The feasibility of quantitative assessment of dynamic ¹⁸F-fluorodeoxyglucose PET in Takayasu's arteritis: a pilot...

PET has been demonstrated to be sensitive for detecting active inflammation in Takayasu's arteritis (TAK) patients, but semi-quantitative-based assessment may be susceptible to various biological and technical factors. Absolute quantification via dynamic PET (dPET) may provide a more reliable and quantitative assessment of TAK-active arteries. The purpose of this study was to investigate the feasibility and efficacy of dPET in quantifying TAK-active arteries compared to static PET.

This prospective study enrolled 10 TAK-active patients (fulfilled the NIH criteria) and 5 control participants from March to October 2022. One-hour dPET scan (all TAK and control participants) and delayed static PET scan at 2-h (all TAK patients) were acquired. For 1-h static PET, summed images from 50 to 60 min of the dPET were extracted. PET parameters derived from 1- and 2-h static PET including SUV (SUV_1H and SUV_2H), target-to-background ratio (TBR) (TBR_1H and TBR_2H), net influx rate (K_i), and TBR_Ki extracted from dPET were obtained. The detectability of TAK-active arteries was compared among different scanning methods using the generalized estimating equation (GEE) with a logistic regression with repeated measures, and the GEE with gamma distribution and log link function was used to evaluate the different study groups or scanning methods.

Based on the disease states, 5 cases of TAK were classified as untreated and relapsed, respectively. The SUV_max on 2-h PET was higher than that on 1-h PET in the untreated patients (P < 0.05). However, no significant differences were observed in the median SUV_max between 1-h PET and 2-h PET in the relapsed patients (P > 0.05). The TBR_Ki was significantly higher than both TBR_1H and TBR_2H (all P < 0.001). Moreover, the detectability of TAK-active arteries by dPET-derived K_i was significantly higher than 1-h and 2-h PET (all P < 0.001). Significant differences were observed in K_imax, SUV_max-1H, TBR_1H, and TBR_Ki among untreated, relapsed, and control groups (all P < 0.05).

Absolute quantitative assessment by dPET provides an improved sensitivity and detectability in both visualization and quantification of TAK-active arteries. This elucidates the clinical significance of dPET in the early detection of active inflammation and monitoring recurrence.