T2 quantification from only proton density and T2-weighted MRI by modelling actual refocusing angles

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biophysics

Background:

• Proton density (PD) and T2-weighted fast spin echo (FSE) images are standard in MRI.
• Exponential fitting is commonly used for T2 quantification but is inaccurate with imperfect radiofrequency (RF) refocusing.

Purpose of the Study:

• To assess the feasibility of accurate T2 quantification using a two echo fitting method.
• To validate this method against standard exponential fitting and multi-echo spin echo techniques.

Main Methods:

• Utilized Bloch equation simulations with known refocusing angles.
• Applied the two echo fitting method to standard PD and T2-weighted FSE images.
• Validated results using phantom and human brain experiments, comparing against exponential and multi-echo spin echo methods.

Main Results:

• The two echo fitting method accurately quantifies T2 values across various flip angles and T2 ranges.
• This method compensates for indirect and stimulated echoes, overcoming limitations of exponential fitting.
• Accuracy is dependent on adequate signal-to-noise ratio (SNR) and knowledge of flip angles.

Conclusions:

• Accurate T2 quantification is achievable with standard MRI sequences using the proposed two echo fitting method.
• This technique offers a more robust alternative to exponential fitting, especially in the presence of RF imperfections.
• The method holds promise for reliable quantitative MRI measurements in clinical and research settings.