Prognostic value of [18F]FAZA PET/MR imaging pre and post revascularization in chronic limb-threatening ischemia: a prospective pilot study on tissue microcirculation.

PURPOSE To evaluate the prognostic value of [18F]FAZA PET in predicting long-term clinical outcomes of critical limb-threatening ischemia (CLTI) patients undergoing endovascular revascularization. METHODS This prospective pilot study received IRB and ethics committee approval. Patients who were planned to undergo revascularization were recruited. All patients underwent both dynamic and static [18F]FAZA PET at two different time points, before and after revascularization. After modelling, dynamic [18F]FAZA PET-derived parameters (including K1, K2, K3, K4, Ki, and total volume distribution [VT]) were extracted from each scan, and delta parameters were calculated. Also, standardized uptake values were calculated from the static [18F]FAZA PET. Furthermore, ankle-brachial indices (ABIs) were measured before and after revascularization. Patients were followed up clinically. All major events were documented, and patients were classified into two groups accordingly: "sustained response" and "therapy failure". RESULTS From the 12 prospectively recruited patients (mean age = 69 years), five patients were diagnosed with therapy failure during follow-up. K1 (p = 0.012) and ABI (p = 0.006) were significantly different in the post-angioplasty setting versus pre-angioplasty evaluations, being significantly lower and higher, respectively. In patients who experienced sustained clinical response, K1 (p = 0.028; significantly lower after treatment), VT (p = 0.018; significantly higher after treatment), and ABI (p = 0.028; significantly higher after treatment) were significantly different after angioplasty versus before angioplasty. In patients with therapy failure, only VT (p = 0.043; significantly lower after treatment) was significantly different. Considering between-group differences, ΔVT was significantly different between those who experienced sustained response versus those with therapy failure (p = 0.003). CONCLUSION Our findings could support the potential prognostic value of changes in dynamic [18F]FAZA's initial volume distribution in the pre- versus post-revascularization setting. Unlike traditional measures, such as ABI, which show tissue's macrovasculature patency, dynamic [18F]FAZA PET could capture tissue-level microcirculation by VT mapping.