Dual-Pathway sequences for MR thermometry: When and where to use them

Area of Science:

• Medical Imaging
• Magnetic Resonance Imaging (MRI)
• Biophysics

Background:

• MR thermometry is crucial for monitoring tissue temperature during treatments.
• Improving the temperature-to-noise ratio (TNR) is key for accurate MR thermometry.
• Dual-pathway sequences offer a potential method to enhance TNR.

Purpose of the Study:

• To evaluate the performance of dual-pathway PSIF-FISP sequences for MR thermometry.
• To quantify the temperature-to-noise ratio (TNR) improvements in various organs and tissues.
• To determine optimal acquisition parameters for PSIF-FISP sequences.

Main Methods:

• Simulations and TNR calculations were performed and validated against analytical equations and phantom scans.
• Relative TNRs of PSIF-FISP were compared to a dual-FISP reference across a range of flip angles (FA) and repetition times (TR).
• Tissue types included gray matter, white matter, kidney, liver, muscle, pancreas, spleen, and reproductive organs.

Main Results:

• PSIF-FISP demonstrated superior TNR in kidney, pelvis, spleen, and gray matter across most tested parameters, with benefits increasing at shorter TRs.
• Significant TNR gains (up to 20%) were achieved with two- to three-fold reductions in TR.
• Tissue-specific optimization of TR and FA is necessary, as benefits vary by tissue type and acquisition settings.

Conclusions:

• Dual-pathway PSIF-FISP sequences can improve TNR and acquisition speed in MR thermometry.
• Optimal acquisition parameters are tissue-dependent, requiring tailored settings for different organs.
• Further improvements in TNR are expected with tissue heating due to altered relaxation rates.