Early effects of an x‐ray contrast medium on renal T2*/T2 MRI as compared to short‐term hyperoxia, hypoxia and aortic occlusion in rats. (12th April 2013)

• Record Type: Journal Article
• Authors: Arakelyan, K.; Cantow, K.; Hentschel, J.; Flemming, B.; Pohlmann, A.; Ladwig, M.; Niendorf, T.; Seeliger, E.
• Is Part Of: Acta physiologica. Volume 208:Number 2(2013:Jun.)
• Page Start: 202
• Page End: 213
• Publication Date: 2013-04-12
• Subjects: Physiology -- Periodicals; Physiology -- Research -- Periodicals; 612
• DOI: 10.1111/apha.12094
• Languages: English
• ISSNs: 1748-1708

Abstract

<abstract abstract-type="main" id="apha12094-abs-0001"> <title>Abstract</title> <sec id="apha12094-sec-0001" sec-type="section"> <title>Aim</title> <p>X‐ray contrast media (CM) can cause acute kidney injury (AKI). Medullary hypoxia is pivotal in CM‐induced AKI, as indicated by invasively and pin‐point measured tissue oxygenation. MRI provides spatially resolved blood oxygenation level–dependent data using T<sub>2</sub>* and T<sub>2</sub> mapping. We studied CM effects on renal T<sub>2</sub>*/T<sub>2</sub> and benchmarked them against short periods of hyperoxia, hypoxia and aortic occlusion (AO).</p> </sec> <sec id="apha12094-sec-0002" sec-type="section"> <title>Methods</title> <p>Rats were equipped with carotid artery catheters (tip towards aorta) and supra‐renal aortic occluders. T<sub>2</sub>*/T<sub>2</sub> mapping was performed using a 9.4‐T animal scanner. CM (1.5 mL iodixanol) was injected into the thoracic aorta with the animal in the scanner followed by 2 h of T<sub>2</sub>*/T<sub>2</sub> mapping. For T<sub>2</sub>*/T<sub>2</sub> assessment, regions of interest in the cortex (C), outer medulla (OM), inner medulla (IM) and papilla (P) were determined according to morphological features.</p> </sec> <sec id="apha12094-sec-0003" sec-type="section"> <title>Results</title> <p>Hyperoxia increased T<sub>2</sub>* in C (by 17%) and all medullary layers (25–35%). Hypoxia decreased T<sub>2</sub>* in C (40%) and all medullary layers (55–60%). AO decreased T<sub>2</sub>* in C (18%) and all medullary layers (30–40%). Upon injection of CM, T<sub>2</sub>* increased transiently, then decreased, reaching values 10–20% below baseline in C and OM and 30–40% below baseline in IM and P.</p> </sec> <sec id="apha12094-sec-0004" sec-type="section"> <title>Conclusion</title> <p>T<sub>2</sub>* mapping corroborates data previously obtained with invasive methods and demonstrates that CM injection affects renal medullary oxygenation. CM‐induced T<sub>2</sub>* decrease in OM was small vs. hypoxia and aortic occlusion. T<sub>2</sub>* decrease obtained for hypoxia was more pronounced than for AO. This indicates that T<sub>2</sub>* may not accurately reflect blood oxygenation under certain conditions.</p> </sec> </abstract>