What material is primarily used in a direct conversion system?

In a direct conversion system for digital radiography, the primary material used is amorphous selenium. This choice is correct because amorphous selenium effectively converts X-ray photons directly into an electrical signal. This process allows for higher image resolution and improves the quality of the resulting images.

Amorphous selenium has properties that facilitate the immediate conversion of radiation into electric charge without the need for an intermediate step, such as light, which is employed by indirect conversion systems. This direct conversion method is advantageous in terms of speed and efficiency, as it minimizes signal loss and preserves image quality.

Other materials listed, such as cesium iodide, are primarily used in indirect conversion systems, which first convert X-rays into light before translating that light into an electrical signal. Therefore, while they are valuable in digital radiography, they do not serve the same function as amorphous selenium in a direct conversion system. The other materials like lead zirconate titanate serve different uses in imaging technologies and are not involved in direct X-ray conversion.