Non-invasive monitoring of renal oxygenation using BOLD-MRI: a reproducibility study

Abstract

Blood oxygenation level-dependent (BOLD) MRI was shown to allow non-invasive observation of renal oxygenation in humans. However, clinical applications of this type of functional MRI of the kidney are still limited, most likely because of difficulties in obtaining reproducible and reliable information. The aim of this study was to evaluate the reproducibility and robustness of a BOLD method applied to the kidneys and to identify systematic physiological changes potentially influencing the renal oxygenation of healthy volunteers. To measure the BOLD effect, a modified multi-echo data image combination (MEDIC) sequence was used to acquire 12 T2*-weighted images within a single breath-hold. Three identical measurements were performed on three axial and three coronal slices of right and left kidneys in 18 volunteers. The mean R2* (1/T2*) values determined in medulla and cortex showed no significant differences over three repetitions and low intra-subject coefficients of variation (CV) (3 and 4% in medulla and cortex, respectively). The average R2* values were higher in the medulla (16.15 +/- 0.11) than in the cortex (11.69 +/- 0.18) (P < 0.001). Only a minor influence of slice orientation was observed. Mean R2* values were slightly higher (3%) in the left than in the right kidney (P < 0.001). Differences between volunteers were identified (P < 0.001). Part of these differences was attributable to age-dependent R2* values, since these values increased with age when medulla (P < 0.001, r = 0.67) or cortex (P < 0.020, r = 0.42) were considered. Thus, BOLD measurements in the kidney are highly reproducible and robust. The results allow one to identify the known cortico-medullary gradient of oxygenation evidenced by the gradient of R2* values and suggest that medulla is more hypoxic in older than younger individuals. BOLD-MRI is therefore a useful tool to study sequentially and non-invasively regional oxygenation of human kidneys.

Towards the identification of multi-parametric quantitative MRI biomarkers in lupus nephritis

“…A recent study reported a wsCV of 18% and 25% for ASL and dynamic contrast-enhanced (DCE) RBF measurement respectively [27]. The estimated MRI parameters (ADC, T2*, RBF and T1rho) in healthy volunteers also match well with reported values in literature for each modality respectively (RBF: [27], T2*: [26], ADC: [22] and T1rho: [14]). In addition, pCASL RBF measurement was validated using global RBF by PC MRI.…”

“…The observed repeatability of the 4 qMRI techniques was comparable or slightly better than those reported in literature. For example, the reproducibility of R2* (1/T2*) measurement has been reported to be 3-12% by multiple studies [11,25,26]. A recent study reported a wsCV of 18% and 25% for ASL and dynamic contrast-enhanced (DCE) RBF measurement respectively [27].…”

Non-invasive investigation of kidney disease in type 1 diabetes by magnetic resonance imaging

“…Such approaches offer significant advantages in detecting pathological changes that may be regional or heterogeneous in their effects, and are forming the basis of our future studies. Renal T 2 * and BOLD contrast Although we could confirm the previously reported differences between the R 2 * of the cortex and medulla [17,19], we observed no change in renal R 2 * on physiological perturbation [21,34,35] as previously ascribed to changes in tissue oxygenation via BOLD contrast mechanisms [36]. Some earlier studies have employed hand-placed regions of interest to assess changes in R 2 * , typically using T 2 * or R 2 * maps to guide selection of ROI position.…”

Clinical Functional MRI of the kidneys

“…At the baseline, R Ã 2 values in the order of 12 s -1 and of 16 s -1 were reported at 1.5 T in the cortex and the medulla, respectively [32]. Numerous studies focused on the quantification of baseline renal relaxivity values under pathological conditions.…”

“…Hueper et al [18] Yu et al [15] Inci et al [14] Chandarana et al [16] Zhang et al [13] Lu et al [20] Sigmund et al [11] Wittsack et al [12] Rosenkrantz et al [54] Hueper et al [21] ASL Artz et al [26] Pedrosa et al [28] Lanzman et al [29] Rossi et al [27] Cutajar et al [23] Wu et al [24] Boss et al [22] Schor-Bardach et al [30] BOLD Park et al [37] Xiao et al [36] Min et al [38] Yin et al [34] Michaely et al [43] Xin-Long et al [33] Park et al [37] Donati et al [42] Simon-Zoula et al [32] Zhang et al…”