Quantitative magnetization transfer imaging using balanced SSFP

Gloor, M; Scheffler, Klaus; Bieri, Oliver

doi:10.1002/mrm.21705

Cited by 133 publications

(280 citation statements)

References 32 publications

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“…binary spin-bath model) as described in detail elsewhere (9)(10)(11)(12). In contrast to common MT prepared SPGR methods, the RF pulse train used for imaging is responsible for the MT effect with bSSFP.…”

Section: Two-pool Bloch Simulationmentioning

confidence: 99%

Finite RF pulse correction on DESPOT2

Crooijmans

Scheffler

Bieri

2010

Magnetic Resonance in Med

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Magnetization transfer and finite radiofrequency (RF) pulses affect the steady state of balanced steady state free precession. As quantification of transverse relaxation (T 2 ) with driven equilibrium single pulse observation of T 2 is based on two balanced steady state free precession acquisitions, both effects can influence the outcome of this method: a short RF pulse per repetition time (T RF /TR ( 1) leads to considerable magnetization transfer effects, whereas prolonged RF pulses (T RF /TR > 0.2) minimize magnetization transfer effects, but lead to increased finite pulse effects. A correction for finite pulse effects is thus implemented in the driven equilibrium single pulse observation of T 2 theory to compensate for reduced transverse relaxation effects during excitation. It is shown that the correction successfully removes the driven equilibrium single pulse observation of T 2 dependency on the RF pulse duration. A reduction of the variation in obtained T 2 from over 50% to less than 10% is achieved. We hereby provide a means of acquiring magnetization transfer-free balanced steady state free precession images to yield accurate T 2 values using elongated RF pulses. Magn Reson Med 65:858-862,

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Section: Two-pool Bloch Simulationmentioning

confidence: 99%

Finite RF pulse correction on DESPOT2

Crooijmans

Scheffler

Bieri

2010

Magnetic Resonance in Med

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“…In contrast to quantitative MT imaging, where finite RF pulse effects can be fully taken into account from an adaptation of the bSSFP MT signal model (21), simple semiquantitative estimates, such as MTR values (see Figs. 9 and 10), cannot be corrected for.…”

Section: Discussionmentioning

confidence: 99%

“…Short RF pulses, however, lead to pronounced magnetization transfer (MT) effects in tissues (14) which may impair the accuracy of common SSFP-based quantitative MR imaging techniques, such as fast relaxation time mapping with inversion recovery SSFP (15,16) or variable nutation SSFP (17). Thus, long RF pulses were proposed to be used with these techniques to suppress MT effects (18,19), but it also became evident that signal modulations from finite RF pulses can no longer be neglected (18,20,21). In principle, signal models of quantitative SSFP imaging techniques can be adapted to take into account finite RF pulse effects, as proposed with variable nutation SSFP and quantitative MT (20,21), but a correction of semiquantitative methods, such as magnetization transfer ratio (MTR) imaging (22), is not possible.…”

mentioning

confidence: 99%

“…Thus, long RF pulses were proposed to be used with these techniques to suppress MT effects (18,19), but it also became evident that signal modulations from finite RF pulses can no longer be neglected (18,20,21). In principle, signal models of quantitative SSFP imaging techniques can be adapted to take into account finite RF pulse effects, as proposed with variable nutation SSFP and quantitative MT (20,21), but a correction of semiquantitative methods, such as magnetization transfer ratio (MTR) imaging (22), is not possible. Thus, although in many cases finite RF pulse effects can be accounted for in the transient and in the steady state, their presence seems more of a hindrance than an aid and in practice suppression of finite RF effects might frequently be highly desirable.…”

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confidence: 99%

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Superbalanced steady state free precession

Bieri

2011

Magnetic Resonance in Med

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Steady state free precession (SSFP) signal theory is commonly derived in the limit of quasi-instantaneous radiofrequency (RF) excitation. SSFP imaging protocols, however, are frequently set up with minimal pulse repetition times and RF pulses can thus constitute a considerable amount to the actual pulse repetition time. As a result, finite RF pulse effects can lead to 10-20% signal deviation from common SSFP theory in the transient and in the steady state which may impair the accuracy of SSFP-based quantitative imaging techniques. In this article, a new and generic approach for intrinsic compensation of finite RF pulse effects is introduced. Compensation is based on balancing relaxation effects during finite RF excitation, similar to flow or motion compensation of gradient moments. RF pulse balancing, in addition to the refocusing of gradient moments with balanced SSFP, results in a superbalanced SSFP sequence free of finite RF pulse effects in the transient and in the steady state; irrespective of the RF pulse duration, flip angles, relaxation times, or off-resonances. In multipulse experiments, the time evolution of spins is commonly analyzed in the limit of quasi-instantaneously acting radiofrequency (RF) pulses. This concept separates the Bloch equations (1) into repetitive units of RF excitation and interpulse delays (2) and thereby allows the derivation of closed form solutions to steady state free precession (SSFP) sequences in the steady state (3-7) and the transient phase (8-11). In practice, however, RF pulses have a finite duration (T RF ) and may cause systematic deviations from the solutions derived in the limit of quasi-instantaneous RF pulses (12,13). An introductory example of this behavior is presented in Fig. 1 for balanced SSFP (bSSFP). The range of finite RF pulse effects is illustrated for the steady state amplitude (Fig. 1a) and for the decay factor of the transient (Fig. 1b) as a function of the flip angle (a) for the two extremes of quasi-instantaneous (T RF ! 0) and quasi-continuous (T RF ! pulse repetition time [TR]) excitation. Generally, finite RF pulse effects increase with increasing flip angle and relaxation time ratio (L :¼ T 1 /T 2 ) and show a smooth transition with the fractional RF pulse duration (l :¼ T RF /TR) (12). However, neither bSSFP contrast nor its spin-echo nature is affected by finite RF pulse effects (13).Following the common doctrine, SSFP imaging protocols have minimal TR and short excitation periods. Short RF pulses, however, lead to pronounced magnetization transfer (MT) effects in tissues (14) which may impair the accuracy of common SSFP-based quantitative MR imaging techniques, such as fast relaxation time mapping with inversion recovery SSFP (15,16) or variable nutation SSFP (17). Thus, long RF pulses were proposed to be used with these techniques to suppress MT effects (18,19), but it also became evident that signal modulations from finite RF pulses can no longer be neglected (18,20,21). In principle, signal models of quantitative SSFP imaging techniques c...

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“…Furthermore, SSFP sequences show an inherent MT contrast enhancement, as shown by (12,13) which might be beneficial for coronary vein imaging. In a thin slab acquisition, the inflow of fresh blood increases the blood signal-to-noise ratio (SNR) and yields better CNR for GRE imaging.…”

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confidence: 99%

Whole heart magnetization‐prepared steady‐state free precession coronary vein MRI

Stoeck

Han

Peters

et al. 2009

Magnetic Resonance Imaging

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Purpose: To compare two coronary vein imaging techniques using whole-heart balanced steady-state free precession (SSFP) and a targeted double-oblique spoiled gradient-echo (GRE) sequences in combination with magnetization transfer (MT) preparation sequence for tissue contrast improvement. Materials and Methods:Nine healthy subjects were imaged with the proposed technique. The results are compared with optimized targeted MT prepared GRE acquisitions. Both quantitative and qualitative analyses were performed to evaluate each imaging method.Results: Whole-heart images were successfully acquired with no visible image artifact in the vicinity of the coronary veins. The anatomical features and visual grading of both techniques were comparable. However, the targeted small slab acquisition of the left ventricular lateral wall was superior to whole-heart acquisition for visualization of relevant information for cardiac resynchronization therapy (CRT) lead implantation. Conclusion:We demonstrated the feasibility of wholeheart coronary vein MRI using a 3D MT-SSFP imaging sequence. A targeted acquisition along the lateral left ventricular wall is preferred for visualization of branches commonly used in CRT lead implantation.

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Quantitative magnetization transfer imaging using balanced SSFP

Cited by 133 publications

References 32 publications

Finite RF pulse correction on DESPOT2

Finite RF pulse correction on DESPOT2

Superbalanced steady state free precession

Whole heart magnetization‐prepared steady‐state free precession coronary vein MRI

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