Can multi-slice or navigator-gated R2* MRI replace single-slice breath-hold acquisition for hepatic iron quantification?
Liver R2* values calculated from multi-gradient echo (mGRE) magnetic resonance images (MRI) are strongly correlated with hepatic iron concentration (HIC) as shown in several independently derived biopsy calibration studies. These calibrations were established for axial single-slice breath-hold imaging at the location of the portal vein. Scanning in multi-slice mode makes the exam more efficient, since whole-liver coverage can be achieved with two breath-holds and the optimal slice can be selected afterward. Navigator echoes remove the need for breath-holds and allow use in sedated patients.
To evaluate if the existing biopsy calibrations can be applied to multi-slice and navigator-controlled mGRE imaging in children with hepatic iron overload, by testing if there is a bias-free correlation between single-slice R2* and multi-slice or multi-slice navigator controlled R2*.
Materials and methods
This study included MRI data from 71 patients with transfusional iron overload, who received an MRI exam to estimate HIC using gradient echo sequences. Patient scans contained 2 or 3 of the following imaging methods used for analysis: single-slice images (n = 71), multi-slice images (n = 69) and navigator-controlled images (n = 17). Small and large blood corrected region of interests were selected on axial images of the liver to obtain R2* values for all data sets. Bland-Altman and linear regression analysis were used to compare R2* values from single-slice images to those of multi-slice images and navigator-controlled images.
Bland-Altman analysis showed that all imaging method comparisons were strongly associated with each other and had high correlation coefficients (0.98 ≤ r ≤ 1.00) with P-values ≤0.0001. Linear regression yielded slopes that were close to 1.
We found that navigator-gated or breath-held multi-slice R2* MRI for HIC determination measures R2* values comparable to the biopsy-validated single-slice, single breath-hold scan. We conclude that these three R2* methods can be interchangeably used in existing R2*-HIC calibrations.
KeywordsChildren Hepatic iron concentration Iron Iron quantification Liver Magnetic resonance imaging R2* quantification T2*
The authors thank Wendy Pyburn for assistance with data collection, Gail Fortner, RN, for support with patient selection, and Aaryani Sajja and Nathan Artz for reviewing the manuscript.
This work was supported in part by the American Lebanese Syrian Associated Charities (ALSAC – the fund-raising organization of St. Jude Children’s Research Hospital), by grant 5 R01 DK088988 from the National Institute of Diabetes and Digestive and Kidney Diseases and grant 5 R25 CA23944 from the National Cancer Institute.
Compliance with ethical standards
Conflicts of interest
- 38.Song R, Bevington T, Taylor BA et al (2013) Evaluation of correction methods for errors in T2* quantification caused by background gradients. Paper presented at the Proceedings of the 21st Scientific Meeting, International Society for Magnetic Resonance in Medicine, Salt Lake City, UT, USA, April 2013Google Scholar