Geometric reconstruction of seed implants using a three-film technique

A computer program has been written to reconstruct the three-dimensional distribution of radioactive seed implants. The technique requires the use of three rotated films with random input of the seeds. This algorithm differs from previous ones in the constraints that are applied, since no correlation is made between distances on the three films from the plane of rotation through the isocenter nor is there a correlation between the distances from the axis of rotation. Instead, projections from the x-ray source to the seed images on each of the three films are compared to see which combinations of seeds intersect at a point and therefore correspond to real seeds. This program has been written in Fortran IV for the PDP VAX 11/780 and 11/34 computers. Changes have been made to the TP11 program "QSEED" on the PDP 11/34 to accommodate the coordinate data from this program to produce the requisite isodose curves.