Publications [#268571] of James T. Dobbins

Papers Published
  1. Peppler, WW; Kudva, B; III, JTD; Lee, CS; Lysel, MSV; Hasegawa, BH; Mistretta, CA, DIGITALLY CONTROLLED BEAM ATTENUATOR., Proceedings of SPIE - The International Society for Optical Engineering, vol. 347 (1982), pp. 106-111 .

    Abstract:
    In digital fluorographic techniques the video camera must accommodate a wide dynamic range due to the large variation in the subject thickness within the field of view. Typically exposure factors and the optical aperture are selected such that the maximum video signal is obtained in the most transmissive region of the subject. Consequently, it has been shown that the signal-to-noise ratio is severely reduced in the dark regions. The authors have developed a prototype digital beam attenuator (DBA) which will alleviate this and some related problems in digital fluorography. The prototype DBA consists of a 6×6 array of pistons which are individually controlled. A membrane containing an attenuating solution of (CdCl3) in water and the piston matrix are placed between the X-ray tube and the subject. Under digital control the pistons are moved into the attenuating material in order to adjust the beam intensity over each of the 36 cells. The DBA control unit which digitizes the image during patient positioning directs the pistons under hydraulic control to produce a uniform X-ray field exiting the subject. The pistons were designed to produce very little structural background in the image