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Click Calcified lymph node with AC artifact in a 64-year- old male with a history of left-sided primary squamous cell carcinoma of the lung referred for a staging PET/CT exam. Axial CT images show the area of uptake to correspond to a calcified right paratracheal lymph node (HU: min 365, max 3017, mean 2526). The non-AC axial PET (Image stack 2) shows minimal FDG activity in suspected area as compared to the attenuation corrected image (Fig. 1d), and therefore is most likely an AC artifact superimposed on minimal inflammatory uptake from prior inflammatory disease. At mediastinoscopy, this node was histologically proven to be inflammatory.

Click Calcified lymph node with AC artifact in a 64-year- old male with a history of left-sided primary squamous cell carcinoma of the lung referred for a staging PET/CT exam. Scan was performed 60 minutes after injection of 12-16 mCi of FDG tracer. CT based attenuation correction algorithm was done using two iterations and 8 subsets. The non-AC axial PET image shows minimal FDG activity in suspected area, as compared to the attenuation corrected image (Fig. 1d), and therefore is most likely an AC artifact superimposed on minimal inflammatory uptake from prior inflammatory disease. At mediastinoscopy, this node was histologically proven to be inflammatory.

Click Calcified lymph node with AC artifact in a 69-year-old male with a history of primary esophageal carcinoma with localized disease having undergone esophagectomy and was now referred for a six-month follow up PET/CT scan. Axial CT shows the area of uptake to correspond to a large calcified subcarinal lymph node (HU: min 435, max 1766, mean 1073). The non-AC axial PET image (Image stack 4) shows no evidence of FDG activity in the suspected area proving the area to be an AC artifact, as compared to the attenuation corrected image (Fig. 2d).

Click Calcified lymph node with AC artifact in a 69-year-old male with a history of primary esophageal carcinoma with localized disease having undergone esophagectomy and was now referred for a six-month follow up PET/CT scan. Scan was performed 60 minutes after injection of 12-16 mCi of FDG tracer. CT based attenuation correction algorithm was done using two iterations and 8 subsets. Axial AC PET shows a focal area of intense FDG uptake in the subcarinal area. Axial CT and fused axial PET/CT images (Fig. 2b,c) show the area of uptake to correspond to a large calcified subcarinal lymph node (HU: min 435, max 1766, mean 1073). The non-AC axial PET image (Image stack 5) shows no evidence of FDG activity in the suspected area proving the area to be an AC artifact, as compared to the attenuation corrected images.

Click Calcified lymph node with AC artifact in a 69-year-old male with a history of primary esophageal carcinoma with localized disease having undergone esophagectomy and was now referred for a six-month follow up PET/CT scan. Scan was performed 60 minutes after injection of 12-16 mCi of FDG tracer. The non-AC axial PET image shows no evidence of FDG activity in the suspected area proving the area to be an AC artifact, as compared to the attenuation corrected images (Image stack 4).

Click Calcified lymph node with AC artifact in a 66-year-old female with a history of esophageal carcinoma, status post esophagectomy, with local recurrence, who had both chemotherapy and radiation and is now referred for restaging. Axial CT shows the area of uptake to correspond to a small calcified lymph node (HU: min 514, max 1372, mean 992). The non-AC fused axial PET/CT image (Fig. 3e) shows no evidence of FDG activity in the suspected area proving the area to be an AC artifact, as compared to the attenuation corrected image (Fig. 3d).

Click Calcified lymph node with AC artifact in a 66-year-old female with a history of esophageal carcinoma, status post esophagectomy, with local recurrence, who had both chemotherapy and radiation and is now referred for restaging. Scan was performed 60 minutes after injection of 12-16 mCi of FDG tracer, with the following parameters: 120 kVp, 280mAs, 5 mm slice thickness, and CT based attenuation correction algorithm using two iterations and 8 subsets. Coronal AC PET shows a focal area of intense FDG uptake between the aorta and mid-thoracic vertebral body. Axial CT (Image stack 6) shows the area of uptake to correspond to a small calcified lymph node (HU: min 514, max 1372, mean 992). The non-AC fused axial PET/CT image (Fig. 3e) shows no evidence of FDG activity in the suspected area proving the area to be an AC artifact, as compared to the attenuation corrected images.

Click Large calcified lymph node without AC artifact in an 85-year-old female with questionable soft tissue abnormality in right hilum. Axial CT shows large subcarinal calcified lymph nodes (HU: min 520, max 1371, mean 809).

Click Large calcified lymph node without AC artifact in an 85-year-old female with questionable soft tissue abnormality in right hilum. Scan was performed 60 minutes after injection of 12-16 mCi of FDG tracer, with the following parameters: 120 kVp, 300mAs, 5 mm slice thickness, and CT based attenuation correction algorithm using two iterations and 8 subsets. Axial AC PET shows no FDG activity in the area of large subcarinal calcified lymph nodes, as seen on axial CT (Image stack 8) and AC axial fused PET/CT images (Fig. 4b,c) (HU: min 520, max 1371, mean 809).