| 摘要 |
<p>A part of the vascular system which may be considered to consist of an entrance vessel (33), a reservoir (37) and an exit vessel (35) is arranged in an apparatus for making subtraction images by means of penetrating radiation, a contrast medium which absorbs radiation being introduced into the entrance vessel (33). During the flowing of the liquid mixed with contrast medium from the entrance vessel (33), via the reservoir (37), to the exit vessel (35), a serie of subtraction images is made. For successive subtraction images having the ranks n and n+1 in the serie a part (43) of the entrance vessel (33) which adjoins the reservoir and a part (45) of the exit vessel (35) which adjoins the reservoir are determined for which the equation DELTA TDres(n) = TDin(n)-TDex(n+1) is satisfied, where TDg(n) is defined as the total radiographic density of a region g in the subtraction image having the rank n, where DELTA TDres(n) is defined as DELTA TDres(n) = TDres(n+1)-TDres(n) and where the suffices res, in and ex refer to the reservoir, said part of the entrance vessel, and said part of the exit vessel, respectively.</p> |
