Pulse-echo Imaging Research Articles

Super-Resolution Ultrasound Lamb Wave NDE Imaging of Anisotropic Airplane Laminates via Deconvolutional Neural Network

A deconvolutional neural network (DNN) is integrated into the ultrasound (UT) pulse-echo Lamb wave nondestructive evaluation (NDE) imaging technique to achieve subwavelength super-resolution defect images for the application of anisotropic composite airplane-laminated structures. First, numerical simulation has been performed to simulate the multilayer velocity–frequency dispersion relation of the symmetric and antisymmetric Lamb wave modes. Then, a super-resolution DNN is developed with all Lamb wave modes as the convolutional kernels to obtain the subwavelength defects image of the laminated structures. After that, the effectiveness of the pulse-echo Lamb wave NDE imaging technique is verified by the experimental test of a standard aluminum metal plate with three calibration holes of 2/3/5 mm diameters at the UT center frequency of 2 MHz and a line defect. Finally, the experiment of the pulse-echo Lamb wave NDE imaging technique is carried out with an L-joint coupon sample made of anisotropic graphite–epoxy airplane materials. The comparison between the experimental result and the conventional pitch-catch C-scan shows that the Lamb wave NDE technique can reveal more details of the defects, indicating its promising application in anisotropic layers’ structures defects inspection.

Training Variational Networks With Multidomain Simulations: Speed-of-Sound Image Reconstruction.

Speed-of-sound (SoS) has been shown as a potential biomarker for breast cancer imaging, successfully differentiating malignant tumors from benign ones. SoS images can be reconstructed from time-of-flight measurements from ultrasound images acquired using conventional handheld ultrasound transducers. Variational networks (VNs) have recently been shown to be a potential learning-based approach for optimizing inverse problems in image reconstruction. Despite earlier promising results, these methods, however, do not generalize well from simulated to acquired data, due to the domain shift. In this work, we present for the first time a VN solution for a pulse-echo SoS image reconstruction problem using diverging waves with conventional transducers and single-sided tissue access. This is made possible by incorporating simulations with varying complexity into training. We use loop unrolling of gradient descent with momentum, with an exponentially weighted loss of outputs at each unrolled iteration in order to regularize the training. We learn norms as activation functions regularized to have smooth forms for robustness to input distribution variations. We evaluate reconstruction quality on the ray-based and full-wave simulations as well as on the tissue-mimicking phantom data, in comparison with a classical iterative [limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS)] optimization of this image reconstruction problem. We show that the proposed regularization techniques combined with multisource domain training yield substantial improvements in the domain adaptation capabilities of VN, reducing the median root mean squared error (RMSE) by 54% on a wave-based simulation data set compared to the baseline VN. We also show that on data acquired from a tissue-mimicking breast phantom, the proposed VN provides improved reconstruction in 12 ms.

Robotic scanning technology for laser pulse‐echo inspection

The full-field pulse-echo ultrasonic propagation imaging (PE UPI) system using a two-axis linear stage has been successfully used to perform a non-destructive evaluation of flat specimens. This study used a six-axis robot arm to develop a robotic scanning algorithm that can be applied to the laser pulse-echo inspection of non-flat objects. The robotic PE UPI system was constructed and verified for both flat and curved specimens. The internal structures and defects of a honeycomb sandwich plate and a glass-fibre-reinforced polymer specimen were visualised by the robotic PE UPI system. The quality of the evaluation of the flat specimen was equivalent to that of a two-axis linear system, and the result of the curved specimen showed improvement compared to that of the linear system. The ability of the robotic scanning technique to evaluate the structural health performance of arbitrarily shaped surfaces was validated.

Ultrasound Sonography to Detect Focal Osteoporotic Jawbone Marrow Defects Clinical Comparative Study with Corresponding Hounsfield Units and RANTES/CCL5 Expression.

IntroductionThe presently used impulse echo ultrasound examination is not suitable to provide relevant and reliable information about the jawbone, because ultrasound (US) almost completely reflects from the hard cortical jawbone. At the same time, “focal osteoporotic bone marrow defects” (BoneMarrowDefects = BMD) in jawbone are the subject of scientific presentations and discussions.PurposeCan a newly developed trans-alveolar ultrasonic sonography (TAU-n) device locate and ascertain BMD?Patients and MethodsTAU-n consists of a two-part handpiece with an extraoral ultrasound transmitter and an intraoral ultrasound receiver. The TAU-n computer display shows the different jawbone densities with corresponding colour coding. The changes in jawbone density are also displayed numerically. The validation of TAU-n readings: A usual orthopantomogram (2D-OPG) on its own is not suitable for unequivocally determining jawbone density and has to be excluded from this validation. For validation, a 3D-digital volume tomogram@/cone beam computer tomogram (DVT@/CBCT) with the capacity to measure Hounsfield units (HU) and a TAU-n are used to determine the presence of preoperative BMD in 82 patient cases. Postoperatively, histology samples and multiplex analysis of RANTES@/CCL5 (R@/C) expression derived from surgically cleaned BMD areas are evaluated.ResultsIn all 82 bone samples, DVT-HU, TAU-n values and R/C expressions show the presence of BMD with chronic inflammatory character. However, five histology samples showed no evidence of BMD. All four evaluation criteria (DVT-HU, TAU-n, R/C, histology) confirm the presence of BMD in each of the 82 samples.ConclusionThe TAU-n method almost completely matches the diagnostic reliability of the other methods. The newly developed TAU-n scanner is a reliable and radiation-free option to detect BMD.

Broadband Piezoelectric Transducers for Under-Display Ultrasonic Fingerprint Sensing Applications

Smartphones today have attracted a continuous trend of pursuing narrow-bezel and full-screen displays. To allow for a more user-friendly front side fingerprint recognition in full-screen displays, it is crucial to develop an under-display type of fingerprint sensor. Among fingerprint sensing techniques, ultrasonic fingerprint sensing has been proved to be able to provide more distinctive features and give a high resistance to spoof attacks. However, until now no study about under-display ultrasonic fingerprint sensing has been reported. In this article, for the first time, multilayer under-display ultrasonic fingerprint sensor structure using various active materials/structures were theoretically designed and compared. Based on the theoretical analysis results, a lead zirconate titanate (PZT)-5A-based multilayer under-display ultrasonic fingerprint sensor with a resonant frequency of 20 MHz, and a −6-dB fractional bandwidth of more than 70% was fabricated to meet the requirements of resolution and sensitivity for the under-display ultrasonic fingerprint imaging applications. The prototyped sensor was characterized, and the fingerprint recognition capability was tested using a custom-made fingerprint-mimicking phantom. The phantom images were acquired based on the pulse-echo imaging method. With the 1 μJ impulse driving signal, the sensor was manipulated to image a 2.0 mm × 1.0 mm section of fingerprint-mimicking phantom by mechanical scanning, obtaining an electronic image with 500 × 500 DPI. The fingerprint-mimicking phantom imaging results suggest that the 20 MHz broadband PZT-based multilayer structure holds great potential for under-display ultrasonic fingerprint sensor applications.

Discerning calvarian microvascular networks by combined optoacoustic ultrasound microscopy

Bone microvasculature plays a paramount role in bone marrow maintenance, development, and hematopoiesis. Studies of calvarian vascular patterns within living mammalian skull with the available intravital microscopy techniques are limited to small scale observations. We developed an optical-resolution optoacoustic microscopy method combined with ultrasound biomicroscopy in order to reveal and discern the intricate networks of calvarian and cerebral vasculature over large fields of view covering majority of the murine calvaria. The vasculature segmentation method is based on an angle-corrected homogeneous model of the rodent skull, generated using simultaneously acquired three-dimensional pulse-echo ultrasound images. The hybrid microscopy design along with the appropriate skull segmentation method enable high throughput studies of a living bone while facilitating correct anatomical interpretation of the vasculature images acquired with optical resolution optoacoustic microscopy.

Experimental Investigation of Mode I Interlaminar Fracture Toughness in T300/914 Composite

Abstract An aerospace structural material T300/914 has been studied to understand the Mode I interlaminar fracture toughness. For experimental analysis a Double Cantilever Beam (DCB) test is conducted on the laminate to estimate the Mode I interlaminar fracture toughness of the sample. A 48-layer laminate was prepared by hand layup process and an insert included at the mid plane to produce the artificial initial crack required for the test. All the tests are conducted in accordance to the ASTM standards. Pulse-Echo test results and C-Scan images of the laminate were analyzed to find the defects in the laminate. The data from DCB test were analyzed by Modified Beam theory, Compliance calibration method and modified compliance calibration methods to find the interlaminar fracture toughness. A crack length correction method is implemented for data reduction. Numerical analysis of the data derives results in accordance with the experimental analysis.

Coding Mask Design for Single Sensor Ultrasound Imaging

We study the design of a coding mask for pulse-echo ultrasound imaging. We are interested in the scenario of a single receiving transducer with an aberrating layer, or ‘mask,’ in front of the transducer's receive surface, with a separate co-located transmit transducer. The mask encodes spatial measurements into a single output signal, containing more information about a reflector's position than a transducer without a mask. The amount of information in such measurements is dependent on the mask geometry, which we propose to optimize using an image reconstruction mean square error (MSE) criterion. We approximate the physics involved to define a linear measurement model, which we use to find an expression for the image error covariance matrix. By discretizing the mask surface and defining a discrete number of mask thickness levels per point on its surface, we show how finding the best mask can be posed as a variation of a sensor selection problem. We propose a convex relaxation in combination with randomized rounding, as well as a greedy optimization algorithm to solve this problem. We show empirically that both algorithms come close to the global optimum. Our simulations further show that the optimized masks have better a MSE than nearly all randomly shaped masks. We observe that an optimized mask amplifies echoes coming from within the region of interest (ROI), and strongly reduces the correlation between echoes of pixels within the ROI.

Fabrication of Coaxial and Confocal Transducer Based on Sol-Gel Composite Material for Optical Resolution Photoacoustic Microscopy.

We have newly developed coaxial and confocal optical-resolution photoacoustic microscopy based on sol-gel composite materials. This transducer contains a concave-shaped piezoelectric layer with a focus depth of 5 mm and a hole with a diameter of 3 mm at the center to pass a laser beam into a phantom. Therefore, this system can directly detect an excited photoacoustic signal without prisms or acoustic lenses. We demonstrate the capability of the system through pulse-echo and photoacoustic imaging experiments. The center frequency of the fabricated transducer is approximately 7 MHz, and its relative bandwidth is 86%. An ex-vivo experiment is conducted, and photoacoustic signals are clearly obtained. As a result, 2- and 3-dimensional maximum amplitude projection images are reconstructed.

Noninvasive Acoustoelectric Imaging of Resistivity Distribution Based on Lead Field Theory

Acoustoelectric (AE) effect is a basic physical interaction that focused ultrasound that alters the resistivity at the focal spot. Exploiting the AE effect, noninvasive AE imaging (nAEI) of resistivity distribution is investigated based on lead field theory. According to lead field theory, measured AE signal is of good spatial position property, which is sifted by focused ultrasound. Therefore, nAEI can form images directly without resorting to the inverse algorithm. A uniform phantom, 15% NaCl solution, and a nonuniform phantom, composed of 15% NaCl solution and fat, are imaged and discussed. In the experiment, both stimulating and recording electrodes are noninvasive, fixed on the boundary of the imaging chamber. A 1-MHz focused ultrasound transducer scans across the imaging chamber to make spatial sifting. For the uniform phantom with the fixed focal spot, the linear relationship between measured AE signal envelope and injected current signal is tested. In addition, taking resistivity distribution into consideration, the $yz$ -section images of uniform and nonuniform phantoms are presented. Compared to that of the uniform phantom, the resistivity distribution interface of nonuniform phantom can be obviously imaged and distinguished, which is verified by ultrasound pulse-echo imaging. Also, the 3-D slice images confirm that, even taking injected current into consideration, nAEI is potential for resistivity distribution. Finally, the experiment results are discussed and the reason is analyzed from the aspect of enhanced ultrasound pressure and current density induced by resistivity distribution. Both experimental and simulation results validate the feasibility of nAEI of resistivity distribution, and this paper potentially enhances the application of nAEI for cancer detection.

Investigation of the damage effect on electromagnetic performance evaluation of a radar absorbing structure

Stealth technology encompasses various techniques to minimize the detection of acoustic, visual, infrared, and electromagnetic (EM) wave signals. Specifically, to minimize the radar cross section (RCS) of the radar system, radar-absorbing structures (RAS) capable of absorbing EM waves are essential. RAS composed of composites can be damaged, and both their structural and EM performances become important issues in RAS studies. Therefore, in this study, EM wave interactions in damaged specimens were evaluated and visualized using a scanning free-space measurement (SFM) system. First, the change in the EM performance due to damage was analyzed using Al-alloy 6061 and Teflon specimens. When the damage size was less than one-half wavelength (30 mm and 20 mm) in both the X (8.2∼12.4 GHz) and Ku (12.4∼18 GHz) bands, the return loss of Al-alloy 6061 was close to 0 dB and the real part of the permittivity was between 2 and 2.1. On the other hand, when the damage size was more than one-half wavelength, the EM performance in terms of the return and insertion loss and the EM properties of the material (such as the permittivity) were changed in both Al-alloy 6061 and Teflon specimens. Second, a nickel fiber-based RAS with lightning strike-induced damage was also tested by the SFM system, and a behavior similar to that of non-stealth specimens was observed. The RAS was also tested by a pulse-echo ultrasonic propagation imager (PE-UPI) system to investigate the internal damage induced by the lightning strike. Much larger delaminations than the penetration occurred at different plies of the RAS. Eventually, it was found that not only the penetration damage but also the delaminations predominantly affected the EM performance, which caused the overall stealth degradation.

Reconstruction of shear wave speed in layered media using time-harmonic excitation and pulse-echo imaging

Recent advances in high-frequency ultrasound imaging have opened new possibilities for quantitative characterization of skin properties. Noninvasive, accurate measurements of elasticity for multiple layers (e.g., stratum corneum, epidermis, dermis) are potentially beneficial for development and validation of new skin treatments. Here, pulse-echo ultrasound imaging using linear arrays is used to measure time-harmonic tissue displacements induced by a mechanical shaker. It is shown that reconstruction of time-harmonic displacement amplitude and phase in induced elastic waves is feasible for frame rates exceeding the Nyquist frequency and for echoes acquired using multiple transmits per frame. Measured wavefields are inverted using spatial Fourier analysis, numerical solution of the Helmholtz equation by finite difference methods, and direct observation of shear wavelengths. These approaches are validated using a 5 MHz diagnostic imaging array with a clinical scanner (Zonare z.one, L8-1 array) and multlilayered phantoms with varying elastic properties and echogenicity. Further verification of these methods is performed by comparing with finite-element simulations employing a linear elasticity model. Feasibility for measurement of skin layer elastic properties using high-frequency ultrasonic imaging is demonstrated using a 50 MHz linear array and a small-animal scanner (Vevo 2100, MS700 array) for measurements on porcine skin.Recent advances in high-frequency ultrasound imaging have opened new possibilities for quantitative characterization of skin properties. Noninvasive, accurate measurements of elasticity for multiple layers (e.g., stratum corneum, epidermis, dermis) are potentially beneficial for development and validation of new skin treatments. Here, pulse-echo ultrasound imaging using linear arrays is used to measure time-harmonic tissue displacements induced by a mechanical shaker. It is shown that reconstruction of time-harmonic displacement amplitude and phase in induced elastic waves is feasible for frame rates exceeding the Nyquist frequency and for echoes acquired using multiple transmits per frame. Measured wavefields are inverted using spatial Fourier analysis, numerical solution of the Helmholtz equation by finite difference methods, and direct observation of shear wavelengths. These approaches are validated using a 5 MHz diagnostic imaging array with a clinical scanner (Zonare z.one, L8-1 array) and multlilaye...

Development of autonomous target recognition and scanning technology for pulse-echo ultrasonic propagation imager

This article proposes a pulse-echo ultrasonic propagation imaging system that is capable of autonomous target recognition and scanning an area of a customizable shape for the non-destructive evaluation of structural defects. The proposed system employs through-the-thickness bulk waves for ultrasonic inspection, which is achieved by joining two laser beams: one each for the ultrasonic wave generation and sensing. Moreover, the system is capable of autonomously suggesting a suitable inspection area for a specimen placed in front of the scanning head. The scan area delimitation algorithm uses the specimen image and ascertains the specimen border by means of edge and contour detection operations, following which a scan area closely conforming to the specimen boundary is suggested. The system can scan an area of any arbitrary shape, thereby preventing any wasteful operations that may result from fixed shape (rectangular or square) scanning. A Q-switched laser is used for generating the aforementioned ultrasonic waves, while a laser Doppler vibrometer is used for sensing these signals. A dual-axis automated translation stage is applied for raster scanning of the specimen, and a data acquisition card is employed for taking measurements. A camera mounted on the scan head is used for imaging the specimen for the scan area detection. Graphical user interface software controls all the individual blocks of the system, while implementing the required image processing, scan area detection, signal acquisition, signal processing, and result display. The graphical user interface is created in C++ using the Qt framework. Moreover, Qt Widgets for Technical Applications is used for the result display, and the Open Source Computer Vision Library is employed for the implementation of basic image processing algorithms. Multi-threading is used for real-time updating of the scan results while the scanning is ongoing.

Broadband Laser Ultrasonic Excitation and Multi-band Sensing for Hierarchical Automatic Damage Visualization

It is well known that the selection of a frequency for signal generation and data acquisition significantly affects the quality of ultrasonic or laser ultrasonic nondestructive testing (NDT) results, and the analog filter is essential to prevent the aliasing effect. This paper presents a systematic approach using a hierarchical inspection scheme for automatic inspection processes. A frequency band divider (FBD) with a single-input–multiple-output (SIMO) system was newly created to examine quickly various frequency ranges at single scanning using laser-based broadband excitation. The FBD was implemented into a pulse-echo ultrasonic propagation imaging (PE UPI) system capable of fully noncontact laser ultrasonic inspection. Only two scans are required to determine the optimal frequency range for unknown specimens. This tremendously reduces the number of scanning trials for the investigation of complete frequency ranges.

Speckle coherence of piecewise-stationary stochastic targets.

The van Cittert-Zernike (VCZ) theorem describes the propagation of spatial covariance from an incoherent source distribution, such as backscatter from stochastic targets in pulse-echo imaging. These stochastic targets are typically assumed statistically stationary and spatially incoherent with uniform scattering strength. In this work, the VCZ theorem is applied to a piecewise-stationary scattering model. Under this framework, the spatial covariance of the received echo data is demonstrated as the linear superposition of covariances from distinct spatial regions. This theory is analytically derived from fundamental physical principles, and validated through simulation studies demonstrating superposition and scaling. Simulations show that linearity is preserved over various depths and transmit apodizations, and in the presence of noise. These results provide a general framework to decompose spatial covariance into contributions from distinct regions of interest, which may be applied to advanced imaging methods. While the simulation tools used for validation are specific to ultrasound, this analysis is generally applicable to other coherent imaging applications involving stochastic targets. This covariance decomposition provides the physical basis for a recently described imaging method, Multi-covariate Imaging of Sub-resolution Targets.

Damage visualization of a cylindrical CFRP lattice-skin structure based on a pulse-echo ultrasonic propagation imager

Abstract Recently, composite lattice structures are attracting significant attention owing to their high specific stiffness and specific strength and are mainly used in aerospace applications. However, the composite lattice structure also exhibits damage occurrence probability during operation as well as defects in the filament winding manufacturing process. Thus a non-destructive evaluation (NDE) technique for defect and damage evaluation is essential although its complexity is not desirable, especially with respect to in-situ NDE. In this study, we propose a pulse-echo ultrasonic propagation imaging (PE UPI) system for in-situ NDE of cylindrical composite lattice-skin specimen and develop a VTWAM (Variable time window amplitude mapping)-based curvature-compensating algorithm that eliminates the curved surface effect of the PE UPI system. As a result of the actual application to a damaged lattice cylindrical specimen, the damage position, size, and shape are clearly visualized by effectively suppressing the curved surface effect in the inspection region via the VTWAM-based curvature-compensating algorithm. We demonstrate the capability of the linear scan PE UPI to inspect a curved and complex lattice-skin structure with a curved surface compensation algorithm and propose the same as a tool for in-situ health management of composite lattice structures for manufacturing to in-service stages.

Nondestructive and electromagnetic evaluations of stealth structures damaged by lightning strike

Stealth technology is very important for the survival of military aircraft. A stealth aircraft structure has both electromagnetic and mechanical functions. Lightning can cause failure on both the points. In this study, we claim that the stealth structure should be evaluated nondestructively and electromagnetically, and we propose a method for full-field evaluations of both the functions. First, a radar absorbing structure was designed and fabricated with stealth capability in the X-band. The radar absorbing structure consisted of a carbon nanotube layer (glass/epoxy dispersed with multiwalled carbon nanotubes), a spacer layer (glass/epoxy) and a perfect electrical conductor layer. A lightning test was performed using an impulse current generator according to standard regulations. Then, nondestructive damage and electromagnetic performance evaluations were performed using a pulse-echo laser ultrasonic propagation imager and a scanning free-space measurement system, respectively. The results showed that neither structural damage nor changes in the electromagnetic properties were observed during the two evaluations. In general, the composites were severely damaged by lightning. However, it turned out that the radar absorbing structure with the carbon nanotube layer could prevent serious damage to stealth function as well as material damage owing to the high conductivity of the carbon nanotubes dispersed in its surface layer.

Improving DOT reconstruction with a Born iterative method and US-guided sparse regularization.

Ultrasound (US)-guided diffuse optical tomography (DOT) is a promising low-cost imaging technique for diagnosis and assessment of breast cancer. US-guided DOT is best implemented in reflection geometry, which can be co-registered with US pulse-echo imaging and also minimizes the tissue depth for adequate light penetration. However, due to intense light scattering, the DOT reconstruction problem is ill-posed. In this communication, we describe a new non-linear Born iterative reconstruction method with US-guided depth-dependent sparse regularization for improving DOT reconstruction by incorporating a priori lesion depth and shape information from the co-registered US image. Our method iteratively solves the inverse problem by updating the photon-density wave using the finite difference method, computing the weight matrix based on Born approximation, and reconstructing the absorption map using the fast iterative shrinkage-thresholding optimization algorithm (FISTA). We validate our method using both phantom and patient data and compare the results with those using the first order linear Born method. Phantom experiments demonstrate that the non-linear Born method provides more accurate target absorption reconstruction and better resolution than the linear Born method. Clinical studies on 20 patients show that non-linear Born reconstructs more realistic tumor shapes than linear Born, and improves the malignant-to-benign lesion contrast ratio from to , which is a improvement. For lesions approximately more than cm in diameter, the average malignant-to-benign lesion contrast ratio is increased from to , which is a improvement.

All-Optical Rotational Ultrasound Imaging

Miniaturised high-resolution imaging devices are valuable for guiding minimally invasive procedures such as vascular stent placements. Here, we present all-optical rotational B-mode pulse-echo ultrasound imaging. With this device, ultrasound transmission and reception are performed with light. The all-optical transducer in the probe comprised an optical fibre that delivered pulsed excitation light to an optical head at the distal end with a multi-walled carbon nanotube and polydimethylsiloxane composite coating. This coating was photoacoustically excited to generate a highly directional ultrasound beam perpendicular to the optical fibre axis. A concave Fabry-Pérot cavity at the distal end of an optical fibre, which was interrogated with a tuneable continuous-wave laser, served as an omnidirectional ultrasound receiver. The transmitted ultrasound had a −6 dB bandwidth of 31.3 MHz and a peak-to-peak pressure of 1.87 MPa, as measured at 1.5 mm from the probe. The receiver had a noise equivalent pressure <100 Pa over a 20 MHz bandwidth. With a maximum outer probe diameter of 1.25 mm, the probe provided imaging with an axial resolution better than 50 µm, and a real-time imaging rate of 5 frames per second. To investigate the capabilities of the probe, intraluminal imaging was performed in healthy swine carotid arteries. The results demonstrate that the all-optical probe is viable for clinical rotational ultrasound imaging.

Ex vivo thermal ablation monitoring using three-dimensional ultrasound echo decorrelation imaging

Echo decorrelation imaging is a method for quantitatively mapping transient heat-induced changes in pulse-echo ultrasound images. For clinical thermal ablation of liver cancer using radiofrequency or microwave ablation (RFA or MWA), real-time three-dimensional (3D) echo decorrelation imaging is necessary because the entire tumor, with typical diameter 2–5 cm, is ablated at once. We present a method for constructing 3D echo decorrelation maps during radiofrequency ablation (RFA) in ex vivo bovine liver using beamformed in-phase and quadrature (IQ) echo acquired from a Siemens Acuson SC2000 scanner and 4Z1c matrix array. To directly compare echo decorrelation images to the desired outcome of tissue ablation, 3D echo decorrelation images are compared to volumetric reconstructions of the thermal ablation zone, obtained from optical scans of regularly spaced tissue sections. Capability of echo decorrelation as a predictor of local ablation is assessed using receiver operator characteristic curve analysis. Similar to previous studies of two-dimensional echo decorrelation imaging, good correspondence is seen between 3D echo decorrelation images and ablated tissue histology.