Integrated software environment based on COMKAT for analyzing tracer pharmacokinetics with molecular imaging

77 Objectives To evaluate the role of high resolution quantitative PET/CT with MRI for early monitoring of treatment response to TNF-α inhibitor in human patients with rheumatoid arthritis (RA). Methods A PET/CT extremity scanner has been built at our institution. High resolution fused and co-registered PET/CT images of the wrist are obtained from this device. The patient lies prone on top of the PET/CT gantry, with the most symptomatic hand (locked by an immobilizer) suspended through a hole on the table-top. The hand immobilizer is compatible with MRI allowing the acquisition of clinical MR images at the same time points as extremity PET/CT. To date, three RA patients who were candidates for TNF-α blocker etanercept have been scanned with FDG-PET/CT and MRI at baseline and two at one month after initiation of treatment. This is a 10 patient study and recruitment is ongoing. Results For patient 1 (57f) at 1 month, marked reduction compared to baseline of 20-40% in maximum PET signal intensity (Imax) in the synovium and at sites of erosions, and of 82% in PET metabolic synovial volume was measured. MRI contrast enhancement correlated with this finding. This patient was hence classified as a responder to the drug. Rheumatologist examination at the end of three months confirmed this finding. For patient 2 (63f), an increase of 20-30% in Imax was measured in the synovium and at erosion sites at 1 month compared to baseline. We predict that this patient is a non-responder to the drug. Clinical examination for this patient is pending. Conclusions From initial studies, high resolution FDG-PET/CT with MRI shows significant promise for quantitative monitoring of early response to anti-TNF-α therapy in RA. Research Support This work was funded by the NIH grants UL1-RR024146, R01CA129561, R01EB002138, and the UC Davis Imaging Research Center