Abstract
Simple SummaryThis paper aims to improve the knowledge regarding 18F-FDOPA PET/CT parameters that may influence both the interpretation of PET data and the management of primary brain tumors. The evaluation of volumetric parameters in 18F-FDOPA imaging is uncommon, and we aim to increase the scientific interest on the potential role of volumetric parameters in the clinical practice. The standardized uptake value (SUV)-derived indices as SUV max, SUV mean, SUV max ratio, and SUV mean ratio are widely used but the exact methodology to elaborate SUV ratio is not well established. Therefore, this study aims to assess the correlation between SUV-derived indices and volumetric uptake parameters.Novel parameters in PET imaging, such as volumetric parameters, are gaining interest in the scientific literature, but the role of dopaminergic tumor volume (DTV) and total lesion F-DOPA activity (TLDA) and the correlation between volumetric and SUV-derived parameters are not well defined yet. One hundred and thirty-three patients that underwent 18F-FDOPA imaging for primary brain tumors were included in this retrospective study. SUV-derived indices were calculated (the occipital region was chosen to generate ratios of tumor SUV) and compared with volumetric parameters. Regression models were applied in univariate analysis and lnSUVmax was positively associated with lnDTV (beta 0.42, p = 0.007), the lnSUVmax ratio was positively associated with lnDTV (beta 0.80, p = 0.011), lnSUVmax was positively associated with lnTLDA (beta 1.27, p < 0.0001), and the lnSUVmax ratio was positively associated with lnTLDA (beta 1.87, p < 0.0001). Our study demonstrates that volumetric uptake parameters in 18F-FDOPA PET/CT are easier to assess in primary brain tumors with higher SUV max and SUV max ratios, and supports the emerging role of volumetric parameters in the data interpretation.
Highlights
The subjects included in the retrospective analysis were adult (≥18 years old), had a diagnosis of primary brain tumor, and were willing to participate in an eventual future retrospective study
The lnSUVmax ratio was positively associated with lnTLDA; the model explained 24.6% of the variance in lnDTV (Rsquare 0.246, STED 1.14)
We aim to focus on the methodology concerning the calculation of standardized uptake value (SUV) max ratio, based on previous studies of our research group [8,11,12] in which the occipital region was chosen for SUV max calculation for the background (SUVmax occ), instead of using an ROI positioned on the semi-oval center of the unaffected contralateral hemisphere, as reported in other papers [23]
Summary
F-fluoro-l-phenylalanine (18 F-FDOPA) is one of the most used imaging techniques in the management of primary brain tumors, especially for tumor grading, delineation of tumor extension, treatment planning, treatment response, and post-treatment surveillance [1]. This radiopharmaceutical is a catecholaminergic precursor, and it enters the cell through. L-type amino acid transporter 1 and 2 (LAT1 and LAT2), which are overexpressed in tumor cells [2]. 18F-FDOPA is decarboxylated by aromatic l-amino acid decarboxylase with the formation of 18F-dopamine, and is transported into vesicles [3]; the increased protein synthesis induces a high radiopharmaceutical uptake in tumor cells.
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