Magnetic resonance imaging of spondyloarthritis: spine and SI joints

Standardized uptake value-based analysis of two-phase whole-body bone tomoscintigraphies recorded with a high-speed 360° CZT camera in patients with known or suspected inflammatory arthritis

PURPOSE

360° CZT-cameras provide whole-body bone SPECT/CT recordings at delayed (DEL) and blood-pool (BP) phases with short recording times but long visual analysis times. This study aims to determine whether a standardized uptake value (SUV)-based detection of inflammatory arthritis (IA) could facilitate this analysis.

METHODS

We included 72 patients with known or suspected IA who underwent two-phase whole-body bone SPECT/CT after 550-650 MBq [99mTc]Tc-HDP injection. Forty-eight patients also had ultrasound (US) for peripheral IA, and 42 had MRI for axial IA. The skeleton was segmented into 26 joint areas and analyzed by trained observers using a visual consensus methodology and SUVmax measurements.

RESULTS

A total of 1836 joint areas were analyzed, including 1126 peripheral ones (limb joints excluding hips and shoulders). SUVmax was predictive of visually abnormal SPECT joints with high areas under receiver-operating-characteristic (ROC) curves for non-peripheral (BP-SPECT: 0.941 ± 0.017, DEL-SPECT: 0.910 ± 0.014) and especially peripheral (BP-SPECT: 0.980 ± 0.005, DEL-SPECT: 0.939 ± 0.012) joints. An SUVmax threshold-based prediction of visual SPECT abnormalities had high negative predictive values (BP-SPECT: 99.2% (1479/1491), DEL-SPECT: 97.2% (1333/1372)) but low positive predictive values (BP-SPECT: 35.1% (121/345), DEL-SPECT: 51.2% (237/463)). MRI- and US-defined IA were best predicted by a visually abnormal BP-SPECT due to higher specificities than SUVmax thresholds (all p < 0.05).

CONCLUSION

On two-phase whole-body bone SPECT/CT, an SUVmax-based IA detection may not replace the conventional visual method. However, given the high negative predictive values provided by SUVmax thresholds, the time-consuming visual analysis of SPECT/CT slices could be confined to the small proportion of joints exceeding these thresholds.