Foamed epoxy resin-based lung substitutes

A variety of materials have been introduced over the years to simulate lung tissue, with both foamed and granulated products being used (Edling, 1944; Alderson et al, 1962; Rogers, 1970; Stacey, 1972; McGinley, 1973; White, 1974; Constantinou, 1978). Unfortunately, many available lung substitutes have imprecise or variable elemental compositions. In addition, complex manufacturing procedures are frequently necessary in order to produce the required material.

In this note a range of foamed lung substitutes based on an epoxy resin system are discussed. The substitutes have well defined elemental compositions and radiation interaction characteristics for photons and electrons that closely match those of the lungs. By careful addition of a special foaming agent, the mass density of the final material may be at any derived value within the quoted mass density range of the inflated/deflated lung (260–1050 kg m⁻³) (International Commission on Radiological Protection (ICRP), 1975).

It should be noted that the materials presented here use the same foaming agent (Dow Corning, DC 1107) as that described by Constantinou (1978) in his Ph.D. Thesis.

The use of epoxy resin systems in the manufacture of tissue substitutes was discussed in detail by White et al (1977), when 15 substitutes were introduced, including a lung material designated LN4. The formulation LN4 represented the lowest-density material that could be produced at that time by loading the epoxy resin system, CB2, with the low-density filler, phenolic microspheres (PMS). The resulting mass density of 600 kg m⁻³ was higher than the lowest reported density of the inflated lung.