Dvir Radunsky1, Tamar Blumenfeld-Katzir1, Osnat Volovyk2, Assaf Tal2, Daniel Barazany3, Galia Tsarfaty4, Noam Ben-Eliezer1,5,6. 1. Department of Biomedical Engineering, Tel Aviv University, Tel Aviv, Israel. 2. Department of Chemical Physics, The Weizmann Institute, Rehovot, Israel. 3. Strauss computational neuroimaging center, Tel Aviv University, Tel Aviv, Israel. 4. Department of Diagnostic Imaging, Sheba Medical Center, Ramat Gan, Israel. 5. Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel. 6. Center for Advanced Imaging Innovation and Research (CAI2R), NewYork University Langone Medical Center, New York, New York.
Abstract
PURPOSE: Multi-echo spin-echo (MESE) protocol is the most effective tool for mapping T2 relaxation in vivo. Still, MESE extensive use of radiofrequency pulses causes magnetization transfer (MT)-related bias of the water signal, instigated by the presence of macromolecules (MMP). Here, we analyze the effects of MT on MESE signal, alongside their impact on quantitative T2 measurements. METHODS: Study used 3 models: in vitro urea phantom, ex vivo horse brain, and in vivo human brain. MT ratio (MTR) was measured between single-SE and MESE protocols under different scan settings including varying echo train lengths, number of slices, and inter-slice gap. MTR and T2 values were extracted for each model and protocol. RESULTS: MT interactions biased MESE signals, and in certain settings, the corresponding T2 values. T2 underestimation of up to 4.3% was found versus single-SE values in vitro and up to 13.8% ex vivo, correlating with the MMP content. T2 bias originated from intra-slice saturation of the MMP, rather than from indirect saturation in multi-slice acquisitions. MT-related signal attenuation was caused by slice crosstalk and/or partial T1 recovery, whereas smaller contribution was caused by MMP interactions. Inter-slice gap had a similar effect on in vivo MTR (21.2%), in comparison to increasing the number of slices (18.9%). CONCLUSIONS: MT influences MESE protocols either by uniformly attenuating the entire echo train or by cumulatively attenuating the signal along the train. Although both processes depend on scan settings and MMP content, only the latter will cause underestimation of T2 .
PURPOSE: Multi-echo spin-echo (MESE) protocol is the most effective tool for mapping T2 relaxation in vivo. Still, MESE extensive use of radiofrequency pulses causes magnetization transfer (MT)-related bias of the water signal, instigated by the presence of macromolecules (MMP). Here, we analyze the effects of MT on MESE signal, alongside their impact on quantitative T2 measurements. METHODS: Study used 3 models: in vitro urea phantom, ex vivo horse brain, and in vivo human brain. MT ratio (MTR) was measured between single-SE and MESE protocols under different scan settings including varying echo train lengths, number of slices, and inter-slice gap. MTR and T2 values were extracted for each model and protocol. RESULTS: MT interactions biased MESE signals, and in certain settings, the corresponding T2 values. T2 underestimation of up to 4.3% was found versus single-SE values in vitro and up to 13.8% ex vivo, correlating with the MMP content. T2 bias originated from intra-slice saturation of the MMP, rather than from indirect saturation in multi-slice acquisitions. MT-related signal attenuation was caused by slice crosstalk and/or partial T1 recovery, whereas smaller contribution was caused by MMP interactions. Inter-slice gap had a similar effect on in vivo MTR (21.2%), in comparison to increasing the number of slices (18.9%). CONCLUSIONS: MT influences MESE protocols either by uniformly attenuating the entire echo train or by cumulatively attenuating the signal along the train. Although both processes depend on scan settings and MMP content, only the latter will cause underestimation of T2 .
Authors: S Floris; E L A Blezer; G Schreibelt; E Döpp; S M A van der Pol; I L Schadee-Eestermans; K Nicolay; C D Dijkstra; H E de Vries Journal: Brain Date: 2003-12-22 Impact factor: 13.501
Authors: Tom Hilbert; Ding Xia; Kai Tobias Block; Zidan Yu; Riccardo Lattanzi; Daniel K Sodickson; Tobias Kober; Martijn A Cloos Journal: Magn Reson Med Date: 2019-11-25 Impact factor: 4.668
Authors: Ellen van der Plas; Laurie Gutmann; Dan Thedens; Richard K Shields; Kathleen Langbehn; Zhihui Guo; Milan Sonka; Peggy Nopoulos Journal: Muscle Nerve Date: 2021-02-05 Impact factor: 3.217
Authors: Francesco Santini; Xeni Deligianni; Matteo Paoletti; Francesca Solazzo; Matthias Weigel; Paulo Loureiro de Sousa; Oliver Bieri; Mauro Monforte; Enzo Ricci; Giorgio Tasca; Anna Pichiecchio; Niels Bergsland Journal: Front Neurol Date: 2021-02-26 Impact factor: 4.003
Authors: Sen Ma; Nan Wang; Zhaoyang Fan; Marwa Kaisey; Nancy L Sicotte; Anthony G Christodoulou; Debiao Li Journal: Magn Reson Med Date: 2020-10-26 Impact factor: 4.668