Effects of carbidopa premedication on 18F-FDOPA PET imaging of brain tumors: a static, dynamic and radiomics analysis

Purpose This study aims to determine the impact of carbidopa premedication on static, dynamic and radiomics parameters of 18F-FDOPA PET imaging in brain tumors. Material and Methods The study included 54 patients that underwent 18F-FDOPA PET imaging for newly diagnosed gliomas. Among these, 18 patients received 100 mg of carbidopa. SUV parameters and 105 radiomics features were extracted from the static images. Dynamic data were available for 41 patients. Time to Peak (TTP) values were extracted from dynamic acquisitions. These parameters were obtained from volumes of interest in healthy brain as well as tumors. Simulation of the effects of carbidopa premedication on TTP values were also generated. Results All static and TTP dynamic parameters were significantly increased in healthy brain regions of premedicated patients (ΔSUVmean = + 53%, ΔTTP = + 48%, p < 0.001). Furthermore, carbidopa impacted 81% of radiomics features, of which 92% correlated with SUVmean (absolute correlation coefficient ≥ 0.4). In tumors, premedication with carbidopa was an independent predictor of SUVmean (ΔSUVmean = + 52%, p < 0.001) and TTP (ΔTTP = + 24%, p = 0.025). Interestingly, all parameters were no longer significantly modified by carbidopa premedication when using tumor-to-healthy-brain image and TAC ratios. Simulated data confirmed that carbidopa leads to an increase in tumor TTP values which is corrected by using these ratios. Conclusion In 18F-FDOPA PET brain imaging, carbidopa induces an increase of similar magnitude in SUV, SUV-dependent radiomics and TTP dynamic parameters in healthy brain and tumor regions which are compensated for after using the tumor-to-healthy-brain image and TAC ratios which is an important point for multicentric studies harmonization.