Feature Tracking Using Ultrasound
Various implementations of the invention provide techniques and supporting systems that facilitate real-time or near-real-time ultrasound tracking for the purpose of calculating changes in anatomical features during a medical procedure. More specifically, anatomical features within a patient undergoing a medical procedure are tracked by obtaining temporally-distinct three dimensional ultrasound images that include the feature of interest and obtaining a targeted subset of ultrasound images focused on the feature. Based on the targeted subset of ultrasound images, a displacement of the feature is determined and image parameters used to obtain the targeted subset of ultrasound images are adjusted based on the displacement. This results in a time-based sequence of three dimensional images and targeted ultrasound images of the feature that identify changes in the position, size, location, and/or shape of the feature.
1 . A computer-implemented method for tracking an anatomical feature of interest within a patient undergoing a medical procedure, the method comprising:
obtaining from a memory device a three dimensional image of a region of interest wherein the region of interest includes the feature of interest at a first periodicity;
determining a location of the feature of interest in the region of interest; and
by a processor, iteratively obtaining temporally-displaced targeted subsets of ultrasound images at a periodicity greater than the first periodicity focused on the determined location, each subset being compared with the three dimensional image and determining, based on each comparison, a displacement of the feature.
2 . The method of claim 1 further comprising determining if the displacement exceeds a displacement threshold and if so, obtaining an updated three dimensional image of the region of interest sooner than would be obtained according to the first periodicity.
3 . The method of claim 1 wherein the displacement threshold comprises an upper limit of spatial displacement of the feature of interest.
4 . The method of claim 1 further comprising determining if the displacement exceeds a safety threshold and if so, halting the medical procedure to allow for one or more adjustments to the patient's orientation with respect to a treatment device.
5 . The method of claim 1 further comprising adjusting one or more image parameters used in obtaining the targeted subset of ultrasound images based on the displacement.
6 . The method of claim 1 further comprising continuously adjusting one or more treatment apparatus in response to the displacement without interrupting the medical procedure.
7 . The method of claim 6 wherein the treatment apparatus comprises one or more of a treatment couch and a multi-leaf collimator.
8 . The method of claim 1 wherein the targeted subset comprises a series of two dimensional image slices of the feature.
9 . The method of claim 1 wherein the targeted subset comprises two or more tracking planes.
10 . The method of claim 9 wherein one or more of the tracking planes comprise reconstructed planes.
11 . The method of claim 1 wherein the targeted subset further comprises three dimensional ultrasound datasets related to a limited region of interest.
12 . The method of claim 11 wherein the limited reduced region of interest is based at least in part on an adjusted sector size.
13 . The method of claim 11 wherein the limited reduced region of interest is based at least in part on an adjusted image depth.
14 . The method of claim 11 wherein the limited reduced region of interest is based at least in part on an adjusted ultrasound sector angle.
15 . The method of claim 1 wherein the targeted subset further comprises three dimensional ultrasound datasets having a reduced resolution.
16 . The method of claim 1 wherein the three dimensional ultrasound images are obtained using a motorized probe.
17 . The method of claim 1 wherein the three dimensional ultrasound images are obtained using a biplanar probe.
18 . The method of claim 1 wherein the three dimensional ultrasound images are obtained using a matrix probe.
19 . The method of claim 1 wherein the three dimensional ultrasound images are obtained using a three dimensional ultrasound probe placed external to the patient.
20 . The method of claim 1 wherein the three dimensional ultrasound images are obtained using a three dimensional ultrasound probe placed internal to the patient.
21 . The method of claim 1 wherein the medical procedure comprises external beam radiotherapy.
22 . The method of claim 1 wherein the medical procedure comprises obtaining one or more planning images for radiotherapy.
23 . The method of claim 1 wherein the feature comprises an organ.
24 . The method of claim 1 further comprising segmenting a subset of the targeted images.
25 . The method of claim 1 wherein the comparison comprises comparing grey-scale values of a subset of the targeted images.
26 . The method of claim 1 wherein the targeted subset of ultrasound images are obtained using an ultrasound probe having trackable markers affixed thereto.
27 . The method of claim 26 wherein the trackable markers are tracked over time using a tracking system.
28 . The method of claim 26 wherein the trackable markers are calibrated to pixels within the targeted subset of ultrasound images.
29 . The method of claim 1 wherein the feature comprises a prostate gland and the targeted subset of ultrasound images are obtained transperineally.
30 . A system for tracking an anatomical feature of interest within a patient undergoing a medical procedure, the system comprising:
a processor configured to: (i) locate the feature of interest within a series of three dimensional images of a region of interest obtained at a first periodicity wherein the region of interest includes the feature of interest, (ii) iteratively comparing temporally displaced targeted subsets of ultrasound images obtained at a periodicity greater than the first periodicity with the three dimensional image, and (iii) determining, based on each comparison, a displacement of the feature of interest; and
a register for receiving and storing the three dimensional image and the temporally displaced targeted subsets of ultrasound images.
31 . The system of claim 30 wherein the processor is further configured to determine if the displacement exceeds a displacement threshold and if so, provide instructions to obtain an updated three dimensional image of the region of interest sooner than would be obtained based on the first periodicity.
32 . The system of claim 31 wherein the displacement threshold comprises an upper limit of spatial displacement of the feature of interest.
33 . The system of claim 30 wherein the processor is further configured to determine if the displacement exceeds a safety threshold and if so, provide instructions to halt the medical procedure to allow for one or more adjustments to the patient's orientation with respect to a treatment device prior to reinstating the procedure.
34 . The system of claim 30 further comprising an ultrasound probe for providing the images.
35 . The system of claim 31 wherein the ultrasound probe comprises a two dimensional ultrasound probe and a housing into which the ultrasound probe is rotatably mounted, thereby providing at least one degree of freedom of movement of the probe within the housing.
36 . The system of claim 35 further comprising a motor for causing the probe to oscillate within the housing according to the at least one degree of freedom.
37 . The system of claim 31 wherein the ultrasound probe further comprises trackable markers affixed thereto.
38 . The system of claim 31 further comprising a controller for providing the adjusted imaging parameters to the ultrasound probe.
39 . The system of claim 30 further comprising a display for displaying the images.