Abstract: The present disclosure describes methods for calibrating a spectral X-ray system to perform material decomposition with a single scan of an energy discriminating detector or with a single scan at each used X-ray spectrum. The methods may include material pathlengths exceeding the size of the volume reconstructable by the system. Example embodiments include physical and matching calibration phantoms. The physical calibration phantom is used to measure the attenuation of X-rays passing therethrough with all combinations of pathlengths through the calibration's basis materials. The matching digital calibration phantom is registered with the physical calibration phantom and is used to calculate the pathlength though each material for each measured attenuation value. A created data structure includes the X-ray attenuation for each X-ray spectrum or detector energy bin for all combinations of basis material pathlengths.

Abstract: The present disclosure describes methods and apparatuses for reducing metal artifacts in cone beam computed tomography (CBCT) reconstructions. The methods use multiple imaging modalities to identify and locate metal present in a region of dental patients mouth and to generate a reconstructed 3-D volume image of the region with reduced metal artifacts using data obtained by the multiple modalities. According to example embodiments, the methods include creating a metal map using data from a first imaging modality and an initial 3-D reconstruction from data obtained from a second imaging modality including CBCT imaging. The metal map is registered to the initial 3-D reconstruction with a reconstructed metal map and projection metal maps being subsequently produced and applied to projections from the CBCT imaging to generate interpolated projections.

Abstract: A method for rendering metal obscured regions in a volume radiographic image reconstructs a first 3D image using a plurality of 2D projection images obtained over a scan angle range relative to the subject and identifies metal in the first 3D image or metal shadows in the plurality of 2D projection images. Then, metal obscured regions are determined in a reconstructed 3D image of the object, and an alternative reconstruction being a limited angle reconstruction is performed for the metal obscured regions and displayed to the user with an indication of the spatial relationship to a corresponding metal obscured region.

Abstract: A method for geometric calibration of a volume imaging apparatus disposes calibration phantom in a radiation path that includes a subject positioned between an x-ray source and a detector. The phantom has a number of radio-opaque markers formed of a marker material. In a repeated sequence, at each of a number of positional relationships of the x-ray source to the detector: 2D projection image data is acquired for the subject and the phantom, wherein the 2D projection image data distinguishes at least first and second x-ray energy distributions; source-to-detector geometry of the imaging apparatus is calculated, corresponding to the acquired 2D projection image data for the first and second x-ray energy distributions. The method reconstructs and displays a 3D volume image of the subject according to acquired anatomy image data from the subject and source-to-detector geometry within the 2D projection images.

Abstract: An intraoral tomosynthesis imaging apparatus having an intraoral detector coupled to a frame or radio-opaque marker attached to its radiation facing surface without any frame attached, wherein the frame defines a target aperture for an incident radiation beam. An enclosure seats against the target aperture and houses at least one x-ray source configured to emit a radiation beam from each of a plurality of focal points within the enclosure A collimator is disposed to form a collimated radiation beam and direct the collimated beam through the target aperture and to the detector. A geometric calibration phantom having a plurality of radio-opaque markers is disposed in the path of the collimated beam. This arrangement is modified to operate as a regular intraoral imaging device by accommodating a high-power central source at the same or different distances as other sources from the detector and displacing the phantom from the field of view.

Abstract: A method for characterizing bone structure for a patient, method executed at least in part on a computer, acquires one or more 2D x-ray projection images of a volume, wherein image content is acquired at two or more spectral frequencies. The acquired x-ray image content is processed to calculate one or more metrics that characterize bone structure within the imaged volume. The one or more calculated metrics are displayed.

Abstract: The present disclosure describes methods and apparatuses for reducing metal artifacts in cone beam computed tomography (CBCT) reconstructions. The methods use multiple imaging modalities to identify and locate metal present in a region of dental patients mouth and to generate a reconstructed 3-D volume image of the region with reduced metal artifacts using data obtained by the multiple modalities. According to example embodiments, the methods include creating a metal map using data from a first imaging modality and an initial 3-D reconstruction from data obtained from a second imaging modality including CBCT imaging. The metal map is registered to the initial 3-D reconstruction with a reconstructed metal map and projection metal maps being subsequently produced and applied to projections from the CBCT imaging to generate interpolated projections.

Abstract: The present disclosure describes a Cone Beam Computed Tomography (CBCT) imaging system and methods of operating the system to minimize the degradation of projection images by metal in a scanned object. The methods determine the location of metal in the scanned object by making an initial low dose scan and then, using information obtained from the low dose scan, perform a second scan that may be used to create a reconstruction with reduced artifacts. The methods also calculate X-ray source and detector scan trajectories which minimize reconstruction artifacts and optimize image quality, especially when a region-of-interest is near metal in the scanned object. Additionally, the methods of the present invention calculate X-ray source and detector scan trajectories that maximize the angular range of X-rays which pass through the region-of-interest that are not blocked by metal in the scanned object.

Abstract: The present disclosure describes methods for calibrating a spectral X-ray system to perform material decomposition with a single scan of an energy discriminating detector or with a single scan at each used X-ray spectrum. The methods may include material pathlengths exceeding the size of the volume reconstructable by the system. Example embodiments include physical and matching calibration phantoms. The physical calibration phantom is used to measure the attenuation of X-rays passing therethrough with all combinations of pathlengths through the calibration's basis materials. The matching digital calibration phantom is registered with the physical calibration phantom and is used to calculate the pathlength though each material for each measured attenuation value. A created data structure includes the X-ray attenuation for each X-ray spectrum or detector energy bin for all combinations of basis material pathlengths.

Abstract: The present disclosure describes methods for improving semi-automatic and/or fully automatic tooth segmentation in reconstructed images of X-ray scans using multi-energy X-ray spectra and/or a multi-energy X-ray scanner at more than one energy. Such improved segmentation of teeth in a reconstructed image of an X-ray scan is a critical first step in the utilization of the image for applications in orthodontics, endodontics, and implant planning In accordance with the methods, tooth segmentation may be performed semi-automatically or automatically for images which are reconstructed from a multi-energy X-ray scan. The results of the tooth segmentation may be represented as an image map which identifies voxels which are within a tooth or as a three-dimensional (3D) grid or any other representation of a three-dimensional (3D) spatial region.

Abstract: Methods for reconstruction of a volume radiographic image acquire 2-D projection images of a subject at a plurality of acquisition angles and generate an initial 3-D volume image formed of image voxels according to the acquired 2-D projection images. An initial 3-D reconstruction metal mask is formed from voxels that have attenuation to x-rays indicative of metal. At least one voxel is removed from the initial 3-D reconstruction metal mask to form a refined 3-D reconstruction metal mask according to a distribution of pixel values that contribute to the corresponding data value for the at least one voxel. One or more 2-D projection images are modified according to the distribution of pixel values. A refined 3-D volume image is generated according to the modified 2-D projection images. A rendering of the refined 3-D volume image displays that includes at least a portion of the refined 3-D reconstruction metal mask.

Abstract: A method for rendering metal obscured regions in a volume radiographic image reconstructs a first 3D image using a plurality of 2D projection images obtained over a scan angle range relative to the subject and identifies metal in the first 3D image or metal shadows in the plurality of 2D projection images. Then, metal obscured regions are determined in a reconstructed 3D image of the object, and an alternative reconstruction being a limited angle reconstruction is performed for the metal obscured regions and displayed to the user with an indication of the spatial relationship to a corresponding metal obscured region.

Abstract: A method for displaying a paranasal sinus region of a patient is executed at least in part on a computer, acquiring volume image data of the paranasal sinus region of the patient, identifying one or more airways within the paranasal sinus region from the volume image data, displaying the at least one or more airways, and highlighting one or more portions of the displayed airways that are constricted below a predetermined value.

Abstract: A method for reducing metal artifacts in a volume radiographic image reconstructs a first 3-D-image using measured projection images and forms a 3-D image metal mask that contains metal voxels. For each measured projection image, a projection metal mask is a projection of the 3-D image metal mask. A 3-D prior image contains voxels within the 3-D image metal mask. Voxel values of the first 3-D image outside the 3-D image metal mask are replaced with a value representative of air or soft tissue. Non-metal voxels of the 3-D prior image are modified according to a difference between a pixel value related to the nonmetal voxel and the corresponding pixel value in a calculated projection image. Composite projection images are formed by replacing measured projection image data for pixels within the projection metal mask with calculated projection image data. A metal artifact reduced 3-D image is reconstructed from composite projections.

Abstract: A method for generating a 3-dimensional reconstruction model of an object of interest that lies within a volume, the method executed at least in part by a computer, acquires a first set of projection images of the volume at a first exposure and a first field of view and a second set of projection images of the object of interest within the volume at a second exposure that is higher than the first exposure and a second field of view that is narrower than the first field of view. An object of interest is reconstructed from the second set of projection images according to information related to portions of the volume that lie outside the object of interest. The reconstructed object of interest is displayed.

Abstract: A method for generating a 3-dimensional reconstruction model of an object of interest that lies within a volume, the method executed at least in part by a computer, acquires a first set of projection images of the volume at a first exposure and a first field of view and a second set of projection images of the object of interest within the volume at a second exposure that is higher than the first exposure and a second field of view that is narrower than the first field of view. An object of interest is reconstructed from the second set of projection images according to information related to portions of the volume that lie outside the object of interest. The reconstructed object of interest is displayed.

Abstract: A method for reducing metal artifacts in a volume radiographic image reconstructs a first 3-D-image using measured projection images and forms a 3-D image metal mask that contains metal voxels. For each measured projection image, a projection metal mask is a projection of the 3-D image metal mask. A 3-D prior image contains voxels within the 3-D image metal mask. Voxel values of the first 3-D image outside the 3-D image metal mask are replaced with a value representative of air or soft tissue. Non-metal voxels of the 3-D prior image are modified according to a difference between a pixel value related to the nonmetal voxel and the corresponding pixel value in a calculated projection image. Composite projection images are formed by replacing measured projection image data for pixels within the projection metal mask with calculated projection image data. A metal artifact reduced 3-D image is reconstructed from composite projections.

Abstract: A method for forming a three-dimensional reconstructed image acquires two dimensional measured radiographic projection images over a set of projection angles, wherein the measured projection image data is obtained from an energy resolving detector that distinguishes first and second energy bands. A volume reconstruction has image voxel values representative of the scanned object by back projection of the measured projection data. Volume reconstruction values are iteratively modified to generate an iterative reconstruction by repeating, for angles in the set of projection angles and for each of a plurality of pixels of the detector: generating a forward projection that includes calculating an x-ray spectral distribution at each volume voxel, calculating an error value by comparing the generated forward projection value with the corresponding measured projection image value, and adjusting one or more voxel values using the calculated error value and the x-ray spectral distribution.

Abstract: A method for displaying a paranasal sinus region of a patient is executed at least in part on a computer, acquiring volume image data of the paranasal sinus region of the patient, identifying one or more airways within the paranasal sinus region from the volume image data, displaying the at least one or more airways, and highlighting one or more portions of the displayed airways that are constricted below a predetermined value.

Abstract: A method for forming a three-dimensional reconstructed image acquires two dimensional measured radiographic projection images over a set of projection angles, wherein the measured projection image data is obtained from an energy resolving detector that distinguishes first and second energy bands. A volume reconstruction has image voxel values representative of the scanned object by back projection of the measured projection data. Volume reconstruction values are iteratively modified to generate an iterative reconstruction by repeating, for angles in the set of projection angles and for each of a plurality of pixels of the detector: generating a forward projection that includes calculating an x-ray spectral distribution at each volume voxel, calculating an error value by comparing the generated forward projection value with the corresponding measured projection image value, and adjusting one or more voxel values using the calculated error value and the x-ray spectral distribution.