Work

The harmonic residual index: a spectral purity metric for magnetic hyperthermia RF generators

Year: 2026

Type: article

Abstract: RF generators are core components of magnetic hyperthermia (MH) systems, yet output quality is rarely characterized beyond nominal frequency and amplitude. Harmonic distortion can introduce parasitic components that complicate reproducibility and accurate field characterization; MH-specific spectral quality indices remain limited. This study proposes two indices for RF generator output quality assessment in MH: the harmonic residual index ( HRI ) and a simulation-derived harmonic specific absorption rate (SAR) contribution index ( Λ ¯ SAR ). A sinusoidal RF generator (50–200 kHz, 115 W) was evaluated with three coil configurations at 10%–100% power. Spatial magnetic-field measurements were acquired using a passive search coil, and HRI was computed pointwise to generate harmonic distortion maps. THD was computed from the same spectra for benchmarking. Spatial mean HRI ( HRI ― ) and THD ( THD ― ) were modelled using weighted power-law fitting. Inductive heating experiments (120–166.5 mg ml −1 MNP) evaluated the reliability of experimental calorimetry, motivating a shift toward simulation-based dosimetry. Finite element method (FEM) simulations of a simplified neck model driven by measured harmonics estimated relative harmonic SAR contributions and Λ ¯ SAR . HRI ― ranged from 0.17 ± 0.04 to 16.41 ± 3.48 (RMSE = 0.301–1.523) and increased monotonically with power level across all coils, while THD showed smaller variations and less spatially structured behaviour. Experimental heating trials yielded marginal temperature elevations (⩽2.5 °C) with quantization errors, demonstrating that standard calorimetry is metrologically insufficient for SAR derivation at clinical field intensities. Conversely Λ ¯ SAR ranged from 2.23E + 4 to 2.70E + 6, indicating low harmonic contributions relative to the fundamental under the tested conditions. HRI

Source: Journal of Physics D Applied Physics

DOI: 10.1088/1361-6463/ae9d8a

Authors: Serhat Ilgaz Yöner, Alpay Özcan, Oğuz Akın

Institutions: Acıbadem University, Boğaziçi University, Memorial Sloan Kettering Cancer Center

Language: English

Topic: Characterization and Applications of Magnetic Nanoparticles

Subfield: Biomedical Engineering

Field: Engineering

Domain: Physical Sciences

SDG: Good health and well-being

Open Access status: hybrid

Estimated APC paid: $3,325