According to an embodiment of the invention, a method and apparatus for signal modulation are described. In the technique, the dual-energy X-ray imaging system utilizes a slit collimator to expose a series of portions of a region of interest within a patient with X-rays of two different energies. The modified cyclic aliphatic polyamine thus obtained is added in epoxy resin to be used as a curing agent for epoxy resin. The crown portions of the deposition sections are arranged consecutively in side-by-side relationship along a circumferential extension of the toroidal support.