Tumor Thrombus within the Superior Sagittal Sinus Detected on FDG PET Venography

A 60-year-old male, diagnosed with poorly differentiated squamous cell carcinoma of the distal esophagus, presented with diminution of vision in the left eye, 3 months after starting concurrent chemoradiotherapy. Diagnostic computed tomography (CT) venography was done which showed a filling defect in the superior sagittal venous sinus [thin yellow arrow, Figure 1a]. Fluorodeoxyglucose (FDG) positron emission tomography/CT (P) was done subsequently starting with a dynamic PET acquisition of the intracranial vessels immediately after 6.5 mCi of FDG injection (frame-mode acquisition for 2 min, 8 s/frame, reconstruction with Q. Clear algorithm at beta value 500). A filling defect was noticed in the superior sagittal venous sinus in the venous phase of early dynamic PET images [lateral projection of the maximum intensity projection image, bold yellow arrow, Figure 1b], corresponding to the defect in CT venography image. 'Whole body FDG PET/contrast enhanced CT acquisition at 60 min showed residual disease in the esophagus [small yellow arrows, Figure 2a-c] and an FDG avid enhancing lesion in the high parasagittal region of the parietal scalp infiltrating the superior sagittal sinus [green arrow, Figure 1d] without any bone erosions, suggesting possible spread of disease from the scalp into venous sinuous via the emissary veins in the skull. Elsewhere, an FDG-avid enhancing lesion was noted involving the left choroid [red arrows, Figure 2d and e], explaining the diminution of left eye vision with multiple new metastatic skeletal lesions [green arrows, Figure 2f and g].

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Figure 1: Filling defect in the superior sagittal venous sinus in in CT venography image [thin yellow arrow, a], on the the venous phase of early dynamic PET images [lateral projection of the MIP image, bold yellow arrow, b and fused PET/CT images, c]. FDG avid enhancing lesion in the high parasagittal region of the parietal scalp infiltrating the superior sagittal sinus [green arrow, d]

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Figure 2: Whole bodyPETMIPshowing residual disease in the esophagus [small yellowarrows, a-c], an FDG avidenhancinglesion in the left choroid [red arrows, d and e]withmultiplenewactiveskeletallesions [green arrows, f and g]

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Cancer patients are at about 5-fold increased risk of cerebral venous thrombosis (CVT), especially within the 1^st year of cancer diagnosis.[1] Early detection of CVT and appropriate treatment are important to avoid complications such as hemorrhage and hematoma formation.[2] Owing to its excellent spatial resolution and widespread availability, CT and magnetic resonance (MR) imaging angiography are now established modalities to study vasculature anatomy. However, there is a need for alternative angiography techniques in patients with contrast allergy and renal failure. The feasibility of early dynamic PET/CT angiographyin detecting stenosis of large arteries of the head neck/abdomen has previously been demonstrated by Drescher et al.[3] To our knowledge, our report here is the first instance of a CVT detection demonstrated on early dynamic FDG acquisition of the brain. We believe early dynamic PET imaging may be a clinically useful alternative to contrast CT/MR in detecting CVT, especially with next-generation PET scanners on the horizon with significantly improved sensitivity and spatial resolution.[4]