Non-invasive measurement of hepatic venous oxygen saturation (ShvO2) with quantitative susceptibility mapping in normal mouse liver and livers bearing colorectal metastases

PurposeThe purpose of this prospective study was to investigate the potential of QSM to non-invasively measure hepatic venous oxygen saturation (ShvO2).Materials & MethodsAll animal studies were performed in accordance with the UK Home Office Animals Science Procedures Act (1986) and UK National Cancer Research Institute (NCRI) guidelines. QSM data was acquired from a cohort of mice (n=10) under both normoxic (medical air, 21% O2/ balance N), and hyperoxic conditions (100% O2). Susceptibility measurements were taken from large branches of the portal and hepatic vein under each condition and were used to calculate venous oxygen saturation in each vessel. Blood was extracted from the IVC of three mice under norm- and hyperoxic conditions, and oxygen saturation was measured using a blood gas analyser to act as a gold standard. QSM data was also acquired from a cohort of mice bearing colorectal liver metastases (CRLM). SvO2was calculated from susceptibility measurements made in the portal and hepatic veins, and compared to the healthy animals.ResultsSvO2calculated from QSM measurements showed a significant increase of 14.93% in the portal vein (p < 0.05), and an increase of 21.39% in the hepatic vein (p < 0.01). Calculated results showed excellent agreement with those from the blood gas analyser (26.14% increase). ShvO2was significantly lower in the disease cohort (30.18 ± 11.6%), than the healthy animals (52.67 ± 17.8%) (p < 0.05), but differences in the portal vein were not significant.ConclusionQSM is a feasible tool for non-invasively measuring hepatic venous oxygen saturation and can detect differences in oxygen consumption in livers bearing colorectal metastases.