Limits...
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

HIV positive patient with SCC of the left piriform sinus. a Axial PETCT illustrates a nodular area of high FDG uptake at left level II (asterisk) and bilateral nodular areas of symmetrical high FDG uptake laterally in the neck (arrows). There is an additional nodular area of high FDG uptake in the right retropharyngeal region (arrowhead). All nodular areas of high FDG uptake appear to represent metastatic adenopathy. b Corresponding axial CECT image shows an enlarged enhancing left level II node (asterisk). No suspicious adenopathy is seen at the other sites of increased FDG uptake including the lateral sides of the neck as well as the right retropharyngeal region. c Corresponding coronal PET/CT image confirms the linear nature of the foci of high FDG uptake in both sternocleidomastoid muscles (arrow) and in the right longus colli muscle (arrowheads). Areas of avid nodular FDG uptake are seen at left level II and III (asterisks). d Corresponding coronal CECT image confirms that the linear areas of FDG uptake correspond to neck muscles. Metastatic cervical adenopathy is confirmed at left level II and III (asterisks). The high uptake in the right longus colli and bilateral sternocleidomastoid muscles was related to involuntary contraction in this very anxious patient
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4195840&req=5

Fig5: HIV positive patient with SCC of the left piriform sinus. a Axial PETCT illustrates a nodular area of high FDG uptake at left level II (asterisk) and bilateral nodular areas of symmetrical high FDG uptake laterally in the neck (arrows). There is an additional nodular area of high FDG uptake in the right retropharyngeal region (arrowhead). All nodular areas of high FDG uptake appear to represent metastatic adenopathy. b Corresponding axial CECT image shows an enlarged enhancing left level II node (asterisk). No suspicious adenopathy is seen at the other sites of increased FDG uptake including the lateral sides of the neck as well as the right retropharyngeal region. c Corresponding coronal PET/CT image confirms the linear nature of the foci of high FDG uptake in both sternocleidomastoid muscles (arrow) and in the right longus colli muscle (arrowheads). Areas of avid nodular FDG uptake are seen at left level II and III (asterisks). d Corresponding coronal CECT image confirms that the linear areas of FDG uptake correspond to neck muscles. Metastatic cervical adenopathy is confirmed at left level II and III (asterisks). The high uptake in the right longus colli and bilateral sternocleidomastoid muscles was related to involuntary contraction in this very anxious patient

Mentions: Physiological FDG uptake is often seen in the muscles of the head and neck, which can constitute a diagnostic dilemma in the interpretation of PET scans [2–4, 6–9]. Prominent physiological uptake can be seen in the tongue and in the pterygoid muscles on vocalisation and chewing after FDG injection. Prominent FDG uptake is also often seen in the extraocular muscles due to eye motion. In the neck, physiological FDG uptake can be seen both in the visceral and non-visceral compartment musculature. In the visceral compartment, pronounced uptake in the cricopharyngeus and posterior cricoarytenoid muscles on phonation can interfere with the interpretation of PET scans in patients with hypopharyngeal, oesophageal and thyroid cancers, in whom this physiological uptake may mimic pathology [2, 4, 6, 27]. Uptake in the anterior portion of the genioglossus muscles can mimic or obscure small floor of the mouth cancers. Contraction-induced increased FDG uptake in the cervical muscles, strap muscles and paraspinal muscles in anxious patients (in particular sternocleidomastoid, scalenus anterior, longus colli, longus capitis and inferior obliquus capiti muscles) can mimic lymph node metastasis or, alternatively, may lead to false-negative findings obscuring disease truly present in underlying lymph nodes [2–4, 6–9, 28, 29]. Uptake in the anterior scalenus muscle mimicking supraclavicular lymph node metastasis in a case of lung cancer has been described [29]. Muscle uptake is generally linear and can be traced from the origin to insertion on fused PET/CT images (Fig. 5) Therefore, careful analysis of two-dimensional (2D) multiplanar reconstructions in the coronal and sagittal planes is mandatory whenever findings are unclear on axial PET/CT images [2, 4, 7–9, 28]. The administration of benzodiazepines before FDG injection helps to decrease muscle uptake; however, it is rarely done in clinical routine. Also, patients may be advised to stay relaxed and avoid talking, eating and chewing after the injection of FDG [7–9, 28]. A further factor influencing FDG uptake in muscle is insulin. Insulin administration prior to FDG PET/CT leads to increased accumulation of FDG in muscle, degrading image quality and hampering correct image interpretation [2].


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)

HIV positive patient with SCC of the left piriform sinus. a Axial PETCT illustrates a nodular area of high FDG uptake at left level II (asterisk) and bilateral nodular areas of symmetrical high FDG uptake laterally in the neck (arrows). There is an additional nodular area of high FDG uptake in the right retropharyngeal region (arrowhead). All nodular areas of high FDG uptake appear to represent metastatic adenopathy. b Corresponding axial CECT image shows an enlarged enhancing left level II node (asterisk). No suspicious adenopathy is seen at the other sites of increased FDG uptake including the lateral sides of the neck as well as the right retropharyngeal region. c Corresponding coronal PET/CT image confirms the linear nature of the foci of high FDG uptake in both sternocleidomastoid muscles (arrow) and in the right longus colli muscle (arrowheads). Areas of avid nodular FDG uptake are seen at left level II and III (asterisks). d Corresponding coronal CECT image confirms that the linear areas of FDG uptake correspond to neck muscles. Metastatic cervical adenopathy is confirmed at left level II and III (asterisks). The high uptake in the right longus colli and bilateral sternocleidomastoid muscles was related to involuntary contraction in this very anxious patient
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig5: HIV positive patient with SCC of the left piriform sinus. a Axial PETCT illustrates a nodular area of high FDG uptake at left level II (asterisk) and bilateral nodular areas of symmetrical high FDG uptake laterally in the neck (arrows). There is an additional nodular area of high FDG uptake in the right retropharyngeal region (arrowhead). All nodular areas of high FDG uptake appear to represent metastatic adenopathy. b Corresponding axial CECT image shows an enlarged enhancing left level II node (asterisk). No suspicious adenopathy is seen at the other sites of increased FDG uptake including the lateral sides of the neck as well as the right retropharyngeal region. c Corresponding coronal PET/CT image confirms the linear nature of the foci of high FDG uptake in both sternocleidomastoid muscles (arrow) and in the right longus colli muscle (arrowheads). Areas of avid nodular FDG uptake are seen at left level II and III (asterisks). d Corresponding coronal CECT image confirms that the linear areas of FDG uptake correspond to neck muscles. Metastatic cervical adenopathy is confirmed at left level II and III (asterisks). The high uptake in the right longus colli and bilateral sternocleidomastoid muscles was related to involuntary contraction in this very anxious patient
Mentions: Physiological FDG uptake is often seen in the muscles of the head and neck, which can constitute a diagnostic dilemma in the interpretation of PET scans [2–4, 6–9]. Prominent physiological uptake can be seen in the tongue and in the pterygoid muscles on vocalisation and chewing after FDG injection. Prominent FDG uptake is also often seen in the extraocular muscles due to eye motion. In the neck, physiological FDG uptake can be seen both in the visceral and non-visceral compartment musculature. In the visceral compartment, pronounced uptake in the cricopharyngeus and posterior cricoarytenoid muscles on phonation can interfere with the interpretation of PET scans in patients with hypopharyngeal, oesophageal and thyroid cancers, in whom this physiological uptake may mimic pathology [2, 4, 6, 27]. Uptake in the anterior portion of the genioglossus muscles can mimic or obscure small floor of the mouth cancers. Contraction-induced increased FDG uptake in the cervical muscles, strap muscles and paraspinal muscles in anxious patients (in particular sternocleidomastoid, scalenus anterior, longus colli, longus capitis and inferior obliquus capiti muscles) can mimic lymph node metastasis or, alternatively, may lead to false-negative findings obscuring disease truly present in underlying lymph nodes [2–4, 6–9, 28, 29]. Uptake in the anterior scalenus muscle mimicking supraclavicular lymph node metastasis in a case of lung cancer has been described [29]. Muscle uptake is generally linear and can be traced from the origin to insertion on fused PET/CT images (Fig. 5) Therefore, careful analysis of two-dimensional (2D) multiplanar reconstructions in the coronal and sagittal planes is mandatory whenever findings are unclear on axial PET/CT images [2, 4, 7–9, 28]. The administration of benzodiazepines before FDG injection helps to decrease muscle uptake; however, it is rarely done in clinical routine. Also, patients may be advised to stay relaxed and avoid talking, eating and chewing after the injection of FDG [7–9, 28]. A further factor influencing FDG uptake in muscle is insulin. Insulin administration prior to FDG PET/CT leads to increased accumulation of FDG in muscle, degrading image quality and hampering correct image interpretation [2].

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