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Objective <p>Within gradient-spoiled transient-state MR sequences like Magnetic Resonance Fingerprinting or Magnetic Resonance Spin TomogrAphy in Time-domain (MR-STAT), it is examined whether an optimized RF phase modulation can help to improve the precision of the resulting relaxometry maps.</p> Methods <p>Using a Cramer-Rao based method called BLAKJac, optimized sequences of RF pulses have been generated for two scenarios (amplitude-only modulation and amplitude + phase modulation) and for several conditions. These sequences have been tested on a phantom, a healthy human brain and a healthy human leg, to reconstruct parametric maps (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({T}_{1}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({T}_{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation>) as well as their standard deviations.</p> Results <p>The amplitude + phase modulation scenario systematically resulted in lower noise levels than the amplitude-only modulation scenario. On average, the difference was around 34%, but it was substantially larger for scans acquired under SAR restrictions. Compared to amplitude-only, in the amplitude + phase modulation scenario, the relevance of an inversion pulse and of a pause were greatly reduced, at least considering overall precision and in-phantom accuracy.</p> Conclusion <p>The application of an optimized RF phase modulation in quantitative transient-states MRI is beneficial for almost all tested scenarios and conditions, in particular under SAR restrictions Furthermore, RF phase modulation reduces the need for inversions pulses and pauses.</p>

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RF phase modulation improves quantitative transient state sequences under constrained conditions

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年9月11日

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  • Miha Fuderer,
  • Hongyan Liu,
  • Oscar van der Heide,
  • Cornelis A. T. van den Berg,
  • Alessandro Sbrizzi

摘要

Objective

Within gradient-spoiled transient-state MR sequences like Magnetic Resonance Fingerprinting or Magnetic Resonance Spin TomogrAphy in Time-domain (MR-STAT), it is examined whether an optimized RF phase modulation can help to improve the precision of the resulting relaxometry maps.

Methods

Using a Cramer-Rao based method called BLAKJac, optimized sequences of RF pulses have been generated for two scenarios (amplitude-only modulation and amplitude + phase modulation) and for several conditions. These sequences have been tested on a phantom, a healthy human brain and a healthy human leg, to reconstruct parametric maps ( \({T}_{1}\) T 1 and \({T}_{2}\) T 2 ) as well as their standard deviations.

Results

The amplitude + phase modulation scenario systematically resulted in lower noise levels than the amplitude-only modulation scenario. On average, the difference was around 34%, but it was substantially larger for scans acquired under SAR restrictions. Compared to amplitude-only, in the amplitude + phase modulation scenario, the relevance of an inversion pulse and of a pause were greatly reduced, at least considering overall precision and in-phantom accuracy.

Conclusion

The application of an optimized RF phase modulation in quantitative transient-states MRI is beneficial for almost all tested scenarios and conditions, in particular under SAR restrictions Furthermore, RF phase modulation reduces the need for inversions pulses and pauses.