Hypoxia imaging with [18F]HX4 PET in NSCLC patients: Defining optimal imaging parameters☆

Background and purpose [18F]HX4 is a promising hypoxia PET-tracer. Uptake, spatio-temporal stability and optimal acquisition parameters for [18F]HX4 PET imaging were evaluated in non-small cell lung cancer (NSCLC) patients. Materials and methods [18F]HX4 PET/CT images of 15 NSCLC patients were acquired 2 h and 4 h after injection (p.i.). Maximum standardized-uptake-value (SUVmax), tumor-to-blood-ratio (TBRmax), hypoxic fraction (HF) and contrast-to-noise-ratio (CNR) were determined for all lesions. To evaluate spatio-temporal stability, DICE-similarity and Pearson correlation coefficients were calculated. Optimal acquisition-duration was assessed by comparing 30, 20, 10 and 5 min acquisitions. Results Considerable uptake (TBR >1.4) was observed in 18/25 target lesions. TBRmax increased significantly from 2 h (1.6 ± 0.3) to 4 h p.i. (2.0 ± 0.6). Uptake patterns at 2 h and 4 h p.i. showed a strong correlation (R = 0.77 ± 0.10) with a DICE similarity coefficient of 0.69 ± 0.08 for the 30% highest uptake volume. Reducing acquisition-time resulted in significant changes in SUVmax and CNR. TBRmax and HF were only affected for scan-times of 5 min. Conclusions The majority of NSCLC lesions showed considerable [18F]HX4 uptake. The heterogeneous uptake pattern was stable between 2 h and 4 h p.i. [18F]HX4 PET imaging at 4 h p.i. is superior to 2 h p.i. to reach highest contrast. Acquisition time may be reduced to 10 min without significant effects on TBRmax and HF