Accelerated model-based proton resonance frequency shift temperature mapping using echo-based GRAPPA reconstruction.

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Medical Physics

Background:

• Accurate MR temperature estimation is crucial for various applications, including thermal ablation monitoring.
• The proton resonance frequency (PRF) shift method is a common technique for MR thermometry.
• Current methods can be time-consuming, necessitating acceleration strategies.

Purpose of the Study:

• To develop and validate an accelerated MR temperature estimation method.
• To utilize a model-based PRF shift approach with enhanced speed.
• To assess the accuracy of the proposed acceleration technique.

Main Methods:

• A multi-echo gradient-recalled echo (GRE) sequence was used to acquire images at 16 echo times (TE).
• Retrospective undersampling of k-space data was performed at reduction factors of 2-3.
• A novel reconstruction method, Echo-based GRAPPA, combined data from three TEs for accelerated imaging.

Main Results:

• Echo-based GRAPPA achieved a reconstruction-induced temperature Root Mean Square Error (RMSE) below 1.4 °C in ex vivo liver experiments (reduction factor 2.3).
• In vivo breast imaging demonstrated a mean temperature error of 2.3 °C in water-fat mixed regions (reduction factor 2.7).
• The proposed Echo-based GRAPPA method showed lower temperature RMSE compared to conventional GRAPPA.

Conclusions:

• The developed Echo-based GRAPPA method effectively accelerates MR temperature estimation using the model-based PRF shift.
• The technique achieves acceleration factors of 2-3 with temperature errors below 3°C in relevant imaging scenarios.
• This acceleration holds promise for improving the efficiency of MR thermometry.