Use of positron emission tomography with methyl‐11C‐choline and 2‐18F‐fluoro‐2‐deoxy‐D‐glucose in comparison with magnetic resonance imaging for the assessment of inflammatory proliferation of synovium

Objective

To compare positron emission tomography (PET) and magnetic resonance imaging (MRI) in the evaluation of inflammatory proliferation of synovium.

Methods

Ten patients (mean ± SD age 36 ± 13 years) with inflammatory joint disease and with clinical signs of inflammation of the joint were studied. A new tracer for cellular proliferation, methyl‐¹¹C‐choline (¹¹C‐choline), and a widely used tracer for the detection of inflammation and cancer, 2‐¹⁸F‐fluoro‐2‐deoxy‐D ‐glucose (¹⁸F‐FDG), were applied for PET imaging, and the results were compared with the findings from gadolinium diethylenetriaminepentaacetic acid–enhanced MR images. The uptake of ¹¹C‐choline and ¹⁸F‐FDG in the inflamed synovium was measured and expressed as the standardized uptake value (SUV) and the kinetic influx constant (K_i) obtained from graphic analysis, and these values were compared with quantitative values on MRI. Synovial volumes were measured on the coronal contrast‐enhanced T1‐weighted MR images using the standard software of the MR imager.

Results

All patients showed high accumulation of both ¹¹C‐choline and ¹⁸F‐FDG at the site of arthritic changes, where quantification of the tracer uptake was performed. The SUV of ¹¹C‐choline was 1.5 ± 0.9 gm/ml (mean ± SD; n = 10) and the SUV of ¹⁸F‐FDG was 1.9 ± 0.9 gm/ml (n = 10) (P = 0.017). The K_i of ¹¹C‐choline (mean ± SD 0.048 ± 0.042 minute⁻¹) was 8‐fold higher than the K_i of ¹⁸F‐FDG (0.006 ± 0.003 minute⁻¹) (P = 0.009). Both the uptake of ¹¹C‐choline and the uptake of ¹⁸F‐FDG correlated highly with the volume of synovium; the highest correlation was observed with the K_i of ¹¹C‐choline (r = 0.954, P < 0.0001).

Conclusion

In the use of PET scans,¹¹C‐choline can be regarded as a promising tracer for quantitative imaging of proliferative arthritis changes. Nevertheless, subsequent prospective studies with larger numbers of patients are necessary to further characterize the relationship between the findings on PET imaging and the clinical and functional measures of inflammation.