| 摘要 |
<p>In transversal computer tomography apparatus, in which the positioning zone in which the patient can be positioned is larger than the scanning zone in which a body slice can be scanned, due to incomplete irradiation of the body during examination reconstruction errors are liable to occur. These errors can be reduced in that a sum of measuring values of a measuring series is formed and that difference between each sum and a maximum of all sums is determined, whilst in the case where at least one of the differences thus formed deviates from zero, a priori values are formed to complement the measuring values, so that for each beam direction, the sum of the a priori values corresponds to the difference determined for this direction or measuring series, each a priori value for each time one direction being proportional to the length of a beam extending through the body outside a scanning zone in this direction. This length corresponds to the distance between two points of intersection of the beam and the edge of the body. This edge being determined as the envelope of all beams which are tangent to the body inside the scanning zone, or as an extension of the envelope which is determined by interpolation. The reconstruction of the absorption distribution inside the scanning zone is realized on the basis of the measuring values and the a priori values.</p> |
