Globally optimized Fourier finite-difference method for ultrasound breast imaging (original) (raw)
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Globally optimized Fourier finite-difference method for ultrasound breast imaging
Medical Imaging 2008: Ultrasonic Imaging and Signal Processing, 2008
Ultrasound reflection imaging is a promising imaging modality for detecting small, early-stage breast cancers. Properly accounting for ultrasound scattering from heterogeneities within the breast is essential for high-resolution and high-quality ultrasound breast imaging. We develop a globally optimized Fourier finite-difference method for ultrasound reflectivity image reconstruction. It utilizes an optimized solution of acoustic-wave equation and a heterogeneous sound-speed distribution of the breast obtained from tomography to reconstruct ultrasound reflectivity images. The method contains a finite-difference term in addition to the split-step Fourier implementation, and minimizes ultrasound phase errors during wavefield inward continuation while maintaining the advantage of high computational efficiency. The accuracy analysis indicates that the optimized method is much more accurate than the split-step Fourier method. The computational efficiency of the optimized method is one to two orders of magnitude faster than time-reversal imaging using a finite-difference time-domain wave-equation scheme. Our new optimized method can accurately handle ultrasound scattering from breast heterogeneities during reflectivity image reconstruction. Our numerical imaging examples demonstrate that the optimized method has the potential to produce high-quality and high-resolution ultrasound reflectivity images in combination with a reliable ultrasound sound-speed tomography method.
Ultrasound pulse-echo imaging using the split-step Fourier propagator
Proceedings of SPIE, 2007
Ultrasonic reflection imaging has the potential to produce higher image resolution than transmission tomography, but imaging resolution and quality still need to be further improved for early cancer detection and diagnosis. We present an ultrasound reflection image reconstruction method using the split-step Fourier propagator. It is based on recursive inward continuation of ultrasonic wavefields in the frequency-space and frequency-wavenumber domains. The inward continuation within each extrapolation interval consists of two steps. In the first step, a phase-shift term is applied to the data in the frequency-wavenumber domain for propagation in a reference medium. The second step consists of applying another phase-shift term to data in the frequency-space domain to approximately compensate for ultrasonic scattering effects of heterogeneities within the breast. We use synthetic ultrasound pulse-echo data recorded around a ring for heterogeneous, computer-generated, numerical breast phantoms to study the imaging capability of the method. The phantoms are derived from an experimental breast phantom and a sound-speed tomography image of an in-vivo ultrasound breast data collected using a ring array. The heterogeneous sound-speed models used for pulse-echo imaging are obtained using a computationally efficient, first-arrival-time (time-of-flight) transmission tomography method. Our studies demonstrate that reflection image reconstruction using the split-step Fourier propagator with heterogeneous sound-speed models significantly improves image quality and resolution. We also numerically verify the spatial sampling criterion of wavefields for a ring transducer array.
SPIE Proceedings, 2014
Ultrasound transmission tomography usually generates low-resolution breast images. We improve sound-speed reconstructions using ultrasound waveform tomography with both transmission and reflection data. We validate the improvement using computer-generated synthetic-aperture ultrasound transmission and reflection data for numerical breast phantoms. Our tomography results demonstrate that using both transmission and reflection data in ultrasound waveform tomography greatly enhances the resolution and accuracy of tomographic reconstructions compared to ultrasound waveform tomography using either transmission data or reflection data alone. To verify the capability of our novel ultrasound waveform tomography, we design and manufacture a new synthetic-aperture breast ultrasound tomography system with two parallel transducer arrays for clinical studies. The distance of the two transducer arrays is adjustable for accommodating different sizes of the breast. The parallel transducer arrays also allow us to easily scan the axillary region to evaluate the status of axillary lymph nodes and detect breast cancer in the axillary region. However, synthetic-aperture ultrasound reflection data acquired by firing each transducer element sequentially are usually much weaker than transmission data, and have much lower signal-to-noise ratios than the latter. We develop a numerical virtual-point-source method to enhance ultrasound reflection data using synthetic-aperture ultrasound data acquired by firing each transducer element sequentially. Syntheticaperture ultrasound reflection data for a breast phantom obtained using our numerical virtual-point-source method reveals many coherent ultrasound reflection waveforms that are weak or invisible in the original synthetic-aperture ultrasound data. Ultrasound waveform tomography using both transmission and reflection data together with numerical virtual-point-source method has great potential to produce high-resolution tomographic reconstructions in clinical studies of breast ultrasound tomography.
The Journal of the Acoustical Society of America, 2017
Ultrasound computed tomography (USCT) is a non-invasive imaging technique that provides information about the acoustic properties of soft tissues in the body, such as the speed of sound (SS) and acoustic attenuation (AA). Knowledge of these properties can improve the discrimination between benign and malignant masses, especially in breast cancer studies. Full wave inversion (FWI) methods for image reconstruction in USCT provide the best image quality compared to more approximate methods. Using FWI, the SS is usually recovered in the time domain, and the AA is usually recovered in the frequency domain. Nevertheless, as both properties can be obtained from the same data, it is desirable to have a common framework to reconstruct both distributions. In this work, an algorithm is proposed to reconstruct both the SS and AA distributions using a time domain FWI methodology based on the fractional Laplacian wave equation, an adjoint field formulation, and a gradient-descent method. The optimization code employs a Compute Unified Device Architecture version of the software k-Wave, which provides high computational efficiency. The performance of the method was evaluated using simulated noisy data from numerical breast phantoms. Errors were less than 0.5% in the recovered SS and 10% in the AA. V
3D Wave-Equation-Based Finite-Frequency Tomography for Ultrasound Computed Tomography
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Ultrasound Computed Tomography (USCT) has great potential for 3D quantitative imaging of acoustic breast tissue properties. Typical devices include high-frequency transducers, which makes tomography techniques based on numerical wave propagation simulations computationally challenging, especially in 3D. Therefore, despite the finite-frequency nature of ultrasonic waves, ray-theoretical approaches to transmission tomography are still widely used.
High resolution 3D ultrasonic breast imaging by time-domain full waveform inversion
Inverse Problems, 2021
Ultrasound tomography (UST) scanners allow quantitative images of the human breast’s acoustic properties to be derived with potential applications in screening, diagnosis and therapy planning. Time domain full waveform inversion (TD-FWI) is a promising UST image formation technique that fits the parameter fields of a wave physics model by gradient-based optimization. For high resolution 3D UST, it holds three key challenges: firstly, its central building block, the computation of the gradient for a single US measurement, has a restrictively large memory footprint. Secondly, this building block needs to be computed for each of the 103–104 measurements, resulting in a massive parallel computation usually performed on large computational clusters for days. Lastly, the structure of the underlying optimization problem may result in slow progression of the solver and convergence to a local minimum. In this work, we design and evaluate a comprehensive computational strategy to overcome the...
Refraction corrected transmission ultrasound computed tomography for application in breast imaging
Medical Physics, 2010
We present an iterative framework for CT reconstruction from transmission ultrasound data which accurately and efficiently models the strong refraction effects that occur in our target application: Imaging the female breast. Methods: Our refractive ray tracing framework has its foundation in the fast marching method ͑FNMM͒ and it allows an accurate as well as efficient modeling of curved rays. We also describe a novel regularization scheme that yields further significant reconstruction quality improvements. A final contribution is the development of a realistic anthropomorphic digital breast phantom based on the NIH Visible Female data set. Results: Our system is able to resolve very fine details even in the presence of significant noise, and it reconstructs both sound speed and attenuation data. Excellent correspondence with a traditional, but significantly more computationally expensive wave equation solver is achieved. Conclusions: Apart from the accurate modeling of curved rays, decisive factors have also been our regularization scheme and the high-quality interpolation filter we have used. An added benefit of our framework is that it accelerates well on GPUs where we have shown that clinical 3D reconstruction speeds on the order of minutes are possible.
Modeling acoustic wave field propagation in 3D breast models
2011
Attenuation or loss forms an important phenomenon in medical ultrasound. At ultrasonic frequencies, attenuation is mainly due to absorption. Experimental data reveal that attenuation acts according to a frequency power law. For a given penetration depth, this effect limits the frequency, and hence the attainable resolution, that is utilized in diagnostic ultrasound applications. Attenuation is also crucial for therapeutic applications where high intensity focused ultrasound fields are used for ablation and hyperthermia treatment. Modeling attenuative pressure fields in inhomogeneous media is therefore of great importance for the development of new ultrasound modalities and the optimization of treatment protocols. In this paper a compliance memory function is utilized to model attenuation. This function consists of two parts; a spatially independent and a spatially dependent part. The former accounts for the lossy background medium, the latter for variations in the attenuation parameters with respect to the background medium. The first part is accounted for by deriving the Green's function of the lossy background medium, whereas the second part leads to the formulation of attenuation contrast sources. The resulting integral equation for the acoustic wave field is solved with an iterative Neumann scheme. Each step involves the convolution of the attenuation contrast sources with the 'lossy' Green's function. Finally, nonlinear contrast sources are included to extend the method to nonlinear acoustics, resulting in a new version of the Iterative Nonlinear Contrast Source (INCS) method. The presented approach shows excellent agreement with results obtained with the 'contrast only' INCS method, which includes losses only via an attenuation contrast source. This agreement occurs both when nonlinear propagation is or is not taken into account. Moreover, the presented method shows a faster convergence ac compared to the 'contrast only' method, and it automatically prevents for scattering artifacts caused by truncation of the numerical domain.
Full-wave attenuation reconstruction in the time domain for ultrasound computed tomography
2016 IEEE 13th International Symposium on Biomedical Imaging (ISBI), 2016
Acoustical attenuation (AA) maps in Ultrasound Computed Tomography (USCT) provide enhanced contrast between tissues compared to the speed of sound (SS), which is the most common property of tissue studied with this technique. Currently, the full wave inversion (FWI) methods used for their reconstruction are very different: the AA is mainly estimated using frequency domain algorithms, while the SS is more often recovered in the time domain. In this work we present a novel strategy to recover the attenuation maps through a straightforward and simplified procedure in the time domain. A gradient descent method was employed to optimize iteratively the attenuation distribution. The expression for the functional gradient of the norm of the global deviation between experimental and simulated data was obtained using an adjoint method. The optimization code, implemented in C++, employs a CUDA version of the k-Wave software to perform forward and backward wave propagation. Noisy simulated data was used to test the performance of the proposed method. The simplicity of the formulation of this new method may facilitate the reconstruction of AA and SS maps under a common framework in USCT.
2008
Transmission Ultrasound Computed Tomography (CT) is strongly affected by the acoustic refraction properties of the imaged tissue, and proper modeling and correction of these effects is crucial to achieving high-quality image reconstructions. A method that can account for these refractive effects solves the governing Eikonal equation within an iterative reconstruction framework, using a wave-front tracking approach. Excellent results can be obtained, but at considerable computational expense. Here, we report on the acceleration of three Eikonal solvers (Fast Marching Method (FMM), Fast Sweeping Method (FSM), Fast Iterative Method (FIM)) on three computational platforms (commodity graphics hardware (GPUs), multi-core and cluster CPUs), within this refractive Transmission Ultrasound CT framework. Our efforts provide insight into the capabilities of the various architectures for acoustic wave-front tracking, and they also yield a framework that meets the interactive demands of clinical practice, without a loss in reconstruction quality.