1. A method for producing a shaded image from data acquired with a nuclear imaging tomographic scanner, the steps comprising: (a) acquiring a sequence of two-dimensional frames of nuclear event data which is reconstructed to form a three-dimensional array of data V(x,y,z) which indicates the number of nuclear events at a three-dimensional matrix of points throughout a volume of interest; (b) extending into the volume of interest a projector from a pixel in a projection plane to determine the distance between that pixel in the projection plane and the boundary of an object within the volume of interest, including the steps of: (i) extending the projector an incremental distance away from the projection plane, (ii) calculating the number of nuclear events at the current position of the projector from the three-dimensional array of data, V(x,y,z), (iii) comparing the calculated number of nuclear events with a pre-established threshold value, (iv) reiterating steps i-iii if the threshold value is not reached, otherwise, (v) calculating the location at which the projector intersects the object's boundary by interpolating between the current calculated number of nuclear events and the calculated number of nuclear events from the previous iteration to arrive at a location between the projector's current position and its position for the previous iteration; (c) producing a two-dimensional array of distance data D(z,y) by repeating step (b) for each pixel in the projection plane; and (d) producing a two-dimensional display data array DS(z,y) by assigning a brightness value to each element in the display data array which is a function of the distance value of its corresponding element in the distance array D(z,y).