The patent's inventors are Muller, Serge (Guyancourt, FR); Puong, Sylvie (
This patent was filed on
From the background information supplied by the inventors, news correspondents obtained the following quote: "The field of the invention relates to a medical imaging method of tomosynthesis. In particular, it relates to a method for processing images obtained by tomosynthesis to improve the quality of the images necessary for a radiologist to develop a diagnosis.
"Tomosynthesis is a medical imaging modality whereof the essential principles are listed hereinbelow and illustrated in FIG. 1.
"FIG. 1 schematically illustrates the acquisition of 2D images of the organ and reconstruction of a 3D image of this organ by tomosynthesis.
"X-rays, R, originating from a source S are emitted according to different angulations (1, . . . , i, . . . , n) to the organ O. After passing through the organ, they are detected by the detector Det forming a set of projection images (Al, . . . , Ai, . . . , An). It should be noted that there are as many 2D images acquired as angulations considered.
"In single-energy tomosynthesis the basis of the 2D images is supposed to be locally uniform around the lesion of interest.
"In the case of dual-energy tomosynthesis it is evident that two images are acquired with two different energy spectra for each angulation considered and that a contrast medium has been earlier injected in the patient.
"The acquisition is executed by a detector Det situated opposite a source of X-rays, for example a digital camera or a solid detector based on amorphous silicon or amorphous selenium.
"Application of tomosynthesis is detection and characterisation of a lesion in an organ, for example a cancerous lesion.
"In a tomosynthesis embodiment the 2D projection images are utilised to reconstruct a 3D image, and the radiologist interprets this image as a function of the differences in contrast observed.
"The reconstructed volume (VR) contains a plurality of voxels quantifying the attenuation of X-rays by matter encountered.
"In the case of an organ exhibiting a lesion it presents attenuation different to the organ.
"The result on the 3D image is a contrast difference for detecting the lesion.
"However, an intrinsic problem to tomosynthesis is the limited angular opening of the acquisition of projection images which causes in particular limited resolution according to the dimension perpendicular to the plane of the detector. Here the plane of the detector is according to the x, y axes of an orthonormal marker and the perpendicular dimension is according to the z axis of this same marker.
"Poor resolution in the z dimension perpendicular to the plane of the detector is due to the limited angular opening covered by the X-ray tube in comparison to tomography.
"In fact, to obtain isotropic resolution (identical according to all dimensions) a set of projection images right around the organ would have to be acquired continuously. Yet it is understood that this is practically impossible for tomosynthesis examination.
"Methods are known for improving the resolution of images acquired for discriminating nearby elements.
"But apart from this problem, beyond a certain thickness of a lesion (taken along the z axis), the value of the voxels making up this lesion in an image plane passing through the lesion in the reconstructed volume is not sufficient for improved identification of the type of lesion by the radiologist (benign or malignant lesion).
"The effect of this is to introduce uncertainty to the characterisation of the lesion, which can obviously compromise diagnosis.
"In other terms the reconstructed image is reliable only for lesions having minimal thickness relative to their size according to a plane which is parallel to the detector and which passes through the object."
Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "Embodiments of the invention improve the images obtained by tomosynthesis and especially those obtained by emission of X-rays with injection of contrast medium.
"And more particularly, an embodiment of the invention overcomes the lack of the contrast due to the limited angular opening characterising the path of the source of X-rays around the zone of interest during acquisition of 2D projection images in tomosynthesis.
"In particular, it prevents the value of the voxels of the 3D image from being degraded when the thickness of the object to be characterised is less than a thickness limit for a given size of object measured in a plane which is parallel to the detector and which passes through the object.
"An embodiment of the invention in fact overcomes this limit to obtain 3D images containing voxels precisely by quantifying the radio-opacity of the zone of interest.
"Thus, according to a first aspect, an embodiment of the invention relates to a method for processing images obtained by tomosynthesis comprising acquisition of a plurality of 2D projection images of a region of interest of a patient; reconstruction of a 3D digital image from the acquired 2D projection images.
"An embodiment of a method is characterised in that it comprises: detection of an object in the reconstructed 3D image; estimation of a thickness limit characteristic of a lack of the contrast of the voxels for a diameter of the object; estimation of the thickness of the object; comparison of the thickness of the object to the thickness limit; and in that if the thickness of the object is less than the thickness limit, the method further comprises application at least to the voxels of the object in the reconstructed image of a multiplicative corrective factor equal to the ratio between the thickness limit and the thickness of the object.
"An embodiment of the method therefore produces a 3D image of the organ containing the object to be characterised whereof the voxels are proportional to the physical size characteristic of the radio-opacity of the object.
"According to a second aspect, an embodiment of the invention relates to a medical imaging system comprising means for a method embodiment according to the first aspect of the invention.
"And according to a third aspect, an embodiment of the invention relates to a computer program, characterised in that it comprises machine instructions for using a method according to the first aspect of the invention."
For the URL and additional information on this patent, see: Muller, Serge; Puong, Sylvie. Method for Processing Images Obtained by Tomosynthesis and Associated Device. U.S. Patent Number 8798348, filed
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