Mapping hepatic blood oxygenation by quantitative BOLD (qBOLD) MRI

Abstract

Purpose Abnormalities in hepatic oxygen delivery and oxygen consumption may serve as a significant indicator of hepatic cellular dysfunction and may predict treatment response. However, conventional and oxygen‐enhanced hepatic BOLD MRI can only provide semiquantitative assessment of hepatic oxygenation. Methods A hepatic quantitative BOLD (qBOLD) model was proposed for noninvasive mapping of hepatic venous blood oxygen saturation (Yv) and deoxygenated blood volume (DBV) in human subjects. The validity and the estimation bias of the proposed model were evaluated by Monte Carlo simulations. Eight healthy subjects were scanned after written consent with institutional review board approval. Results Monte Carlo simulations demonstrated that the proposed single‐compartment hepatic qBOLD model leads to significant deviation of the predicted T2* decay profile from the simulated signal due to high hepatic blood volume fraction. Small relative estimation bias for hepatic Yv and significant overestimation for hepatic DBV were observed, which can be corrected by applying the calibration curves established from simulations. After correction, the mean hepatic Yv in human subjects was 56.8 ± 6.8%, and the mean hepatic DBV was 0.190 ± 0.035, consistent with measurements from other invasive approaches. Except in regions with significant vascular contamination, the maps for hepatic Yv and DBV were relatively homogenous. Conclusions With estimation bias correction, the hepatic qBOLD approach enables noninvasive mapping of hepatic blood volume and oxygenation in human subjects. The established protocol may be used to quantitatively assess hepatic tissue hypoxia in multiple liver diseases.

Differential requirements for mitochondrial electron transport chain components in the adult murine liver

“…Thus, increased tissue oxygen levels result in decreased T1 values. Similarly, the unpaired electrons of iron in deoxyhemoglobin allow it to act as a strong paramagnetic agent which accelerates the decay of transverse magnetization in the blood (characterized by the transverse relaxation time T2*), termed the BOLD (Blood-Oxygen-Level-Dependent) effect ( Wengler et al, 2019 ). In this manner, relative increases in T2* values are indicative of decreased deoxyhemoglobin concentration (i.e., an increased blood oxygenation state).…”

Quantitative perfusion mapping with induced transient hypoxia using BOLD MRI

“…It is also potentially easily translatable to clinical protocols, especially for perfusion quantification in patients under anesthesia. Apart from brain imaging, since previous work has demonstrated good performance of BOLD imaging and different respiratory challenges in the liver, kidney, and heart, [36][37][38][39] this dDSC technique can potentially be applied to assess in these organs where non-contrast imaging modalities, such as ASL, have proven less effective due to low signal-to-noise ratio. 40 Most importantly, this hypoxia gas paradigm is very safe and well-tolerated; our laboratory has performed this experiment on over 200 subjects in a larger study on sickle cell anemia without any major adverse events, such as stroke or transient ischemic attack.…”

“…It is also potentially easily translatable to clinical protocols, especially for perfusion quantification in patients under anesthesia. Apart from brain imaging, since previous work has demonstrated good performance of BOLD imaging and different respiratory challenges in the liver, kidney, and heart, 36‐39 this dDSC technique can potentially be applied to assess in these organs where non‐contrast imaging modalities, such as ASL, have proven less effective due to low signal‐to‐noise ratio 40 …”

Differential requirements for mitochondrial electron transport chain components in the adult murine liver

“…Based on arterial spin labeling (31), we did not observe changes in liver perfusion between the two genotypes (Figure 3F). BOLD (Blood-oxygen-level dependent) measurements (T2*) are dependent on the concentration of deoxyhemoglobin (32,33), and we observed significant increases in T2* in both ndufa9 f/f and ndufa9 -/animals, indicating increased blood oxygen in the setting of 100% O2 (Figure 3G). TOLD (Tissue-oxygen-level dependent) measurements (based on T1 relaxation) are dependent on the dissolved oxygen concentration; with increased tissue oxygen content, T1 parameters are expected to decrease (34).…”