QUATRO audits help radiotherapy centres attain the best level of practice possible for their economic circumstances. They assess: the radiotherapy infrastructure; patient and equipment procedures; radiation protection aspects; staffing levels; and professional training programmes for the local radiotherapy staff. An audit is carried out by a multidisciplinary team of experts, typically comprising a radiation oncologist, a medical physicist and a radiation therapist.

The QUATRO methodology gives guidance on the implementation of such audits.

Audits usually conclude with a written report that assesses the current radiotherapy practices and makes recommendations for improvement. Such reports are then submitted to the assessed facility. It is important to note that an audit is specifically not designed for regulatory purposes and the auditors have no power to enforce any actions based on their assessment. They can only report their findings and give recommendations, which the audited facility is free to implement or not, as they wish. Notwithstanding this, QUATRO audits have overall contributed to significant improvements.