Abstract
Targeted radiofrequency (RF) heating induced hyperthermia has a wide range of applications, ranging from adjunct anti-cancer treatment to localized release of drugs. Focal RF heating is usually approached using time-consuming nonconvex optimization procedures or approximations, which significantly hampers its application. To address this limitation, this work presents an algorithm that recasts the problem as a semidefinite program and quickly solves it to global optimality, even for very large (human voxel) models. The target region and a desired RF power deposition pattern as well as constraints can be freely defined on a voxel level, and the optimum application RF frequencies and time-multiplexed RF excitations are automatically determined. 2D and 3D example applications conducted for test objects containing pure water (rtarget = 19 mm, frequency range: 500–2000 MHz) and for human brain models including brain tumors of various size (r1 = 20 mm, r2 = 30 mm, frequency range 100–1000 MHz) and locations (center, off-center, disjoint) demonstrate the applicability and capabilities of the proposed approach. Due to its high performance, the algorithm can solve typical clinical problems in a few seconds, making the presented approach ideally suited for interactive hyperthermia treatment planning, thermal dose and safety management, and the design, rapid evaluation, and comparison of RF applicator configurations.
Highlights
Vigorous fundamental andengineering research into electromagnetic field radiation induced heating of tissue has culminated in an enormous body of literature [1,2,3,4]
The target region and a desired RF power deposition pattern as well as constraints can be freely defined on a voxel level, and the optimum application RF frequencies and time-multiplexed RF excitations are automatically determined. 2D
Localized tissue heating induced by electromagnetic fields (EMF) has a wide array of applications ranging from thermal therapy as a potent sensitizer of chemo- and radiotherapy to the controlled release of therapeutics from a nano-carrier [5,6,7,8,9,10,11,12]
Summary
Vigorous fundamental and (bio)engineering research into electromagnetic field radiation induced heating of tissue has culminated in an enormous body of literature [1,2,3,4]. Radiofrequency (RF) heating relies on the interference of electric fields produced by multiple independent RF sources, which are sought to constructively interfere in the targeted heating volume while keeping RF power deposition outside the target to a minimum to preserve healthy tissue This requirement has spurred consideration of the physics and EMF simulations and has motivated the development of RF applicator concepts to advance thermal intervention with the focal point quality being governed by the radiation pattern of the single RF transmit element, the RF channel count, and the thermal intervention radiofrequency of the RF applicator [13,14,15,16]. A number of proposed methods seek to apply array synthesis techniques [31] to directly shape the electric fields in a desirable pattern
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