Buyers Guide: Cone Beam 3D Imaging

Dentalcompare
Clinical Director
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How does Cone Beam Work?

Cone Beam CT is arguably one of the most incredible advances the entire dental profession has seen in the last few decades. While we certainly have seen many other innovations such as digital impressions, handpiece technology or laser dentistry, each of those is related to treatment. And we can only treat what we have diagnosed, and we can only diagnose what we can actually see.

Put simply, Cone Beam CT allows you to see more. It provides three dimensional views of teeth, the TMJ or airway that have never been available before. 

The technology works in a similar fashion as other radiographic imaging, such as digital panoramic systems. There is an x-ray source on one side and a detector on the other. In the case of cone beam, the x-rays are released in the shape of a cone. As the unit spins around the patient’s head, the computer picks up a series of cephalometric x-rays with variable densities and uses a complex algorithm to rebuild them into a 3D pattern based on similar points of density.

The result is a 3D image of the patient.

While 2D images have distortion similar to the way a shadow is distorted depending on the position of the sun, Cone Beam images are free of distortion, allowing exact sizes and distances to be measured down to the 10ths of a millimeter. Another advantage over 2D imaging is the ability to view an internal slice of a Cone Beam image to view a specific plane of the anatomy without having to deal with structures in front or behind it.

Radiation exposure from any x-ray imaging is a concern, but Dental Cone Beam systems use far less radiation than a medical CT scan. Those systems capture individual x-ray slices and then reassemble them to create the 3D image. It’s similar to building a loaf of bread by grabbing one slice at a time, whereas dental Cone Beam systems grab the entire loaf at once.

Image

Why Do I Need Cone Beam

  • Implant Dentistry – Cone Beam is a natural fit for implant planning. It lets you see the undistorted position of crucial structures such as the inferior alveolar nerve or the maxillary sinus, and 1:1 measuring tools allow precisely gauged distances and virtual treatment planning with digital versions of your implant system of choice.
  • Endodontics – Many times the periodical radiolucency is being blocked by other structures, or by a root itself. You can see precise endodontic pathology when using cone beam, and the accuracy even allows visualization of the MB2 canals in upper molars prior to access.
  • Periodontics – Cone Beam CT allows you to see bone levels in three dimensions around a tooth. This makes it easier to target treatment or to know if an extraction and grafting is a better choice.
  • Orthodontics – Cone Beam allow you to create cephalometric reconstructions from the images. You also can see the precise position of all teeth and the exact orientation of an impacted canine tooth.
  • Oral Surgery – Along with implant placement, Cone Beam takes the guesswork out of surgery. In the case of wisdom teeth, you can see the exact location in relation to adjacent teeth, as well as to an inferior alveolar nerve.
  • Airway – Snoring and sleep apnea have now been indicated in everything from hypertension to heart disease. Cone beam allows you to do complex airway studies to determine the best treatment.

What I Need to Know

Voxel vs. Pixel: In digital pictures, resolution of the image is measured in pixels which are small squares of information. The greater the number of pixels, the more detailed the image. For 3D images you have a voxel, which is a cube of information stacked with other cubes to make up the image. Voxel size can be as low as 0.085 mm. 

Imaging Software: The software used to view the image should be intuitive and easy to use for capturing and evaluating the images. Some software applications can reduce the scatter caused when x-rays encounter metal in a patient’s mouth.

Detector Type:There are two basic types: Flat Panel (direct acquisition) and Image Intensifier (indirect acquisition). The flat panel is often more efficient and can provide an image with reduced noise. Radiation exposure is usually higher for flat panel machines, however some of the newest flat panel systems have addressed this issue with doses comparable to, or even lower than indirect systems.

Portal to Surgical Guides: Any cone beam machine will allow you to have a surgical guide made for placing dental implants, but it’s important to know if this functionality built into the software, or if a 3rd party application is required. Know the costs associated with each option, and consider the fees for image cleanup or fabrication of the guide itself.

Size of the Volume: Each Cone Beam machine will collect a certain volume of data corresponding to an area of the anatomy. Some machines can capture just one quadrant while others can image the entire mandible, maxilla and as high as the inferior portion of the orbital cavity. 

Exposure Time: This is how long it takes to acquire a full image of the patient, often in the 10-20 second range. Shorter exposure times mean shorter time for patients to sit still and increased likelihood of obtaining an undistorted image.

Reconstruction Time: This is how long it takes for the computer to build the 3D image. Times can range from as low as 20 seconds up to 5 or 6 minutes. 

Patient Position: Cone Beam systems have been designed with three patient position options: standing, sitting, or laying down. Standing machines take up less space in the practice, but the other orientations make it easier for the patient to stay still during image acquisition. 

Footprint and Size of the Machine: As stated above, the machine has to be able to fit in your office. Consider where it will go or what older equipment it might replace. Get creative!

Questions to Ask

  1. What type of office do I have and what procedures do I perform?
  2. Am I interested in placing dental implants?
  3. What is the field of acquisition of the machine?  Do I need to capture the TMJ and the entire maxilla, or am I looking at 2-3 teeth?
  4. Does my purchase include training in use of the machine, as well as utilization of the software and what anatomic structures are being viewed?
  5. How do I get software upgrades? Is there an ongoing fee, individual upgrade fees, or is it free with ownership of the machine?
  6. What is the warranty on the machine?
  7. What is included in the service agreement?
  8. How fast can I get a repair person to my office if the machine goes down?
  9. What basic requirements for my existing computer network will change? Consider that the images are very large, and most recommend computers with higher end video cards, as well as networks with Gigabit switching and Cat 5e or Cat 6 cabling.

Definitions

ALARA – As Low As Reasonably Achieve is the guiding principle for use of most x-ray imaging technologies. It encourages clinicians to use the lowest radiation settings possible to capture a necessary diagnostic image.

Computed tomography – An imaging technique that uses x-rays and computer software to produce composite images built from individual slices.

Gigabit Ethernet – A computer connection that supports 1 Gigabit per second data transfer speeds. 

Voxel – A single sample, or data point, on a regularly spaced, three dimensional grid. The building blocks of a 3D digital image.

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