FID sampling superior to spin-echo sampling for T2*-based quantification of holmium-loaded microspheres: theory and experiment.
This work demonstrates both theoretically and experimentally that multiple gradient-echo sampling of free induction decay (MGEFID) is superior to MGE sampling of spin echo (MGESE) for T2*-based quantification of holmium-loaded microspheres (HoMS). An interleaved sampling strategy was applied in great detail to characterize the MR signal behavior of FID and SE signals of gels and perfused rabbit livers containing HoMS in great detail. Diffusion sensitivity was demonstrated for MGESE sampling, resulting in non-exponential signal decay on both sides of the SE peak and in an underestimation of the HoMS concentration. Other than MGESE sampling, MGEFID sampling was demonstrated to be insensitive to diffusion, to exhibit exponential signal decay, and to allow accurate T2*-based quantification of HoMS. Furthermore, a fit procedure was proposed extending the upper limit of quantifiable R2* relaxation rates to at least 1500 sec(-1). With this post-processing step incorporated, MGEFID was shown to correctly estimate the integral amount of inhomogeneously distributed HoMS in liver tissue, up to a clinically relevant limit. All experimental findings could be explained with the theory of nuclear magnetic resonance (NMR) signal behavior in magnetically inhomogeneous tissues. HoMS were shown to satisfy the static dephasing regime when investigated with MGEFID and to violate the static dephasing conditions for MGESE at longer echo times typically used in SE.
Seevinck
Peter R
PR
Image Sciences Institute, Department of Radiology, University Medical Center Utrecht, The Netherlands. p.seevinck@umcutrecht.nl
Seppenwoolde
Jan-Henry
JH
Zwanenburg
Jaco J M
JJ
Nijsen
Johannes F W
JF
Bakker
Chris J G
CJ
D000465:Algorithms; D000818:Animals; D003198:Computer Simulation; D004337:Drug Carriers / Q000737:chemistry; D006695:Holmium / Q000737:chemistry; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging; D008863:Microspheres; D008954:Models, Biological; D011817:Rabbits; D015203:Reproducibility of Results; D018401:Sample Size; D012680:Sensitivity and Specificity; D013113:Spin Labels
D004337:Drug Carriers; D013113:Spin Labels; D006695:Holmium