To evaluate the value of ⁶⁸Ga-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA)-fibroblast activating protein inhibitor (FAPI)-04 PET/CT on assessing different pathological grades in patients with renal fibrosis.

A total of 25 patients (11 males, 14 females; age (39.3±13.9) years) diagnosed with renal fibrosis in the Affiliated Hospital of Southwest Medical University from September 2020 to August 2021 were retrospectively analyzed. All patients underwent renal puncture examination and ⁶⁸Ga-DOTA-FAPI-04 PET/CT examination. The pathological results of kidney puncture were as the " gold standard" to divide the patients into mild fibrosis (Ⅰ), moderate fibrosis (Ⅱ), and severe fibrosis (Ⅲ). At the same time, 20 patients (10 males, 10 females; age (47.5±13.2) years) who underwent ⁶⁸Ga-DOTA-FAPI-04 PET/CT examination showed no abnormal uptake of radioactivity in bilateral kidneys and no history of urinary system related diseases were enrolled as normal controls. Parameters including the maximum standardized uptake value (SUV_max) of both kidneys, the mean standardized uptake value (SUV_mean) of the liver, target/background ratio (TBR), glomerular filtration rate (GFR), and serum creatinine (Scr) were collected. Kruskal-Wallis rank sum test and Bonferroni correction method were used to compare the differences of SUV_max, SUV_mean, TBR and Scr among groups. One-way analysis of variance and least significant difference (LSD) t test were used to compare the difference of GFR among groups. The receiver operating characteristic (ROC) curve analysis was used to analyze the diagnostic efficacy of SUV_max for the degree of renal fibrosis.

Of 25 patients, 22 had increased imaging agent uptake and the sensitivity of ⁶⁸Ga-DOTA-FAPI-04 PET/CT in diagnosing renal fibrosis was 88%. The SUV_max and TBR of patients with fibrosis grade Ⅰ, Ⅱ and Ⅲ were significantly higher than those of controls (SUV_max: 4.40(3.30, 4.50), 5.90(4.28, 6.48), 8.50(7.50, 9.73) and 1.44(1.38, 1.68); TBR: 6.340±2.389, 8.097±1.420, 11.343±2.002 and 2.986±0.645; H values: 33.685, 32.368, all adjusted P<0.05 (Bonferroni correction method)). The Scr of patients with fibrosis grade Ⅰ and Ⅲ were significantly different (70.1(55.4, 92.5) and 174.1(161.4, 498.2) μmol/L;H=9.770, adjusted P<0.05 (Bonferroni correction method)). The liver SUV_mean of patients with renal fibrosis grades Ⅱ and Ⅲ were significantly higher than that of controls (0.673±0.129, 0.751±0.170 and 0.514±0.142; H=15.609, both adjusted P<0.05 (Bonferroni correction method)). The GFR of patients with fibrosis grade Ⅲ had significant differences with grade Ⅰ and Ⅱ ((27.867±15.747), (87.756±31.657) and (63.160±29.556) ml/min;F=8.298, both P<0.05). ROC curve analysis showed that the area under curve was 0.946 7 (95%CI: 0.899 6-0.993 8, P<0.001).

⁶⁸Ga-DOTA-FAPI-04 PET/CT has a certain value in evaluating the degree of renal fibrosis, which can be used as a supplementary examination method for diagnosing renal fibrosis.

Fibrosis; Kidney; Positron-emission tomography; Tomography, X-ray computed; ⁶⁸Ga-FAPI