FDG PET of Infection and Inflammation

doi:10.1148/rg.255045122

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FDG PET of Infection and Inflammation¹

Charito Love, MD, Maria B. Tomas, MD, Gene G. Tronco, MD and Christopher J. Palestro, MD

¹ From the Division of Nuclear Medicine, Long Island Jewish Medical Center, 270–05 76th Ave, New Hyde Park, NY 11040. Presented as an education exhibit at the 2003 RSNA Annual Meeting. Received June 4, 2004; revision requested August 19 and received October 25; accepted November 9. All authors have no financial relationships to disclose.

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Figure 1a. Iatrogenic infection of surgical reinforcement mesh in a 50-year-old woman who had undergone repair of a ventral hernia 2 months earlier. (a) FDG PET scan shows intense radiotracer accumulation within the spleen, a finding that raised suspicion for tumor. However, additional work-up for malignancy was negative. (b) On a repeat FDG PET scan obtained 10 months later when the infection had resolved and the patient was in good health, the spleen is barely discernible.

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Figure 1b. Iatrogenic infection of surgical reinforcement mesh in a 50-year-old woman who had undergone repair of a ventral hernia 2 months earlier. (a) FDG PET scan shows intense radiotracer accumulation within the spleen, a finding that raised suspicion for tumor. However, additional work-up for malignancy was negative. (b) On a repeat FDG PET scan obtained 10 months later when the infection had resolved and the patient was in good health, the spleen is barely discernible.

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Figure 2a. Fungal pneumonia in a 40-year-old man with AIDS and newly diagnosed anaplastic lymphoma. (a) Computed tomographic (CT) scan demonstrates a 6 x 3.5-cm thick-walled cavitary lesion in the posterior segment of the right lower lung. (b) FDG PET scan demonstrates intense, heterogeneous accumulation of radiotracer in the posterior aspect of the right lower lung, a finding that corresponds to the abnormality identified at CT and that could indicate lymphomatous involvement of the pulmonary parenchyma. The final diagnosis, however, was fungal pneumonia. It was not possible to distinguish lymphoma from infection on the basis of the FDG PET finding alone.

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Figure 2b. Fungal pneumonia in a 40-year-old man with AIDS and newly diagnosed anaplastic lymphoma. (a) Computed tomographic (CT) scan demonstrates a 6 x 3.5-cm thick-walled cavitary lesion in the posterior segment of the right lower lung. (b) FDG PET scan demonstrates intense, heterogeneous accumulation of radiotracer in the posterior aspect of the right lower lung, a finding that corresponds to the abnormality identified at CT and that could indicate lymphomatous involvement of the pulmonary parenchyma. The final diagnosis, however, was fungal pneumonia. It was not possible to distinguish lymphoma from infection on the basis of the FDG PET finding alone.

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Figure 3a. (a, b) Toxoplasmosis in an AIDS patient. (a) Contrast material–enhanced T1-weighted MR image shows an enhancing lesion in the right frontal operculum. (b) On an FDG PET scan, the lesion is hypometabolic. The final diagnosis was toxoplasmosis. (c, d) CNS lymphoma in a different AIDS patient. (c) Contrast-enhanced T1-weighted MR image reveals an enhancing mass in the splenium of the corpus callosum. (d) On an FDG PET scan, the lesion is hypermetabolic. The lesion subsequently proved to be lymphoma.

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Figure 3b. (a, b) Toxoplasmosis in an AIDS patient. (a) Contrast material–enhanced T1-weighted MR image shows an enhancing lesion in the right frontal operculum. (b) On an FDG PET scan, the lesion is hypometabolic. The final diagnosis was toxoplasmosis. (c, d) CNS lymphoma in a different AIDS patient. (c) Contrast-enhanced T1-weighted MR image reveals an enhancing mass in the splenium of the corpus callosum. (d) On an FDG PET scan, the lesion is hypermetabolic. The lesion subsequently proved to be lymphoma.

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Figure 3c. (a, b) Toxoplasmosis in an AIDS patient. (a) Contrast material–enhanced T1-weighted MR image shows an enhancing lesion in the right frontal operculum. (b) On an FDG PET scan, the lesion is hypometabolic. The final diagnosis was toxoplasmosis. (c, d) CNS lymphoma in a different AIDS patient. (c) Contrast-enhanced T1-weighted MR image reveals an enhancing mass in the splenium of the corpus callosum. (d) On an FDG PET scan, the lesion is hypermetabolic. The lesion subsequently proved to be lymphoma.

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Figure 3d. (a, b) Toxoplasmosis in an AIDS patient. (a) Contrast material–enhanced T1-weighted MR image shows an enhancing lesion in the right frontal operculum. (b) On an FDG PET scan, the lesion is hypometabolic. The final diagnosis was toxoplasmosis. (c, d) CNS lymphoma in a different AIDS patient. (c) Contrast-enhanced T1-weighted MR image reveals an enhancing mass in the splenium of the corpus callosum. (d) On an FDG PET scan, the lesion is hypermetabolic. The lesion subsequently proved to be lymphoma.

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Figure 4a. Metastatic renal cell carcinoma in an 81-year-old woman who presented with persistent fevers and no localizing signs. (a) FDG PET scan demonstrates a hypermetabolic focus in the mediastinum. (b) CT scan reveals mediastinal lymphadenopathy. Biopsy results confirmed mediastinal lymph node involvement by metastatic renal cell carcinoma.

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Figure 4b. Metastatic renal cell carcinoma in an 81-year-old woman who presented with persistent fevers and no localizing signs. (a) FDG PET scan demonstrates a hypermetabolic focus in the mediastinum. (b) CT scan reveals mediastinal lymphadenopathy. Biopsy results confirmed mediastinal lymph node involvement by metastatic renal cell carcinoma.

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Figure 5. Infected bypass graft. Axial (left) and coronal (right) FDG PET scans demonstrate intense radiotracer activity in an infected left femoral artery bypass graft.

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Figure 6a. Infective endocarditis in a patient who had undergone mitral valve replacement. FDG PET was performed because of persistent bacteremia. (a) Axial (left) and coronal (right) FDG PET scans show a focus of increased intracardiac activity. Results of echocardiography confirmed the presence of valvular vegetations and a mitral annular abscess. (b) ¹¹¹In-labeled leukocyte image is unremarkable.

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Figure 6b. Infective endocarditis in a patient who had undergone mitral valve replacement. FDG PET was performed because of persistent bacteremia. (a) Axial (left) and coronal (right) FDG PET scans show a focus of increased intracardiac activity. Results of echocardiography confirmed the presence of valvular vegetations and a mitral annular abscess. (b) ¹¹¹In-labeled leukocyte image is unremarkable.

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Figure 7a. Pulmonary embolism with pulmonary infarction in a 31-year-old woman who had been successfully treated for endometritis. The patient presented with persistent fevers but no localizing signs or symptoms. (a) Anterior (left) and posterior (right) ¹¹¹In-labeled leukocyte images are normal. FDG PET was performed in an effort to identify the source of the patient’s fevers. (b) Axial (left) and coronal (right) FDG PET scans show evidence of a left-sided pleural effusion and a hypermetabolic pleura-based focus in the left lower lung. CT pulmonary angiography was performed because malignancy was thought to be clinically unlikely and because of the propensity of FDG to accumulate in thromboembolic disease. (c, d) CT pulmonary angiograms show left lower lobe pulmonary emboli (arrowhead in c) and a nonenhancing wedge-shaped lesion in the periphery of the left lower lung (d) corresponding to the hypermetabolic focus seen at FDG PET. The final diagnosis was pulmonary embolism with pulmonary infarction. This case illustrates the importance of sensitivity when evaluating patients with FUO. The labeled leukocyte study correctly excluded infection as the source of the patient’s fever but provided no additional information about the nature or location of the source of the fever. FDG, although not providing a specific diagnosis, did help localize the source of the FUO, facilitating the diagnosis with subsequent studies.

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Figure 7b. Pulmonary embolism with pulmonary infarction in a 31-year-old woman who had been successfully treated for endometritis. The patient presented with persistent fevers but no localizing signs or symptoms. (a) Anterior (left) and posterior (right) ¹¹¹In-labeled leukocyte images are normal. FDG PET was performed in an effort to identify the source of the patient’s fevers. (b) Axial (left) and coronal (right) FDG PET scans show evidence of a left-sided pleural effusion and a hypermetabolic pleura-based focus in the left lower lung. CT pulmonary angiography was performed because malignancy was thought to be clinically unlikely and because of the propensity of FDG to accumulate in thromboembolic disease. (c, d) CT pulmonary angiograms show left lower lobe pulmonary emboli (arrowhead in c) and a nonenhancing wedge-shaped lesion in the periphery of the left lower lung (d) corresponding to the hypermetabolic focus seen at FDG PET. The final diagnosis was pulmonary embolism with pulmonary infarction. This case illustrates the importance of sensitivity when evaluating patients with FUO. The labeled leukocyte study correctly excluded infection as the source of the patient’s fever but provided no additional information about the nature or location of the source of the fever. FDG, although not providing a specific diagnosis, did help localize the source of the FUO, facilitating the diagnosis with subsequent studies.

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Figure 7c. Pulmonary embolism with pulmonary infarction in a 31-year-old woman who had been successfully treated for endometritis. The patient presented with persistent fevers but no localizing signs or symptoms. (a) Anterior (left) and posterior (right) ¹¹¹In-labeled leukocyte images are normal. FDG PET was performed in an effort to identify the source of the patient’s fevers. (b) Axial (left) and coronal (right) FDG PET scans show evidence of a left-sided pleural effusion and a hypermetabolic pleura-based focus in the left lower lung. CT pulmonary angiography was performed because malignancy was thought to be clinically unlikely and because of the propensity of FDG to accumulate in thromboembolic disease. (c, d) CT pulmonary angiograms show left lower lobe pulmonary emboli (arrowhead in c) and a nonenhancing wedge-shaped lesion in the periphery of the left lower lung (d) corresponding to the hypermetabolic focus seen at FDG PET. The final diagnosis was pulmonary embolism with pulmonary infarction. This case illustrates the importance of sensitivity when evaluating patients with FUO. The labeled leukocyte study correctly excluded infection as the source of the patient’s fever but provided no additional information about the nature or location of the source of the fever. FDG, although not providing a specific diagnosis, did help localize the source of the FUO, facilitating the diagnosis with subsequent studies.

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Figure 7d. Pulmonary embolism with pulmonary infarction in a 31-year-old woman who had been successfully treated for endometritis. The patient presented with persistent fevers but no localizing signs or symptoms. (a) Anterior (left) and posterior (right) ¹¹¹In-labeled leukocyte images are normal. FDG PET was performed in an effort to identify the source of the patient’s fevers. (b) Axial (left) and coronal (right) FDG PET scans show evidence of a left-sided pleural effusion and a hypermetabolic pleura-based focus in the left lower lung. CT pulmonary angiography was performed because malignancy was thought to be clinically unlikely and because of the propensity of FDG to accumulate in thromboembolic disease. (c, d) CT pulmonary angiograms show left lower lobe pulmonary emboli (arrowhead in c) and a nonenhancing wedge-shaped lesion in the periphery of the left lower lung (d) corresponding to the hypermetabolic focus seen at FDG PET. The final diagnosis was pulmonary embolism with pulmonary infarction. This case illustrates the importance of sensitivity when evaluating patients with FUO. The labeled leukocyte study correctly excluded infection as the source of the patient’s fever but provided no additional information about the nature or location of the source of the fever. FDG, although not providing a specific diagnosis, did help localize the source of the FUO, facilitating the diagnosis with subsequent studies.

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Figure 8a. Metastatic involvement in a patient with a history of colon cancer and fever. (a) CT scan shows a destructive soft-tissue mass involving the sacrum. (b) FDG PET scan shows the mass to be hypermetabolic but does not help differentiate infection from tumor. The final diagnosis was metastatic colon carcinoma.

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Figure 8b. Metastatic involvement in a patient with a history of colon cancer and fever. (a) CT scan shows a destructive soft-tissue mass involving the sacrum. (b) FDG PET scan shows the mass to be hypermetabolic but does not help differentiate infection from tumor. The final diagnosis was metastatic colon carcinoma.

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Figure 9. FDG PET scan obtained in a patient who had undergone abdominal surgery 2 months earlier demonstrates a linear area of intense radiotracer activity (arrowheads) representing a normally healed surgical incision.

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Figure 10. FDG PET scans obtained in a patient who had undergone total right knee replacement 3 months earlier show intense radiotracer activity along the lateral margin of the asymptomatic, uninfected replacement. More extensive investigation is needed to clarify the role of FDG PET in the evaluation of postoperative infection.

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Figure 11a. (a) Infected left hip prosthesis. FDG PET scan shows increased periprosthetic radiotracer activity at the bone-prosthesis interface along the lateral aspect of the femoral component of the prosthesis. (b) Aseptically loosened left hip prosthesis. FDG PET scan demonstrates uptake similar to that seen in a along the lateral margin of the prosthesis. Bone-prosthesis interface activity at FDG PET, once thought to be specific for infection, is probably related to osteolysis, which is present in both infection and loosening.

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Figure 11b. (a) Infected left hip prosthesis. FDG PET scan shows increased periprosthetic radiotracer activity at the bone-prosthesis interface along the lateral aspect of the femoral component of the prosthesis. (b) Aseptically loosened left hip prosthesis. FDG PET scan demonstrates uptake similar to that seen in a along the lateral margin of the prosthesis. Bone-prosthesis interface activity at FDG PET, once thought to be specific for infection, is probably related to osteolysis, which is present in both infection and loosening.

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Figure 12a. Spinal osteomyelitis. (a) FDG PET scan shows intense radiotracer accumulation in the lower lumbar spine. (b) Coronal image from a gallium SPECT study shows a similar abnormality.

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Figure 12b. Spinal osteomyelitis. (a) FDG PET scan shows intense radiotracer accumulation in the lower lumbar spine. (b) Coronal image from a gallium SPECT study shows a similar abnormality.

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Figure 13. Active sarcoidosis. Axial (left) and coronal (right) FDG PET scans show intense radiotracer activity in the mediastinum. In patients with sarcoidosis, FDG PET can be used to monitor disease activity and response to therapy.

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Figure 14. Vasculitis. FDG PET scan shows increased radiotracer activity in the major arteries of the thorax, abdomen, and pelvis. (Case courtesy of W. J. G. Oyen, MD, PhD, Department of Nuclear Medicine, University Medical Center, Nijmegen, The Netherlands.)

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Figure 15a. Osteomyelitis in an 80-year-old woman who had undergone insertion of spinal hardware 6 months earlier. (a) Axial CT scan demonstrates osteopenia and destruction of the L4 vertebral body. (b) Axial FDG PET scan demonstrates increased activity in the lower lumbar spine. PET-CT was performed owing to increasing back pain. (c) Axial coregistered PET-CT scan helps confirm that the abnormal FDG accumulation seen in b involves the bone. (Case courtesy of K. D. Stumpe, MD, Division of Nuclear Medicine, University Hospital, Zurich, Switzerland.)

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Figure 15b. Osteomyelitis in an 80-year-old woman who had undergone insertion of spinal hardware 6 months earlier. (a) Axial CT scan demonstrates osteopenia and destruction of the L4 vertebral body. (b) Axial FDG PET scan demonstrates increased activity in the lower lumbar spine. PET-CT was performed owing to increasing back pain. (c) Axial coregistered PET-CT scan helps confirm that the abnormal FDG accumulation seen in b involves the bone. (Case courtesy of K. D. Stumpe, MD, Division of Nuclear Medicine, University Hospital, Zurich, Switzerland.)

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Figure 15c. Osteomyelitis in an 80-year-old woman who had undergone insertion of spinal hardware 6 months earlier. (a) Axial CT scan demonstrates osteopenia and destruction of the L4 vertebral body. (b) Axial FDG PET scan demonstrates increased activity in the lower lumbar spine. PET-CT was performed owing to increasing back pain. (c) Axial coregistered PET-CT scan helps confirm that the abnormal FDG accumulation seen in b involves the bone. (Case courtesy of K. D. Stumpe, MD, Division of Nuclear Medicine, University Hospital, Zurich, Switzerland.)

FDG PET of Infection and Inflammation1

FDG PET of Infection and Inflammation¹