Non-calorimetric determination of absorbed power during magnetic nanoparticle based hyperthermia

TL;DR

This paper introduces a non-invasive, real-time method to measure absorbed power during magnetic nanoparticle hyperthermia by monitoring the quality factor change in a resonant RF circuit, avoiding traditional calorimetry issues.

Contribution

It presents a novel non-calorimetric technique based on RF circuit quality factor measurement for accurate, real-time power assessment in magnetic hyperthermia, compatible with MRI hardware.

Findings

Validated the method against conventional calorimetry.

Demonstrated applicability with solenoid and birdcage RF coils.

Enables integration of hyperthermia monitoring with MRI systems.

Abstract

Nanomagnetic hyperthermia (NMH) is intensively studied with the prospect of cancer therapy. A major challenge is to determine the dissipated power during in vivo conditions and conventional methods are either invasive or inaccurate. We present a non-calorimetric method which yields the heat absorbed during hyperthermia: it is based on accurately measuring the quality factor change of a resonant radio frequency circuit which is employed for the irradiation. The approach provides the absorbed power in real-time, without the need to monitor the sample temperature as a function of time. As such, it is free from the problems caused by the non-adiabatic heating conditions of the usual calorimetry. We validate the method by comparing the dissipated power with a conventional calorimetric measurement. We present the validation for two types of resonators with very different filling factors: a solenoid and a so-called birdcage coil. The latter is a volume coil, which is generally used in magnetic resonance imaging (MRI) under in vivo condition. The presented method therefore allows to effectively combine MRI and thermotherapy and is thus readily adaptable to existing imaging hardware.