Using BOLD Imaging to Measure Renal Oxygenation Dynamics in Rats Injected with Diuretics

Kusakabe, Yoshinori; Matsushita, Taro; Honda, Saori; Okada, S.; Murase, Kenya

doi:10.2463/mrms.9.187

Cited by 13 publications

(9 citation statements)

References 22 publications

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“…A functional difference between the renal medullary and cortical regions has recently been demonstrated using BOLD (16,26,27). After the application of furosemide, the renal medulla was shown to take up larger amounts of oxygen than the cortex, resulting in a stronger T 2 *-response.…”

Section: Discussionmentioning

confidence: 99%

Quantitative BOLD response of the renal medulla to hyperoxic challenge at 1.5 T and 3.0 T

et al. 2012

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The aim of this study was to gage the magnitude of changes of the apparent renal medullary transverse relaxation time (ΔT(2)) induced by inhalation of pure oxygen (O(2) ) or carbogen (95% O(2) , 5% CO(2) ) versus baseline breathing of room air. Eight healthy volunteers underwent 2D multi-gradient echo MR imaging at 1.5 T and 3.0 T. Parametrical T(2) relaxation time maps were computed and average T(2) was measured in regions of interest placed in the renal medulla and cortex. The largest T(2) changes were measured in the renal medulla, with a relative ∆T(2) of 33.8 ± 22.0% (right medulla) and 34.7 ± 17.6% (left medulla) as compared to room air for oxygen breathing (p > 0.01), and 53.8 ± 23.9% and 53.5 ± 33.9% (p < 0.01) for carbogen breathing, respectively at 3 T. At 1.5 T, the corresponding values were 13.7 ± 18.5% and 24.1 ± 17.1% (p < 0.01) for oxygen breathing and 23.9 ± 17.2% and 38.9 ± 37.6% (p < 0.01) for carbogen breathing. As a result, we showed that renal medullary T(2) times responded strongly to inhalation of hyperoxic gases, which may be attributed to the hypoxic condition of the medulla and subsequent reduction in deoxyhemoglobin.

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Section: Discussionmentioning

confidence: 99%

Quantitative BOLD response of the renal medulla to hyperoxic challenge at 1.5 T and 3.0 T

et al. 2012

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“…In dogs, Thurau et al showed that renal oxygenation improved upon administration of a thiazide [30]. In animals, acetazolamide, a proximal diuretic, has been shown to increase cortical oxygenation and to reduce medullary oxygenation [38]. In patients chronically treated with furosemide a blunted response to the acute dose of furosemide has been reported [32].…”

Section: Discussionmentioning

confidence: 95%

Comparative Effect of a Renin Inhibitor and a Thiazide Diuretic on Renal Tissue Oxygenation in Hypertensive Patients

Vakilzadeh

Muller

Forni

et al. 2015

Kidney Blood Press Res

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Background/Aims: The purpose of the present study was to compare the direct renin inhibitor aliskiren to the diuretic hydrochlorothiazide (HCTZ) in their ability to modulate renal tissue oxygenation in hypertensive patients. Methods: 24 patients were enrolled in this randomized prospective study and 20 completed the protocol. Patients were randomly assigned to receive either aliskiren 150-300 mg/d or HCTZ 12.5 - 25 mg/d for 8 weeks. Renal oxygenation was measured by BOLD-MRI at weeks 0 and 8. BOLD-MRI was also performed before and after an i.v. injection of 20 mg furosemide at week 0 and at week 8. BOLD-MRI data were analyzed by measuring the oxygenation in 12 computed layers of the kidney enabling to asses renal oxygenation according to the depth within the kidney and by the classical method of regions of interest (ROI). Results: The classical ROI analysis of the data showed no difference between the groups at week 8. The analysis of renal oxygenation according to the 12 layers method shows no significant difference between aliskiren and HCTZ at week 8 before administration of furosemide. However, within group analyses show that aliskiren slightly but not significantly increased oxygenation in the cortex and decreased medullary oxygenation whereas HCTZ induced a significant overall decrease in renal tissue oxygenation. With the same method of analysis we observed that the response to furosemide was unchanged in the HCTZ group at week 8 but was characterized by an increase in both cortical and medullary oxygenation in aliskiren-treated patients. Patients responding to aliskiren and HCTZ by a fall in systolic blood pressure of >10 mmHg improved their renal tissue oxygenation when compared to non-responders. Conclusion: With the classical method of evaluation using regions no difference were found between aliskiren and HCTZ on renal tissue oxygenation after 8 weeks. In contrast, with our new method that takes into account the entire kidney, within group analyses show that aliskiren slightly increases cortical and medullary renal tissue oxygenation in hypertensive patients whereas HCTZ decreases significantly renal oxygenation at trough.

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“…This observation was consistent and highly reproducible in repeated studies. The functional difference between renal medullary and cortical regions has recently been demonstrated using BOLD . The hypoxic state of the medulla is caused by: (i) low oxygen delivery as a result of low vascular density in the medulla and arterial–venous shunting; and (ii) high oxygen consumption for active transcellular transport of sodium and chloride…”

Section: Discussionmentioning

confidence: 99%

Evaluation of renal oxygenation change under the influence of carbogen breathing using a dynamic R₂, R₂′ and R₂* quantification approach

et al. 2016

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The purpose of this study is to demonstrate the feasibility of dynamic renal R /R '/R * measurements based on a method, denoted psMASE-ME, in which a periodic 180° pulse-shifting multi-echo asymmetric spin echo (psMASE) sequence, combined with a moving estimation (ME) strategy, is adopted. Following approval by the institutional animal care and use committee, a block design of respiratory challenge with interleaved air and carbogen (97% O , 3% CO ) breathing was employed in nine rabbits. Parametrical R /R '/R * maps were computed and average R /R '/R * values were measured in regions of interest in the renal medulla and cortex. Bland-Altman plots showed good agreement between the proposed method and reference standards of multi-echo spin echo and multi-echo gradient echo sequences. Renal R , R ' and R * decreased significantly from 16.2 ± 4.4 s , 9.8 ± 5.2 s and 25.9 ± 5.0 s to 14.9 ± 4.4 s (p < 0.05), 8.5 ± 4.1 s (p < 0.05) and 23.4 ± 4.8 s (p < 0.05) in the cortex when switching the gas mixture from room air to carbogen. In the renal medulla, R , R ' and R * also decreased significantly from 12.9 ± 4.7 s , 15.1 ± 5.8 s and 27.9 ± 5.3 s to 11.8 ± 4.5 s (p < 0.05), 14.2 ± 4.2 s (p < 0.05) and 25.8 ± 5.1 s (p < 0.05). No statistically significant differences in relative R , R ' and R * changes were observed between the cortex and medulla (p = 0.72 for R , p = 0.39 for R ' and p = 0.61 for R *). The psMASE-ME method for dynamic renal R /R '/R * measurements, together with the respiratory challenge, has potential use in the evaluation of renal oxygenation in many renal diseases.

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Using BOLD Imaging to Measure Renal Oxygenation Dynamics in Rats Injected with Diuretics

Cited by 13 publications

References 22 publications

Quantitative BOLD response of the renal medulla to hyperoxic challenge at 1.5 T and 3.0 T

Quantitative BOLD response of the renal medulla to hyperoxic challenge at 1.5 T and 3.0 T

Comparative Effect of a Renin Inhibitor and a Thiazide Diuretic on Renal Tissue Oxygenation in Hypertensive Patients

Evaluation of renal oxygenation change under the influence of carbogen breathing using a dynamic R₂, R₂′ and R₂* quantification approach

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Using BOLD Imaging to Measure Renal Oxygenation Dynamics in Rats Injected with Diuretics

Cited by 13 publications

References 22 publications

Quantitative BOLD response of the renal medulla to hyperoxic challenge at 1.5 T and 3.0 T

Quantitative BOLD response of the renal medulla to hyperoxic challenge at 1.5 T and 3.0 T

Comparative Effect of a Renin Inhibitor and a Thiazide Diuretic on Renal Tissue Oxygenation in Hypertensive Patients

Evaluation of renal oxygenation change under the influence of carbogen breathing using a dynamic R2, R2′ and R2* quantification approach

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Evaluation of renal oxygenation change under the influence of carbogen breathing using a dynamic R₂, R₂′ and R₂* quantification approach