The present invention relates to dental imaging technology. More specifically, the present invention relates to reconstructing a three-dimensional image of a patient's teeth using both x-ray and surface scanning technology.
X-ray technology can be used to generate a three-dimensional, digital representation of a subject using computed tomography (CT). However, metal and other objects can reflect x-rays that would otherwise penetrate through human tissue and be detected by the x-ray detector. This reflection can cause unwanted artifacts to appear in the captured data set. This effect is particularly prevalent in dental imaging where foreign substances such as metal fillings or braces are often installed in the patient's mouth.
There are some prior systems in which artifacts are removed from x-ray data by, simply stated, “combining” x-ray and non-x-ray data. However, as best known by the inventors, in addition to removing or reducing artifacts, such systems also remove significant amounts of desired image data.
U.S. Publication No. 2010/0124367 has suggested that artifacts can be removed from x-ray data by the “fusion of the x-ray data set with an optical image of the jaw, which is completely free of metal artifacts . . . .” However, details regarding how the artifacts would be removed are not provided and the “fusion” disclosed in the '367 publication uses a pre-positioning technique that requires identifying registration points on a screen or other manual means prior to combining the data. While this pre-positioning makes the task of combining the two data sets substantially easier than a completely automatic method, the method requires manual intervention. That is, the x-ray technician, dentist, or other dental professional must manually manipulate the images on a screen.
U.S. Pat. No. 6,671,529 describes a method of creating a composite skull model by combining three-dimensional CT data and laser surface scans of a patient's teeth. In the '529 patent, the teeth are completely removed from the CT model and replaced with only the surface scan data of the patient's teeth.
U.S. Pat. No. 7,574,025 describes a method of removing artifacts from a three-dimensional model (such as CT or MRI) by a negative impression template of the patient's teeth. In the '025 patent, a negative impression template is cast of the patient's teeth. A first model is generated while the negative impression template is placed in the patient's mouth. A second model is generated of only the negative impression template using the same imaging technology as the first. Voxels from the first digital image are substituted for corresponding voxels from the second digital image to create a model of the patient's teeth without artifacts.