Digital Radiology

Advances in computer and X-ray technology now permit the use of systems that employ sensors in place of X-ray ?lms (with emulsion). The image is either directly or indirectly converted into a digital representation that is displayed on a computer screen. 

DIGITAL IMAGE RECEPTORS

- charged coupled device (CCD) used
- Pure silicon divided into pixels.
- Electromagnetic energy from visible light or X-rays interacts with pixels to create an electric charge that can be stored.
- Stored charges are transmitted electronically and create an analog output signal and displayed via digital converter (analog to digital converter). 

ADVANTAGES OF DIGITAL TECHNIQUE

Immediate display of images.

Enhancement of image (e.g., contrast, gray scale, brightness).

Radiation dose reduction up to 60%.

Major disadvantage: High initial cost of sensors. Decreased image resolution and contrast as compared to D speed ?lms.

DIRECT IMAGING

- CCD or complementary metal oxide semiconductor (CMOS) detector used that is sensitive to electromagnetic radiation.

- Performance is comparable to ?lm radiography for detection of periodontal lesions and proximal caries in noncavitated teeth.

INDIRECT IMAGING

- Radiographic ?lm is used as the image receiver (detector). 

- Image is digitized from signals created by a video device or scanner that views the radiograph.

Sensors

STORAGE PHOSPHOR IMAGING SYSTEMS

Phosphor screens are exposed to ionizing radiation which excites BaFBR:EU+2 crystals in the screen storing the image.

A computer-assisted laser then promotes the release of energy from the crystals in the form of blue light.

The blue light is scanned and the image is reconstructed digitally.

ELECTRONIC SENSOR SYSTEMS

X-rays are converted into light which is then read by an electronic sensor such as a CCD or CMOS.

Other systems convert the electromagnetic radiation directly into electrical impulses.

Digital image is created out of the electrical impulses.