DOI: 10.1148/rg.254035156
Combined PET-CT in the Head and Neck
Part 1. Physiologic, Altered Physiologic, and Artifactual FDG Uptake1
Todd M. Blodgett, MD,
Melanie B. Fukui, MD,
Carl H. Snyderman, MD,
Barton F. Branstetter, IV, MD,
Barry M. McCook, MD,
Dave W. Townsend, PhD and
Carolyn C. Meltzer, MD
1 From the Departments of Radiology (T.M.B., B.F.B., B.M.M., D.W.T., C.C.M.), Otolaryngology (C.H.S., B.F.B.), Psychiatry (C.C.M.), and Neurology (C.C.M.), University of Pittsburgh, 200 Lothrop St, Pittsburgh, PA 15213; and the Department of Radiology, Allegheny General Hospital, Pittsburgh, Pa (M.B.F.). Presented as an education exhibit at the 2001 RSNA Annual Meeting. Received June 26, 2003; revision requested October 22; final revision received October 25, 2004; accepted November 3. T.M.B. is a consultant for Petnet Pharmaceuticals; D.W.T. is a consultant for CPS Innovations; all remaining authors have no financial relationships to disclose.
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Figure 1a. Hypermetabolic thyroid adenoma. Axial CT (a) and fused PET-CT (b) scans show focal intense FDG uptake (arrow) that is localized to the left lobe of the thyroid gland. Subsequent biopsy helped confirm thyroid adenoma.
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Figure 1b. Hypermetabolic thyroid adenoma. Axial CT (a) and fused PET-CT (b) scans show focal intense FDG uptake (arrow) that is localized to the left lobe of the thyroid gland. Subsequent biopsy helped confirm thyroid adenoma.
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Figure 2a. Hürthle cell carcinoma. Axial CT (a) and fused PET-CT (b) scans help localize a focal abnormality (arrow) to a 2.5-cm cystic thyroid mass. Biopsy of the mass helped confirm a Hürthle cell carcinoma of the thyroid gland.
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Figure 2b. Hürthle cell carcinoma. Axial CT (a) and fused PET-CT (b) scans help localize a focal abnormality (arrow) to a 2.5-cm cystic thyroid mass. Biopsy of the mass helped confirm a Hürthle cell carcinoma of the thyroid gland.
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Figure 3a. Physiologic thyroid uptake. (a) Coronal PET scan shows diffuse symmetric FDG uptake localized to the thyroid gland (arrow). (b) Axial fused PET-CT scan helps confirm localization of the uptake to the thyroid gland (arrow).
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Figure 3b. Physiologic thyroid uptake. (a) Coronal PET scan shows diffuse symmetric FDG uptake localized to the thyroid gland (arrow). (b) Axial fused PET-CT scan helps confirm localization of the uptake to the thyroid gland (arrow).
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Figure 4a. Physiologic parotid uptake. Axial CT (a) and fused PET-CT (b) scans show moderate symmetric FDG uptake in the parotid glands (arrow).
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Figure 4b. Physiologic parotid uptake. Axial CT (a) and fused PET-CT (b) scans show moderate symmetric FDG uptake in the parotid glands (arrow).
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Figure 5a. Physiologic submandibular uptake. Axial CT (a) and fused PET-CT (b) scans demonstrate symmetric FDG uptake that is localized to the submandibular glands (arrow).
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Figure 5b. Physiologic submandibular uptake. Axial CT (a) and fused PET-CT (b) scans demonstrate symmetric FDG uptake that is localized to the submandibular glands (arrow).
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Figure 6a. Physiologic muscle uptake. (a) Coronal PET scan demonstrates multiple bilateral foci of intense FDG uptake (arrows). Note also the primary right lung cancer (arrowhead). (b) Axial CT scan of the lower neck shows foci of intense FDG uptake in the shoulder girdle (arrows). (c) Fused PET-CT scan helps localize the foci of FDG uptake to muscles and fat in the shoulder girdle (arrows).
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Figure 6b. Physiologic muscle uptake. (a) Coronal PET scan demonstrates multiple bilateral foci of intense FDG uptake (arrows). Note also the primary right lung cancer (arrowhead). (b) Axial CT scan of the lower neck shows foci of intense FDG uptake in the shoulder girdle (arrows). (c) Fused PET-CT scan helps localize the foci of FDG uptake to muscles and fat in the shoulder girdle (arrows).
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Figure 6c. Physiologic muscle uptake. (a) Coronal PET scan demonstrates multiple bilateral foci of intense FDG uptake (arrows). Note also the primary right lung cancer (arrowhead). (b) Axial CT scan of the lower neck shows foci of intense FDG uptake in the shoulder girdle (arrows). (c) Fused PET-CT scan helps localize the foci of FDG uptake to muscles and fat in the shoulder girdle (arrows).
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Figure 7a. Asymmetric sternocleidomastoid muscle uptake. Coronal PET demonstrated asymmetric FDG uptake in the right side of the neck. (a) Axial CT scan shows focal FDG uptake in the right sternocleidomastoid muscle (arrow). (b) Corresponding fused PET-CT scan helps accurately localize the FDG uptake to the right sternocleidomastoid muscle (arrow). Note also the symmetric FDG uptake within the prevertebral muscles (arrowheads).
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Figure 7b. Asymmetric sternocleidomastoid muscle uptake. Coronal PET demonstrated asymmetric FDG uptake in the right side of the neck. (a) Axial CT scan shows focal FDG uptake in the right sternocleidomastoid muscle (arrow). (b) Corresponding fused PET-CT scan helps accurately localize the FDG uptake to the right sternocleidomastoid muscle (arrow). Note also the symmetric FDG uptake within the prevertebral muscles (arrowheads).
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Figure 8a. Asymmetric uptake in the inferior obliquus capitus muscle. (a) Coronal PET scan shows a hypermetabolic focus in the left side of the neck (arrow). (b) Axial CT scan reveals no correlative abnormality. Arrow indicates the left inferior obliquus capitus muscle. (c) Axial fused PET-CT scan helps confirm prominent asymmetric physiologic FDG uptake in the left inferior obliquus capitus muscle (arrow).
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Figure 8b. Asymmetric uptake in the inferior obliquus capitus muscle. (a) Coronal PET scan shows a hypermetabolic focus in the left side of the neck (arrow). (b) Axial CT scan reveals no correlative abnormality. Arrow indicates the left inferior obliquus capitus muscle. (c) Axial fused PET-CT scan helps confirm prominent asymmetric physiologic FDG uptake in the left inferior obliquus capitus muscle (arrow).
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Figure 8c. Asymmetric uptake in the inferior obliquus capitus muscle. (a) Coronal PET scan shows a hypermetabolic focus in the left side of the neck (arrow). (b) Axial CT scan reveals no correlative abnormality. Arrow indicates the left inferior obliquus capitus muscle. (c) Axial fused PET-CT scan helps confirm prominent asymmetric physiologic FDG uptake in the left inferior obliquus capitus muscle (arrow).
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Figure 9. Physiologic facial muscle uptake. Axial fused PET-CT scan helps localize linear FDG uptake to the muscles of facial expression in the lower part of the face (arrow), a finding that is consistent with physiologic FDG uptake.
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Figure 10a. Physiologic effect of insulin on FDG muscle uptake. Axial CT (a) and fused PET-CT (b) scans show prominent linear FDG uptake within the muscles of the neck and upper back (arrows). The patient had received insulin prior to the injection of FDG.
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Figure 10b. Physiologic effect of insulin on FDG muscle uptake. Axial CT (a) and fused PET-CT (b) scans show prominent linear FDG uptake within the muscles of the neck and upper back (arrows). The patient had received insulin prior to the injection of FDG.
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Figure 11. Physiologic lateral pterygoid muscle uptake. Coronal PET demonstrated bilateral foci of intense physiologic FDG uptake in the infratemporal fossa and adenoids. CT findings were normal. Axial fused PET-CT scan helps localize foci of uptake to the superior portion of the lateral pterygoid muscles (arrow).
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Figure 12. Symmetric physiologic mylohyoid muscle uptake. Axial fused PET-CT scan helps accurately localize FDG uptake to the mylohyoid line (the insertion site of the mylohyoid muscle) (arrow).
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Figure 13. Asymmetric mylohyoid muscle uptake. Coronal fused PET-CT scan demonstrates precise localization of FDG to the right mylohyoid muscle (arrow).
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Figure 14a. Asymmetric uptake in the right medial pterygoid muscle. (a) Coronal PET scan shows a large, asymmetric hypermetabolic focus in the right infratemporal fossa (arrow). (b) Axial CT scan demonstrates no abnormality. Arrow indicates the right medial pterygoid muscle. (c) Axial fused PET-CT scan helps accurately localize uptake to the right medial pterygoid muscle (arrow), a finding that is consistent with asymmetric physiologic muscle uptake.
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Figure 14b. Asymmetric uptake in the right medial pterygoid muscle. (a) Coronal PET scan shows a large, asymmetric hypermetabolic focus in the right infratemporal fossa (arrow). (b) Axial CT scan demonstrates no abnormality. Arrow indicates the right medial pterygoid muscle. (c) Axial fused PET-CT scan helps accurately localize uptake to the right medial pterygoid muscle (arrow), a finding that is consistent with asymmetric physiologic muscle uptake.
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Figure 14c. Asymmetric uptake in the right medial pterygoid muscle. (a) Coronal PET scan shows a large, asymmetric hypermetabolic focus in the right infratemporal fossa (arrow). (b) Axial CT scan demonstrates no abnormality. Arrow indicates the right medial pterygoid muscle. (c) Axial fused PET-CT scan helps accurately localize uptake to the right medial pterygoid muscle (arrow), a finding that is consistent with asymmetric physiologic muscle uptake.
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Figure 15. Lingual uptake. Axial fused PET-CT scan demonstrates physiologic lingual FDG uptake (arrow).
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Figure 16. Palatal mucosal uptake. Axial fused PET-CT scan shows intense FDG uptake in the superior oropharynx (arrow). FDG uptake within the mucosa of the soft palate is often indistinguishable from the slightly more inferior lingual uptake (cf Fig 15).
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Figure 17a. Physiologic vocal cord uptake. Axial CT (a) and fused PET-CT (b) scans help identify FDG uptake in the neck as symmetric physiologic activity in the true vocal cords (arrow). The patient was talking during the uptake phase.
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Figure 17b. Physiologic vocal cord uptake. Axial CT (a) and fused PET-CT (b) scans help identify FDG uptake in the neck as symmetric physiologic activity in the true vocal cords (arrow). The patient was talking during the uptake phase.
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Figure 18a. Physiologic cricopharyngeus muscle uptake. (a) Coronal PET scan demonstrates a hypermetabolic focus (arrow). (b) Axial fused PET-CT scan helps localize the area of uptake precisely to the cricopharyngeus muscle (arrow).
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Figure 18b. Physiologic cricopharyngeus muscle uptake. (a) Coronal PET scan demonstrates a hypermetabolic focus (arrow). (b) Axial fused PET-CT scan helps localize the area of uptake precisely to the cricopharyngeus muscle (arrow).
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Figure 19. Pharyngeal constrictor muscle uptake. Axial fused PET-CT scan demonstrates physiologic FDG uptake within the pharyngeal constrictor muscles (arrow). The patient was coughing during the uptake phase.
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Figure 20a. Physiologic brown fat uptake. (a) Coronal PET scan shows bilateral foci of intense FDG uptake in the posterior superior thorax (arrow). (b) Axial CT scan shows no correlative abnormality. Arrow indicates an area of fat attenuation. (c) Axial fused PET-CT scan helps localize the foci precisely to areas of fat attenuation seen at CT (arrow).
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Figure 20b. Physiologic brown fat uptake. (a) Coronal PET scan shows bilateral foci of intense FDG uptake in the posterior superior thorax (arrow). (b) Axial CT scan shows no correlative abnormality. Arrow indicates an area of fat attenuation. (c) Axial fused PET-CT scan helps localize the foci precisely to areas of fat attenuation seen at CT (arrow).
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Figure 20c. Physiologic brown fat uptake. (a) Coronal PET scan shows bilateral foci of intense FDG uptake in the posterior superior thorax (arrow). (b) Axial CT scan shows no correlative abnormality. Arrow indicates an area of fat attenuation. (c) Axial fused PET-CT scan helps localize the foci precisely to areas of fat attenuation seen at CT (arrow).
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Figure 21a. Asymmetric superphysiologic uptake in a vocal cord following paralysis of the contralateral cord caused during thyroid surgery. (a) Axial fused PET-CT scan helps localize asymmetric FDG uptake to the right true vocal cord (arrow), a finding that simulates a laryngeal neoplasm. (b) Laryngoscopic image helps confirm superphysiologic metabolic activity in the normal vocal cord (arrow) and paralysis of the contralateral cord. (Figure 21 reprinted, with permission, from reference 33.)
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Figure 21b. Asymmetric superphysiologic uptake in a vocal cord following paralysis of the contralateral cord caused during thyroid surgery. (a) Axial fused PET-CT scan helps localize asymmetric FDG uptake to the right true vocal cord (arrow), a finding that simulates a laryngeal neoplasm. (b) Laryngoscopic image helps confirm superphysiologic metabolic activity in the normal vocal cord (arrow) and paralysis of the contralateral cord. (Figure 21 reprinted, with permission, from reference 33.)
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Figure 22. Physiologic adenoid uptake. Axial fused PET-CT scan helps localize intense bilateral nasopharyngeal FDG uptake to the adenoids (arrow).
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Figure 23. Physiologic palatine tonsil uptake. Axial fused PET-CT scan shows intense symmetric physiologic FDG uptake within the palatine tonsils (arrow). This finding can also be seen in tonsillar hyperplasia.
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Figure 24. Squamous cell carcinoma of the nasopharynx in a patient with squamous cell metastases to the neck and no known primary malignancy. Axial fused PET-CT scan shows asymmetric FDG uptake in the left side of the nasopharynx (arrow). Subsequent biopsy helped confirm the diagnosis.
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Figure 25a. Lymphangiographic effect in a patient with known infiltration of FDG into the left antecubital vein. (a) Coronal PET scan shows accumulation of FDG within the axillary and left paratracheal lymph nodes (arrow). (b) Axial fused PET-CT scan of the left arm shows indistinct areas of FDG accumulation within the lymphatic channels (arrow). Repeat fused PET-CT performed a few weeks later showed no evidence of nodal uptake.
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Figure 25b. Lymphangiographic effect in a patient with known infiltration of FDG into the left antecubital vein. (a) Coronal PET scan shows accumulation of FDG within the axillary and left paratracheal lymph nodes (arrow). (b) Axial fused PET-CT scan of the left arm shows indistinct areas of FDG accumulation within the lymphatic channels (arrow). Repeat fused PET-CT performed a few weeks later showed no evidence of nodal uptake.
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Figure 26a. CT attenuation artifact from an implantable catheter port. (a) Coronal PET scan demonstrates focal intense FDG accumulation in the right supraclavicular area (arrow). (b) Axial fused PET-CT scan helps localize the FDG activity to an implanted catheter port (arrow). (c) Axial uncorrected emission image helps confirm that the abnormality (arrowhead) is an attenuation correction artifact caused by the extremely high attenuation of the port.
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Figure 26b. CT attenuation artifact from an implantable catheter port. (a) Coronal PET scan demonstrates focal intense FDG accumulation in the right supraclavicular area (arrow). (b) Axial fused PET-CT scan helps localize the FDG activity to an implanted catheter port (arrow). (c) Axial uncorrected emission image helps confirm that the abnormality (arrowhead) is an attenuation correction artifact caused by the extremely high attenuation of the port.
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Figure 26c. CT attenuation artifact from an implantable catheter port. (a) Coronal PET scan demonstrates focal intense FDG accumulation in the right supraclavicular area (arrow). (b) Axial fused PET-CT scan helps localize the FDG activity to an implanted catheter port (arrow). (c) Axial uncorrected emission image helps confirm that the abnormality (arrowhead) is an attenuation correction artifact caused by the extremely high attenuation of the port.
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Figure 27a. Linear CT attenuation artifact due to high-attenuation intravenous contrast material. (a) Coronal PET scan shows a focal area of intense FDG accumulation located in the left axilla (arrow) and mimicking an abnormal axillary lymph node. (b) Axial fused PET-CT scan helps localize the uptake to an area of dense contrast material in the left subclavian vein (arrow). (c) Axial uncorrected emission image reveals that the area of apparent FDG uptake in the axilla (arrow) is an artifact generated during the attenuation correction process. (Figure 27 reprinted, with permission, from reference 37.)
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Figure 27b. Linear CT attenuation artifact due to high-attenuation intravenous contrast material. (a) Coronal PET scan shows a focal area of intense FDG accumulation located in the left axilla (arrow) and mimicking an abnormal axillary lymph node. (b) Axial fused PET-CT scan helps localize the uptake to an area of dense contrast material in the left subclavian vein (arrow). (c) Axial uncorrected emission image reveals that the area of apparent FDG uptake in the axilla (arrow) is an artifact generated during the attenuation correction process. (Figure 27 reprinted, with permission, from reference 37.)
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Figure 27c. Linear CT attenuation artifact due to high-attenuation intravenous contrast material. (a) Coronal PET scan shows a focal area of intense FDG accumulation located in the left axilla (arrow) and mimicking an abnormal axillary lymph node. (b) Axial fused PET-CT scan helps localize the uptake to an area of dense contrast material in the left subclavian vein (arrow). (c) Axial uncorrected emission image reveals that the area of apparent FDG uptake in the axilla (arrow) is an artifact generated during the attenuation correction process. (Figure 27 reprinted, with permission, from reference 37.)
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Figure 28a. Focal CT attenuation artifact due to high-attenuation intravenous contrast material. (a) Coronal PET scan shows symmetric FDG uptake in the thyroid gland and a focal area of intense uptake in the right supraclavicular region (arrow) mimicking an abnormal lymph node. (b) Axial fused PET-CT scan helps localize the apparent FDG activity precisely to the brachiocephalic vein (arrow). (c) On an axial uncorrected emission image, no apparent FDG activity is seen (arrow), indicating that the area of uptake seen at fused PET-CT represents an artifact of CT-based attenuation correction.
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Figure 28b. Focal CT attenuation artifact due to high-attenuation intravenous contrast material. (a) Coronal PET scan shows symmetric FDG uptake in the thyroid gland and a focal area of intense uptake in the right supraclavicular region (arrow) mimicking an abnormal lymph node. (b) Axial fused PET-CT scan helps localize the apparent FDG activity precisely to the brachiocephalic vein (arrow). (c) On an axial uncorrected emission image, no apparent FDG activity is seen (arrow), indicating that the area of uptake seen at fused PET-CT represents an artifact of CT-based attenuation correction.
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Figure 28c. Focal CT attenuation artifact due to high-attenuation intravenous contrast material. (a) Coronal PET scan shows symmetric FDG uptake in the thyroid gland and a focal area of intense uptake in the right supraclavicular region (arrow) mimicking an abnormal lymph node. (b) Axial fused PET-CT scan helps localize the apparent FDG activity precisely to the brachiocephalic vein (arrow). (c) On an axial uncorrected emission image, no apparent FDG activity is seen (arrow), indicating that the area of uptake seen at fused PET-CT represents an artifact of CT-based attenuation correction.
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Figure 29a. Abnormal lymph node adjacent to high-attenuation intravenous contrast material. (a) Coronal PET scan shows a small focal abnormality in the supraclavicular region (arrow). (b, c) Axial CT (b) and fused PET-CT (c) scans help localize the abnormality to the right brachiocephalic vein (cf Fig 28). In this case, however, uncorrected emission PET still showed the abnormality, indicating that the abnormality did not represent an attenuation correction artifact, but rather a small node adjacent to the brachiocephalic vein.
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Figure 29b. Abnormal lymph node adjacent to high-attenuation intravenous contrast material. (a) Coronal PET scan shows a small focal abnormality in the supraclavicular region (arrow). (b, c) Axial CT (b) and fused PET-CT (c) scans help localize the abnormality to the right brachiocephalic vein (cf Fig 28). In this case, however, uncorrected emission PET still showed the abnormality, indicating that the abnormality did not represent an attenuation correction artifact, but rather a small node adjacent to the brachiocephalic vein.
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Figure 29c. Abnormal lymph node adjacent to high-attenuation intravenous contrast material. (a) Coronal PET scan shows a small focal abnormality in the supraclavicular region (arrow). (b, c) Axial CT (b) and fused PET-CT (c) scans help localize the abnormality to the right brachiocephalic vein (cf Fig 28). In this case, however, uncorrected emission PET still showed the abnormality, indicating that the abnormality did not represent an attenuation correction artifact, but rather a small node adjacent to the brachiocephalic vein.
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Copyright © 2005 by the Radiological Society of North America.
