BACKGROUND

Field

The present application relates generally to obtaining tomographic images in a dental environment, and, more particularly, to methods, systems, apparatuses, and computer programs for processing tomographic images.

Description of Related Art

X-ray radiography can be performed by positioning an x-ray source on one side of an object (e.g., a patient or a portion thereof) and causing the x-ray source to emit x-rays through the object and toward an x-ray detector (e.g., radiographic film, an electronic digital detector, or a photostimulable phosphor plate) located on the other side of the object. As the x-rays pass through the object from the x-ray source, their energies are absorbed to varying degrees depending on the composition of the object, and x-rays arriving at the x-ray detector form a two-dimensional (2D) x-ray image (also known as a radiograph) based on the cumulative absorption through the object. This process is explained further in reference toFIG. 60A-FIG. 60C.

FIG. 60Ashows a patient and an x-ray device6000positioned for obtaining an occlusal image of the mandible. A sensor or x-ray film (not shown) is disposed inside the patient's mouth. An exposure is recorded and an x-ray image is subsequently developed, as shown inFIG. 60B. In traditional x-ray imaging, the sensor (or film) records the intensity of the x-rays incident thereon, which are reduced (or attenuated) by the matter which lies in their respective paths. The recorded intensity represents that total attenuation of the x-ray through the image volume, as illustrated inFIG. 60C.

InFIG. 60Ctwo x-rays (ray A and ray B) are incident on two adjacent sensor elements6008and6010of an x-ray detector. Ray A travels through two blocks of identical material, block6002and block6004, each with an attenuation factor of 50%. Ray B travels through block6006which also has an attenuation factor of 50%. The intensity of Ray A recorded by sensor element6008is 25% of the original intensity. The intensity of Ray B recorded by sensor element6010is 50% of the original intensity. In a traditional x-ray image the recorded intensities are represented by light/dark regions. The lighter regions correspond to areas of greater x-ray attenuation and the darker regions correspond to areas of less, if any, x-ray attenuation. Thus, a two-dimensional projection image produced by sensor elements6008and6010will have a lighter region corresponding to sensor element6008and a darker region corresponding to sensor element6010. However, from such a two-dimensional projection image it cannot be determined that there were two blocks of material (6002and6004) at different positions in the path of Ray A, as opposed to a single block of material which caused the same amount of x-ray attenuation. In other words, the traditional x-ray image contains no depth information. As such, overlapping objects may easily obscure one another and reduce the diagnostic usefulness of the projection image.

Computed tomography (CT) and cone beam computed tomography (CBCT) have been used to acquire three-dimensional data about a patient, which includes depth information. The three-dimensional data can be presented on a display screen for clinician review as a 3D rendering or as a stack of parallel 2D tomographic image slices. Each slice represents a cross-section of the patient's anatomy at a specified depth. While CT and CBCT machines may produce a stack of parallel 2D tomographic image slices, these machines carry a high cost of ownership, may be too large for use in chair-side imaging, and expose patients to a relatively high dose of x-rays.

Tomosynthesis is an emerging imaging modality that provides three-dimensional information about a patient in the form of tomographic image slices reconstructed from images taken of the patient with an x-ray source from multiple perspectives within a scan angle smaller than that of CT or CBCT (e.g., ±20°, compared with at least 180° in CBCT). Compared to CT or CBCT, tomosynthesis exposes patients to a lower x-ray dosage, acquires images faster, and may be less expensive.

Typically, diagnosis using tomosynthesis is performed by assembling a tomosynthesis stack of two-dimensional image slices that represent cross-sectional views through the patient's anatomy. A tomosynthesis stack may contain tens of tomosynthesis image slices. Clinicians locate features of interest within the patient's anatomy by evaluating image slices one at a time, either by manually flipping through sequential slices or by viewing the image slices as a cine loop, which are time-consuming processes. It may also be difficult to visually grasp aspects of anatomy in a proper or useful context from the two-dimensional images. Also, whether the tomographic images slices are acquired by CT, CBCT, or tomosynthesis, their usefulness for diagnosis and treatment is generally tied to their fidelity and quality.

Quality may be affected by image artifacts. Tomosynthesis datasets typically have less information than full CBCT imaging datasets due to the smaller scan angle, which may introduce distortions into the image slices in the form of artifacts. The extent of the distortions depends on the type of object imaged. For example, intraoral tomosynthesis imaging can exhibit significant artifacts because structures within the oral cavity are generally dense and radiopaque. Still further, spatial instability in the geometry of the tomosynthesis system and/or the object can result in misaligned projection images which can degrade the quality and spatial resolution of the reconstructed tomosynthesis image slices. Spatial instability may arise from intentional or unintentional motion of the patient, the x-ray source, the x-ray detector, or a combination thereof. It may therefore be desirable to diminish one or more of these limitations.

SUMMARY

One or more the above limitations may be diminished by methods, systems, apparatuses, and computer programs products for processing tomographic images as described herein.

In one embodiment, a method of identifying a tomographic image of a plurality of tomographic images is provided. Information specifying a region of interest in at least one of a plurality of projection images or in at least one of a plurality of tomographic images reconstructed from the plurality of projection images is received. A tomographic image of the plurality of tomographic images is identified. The identified tomographic image is in greater focus in an area corresponding to the region of interest than others of the plurality of tomographic images.

In another embodiment, an apparatus for identifying a tomographic image from a plurality of tomographic images. The apparatus includes a processor and a memory storing at least one control program. The processor and memory are operable to: receive information specifying a region of interest in at least one of a plurality of projection images or in at least one of a plurality of tomographic images reconstructed from a plurality of projection images, and identify a tomographic image of the plurality of tomographic images. The tomographic image is in greater focus in an area corresponding to the region of interest than others of the plurality of tomographic images.

In a further embodiment, a non-transitory computer-readable storage medium storing a program which, when executed by a computer system, causes the computer system to perform a method. The method includes receiving information specifying a region of interest in at least one of a plurality of projection images or in at least one of a plurality of tomographic images reconstructed from the plurality of projection images, and identifying a tomographic image of the plurality of tomographic images. The identified tomographic image is in greater focus in an area corresponding to the region of interest than others of the plurality of tomographic images.

In still another embodiment, a method for generating clinical information is provided. Information indicating at least one clinical aspect of an object is received. Clinical information of interest relating to the at least one clinical aspect is generated from a plurality of projection images. At least one of the steps is performed by a processor in conjunction with a memory.

In still a further embodiment, an apparatus for generating clinical information. The apparatus includes a processor and a memory storing at least one control program. The processor and the memory are operable to: receive information indicating at least one clinical aspect of an object, and generate, from a plurality of projection images, clinical information of interest relating to the at least one clinical aspect.

In yet another embodiment, a non-transitory computer readable storage medium storing a program which, when executed by a computer system, causes the computer system to perform a method. The method includes receiving information indicating at least one clinical aspect of an object, and generating, from a plurality of projection images, clinical information of interest relating to the at least one clinical aspect.

