Radiation therapy is used to treat over 60% of cancer patients and is used in nearly half of the curative cases, however, in low- and middle-income countries (LMIC), there is a large underserved population, with technology per capita 2 or more orders of magnitude lower than in the US. Many LMIC still utilize outdated Cobalt-60 machines, which result in excessive normal tissue dose, present safety hazards, and are at risk for diversion for terrorist purposes in radiological dispersal devices (aka “dirty bombs”). The barriers to wider adoption of modern linear accelerator technology are primarily due to the high capital and operating costs and requirement for highly- trained personnel. In addition, state-of-the-art medical linacs have very high peak and average electrical draws, and require stable, reliable power that is often unavailable in LMIC. This project will address these issues with a novel medical linac platform that will be designed from the ground up to be robust, reliable and efficient. The system is based on the novel 4π radiotherapy technique developed at UCLA. It utilizes an industrial robot and allows automatic generation and delivery of high-quality treatment plans. A reliable sparse orthogonal collimator will replace the failure-prone multileaf collimator. Finally, it will incorporate a linear accelerator and RF power system design that is optimized for power efficiency and low cooling requirements. In Phase I of the SBIR project, the efficient accelerating structure and RF power system will be designed and optimized to minimize power consumption and cooling requirements. The simplified, yet clinically superior, sparse orthogonal collimator will be engineered. Finally, the automated treatment planning software will be developed. There is a compelling humanitarian and economic case for increasing access to radiotherapy. Millions die every year in the developing world from cancers that could have been successfully treated by radiation therapy, and it is estimated that the return on investment in radiotherapy can exceed $500 billion globally in 2015-2035 and save 27 million life-years. The team behind this proposal has already started the process of raising private capital for the development of this novel, simple, yet clinically superior radiotherapy system. The business plan projects $674 million in sales during the first 10 years of commercialization. The global radiotherapy equipment market was $4.9 billion in 2014.