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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 - Korean J Radiol (2015)

Bottom Line: 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).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).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.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Third Affiliated Hospital of Suzhou University, Changzhou, Jiangsu 213003, China.

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.

No MeSH data available.


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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Figure 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.

Mentions: First, the pre- and post-water loading mGRE and SWI datasets were co-registered on an extended workstation (EWS, Philips Healthcare) to avoid mismatched artifacts resulting from different positions of the kidney image during breath holds. Then, the phase datasets were exported to SPIN for correction processing (presented in the last section) and subsequent analysis. Second, to ensure that each region of interest (ROI) fell within identifiable medullary and cortical sections, one plane through the renal hilum of each kidney was used for the image analysis at the point where the optimal contrast between the cortex and medulla was observed. The kidney ROI was divided into three segments; one cortical ROI and one medullary ROI were drawn in each segment (6-10 pixels within each ROI) and transferred to phase images and T2* maps to measure the parameters (Fig. 1). The mean phase (φcortex and φmedulla), and mean T2* (T2*cortex and T2*medulla) values were calculated by averaging the cortical and medullary ROIs, respectively, measured by the two radiologists. The relative changes (RC) in the mean phase and T2* values after water loading were calculated using the following equations. (2),RCp=Δφφ0×100%


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 - Korean J Radiol (2015)

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.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4499547&req=5

Figure 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.
Mentions: First, the pre- and post-water loading mGRE and SWI datasets were co-registered on an extended workstation (EWS, Philips Healthcare) to avoid mismatched artifacts resulting from different positions of the kidney image during breath holds. Then, the phase datasets were exported to SPIN for correction processing (presented in the last section) and subsequent analysis. Second, to ensure that each region of interest (ROI) fell within identifiable medullary and cortical sections, one plane through the renal hilum of each kidney was used for the image analysis at the point where the optimal contrast between the cortex and medulla was observed. The kidney ROI was divided into three segments; one cortical ROI and one medullary ROI were drawn in each segment (6-10 pixels within each ROI) and transferred to phase images and T2* maps to measure the parameters (Fig. 1). The mean phase (φcortex and φmedulla), and mean T2* (T2*cortex and T2*medulla) values were calculated by averaging the cortical and medullary ROIs, respectively, measured by the two radiologists. The relative changes (RC) in the mean phase and T2* values after water loading were calculated using the following equations. (2),RCp=Δφφ0×100%

Bottom Line: 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).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).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.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Third Affiliated Hospital of Suzhou University, Changzhou, Jiangsu 213003, China.

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.

No MeSH data available.