Maximal segment pair

The precision of the RSA method is dependant on the number of tantalum beads, the degree to which they are distributed three dimensionally, as well as their relative distance to the other object or segment. While in theory each patient would have a unique measurement precision, in reality good precision can be achieved by maximizing the number of beads (a minimum of three) and by having them sufficiently disbursed so they do not fall in a single line or plane. The precision of an RSA smdy can be determined by the use of a double examination where two pairs of films are acquired on the same day [74]. The measured motion between these double examinations represents the error. A standard deviation of the error of the double examinations for aU patients in a study can then be used to calculate a 95% or 99% confidence interval, which represents the precision of the study group. 

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