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Evaluation of intra-renal oxygenation during water diuresis: a time-resolved study using BOLD MRI.

ABSTRACT: Hypoxia of the renal medulla is a possible precursor to the onset of acute renal failure in humans and therefore an understanding of the factors influencing the oxygenation status within the renal medulla is very important. Blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) has been shown to non-invasively evaluate intra-renal oxygenation levels of the renal medulla in humans. A newly implemented three-dimensional (3-D) multiple gradient-recalled echo sequence, which permits examination of temporal responses to physiological or pharmacological stimuli, was used to monitor changes in intra-renal oxygenation status during water diuresis. Five healthy, young subjects (22+/-1.2 years) took part in the study. BOLD MRI data were acquired before and after water loading. Studies were repeated on a separate day after the subjects were pretreated with naproxen. Water diuresis significantly improved renal medullary oxygenation levels in all subjects (pre-waterload=30.3 1/s vs post-waterload 22.8 1/s); however, the temporal response was found to be subject dependent. In the presence of cyclooxygenase (COX) inhibition by naproxen, the improvement in oxygenation during water diuresis was completely abolished (pre-waterload=27.5 1/s vs post-waterload 28.5 1/s). Monitoring of temporal responses for the first time during water loading allowed for an appreciation of subject dependence. Comparison of the temporal response in terms of slopes demonstrated a significant difference between the waterload studies with and without naproxen (with naproxen=0.056 1/(s min) vs without naproxen=0.25 1/(s min)). The observed effects of naproxen were consistent with previous findings with COX inhibition.

SUBMITTER: Tumkur SM

PROVIDER: S-EPMC2919062 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:Computed tomography (CT) and spirometry are the current standard methods for assessing lung anatomy and pulmonary ventilation, respectively. However, CT provides limited ventilation information and spirometry only provides global measures of lung ventilation. Thus, a method that can enable simultaneous examination of lung anatomy and ventilation is of clinical interest. PURPOSE:To develop and test a 4D respiratory-resolved sparse lung MRI (XD-UTE: eXtra-Dimensional Ultrashort TE imaging) approach for simultaneous evaluation of lung anatomy and pulmonary ventilation. STUDY TYPE:Prospective. POPULATION:In all, 23 subjects (11 volunteers and 12 patients, mean age?=?63.6?±?8.4). FIELD STRENGTH/SEQUENCE:3T MR; a prototype 3D golden-angle radial UTE sequence, a Cartesian breath-hold volumetric-interpolated examination (BH-VIBE) sequence. ASSESSMENT:All subjects were scanned using the 3D golden-angle radial UTE sequence during normal breathing. Ten subjects underwent an additional scan during alternating normal and deep breathing. Respiratory-motion-resolved sparse reconstruction was performed for all the acquired data to generate dynamic normal-breathing or deep-breathing image series. For comparison, BH-VIBE was performed in 12 subjects. Lung images were visually scored by three experienced chest radiologists and were analyzed by two observers who segmented the left and right lung to derive ventilation parameters in comparison with spirometry. STATISTICAL TESTS:Nonparametric paired two-tailed Wilcoxon signed-rank test; intraclass correlation coefficient, Pearson correlation coefficient. RESULTS:XD-UTE achieved significantly improved image quality compared both with Cartesian BH-VIBE and radial reconstruction without motion compensation (P?<?0.05). The global ventilation parameters (a sum of the left and right lung measures) were in good correlation with spirometry in the same subjects (correlation coefficient?=?0.724). There were excellent correlations between the results obtained by two observers (intraclass correlation coefficient ranged from 0.8855-0.9995). DATA CONCLUSION:Simultaneous evaluation of lung anatomy and ventilation using XD-UTE is demonstrated, which have shown good potential for improved diagnosis and management of patients with heterogeneous lung diseases. LEVEL OF EVIDENCE:2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:411-422.

Project description:Purpose: Cold ischemia-reperfusion injury (CIRI) is one of the most serious complications following renal transplantation. The current study investigated the feasibility of Intravoxel Incoherent Motion (IVIM) imaging and blood oxygenation level-dependent (BOLD) in the evaluation of different degrees of renal cold ischemia-reperfusion injury in a rat model. Methods: Seventy five rats were randomly divided into three groups (N = 25 for each group): T0: sham-operated group, T2/T4: CIRI groups with different cold ischemia hours (2, 4 h, respectively). The rat model of CIRI group was established by left kidney cold ischemia with right nephrectomy. All the rats received a baseline MRI before the surgery. Five rats in each group were randomly selected to undergo an MRI examination at 1 h, day 1, day 2 and day 5 after CIRI. The IVIM and BOLD parameters were studied in the renal cortex (CO), the outer stripe of the outer medulla (OSOM), and the inner stripe of the outer medulla (ISOM) followed by histological analysis to examine Paller scores, peritubular capillary (PTC) density, apoptosis rate and biochemical indicators to obtain the contents of serum creatinine (Scr), blood urea nitrogen (BUN), superoxide dismutase (SOD) and malondialdehyde (MDA). Results: The D, D*, PF and T2* values in the CIRI groups were lower than those in the sham-operated group at all timepoints (all p < 0.05). The prolonged cold ischemia times resulted in gradually lower D, D*, PF and T2* values (all p < 0.05). The D and T2* values of cortex and OSOM in Group T0 and T2 returned to the baseline level (all p > 0.05) except Group T4. The D* and PF values of cortex, OSOM and ISOM in Group T2 and T4 still remained below the normal levels (all p < 0.05) except Group T0. D, D*, PF and T2* values were strongly correlated with histopathological (Paller scores, PTC density and apoptosis rate) and the biochemistry indicators (SOD and MDA) (|r|>0.6, p < 0.001). D*, PF and T2* values were moderately to poorly correlated with some biochemistry indicators (Scr and BUN) (|r|<0.5, p < 0.05). Conclusion: IVIM and BOLD can serve as noninvasive radiologic markers for monitoring different degrees of renal impairment and recovery after renal CIRI.

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Evaluation of intra-renal oxygenation during water diuresis: a time-resolved study using BOLD MRI.

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