Method for computed tomography

A method for determining the spatial distribution of the absorption of radiation in a slice of a body comprising the steps:

• irradiating the body from a plurality of different positions along a plurality of measuring beams which pass through a scanning zone, the slice of the body being completely irradiated by radiation from at least one of the positions and being less than completely irradiated by radiation from at least one other of the positions;
• measuring the integral of the absorption of radiation by the body along each of the measuring beams to produce measuring values, a measuring series comprising the set of all measuring values produced by radiation from a single position;
• forming the sum of the measuring values in each of the measuring series;
• identifying the maximum of all of said sums;
• determining the difference between each of said sums and the maximum sum;
• forming, in the case where at least one of the differences deviates from zero, a priori values so that for each measuring series the sum of the associated a priori values corresponds to the difference between the sum formed for that series and the maximum sum, each a priori value being proportional to the length of a beam extending through the body from the corresponding position, which length corresponds to the distance between the points of intersection of the associated beam and the edge of the body, said each being determined as the envelope of all beams which are tangent to the body inside the scanning zone and as an extension of the body which is determined by interpolation;
• and
• reconstructing the absorption distribution inside the scanning zone, by the methods of computed tomography, utilizing both the measuring values and the a priori values.