18F-FSPG PET images, in comparison with MRI and 18F-FDG PET images of the three patients with lung cancer metastases to the brain.

For each subject, the whole-body Maximum Intensity Projection (MIP) image of the 18F-FSPG PET scan is shown on the left. In the right column, the axial images through the level of the brain metastasis include the post-contrast T1 MRI (top), 18F-FSPG PET (middle), and 18F-FDG PET (bottom). Physiologic distribution to normal organs are highlighted on the MIP image for subject A, including the liver (l), pancreas (p), kidneys (k), and bladder (b). For the first two subjects (A, B), the small lesions (below 1.5 cm) are clearly visible on MRI and with 18F-FSPG (SUV-A: 11.0, SUV-B: 4.7). With 18F-FDG, however, there is no discernible activity in these lesions. The larger lesion for subject C, who had previously been treated in this region, is again clearly discernable with MRI although the etiology of the enhancement was unclear whether representing residual/recurrent disease versus post-therapy changes. Both the 18F-FDG (SUV 10.1) and 18F-FSPG PET (SUV 21.8) are positive for this subject, but the accumulation of the latter is stronger, and further enhanced by the lack of uptake in the surrounding normal brain tissue (FDG SUV 4.8, FSPG SUV 0.1).