Chapter 6 - Cassetteless Equipment and Image Acquisition

Digital radiography (DR)

It is another way to record x-ray exposure after it has passed through the patient.

Digital radiography (DR)

It is used to describe images recorded on an electronically readable device.

Thin-film transistor (TFT)

It may be used in both direct- and indirect-conversion detectors.

Flat-panel detectors

It consists of a photoconductor, amorphous selenium (a-Se), which holds a charge on its surface that can then be read out by a TFT

Direct Conversion

In this, x-ray photons are absorbed by the coating material and immediately converted into an electrical signal.

thin-film transistor (TFT)

It is a photosensitive array made up of small (about 100 to 200 μm) pixels.

field-effect transistor (FET) or silicon TFT

isolates each pixel element and reacts like a switch to send the electrical charges to the image processor .

Indirect Conversion detectors

It is a two-step process: x-ray photons are converted to light, and then the light photons are converted to an electrical signal.

CsI scintillator

A newer type of amorphous silicon detector uses a…?

charge-coupled devices (CCDs)

The oldest indirect-conversion DR system is based on…?

complementary metal oxide silicon (CMOS)

This systems use specialized pixel sensors that, when struck with x-ray photons, convert the x-rays into light photons and store them in capacitors.

detective quantity efficiency (DQE)

How efficiently a system converts the x-ray input signal into a useful output image is known as?

DQE

Its a measurement of the percentage of x-rays that is absorbed when they hit the detector.

Detector size

It's critical. It must be large enough to cover the entire area to be imaged and small enough to be practical.

direct and indirect

There are two types of cassetteless digital imaging systems:

Direct sensors

are TFT arrays of amorphous silicon coated with a-Se.

Direct sensors

absorb x-ray photons and immediately convert them to an electrical signal.

Indirect conversion detectors

It use a scintillator that converts x-rays into visible light, which is then converted into an electric charge.

charge-coupled devices (CCDs)

It act as miniature cameras that convert light produced by x-ray interaction with photostimulable phosphors into an electrical charge.