B 1 + $$ {\mathrm{B}}_1^{+} $$ mapping near metallic implants using turbo spin echo pulse sequences.

Area of Science:

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

Background:

• Accurate B1+ field mapping is crucial for quantitative MRI.
• Metal implants in patients cause image artifacts and B1+ estimation errors.
• Existing B1+ mapping techniques struggle with metal-induced susceptibility effects.

Purpose of the Study:

• To introduce a novel B1+ mapping technique for MRI of body parts with metal hardware.
• To utilize turbo spin echo (TSE) sequences for B1+ estimation in challenging anatomical regions.
• To overcome limitations of conventional B1+ mapping in the presence of metallic implants.

Main Methods:

• Acquired multiple TSE image sets with varying flip angles (2-4 sets).
• Matched signal intensities to a Bloch-equation-simulated database.
• Validated against dual-angle methods and a vendor sequence in phantoms and human subjects.

Main Results:

• Excellent agreement with reference methods in non-metal phantoms and subjects.
• High correlation with spin echo dual-angle method in subjects without metal.
• Successfully resolved B1+ near metal implants, unlike reference techniques with narrow estimation ranges.

Conclusions:

• The proposed TSE-based B1+ mapping technique accurately quantifies B1+ fields near metal hardware.
• This method overcomes susceptibility-related and range limitations of standard mapping sequences.
• Enables improved quantitative MRI and B1+ shimming in patients with metallic implants.