Quantifying hepatic functional reserve in rats via dynamic PET imaging using [68Ga]-NOTA-LSA

Preoperative evaluation of hepatic functional reserve determines the safe extent in liver resection. Existing methods assess only the global reserve rather than the local distribution. This work aims to quantify the regional hepatic functional reserve in vivo. We used [68Ga]-NOTA-LSA PET/CT to image nine rats, two with cirrhosis. Each rat underwent a 20-min dynamic PET scan. Data were modelled by a two-compartment model with a hepatic dual-input function. Based on the model, we calculated the distribution volume (DV) of [68Ga]-NOTA-LSA in the liver via two approaches (denoted DV1 and DV2). For comparison, we also calculated the static PET metric standard uptake value (SUV). Using DV and SUV maps, we calculated functional liver ratio (FLR). The results of DV maps show local heterogeneity of the liver. Significant difference between normal and liver-impaired rats can be seen both in DV1 and DV2, but not in SUV. FLR, when obtained through the DV map, is negatively correlated with three test indices of the liver function, i.e., alanine transferase (ALT), aspartate transaminase (AST) and Lactate dehydrogenase (LDH) levels. Specifically, FLR obtained using DV2 shows stronger negative correlation (rALT =-0.932;rAST =-0.914;rLDI1=-0.907, all with p<0.01) than that obtained using DV1 (rALT =-0.924;rAST =-0.905;rLDH=-0.901, all with p<0.01). No correlation is found in FLR if it is calculated using SUV. In conclusions, Dynamic PET with [68Ga]-NOTA-LSA evaluates the regional hepatic functional reserve, and enables differentiation between normal and impaired livers. However, SUV, the static [68Ga]-NOTA-LSA uptake, alone does not.