PET attenuation correction for rigid MR Tx/Rx coils from ¹⁷⁶Lu background activity

Area of Science:

• Medical Imaging
• Nuclear Medicine
• Biophysics

Background:

• Positron Emission Tomography-Magnetic Resonance (PET-MR) imaging faces challenges in correcting for radiofrequency (RF) coil attenuation of 511 keV annihilation radiation.
• Optimized PET-transparent RF coils still cause significant attenuation, leading to artifacts and biases in reconstructed activity concentrations.

Purpose of the Study:

• To present a straightforward method for measuring RF coil attenuation in simultaneous MR-PET imaging.
• To evaluate this method using natural lutetium-176 (¹⁷⁶Lu) background within the PET detector scintillator.

Main Methods:

• Developed a method to measure RF coil attenuation using the natural ¹⁷⁶Lu gamma background in the PET detector.
• Evaluated the method on a prototype 3T MR-BrainPET using phantom studies and patient/volunteer emission images.
• Investigated PET scanner count rate stability and RF head coil X-ray properties.

Main Results:

• The ¹⁷⁶Lu background-based attenuation correction method demonstrated slightly better performance than the current coil attenuation correction method, even without energy extrapolation.
• The current method relies on external transmission scans with rotating ⁶⁸Ge sources.
• The proposed method offers straightforwardness and ready availability without additional accessories.

Conclusions:

• The presented method provides an effective and easily accessible approach for attenuation correction in MR-PET imaging.
• This technique improves the accuracy of reconstructed activity concentrations by addressing RF coil attenuation.
• The method eliminates the need for external CT scanners or dedicated transmission sources.