What materials are commonly used as interspace materials in grids?

Interspace materials in grids play a crucial role in radiographic imaging by helping to absorb scatter radiation. The correct answer is aluminum and air because these materials effectively provide the necessary support and separation between the lead strips of the grid. Aluminum is lightweight yet sturdy, allowing it to maintain the structural integrity of the grid while facilitating the passage of the primary beam. Air serves as an excellent interspace filler since it reduces the overall weight of the grid and minimizes the scatter that can occur in the interspace area.

In comparison, while lead and rubber may have specific applications in radiation shielding or patient care, they do not provide the optimal combination of support and scatter reduction found with aluminum and air. Materials like cardboard and plastic are not typically durable enough to withstand the rigors of radiation exposure and mechanical manipulation involved in imaging procedures. Glass and copper are also unsuitable; glass is too fragile for use in grids and copper cannot effectively serve as an interspace material due to its weight and potential for causing more scatter rather than absorbing it. Thus, aluminum and air are the preferred materials for their effectiveness in radiographic grids.