Using MicroCT Imaging Technique to Quantify Heat Generation Distribution Induced by Magnetic Nanoparticles for Cancer Treatments

Abstract

Magnetic nanoparticles have been used in clinical and animal studies to generate localized heating for tumor treatments when the particles are subject to an external alternating magnetic field. Currently, since most tissue is opaque, the detailed information of the nanoparticle spreading in the tissue after injections cannot be visualized directly and is often quantified by indirect methods, such as temperature measurements, to inversely determine the particle distribution. In this study, we use a high resolution microcomputed tomography (microCT) imaging system to investigate nanoparticle concentration distribution in a tissue-equivalent agarose gel. The local density variations induced by the nanoparticles in the vicinity of the injection site can be detected and analyzed by the microCT system. Heating experiments are performed to measure the initial temperature rise rate to determine the nanoparticle-induced volumetric heat generation rates (or specific absorption rate (SARW/m3)) at various gel locations. A linear relationship between the measured SARs and their corresponding microCT pixel index numbers is established. The results suggest that the microCT pixel index number can be used to represent the nanoparticle concentration in the media since the SAR is proportional to the local nanoparticle concentration. Experiments are also performed to study how the injection amount, gel concentration, and nanoparticle concentration in the nanofluid affect the nanoparticle spreading in the gel. The nanoparticle transport pattern in gels suggests that convection and diffusion are important mechanisms in particle transport in the gel. Although the particle spreading patterns in the gel may not be directly applied to real tissue, we believe that the current study lays the foundation to use microCT imaging systems to quantitatively study nanoparticle distribution in opaque tumor.

Numerical study of nanofluid infusion in deformable tissues for hyperthermia cancer treatments

“…c Shapes of the nanofluid distribution after injection 1% concentration gels [30] gels in a plane perpendicular to the needle track, leading to extended bulk flow in that direction. The microCT imaging [2] confirms that the observed shape of the nanofluid distribution for the infusion rate of 10 ll min -1 is due to the formation of a crack in the gel. Real tissues, on the other hand, can sustain sufficiently high pressure elevation without a breakage.…”

Temperature distribution in multi-layer skin tissue in presence of a tumor

“…The only departure from Section 2.1 comes in the resistor network solution, shown in Eq. (8). In this case, T j,r (x) continues to be given by Eq.…”

“…A significant amount of research in bioheat transfer over the past few decades has led to an understanding of the governing dynamics of thermal transport in a tissue [1][2][3]. A number of thermal based therapeutic measures have been developed and adopted in practice, including laser surgery, cryotherapy, magnetic nanoparticle based hyperthermia and radio frequency ablation [4][5][6][7][8][9]. The design and optimization of these procedures has been aided by advancements in the understanding of bioheat transfer.…”

“…The different theories involved with hyperthermia treatment were verified by performing experiments on a large bovine kidney by turning it into tissue phantom using alcohol fixation technique [28]. Most of these papers investigate therapy of cancerous tissue, including electroporation-based chemotherapy [6,29,30], magnetic nanoparticle based heating [7,8], etc. In a recent study, a high resolution microcomputed tomography imaging system has been used to investigate the concentration and distribution of injected nanoparticles.…”

“…In a recent study, a high resolution microcomputed tomography imaging system has been used to investigate the concentration and distribution of injected nanoparticles. Also nanoparticle induced volumetric heat generation rate was measured experimentally [8]. Several studies on estimating the thermal damage potential due to Joule heating and the importance of considering the multilayer nature of skin tissue have also been presented [6,31,32].…”