## 1 Introduction  
Peclinical animal models play an important role in understanding of human disease. It is applied to a variety of research, ranging from diagnosis methods and treatments for diseases. Especially Magnetic resonance imaging (MRI) is a medical imaging method that allows the acquisition of anatomical images from small animals [1, 2, 3]. MR images can be employed to diagnose cancer and tumor tissues [4, 5, 6, 7]. In addition, MRI is 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]. The results of previous works [15, 16] indicate the usefulness of heat treatment induced into tumor cells of small animals through a heating system. In previous studies, focusedultrasound, radiofrequency (RF) and microwave (MW) were used as heating systems that can be combined with MRI systems [17; 18; 19; 20; 21]. Specifically, RF or MW energy is applied to the target area in the form of an electric (\(\ket{\mathrm{I}\ket{\mathrm{I}}}\)-field through various types of antennas such as slots, dipoles, bow ties, etc. [18; 19; 20; 21; 22] to induce a temperature rise of \(\sim\)43 \({}^{\circ}\)C or higher in the target tissue. In combination with radiotherapy and/or chemotherapy the hyperthermia treatments with an increased exposure time has shown to produce constant cell death rate [22]. In ref. [19] it is shown that the use of a Yagi-Uda antenna for hyperthermia applications operating at 433 MHz, it exhibited low coupling with the imaging RF coils operating at 64 MHz. This is an important aspect when designing an RF transmitter for hyperthermia. Similar to Yagi-Uda antennas, Patch antennas are a type of electromagnetic field generator that consist of a dielectric material placed between the ground and patch plane. At frequencies above 400 Mhz, there are also studies for the purpose of thermal treatment of patch antennas [23; 24; 25]. Even though these studies were combined with an MRI system, MR images acquisition and heating were operated separately. MR image acquisition and heating using the SAR value for a bow-tie antenna that can operate in two ways has been proposed [21]. In this study, we present a dual-purpose patch antenna that can be used for MRI imaging and RF heating hyperthermia. To do that, we need to solve a few problems. The first problem is that at 300 MHz, the 7T MRI operating frequency, the size of the antenna is too large to be applied to small animals. The second issue is the \(\ket{\mathrm{B}_{1}}\) -field profile according to the orientation of the antenna, as the \(\ket{\mathrm{B}_{1}}\) -field consists of the \(\mathrm{B_{x}}\) and \(\mathrm{B_{y}}\) components of the magnetic field. For MRI, RF coils that can transmit and receive a uniform and strong \(\ket{\mathrm{B}_{1}}\) -field are preferred. If the antenna is placed on the \(z\)-\(y\) plane, as is common for any RF coil, the \(\ket{\mathrm{B}_{1}}\) -profile has a low intensity because the major component of the magnetic field in this orientation is the z component of the magnetic field \(\ket{\mathrm{B}_{z}}\), which is not part of the \(\ket{\mathrm{B}_{1}}\) -field.