MNP-Enhanced Microwave Medical Imaging by Means of Pseudo-Noise Sensing

Abstract

Magnetic nanoparticles have been investigated for microwave imaging over the last decade. The use of functionalized magnetic nanoparticles, which are able to accumulate selectively within tumorous tissue, can increase the diagnostic reliability. This paper deals with the detecting and imaging of magnetic nanoparticles by means of ultra-wideband microwave sensing via pseudo-noise technology. The investigations were based on phantom measurements. In the first experiment, we analyzed the detectability of magnetic nanoparticles depending on the magnetic field intensity of the polarizing magnetic field, as well as the viscosity of the target and the surrounding medium in which the particles were embedded, respectively. The results show a nonlinear behavior of the magnetic nanoparticle response depending on the magnetic field intensity for magnetic nanoparticles diluted in distilled water and for magnetic nanoparticles embedded in a solid medium. Furthermore, the maximum amplitude of the magnetic nanoparticles responses varies for the different surrounding materials of the magnetic nanoparticles. In the second experiment, we investigated the influence of the target position on the three-dimensional imaging of the magnetic nanoparticles in a realistic measurement setup for breast cancer imaging. The results show that the magnetic nanoparticles can be detected successfully. However, the intensity of the particles in the image depends on its position due to the path-dependent attenuation, the inhomogeneous microwave illumination of the breast, and the inhomogeneity of the magnetic field. Regarding the last point, we present an approach to compensate for the inhomogeneity of the magnetic field by computing a position-dependent correction factor based on the measured magnetic field intensity and the magnetic susceptibility of the magnetic particles. Moreover, the results indicate an influence of the polarizing magnetic field on the measured ultra-wideband signals even without magnetic nanoparticles. Such a disturbing influence of the polarizing magnetic field on the measurements should be reduced for a robust magnetic nanoparticles detection. Therefore, we analyzed the two-state (ON/OFF) and the sinusoidal modulation of the external magnetic field concerning the detectability of the magnetic nanoparticles with respect to these spurious effects, as well as their practical application.

Microwave Catheter Navigation System for the Radiofrequency Liver Ablation

“…During the RF ablation, the tissue is locally heated, and this causes changes in dielectric properties. These changes within the considered temperature range are in order of percentages [ 19 , 27 ]. We assume that the amplitudes of UWB signal reflections from the heated regions will be several times lower than the reflections from the metallic catheter, and the detection accuracy will not be influenced.…”

“…Various studies are currently in progress dealing with non-invasive tissue temperature monitoring by UWB radar in hyperthermia [ 19 ] or MW tomography in ablation [ 21 , 22 , 23 ]. Progress has also been made in the field of MW detection of breast tumors [ 24 , 25 , 26 , 27 ], in UWB radar tomography [ 28 ], and the field of stroke detection by MW tomography [ 29 , 30 ]. Based on the considerable advances in microwave imaging, it can be assumed that this technology could be used to determine the exact position of the ablation catheter in the patient’s body with high precision.…”

Temperature dependence studies of tissue-mimicking phantoms for ultra-wideband microwave breast tumor detection

“…From the porcine tissue measurements it can be derived that temperature has a significant effect on the permittivity of biological tissue, cf [32,33] and can thus potentially be used as a contrast mechanism for diagnostic purposes. This approach would exploit the physiological properties of the human body and would not require the use of externally supplied artificial contrast agents such as nanoparticles [34,35].…”

Configurable Pseudo Noise Radar Imaging System Enabling Synchronous MIMO Channel Extension

“…Additionally, in medical imaging, the radar principle can be used to screen through layers of human tissue. That way, using conformal antenna arrays, arterial movement covered by the human skull may become visible [6], or cancerous tissue may be found by employing magnetically stimulated nano particles [7,8].…”