Signal processing apparatus, signal processing program, and a signal processing program and computer readable recording medium

A signal processing apparatus for processing a fluoroscopic image represented by transparent superposition of the different background portion directed portion and the target portion, such as a diseased part for a plurality of times, acquiring the fluoroscopic image including the target portion the target portion and the background portion and the fluoroscopic image acquiring unit, a component of the transmitted image due to the components due to the target portion and the background portion at time t certain of said plurality of times, in the plurality of times that calculated in association with the estimated value of the distribution information, and calculating section that evaluates the consistency between the fluoroscopic image in the plurality of times, based on the evaluation result of the calculation unit, the target portion or the in the time t and an updating unit for updating the estimated value of the distribution information of the background portion.