Transcranial photoacoustic/thermoacoustic tomography brain imaging informed by adjunct image data
Systems and methods of reconstructing photoacoustic imaging data corresponding to a brain of a subject through a skull of a subject utilizing a reconstruction method that incorporates a spatial model of one or more acoustic properties of the brain and skull of the subject derived from an adjunct imaging dataset.
1. A method of imaging a brain situated within a skull of a subject, comprising:
obtaining an adjunct image dataset corresponding to the skull of the subject being imaged;
analyzing the adjunct image dataset to specify one or more parameters of a spatial model of the skull;
obtaining one or more photoacoustic imaging signals corresponding to the brain of the subject through the skull of the subject at a photoacoustic tomography (PAT) coordinate system, wherein obtaining the one or more photoacoustic imaging signals comprises directing, with at least one laser pulse, illumination of the skull of the subject, wherein a first fraction of the at least one laser pulse passes through the skull to illuminate the brain, wherein a second fraction of the at least one laser pulse reflects off a surface of the subject, wherein a photon recycling device reflects at least a portion of the second fraction of the at least one laser pulse back towards the brain as recycled laser light to further illuminate the brain, and wherein the one or more photoacoustic imaging signals include (a) acoustic signals generated by the brain of the subject in response to illumination by the first fraction of the at least one laser pulse and (b) acoustic signals generated by the brain of the subject in response to illumination of the brain by the recycled laser light from the photon recycling device;
determining the PAT coordinate system using the one or more photoacoustic imaging signals;
registering the spatial model to the PAT coordinate system to establish an imaging model; and
reconstructing a photoacoustic image from the one or more photoacoustic imaging signals of the brain of the subject by implementing an image reconstruction method configured to mitigate aberrations of the one or more photoacoustic imaging signals induced by the skull of the subject using the imaging model and the one or more imaging photoacoustic signals.
2. The method of claim 1 , wherein the adjunct image dataset is obtained using an X-ray computed tomography scanning device or a magnetic resonance imaging device.
3. The method of claim 2 , wherein the adjunct image dataset comprises a spatial map of porosity and acoustic properties comprising a speed of sound and an ambient density.
4. The method of claim 3 , wherein the image reconstruction method is chosen from a time-reversal reconstruction method and an iterative reconstruction method.
5. The method of claim 4 , wherein the image reconstruction method is the time-reversal reconstruction method, and wherein the time-reversal reconstruction method comprises solving discretized forms of acoustic equations describing a propagation of an acoustic wavefield though a heterogeneous medium subject to one or more initial conditions corresponding to an initial photoacoustically generated wavefield within the medium and an initial acoustic particle velocity of zero throughout the medium to obtain the photoacoustic image corresponding to a spatial distribution of an initial acoustic wavefield, wherein the initial acoustic wavefield is proportional to an absorbed optical energy density.
6. The method of claim 5 , wherein the discretized forms of the acoustic equations are solved using a numerical algorithm comprising one or more of a real-space finite-element method, a real-space finite-difference method, and a k-space pseudospectral method.
7. The method of claim 6 , wherein the numerical algorithm is the k-space pseudospectral method.
8. The method of claim 4 , wherein the image reconstruction method is the iterative reconstruction method comprising iteratively solving a discretized imaging model comprising a system matrix to obtain the photoacoustic image corresponding to a spatial distribution of an initial acoustic wavefield, wherein the initial acoustic wavefield is proportional to an absorbed optical energy density.
9. The method of claim 8 , wherein the iterative reconstruction method solves the discretized imaging model using an optimization relation.
10. The method of claim 9 , wherein the optimization relation is a total variation-regularized penalized least-squares cost function.
11. The method of claim 1 , further comprising generating a second photoacoustic image and subjecting the photoacoustic image and the second photoacoustic image to a differential imaging method comprising subtracting the second photoacoustic image from the photoacoustic image to obtain a differential image.
12. The method of claim 11 , wherein the differential image is subjected to a high-pass filter.
13. The method of claim 11 , wherein the photoacoustic image corresponds to the brain and the skull of the subject at a first condition and the second photoacoustic image corresponds to the brain and the skull of the subject at a second condition.
14. The method of claim 13 , wherein the first condition comprises an untreated baseline condition and the second condition comprises a condition after a treatment, wherein the treatment is chosen from: a change in an endogenous contrast agent, an introduction of an exogenous contrast agent, a therapeutic treatment, and a performance of a cognitive task.
15. The method of claim 1 , wherein illuminating of the skull of the subject with the at least one laser pulse comprises directing the at least one laser pulse through a concave lens of the photon recycling device.
16. The method of claim 1 , wherein reflecting at least the portion of the second fraction of the at least one laser pulse back towards the brain of the subject as recycled laser light comprises reflecting laser light off of a concave surface of the photon recycling device.
17. The method of claim 16 , wherein the concave surface of the photon recycling device has an elliptical parabaloid curvature.
18. The method of claim 1 , wherein the second fraction of the at least one laser pulse reflects off a surface of the skull of the subject.
19. The method of claim 1 , wherein the image reconstruction method is configured to account for shear wave mode conversion.
20. The method of claim 1 , wherein obtaining the one or more photoacoustic imaging signals corresponding to the brain of the subject through the skull of the subject further comprises receiving, using at least one ultrasonic transducer, (a) the acoustic signals generated by the brain of the subject in response to illumination by the first fraction of the at least one laser pulse and (b) the acoustic signals generated by the brain of the subject in response to illumination of the brain by the recycled laser light from the photon recycling device.