Abstract
The popularity of patch antennas in magnetic resonance imaging (MRI) has reduced because of the large size required for patch antennae to resonate. Since the size of the patch antenna is associated with the wavelength and the wavelengths that are used in MRI are substantially large, large antennas are used. Methods of reducing patch antenna sizes have been proposed; however, these methods reduce the penetration depth and uniformity. In this study, we reduced the area of the patch antenna by 30% by folding the ground and patch planes in a zigzag pattern. The patch antenna produced two main resonant modes. The first mode produced a uniform magnetic field that was used for MRI. The second mode produced a strong and focused electric (|E|)-field, which was used for radiofrequency (RF) heating. Furthermore, we explored the use of a combination of two patch antennas aligned along the z-axis to provide a circular uniform magnetic flux density (|B1|) field at 300 MHz, which corresponds to the Larmor frequency in the 7T MRI system. In addition, the patch antenna configuration will be used for RF heating hyperthermia operating at 1.06 GHz. The target object was a small rat with insertion of colon cancer. Using the proposed configuration, we achieved |B1|-field uniformity with a standard deviation of 3% and a temperature increment of 1 °C in the mimic cancer tissue.
Highlights
Preclinical animal models play an important role in understanding of human disease
Magnetic resonance imaging (MRI) is a medical imaging method that allows the acquisition of anatomical images from small animals [1,2,3]
MRI is the predominant method for performing non-invasive temperature measurement during hyperthermia treatments [8,9,10,11,12]
Summary
It is applied to a variety of research, ranging from diagnosis methods and treatments for diseases. MRI is the predominant method for performing non-invasive temperature measurement during hyperthermia treatments [8,9,10,11,12]. Scientists study cancer properties and treatments using ultra-high field MRI, and preclinical studies in controlled environments are usually performed with small animals such as rats and mice [12,13]. In order to provide a stable hyperthermia protocol in clinical practice, it is necessary to accurately measure changes in energy transfer parameters (applied power level, heating duration) in small animal experiments, for which we integrate a system of heating and temperature monitoring. Most heating experiments of small animal integrated with MRI have been implemented in clinical MR scanners. Since the animal MRI system has a smaller bore size than the clinical MRI system, there is a technical limitation in integrating it with a heating device in the limited space [14]
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