Intraoral Camera

Digital Radiography:

There are three methods of producing digital images: CCD/CID/CMOS sensors, phosphorus plates and scanning of conventional film. All three systems are available in periapical, panoramic and cephalometric sizes. This digital radiography equipment uses conventional generation devices to produce x-ray energy. Direct digital radiography and phosphorus plates have many advantages over silver halide film, such as speed, reduced radiation, environmental waste reduction, elimination of darkroom costs, lossless e-mail image transfer and enhanced practice image.

The value of instant digital imaging in the modern dental office, especially for endodontic and implant procedures is well known. "Several phosphorus and CCD/CMOS digital systems have good-to-very-good image quality, plus ease of use, and image enhancement capabilities that make them competitive with conventional film in overall usefulness." However, according to the CRA Associates, the image quality of digital radiographs still does not measure up to the sharpness and detail of silver halide film. Conventional film provides a finer grade of detail through continuous shades of black-and-white images, rather than discrete shades of gray used by digital systems. Advances are being made (digital subtraction radiography , improved resolution), though, and digital image quality may equal or surpass that of film in the future. As Dunn and Kantor stated in their review of the subject, "digital imaging has many potential benefits yet to be fully explored or demonstrated."

Resolution:

One of the most critical - and most misunderstood - issues concerning digital representation of image data is resolution. While computer screen selection, ambient lighting and image compression all affect resolution, the most compelling issue is the image quality of dental structures as viewed by the clinician. According to a study by Clinical Research Associates on dental imaging quality, some currently available systems were ranked using a scale of 1-10. Film ranked highest at 8.7. The second highest ranking was a film scanner that achieved an image quality score of 7.0, but is dependent on the quality of the original film-based image. The digital radiography systems ranked slightly lower for image quality in dental applications with scores ranging between 6.5 and 3.0.

The quality of many film-based images, on the other hand, is compromised by operational problems such as chemical and film freshness, developing inconsistencies, light leaks, and shipment handling. Detection of gross and moderate caries can be performed with both conventional film and digital imaging systems with a great degree of surety. For incipient caries detection, film sharpness and detail are still helpful adjuncts to digital systems. Unfortunately, the presence of caries are always more extensive than depicted by either digital or film systems. Incipient caries and some periapical lesions continue to present a challenge for both film and digitally based systems.

In the detection of periapical bone lesions created in cortical and trabecular bone, no difference was detected by Paurazas, et al. between E-speed film, CCD and CMOS sensors. Furthermore, cortical bone lesions were detected with significantly higher accuracy once the junction of the cortical plate was involved or perforated.

Radiation:

Digital imaging generally requires less radiation than film-based systems. According to the CRA Newsletter, CCD/CID/CMOS sensors can reduce exposure by up to 82 percent. Phosphorous plates reduce radiation by up to 22 percent compared with conventional film . Foroughi et al. noted reduced radiation averaging 55% when compared to Kodak D speed film and an average of 45% reduction when compared to E speed film. Film scanning provides no dose savings because a conventional film image must first be produced.

Time-to-image and time-to-retake: Conventional film and phosphorous plates takes at least a minute to process after the film is transported to the developing site and unwrapped, while CCD/CID/CMOS sensors are virtually instant, with paint times usually completed in less than four seconds. If the image is unsatisfactory or a second view is required, a second image can be generated using the CCD/CID/CMOS sensor by simply repositioning the x-ray tube head and/or sensor and exposing another image. Phosphor plates and films require considerably more time to produce the first image; time-to-retake is thereby increased, with less assurance that the second image will be at the desired angle. This improved workflow pattern using CCD/CID/CMOS sensors will enhance staff utilization and reduce patient waiting time for retakes. Dedicated film scanners generally take ten seconds to process a developed film.

Optimization:

All digital radiographic systems allow for image optimization. Most feature the ability to change contrast/brightness to view images that are under or over exposed, create an inverse image, equalize density, magnify and allow for image rotation and mirror imaging. Image annotation is another advantage of digital radiography. Some programs allow creation of markers or notes that will place descriptive annotation with numbered pointers, to call attention to specific details in the image. Algorithms that can sharpen and enhance caries are also present in a number of systems, holding promise for even more future improvements. Another enhancement, pseudo coloring ascribes false colors based on brightness of pixels and can help with patient visualization of images.

Measurement: Three types of measurement available with digital images: linear measurement, which allows the practitioner to measure the distance between two points in millimeters; angle measurement, which measures the angle between to lines; and area measurement, which measures the area of the image or a segment of the image. Since magnification and distortion error play a significant role in all radiographic measurement accuracy, both film and digital systems subject to error. A recent study by Eikenberg and Vandre demonstrated that „measurement error was significantly less for the digital images than the film-based images when comparing images of human skulls taken with a custom jig. However, the authors point out that in clinical situations, these measurement differences may not be clinically significant. Measurements are based on magnification and distortion error, so there is no statistical significance between conventional film and direct digital radiography. Sophisticated calibration algorithms are under development, so that accurate measurement of parallel images should be more feasible in the future.

Security:

While film based images can easily be produced in duplicate, each subsequent rendition of the image will be reduced in quality. Digital images, on the other hand, can be reproduced in unlimited quantity because the images are stored and produced without loss of any detail. Furthermore, digital images can be stored on and off site, on many types of media, thereby helping to mitigate theft, fire or other damage to records.

Paradoxically, the ease of reproduction and storage of digital images allows for the alteration of radiographs without a trace. The ease of producing an altered image is controversial, but improved safeguards are under development. Archiving radiographs in the form of write-once, read-many formats, such as the now ubiquitous multi-session CD-ROM recorder are among the current solutions to this issue. These CD-ROMs can be stored off site by a third party archivist. When sent through the Internet, this data is also vulnerable. The two technologies available today to encrypt this data, either SSL (Secure Socket Layer) or digital certificates, can provide at least 128 bit encryption and virtually eliminates the chance of alteration or fraud. SSL connections to Internet servers can be recognized by the prefix "https://" in the address line.

Markers:

Occasionally, radiographs and VL images warrant a tag so that you can return to them later to assemble teaching or patient education materials. Most software today allows markers to be placed so that a computer search can call up the images efficiently. In addition, readily available software enables you to create notes and diagrammatic annotation of important features of an image.

Computer Interface:

While each of the intraoral direct or wired digital radiography systems requires connection to the computer, only Schick Technologies&Mac226; system connects directly to the USB port of the CCW, thereby eliminating the input board and simplifying installation and maintenance. Laptop configurations add flexibility if the practitioner wants to move the equipment between different operatories and office locations, or use it for off-site procedures at hospitals and nursing homes. They also benefit from the elimination of special cards for sensor connection.