Robot-assisted stereotactic body radiation therapy (rSBRT) is a modern irradiation technique for small tumors. Highly hypofractionated doses with steep gradient and high conformity are delivered with a robotic arm based linear accelerator (CyberKnife^®). In Hungary, SBRT can be performed with conventional linear accelerator (LINAC), gamma knife or CyberKnife (CK). CyberKnife is a special SBRT delivery system that utilizes a robotic arm to precisely irradiate tumors, offering a non-invasive alternative to traditional surgery. The aim of the PhD research is to analyze the image guidance of CyberKnife and in addition to determine the safety margins for the target volumes. A further objective is to investigate the efficiency of treatment planning methods and to compare different dose calculation algorithms implemented in the treatment planning system. Furthermore, to perform dosimetric analysis of SBRT performed with a conventional linear accelerator and CyberKnife according to international SBRT clinical protocol such as the RTOG recommendation. SBRT technique relies on advanced imaging technologies such as CT or MR imaging to define the location and shape of the tumor. The use of MR images is required in many regions such as the brain, head-and-neck, liver and prostate. Therefore, well-developed MRI protocols are also needed in clinical work for radiotherapy.