This study is to demonstrate the feasibility of novel MRI-guided ultrasound stimulated microbubble treatment to enhance radiation effects in humans receiving external beam radiotherapy delivered using a LINAC (linear accelerator) radiation therapy device. The investigators have previously demonstrated that ultrasound and microbubble mediated endothelial cell perturbation can significantly enhance the effectiveness of radiation. It enhances tumour response to radiation significantly by synergistically destroying tumour blood vessels. The technique is targeted spatially and achieves tumour specificity by confining the low-power ultrasonic fields that stimulate microbubbles to the tumour location only. By perturbing the tumour vasculature and activating specific genetic pathways, the technique sensitizes the targeted tissues to the subsequent therapeutic application of radiation, resulting in significantly enhanced cell killing. The primary aim of this research is to evaluate the safety profile of MRI-guided ultrasound stimulated microbubble treatment and radiation in patients with head and neck cancer. The secondary aim is to evaluate tumor (primary and/or nodal) response to MRg-FU + MB and radiation, as measured radiologically within the treated therapeutic regions.