Digital Imaging and Acquisition

Digital Imaging

• Digital imaging is a method of capturing an image using a sensor, breaking it into electronic pieces, and presenting and storing the image using a computer and related imaging software.
• Digital image is composed of pixels, which are discrete units of information.
• Analog-to-digital converter converts data elements acquired by the sensor from analog to digital form.
• Bit-depth image determines the number of possible gray-scale combinations for each pixel. An 8-bit depth image has 256 shades of gray (2⁸).
• Digital subtraction is a method of reversing the gray scale as an image is viewed. Radiolucent images (normally black) appear white, and radiopaque images (normally white) appear black.
• Line pairs/millimeter (lp/mm) is a measurement used to evaluate the computer's ability to capture the resolution (or detail) of an image.

Digital Image Acquisition

• Direct digital imaging uses an intraoral sensor exposed to x-radiation to capture a dental image that can be viewed on a computer monitor.
• Indirect digital imaging uses a sensor scanned after exposure to x-radiation and then converted into a digital form that can be viewed on a computer monitor.
• Storage phosphor imaging records the image on a phosphor-coated plate, which is then placed into an electronic processor and scanned by a laser to produce an image on a computer monitor.

Key Components

• Sensor: A receptor used to capture intraoral or extraoral images in digital imaging.
• Charge-coupled device (CCD): A solid-state silicon chip detector that converts light or x-ray photons into an electrical charge or signal. This is found in the sensor.

Other Terms

• Nalog image: A radiographic image produced by conventional film.
• Digitize: To convert an image into a digital form that can be processed by a computer.