System and method for estimating an indicator of the tissue activity of an organ
The invention relates to a system and method for quantifying a novel biomarker of the tissue activity of a human or animal organ. By way of preferred application, such a biomarker describes the diffusivity of biological fluids in living tissues in the form of a novel indicator of the diffusion of water molecules in living tissues on the basis of diffusion data resulting from the acquisition of a sequence of images of one or more parts of the body of an animal or human patient. Particularly resistant and stable with respect to noise present in the medical imaging signals from which the experimental data stem, the novel biomarker is relevant in a large number of applications including, inexhaustively, the analysis and/or monitoring of cancers, or the assessment of strokes.
1 . A method for quantifying a biomarker of an elementary volume, called “voxel”, of an organ of a human or animal patient, said method being implemented by a processing unit of a diffusion MRI imaging analysis system, and comprising steps for:
generating the value of said biomarker, hereinafter denoted “tissue activity indicator” or TAI, on the basis of experimental data S(b) corresponding to the voxel, wherein said step for generating the value of said biomarker TAI comprises, over a delimited interval b min to b max of values of an acquisition parameter b corresponding to the intensity of the diffusion gradient, the calculation TAI=∫ b min b max L(b)−Γ S [S(b)] db, L(b) being a function of said acquisition parameter b and Γ S [S(b)] a bijective transformation of said experimental data S(b), wherein said experimental data S(b) is acquired from a plurality of digital image sequences obtained using an imaging device using nuclear magnetic resonance imaging;
generating an output image including a parametric map of pixels on an output human-machine interface of the diffusion MRI imaging analysis system, the output image encoding the value of said biomarker TAI for the voxel on the basis of a color gradient to express high tissue activity; and
establishing a diagnosis of a pathology among a set of pathologies including ischemic vascular accident or cancerous lesions for the human or animal patient based on the output image including the parametric map of pixels displaying the high tissue activity.
2 . The method according to claim 1 , wherein said function and bijective transformation are mutually determined, so that L(b) is greater than or equal to Γ S [S(b)] over all the values of the acquisition parameter b between b min and b max .
3 . The method according to claim 1 , wherein said function and bijective transformation are mutually determined, such that L(b min )=Γ S [S(b min )] and/or L(b max )=Γ S [S(b max )].
4 . The method according to claim 1 , the diffusion MRI imaging analysis system comprising an input human-machine interface, cooperating with the processing unit, said method comprising a step of determining the function L(b) of said acquisition parameter b and the bijective transformation Γ S [S(b)] of said experimental data S(b) on the basis of input data of a user of said input human-machine interface.
5 . The method according to claim 1 , wherein the step for generating the value of said biomarker is implemented by successive iterations for a plurality of voxels in question, said biomarker (TAI) being quantified per voxel.
6 . The method according to claim 1 , wherein the step for generating the value of said biomarker is implemented by successive iterations for a plurality of voxels in question, said biomarker (TAI) being quantified per voxel, and the step for triggering an output of said quantified biomarker (TAI) comprises generating an image in the form of a parametric map the pixels of which respectively encode the values of said quantified biomarker for the voxels in question.
7 . A non-transitory computer-readable medium storing a program comprising one or more instructions that can be interpreted or executed by a processing unit of an imaging analysis system, wherein the interpretation or execution of said instructions by said processing unit causes the implementation of a method for quantifying a biomarker (TAI) of an elementary volume according to claim 1 .
8 . An imaging analysis system comprising a processing unit, an output human-machine interface, an imaging device using nuclear magnetic resonance imaging, and an interface for communicating with the imaging device and storage media, wherein:
the imaging device arranged to emit high-frequency electromagnetic waves on a part of the body of the patient including an organ and measure a signal re-emitted by atoms of the organ to acquire a plurality of digital image sequences of the organ;
the communication interface is arranged to receive from the imaging device experimental data S(b) of an elementary volume of an organ, said experimental data S(b) acquired from the plurality of digital image sequences of the organ; and
the storage media contains instructions, the interpretation or execution of which by said processing unit causes the processing unit to:
generate a quantified biomarker of an elementary volume, called “voxel”, of an organ of a human or animal patient, hereinafter denoted “tissue activity indicator” or TAI, over a delimited interval b min to b max of values of an acquisition parameter b corresponding to the intensity of the diffusion gradient, the calculation TAI=∫ b min b max L(b)−Γ S [S(b)] db, L(b) being a function of said acquisition parameter b and Γ S [S(b)] a bijective transformation of said experimental data S(b);
generate an output image including a parametric map of pixels, the output image encoding the value of said biomarker TAI for the voxel on the basis of a color gradient to express high tissue activity; and
triggering an output of said biomarker TAI to the output human-machine interface, wherein the output of said biomarker TAI confirms a diagnosis.
9 . An imaging analysis system according to claim 8 , wherein:
the experimental data S(b) of an elementary volume of an organ are data resulting from an acquisition of a signal by diffusion MRI imaging; and
the quantified biomarker is an indicator of the diffusion of water molecules (TAI) in an elementary volume of said organ.
10 . The imaging analysis system according to claim 8 , wherein the communication interface is arranged to transmit a graphical content, associated with said quantified biomarker by the implementation of a step of for triggering an output of said quantified biomarker (TAI) in a suitable format, to an output human-machine interface.
11 . The imaging analysis system according to claim 8 , wherein the communication interface is arranged to collect input data transmitted by an input human-machine interface of said system, said input data making it possible to determine a function L(b) of the acquisition parameter b and a bijective transformation Γ S [S(b)] of said experimental data S(b).
12 . A method for quantifying a biomarker of an organ of a human or animal patient, the method comprising:
receiving, by a processing unit of a diffusion MRI imaging analysis system, experimental data as a plurality of digital image sequences obtained by an imaging device of the diffusion MRI imaging analysis system using nuclear magnetic resonance imaging;
iteratively, for each voxel of a plurality of voxels within the plurality of digital image sequences:
determining a measure of diffusion of water molecules for each voxel of a digital image sequence based on determining a difference between areas under two different curves in a an image, a first curve representing an arbitrary function of a diffusion gradient based on experimental data, and a second curve representing a bijective function, applied to a diffusion signal measured at different values of an acquisition parameter b in each of the digital images of the digital image sequence without noise reduction, wherein the diffusion signal is defined over a delimited interval;
generating a tissue activity indicator based on the measure of diffusion of water molecules for the voxel of the digital image sequence by combining the measure of diffusion of water molecules corresponding in each of the digital images; and
generating an output image of the MRI imaging analysis system, the output image including a parametric map of pixels encoding the tissue activity indicator for each of the plurality of voxels, wherein the tissue activity indicator expresses the pixels describing a high tissue activity of the organ of a human or animal patient.