) and coronal (b) PET/CT images illustrate high FDG uptake of the right submandibular gland (arrows) and soft tissues of the neck (asterisk) in a patient investigated for histiocytosis. The left submandibular gland (arrowhead) shows moderate FDG uptake. Note that the hypermetabolic submandibular gland can be easily mistaken for lymphadenopathy unless coronal images are carefully analysed. Corresponding axial (c) and coronal (d) CECT images reveal slightly increased enhancement of the right submandibular gland (arrows), reticulated aspect of subcutaneous fatty tissue (asterisk) and thickening of the right platysma muscle due to sialadenitis with phlegmon. Dashed arrows in d point at the phlegmon extending cranially in the masticator space. US revealed lithiasis as the cause of sialadenitis

Mentions: Other than osteomyelitis and reactive nodes, inflammation of salivary gland parenchyma and of salivary ducts can constitute a diagnostic pitfall (Fig. 8). Increased salivary gland uptake can be seen in obstructive as well as non-obstructive sialadenitis. In obstructive sialadenitis, the increased FDG uptake can be explained by the accumulation of excreted FDG in the dilated ductal system. The FDG uptake seen in non-obstructive sialadenitis is caused by activated white blood cells, increased levels of glucose transporters (mainly GLUT 1 and GLUT 3), cytokines and growth factors [10]. Careful correlation of FDG uptake with morphology, as depicted on the CT or CECT part of the PET CT is essential for diagnosis (Fig. 8). CECT findings in sialadenitis include major enhancement of gland parenchyma, reticulated aspect of peri-glandular fatty tissue due to phlegmon and, occasionally, the presence of a small abscess. CECT is less sensitive than US for the detection of early sialadenitis and sialolithiasis. Hypoechoic gland parenchyma, increased vascularisation on Doppler images and blurred gland margins are characteristic findings on US.Fig. 7


FDG-PET/CT pitfalls in oncological head and neck imaging.

Purohit BS, Ailianou A, Dulguerov N, Becker CD, Ratib O, Becker M - Insights Imaging (2014)

Axial (a) and coronal (b) PET/CT images illustrate high FDG uptake of the right submandibular gland (arrows) and soft tissues of the neck (asterisk) in a patient investigated for histiocytosis. The left submandibular gland (arrowhead) shows moderate FDG uptake. Note that the hypermetabolic submandibular gland can be easily mistaken for lymphadenopathy unless coronal images are carefully analysed. Corresponding axial (c) and coronal (d) CECT images reveal slightly increased enhancement of the right submandibular gland (arrows), reticulated aspect of subcutaneous fatty tissue (asterisk) and thickening of the right platysma muscle due to sialadenitis with phlegmon. Dashed arrows in d point at the phlegmon extending cranially in the masticator space. US revealed lithiasis as the cause of sialadenitis
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4195840&req=5

Fig8: Axial (a) and coronal (b) PET/CT images illustrate high FDG uptake of the right submandibular gland (arrows) and soft tissues of the neck (asterisk) in a patient investigated for histiocytosis. The left submandibular gland (arrowhead) shows moderate FDG uptake. Note that the hypermetabolic submandibular gland can be easily mistaken for lymphadenopathy unless coronal images are carefully analysed. Corresponding axial (c) and coronal (d) CECT images reveal slightly increased enhancement of the right submandibular gland (arrows), reticulated aspect of subcutaneous fatty tissue (asterisk) and thickening of the right platysma muscle due to sialadenitis with phlegmon. Dashed arrows in d point at the phlegmon extending cranially in the masticator space. US revealed lithiasis as the cause of sialadenitis
Mentions: Other than osteomyelitis and reactive nodes, inflammation of salivary gland parenchyma and of salivary ducts can constitute a diagnostic pitfall (Fig. 8). Increased salivary gland uptake can be seen in obstructive as well as non-obstructive sialadenitis. In obstructive sialadenitis, the increased FDG uptake can be explained by the accumulation of excreted FDG in the dilated ductal system. The FDG uptake seen in non-obstructive sialadenitis is caused by activated white blood cells, increased levels of glucose transporters (mainly GLUT 1 and GLUT 3), cytokines and growth factors [10]. Careful correlation of FDG uptake with morphology, as depicted on the CT or CECT part of the PET CT is essential for diagnosis (Fig. 8). CECT findings in sialadenitis include major enhancement of gland parenchyma, reticulated aspect of peri-glandular fatty tissue due to phlegmon and, occasionally, the presence of a small abscess. CECT is less sensitive than US for the detection of early sialadenitis and sialolithiasis. Hypoechoic gland parenchyma, increased vascularisation on Doppler images and blurred gland margins are characteristic findings on US.Fig. 7

Bottom Line: The commonly encountered false-positive PET/CT interpretation pitfalls are due to high FDG uptake by physiological causes, benign thyroid nodules, unilateral cranial nerve palsy and increased FDG uptake due to inflammation, recent chemoradiotherapy and surgery.False-negative findings are caused by lesion vicinity to structures with high glucose metabolism, obscuration of FDG uptake by dental hardware, inadequate PET scanner resolution and inherent low FDG-avidity of some tumours.The interpreting physician must be aware of these unusual patterns of FDG uptake, as well as limitations of PET/CT as a modality, in order to avoid overdiagnosis of benign conditions as malignancy, as well as missing out on actual pathology. • Knowledge of key imaging features of physiological and non-physiological FDG uptake is essential for the interpretation of head and neck PET/CT studies. • Precise anatomical evaluation and correlation with contrast-enhanced CT, US or MRI avoid PET/CT misinterpretation. • Awareness of unusual FDG uptake patterns avoids overdiagnosis of benign conditions as malignancy.

View Article: PubMed Central - PubMed

Affiliation: Department of Imaging, Division of Radiology, Geneva University Hospital, Rue Gabrielle Perret Gentil 4, 1211, Geneva 14, Switzerland.

ABSTRACT

Objectives: Positron emission tomography-computed tomography (PET/CT) with fluorine-18-fluorodeoxy-D-glucose (FDG) has evolved from a research modality to an invaluable tool in head and neck cancer imaging. However, interpretation of FDG PET/CT studies may be difficult due to the inherently complex anatomical landmarks, certain physiological variants and unusual patterns of high FDG uptake in the head and neck. The purpose of this article is to provide a comprehensive approach to key imaging features and interpretation pitfalls of FDG-PET/CT of the head and neck and how to avoid them.

Methods: We review the pathophysiological mechanisms leading to potentially false-positive and false-negative assessments, and we discuss the complementary use of high-resolution contrast-enhanced head and neck PET/CT (HR HN PET/CT) and additional cross-sectional imaging techniques, including ultrasound (US) and magnetic resonance imaging (MRI).

Results: The commonly encountered false-positive PET/CT interpretation pitfalls are due to high FDG uptake by physiological causes, benign thyroid nodules, unilateral cranial nerve palsy and increased FDG uptake due to inflammation, recent chemoradiotherapy and surgery. False-negative findings are caused by lesion vicinity to structures with high glucose metabolism, obscuration of FDG uptake by dental hardware, inadequate PET scanner resolution and inherent low FDG-avidity of some tumours.

Conclusions: The interpreting physician must be aware of these unusual patterns of FDG uptake, as well as limitations of PET/CT as a modality, in order to avoid overdiagnosis of benign conditions as malignancy, as well as missing out on actual pathology.

Teaching points: • Knowledge of key imaging features of physiological and non-physiological FDG uptake is essential for the interpretation of head and neck PET/CT studies. • Precise anatomical evaluation and correlation with contrast-enhanced CT, US or MRI avoid PET/CT misinterpretation. • Awareness of unusual FDG uptake patterns avoids overdiagnosis of benign conditions as malignancy.

No MeSH data available.


Related in: MedlinePlus