Steady state of gradient echo sequences with radiofrequency phase cycling: Analytical solution, contrast enhancement with partial spoiling

Ganter, Carl

doi:10.1002/mrm.20736

Cited by 37 publications

(92 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As in Ref. 10, we will use the following convention for the local (i.e., x-dependent) complex magnetization density…”

Section: Recursion Relationmentioning

confidence: 99%

“…Explicit expressions for the matrices can be found in Appendix A of Ref. 10. Note that the Bloch equation [9] depends on the accumulated phase per TR, ϑ, and thus applies only to those isochromats with ϑ ≡ ϑ(x), cf.…”

Section: Recursion Relationmentioning

confidence: 99%

“…The focus will be mainly on unbalanced sequences, but it will be shown that the known results for balanced sequences can be reobtained as well. Similar to the solution of the RF-spoiled steady state (10), the coherence pathways will be decomposed into irreducible subpaths and subsequently added. Instead of the abstract index counting presented in Ref.…”

mentioning

confidence: 99%

“…Instead of the abstract index counting presented in Ref. 10, a graph theoretical formulation will be used this time, so that the connection with the familiar phase graph formalism (3,11) should become more transparent.…”

mentioning

confidence: 99%

See 3 more Smart Citations

Analytical solution to the transient phase of steady‐state free precession sequences

Ganter

2009

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

The transient phase of short-TR steady-state free precession (SSFP) sequences exhibits an often striking complexity and is not only important for nonequilibrium applications (e.g., rapid T 1 -measurements), but can also cause severe artifacts in conventional imaging. In both cases, balanced SSFP sequences are practically (with regard to preparation efficiency) and conceptually (concerning the theoretical understanding of the decay) easier to handle their unbalanced counterparts, for which currently no theory is available. Based on a decomposition of coherence pathways into irreducible subpaths, an exact mathematical solution to the transient phase of unbalanced SSFP sequences is presented in this article, which also includes the known results for balanced SSFP and the steady state of arbitrary SSFP sequences as special cases. As an application, it is shown that the familiar Look-Locker expression for the accelerated magnetization recovery in RFspoiled sequences is only valid for T 2 → 0. In addition to oscillatory perturbations, systematic deviations from the monoexponential decay are observed for T 2 > 0 as a consequence of memory effects. Magn Reson Med 62:149-164, 2009.

show abstract

“…As in Ref. 10, we will use the following convention for the local (i.e., x-dependent) complex magnetization density…”

Section: Recursion Relationmentioning

confidence: 99%

Section: Recursion Relationmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Analytical solution to the transient phase of steady‐state free precession sequences

Ganter

2009

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

show abstract

“…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)(4)(5)(6)(7) and the transient phase (8)(9)(10)(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).…”

mentioning

confidence: 99%

Superbalanced steady state free precession

Bieri

2011

Magnetic Resonance in Med

View full text Add to dashboard Cite

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...

show abstract

A plug for catheter plugs in treatment strategies for acquired ventricular septal defects

Latson

2007

Cathet Cardio Intervent

View full text Add to dashboard Cite

Steady state of gradient echo sequences with radiofrequency phase cycling: Analytical solution, contrast enhancement with partial spoiling

Cited by 37 publications

References 12 publications

Analytical solution to the transient phase of steady‐state free precession sequences

Analytical solution to the transient phase of steady‐state free precession sequences

Superbalanced steady state free precession

A plug for catheter plugs in treatment strategies for acquired ventricular septal defects

Contact Info

Product

Resources

About