MRI guided high intensity focused ultrasound (HIFU) has great potentials for imaged guided thermal therapy due to MRI’s unique capability of providing accurate and real-time target localization and temperature monitoring [1, 2].In order to avoid ultrasound field interference, surface coil placed between ultrasound focal spot and transducer becomes a broadly used setup [3, 4].In this work, we propose a 3 channel ultrasound compatible rat array to obtain high resolution and homogeneous rat brain images at 3T for temperature monitoring. Both phantom and in-vivo imaging experiments in temperature mapping are carried out to evaluate the performance of the design.Experimental setup and array structure: as shown in Fig. 1, the head of anesthetized rat (or phantom) was positioned supine in the proposed array. In order to well couple to the transducer, the rat/phantom and array was placed above a tank with de-gassed water. The proposed ultrasound compatible rat array consisted of 3 loops, two 50 mm ×60 mm rectangle loops on the top and one circular loop with 55 mm diameter at the bottom. Ultrasound wave propagated across the bottom loop. All of the three loops were tuned and matched at 123.2 MHz, the 1H frequency of our 3T MR scanner. The decoupling of the top two loops was achieved by overlapping while the top loop and bottom loop were capacitance decoupled. Low input impedance preamplifiers were used to further improve element decoupling. Phantom study: A gradient echo (GRE) sequence is utilized to investigate the coverage and homogeneity of the proposed array. Images of transverse, coronal and sagittal planes are acquired. In-vivo study: In order to evaluate the array performance in the in-vivo case, the T1- and T2- weighted 2D fast spin echo sequences are utilized to acquire high resolution rat brain images. Temperature mapping study: In-vitro MRI guided HIFU ablation experiment is performed on a piece of porcine muscle. During the HIFU ablation, GRE based temperature mapping sequence [5] was carried out continuously to monitor the temperature variation and distribution in the porcine muscle. All above studies are performed on Siemens 3T TIM Trio (Siemens, Erlangen, Germany) system with imaging parameters shown in Table 1.Fig. 2. shows the phantom images on the transverse, coronal and sagittal planes respectively. The images demonstrate that the proposed array provides sufficient coverage and homogeneity in the rat brain region. T1- and T2- weighted rat brain images with 0.23 mm × 0.23 mm × 1 mm and 0.2 mm × 0.2 mm × 1 mm resolution respectively are shown in Fig. 3. The high spatial resolution rat brain images demonstrate the capability of the array to provide high signal-to-noise ratio, which is critical to obtain high quality anatomic images and accurate temperature measurement [5]. In Fig. 4, the temperature variation on the focal spot during the three stages is shown. At the moment that the ultrasound turned off, the temperature variation distribution is calculated via phase image and registered to the anatomic image, in which the location of the focal spot is identified. The results demonstrate the capability of the proposed array to carry out temperature mapping for MRI guided HIFU treatment.The proposed 3-channel ultrasound compatible rat array is capable of providing homogenous and high SNR images in the whole rat brain at 3T. By using this array, high resolution whole rat brain image scan be obtained and temperature mapping can be carried out, which provides the possibility to perform MRI guided HIFU treatment in-vivo.