Acta physiologica (Oxford, England) · 2013
Early effects of an x-ray contrast medium on renal T(2) */T(2) MRI as compared to short-term hyperoxia, hypoxia and aortic occlusion in rats.
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Arakelyan K, Cantow K, Hentschel J, Flemming B, Pohlmann A, Ladwig M, Niendorf T, Seeliger E
Аннотация
AIM: 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 T2 * and T2 mapping. We studied CM effects on renal T2 */T2 and benchmarked them against short periods of hyperoxia, hypoxia and aortic occlusion (AO).
METHODS: Rats were equipped with carotid artery catheters (tip towards aorta) and supra-renal aortic occluders. T2 */T2 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 T2 */T2 mapping. For T2 */T2 assessment, regions of interest in the cortex (C), outer medulla (OM), inner medulla (IM) and papilla (P) were determined according to morphological features.
RESULTS: Hyperoxia increased T2 * in C (by 17%) and all medullary layers (25-35%). Hypoxia decreased T2 * in C (40%) and all medullary layers (55-60%). AO decreased T2 * in C (18%) and all medullary layers (30-40%). Upon injection of CM, T2 * increased transiently, then decreased, reaching values 10-20% below baseline in C and OM and 30-40% below baseline in IM and P.
CONCLUSION: T2 * mapping corroborates data previously obtained with invasive methods and demonstrates that CM injection affects renal medullary oxygenation. CM-induced T2 * decrease in OM was small vs. hypoxia and aortic occlusion. T2 * decrease obtained for hypoxia was more pronounced than for AO. This indicates that T2 * may not accurately reflect blood oxygenation under certain conditions.
METHODS: Rats were equipped with carotid artery catheters (tip towards aorta) and supra-renal aortic occluders. T2 */T2 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 T2 */T2 mapping. For T2 */T2 assessment, regions of interest in the cortex (C), outer medulla (OM), inner medulla (IM) and papilla (P) were determined according to morphological features.
RESULTS: Hyperoxia increased T2 * in C (by 17%) and all medullary layers (25-35%). Hypoxia decreased T2 * in C (40%) and all medullary layers (55-60%). AO decreased T2 * in C (18%) and all medullary layers (30-40%). Upon injection of CM, T2 * increased transiently, then decreased, reaching values 10-20% below baseline in C and OM and 30-40% below baseline in IM and P.
CONCLUSION: T2 * mapping corroborates data previously obtained with invasive methods and demonstrates that CM injection affects renal medullary oxygenation. CM-induced T2 * decrease in OM was small vs. hypoxia and aortic occlusion. T2 * decrease obtained for hypoxia was more pronounced than for AO. This indicates that T2 * may not accurately reflect blood oxygenation under certain conditions.