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. 2019 Apr;81(4):2666-2675.
doi: 10.1002/mrm.27571. Epub 2018 Nov 19.

Noninvasive quantification of oxygen saturation in the portal and hepatic veins in healthy mice and those with colorectal liver metastases using QSM MRI

Eoin Finnerty  1 , Rajiv Ramasawmy  1 , James O'Callaghan  1 , John J Connell  1 , Mark Lythgoe  2 , Karin Shmueli  1 , David L Thomas  3 , Simon Walker-Samuel  4
Affiliations

Noninvasive quantification of oxygen saturation in the portal and hepatic veins in healthy mice and those with colorectal liver metastases using QSM MRI

Eoin Finnerty et al. Magn Reson Med. 2019 Apr.

Abstract

Purpose: This preclinical study investigated the use of QSM MRI to noninvasively measure venous oxygen saturation (SvO2) in the hepatic and portal veins.

Methods: QSM data were acquired from a cohort of healthy mice (n = 10) on a 9.4 Tesla MRI scanner under normoxic and hyperoxic conditions. Susceptibility was measured in the portal and hepatic veins and used to calculate SvO2 in each vessel under each condition. Blood was extracted from the inferior vena cava of 3 of the mice under each condition, and SvO2 was measured with a blood gas analyzer for comparison. QSM data were also acquired from a cohort of mice bearing liver tumors under normoxic conditions. Susceptibility was measured, and SvO2 calculated in the portal and hepatic veins and compared to the healthy mice. Statistical significance was assessed using a Wilcoxon matched-pairs signed rank test (normoxic vs. hyperoxic) or a Mann-Whitney test (healthy vs. tumor bearing).

Results: SvO2 calculated from QSM measurements in healthy mice under hyperoxia showed significant increases of 15% in the portal vein (P < 0.05) and 21% in the hepatic vein (P < 0.01) versus normoxia. These values agreed with inferior vena cava measurements from the blood gas analyzer (26% increase). SvO2 in the hepatic vein was significantly lower in the colorectal liver metastases cohort (30% ± 11%) than the healthy mice (53% ± 17%) (P < 0.05); differences in the portal vein were not significant.

Conclusion: QSM is a feasible tool for noninvasively measuring SvO2 in the liver and can detect differences due to increased oxygen consumption in livers bearing colorectal metastases.

Keywords: QSM; cancer; hepatic venous oxygen saturation; liver.

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Figures

Figure 1
Figure 1
T2*‐weighted magnitude images showing example ROIs. (A) Image showing large branch of HV (coronal orientation) including liver and stomach. (B) Image showing water reference in situ, including IVC (axial orientation), stomach, and liver tissue. (C) 3D rendering of magnitude image displaying PV and HV ROIs and water reference in situ. (D) Image showing large branches of PV (coronal orientation) including liver and stomach. Abbreviations: HV, hepatic vein; IVC, inferior vena cava; PV, portal vein; ROI, region of interest
Figure 2
Figure 2
Maximum intensity projections of processed QSM data from a 2.2 mm segment of a representative mouse liver under normoxic (left) and hyperoxic (right) conditions. Large branches of the HV are clearly visible in each image (red arrows). Vessels are brighter with respect to the liver tissue (by approximately 500 ppb) in the normoxic image compared with the hyperoxic image, indicating a more paramagnetic susceptibility
Figure 3
Figure 3
Change in venous oxygen saturation in (A) the PV (SpvO2) and (B) the HV (ShvO2). A statistically significant increase in oxygen saturation was measured in response to hyperoxia in both vessels (*P < 0.05, **P < 0.01).
Figure 4
Figure 4
The change in venous oxygen saturation in the HV from noninvasive measurements with QSM and invasive measurements from the IVC with a blood gas analyzer. There is good agreement between the 2 datasets
Figure 5
Figure 5
Measurements of venous blood oxygen saturation in mice with colorectal liver metastases and healthy mice. SvO2 values were calculated from susceptibility measurements in the PV (A) and the HV (B). Measurements in the HV of the mice with tumors contained significantly less oxygen than the healthy cohort
See this image and copyright information in PMC

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