Influence of oxygen and carbogen breathing on renal oxygenation measured by T2*‐weighted imaging at 3.0 T

Abstract

The aim of the study was to assess the influence of carbogen (95% O(2), 5% CO(2)) or pure oxygen breathing on renal oxygenation measured by blood oxygenation level dependent (BOLD) magnetic resonance imaging at 3.0 T. Seven healthy young volunteers (median age 25, range 23-35 years) participated in the study. A T2*-weighted fat-saturated spoiled gradient-echo sequence was implemented on a 3.0 T whole-body imager (TE/TR = 27.9 ms/49 ms, excitation angle 20 degrees ) with an acquisition time of approximately 5.3 s. A total of 100 images were acquired during 22 min. A block design was applied for gas administration: 4 min room air, 4 min carbogen/oxygen, 4 min room air, 4 min carbogen/oxygen and 6 min room air. A compartment model was fitted to the data sets accounting for time-dependent increase/decrease of renal oxygenation as well as baseline changes of the scanner. T2*-weighted images showed good image quality without notable artefacts or distortions. Mean relative signal increase due to carbogen breathing was 2.73% (95% confidence interval: 1.34-5.54) in the right kidney and 3.76% (1.53-9.20) in the left kidney, while oxygen breathing led to a signal enhancement of 3.20% (2.57-3.98) in the right kidney and 3.16% (1.83-5.45) in the left kidney. No statistical difference was found between carbogen and oxygen breathing or between the oxygenation of the right and the left kidney. A significant difference was found in the characteristic time constant for the signal increase with a faster saturation taking place for oxygen breathing. Renal tissue oxygenation is clearly influenced by carbogen or oxygen breathing. The changes can be assessed by T2*-weighted MRI at high field strengths. The effects are in the expected range for the BOLD effect of 3-4% at 3.0 T. The proposed technique might be interesting for the assessment of renal tissue oxygenation and its regulation in patients with kidney diseases.

Blood oxygenation level‐dependent (BOLD) contrast magnetic resonance imaging (MRI) for prediction of breast cancer chemotherapy response: A pilot study

“…It is also independent of signal intensity. Increasingly, human studies are examining R with respect to tumor oxygenation, as shown for breast (34), prostate (35), head and neck tumors (36), and kidney (37). R has been reported in a group of 31 breast cancer patients undergoing neoadjuvant chemotherapy (38).…”

“…We observed signal increases within 2–4 minutes, but little decline was seen within 90 seconds of return to air breathing. Previous studies have reported quite rapid signal decreases in breast (23) and normal kidneys (37) upon return to air‐breathing, but those studies used active flowing air as well as oxygen, whereas we used passive air and active flowing oxygen only. Thus, the bore of the magnet likely remained flooded with oxygen for some time after oxygen flow was discontinued.…”

Simultaneous measurement of tissue oxygen level‐dependent (TOLD) and blood oxygenation level‐dependent (BOLD) effects in abdominal tissue oxygenation level studies

“…Using a Levenberg–Marquardt algorithm on a voxel‐by‐voxel basis, the measured signal intensities in each voxel can be fitted to a two‐parameter equation [2]. We report T 1 and rather than the reciprocal R 1 , to provide direct comparison with previous reports in the literature for tissue values .…”

Blood oxygenation level-dependent MRI for assessment of renal oxygenation

“…Although the data are not entirely consistent, most BOLD MRI studies in humans have demonstrated that breathing 100% oxygen increases intrarenal oxygenation in the medulla but not in the cortex, suggesting nonsaturation of renal medullary oxygenation under physiologic conditions. [13][14][15][16][17] Addition of a vasodilator gas exaggerates the medullary response but has a less consistent effect in the cortex. 13,15,16 In this regard, it is interesting to note that hyperbaric oxygen has been shown to exert a protective effect in an ischemia/reperfusion model in the rat.…”

“…[13][14][15][16][17] Addition of a vasodilator gas exaggerates the medullary response but has a less consistent effect in the cortex. 13,15,16 In this regard, it is interesting to note that hyperbaric oxygen has been shown to exert a protective effect in an ischemia/reperfusion model in the rat. 18 …”