SYSTEM, METHOD, AND COMPUTER-ACCESSIBLE MEDIUM FOR NON-INVASIVE TEMPERATURE ESTIMATION
20210161394 · 2021-06-03
Assignee
Inventors
- SAIRAM GEETHANATH (New York, NY, US)
- Julie Marie KABIL (New York, NY, US)
- JOHN THOMAS VAUGHAN, JR. (New York, NY, US)
Cpc classification
G01R33/5608
PHYSICS
A61B5/055
HUMAN NECESSITIES
G16H50/20
PHYSICS
G06N3/082
PHYSICS
A61B5/01
HUMAN NECESSITIES
International classification
A61B5/01
HUMAN NECESSITIES
A61B5/055
HUMAN NECESSITIES
Abstract
Exemplary system, method and computer-accessible medium for estimating a temperature on a portion of a body of an anatomical structure(s) can be provided, using which it is possible to, for example, receive a plurality of magnetic resonance (MR) images for the anatomical structure(s), segment the MR images into a plurality of tissue types, mapping the tissue types to a tissue property(ies), and estimate the temperature on the portion of the body of the patient(s) using a neural network. The tissue property(ies) can include a conductivity, a permittivity, or a density. The density can be a mass cell density. The neural network can be a single neural network. The temperature can be estimated based on a set of vectors between points on the portion of the body and a temperature sensor. Each vector can correspond to a tissue thermal profile for each point.
Claims
1. A non-transitory computer-accessible medium having stored thereon computer-executable instructions for estimating a temperature on a portion of a body of at least one anatomical structure, wherein, when a hardware computing arrangement executes the instructions, the hardware computing arrangement is configured to perform procedures comprising: receiving a plurality of magnetic resonance (MR) images for the at least one anatomical structure; segmenting the MR images into a plurality of tissue types; mapping the tissue types to at least one tissue property; and estimating the temperature on the body of the at least one patient using a neural network.
2. The computer-accessible medium of claim 1, wherein the at least one tissue property includes at least one of a conductivity, a permittivity or a density.
3. The computer-accessible medium of claim 1, wherein the density is a mass cell density.
4. The computer-accessible medium of claim 1, wherein the neural network is a single neural network.
5. The computer-accessible medium of claim 1, wherein the hardware computing arrangement is configured to estimate the temperature based on a set of vectors between points on the body and a temperature sensor.
6. The computer-accessible medium of claim 1, wherein each of the vectors corresponds to a tissue thermal profile for each respective point.
7. The computer-accessible medium of claim 6, wherein the hardware computing arrangement is further configured to map the temperature at each respective point.
8. The computer-accessible medium of claim 7, wherein the hardware computing arrangement is configured to map the temperature at each respective point using the neural network.
9. The computer-accessible medium of claim 7, wherein the hardware computing arrangement is configured to map the temperature at each point using a Euclidean distance between each respective point and a temperature sensor.
10. The computer-accessible medium of claim 1, wherein the portion of the body is on a surface of the at least one anatomical structure.
11. The computer-accessible medium of claim 1, wherein the portion of the body is internal to the at least one anatomical structure.
12. The computer-accessible medium of claim 1, wherein the tissue types include at least one of (i) Fat, (ii) Grey Matter, (iii) Bone, (iv) Muscle, or (iv) Cerebrospinal Fluid.
13. The computer-accessible medium of claim 1, wherein the hardware computing arrangement is further configured to train the neural network.
14. The computer-accessible medium of claim 13, wherein the hardware computing arrangement is configured to train the neural network by segmenting the tissue types of at least one further anatomical structure.
15. The computer-accessible medium of claim 14, wherein the tissue types include at least one of (i) Fat, (ii) Grey Matter, (iii) Bone, (iv) Muscle, of (iv) Cerebrospinal Fluid.
16. The computer-accessible medium of claim 13, wherein the hardware computing arrangement is configured to train the neural network by varying a number of hidden nodes in the neural network.
17. The computer-accessible medium of claim 1, wherein the neural network includes (i) three layers, and (ii) a Rectified linear Unit activation function.
18. The computer-accessible medium of claim 1, wherein the at least one anatomical structure is a brain of a patient, and wherein the MR images are brain slices of the brain of the patient.
19. A method for estimating a temperature on a portion of a body of at least one anatomical structure, comprising: receiving a plurality of magnetic resonance (MR) images for the at least one anatomical structure; segmenting the MR images into a plurality of tissue types; mapping the tissue types to at least one tissue property; and using a hardware computing arrangement, estimating the temperature on the body of the at least one patient using a neural network.
20-36 (canceled)
37. A system for estimating a temperature on a portion of a body of at least one anatomical structure, comprising: a hardware computing arrangement configured to: receive a plurality of magnetic resonance (MR) images for the at least one anatomical structure; segment the MR images into a plurality of tissue types; map the tissue types to at least one tissue property; and estimate the temperature on the body of the at least one patient using a neural network.
38-54. (canceled)
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Further objects, features and advantages of the present disclosure will become apparent from the following detailed description taken in conjunction with the accompanying Figures showing illustrative embodiments of the present disclosure, in which:
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[0047] Throughout the drawings, the same reference numerals and characters, unless otherwise stated, are used to denote like features, elements, components or portions of the illustrated embodiments. Moreover, while the present disclosure will now be described in detail with reference to the figures, it is done so in connection with the illustrative embodiments and is not limited by the particular embodiments illustrated in the figures and the appended claims.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Exemplary Non-Invasive Temperature Estimation
[0048] For example, an object O ({right arrow over (r)}) can be provided with an internal spatial temperature distribution T({right arrow over (r)}) with {right arrow over (r)} representing the three dimensional spatial vector r(x, y, and z). Let T({right arrow over (r)}) be altered through the application of an external heating source such as the application of radio frequency pulses during a magnetic resonance imaging (“MRI”) experiment. This can cause changes in T(r) depending on a multitude of factors. Some examples of such factors can include the characteristics of the heat source, material composition of the object relating to corresponding electro-thermal properties, position of the object, capabilities of the object to regulate the changes in temperature, etc. In the case of in vivo studies utilizing MRI, this can map to radio frequency (“RF”) Transmitter ({right arrow over (θ)}.sub.RFT) and Pulse Sequence Design ({right arrow over (θ)}.sub.PSD) parameters, tissue thermal properties ({right arrow over (θ)}.sub.TP), posture ({right arrow over (θ)}.sub.POS) thermos-physiological regulation ({right arrow over (θ)}.sub.Tphy) capabilities, etc. Thus, for example:
T({right arrow over (r)})=f({right arrow over (θ)})
{right arrow over (θ)}=f({right arrow over (θ)}.sub.RFT, {right arrow over (θ)}.sub.PSD, {right arrow over (θ)}.sub.TP, {right arrow over (θ)}.sub.POS, {right arrow over (θ)}.sub.Tphy, . . . ) [1]
[0049] The surface temperature (T.sub.S({right arrow over (r)})) of the object can be measured through one of the exemplary modalities described herein. The number of these sensors can be N.sub.s. The temperature changes in these measurements can be caused by the internal heat changes in the object and the heat source.
[0050] There can be N.sub.P points inside O ({right arrow over (r)}) whose temperatures have to be estimated. For a point Q (T.sub.Q({right arrow over (r)})) inside of O({right arrow over (r)}), there can be N.sub.s observations of surface temperatures (T.sub.S({right arrow over (r)})). Changes in the temperature at point Q can cause changes (e.g., widely ranging from subtle to significant) in T.sub.S({right arrow over (r)}). Thus, for example:
T.sub.S({right arrow over (r)})=f(T.sub.Q({right arrow over (r)})) [2]
[0051] These N.sub.s observations can also be impacted by changes in the other (N.sub.P−1) points inside O ({right arrow over (r)}. Now consider a set of vectors between point Q and the temperature sensors T.sub.S({right arrow over (r)}). MR images of the object can be included. These can be segmented into different tissue types and subsequently mapped to tissue/material properties such as conductivity, permittivity, mass cell density, etc. Each of the N.sub.P points can now have associated vectors corresponding to tissue thermal profiles (P.sub.N.sub.
P.sub.Q−T.sub.
[0052] This can then be cast as a neural network based inverse problem of mapping temperature {circumflex over (T)}.sub.N.sub.
{circumflex over (T)}.sub.N.sub.
[0053] The exemplary formulation can be simplified by converting the problem from that of regression to multi-class classification. This can be possible in the context of in vivo human imaging due to the well-defined range of temperature (e.g., 37° C.-41° C.) as well as a precision of 0.1° C. that can be beneficial for applications dependent on temperature estimation. This can define the number of labels (k) for the formulation. The operator f (.) can be evaluated by the neural network. In relation to existing thermal solvers, this can correspond to the joint estimation of SAR and temperature maps while including two additional inputs of the normal metric and surface temperatures. Thus, for example:
{dot over ({circumflex over (T)})}.sub.N.sub.
where, for example:
{dot over ({circumflex over (T)})}.sub.N.sub.
[0054] The training phase can then include the actual temperature at point Q as an input in addition to the thermal tissue profile vector (P.sub.Q−T.sub.
[0055] It can be beneficial to non-invasively estimate the temperature of the internal portions of an object through the training and testing of a fast, efficient neural network as a multi-class classification supervised learning problem. In particular, these can correlate well with state-of-the art thermal solvers that can be routinely used for simulations and temperature related downstream decisions in MRI.
Exemplary Methods
[0056] Application to MR based Thermometry Simulations
[0057] The formulation was tailored to provide in vivo temperature maps under the influence of radio frequency pulses at 3T. This included generation of the thermal vectors, internal and surface temperatures for a human model using CST. This data was then utilized by the neural network separately for training and testing.
Exemplary CST Simulations
[0058] The simulations to acquire temperature maps were performed using the CST Studio Suite software 2018 (e.g., CST Darmstadt, Germany). The procedure step was to model a 16 rung birdcage head coil and tune it to 128 MHz, by adjusting its capacitance values, using a circular polarization to have a homogeneous RF field. Then, a human numerical model, Tom, was imported. (See e.g., diagram shown in
[0059] Once the exemplary model was set up, an exemplary mesh (e.g,, more than 16 million cells) was used to ensure the accuracy of the results. Then, the electromagnetic simulation using the Time-Domain solver was performed and completed in approximately 10 hours. The electromagnetic simulation results wore then provided to the thermal simulation which used the Pennes' Bioheat equation. The Thermal transient solver was performed for an about 100 seconds-duration and the temperature was recorded using a three dimensional (“3D”) monitor with a recording step of 10 seconds. The thermal simulation took about 15 minutes to complete. The thermal maps were obtained at about 100 seconds and extracted temperature data from different brain slices, for training and test purposes.
Exemplary CST Data Processing
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Exemplary Neural Network Architecture
[0061] Exemplary neural network architecture was selected based on the following exemplary features:
[0062] Exemplary Rapid inference: It can be beneficial to facilitate near real-time computation of the temperature maps given that the whole body MRI data approximately consists of 16 million points (e.g., Np) for a resolution of 2 mm×2 mm×2 mm. This resulted in the need of shallow networks.
[0063] Exemplary True multi-class classification: It was beneficial to use a hybrid binary and multi-class classification network to enable a variable number of classes and temperature increments.
[0064] Exemplary Limited number of tunable hyper-parameters: The chosen network can be limited to facilitate simplicity ease-of-use, reproducibility and robustness
[0065] These desired features resulted in the choice of Extreme Learning Machines (“ELM”) as the neural network architecture for NITS. An ELM implemented on tensorflow was utilized for demonstration of the formulation. For example, the only tunable hyper-parameter in ELMS can be the number of hidden nodes. The number of nodes was varied from 512 to 2560 to determine validation test accuracy. For this implementation, 2048 hidden nodes (e.g., corresponding to the highest attained accuracy of 82%) with sigmoid as the activation function and with softmax providing the utilized probabilities for multi-class classification were chosen.
Exemplary Input and Validation Data Features and Training
[0066] The input data for training included 6690 examples derived from one slice of the brain CST simulations. The validation set was chosen to be 134 examples corresponding to 2% of the training data. The chosen training data was the slice with the highest temperature range (e.g., 37.1 . . . 39.8° C.). This was to ensure that the network can be aware of the full range of temperatures it was likely to see during testing. The tissue thermal vector (P.sub.N.sub.
Exemplary Training Labels (Ground Truth)
[0067] The temperature range was divided into segments each separated by 0.1° C. This resulted in 28 bins for the temperature range. This vector was stored for translation between actual temperatures and the labels (e.g., indices of the vector) for training.
Exemplary Input Data-Testing
[0068] The trained network was saved as a model and utilized for testing. A slice of the brain about 5 mm from the training slice was utilized for testing. All points in each of the two dimensional slice along with the corresponding features were flattened and reshaped to the dimensions similar to the ones described for the training data. The resulting labels were converted to temperature bins each of width 0.1° C.
Exemplary Error Quantitation and Statistical Analysis
[0069] Training and test results were correlated with CST simulations. The temperatures from CST simulations were binned correspondingly to enable discrete comparisons between the two approaches. A paired t-test was performed to evaluate statistical significance. All statistical evaluations were performed using graphpad Prism.
Exemplary Computational Resources and Performance
[0070] All CST computations performed using the Time-Domain solver was accelerated by a graphics processing unit (“GPU”). These calculations were performed with a workstation equipped with 4 Nvidia Tesla K-80 cards. The neural network implementation was performed on a custom Digital Storm computer with i9 Intel Processor, and 4 NVidia GPU Tesla cards of 12 GB each. The total time for training over 5 trials was tabulated. The testing/inference performance for each of the N slices was recorded.
[0071] An electromagnetic/thermal co-simulation was performed using CST (e.g., Dassault Systèmes, France). A 16 rungs 3T birdcage head coil was modeled. A human numerical model (e.g., “Tom”, adult male from the CST Voxel Family) was imported in the head coil with a 2 mm isotropic resolution. (See, e.g., exemplary diagram shown in
[0072] The exemplary (e.g., thermal) maps shown in
[0073] The input was a matrix with 35 features for each point: 33 tissue properties (e.g., 3 properties for each of the 11 segments), 1 norm distance to one of the four sensors, 1 temperature value. Each point was represented 4 times to consider the distance and properties to the 4 sensors. Random Gaussian noise with standard deviation 0.05 was added to provide for data augmentation. The exemplary hyper-parameters were optimized to improve the accuracy while avoiding over-fitting the model to the training slice. The estimated temperature maps for test slices were plotted, compared to the simulated maps and the correlation between the prediction and the true temperature was assessed.
Exemplary Results
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[0075] For this phantom with a height of 174 cm, the total NITE computation time at resolution of 2 mm resulted in 870 slices. This was computed by NITE in 3.7 minutes without the use of parallelization through GPU. This acceleration was based on the rapid inferencing of the ELMS. Also, the results illustrate how the exemplary NITE can non-invasively map temperature learning from surface temperature and tissue thermal properties (e.g., MR images). This can be validated by the qualitative comparison of
[0076] The exemplary system, method, and computer-accessible medium, according to an exemplary embodiment of the present disclosure, may not need to utilize invasive temperature measurement probes leading to challenges related to measurement and the sample. Accelerated temperature estimation can be achieved due to the utilization of deep learning rather than Finite Difference Time Domain or Frequency Domain simulations that can be computationally expensive. The exemplary system, method, and computer-accessible medium, according to an exemplary embodiment of the present disclosure, can utilize thermal simulation data, sample composition, and surface temperature measurements to compute internal temperature map estimates. For temperature estimation of MR subjects, the exemplary system, method, and computer-accessible medium may only utilize images as compared to other methods that specifically utilize MR thermometry based acquisition methods to be performed. For non-destructive testing, the exemplary system, method, and computer-accessible medium can utilize information from the material properties of the sample and surface temperature data to provide temperature estimates underutilized experimental conditions such as but not limited to direct heating, thermal ablation, etc.
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[0078] An accuracy of 86% was obtained for the training by adjusting the neural network parameters and using a random dropout method. A positive, linear correlation was observed. However, given the structural differences between the training slice and the test slices, the linearity may not yet be optimal: the further away from the training slice, the less accurate the prediction becomes. Table 1 below shows an illustration of a comparison of time performance between the exemplary NITE and CST for the whole body for CST, and one brain slice for NITE after training. For example, 870 slices may be beneficially used for the whole body with a resolution of 2 mm, resulting in an approximate computation time of 2.5 minutes for the exemplary NITE. Once trained, the exemplary neural network can generate the maps several orders of magnitude faster. The exemplary system, method and computer-accessible medium, according to an exemplary embodiment of the present disclosure, can be modified by tuning more finely the random dropout, optimizing the time or adjusting the number of nodes, and afterwards testing on brain slices with bigger structural differences. Alternatively or in addition, a brain volume (e.g., TOM's) can be trained and tested on other models such as DUKE. Then, an in-vitro review can be performed on a phantom with surface and internal temperature sensors to validate the exemplary method experimentally.
TABLE-US-00001 TABLE 1 CST total simulation time: Whole Body 10.25 hours NITE total calculation time: training Training (to do once): 1.6 hours and testing on 1 slice Testing: 172 ms per slice NITE estimate total calculation time: 2.5 minutes Test on Whole Body 870 slices with a resolution of 2 mm
[0079] Time-efficiency and radiofrequency safety can be beneficial in MRI protocols. Although MR Thermometry procedures exist, including for example T1 relaxation and proton resonance frequency shift, their sensitivity or their acquisition time can be prohibitive. (See, e.g., Reference 1). The exemplary system, method and computer-accessible medium according to an exemplary embodiment of the present disclosure can include a personalized, non-invasive approach. For example, knowing the tissue properties and distance to several surface temperature sensors and the surface temperature, the exemplary system, method and computer-accessible medium can be used to accurately predict the internal body temperature. In a brain slice, e.g., N points can be considered where it can be beneficial to know/determine the temperature. Thus, N.sub.2 surface temperature sensors can be considered/analyzed. For each point N.sub.P in N, an additional set of i equidistant points placed on an imaginary line between one surface sensor and N.sub.P can be considered/analyzed. Using MR1 procedure(s), the images can be acquired and segmented to attribute to each point it tissue properties. Considering this as a classification problem with a defined precision, for example 0.1° C., a neural network model can be trained on a numerical brain slice with multiple points using their attributes (e.g., tissue properties, distance to tour surface sensors and known temperatures acquired through simulation). This exemplary model and/or the exemplary attributes can then be tested on two other slices and compared with the real values to estimate the accuracy.
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[0082] As shown in
[0083] Further, the exemplary processing arrangement 805 can be provided with or include an input/output ports 835, which can include, for example a wired network, a wireless network, the internet, an intranet, a data collection probe, a sensor, etc. As shown in
[0084] The foregoing merely illustrates the principles of the disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements, and procedures which, although not explicitly shown or described herein, embody the principles of the disclosure and can be thus within the spirit and scope of the disclosure. Various different exemplary embodiments can be used together with one another, as well as interchangeably therewith, as should be understood by those having ordinary skill in the art. In addition, certain terms used in the present disclosure, including the specification, drawings and claims thereof, can be used. synonymously in certain instances, including, but not limited to, for example, data and information. It should be understood that, while these words, and/or other words that can be synonymous to one another, can be used synonymously herein, that there can be instances when such words can be intended to not be used synonymously. Further, to the extent that the prior art knowledge has not been explicitly incorporated by reference herein above, it is explicitly incorporated herein in its entirety. All publications referenced are incorporated herein by reference in their entireties.