Advances in Frequency-Mixing MPI: Block-ADMM Multi-Contrast Reconstruction for Drug-Release Thermometry and Monitoring

Magnetic particle imaging (MPI) provides quantitative maps of magnetic nanoparticle concentration and is well suited for monitoring magnetically induced hyperthermia and drug release. Building on the frequency-mixing, narrowband MPI platform previously presented at IWMPI 2024, we now focus on a reconstruction framework based on a block Alternating Direction Method of Multipliers (block-ADMM) operator formulation for efficient multi-contrast image recovery. The system employs dual-frequency excitation around 280 kHz and < 1 kHz, allowing simultaneous heating and imaging with excellent spectral separation and sensitivity. The proposed algorithm jointly inverts multiple spectral components centered at 2?fHF ± N?fLF that share a common nanoparticle distribution while exploiting their complementary spatial responses. This operator-based formulation enables near real-time reconstruction with improved resolution and noise robustness. First experimental results demonstrate temperature-dependent contrast formation, establishing a foundation for potentially quantitative MPI thermometry and feedback-controlled drug release.