Effects of Carbidopa Premedication on 18F-FDOPA PET Imaging of Glioma: A Multiparametric Analysis

Abstract

Purpose: This study aimed to determine the impact of carbidopa premedication on static, dynamic and radiomics parameters of 18F-FDOPA PET in brain tumors. Methods: The study included 54 patients, 18 of whom received carbidopa, who underwent 18F-FDOPA PET for newly diagnosed gliomas. SUV-derived, 105 radiomics features and TTP dynamic parameters were extracted from volumes of interest in healthy brains and tumors. Simulation of the effects of carbidopa on time-activity curves were generated. Results: All static and TTP dynamic parameters were significantly higher 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). All parameters were no longer significantly modified by carbidopa premedication when using ratios to healthy brain. Simulated data confirmed that carbidopa leads to higher tumor TTP values, corrected by the ratios. Conclusion: In 18F-FDOPA PET, carbidopa induces similarly higher SUV and TTP dynamic parameters and similarly impacts SUV-dependent radiomics in healthy brain and tumor regions, which is compensated for by correcting for the tumor-to-healthy-brain ratio. This is a significant advantage for multicentric study harmonization.

Implementing the Point Spread Function Deconvolution for Better Molecular Characterization of Newly Diagnosed Gliomas: A Dynamic 18F-FDOPA PET Radiomics Study

“…To correct for the impact of Carbidopa on SUV measurements, static images were normalized by the SUV mean of a healthy brain to generate static tumor-to-background-ratio (TBR) parametric images [ 23 ]. Voxel/region-based TACs were fitted before being normalized to the fitted mean brain TAC [ 23 ] ( ).…”

“…To correct for the impact of Carbidopa on SUV measurements, static images were normalized by the SUV mean of a healthy brain to generate static tumor-to-background-ratio (TBR) parametric images [ 23 ]. Voxel/region-based TACs were fitted before being normalized to the fitted mean brain TAC [ 23 ] ( ). TTP values were computed as the time interval between the start of dynamic acquisition and the time the maximum uptake value was reached, and the voxel-based analysis enabled the construction of dynamic TTP parametric images [ 13 ].…”

Relevance of Dynamic 18F-DOPA PET Radiomics for Differentiation of High-Grade Glioma Progression from Treatment-Related Changes

“…To avoid amplifying noise from TACs of dynamic images, voxel TAC ratio was obtained by dividing the preliminary fitted voxel tumor TAC by the fitted mean brain TAC. These normalization methods were previously validated elsewhere [ 21 ]. Time-to-peak (TTP) values, which represent the time interval between tracer injection and the time point of the maximal TAC value, were extracted from each individual tumor at the voxel level to generate parametric TTP images.…”

Amino-acid PET as a prognostic tool after post Stupp protocol temozolomide therapy in high-grade glioma patients

“…Time-to-peak (TTP) and slope of uptake value between the 10th and the 30th minute post injection were calculated [12]. To correct for the impact of Carbidopa, static TBR parametric images and normalized region-based time activity curves were generated [14].…”