Calibration for 3D reconstruction of medical images from a sequence of 2D images
Provided herein are systems and methods (i.e., utilities) that are directed to correcting misalignments or offsets between a series or sequence of medical images. The utility corrects offsets between a series of medical images obtained where an imaging device (e.g., ultrasound probe) is supported by a positioning mechanism where there is misalignment between an imaging axis or other reference point of the imaging device and the axis of movement of the positioning device. The determination of this offset between these axis allows for calculating a transformation that allows for placing each of the series images into a common frame of reference.
1. A method for calibrating images obtained from an ultrasound imaging device where the imaging device is supported by a positioning mechanism, comprising:
obtaining at least first and second images from an ultrasound imaging device while said positioning device supports the ultrasound imaging device in first and second positions, respectively, wherein the first and second of images are obtained through rotation of said ultrasound imaging device about an axis of rotation wherein the first and second images are mirror images acquired at angles 180 degrees apart, wherein said positioning mechanism is designed to limit movement of said ultrasound imaging device to said axis of rotation between said first and second positions;
identifying a first distance between said an object in said first image and a known reference point in said first image;
identifying a second distance between said object in said second image and the known reference point in the second image;
determining a difference in said first and second distances; and
calculating a transformation, based on said differences of said first and second images, wherein said transformation defines a calibration of offsets between said reference point of said ultrasound images and said axis of movement of said positioning mechanism.
2. The method of claim 1 , further comprising:
acquiring a sequence of two-dimensional (2D) images of an anatomical object using said ultrasound imaging device as supported by said positioning mechanism, wherein said 2D images are acquired at different positions about said axis of movement; and
applying said transformation to each of said sequence of 2D images, wherein said transformation places said 2D images in a common frame of reference to define a sequence of corrected 2D images.
3. The method of claim 2 , wherein:
said obtaining at least first and second images and calculating said transformation is performed during a common procedure while acquiring said sequence of images.
4. The method of claim 3 , wherein said first and second images are part of said sequence of images.
5. The method of claim 2 , further comprising:
reconstruct said sequence of corrected 2D images to generate a 3D image of said anatomical object.
6. The method of claim 5 , wherein said transformation updates the correlation between real world and image frames during a medical procedure, wherein said medical procedure is performed under 3D image guidance.
7. The method of claim 5 , wherein registering said sequence of 2D images provides real world to image space calibration.
8. The method of claim 2 , further comprising:
preprocessing said sequence of 2D images to remove at least one of speckle and shadow.
9. The method of claim 2 , wherein said image reference point comprises an image axis, wherein said transformation accounts for offsets between said image axis and said axis of movement.
10. The method of claim 2 , wherein said positioning mechanism moves said ultrasound imaging device about a rotational axis of movement.
11. The method of claim 2 , wherein said positioning mechanism moves said ultrasound imaging device about a linear axis of movement.
12. The method of claim 2 , wherein said sequence of two-dimensional (2D) images are acquired from one of a side fire ultrasound transducer and an end-fire ultrasound transducer.
13. The method of claim 1 wherein said transformation defines in-plane calibration values.
14. The method of claim 1 , wherein a plurality of pairs of images are obtained through rotation of said ultrasound imaging device about said axis of rotation such that each pair of images are mirror images acquired at angles 180 degrees apart.
15. The method of claim 1 , wherein the movement of the ultrasound imaging device is non-uniform.
16. A method for calibrating images obtained from an ultrasound imaging device where the imaging device is supported by a positioning mechanism, comprising:
obtaining at least first and second two dimensional (2D) images from an imaging device while said positioning device supports the ultrasound imaging device in first and second angular positions at angles 180 degrees apart, respectively, wherein said positioning mechanism is designed to limit movement of said ultrasound imaging device to a rotational axis of movement between said first and second angular positions;
identifying a first distance between an object in said first image and an imaging axis of said first 2D ultrasound image;
identifying a second distance between said object in said second image and the imaging axis of said second 2D ultrasound image;
determining a difference in said first and second distances; and
calculating a transformation, based on said difference, wherein said transformation defines a calibration of offsets between said imaging axis of said 2D ultrasound images and said rotational axis of said positioning mechanism.
17. The method of claim 16 , wherein obtaining comprises obtaining a plurality of pairs of 2D ultrasound images where each pair of images are 180 degrees apart.
18. The method of claim 17 , further comprising;
identifying first and second distances between an object in each pair of images and said imaging axis of each image;
determining differences between said first and second distances of each pair of images;
calculating said transformation, based on said differences.
19. The method of claim 18 , further comprising:
acquiring a sequence of two-dimensional (2D) images of an anatomical object using said ultrasound imaging device as supported by said positioning mechanism, wherein said 2D images are acquired at different positions about said axis of movement; and
applying said transformation to each of said sequence of 2D images, wherein said transformation places said 2D images in a common frame of reference to define a sequence of corrected 2D images.
20. The method of claim 19 , further comprising:
reconstruct said sequence of corrected 2D images to generate a 3D image of said anatomical object.
21. A system for use in obtaining and calibrating images obtained from an ultrasound imaging device supported by a positioning mechanism, comprising:
an ultrasound imaging probe operative to obtain two-dimensional (2D) ultrasound images;
a positioning mechanism adapted to support said ultrasound imaging probe and move said ultrasound imaging probe between first and second mirror positions at angles 180 degrees apart, wherein said positioning mechanism limits movement of said probe to a single degree of freedom relative to a rotational axis;
a processor operative to:
receive first and second 2D ultrasound images from said ultrasound imaging device at said first and second mirror positions,
identify a first distance between an object in said first 2D ultrasound image and an imaging axis of said first 2D ultrasound image;
identify a second distance between said object in said second 2D ultrasound image and the imaging axis of said second 2D ultrasound image; and
calculate a transformation, based on differences in said first and second distances, wherein said transformation defines a calibration of offsets between said imaging axis of said first and second 2D ultrasound images and said rotational axis of said positioning mechanism.
22. The system of claim 21 , wherein said processor if further operative to:
receive a sequence of two-dimensional (2D) images of an anatomical object from said ultrasound imaging device as supported by said positioning mechanism, wherein said 2D images are acquired at different positions relative to said movement axis;
apply said transformation to each of said sequence of 2D ultrasound images, wherein said transformation places said 2D images in a common frame of reference to define a sequence of corrected 2D images; and
reconstruct said sequence of corrected 2D images to generate a 3D image of said anatomical object.
23. The system of claim 22 , further comprising:
a monitor operative to output said 3D image.