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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

a Coronal PET/CT image illustrates a focal nodular area of high FDG uptake within the left thyroid lobe (white arrow), which can reveal an underlying malignancy in 25–50 % of cases. Therefore, US FNAC is recommended. b Corresponding coronal CECT image shows a small hypodense nodule within the left thyroid lobe (white arrow), corresponding to the focus of high FDG uptake on PET/CT. Subsequent US FNAC of the left thyroid nodule and follow-up over a period of 2 years yielded benign thyroid nodule, thereby indicating that the PET/CT result was false-positive for malignancy
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Fig13: a Coronal PET/CT image illustrates a focal nodular area of high FDG uptake within the left thyroid lobe (white arrow), which can reveal an underlying malignancy in 25–50 % of cases. Therefore, US FNAC is recommended. b Corresponding coronal CECT image shows a small hypodense nodule within the left thyroid lobe (white arrow), corresponding to the focus of high FDG uptake on PET/CT. Subsequent US FNAC of the left thyroid nodule and follow-up over a period of 2 years yielded benign thyroid nodule, thereby indicating that the PET/CT result was false-positive for malignancy

Mentions: The thyroid gland may show various appearances on PET studies with diffuse symmetrical FDG uptake, focal asymmetrical uptake or at times, no uptake [2, 6–8, 62, 63]. Various physiological, benign and pathological processes may be causative for these different patterns of FDG uptake. Mild diffuse symmetrical uptake may be seen in normal thyroid glands, in diffuse goitres or in autoimmune thyroiditis, whereas focal uptake may be seen in adenomatous nodules and thyroid malignancy [2, 6–8, 62, 63]. Although some authors state that the maximum SUV of malignant thyroid lesions is significantly higher than that of benign lesions (6.7 ± 5.5 vs 10.7 ± 7.8; P < 0.05) [63], the reported risk of malignancy in an area of focal FDG uptake in the thyroid ranges from 36–63 % [62, 63]. Therefore, all focal areas of moderate to intense FDG uptake in the thyroid gland should be further assessed with an US examination and US FNAC to exclude thyroid cancer (Fig. 13). Another potential imaging pitfall is the likely misdiagnosis of focal thyroid uptake as metastatic disease in the lower cervical nodal stations [64]. Precise image fusion helps to resolve this diagnostic dilemma [64]. However, in patients who have moved between the CT scan and the PET acquisition, it may be difficult to differentiate between metastatic level IV lymph nodes and small thyroid nodules, in particular in small-sized lesions. In our institution, we routinely perform an US examination of the neck in these situations and, if necessary, US FNAC.Fig. 11


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)

a Coronal PET/CT image illustrates a focal nodular area of high FDG uptake within the left thyroid lobe (white arrow), which can reveal an underlying malignancy in 25–50 % of cases. Therefore, US FNAC is recommended. b Corresponding coronal CECT image shows a small hypodense nodule within the left thyroid lobe (white arrow), corresponding to the focus of high FDG uptake on PET/CT. Subsequent US FNAC of the left thyroid nodule and follow-up over a period of 2 years yielded benign thyroid nodule, thereby indicating that the PET/CT result was false-positive for malignancy
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4195840&req=5

Fig13: a Coronal PET/CT image illustrates a focal nodular area of high FDG uptake within the left thyroid lobe (white arrow), which can reveal an underlying malignancy in 25–50 % of cases. Therefore, US FNAC is recommended. b Corresponding coronal CECT image shows a small hypodense nodule within the left thyroid lobe (white arrow), corresponding to the focus of high FDG uptake on PET/CT. Subsequent US FNAC of the left thyroid nodule and follow-up over a period of 2 years yielded benign thyroid nodule, thereby indicating that the PET/CT result was false-positive for malignancy
Mentions: The thyroid gland may show various appearances on PET studies with diffuse symmetrical FDG uptake, focal asymmetrical uptake or at times, no uptake [2, 6–8, 62, 63]. Various physiological, benign and pathological processes may be causative for these different patterns of FDG uptake. Mild diffuse symmetrical uptake may be seen in normal thyroid glands, in diffuse goitres or in autoimmune thyroiditis, whereas focal uptake may be seen in adenomatous nodules and thyroid malignancy [2, 6–8, 62, 63]. Although some authors state that the maximum SUV of malignant thyroid lesions is significantly higher than that of benign lesions (6.7 ± 5.5 vs 10.7 ± 7.8; P < 0.05) [63], the reported risk of malignancy in an area of focal FDG uptake in the thyroid ranges from 36–63 % [62, 63]. Therefore, all focal areas of moderate to intense FDG uptake in the thyroid gland should be further assessed with an US examination and US FNAC to exclude thyroid cancer (Fig. 13). Another potential imaging pitfall is the likely misdiagnosis of focal thyroid uptake as metastatic disease in the lower cervical nodal stations [64]. Precise image fusion helps to resolve this diagnostic dilemma [64]. However, in patients who have moved between the CT scan and the PET acquisition, it may be difficult to differentiate between metastatic level IV lymph nodes and small thyroid nodules, in particular in small-sized lesions. In our institution, we routinely perform an US examination of the neck in these situations and, if necessary, US FNAC.Fig. 11

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