PURPOSE: MRI relaxation measurements are performed in the presence of a fictitious magnetic field in the recently described technique known as RAFF (Relaxation Along a Fictitious Field). This method operates in the 2(nd) rotating frame (rank n = 2) by using a nonadiabatic sweep of the radiofrequency effective field to generate the fictitious magnetic field. In the present study, the RAFF method is extended for generating MRI contrasts in rotating frames of ranks 1 ≤ n ≤ 5. The developed method is entitled RAFF in rotating frame of rank n (RAFFn). THEORY AND METHODS: RAFFn pulses were designed to generate fictitious fields that allow locking of magnetization in rotating frames of rank n. Contrast generated with RAFFn was studied using Bloch-McConnell formalism together with experiments on human and rat brains. RESULTS: Tolerance to B0 and B1 inhomogeneities and reduced specific absorption rate with increasing n in RAFFn were demonstrated. Simulations of exchange-induced relaxations revealed enhanced sensitivity of RAFFn to slow exchange. Consistent with such feature, an increased grey/white matter contrast was observed in human and rat brain as n increased. CONCLUSION: RAFFn is a robust and safe rotating frame relaxation method to access slow molecular motions in vivo.
n class="abstract_title">PURPOSE: MRI relaxation measurements are performed in the presence of a fictitious magnetic field in the recently described technique known as RAFF (Relaxation Along a Fictitious Field). This method open>n class="Species">rates in the 2(nd) rotating frame (rank n = 2) by using a nonadiabatic sweep of the radiofrequency effective field to generate the fictitious magnetic field. In the present study, the RAFF method is extended for generating MRI contrasts in rotating frames of ranks 1 ≤ n ≤ 5. The developed method is entitled RAFF in rotating frame of rank n (RAFFn). THEORY AND METHODS: RAFFn pulses were designed to generate fictitious fields that allow locking of magnetization in rotating frames of rank n. Contrast generated with RAFFn was studied using Bloch-McConnell formalism together with experiments on human and rat brains. RESULTS: Tolerance to B0 and B1 inhomogeneities and reduced specific absorption rate with increasing n in RAFFn were demonstrated. Simulations of exchange-induced relaxations revealed enhanced sensitivity of RAFFn to slow exchange. Consistent with such feature, an increased grey/white matter contrast was observed in human and rat brain as n increased. CONCLUSION:RAFFn is a robust and safe rotating frame relaxation method to access slow molecular motions in vivo.
Authors: J T Vaughan; G Adriany; M Garwood; E Yacoub; T Duong; L DelaBarre; P Andersen; K Ugurbil Journal: Magn Reson Med Date: 2002-05 Impact factor: 4.668
Authors: Timo Liimatainen; Alejandra Sierra; Timothy Hanson; Dennis J Sorce; Seppo Ylä-Herttuala; Michael Garwood; Shalom Michaeli; Olli Gröhn Journal: Magn Reson Med Date: 2011-06-30 Impact factor: 4.668
Authors: William D Rooney; Glyn Johnson; Xin Li; Eric R Cohen; Seong-Gi Kim; Kamil Ugurbil; Charles S Springer Journal: Magn Reson Med Date: 2007-02 Impact factor: 4.668
Authors: Timo Liimatainen; Dennis J Sorce; Robert O'Connell; Michael Garwood; Shalom Michaeli Journal: Magn Reson Med Date: 2010-10 Impact factor: 4.668
Authors: Luning Wang; Mikko J Nissi; Ferenc Toth; Casey P Johnson; Michael Garwood; Cathy S Carlson; Jutta Ellermann Journal: Magn Reson Med Date: 2016-03-28 Impact factor: 4.668
Authors: Nina Elina Hänninen; Timo Liimatainen; Matti Hanni; Olli Gröhn; Miika Tapio Nieminen; Mikko Johannes Nissi Journal: Sci Rep Date: 2022-07-15 Impact factor: 4.996
Authors: Seyed Amir Mirmojarabian; Eveliina Lammentausta; Esa Liukkonen; Lauri Ahvenjärvi; Juhani Junttila; Miika T Nieminen; Timo Liimatainen Journal: Int J Biomed Imaging Date: 2022-06-23
Authors: Jari Rautiainen; Mikko J Nissi; Elli-Noora Salo; Virpi Tiitu; Mikko A J Finnilä; Olli-Matti Aho; Simo Saarakkala; Petri Lehenkari; Jutta Ellermann; Miika T Nieminen Journal: Magn Reson Med Date: 2014-08-07 Impact factor: 4.668
Authors: Luning Wang; Mikko J Nissi; Ferenc Tóth; Jonah Shaver; Casey P Johnson; Jinjin Zhang; Michael Garwood; Cathy S Carlson; Jutta M Ellermann Journal: PLoS One Date: 2015-10-16 Impact factor: 3.240