Abstract 11328: Non-invasive Evaluation of Regional Kidney Oxygen Tension (PO2) with Circulating Perfluorocarbon (PFC) Nanoparticles (NP) and 19F MRI
Atherosclerotic kidney disease is an important cause of hypertension and renal dysfunction. The renal medulla is highly susceptible to hypoxic injury due to the non-uniform blood flow distribution (cortex vs medulla: 80% vs 20%). Thus we sought to develop a non-invasive method for regional quantification of kidney PO2 capable of reporting the severity of renal hypoxia, with the use of high resolution MRI of PFC NP reporter that directly reflects PO2 based on its unique 19F T1 signal, which varies linearly with PO2. Swiss Webster mice were anesthetized with isofluorane, ventilated with either room air or 100% O2, followed by IV injection of 40% v/v perfluoro-crown-ether (CE) NP (5ml/kg). T1-weighted 1H images of mice kidneys were acquired at 4.7 T to visualize anatomy. A respiration-gated saturation recovery fast spin echo sequence was used for 19F imaging and T1 measurements. The 19F T1 readouts from PFC NP were calibrated against PO2 ex vivo (PO2 = (1/T1-0.366)/0.0023 mmHg), which allowed measurement of the average PO2 for the whole kidney, and regional PO2 of the cortex and medulla. The cortex and medulla were clearly visualized in 1H images (Fig. A). High resolution (0.39*0.78*2 mm3) 19F image (Fig. B) acquired in 20 mins exhibited sufficient SNR (>6) to depict regional anatomy from the circulating PFC NP. PO2 mapping under both normoxia and hyperoxia are shown in Fig. C & D. The measured PO2 in the whole kidney was 224 ± 52 mmHg on 100% O2, significantly higher than 69 ± 18 mmHg on room air (p<0.05). Under hyperoxia, the expected intrarenal PO2 gradient was observed from the well-oxygenated cortex (306 ± 73 mmHg) to the less-oxygenated medulla (180 ± 43 mmHg) (p<0.05). Regional difference in renal PO2 in response to hyperoxic challenge can be measured with 19F MRI of PFC NP. This PO2 responsive contrast approach suggests a new methodology for evaluating oxygen delivery in ischemic nephropathy and likely in other tissues where quantification of perfusion and oxygen delivery is required.
- © 2011 by American Heart Association, Inc.