The orthogonal projection or view is, by definition, a radiographic projection obtained 90° from the original view. It forms the basic requirements of a 'radiographic series', having 'two orthogonal projections of the region of interest'. The importance of two views has been known for many years ¹ as a single view can potentially miss pathology obvious on a second view.

Acute imaging 

Cases can appear normal in one projection and abnormal in the next. Consequently, plain radiographic imaging in the acute setting is seldom a single projection, often comprising of two or more angles of the same region. Orthogonal projections in the acute setting are necessary to convey the three-dimensional nature of the anatomy in question. 

One should always strive to perform (as radiographers) or request (as referrers) orthogonal views. When orthogonal views are not possible, views taken at an alternative angle to the first are still more beneficial than no second view at all.

Foreign body imaging

Plain radiographic investigations of foreign bodies often require orthogonal projections to better understand the position in relation to anatomical structures. The orthogonal projections of foreign bodies can include the 'en face' or 'tangential' projection, whereby the radiographer performs imaging orthogonal to the foreign body rather than anatomical structures.

See also

• radiographic positioning terminology