Anterior-Posterior Exposures 
X-ray view from front to back. This view is becoming more widely used as airway development and suture expansion increases. 

Collimator 
Actually a beam limiter since they do not make X-ray beams parallel. Their function is to line up the central beam and variable apertures. Variable apertures are best because they can be adjusted to fit the application, and can be moved to a different X-ray head. 

Installation 
Most walls and corners are slightly crooked. X-ray beams are absolutely straight. Coordinating the two can be tricky. Look for units with plenty of adjustability, and a mounting system that is simple. 

Wall Mount Units 
Attach to wall and do not move. The patient is moved up and down to fit the unit. Uses Standard dental X-rays. More inconvenient than moveable units, but a practical solution in general offices, due to cost. Consists of two parts, head-film holder + beam limiter - X-ray aimer. Be sure both units can be easily removed from wall to avoid interfering with other operatory functions. 

Ease of Operation 
Except for the first film or two, your assistant will be using the Cephalostat. Be sure it is easy to use and difficult to misuse. Be wary of superfluous adjustments and gadgets. Look for knobs on things she should adjust, and screws and nuts on things she shouldn't. 

Midline Fixation 
It is important to maintain a consistent distance between X-ray source, midline, and the film. This requires a Cephalostat with a midline centering system and a pre-set X-ray to film distance. 

Ear Rod Supports 
The vertical pieces holding the ear rods are usually wood or plastic. Wood is best because it shows least on the film. The more highly finished the supports, the more they show on the film. 

Back-up Service 
Each installation is unique. Most installations go easily and require no help. Look for a system that offers help after the sale to answer installation questions.