Digital Radiography (DR) frequently uses Flat Panel Detectors (FPD). Inside these detectors is a layer of material known as a scintillator. Scintillators, which turn x-rays into light, were once referred to as “screens” when they were in film cassettes. The basic concept is still the same. However, digital x-ray requires much brighter light than that you get with cassette screens, and the materials used are not the same. In digital x-ray, the two materials used are Cesium Iodide (CsI) and Gadolinium Oxide. (GadOx).
Let’s first take a look at CsI. Panels comprised of CsI typically yield more detailed, higher resolution images. These panels also have better light output. Since CsI panels are more sensitive to dose levels, there’s typically a reduced radiation dose of about 10% or so between CsI and GadOx.
GadOx, on the other hand, which is great as a scintillator in panels for certain applications, also produces high image quality. However, when compared to CsI by a trained eye, a difference can be seen between the two compounds. One factor in which GadOx does beat CsI is in cost, as GadOx FPDs come with a lower price tag.
While GadOx seems appears to be a worthy opponent, it’s clear that CsI is the preferable of the two compounds. In fact, some argue that CsI is the highest level of technology used to reduce the radiation dose required for each x-ray shot while also achieving clean, higher resolution images.
Whether you go with a detector using CsI or GadOx, the following fast facts are good to know:
Thicker scintillator layers increase the amount of x-ray conversion to visible light, which leads to good absorption efficiency.
Thick layers of scintillators increase the amount of scatter, which decreases contrast.
Thin scintillators have lower absorption efficiency but better spatial resolution.