T₁ Thermometry for Deep Brain Stimulation Applications: A Comparison between Rapid Gradient Echo Sequences

Area of Science:

• Medical Imaging
• Biophysics
• Neuroscience

Background:

• T1 thermometry is crucial for monitoring radiofrequency-induced heating in patients with deep brain stimulation (DBS) electrodes during MRI.
• Ensuring patient safety during MRI with implanted devices requires precise temperature monitoring methods.

Purpose of the Study:

• To compare the image quality of two T1 thermometry methods and two low specific absorption rate (SAR) imaging sequences.
• To evaluate the effectiveness of different MRI sequences and thermometry techniques for detecting heating around DBS electrodes.

Main Methods:

• An experimental study using a brain-mimicking gel phantom with a central copper wire.
• Two rapid gradient echo sequences (radiofrequency-spoiled and balanced steady-state free precession - bSSFP) were employed.
• T1 thermometry was performed using T1-weighted images with a high SAR sequence and T1 mapping methods.

Main Results:

• The bSSFP sequence demonstrated superior image quality, offering higher spatial resolution (1x1x1.5 mm3 vs. 1x1x3 mm3) and reduced susceptibility artifacts compared to the radiofrequency-spoiled sequence.
• Acquisition time was shorter with the bSSFP sequence.
• A temperature increase of up to 8°C was observed with the high SAR sequence, with a reduced estimated temperature change using T1 mapping.

Conclusions:

• High-resolution T1 maps derived from inversion recovery bSSFP sequences can accurately estimate MRI-induced heating around implanted electrodes.
• This method provides direct estimation of heating, essential for safe Magnetic Resonance Imaging (MRI) procedures in patients with deep brain stimulation (DBS).