Planmeca looks to the third dimension with ProMax

Planmeca has shown its latest work-in-progress to the world in the form of a Cone Beam Computed Tomography (CBCT) system for three-dimensional (3D) dental imaging in the dental practice.

Cone Beam Computed Tomography is an imaging technique that obtains clinically significant data relating to bone structure and morphology for thorough diagnosis and treatment planning. Planmeca's new CBCT concept provides accurate 3D image information, enhancing the level of confidence in diagnosing endodontic and periodontal diseases and TMJ problems. It also generates a great degree of image information for implant planning and oral surgery.

The system, when it becomes available, will enable users to perform workflow-friendly 3D imaging in the dental practice. The dental anatomy acquired in a single scan can be viewed in all three dimensions and the exact location of the region of interest can be selected at the time of diagnosis. The advanced detector technology makes the concept beneficial to the patient as the radiation dose is drastically lower compared to medical CT scanning.

The new concept utilises the latest developments in 3D image reconstruction algorithms, producing accurate and distortion-free images. A fast image reconstruction cycle is achieved through an intelligent use of computing hardware and through a proprietary computing model.

The 3D studies can be transmitted for further diagnosis or archiving using standard DICOM protocols.

The Planmeca ProMax OPG will be the hardware platform for the 3D technology and will be available either as a factory delivered unit or as a field upgrade to system sold after April 2005.

The Planmeca ProMax platform, with its software controlled SCARA movements and digitally controlled X-ray generator, have been programmed to perform 3D studies of dental anatomy. The 3D sensor is a semiconductor-based flat-panel sensor which is insensitive to electric or magnetic field disturbances.

During a 20-second scan, the high sensitivity flat panel sensor provides low-noise distortion-free images at pre defined angles provided by the digitally controlled movement of the ProMax. Low noise and the absence of distortions together with accurate control of the scan movement are essential requirements for high quality 3D reconstructions.

The pixel data, which consists of over 200 images, are transformed to 3D voxel data via a proprietary reconstruction algorithm. Computing uses all the pixel data to form an accurate 3D volume model of the anatomy. The isotropic voxel is a 0.15 x 0.15 x 0.15 mm cube. It enables high resolution viewing and accurate measurements in the whole 3D volume data.

After acquisition of the 3D volume dataset, patient images can be processed in any plan to reproduce highly accurate 2D and 3D views of the selected patient area without the imposition of overlaying and underlying tissues. A unique level of clarity is achieved together with precise geometry allowing accurate measurements in any plane for implants and surgery planning.

During the image acquisition, the Planmeca ProMax X-ray generator works in high mA pulsed mode. This technology enables short, high intensity pulses to capture the images, like in a stroboscope. The high capacity readout of the flat panel sensor contributes to the fast 20-second scan time, eliminating distortions caused by patient movement. Thanks to the fast pulsing X-ray generator, the patient dose is minimal, and significantly lower than the average patient dose of a CT examination of the head. By a rough estimate, the patient dose of a 3D examination is equal to ten panoramic images or 20 film-based periapicals.

There is one fundamental difference between tomographic and tomosynthetic technologies on the one hand, and on the other CBCT technology. It regards the way in which these technologies form image layers. Tomographic and tomosynthetic technologies form image layers by blurring out unwanted details in the desired projection, while CBCT technology produces an accurate calculation of each voxel in the selected volume. Even if details are blurred out with tomographic and tomosynthetic technologies, these details still cast shadows to the image and the projection is mostly fixed. With CBCT, the image is generated just as it is for a medical CT from voxels (three dimensional pixels) and is not corrupted by shadow interference.

Planmeca is currently finalising the development of the ProMax 3D imaging

system. In-house testing is under way and clinical testing will start shortly, as will the homologation process for CE, FDA and TGA listing.

The same Planmeca ProMax unit can be used for taking digital panoramic, digital cephalometric and 3D images. The 3D imaging system will be a field-upgradeable option to existing Planmeca ProMax units built after April 2005.