Korean J Radiol.  2015 Aug;16(4):827-834. 10.3348/kjr.2015.16.4.827.

Evaluation of Renal Oxygenation Level Changes after Water Loading Using Susceptibility-Weighted Imaging and T2* Mapping

• Ding J
• Xing W
• Wu D
• Chen J
• Pan L
• Sun J
• Xing S
• Dai Y

• KMID: 2155556
• DOI: http://doi.org/10.3348/kjr.2015.16.4.827

Abstract

OBJECTIVE
To assess the feasibility of susceptibility-weighted imaging (SWI) while monitoring changes in renal oxygenation level after water loading.
MATERIALS AND METHODS
Thirty-two volunteers (age, 28.0 +/- 2.2 years) were enrolled in this study. SWI and multi-echo gradient echo sequence-based T2* mapping were used to cover the kidney before and after water loading. Cortical and medullary parameters were measured using small regions of interest, and their relative changes due to water loading were calculated based on baseline and post-water loading data. An intraclass correlation coefficient analysis was used to assess inter-observer reliability of each parameter. A receiver operating characteristic curve analysis was conducted to compare the performance of the two methods for detecting renal oxygenation changes due to water loading.
RESULTS
Both medullary phase and medullary T2* values increased after water loading (p < 0.001), although poor correlations were found between the phase changes and the T2* changes (p > 0.05). Interobserver reliability was excellent for the T2* values, good for SWI cortical phase values, and moderate for the SWI medullary phase values. The area under receiver operating characteristic curve of the SWI medullary phase values was 0.85 and was not different from the medullary T2* value (0.84).
CONCLUSION
Susceptibility-weighted imaging enabled monitoring changes in the oxygenation level in the medulla after water loading, and may allow comparable feasibility to detect renal oxygenation level changes due to water loading compared with that of T2* mapping.

Keyword

Magnetic resonance imaging; Blood oxygen level dependent; Susceptibility-weighted imaging; Phase; T2*; Renal oxygenation level

MeSH Terms

Adult
Female
Humans
Kidney/*metabolism
Magnetic Resonance Imaging/*methods
Male
Oxygen/blood/*metabolism
ROC Curve
Reproducibility of Results
Water/*administration & dosage
Young Adult
Oxygen
Water

Figure

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  Fig. 1 Drawing of regions of interest (ROIs) in renal parenchyma. 30-year-old male volunteer underwent transverse susceptibility-weighted imaging and T2* mapping before water loading. One cortical ROI and one medullary ROI were drawn in each segment on magnitude image and were applied to phase image and T2* map to measure parameters in cortex and medulla, respectively.

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  Fig. 2 Distinct change in trend of quantitative parameter measurements appeared in renal medulla after water loading. Very few changes in phase and T2* values occurred in renal cortex, whereas medullary values increased for most of subjects after water loading.

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  Fig. 3 Correlations between phase changes and T2* changes due to water loading. Poor correlations were present between phase changes and T2* changes (all p > 0.05).

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  Fig. 4 Receiver operating characteristics curve analysis of two methods for detecting changes in renal oxygenation levels due to water loading. Area under receiver operating characteristic curve (AUC) was not significantly larger for medullary phase (φmedulla), as measured using susceptibility weighted imaging, than medullary T2* values (T2*medulla) using T2* map.

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