DOI: 10.1148/rg.245035725
PET-CT Fusion Imaging in Differentiating Physiologic from Pathologic FDG Uptake1
Lale Kostakoglu, MD,
Ruth Hardoff, MD,
Rosna Mirtcheva, MD and
Stanley J. Goldsmith, MD
1 From the Division of Nuclear Medicine, Department of Radiology, New York Presbyterian Hospital, Weill Medical College of Cornell University, 525 E 68th St, Starr No 221, New York, NY 10021 (L.K., R.M., S.J.G.); and the Department of Nuclear Medicine, Rabin Medical Center, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel (R.H.). Received October 6, 2003; revision requested November 25 and received January 24, 2004; accepted January 30. All authors have no financial relationships to disclose. Address correspondence to L.K. (e-mail: lak2005@med.cornell.edu).
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Figure 1a. Normal distribution of FDG. Coronal CT (a), PET (b), and PET-CT fusion (c) images demonstrate the physiologic accumulation of FDG in the cerebral-cerebellar cortex at the base of the skull and in the myocardium, liver, kidneys, renal pelvis, bone marrow, and urinary bladder. Note also the minimal uptake in the mediastinum and bilaterally in the lower cervical and psoas muscles.
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Figure 1b. Normal distribution of FDG. Coronal CT (a), PET (b), and PET-CT fusion (c) images demonstrate the physiologic accumulation of FDG in the cerebral-cerebellar cortex at the base of the skull and in the myocardium, liver, kidneys, renal pelvis, bone marrow, and urinary bladder. Note also the minimal uptake in the mediastinum and bilaterally in the lower cervical and psoas muscles.
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Figure 1c. Normal distribution of FDG. Coronal CT (a), PET (b), and PET-CT fusion (c) images demonstrate the physiologic accumulation of FDG in the cerebral-cerebellar cortex at the base of the skull and in the myocardium, liver, kidneys, renal pelvis, bone marrow, and urinary bladder. Note also the minimal uptake in the mediastinum and bilaterally in the lower cervical and psoas muscles.
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Figure 2a. Contraction-induced FDG uptake in a 50-year-old woman with advanced non-small cell lung cancer who was referred for presurgical evaluation. (a) Axial FDG PET scans demonstrate multiple hypermetabolic foci in the anterior cervical region. Intense symmetric and superficial uptake in the anterior neck (arrowheads) suggests tense sternocleidomastoid muscle uptake. An additional asymmetric focus of uptake posterior to the right sternocleidomastoid muscle (arrows) suggests cervical lymph node metastasis, which represents a more advanced disease stage and renders the patient ineligible for surgery until after neoadjuvant chemotherapy. (b, c) Axial CT (b) and PET-CT fusion (c) images demonstrate that the unilateral uptake in the right cervical region corresponds to the anterior scalene muscle (long arrow) and that the superficially located symmetric FDG uptake corresponds to the sternocleidomastoid muscles (short arrows). Evaluation with PET-CT excluded the possibility of a false-positive finding (ie, metastatic disease in the neck), which would subject the patient to unnecessary chemotherapy.
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Figure 2b. Contraction-induced FDG uptake in a 50-year-old woman with advanced non-small cell lung cancer who was referred for presurgical evaluation. (a) Axial FDG PET scans demonstrate multiple hypermetabolic foci in the anterior cervical region. Intense symmetric and superficial uptake in the anterior neck (arrowheads) suggests tense sternocleidomastoid muscle uptake. An additional asymmetric focus of uptake posterior to the right sternocleidomastoid muscle (arrows) suggests cervical lymph node metastasis, which represents a more advanced disease stage and renders the patient ineligible for surgery until after neoadjuvant chemotherapy. (b, c) Axial CT (b) and PET-CT fusion (c) images demonstrate that the unilateral uptake in the right cervical region corresponds to the anterior scalene muscle (long arrow) and that the superficially located symmetric FDG uptake corresponds to the sternocleidomastoid muscles (short arrows). Evaluation with PET-CT excluded the possibility of a false-positive finding (ie, metastatic disease in the neck), which would subject the patient to unnecessary chemotherapy.
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Figure 2c. Contraction-induced FDG uptake in a 50-year-old woman with advanced non-small cell lung cancer who was referred for presurgical evaluation. (a) Axial FDG PET scans demonstrate multiple hypermetabolic foci in the anterior cervical region. Intense symmetric and superficial uptake in the anterior neck (arrowheads) suggests tense sternocleidomastoid muscle uptake. An additional asymmetric focus of uptake posterior to the right sternocleidomastoid muscle (arrows) suggests cervical lymph node metastasis, which represents a more advanced disease stage and renders the patient ineligible for surgery until after neoadjuvant chemotherapy. (b, c) Axial CT (b) and PET-CT fusion (c) images demonstrate that the unilateral uptake in the right cervical region corresponds to the anterior scalene muscle (long arrow) and that the superficially located symmetric FDG uptake corresponds to the sternocleidomastoid muscles (short arrows). Evaluation with PET-CT excluded the possibility of a false-positive finding (ie, metastatic disease in the neck), which would subject the patient to unnecessary chemotherapy.
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Figure 3a. Asymmetric muscle uptake in a 62-year-old woman with squamous cell carcinoma of the tongue who had undergone neck dissection. (a) Axial FDG PET scans demonstrate multiple hypermetabolic foci in the right anterolateral cervical region. Asymmetric and superficial uptake in the right anterior portion of the neck (arrowheads) suggests tense sternocleidomastoid muscle uptake. An additional asymmetric focus of uptake is noted posterior to the right sternocleidomastoid muscle (long arrow) and suggests cervical lymph node metastasis, although unilateral cervical muscle uptake cannot be excluded (cf Fig 4). Symmetric foci seen within the larynx (short arrows) probably represent the intrinsic laryngeal muscles. (b, c) Axial CT (b) and PET-CT fusion (c) images help confirm that the superficial asymmetric FDG uptake in the anterior cervical region corresponds to the right sternocleidomastoid muscle (arrowhead). The absence of contralateral muscle uptake is due to prior neck dissection. The unilateral focus of uptake posterior to the right sternocleidomastoid muscle (long arrow) corresponds to a cervical lymph node, and symmetric foci within the larynx (short arrows) correspond to the intrinsic laryngeal muscles and cricoarytenoid muscles posteriorly. The results of simultaneous evaluation with PET and CT confirmed the diagnosis of (advanced) metastatic disease in the neck and had a significant impact on clinical management. The patient was started on therapy on the basis of the PET-CT findings.
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Figure 3b. Asymmetric muscle uptake in a 62-year-old woman with squamous cell carcinoma of the tongue who had undergone neck dissection. (a) Axial FDG PET scans demonstrate multiple hypermetabolic foci in the right anterolateral cervical region. Asymmetric and superficial uptake in the right anterior portion of the neck (arrowheads) suggests tense sternocleidomastoid muscle uptake. An additional asymmetric focus of uptake is noted posterior to the right sternocleidomastoid muscle (long arrow) and suggests cervical lymph node metastasis, although unilateral cervical muscle uptake cannot be excluded (cf Fig 4). Symmetric foci seen within the larynx (short arrows) probably represent the intrinsic laryngeal muscles. (b, c) Axial CT (b) and PET-CT fusion (c) images help confirm that the superficial asymmetric FDG uptake in the anterior cervical region corresponds to the right sternocleidomastoid muscle (arrowhead). The absence of contralateral muscle uptake is due to prior neck dissection. The unilateral focus of uptake posterior to the right sternocleidomastoid muscle (long arrow) corresponds to a cervical lymph node, and symmetric foci within the larynx (short arrows) correspond to the intrinsic laryngeal muscles and cricoarytenoid muscles posteriorly. The results of simultaneous evaluation with PET and CT confirmed the diagnosis of (advanced) metastatic disease in the neck and had a significant impact on clinical management. The patient was started on therapy on the basis of the PET-CT findings.
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Figure 3c. Asymmetric muscle uptake in a 62-year-old woman with squamous cell carcinoma of the tongue who had undergone neck dissection. (a) Axial FDG PET scans demonstrate multiple hypermetabolic foci in the right anterolateral cervical region. Asymmetric and superficial uptake in the right anterior portion of the neck (arrowheads) suggests tense sternocleidomastoid muscle uptake. An additional asymmetric focus of uptake is noted posterior to the right sternocleidomastoid muscle (long arrow) and suggests cervical lymph node metastasis, although unilateral cervical muscle uptake cannot be excluded (cf Fig 4). Symmetric foci seen within the larynx (short arrows) probably represent the intrinsic laryngeal muscles. (b, c) Axial CT (b) and PET-CT fusion (c) images help confirm that the superficial asymmetric FDG uptake in the anterior cervical region corresponds to the right sternocleidomastoid muscle (arrowhead). The absence of contralateral muscle uptake is due to prior neck dissection. The unilateral focus of uptake posterior to the right sternocleidomastoid muscle (long arrow) corresponds to a cervical lymph node, and symmetric foci within the larynx (short arrows) correspond to the intrinsic laryngeal muscles and cricoarytenoid muscles posteriorly. The results of simultaneous evaluation with PET and CT confirmed the diagnosis of (advanced) metastatic disease in the neck and had a significant impact on clinical management. The patient was started on therapy on the basis of the PET-CT findings.
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Figure 4a. Thyroid carcinoma in a 45-year-old woman with a history of breast cancer who was referred for posttherapy evaluation. Axial PET scan (b) reveals a hypermetabolic focus in a cervical lymph node in the left side of the neck (arrowhead) that is highly suspicious for metastatic disease. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the focus (arrowhead) corresponds to the left thyroid lobe and is consistent with a thyroid nodule. Subsequent ultrasonography demonstrated a multinodular gland with a dominant nodule in the left lower pole. Further investigation with needle biopsy revealed follicular carcinoma of the thyroid gland. PET-CT findings confirmed that the patient had thyroid disease (adenoma or carcinoma) rather than lymph node metastasis; however, the nodule could not be characterized on the basis of PET-CT findings alone.
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Figure 4b. Thyroid carcinoma in a 45-year-old woman with a history of breast cancer who was referred for posttherapy evaluation. Axial PET scan (b) reveals a hypermetabolic focus in a cervical lymph node in the left side of the neck (arrowhead) that is highly suspicious for metastatic disease. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the focus (arrowhead) corresponds to the left thyroid lobe and is consistent with a thyroid nodule. Subsequent ultrasonography demonstrated a multinodular gland with a dominant nodule in the left lower pole. Further investigation with needle biopsy revealed follicular carcinoma of the thyroid gland. PET-CT findings confirmed that the patient had thyroid disease (adenoma or carcinoma) rather than lymph node metastasis; however, the nodule could not be characterized on the basis of PET-CT findings alone.
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Figure 4c. Thyroid carcinoma in a 45-year-old woman with a history of breast cancer who was referred for posttherapy evaluation. Axial PET scan (b) reveals a hypermetabolic focus in a cervical lymph node in the left side of the neck (arrowhead) that is highly suspicious for metastatic disease. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the focus (arrowhead) corresponds to the left thyroid lobe and is consistent with a thyroid nodule. Subsequent ultrasonography demonstrated a multinodular gland with a dominant nodule in the left lower pole. Further investigation with needle biopsy revealed follicular carcinoma of the thyroid gland. PET-CT findings confirmed that the patient had thyroid disease (adenoma or carcinoma) rather than lymph node metastasis; however, the nodule could not be characterized on the basis of PET-CT findings alone.
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Figure 5a. Thyroid nodule in a 51-year-old man with a history of squamous cell carcinoma of the tonsil who was referred for postsurgical evaluation. Axial PET scan (b) reveals a hypermetabolic focus in the right side of the neck (arrow) that is highly suspicious for metastatic disease. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the focus (arrow) corresponds to the right thyroid lobe and is consistent with a thyroid nodule, a finding that was confirmed with subsequent ultrasonography. PET-CT findings confirmed that the patient did not have lymph node metastasis; however, a thyroid nodule requires further investigation with biopsy to rule out a malignant cause within the thyroid gland.
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Figure 5b. Thyroid nodule in a 51-year-old man with a history of squamous cell carcinoma of the tonsil who was referred for postsurgical evaluation. Axial PET scan (b) reveals a hypermetabolic focus in the right side of the neck (arrow) that is highly suspicious for metastatic disease. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the focus (arrow) corresponds to the right thyroid lobe and is consistent with a thyroid nodule, a finding that was confirmed with subsequent ultrasonography. PET-CT findings confirmed that the patient did not have lymph node metastasis; however, a thyroid nodule requires further investigation with biopsy to rule out a malignant cause within the thyroid gland.
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Figure 5c. Thyroid nodule in a 51-year-old man with a history of squamous cell carcinoma of the tonsil who was referred for postsurgical evaluation. Axial PET scan (b) reveals a hypermetabolic focus in the right side of the neck (arrow) that is highly suspicious for metastatic disease. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the focus (arrow) corresponds to the right thyroid lobe and is consistent with a thyroid nodule, a finding that was confirmed with subsequent ultrasonography. PET-CT findings confirmed that the patient did not have lymph node metastasis; however, a thyroid nodule requires further investigation with biopsy to rule out a malignant cause within the thyroid gland.
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Figure 6a. Primary tumor of the larynx in a 45-year-old man with epiglottic carcinoma who was referred for presurgical evaluation. Axial CT (a), PET (b), and PET-CT fusion (c) images show a focus of uptake (arrow) that corresponds to a mass that originates from the larynx and nearly obliterates the lumen on the CT scan. Correlation with CT and PET-CT helped greatly in establishing the diagnosis of primary laryngeal malignancy rather than activated laryngeal muscles. In cases of occult head and neck tumor, differentiation may be difficult without CT correlation. It is essential that the patient remain silent during the period of FDG uptake.
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Figure 6b. Primary tumor of the larynx in a 45-year-old man with epiglottic carcinoma who was referred for presurgical evaluation. Axial CT (a), PET (b), and PET-CT fusion (c) images show a focus of uptake (arrow) that corresponds to a mass that originates from the larynx and nearly obliterates the lumen on the CT scan. Correlation with CT and PET-CT helped greatly in establishing the diagnosis of primary laryngeal malignancy rather than activated laryngeal muscles. In cases of occult head and neck tumor, differentiation may be difficult without CT correlation. It is essential that the patient remain silent during the period of FDG uptake.
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Figure 6c. Primary tumor of the larynx in a 45-year-old man with epiglottic carcinoma who was referred for presurgical evaluation. Axial CT (a), PET (b), and PET-CT fusion (c) images show a focus of uptake (arrow) that corresponds to a mass that originates from the larynx and nearly obliterates the lumen on the CT scan. Correlation with CT and PET-CT helped greatly in establishing the diagnosis of primary laryngeal malignancy rather than activated laryngeal muscles. In cases of occult head and neck tumor, differentiation may be difficult without CT correlation. It is essential that the patient remain silent during the period of FDG uptake.
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Figure 7a. Physiologic laryngeal uptake in a 52-year-old woman with squamous cell carcinoma of the floor of the mouth who had undergone surgery and radiation therapy. Axial CT (a), PET (b), and PET-CT fusion (c) images clearly demonstrate a midline focus of uptake (arrow) that corresponds to the cricoarytenoid muscles located posterior to the thyrocricoid cartilage. Although this site and pattern of uptake are typical for activated vocal cords, CT helps confirm the physiologic nature of the FDG accumulation. Without CT correlation, this focus of uptake may lead to a false-positive finding in patients with malignant processes in this location, particularly in the posttherapy setting.
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Figure 7b. Physiologic laryngeal uptake in a 52-year-old woman with squamous cell carcinoma of the floor of the mouth who had undergone surgery and radiation therapy. Axial CT (a), PET (b), and PET-CT fusion (c) images clearly demonstrate a midline focus of uptake (arrow) that corresponds to the cricoarytenoid muscles located posterior to the thyrocricoid cartilage. Although this site and pattern of uptake are typical for activated vocal cords, CT helps confirm the physiologic nature of the FDG accumulation. Without CT correlation, this focus of uptake may lead to a false-positive finding in patients with malignant processes in this location, particularly in the posttherapy setting.
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Figure 7c. Physiologic laryngeal uptake in a 52-year-old woman with squamous cell carcinoma of the floor of the mouth who had undergone surgery and radiation therapy. Axial CT (a), PET (b), and PET-CT fusion (c) images clearly demonstrate a midline focus of uptake (arrow) that corresponds to the cricoarytenoid muscles located posterior to the thyrocricoid cartilage. Although this site and pattern of uptake are typical for activated vocal cords, CT helps confirm the physiologic nature of the FDG accumulation. Without CT correlation, this focus of uptake may lead to a false-positive finding in patients with malignant processes in this location, particularly in the posttherapy setting.
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Figure 8a. Extranodal disease in a 33-year-old man with a history of aggressive non-Hodgkin lymphoma who had undergone chemotherapy 1 year earlier. Axial PET scan (b) demonstrates intense FDG uptake in the posterosuperior oral cavity (arrows). (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the uptake (arrows) corresponds to the palatine tonsils, with minimal asymmetry seen at CT. In the tonsillar lymphatic tissues, physiologic uptake cannot be differentiated from extranodal lymphoma, especially in cases of subtle CT findings.
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Figure 8b. Extranodal disease in a 33-year-old man with a history of aggressive non-Hodgkin lymphoma who had undergone chemotherapy 1 year earlier. Axial PET scan (b) demonstrates intense FDG uptake in the posterosuperior oral cavity (arrows). (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the uptake (arrows) corresponds to the palatine tonsils, with minimal asymmetry seen at CT. In the tonsillar lymphatic tissues, physiologic uptake cannot be differentiated from extranodal lymphoma, especially in cases of subtle CT findings.
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Figure 8c. Extranodal disease in a 33-year-old man with a history of aggressive non-Hodgkin lymphoma who had undergone chemotherapy 1 year earlier. Axial PET scan (b) demonstrates intense FDG uptake in the posterosuperior oral cavity (arrows). (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the uptake (arrows) corresponds to the palatine tonsils, with minimal asymmetry seen at CT. In the tonsillar lymphatic tissues, physiologic uptake cannot be differentiated from extranodal lymphoma, especially in cases of subtle CT findings.
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Figure 9a. Lymph node metastasis in a 48-year-old man with newly diagnosed squamous cell cancer of the tonsil. Axial PET scan (b) demonstrates intense FDG uptake in the region of the left tonsil (arrow) and in a left cervical lymph node (arrowhead), findings that are consistent with primary and metastatic disease, respectively. (a, c) Axial CT (a) and PET-CT fusion (c) images help confirm that the uptake corresponds to the left palatine tonsil (arrow) and left jugular lymph node (arrowhead). The asymmetric nature of the tonsillar uptake and the presence of lymph node metastasis allow definitive diagnosis.
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Figure 9b. Lymph node metastasis in a 48-year-old man with newly diagnosed squamous cell cancer of the tonsil. Axial PET scan (b) demonstrates intense FDG uptake in the region of the left tonsil (arrow) and in a left cervical lymph node (arrowhead), findings that are consistent with primary and metastatic disease, respectively. (a, c) Axial CT (a) and PET-CT fusion (c) images help confirm that the uptake corresponds to the left palatine tonsil (arrow) and left jugular lymph node (arrowhead). The asymmetric nature of the tonsillar uptake and the presence of lymph node metastasis allow definitive diagnosis.
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Figure 9c. Lymph node metastasis in a 48-year-old man with newly diagnosed squamous cell cancer of the tonsil. Axial PET scan (b) demonstrates intense FDG uptake in the region of the left tonsil (arrow) and in a left cervical lymph node (arrowhead), findings that are consistent with primary and metastatic disease, respectively. (a, c) Axial CT (a) and PET-CT fusion (c) images help confirm that the uptake corresponds to the left palatine tonsil (arrow) and left jugular lymph node (arrowhead). The asymmetric nature of the tonsillar uptake and the presence of lymph node metastasis allow definitive diagnosis.
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Figure 10a. Tonsillar lymphoma in a 20-year-old man with Burkitt lymphoma of the abdomen who was referred for posttherapy evaluation. Axial PET scan (b) demonstrates intense FDG uptake in the region of the tonsils with minimal asymmetry (arrows), a finding that is suspicious for extranodal lymphoma in the regional lymphatic tissues. (a, c) Axial CT (a) and PET-CT fusion (c) images help confirm that the uptake (arrows) corresponds to the palatine tonsils. Furthermore, asymmetric uptake in the left tonsil is seen as a mass that bulges into the lumen on the CT scan. The minimal asymmetry of the tonsillar uptake suggests disease; however, definitive diagnosis cannot be made on the basis of PET-CT findings alone. Subsequent biopsy revealed Burkitt lymphoma of the tonsils.
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Figure 10b. Tonsillar lymphoma in a 20-year-old man with Burkitt lymphoma of the abdomen who was referred for posttherapy evaluation. Axial PET scan (b) demonstrates intense FDG uptake in the region of the tonsils with minimal asymmetry (arrows), a finding that is suspicious for extranodal lymphoma in the regional lymphatic tissues. (a, c) Axial CT (a) and PET-CT fusion (c) images help confirm that the uptake (arrows) corresponds to the palatine tonsils. Furthermore, asymmetric uptake in the left tonsil is seen as a mass that bulges into the lumen on the CT scan. The minimal asymmetry of the tonsillar uptake suggests disease; however, definitive diagnosis cannot be made on the basis of PET-CT findings alone. Subsequent biopsy revealed Burkitt lymphoma of the tonsils.
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Figure 10c. Tonsillar lymphoma in a 20-year-old man with Burkitt lymphoma of the abdomen who was referred for posttherapy evaluation. Axial PET scan (b) demonstrates intense FDG uptake in the region of the tonsils with minimal asymmetry (arrows), a finding that is suspicious for extranodal lymphoma in the regional lymphatic tissues. (a, c) Axial CT (a) and PET-CT fusion (c) images help confirm that the uptake (arrows) corresponds to the palatine tonsils. Furthermore, asymmetric uptake in the left tonsil is seen as a mass that bulges into the lumen on the CT scan. The minimal asymmetry of the tonsillar uptake suggests disease; however, definitive diagnosis cannot be made on the basis of PET-CT findings alone. Subsequent biopsy revealed Burkitt lymphoma of the tonsils.
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Figure 11a. Thymic rebound in a 25-year-old woman with a history of Hodgkin disease who was referred for posttherapy evaluation. Axial PET scan (b) demonstrates findings that are consistent with posttherapy thymic rebound (arrows). (a, c) Axial CT (a) and PET-CT fusion (c) images reveal a symmetric hypermetabolic focus (arrows) that corresponds to the thymus and appears as a bilobed structure with convex lateral borders in the anterosuperior mediastinum at CT.
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Figure 11b. Thymic rebound in a 25-year-old woman with a history of Hodgkin disease who was referred for posttherapy evaluation. Axial PET scan (b) demonstrates findings that are consistent with posttherapy thymic rebound (arrows). (a, c) Axial CT (a) and PET-CT fusion (c) images reveal a symmetric hypermetabolic focus (arrows) that corresponds to the thymus and appears as a bilobed structure with convex lateral borders in the anterosuperior mediastinum at CT.
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Figure 11c. Thymic rebound in a 25-year-old woman with a history of Hodgkin disease who was referred for posttherapy evaluation. Axial PET scan (b) demonstrates findings that are consistent with posttherapy thymic rebound (arrows). (a, c) Axial CT (a) and PET-CT fusion (c) images reveal a symmetric hypermetabolic focus (arrows) that corresponds to the thymus and appears as a bilobed structure with convex lateral borders in the anterosuperior mediastinum at CT.
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Figure 12a. Lymphoma in a 36-year-old man with a history of Hodgkin disease who was referred for posttherapy evaluation for possible residual disease. Axial CT (a), PET (b), and PET-CT fusion (c) images demonstrate a convex right mediastinal hypermetabolic focus (arrow) that is suspicious for residual disease. Although the unilateral manifestation and midmediastinal location of this focus and the presence of associated other abnormal foci of mediastinal uptake do not support thymic rebound, the pattern of uptake resembles thymic uptake. This pattern may be confusing in certain clinical settings, particularly when the pathologic uptake is located more anteriorly in the mediastinum.
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Figure 12b. Lymphoma in a 36-year-old man with a history of Hodgkin disease who was referred for posttherapy evaluation for possible residual disease. Axial CT (a), PET (b), and PET-CT fusion (c) images demonstrate a convex right mediastinal hypermetabolic focus (arrow) that is suspicious for residual disease. Although the unilateral manifestation and midmediastinal location of this focus and the presence of associated other abnormal foci of mediastinal uptake do not support thymic rebound, the pattern of uptake resembles thymic uptake. This pattern may be confusing in certain clinical settings, particularly when the pathologic uptake is located more anteriorly in the mediastinum.
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Figure 12c. Lymphoma in a 36-year-old man with a history of Hodgkin disease who was referred for posttherapy evaluation for possible residual disease. Axial CT (a), PET (b), and PET-CT fusion (c) images demonstrate a convex right mediastinal hypermetabolic focus (arrow) that is suspicious for residual disease. Although the unilateral manifestation and midmediastinal location of this focus and the presence of associated other abnormal foci of mediastinal uptake do not support thymic rebound, the pattern of uptake resembles thymic uptake. This pattern may be confusing in certain clinical settings, particularly when the pathologic uptake is located more anteriorly in the mediastinum.
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Figure 13a. Physiologic thymic uptake in a 23-year-old woman with a history of Hodgkin disease of the chest who was referred for posttherapy evaluation. Axial PET scan (b) demonstrates a unilateral focus of FDG uptake in the superoanterior mediastinum (arrow), a finding that is suspicious for residual disease. Although the uptake is located in the thymic region, its midmediastinal location may suggest viable lymphoma (cf Fig 12). (a, c) Axial CT (a) and PET-CT fusion (c) images help confirm that the anterosuperior mediastinal uptake (arrow) corresponds to thymic tissue, thereby excluding the possibility of residual disease. Although PET-CT is convenient for immediate correlation of images obtained in the same anatomic planes, a recent, separately acquired CT scan would also be helpful in confirming thymic uptake.
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Figure 13b. Physiologic thymic uptake in a 23-year-old woman with a history of Hodgkin disease of the chest who was referred for posttherapy evaluation. Axial PET scan (b) demonstrates a unilateral focus of FDG uptake in the superoanterior mediastinum (arrow), a finding that is suspicious for residual disease. Although the uptake is located in the thymic region, its midmediastinal location may suggest viable lymphoma (cf Fig 12). (a, c) Axial CT (a) and PET-CT fusion (c) images help confirm that the anterosuperior mediastinal uptake (arrow) corresponds to thymic tissue, thereby excluding the possibility of residual disease. Although PET-CT is convenient for immediate correlation of images obtained in the same anatomic planes, a recent, separately acquired CT scan would also be helpful in confirming thymic uptake.
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Figure 13c. Physiologic thymic uptake in a 23-year-old woman with a history of Hodgkin disease of the chest who was referred for posttherapy evaluation. Axial PET scan (b) demonstrates a unilateral focus of FDG uptake in the superoanterior mediastinum (arrow), a finding that is suspicious for residual disease. Although the uptake is located in the thymic region, its midmediastinal location may suggest viable lymphoma (cf Fig 12). (a, c) Axial CT (a) and PET-CT fusion (c) images help confirm that the anterosuperior mediastinal uptake (arrow) corresponds to thymic tissue, thereby excluding the possibility of residual disease. Although PET-CT is convenient for immediate correlation of images obtained in the same anatomic planes, a recent, separately acquired CT scan would also be helpful in confirming thymic uptake.
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Figure 14a. Residual disease in a 36-year-old man with a history of Hodgkin disease who was referred for postchemotherapy evaluation. (a-c) Coronal PET scan (b) shows symmetric hypermetabolic foci in the cervical and supraclavicular regions (small arrows). In addition, there is asymmetric uptake in the right axillary region (large arrow). Coronal CT (a) and PET-CT fusion (c) images help confirm persistent lymphoma in the right axillary lymph nodes (large arrow). No abnormality is seen in the cervical supraclavicular regions that corresponds to the FDG uptake in these regions (small arrows), a finding that is consistent with brown adipose tissue. (d-f) Axial PET scan (e) demonstrates multiple foci of increased FDG uptake in the cervical region. There is also a unilateral focus of uptake in the right jugular region (arrow) that is suspicious for malignancy. CT (d) and PET-CT fusion (f) images help confirm that the focal FDG uptake on the right side (arrowhead) corresponds to a jugular lymph node, a finding that is consistent with residual Hodgkin disease. The uptake in the brown adipose tissue renders interpretation difficult by obscuring the underlying lymph nodes that harbor viable residual disease. It is essential that this pattern of uptake be evaluated simultaneously with CT.
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Figure 14b. Residual disease in a 36-year-old man with a history of Hodgkin disease who was referred for postchemotherapy evaluation. (a-c) Coronal PET scan (b) shows symmetric hypermetabolic foci in the cervical and supraclavicular regions (small arrows). In addition, there is asymmetric uptake in the right axillary region (large arrow). Coronal CT (a) and PET-CT fusion (c) images help confirm persistent lymphoma in the right axillary lymph nodes (large arrow). No abnormality is seen in the cervical supraclavicular regions that corresponds to the FDG uptake in these regions (small arrows), a finding that is consistent with brown adipose tissue. (d-f) Axial PET scan (e) demonstrates multiple foci of increased FDG uptake in the cervical region. There is also a unilateral focus of uptake in the right jugular region (arrow) that is suspicious for malignancy. CT (d) and PET-CT fusion (f) images help confirm that the focal FDG uptake on the right side (arrowhead) corresponds to a jugular lymph node, a finding that is consistent with residual Hodgkin disease. The uptake in the brown adipose tissue renders interpretation difficult by obscuring the underlying lymph nodes that harbor viable residual disease. It is essential that this pattern of uptake be evaluated simultaneously with CT.
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Figure 14c. Residual disease in a 36-year-old man with a history of Hodgkin disease who was referred for postchemotherapy evaluation. (a-c) Coronal PET scan (b) shows symmetric hypermetabolic foci in the cervical and supraclavicular regions (small arrows). In addition, there is asymmetric uptake in the right axillary region (large arrow). Coronal CT (a) and PET-CT fusion (c) images help confirm persistent lymphoma in the right axillary lymph nodes (large arrow). No abnormality is seen in the cervical supraclavicular regions that corresponds to the FDG uptake in these regions (small arrows), a finding that is consistent with brown adipose tissue. (d-f) Axial PET scan (e) demonstrates multiple foci of increased FDG uptake in the cervical region. There is also a unilateral focus of uptake in the right jugular region (arrow) that is suspicious for malignancy. CT (d) and PET-CT fusion (f) images help confirm that the focal FDG uptake on the right side (arrowhead) corresponds to a jugular lymph node, a finding that is consistent with residual Hodgkin disease. The uptake in the brown adipose tissue renders interpretation difficult by obscuring the underlying lymph nodes that harbor viable residual disease. It is essential that this pattern of uptake be evaluated simultaneously with CT.
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Figure 14d. Residual disease in a 36-year-old man with a history of Hodgkin disease who was referred for postchemotherapy evaluation. (a-c) Coronal PET scan (b) shows symmetric hypermetabolic foci in the cervical and supraclavicular regions (small arrows). In addition, there is asymmetric uptake in the right axillary region (large arrow). Coronal CT (a) and PET-CT fusion (c) images help confirm persistent lymphoma in the right axillary lymph nodes (large arrow). No abnormality is seen in the cervical supraclavicular regions that corresponds to the FDG uptake in these regions (small arrows), a finding that is consistent with brown adipose tissue. (d-f) Axial PET scan (e) demonstrates multiple foci of increased FDG uptake in the cervical region. There is also a unilateral focus of uptake in the right jugular region (arrow) that is suspicious for malignancy. CT (d) and PET-CT fusion (f) images help confirm that the focal FDG uptake on the right side (arrowhead) corresponds to a jugular lymph node, a finding that is consistent with residual Hodgkin disease. The uptake in the brown adipose tissue renders interpretation difficult by obscuring the underlying lymph nodes that harbor viable residual disease. It is essential that this pattern of uptake be evaluated simultaneously with CT.
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Figure 14e. Residual disease in a 36-year-old man with a history of Hodgkin disease who was referred for postchemotherapy evaluation. (a-c) Coronal PET scan (b) shows symmetric hypermetabolic foci in the cervical and supraclavicular regions (small arrows). In addition, there is asymmetric uptake in the right axillary region (large arrow). Coronal CT (a) and PET-CT fusion (c) images help confirm persistent lymphoma in the right axillary lymph nodes (large arrow). No abnormality is seen in the cervical supraclavicular regions that corresponds to the FDG uptake in these regions (small arrows), a finding that is consistent with brown adipose tissue. (d-f) Axial PET scan (e) demonstrates multiple foci of increased FDG uptake in the cervical region. There is also a unilateral focus of uptake in the right jugular region (arrow) that is suspicious for malignancy. CT (d) and PET-CT fusion (f) images help confirm that the focal FDG uptake on the right side (arrowhead) corresponds to a jugular lymph node, a finding that is consistent with residual Hodgkin disease. The uptake in the brown adipose tissue renders interpretation difficult by obscuring the underlying lymph nodes that harbor viable residual disease. It is essential that this pattern of uptake be evaluated simultaneously with CT.
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Figure 14f. Residual disease in a 36-year-old man with a history of Hodgkin disease who was referred for postchemotherapy evaluation. (a-c) Coronal PET scan (b) shows symmetric hypermetabolic foci in the cervical and supraclavicular regions (small arrows). In addition, there is asymmetric uptake in the right axillary region (large arrow). Coronal CT (a) and PET-CT fusion (c) images help confirm persistent lymphoma in the right axillary lymph nodes (large arrow). No abnormality is seen in the cervical supraclavicular regions that corresponds to the FDG uptake in these regions (small arrows), a finding that is consistent with brown adipose tissue. (d-f) Axial PET scan (e) demonstrates multiple foci of increased FDG uptake in the cervical region. There is also a unilateral focus of uptake in the right jugular region (arrow) that is suspicious for malignancy. CT (d) and PET-CT fusion (f) images help confirm that the focal FDG uptake on the right side (arrowhead) corresponds to a jugular lymph node, a finding that is consistent with residual Hodgkin disease. The uptake in the brown adipose tissue renders interpretation difficult by obscuring the underlying lymph nodes that harbor viable residual disease. It is essential that this pattern of uptake be evaluated simultaneously with CT.
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Figure 15a. Nonneoplastic esophageal uptake in a 21-year-old woman with a history of non-Hodgkin lymphoma who was referred for restaging following therapy. Axial PET scan (b) shows a focus of metabolic activity in the midline in the lower chest, inferior to the heart and adjacent to the abdominal aorta (arrowhead). A malignant process in a lymph node in this region cannot be excluded on the basis of PET findings alone. (a, c) Axial CT (a) and PET-CT fusion (c) images reveal that the focal FDG uptake in the inferoposterior mediastinum (arrowhead) corresponds to the distal esophagus. This focus of uptake is probably due to physiologic muscle uptake at the gastroesophageal junction or inflammatory changes secondary to gastroesophageal reflux. No tumor, wall thickening, or lymphadenopathy is appreciated in this region.
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Figure 15b. Nonneoplastic esophageal uptake in a 21-year-old woman with a history of non-Hodgkin lymphoma who was referred for restaging following therapy. Axial PET scan (b) shows a focus of metabolic activity in the midline in the lower chest, inferior to the heart and adjacent to the abdominal aorta (arrowhead). A malignant process in a lymph node in this region cannot be excluded on the basis of PET findings alone. (a, c) Axial CT (a) and PET-CT fusion (c) images reveal that the focal FDG uptake in the inferoposterior mediastinum (arrowhead) corresponds to the distal esophagus. This focus of uptake is probably due to physiologic muscle uptake at the gastroesophageal junction or inflammatory changes secondary to gastroesophageal reflux. No tumor, wall thickening, or lymphadenopathy is appreciated in this region.
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Figure 15c. Nonneoplastic esophageal uptake in a 21-year-old woman with a history of non-Hodgkin lymphoma who was referred for restaging following therapy. Axial PET scan (b) shows a focus of metabolic activity in the midline in the lower chest, inferior to the heart and adjacent to the abdominal aorta (arrowhead). A malignant process in a lymph node in this region cannot be excluded on the basis of PET findings alone. (a, c) Axial CT (a) and PET-CT fusion (c) images reveal that the focal FDG uptake in the inferoposterior mediastinum (arrowhead) corresponds to the distal esophagus. This focus of uptake is probably due to physiologic muscle uptake at the gastroesophageal junction or inflammatory changes secondary to gastroesophageal reflux. No tumor, wall thickening, or lymphadenopathy is appreciated in this region.
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Figure 16a. Esophageal adenocarcinoma in a 52-year-old man who was referred for presurgical evaluation. Axial PET scan (b) demonstrates an intense focus of metabolic activity (arrowhead) (cf Fig 15). If no clinical information were available, it would be unclear whether this focus represented physiologic FDG uptake in the distal esophagus or a lymphatic or esophageal malignancy. (a, c) Axial CT (a) and PET-CT fusion (c) images show significant thickening of the distal esophagus that almost obliterates the lumen (arrowhead). This finding corresponds to the intense uptake seen at PET and is consistent with esophageal adenocarcinoma.
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Figure 16b. Esophageal adenocarcinoma in a 52-year-old man who was referred for presurgical evaluation. Axial PET scan (b) demonstrates an intense focus of metabolic activity (arrowhead) (cf Fig 15). If no clinical information were available, it would be unclear whether this focus represented physiologic FDG uptake in the distal esophagus or a lymphatic or esophageal malignancy. (a, c) Axial CT (a) and PET-CT fusion (c) images show significant thickening of the distal esophagus that almost obliterates the lumen (arrowhead). This finding corresponds to the intense uptake seen at PET and is consistent with esophageal adenocarcinoma.
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Figure 16c. Esophageal adenocarcinoma in a 52-year-old man who was referred for presurgical evaluation. Axial PET scan (b) demonstrates an intense focus of metabolic activity (arrowhead) (cf Fig 15). If no clinical information were available, it would be unclear whether this focus represented physiologic FDG uptake in the distal esophagus or a lymphatic or esophageal malignancy. (a, c) Axial CT (a) and PET-CT fusion (c) images show significant thickening of the distal esophagus that almost obliterates the lumen (arrowhead). This finding corresponds to the intense uptake seen at PET and is consistent with esophageal adenocarcinoma.
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Figure 17a. Physiologic diaphragmatic uptake in a 49-year-old woman with a history of abdominal lymphoma and severe chronic obstructive pulmonary disease who was referred for posttherapy follow-up. Axial PET scan (b) demonstrates bilateral hypermetabolic foci in the upper midabdomen that are slightly more prominent on the right side than on the left (arrowheads). These foci of uptake may be attributed to recurrent lymphoma in the regional abdominal lymph nodes. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that these foci (arrowheads) correspond to the diaphragmatic cruces. The combined use of PET and CT in this case allowed definitive exclusion of relapse of lymphoma.
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Figure 17b. Physiologic diaphragmatic uptake in a 49-year-old woman with a history of abdominal lymphoma and severe chronic obstructive pulmonary disease who was referred for posttherapy follow-up. Axial PET scan (b) demonstrates bilateral hypermetabolic foci in the upper midabdomen that are slightly more prominent on the right side than on the left (arrowheads). These foci of uptake may be attributed to recurrent lymphoma in the regional abdominal lymph nodes. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that these foci (arrowheads) correspond to the diaphragmatic cruces. The combined use of PET and CT in this case allowed definitive exclusion of relapse of lymphoma.
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Figure 17c. Physiologic diaphragmatic uptake in a 49-year-old woman with a history of abdominal lymphoma and severe chronic obstructive pulmonary disease who was referred for posttherapy follow-up. Axial PET scan (b) demonstrates bilateral hypermetabolic foci in the upper midabdomen that are slightly more prominent on the right side than on the left (arrowheads). These foci of uptake may be attributed to recurrent lymphoma in the regional abdominal lymph nodes. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that these foci (arrowheads) correspond to the diaphragmatic cruces. The combined use of PET and CT in this case allowed definitive exclusion of relapse of lymphoma.
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Figure 18a. Recurrent disease in a 56-year-old man with esophageal carcinoma. The patient had undergone esophagectomy and was referred for follow-up evaluation. Axial PET scan (b) demonstrates a hypermetabolic focus left of the midline in the upper abdomen (arrow) (cf Fig 17). This focus is consistent with metastatic esophageal carcinoma in the regional lymph nodes or unilateral uptake in the left diaphragmatic crux. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the hypermetabolic focus seen at PET corresponds to an enlarged lymph node (arrow), a finding that is consistent with recurrent disease. The patient subsequently underwent chemotherapy on the basis of the PET-CT findings.
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Figure 18b. Recurrent disease in a 56-year-old man with esophageal carcinoma. The patient had undergone esophagectomy and was referred for follow-up evaluation. Axial PET scan (b) demonstrates a hypermetabolic focus left of the midline in the upper abdomen (arrow) (cf Fig 17). This focus is consistent with metastatic esophageal carcinoma in the regional lymph nodes or unilateral uptake in the left diaphragmatic crux. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the hypermetabolic focus seen at PET corresponds to an enlarged lymph node (arrow), a finding that is consistent with recurrent disease. The patient subsequently underwent chemotherapy on the basis of the PET-CT findings.
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Figure 18c. Recurrent disease in a 56-year-old man with esophageal carcinoma. The patient had undergone esophagectomy and was referred for follow-up evaluation. Axial PET scan (b) demonstrates a hypermetabolic focus left of the midline in the upper abdomen (arrow) (cf Fig 17). This focus is consistent with metastatic esophageal carcinoma in the regional lymph nodes or unilateral uptake in the left diaphragmatic crux. (a, c) Axial CT (a) and PET-CT fusion (c) images demonstrate that the hypermetabolic focus seen at PET corresponds to an enlarged lymph node (arrow), a finding that is consistent with recurrent disease. The patient subsequently underwent chemotherapy on the basis of the PET-CT findings.
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Figure 19a. Physiologic gastric uptake in a 52-year-old man with colorectal cancer who had undergone surgical tumor resection. (a) Coronal PET scans demonstrate a diffuse hypermetabolic focus in the left upper quadrant (arrow) that corresponds to the stomach or the transverse colon. (b-d) Coronal CT (b), PET (c), and PET-CT fusion (d) images help confirm that the focus of activity (arrow) corresponds to physiologic uptake in the stomach.
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Figure 19b. Physiologic gastric uptake in a 52-year-old man with colorectal cancer who had undergone surgical tumor resection. (a) Coronal PET scans demonstrate a diffuse hypermetabolic focus in the left upper quadrant (arrow) that corresponds to the stomach or the transverse colon. (b-d) Coronal CT (b), PET (c), and PET-CT fusion (d) images help confirm that the focus of activity (arrow) corresponds to physiologic uptake in the stomach.
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Figure 19c. Physiologic gastric uptake in a 52-year-old man with colorectal cancer who had undergone surgical tumor resection. (a) Coronal PET scans demonstrate a diffuse hypermetabolic focus in the left upper quadrant (arrow) that corresponds to the stomach or the transverse colon. (b-d) Coronal CT (b), PET (c), and PET-CT fusion (d) images help confirm that the focus of activity (arrow) corresponds to physiologic uptake in the stomach.
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Figure 19d. Physiologic gastric uptake in a 52-year-old man with colorectal cancer who had undergone surgical tumor resection. (a) Coronal PET scans demonstrate a diffuse hypermetabolic focus in the left upper quadrant (arrow) that corresponds to the stomach or the transverse colon. (b-d) Coronal CT (b), PET (c), and PET-CT fusion (d) images help confirm that the focus of activity (arrow) corresponds to physiologic uptake in the stomach.
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Figure 20a. Gastritis in a 47-year-old woman with a history of breast cancer. (a) Coronal PET scans demonstrate a hypermetabolic area in the left upper quadrant of the abdomen in the stomach region (arrow). (b-d) Coronal PET scan (c) shows linear activity (black arrow). Coronal CT (b) and PET-CT fusion (d) images demonstrate that this area of uptake (white arrow) corresponds to the contour of the stomach. It was later confirmed that the patient suffered from gastritis at the time of the PET-CT study. Note the asymmetric uptake in the left breast, a finding that is consistent with breast cancer.
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