Near-field thermoacoustic tomography of small animals

Abstract

Near-field radiofrequency thermoacoustic (NRT) tomography is a new imaging method that was developed to mitigate limitations of conventional thermoacoustic imaging approaches, related to hard compromises between signal strength and spatial resolution. By utilizing ultrahigh-energy electromagnetic impulses at ∼20 ns duration along with improved energy absorption coupling in the near-field, this method can deliver high-resolution images without compromising signal to noise ratio. NRT is a promising modality, offering cost-effectiveness and ease of implementation and it can be conveniently scaled to image small animals and humans. However, several of the performance metrics of the method are not yet documented. In this paper, we characterize the expected imaging performance via numerical simulations based on a finite-integration time-domain (FITD) technique and experiments using tissue mimicking phantoms and different biological samples. Furthermore, we show for the first time whole-body tomographic imaging results from mice, revealing clear anatomical details along with highly dissipative inclusions introduced for control. The best spatial resolution achieved for those experiments was 150 µm.

An Integrated Simulation Approach and Experimental Research on Microwave Induced Thermo-Acoustic Tomography System

“…Thermo-acoustic pressure waves, induced via local heat deposition by microwave energy absorption, can be described via the thermo-acoustic wave equation [16,17], i.e.,…”

“…Thus, the thermal confinement condition [14] is satisfied. Under thermal stress confinement, the heating function can be rewritten in a form with product separated contribution of the spatial H( r) and temporal δ(t ) parts [16,17].…”

“…Therefore, calculating heating function of biology tissue is the first step to perform the simulation. Finite integration time domain (FITD) method is an efficient numerical method in analyzing electromagnetic (EM) problem [16]. It operates with discretizations of the integration form of Maxwell's equations.…”

“…Some experimental MITAT systems have been developed and been reported [12,13,[15][16][17]. In order to validate the performance of the integrated simulation approach, we have developed a MITAT system.…”

“…Two-and three-dimensional (2-D and 3-D) imaging of breast tissue phantoms or real breast tissue specimens have been investigated [14][15][16][17]. In the study of MITAT techniques, a fast and accurate simulation approach is necessary to help designing and optimizing system.…”