A Comparative Study of F-FAPI-42 and F-FDG PET/CT for Evaluating Acute Kidney Injury in Cancer Patients.

Purpose: Compare the value of imaging using positron F-labeled fibroblast activation protein inhibitor-42 (F-FAPI-42) and F-labeled deoxyglucose (F-FDG) for assessment of AKI.

Procedures: This study analyzed cancer patients who received F-FAPI-42 and F-FDG PET/CT imaging. Eight patients had AKI with bilateral ureteral obstruction (BUO), eight had BUO (CKD1-2) with no acute kidney disease (AKD), and eight had no ureteral obstruction (UO) with normal renal function. The average standardized uptake value (SUV) of the renal parenchyma (RP-SUV), the blood pool SUV (B- SUV), SUV in the highest region of the renal collective system (RCS-SUV), and the highest serum creatinine level (top SCr) were recorded.

Results: The F-FAPI-42 and F-FDG results showed that radiotracer of renal parenchyma was more concentrated in the AKI group than in the other two groups, whereas the RP-SUV from F-FAPI-42 was higher than that from F-FDG in the AKI group (all P < 0.05). F-FAPI-42 imaging in the AKI group showed uptake by the renal parenchyma with a diffuse increase, but very little radiotracer in the renal collecting system, similar to a "super kidney scan." The renal parenchyma also had an increase of SUV, with accumulation of radiotracer in the renal collecting system. AKI was more severe when a patient had a "super kidney scan" in both kidneys (P < 0.05). The B-SUV level was higher in the AKI group than in the other two groups in F-FAPI-42 (both P < 0.05).

Conclusions: F-FAPI-42 imaging had higher RP-SUV than F-FDG imaging in cancer patients who had BUO with AKI. An increased renal parenchyma uptake in both kidneys and low radiotracer distribution in the collecting system suggest more severe AKI.