But we have a hint that they do. That hint is provided in an article by Joel E. Gray, Ph.D., who was Prof. of Medical Physics at the Mayo Clinic until his recent retirement. That dose is just inside the First Quartile in our table. While Dr. Gray does not explicity say that image-quality on spine films is good at the Mayo Clinic, it seems safe to assume that quality is very good, because of the Mayo Clinic's reputation for excellence. What we can say, logically, is that if any x-ray practitioners in the First Quartile can obtain very good images, then all practitioners could do it.
Poor quality causes re-takes and additional exposure.
The measurements are made at each facility on a dummy of standard size. The reports do not identify where the measurements were made. From the table, it is clear that x-ray practitioners who use all the procedures can give doses which are 10 or 20 times lower than practitioners who use none of them. Unfortunately, the two articles are very hard to obtain, and they probably have been seen by almost no one in medicine and certainly not by the public. NCRP Report 100.