Plane wave imaging challenge

The plane wave imaging challenge (PICMUS) has been introduced for the first time to IUS in order to encourage participants to compete and share their knowledge in medical ultrasound plane wave imaging. To participate in this challenge, we have chosen the contrast enhanced delay and sum (CEDAS) post signal processing method. This technique have been used to improve B-mode image contrast to noise ratio (CNR) without effecting the image spatial resolution. With CEDAS the energy of every envelope signal is calculated, mapped, and clustered in order to identify the cyst and clutter location. CEDAS significantly reduces the clutter inside the cyst by attenuating it from envelope signals before the new B-Mode image is formed. This paper describes in more details the techniques and parameters we have been using for the challenge. Results obtained for CEDAS shows that it outperforms conventional DAS by 18.33% in experiment and 79.24% in simulation for CNR

Clutter noise reduction in B-Mode image through mapping and clustering signal energy for better cyst classification

Improving the ultrasound image contrast ratio (CR) and contrast to noise ratio (CNR) has many clinical advantages. Breast cancer detection is one example. Anechoic cysts which fill with clutter noise can be easily misinterpreted and classified as malignant lesions instead of benign. Beamforming techniques contribute to off-axis side lobes and clutter. These two side effects inherent in beamforming are undesirable since they will degrade the image quality by lowering the image CR and CNR. To overcome this issue a new post-processing technique known as contrast enhanced delay and sum (CEDAS) is proposed. Here the energy of every envelope signals are calculated, mapped, and clustered in order to identify the cyst and clutter location. CEDAS reduce clutter inside the cyst by attenuating it from envelope signals before the new B-Mode image is formed. With CEDAS, the image CR and CNR improved by average 12 dB and 1.1 dB respectively for cysts size 2 mm to 6 mm and imaging depth from 40 mm to 80 mm

A Novel Sample Based Quadrature Phase Shift Keying Demodulator

This paper presents a new practical QPSK receiver that uses digitized samples of incoming QPSK analog signal to determine the phase of the QPSK symbol. The proposed technique is more robust to phase noise and consumes up to 89.6% less power for signal detection in demodulation operation. On the contrary, the conventional QPSK demodulation process where it uses coherent detection technique requires the exact incoming signal frequency; thus, any variation in the frequency of the local oscillator or incoming signal will cause phase noise. A software simulation of the proposed design was successfully carried out using MATLAB Simulink software platform. In the conventional system, at least 10 dB signal to noise ratio (SNR) is required to achieve the bit error rate (BER) of 10−6, whereas, in the proposed technique, the same BER value can be achieved with only 5 dB SNR. Since some of the power consuming elements such as voltage control oscillator (VCO), mixer, and low pass filter (LPF) are no longer needed, the proposed QPSK demodulator will consume almost 68.8% to 99.6% less operational power compared to conventional QPSK demodulator

Comparison of Spatial and Temporal Averaging on Ultrafast Imaging in Presence of Quantization Errors

In compound plane wave imaging (CPWI), multiple plane waves are used to insonify the imaging region with different steering angles. The compounding operation is effectively a spatial averaging filter that reduces the speckles of the image and increases the image contrast and its lateral resolution. Although spatial averaging often improves CPWI image quality, quantization errors which dependent on sampling frequency and element spacing (pitch), introduced during beam steering reduce this improvement. In this study, the effect of spatial and temporal averaging on speckle noise reduction, contrast resolution and spatial resolution in ultrafast ultrasound imaging is evaluated. The overall results from the simulations shows that the maximum effect of quantization errors on speckle noise is 0.18 dB, on the image contrast is 0.27 dB, on axial resolution is 2.38% and finally on lateral resolution is 1.44%. On the other hand, plane wave imaging (PWI) employing temporal averaging technique which is not bound with quantization errors relatively produces high contrast to noise ratio (CNR) and speckle signal to noise ratio (SSNR) at 40 MHz for both centre frequency compared to CPWI

Enhancement of contrast and resolution of B-mode plane wave imaging (PWI) with non-linear filtered delay multiply and sum (FDMAS) beamforming

FDMAS has been successfully used in microwave imaging for breast cancer detection. FDMAS gained its popularity due to its capability to produce results faster than any other adaptive beamforming technique such as minimum variance (MV) which requires higher computational complexity. The average computational time for single point spread function (PSF) at 40 mm depth for FDMAS is 87 times faster than MV. The new beamforming technique has been tested on PSF and cyst phantoms experimentally with the ultrasound array research platform version 2 (UARP II) using a 3-8 MHz 128 element clinical transducer. FDMAS is able to improve both imaging contrast and spatial resolution as compared to DAS. The wire phantom main lobes lateral resolution improved in FDMAS by 40.4% with square pulse excitation signal when compared to DAS. Meanwhile the contrast ratio (CR) obtained for an anechoic cyst located at 15 mm depth for PWI with DAS and FDMAS are -6.2 dB and -14.9 dB respectively. The ability to reduce noise from off axis with auto-correlation operation in FDMAS pave the way to display the B-mode image with high dynamic range. However, the contrast to noise ratio (CNR) measured at same cyst location for FDMAS give less reading compared to DAS. Nevertheless, this drawback can be compensated by applying compound plane wave imaging (CPWI) technique on FDMAS. In overall the new FDMAS beamforming technique outperforms DAS in laboratory experiments by narrowing its main lobes and increases the image contrast without sacrificing its frame rates

Spatial Resolution and Contrast Enhancement in Photoacoustic Imaging with Filter Delay Multiply and Sum Beamforming Technique

Photoacoustic imaging is used to differentiate between tissue types based on light absorption. Different structures, such as vascular density of capillaries in human tissue, can be analysed and provide diagnostic information to detect early stage breast cancer. Delay and sum (DAS) beamforming is the traditional method to reconstruct photoacoustic images. However, for structures located deep in the tissue (>10 mm), signal to noise (SNR) of the photoacoustic signal drops significantly. This study proposes using filter delay multiply and sum (FDMAS) beamforming technique to increase the SNR and enhance the image quality. Experimental results showed that FDMAS beamformer improved the SNR by 6.9 dB and the lateral resolution by 48% compared to the DAS beamformer. Moreover, the effect of aperture size on the proposed method is presented as the sub-group FDMAS, which further increased the improvement in image quality

New Denoising Unsharp Masking Method for Improved Intima Media Thickness Measurements with Active Contour Segmentation

© 2018 IEEE. The semi-automated balloon snake active contour (BSAC) based segmentations play a vital role in determining the intima-media thickness (IMT) for accessing the risk related to cardio vascular diseases (CVD). However, the speckle and clutter noise in the ultrasound B-mode images are known to interfere with the contour formation during segmentation. Both noise sources act as false external energy in BSAC and thus influence the resulting boundary definition. A large number of iterations are required for the BSAC to accurately detect the boundary and in the presence of high noise the segmentation algorithm can result in false detections. Thus in this work we have applied the new denoising unsharp masking (UM) method on human common carotid artery in order to reduce clutter noise in the B-mode image before the segmentation process takes place for faster and accurate IMT measurement. The resuts show the number of iterations needed for BSAC to settle on the final intima-media border is less with UM-DAS (100 iterations) compared to that without the denoising technique, DAS (200 iterations). Thus the proposed UM techniques is able to provide better results with less time in measuring the IMT compared to that using DAS

A New Nonlinear Compounding Technique for Ultrasound B-mode Medical Imaging

Compounding techniques have been used in ultra-fast ultrasound imaging to improve image quality by reducing clutter noise, smoothing speckle variance and enhancing its spatial resolution at the cost of reducing frame rate. However, the reduction of clutter noise and side lobes inside the anechoic regions is minimal when combining conventional spatial compounding and delay-and-sum (DAS) beamforming. Despite the availability of advanced beamforming algorithms such as filtered-delay-multiply-and-sum (FDMAS), its prevalence is hindered by relatively high computational cost. In this study, a new nonlinear compounding technique known as filtered multiply and sum (FMAS) was proposed to improve the B-mode image quality without increasing the overall computational complexity. With three compunding angles, the lateral resolution for DAS-FMAS was improved by 36% and 19% compared to DAS and FDMAS. The proposed DAS-FMAS technique also provided improvements of 14.1 dB and 7.29 dB in contrast ratio than DAS and FDMAS

A Novel Two-Dimensional Displacement Estimation for Angled Shear Wave Elastography

This study aimed to estimate angled tissue motion for shear wave compounding applications. Shear wave elastography produces the quantitative elasticity biomarker for assessing the health status of tissues. In sheer wave compounding, steered shear waves are generated with different angles, and individual angle elasticity maps are averaged to improve tissue stiffness reconstruction. When shear waves are steered and the tissue motion is generated in multiple directions, traditional one dimensional (1D) displacement estimation fails in capturing actual shear wave amplitude and direction. This study investigated the use of two dimensional (2D) kernel to track angular shear wave motion, which resulted in the underestimation of displacement values. Consequently, a new method named as 2D proposed (2D-P) was used to calculate both axial and lateral motion components separately using 1D axial and lateral kernels. Final results indicated that, the proposed scheme produced an average improvement of 2.01 μm and 4.4 μm compared with the 1D axial cross correlation and 2D cross correlation based methods, respectively

Optimizing the lateral beamforming step for filtered-delay multiply and sum beamforming to improve active contour segmentation using ultrafast ultrasound imaging

As an alternative to delay-and-sum beamforming, a novel beamforming technique called filtered-delay multiply and sum (FDMAS) was introduced recently to improve ultrasound B-mode image quality. Although a considerable amount of work has been performed to evaluate FDMAS performance, no study has yet focused on the beamforming step size, , in the lateral direction. Accordingly, the performance of FDMAS was evaluated in this study by fine-tuning to find its optimal value and improve boundary definition when balloon snake active contour (BSAC) segmentation was applied to a B-mode image in ultrafast imaging. To demonstrate the effect of altering in the lateral direction on FDMAS, measurements were performed on point targets, a tissue-mimicking phantom and in vivo carotid artery, by using the ultrasound array research platform II equipped with one 128-element linear array transducer, which was excited by 2-cycle sinusoidal signals. With 9-angle compounding, results showed that the lateral resolution (LR) of the point target was improved by 67.9% and 81.2%, when measured at −6 dB and −20 dB respectively, when was reduced from to . Meanwhile the image contrast ratio (CR) measured on the CIRS phantom was improved by 10.38 dB at the same reduction and the same number of compounding angles. The enhanced FDMAS results with lower side lobes and less clutter noise in the anechoic regions provides a means to improve boundary definition on a B-mode image when BSAC segmentation is applied