| abstract |
In the field of X-ray apparatuses which use rotatable collars to carry at least a source of X-rays in rotation around a patient, the positional alignment between the collar and the patient is critical to the accuracy of the information. Typically this alignment has been provided through the use of a large, precision mechanism for handling the rotatable collar. The present invention provides a stationary reference (42, 66, 118), and apparatus (40, 24, 70, 72, 134) for determining the positional relationship between the rotatable collar (12, 60, 116) and the stationary reference (42, 66, 118). |