Project 9: Detailing the relation between T2* and tissue pO2 with MR-PHYSIOL to enable unambiguous MR characterization of renal hemodynamics and oxygenation
Acute kidney injury (AKI) of various origins shares a common link in the pathophysiological chain of events: imbalance between renal medullary oxygen delivery and oxygen demand. Parametric MRI (T2*/T2 mapping) enables non-invasive monitoring of renal perfusion and oxygenation. For physiological interpretation of these quantitative MR parameters calibration using a multi-modality approach is essential. Hence, we focused on implementing integrated MRI and invasive techniques in a hybrid setup (MR-PHYSIOL) during the 1st funding period. Our MR-PHYSIOL studies provided new insight into the pathogenesis of renal ischemia/reperfusion injury (I/RI) induced AKI, but also generated novel fundamental questions regarding the relation between renal T2*/T2 and renal tissue/blood pO2. We found that alterations in tubular and vasculature volume fractions significantly influence renal T2*/T2. These must be differentiated from renal blood oxygenation level associated T2*/T2 changes before the diagnostic capabilities of parametric MRI can be translated from experimental research to improved clinical understanding of hemodynamics and oxygenation of AKI. We hypothesize that unraveling the relation between renal T2* versus tissue/blood pO2 levels enables unambiguous interpretation of MR measurements for characterization of renal hemodynamics and oxygenation under (patho)physiological conditions. Applying the MR-PHYSIOL setup, we will test our unifying hypothesis by combining MR based assessment of i) the renal vasculature’s volume fraction, ii) the tubules’ volume fraction, iii) renal perfusion, iv) renal blood oxygenation with v) invasive measurements of total renal blood flow, tissue oxygenation and perfusion, blood oxygenation and arterial pressure and with vi) (patho)physiologically relevant test procedures. To meet this goal, the project fosters novel technical MR developments in combination with new test procedures. Integrative characterization of renal hemodynamics and oxygenation will be done under physiological conditions and in rat AKI models other than I/RI, including i) a model of contrast media induced AKI (CI-AKI) and ii) a model of endotoxemic AKI.
*Dr. Hoff left the institution in Oktober 2016.