CEPHALOGRAM ( CEPH )
Cephalometric analysis is done to evaluate dental and skeletal relationship.
It helps in planning for the alignment of the teeth
It helps to find out the skeletal and dental abnormality.
Cone Beam Computed Tomography
To overcome some of the disadvantages of conventional medical CT scanners, a new type of CT specific for dental applications has recently been developed. This type of advanced tomography (CBCT). Because conventional CT is associated with such a high dose of radiation, this imaging medical technique has always been under significant criticism when used for implant treatment planning. However, with the advent of cone beam technology, the limitations of medical computerized tomography has been overcome. Recently, with the U.S. Food and Drug Administration approval of cone beam technology, there are choices to provide more accurate diagnostic images along with the fraction of radiation exposure, and adherence to the ALARA principle has been accomplished. Scanner are made for “in-office” installation and use, which allows a doctor and patient the convenience of onsite scanning capabilities.
Medical versus cone beam technology Radiation Dosages.
The average absorbed radiation dose from a CBCT scanner (NewTom 3G) is approximately 12.0mSv (micro sieverts). This dose is equivalent to five D-speed dental x-rays or 25% of the radiation from a typical panoramic radiograph. Additionally, medical scanners acquire images that use radiation doses of 40 to 60 times that of CBCT doses.
Image acquisition of medical versus Cone Beam Scanners.
Medical CT scans produce images of transaxial planes by use of solid-state detectors and an x-ray source that rotates around the patient. When compared with the conventional dental x-ray that is a two-dimensional images of many planes superimposed on each other, the CT image has greater contrast with a reduction in spatial resolution. These CT images are reconstructed mathematically, from these incremental images that produce average reconstructed images. However, between each parallel slice exists a small “gap” that contributes to a build-in error within medical scanners. These gaps are adjusted within the software’s algorithms that can result in errors of 1.0 to 1.5 mm.
Using CBCT avoids the errors in medical scanners by accumulating data from one 360-degree rotation around the patient’s head. The algorithms on CBCT scanners very predictable because they are void of any “gaps”, thus eliminating distortion and magnification. Margins of error for CBCT are less than 0.1 mm. Numerous studies have shown cone beam technology to be more accurate than conventional medical CT.
The advantages of CT images are numerous, with the magnification being almost 0% with no superimposition or overlapping of images and minimal distortion. The density of bone may also be assessed with all images being displayed as Hounsfield units. When comparing CT with other types of radiographic modalities, CT has been shown to be superior in identification of vital structures and calculation of distance measurements.
Comparison of medical CT Scanner and Cone Beam
|Scanning Time||Approximately 10 min||Approximately 30 sec.|
|Scan||Multiple slices||One rotation|
|Exposed field||One arch at a time||Both arches simultaneously|
|Positioning||Very technique sensitive||Not as critical|
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