Oral Health Group

Ambient light can damage PSP image quality – Revenge of the sensors


February 3, 2011
by ken

Digital radiography is without question the standard of care in dentistry. 
 

There are two basic means to acquire a digital image:

  • CCD sensor removed from Canon A75 digital camera.

    Image via Wikipedia

    Direct: This is the fastest method to acquire an image and requires a specially coated electronic receptor, called a sensor, which records the image. The sensor is placed in the oral cavity in a similar manner as you would place a film packet. When exposed to x-radiation, the sensor converts the x-rays to an electronic form that is read by the computer almost immediately. Intraoral sensors are comparable in size to an intraoral film packet and may be wired or wireless. Wired sensors are connected to the computer via a fiberoptic cable and wireless sensors communicate with the computer via a radio frequency. (Currently only Schick Technologies sells a wireless sensor.)

  • Semi-indirect: This method requires a special sensor called a photostimuable phosphor plate (PSP) and a special scanner. The sensor is coated on one side with reusable phosphorus that stores the x-radiation until a scanning device converts it into a digital image. The PSP plate looks and handles like dental film, and the image is acquired when exposed to x-rays. Step two involves placing the plate in a special scanner, specific to the imaging software, to convert it to a digital image. This method is not as fast as the direct method, but quicker than the indirect method. The image stored on the plate is erased by exposing it to bright light. Once the plate is cleared, it can be used again. Some systems offer a scanner that also clears the plate, while other systems require the plate to be placed separately in bright light.
From Dr. Bicuspid


February 3, 2011 — The quality of phosphor-plate (PSP) radiographs may decrease if the plates are exposed to ambient light between the time the image is taken and when it is scanned, according to research to be presented next month at the International Association for Dental Research (IADR) meeting in San Diego.

Researchers from University Hospital Dresden examined the influence of time and the intensity of ambient light on
the quality and diagnostic information of PSP-based radiographs. Using a root canal instrument and VixWin software (Gendex Dental Systems), they acquired 250 digital x-ray images of an extracted tooth on five identical PSPs and exposed them to artificial light for different times (0-960 sec) and at different intensities (from less than 50 lux [lx] to more than 300 lx).

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