Scanning

#The present invention relates to the examination of an object by successively scanning the latter by means of a wave radiating beam, the orientation of which is modified from one scan to the other.

#The internal structure of the object is deduced from the measurement of the absorption undergone by the beam.

#This type of examination is used particularly in medicine for the examination of the brain.

#The understanding of the invention will be facilitated by the following description and the figures wherein:

#FIG. 1 is a diagram illustrating the scanning principle of the object effected in the system to which the invention refers;

#FIG. 2 is the principal diagram of an improved examination device according to the invention;

#We see in FIG. 1 in E and R respectively the sound transmitter and sound receiver of a "transgraphic" system, that is, radiography by conventional transmission. These sounds are placed facing each other on either side of the examiner object O. The sound transmitter E transmits a fine beam extending along the axis ZZ connected to sound transmitter E. The radiation can be of any type (X-rays, ultrasonic, infrared..), it being important only that the radiation received in receiver R is as fine as possible. The amplitude A of the radiation received in receiver R is permanently measured. The characteristic parameter of the structure of the object O being the ratio A/Ao, where Ao is the amplitude of the transmitted radiation, it being indispensable, if the single measurement of A is to be sufficient to characterize the object, that Ao is rigorously constant. One could free oneself of this limitation at the expense of measuring circuits for Ao and calculating the ratio A/Ao, circuits whose assembly would be more complex than those necessary for the regulation of the transmission. The probes E and R are displaced simultaneously in the same plane along two lines X perpendicular to the axis ZZ, so that the beam scans the entire object O. After each scanning, the axis ZZ is turned by an angle .DELTA..theta. and a new scanning is effected. The same operation is repeated n times (n equals any integral number, generally over 100), until the axis ER has turned by a total of 180.degree.. For example, we assume .DELTA..theta. = 1.degree., and n = 180. In the drawings we have represented in solid lines the translation axes X of the sounds at the origin, and in broken lines the translation axes Xl after the elementary rotation of the assembly of .DELTA..theta. and in dot-dashed lines the position of the axes Xp for p rotations (p less than n), the sounds being then in E'p and R'p on the axes Xp. We could also rotate the assembly rapidly and displace E and R of .DELTA.X at each revolution.

#The principle of this examination is thus as follows: In the course of each scanning, the variations of the amplitude A of the radiation received are due to the partial absorption of the radiation by the structures traversed by the latter. In a given point P of the trajectory of the rays, that is, on the segment of the axis ZZ comprised between E and R, in a distance Y from the axis X, for a position of the assembly E and R defined by the abscissa X, counted from any fixed origin on the axis X, this absorption is the sum SIGMA (.SIGMA.) of all the elementary absorptions da corresponding to each of the structures comprised between E and P or ##EQU1## where O is less then Y which is less than or equal to Y,y being the distance from the axis X or any pointed between E and P, and Y being the thickness of the object perpendicular to the axes X. This sum is a function of X and of .theta.. Since the measured amplitude is A = Ao/.SIGMA.; SIGMA (.SIGMA.) is a function of the X coordinate of E on the axis X, and of .theta.; Ao is constant.

#We have at the end of the examination of n functions of the form A(X,.theta.). The exploitation of this examination consists in translating these functions into coefficients of absorption for each point of the structure O.