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Quantification of holmium-166 loaded microspheres: estimating high local concentrations using a conventional multiple
Gerrit H van de Maat1, Peter R Seevinck, Clemens Bos
1Image Sciences Institute, University Medical Center Utrecht, The Netherlands. g.h.vandemaat@umcutrecht.nl
Journal of Magnetic Resonance Imaging : JMRI
|January 28, 2012
Summary
A new S(0)-fitting method accurately estimates high R2* values for holmium-166 loaded microspheres (HoMS). This technique improves quantification of HoMS concentration in medical imaging, overcoming limitations of conventional fitting methods.
Area of Science:
- Medical Imaging
- Biophysics
- Radiochemistry
Background:
- Accurate quantification of holmium-166 loaded microspheres (HoMS) is crucial for targeted therapies.
- Conventional R2* fitting methods struggle with fast signal decay in voxels with high HoMS concentrations.
- Existing methods limit the characterization of R2* values, impacting local concentration estimates.
Purpose of the Study:
- To develop and validate a postprocessing method, S(0)-fitting, for estimating high R2* values.
- To improve the quantification of local HoMS concentrations in voxels where conventional fitting fails.
- To provide a best estimate of R2* for highly paramagnetic HoMS.
Main Methods:
- Implemented S(0)-fitting as a postprocessing step within conventional R2* fitting.
- Incorporated estimated initial amplitude (S(0)) from neighboring voxels into the fitting procedure.
- Validated the method in vitro and ex vivo (rabbit liver) using quantitative ultrashort TE imaging (qUTE).
Main Results:
- S(0)-fitting successfully estimated R2* values up to approximately 2300 s(-1), exceeding the ~1000 s(-1) limit of conventional fitting.
- Qualitative and quantitative agreement was observed between S(0)-fitting and qUTE imaging.
- The method demonstrated good performance in both in vitro and ex vivo HoMS experiments.
Conclusions:
- S(0)-fitting is an effective postprocessing technique for characterizing high R2* values beyond conventional relaxometry limits.
- The method is applicable to standard multigradient echo (MGE) datasets.
- S(0)-fitting significantly benefits the quantification of high local concentrations of holmium-loaded microspheres.
