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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 Axial PET/CT image demonstrates extensive streak artefacts from right-sided dental implants in a patient with clinically proven SCCof the right retromolar trigone. The known lesion in the right retromolar trigone is completely obscured by the streak artefacts. b Corresponding axial FDG-PET image depicts no uptake in the region of the right retromolar trigone thereby yielding a false-negative result. c Corresponding axial contrast-enhanced T1W MR image detects the infiltrative mass in the right retromolar trigone (white arrows). The extent of the lesion as seen on MRI was afterwards confirmed surgically. MRI is less affected by dental artefacts as compared to CT
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Fig18: a Axial PET/CT image demonstrates extensive streak artefacts from right-sided dental implants in a patient with clinically proven SCCof the right retromolar trigone. The known lesion in the right retromolar trigone is completely obscured by the streak artefacts. b Corresponding axial FDG-PET image depicts no uptake in the region of the right retromolar trigone thereby yielding a false-negative result. c Corresponding axial contrast-enhanced T1W MR image detects the infiltrative mass in the right retromolar trigone (white arrows). The extent of the lesion as seen on MRI was afterwards confirmed surgically. MRI is less affected by dental artefacts as compared to CT

Mentions: Unremovable dental hardware and metallic implants are a major problem in cross-sectional imaging of the head and neck. They can severely degrade the visual appearance of CT and CECT images by causing streak artefacts and affecting the true distribution of Hounsfield units. These artefacts may propagate to the PET images through CT-based attenuation correction factors [2, 71]. Attenuation-correction artefacts may negate the utility of CT for the spatial localisation of PET findings. Because artefacts related to metal implants are in general less pronounced on MRI scans, a combined interpretation of PET/CT and MRI helps to avoid false-negative readings and/or inaccurate tumour assessment (Fig. 18). Artefacts related to dental hardware and metallic implants also affect measurements of SUV values on PET/CT [72]: while SUVs tend to decrease in the dark streak artefact regions, they increase significantly in the bright streak artefact regions [73]. Appropriate algorithms for the correction of metallic artefacts on CT help to overcome this pitfall [72]. These algorithms help to suppress the bright and dark streak artefacts, thereby increasing the HUs in areas where values have been underestimated and decreasing the HUs in areas where values have been overestimated. Inspection of the emission data (non-attenuation-corrected PET scan) often helps to resolve any uncertainty regarding the presence of a CT-based attenuation artefact [2, 6, 74]. Recently, it has been suggested that dental streak artefacts can be corrected during CT-based attenuation correction using complementary MRI data [75].Fig. 15


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 Axial PET/CT image demonstrates extensive streak artefacts from right-sided dental implants in a patient with clinically proven SCCof the right retromolar trigone. The known lesion in the right retromolar trigone is completely obscured by the streak artefacts. b Corresponding axial FDG-PET image depicts no uptake in the region of the right retromolar trigone thereby yielding a false-negative result. c Corresponding axial contrast-enhanced T1W MR image detects the infiltrative mass in the right retromolar trigone (white arrows). The extent of the lesion as seen on MRI was afterwards confirmed surgically. MRI is less affected by dental artefacts as compared to CT
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig18: a Axial PET/CT image demonstrates extensive streak artefacts from right-sided dental implants in a patient with clinically proven SCCof the right retromolar trigone. The known lesion in the right retromolar trigone is completely obscured by the streak artefacts. b Corresponding axial FDG-PET image depicts no uptake in the region of the right retromolar trigone thereby yielding a false-negative result. c Corresponding axial contrast-enhanced T1W MR image detects the infiltrative mass in the right retromolar trigone (white arrows). The extent of the lesion as seen on MRI was afterwards confirmed surgically. MRI is less affected by dental artefacts as compared to CT
Mentions: Unremovable dental hardware and metallic implants are a major problem in cross-sectional imaging of the head and neck. They can severely degrade the visual appearance of CT and CECT images by causing streak artefacts and affecting the true distribution of Hounsfield units. These artefacts may propagate to the PET images through CT-based attenuation correction factors [2, 71]. Attenuation-correction artefacts may negate the utility of CT for the spatial localisation of PET findings. Because artefacts related to metal implants are in general less pronounced on MRI scans, a combined interpretation of PET/CT and MRI helps to avoid false-negative readings and/or inaccurate tumour assessment (Fig. 18). Artefacts related to dental hardware and metallic implants also affect measurements of SUV values on PET/CT [72]: while SUVs tend to decrease in the dark streak artefact regions, they increase significantly in the bright streak artefact regions [73]. Appropriate algorithms for the correction of metallic artefacts on CT help to overcome this pitfall [72]. These algorithms help to suppress the bright and dark streak artefacts, thereby increasing the HUs in areas where values have been underestimated and decreasing the HUs in areas where values have been overestimated. Inspection of the emission data (non-attenuation-corrected PET scan) often helps to resolve any uncertainty regarding the presence of a CT-based attenuation artefact [2, 6, 74]. Recently, it has been suggested that dental streak artefacts can be corrected during CT-based attenuation correction using complementary MRI data [75].Fig. 15

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