Patent Document ID: 5528649
Application ID: 07979471
Patent Flag: 1

Claim One:
1. A method of calibrating a radiological system for examining an object (13) wherein the system is of the type including an X-ray tube (11) having a supply voltage V adjustable to various different values V.sub.m either continuously or discretely, the tube emitting a beam of X-rays in the form of bursts of variable duration S, and having an anode current I, and a detector cell for detecting X-rays that have passed through the object to be examined and for converting a physical magnitude characteristic of the beam of X-rays into a measurement signal M such as an electrical signal, the method comprising the steps of: (a) selecting a physical magnitude A which is characteristic of the object to be observed; (b) choosing a class of reference objects including n phantoms exhibiting n known values of the same physical magnitude; (c) selecting j values V.sub.m of the supply voltage for the X-ray tube (11) at which calibration is to be performed; (d) selecting a value of the product IS of the anode current I drawn by the X-ray tube during the exposure time S for each phantom associated with each value of the supply voltage V.sub.m ; (e) installing a phantom in the path of the X-rays, adjusting the tube voltage to a value V.sub.m, and integrating the radiation (16) that passes through the phantom as detected by the detector cell between the beginning of measurement and the instant at which the product IS is equal to the value selected in step (d), thereby obtaining a measurement M; (f) calculating the efficiency D as given by the ratio M/IS; (g) reiterating operations (e) and (f) for the same phantom for each of the (j-1) other selected values of the supply voltage V.sub.m ; (h) reiterating steps (e), (f) and (g) for the (n-1) other phantoms; (i) using a conventional estimation method, determining the analytic model D=f(V.sub.m, A) relating the values of efficiency D to the values of the physical magnitude A and of the supply voltage V.sub.m ; and (j) determining the inverse function of f(V.sub.m, A) written g(V.sub.m, D), thereby enabling A to be determined with known values of V.sub.m and D.