Canadian CT head rule

The Canadian CT head rule (abbreviated CCTHR or CCHR; also sometimes referred to as the Canadian Computed Tomography Head Rule) is a medical scale used to decide whether patients with minor head injuries should undergo cranial CT scans. It was originally described by Stiell et al. in a paper published in "the Lancet" in 2001, in which they initially used it only on patients with Glasgow Coma Scale scores of between 13 and 15. Since then, the CCTHR has become the most widely researched and extensively validated rule of its kind, though a 2011 systematic review noted that "its exclusion criteria make it difficult to apply universally."
Criteria.
The CCTHR excludes patients who:
Under the CCTHR, patients with minor head injuries should only receive CT scans if one or more of the following criteria are met:
The first five criteria are considered "high-risk", whereas criteria 6 and 7 are considered "medium-risk".