Synthetic aperture (SA) technique is a novel approach to present day commercial systems and has previously not been used in medical ultrasound imaging. The basic idea of SA is to combine information acquired simultaneously from all directions over a number of emissions and to reconstruct the full image from these data.

The paper presents the multi-element STA (MSTA) method for medical ultrasound imaging. The main difference with the STA approach is the use of a few elements in the transmit mode in contrast to a single element aperture. This allows increasing the system frame rate, decreasing the number of emissions, and provides the best compromise between the penetration depth and lateral resolution. Besides, a modified MSTA is proposed with a corresponding RF signal correction in the receive mode, which accounts for the element directivity property.

In the experiments a 32-element linear transducer array with 0.48 mm inter-element spacing and a burst pulse of 100 ns duration were used. Two elements wide transmission aperture was used to generate an ultrasound wave covering the full image region. The comparison of 2D ultrasound images of a tissue mimicking phantom obtained using the STA and MSTA methods is presented to demonstrate the benefits of the second one.

The paper presents the optimization problem for the multi-element synthetic transmit aperture method (MSTA) in ultrasound imaging applications. The optimal choice of the transmit aperture size is made as a trade-off between the lateral resolution, penetration depth and the frame rate. Results of the analysis obtained by a developed optimization algorithm are presented. The maximum penetration depth and lateral resolution at given depths are chosen as optimization criteria. The results of numerical experiments carried out in MATLAB® using synthetic aperture data of point reflectors obtained by the FIELD II simulation program are presented. The visualization of experimental synthetic aperture data of a tissue mimicking phantom and in vitro measurements of the beef liver performed using the SonixTOUCH Research system are also shown.

B a c k g r o u n d: Echocardiography is the first exam to establish the myocardial function in patients with takotsubo syndrome (TTS). However, ECG-Gated Myocardial Single-Photon Emission Tomography (G-SPECT) also allows to calculate left ventricular ejection fraction (LVEF) and can be useful in early stadium of TTS.

A i m: To compare LVEF obtained from 99mTc-MIBI G-SPECT and echocardiography in patients with TTS.

M a t e r i a l a n d M e t h o d s: Study population: 20 patients in medium age 77 (62–89) with TTS were included. In all patients 99mTc-MIBI G-SPECT and echocardiography was performed on the same day.

R e s u l t s: LVEF measured by G-SPECT and echocardiography ranged from 34 to 83% and 38 to 69%, respectively. The LVEF values for ECHO were significantly lower than for SPECT. The correlation between the LVEF was r = 0.76. The calculated correlation coefficient (r) for linear regression analysis was 0.64. The following equation shows the approximate interdependence of both LVEF calculations: LVEF GSPECT = 10.35 + 0.93 * LVEF Echo.

C o n c l u s i o n s: G-SPECT tends to overerestimate LVEF compared to echocardiography so these imaging techniques should not be used interchangeably. Calculated equation should be used for comparison of LVEF.

The attenuating properties of biological tissue are of great importance in ultrasonic medical imaging. Investigations performed in vitro and in vivo showed the correlation between pathological changes in the tissue and variation of the attenuation coefficient. In order to estimate the attenuation we have used the downshift of mean frequency (fm) of the interrogating ultrasonic pulse propagating in the medium. To determine the fm along the propagation path we have applied the fm estimator (I/Q algorithm adopted from the Doppler mean frequency estimation technique). The mean-frequency shift trend was calculated using Single Spectrum Analysis. Next, the trends were converted into attenuation coefficient distributions and finally the parametric images were computed. The RF data were collected in simulations and experiments applying the synthetic aperture (SA) transmit-receiving scheme. In measurements the ultrasonic scanner enabling a full control of the transmission and reception was used. The resolution and accuracy of the method was verified using tissue mimicking phantom with uniform echogenicity but varying attenuation coefficient.

Ultrasound is used for breast cancer detection as a technique complementary to mammography, the standard screening method. Current practice is based on reflectivity images obtained with conventional instruments by an operator who positions the ultrasonic transducer by hand over the patient’s body. It is a non-ionizing radiation, pain-free and not expensive technique that provides a higher contrast than mammography to discriminate among fluid-filled cysts and solid masses, especially for dense breast tissue. However, results are quite dependent on the operator’s skills, images are difficult to reproduce, and state-of-the-art instruments have a limited resolution and contrast to show micro-calcifications and to discriminate between lesions and the surrounding tissue. In spite of their advantages, these factors have precluded the use of ultrasound for screening.

This work approaches the ultrasound-based early detection of breast cancer with a different concept. A ring array with many elements to cover 360◦ around a hanging breast allows obtaining repeatable and operator-independent coronal slice images. Such an arrangement is well suited for multi-modal imaging that includes reflectivity, compounded, tomography, and phase coherence images for increased specificity in breast cancer detection. Preliminary work carried out with a mechanical emulation of the ring array and a standard breast phantom shows a high resolution and contrast, with an artifact-free capability provided by phase coherence processing.

The pathological states of biological tissue are often resulted in attenuation changes. Thus, information about attenuating properties of tissue is valuable for the physician and could be useful in ultrasonic diagnosis. We are currently developing a technique for parametric imaging of attenuation and we intend to apply it for in vivo characterization of tissue. The attenuation estimation method based on the echoes mean frequency changes due to tissue attenuation dispersion, is presented. The Doppler IQ technique was adopted to estimate the mean frequency directly from the raw RF data. The Singular Spectrum Analysis technique was used for the extraction of mean frequency trends. These trends were converted into attenuation distribution and finally the parametric images were computed. In order to reduce variation of attenuation estimates the spatial compounding method was applied. Operation and accuracy of attenuation extracting procedure was verified by calculating the attenuation coefficient distribution using the data from the tissue phantom (DFS, Denmark) with uniform echogenicity while attenuation coefficient underwent variation.

Super-resolution image reconstruction utilizes two algorithms, where one is for single-frame image reconstruction, and the other is for multi-frame image reconstruction. Singleframe image reconstruction generally takes the first degradation and is followed by reconstruction, which essentially creates a problem of insufficient characterization. Multi-frame images provide additional information for image reconstruction relative to single frame images due to the slight differences between sequential frames. However, the existing super-resolution algorithm for multi-frame images do not take advantage of this key factor, either because of loose structure and complexity, or because the individual frames are restored poorly. This paper proposes a new SR reconstruction algorithm for images using Multi-grained Cascade Forest. Multi-frame image reconstruction is processed sequentially. Firstly, the image registration algorithm uses a convolutional neural network to register low-resolution image sequences, and then the images are reconstructed after registration by the Multi-grained Cascade Forest reconstruction algorithm. Finally, the reconstructed images are fused. The optimal algorithm is selected for each step to get the most out of the details and tightly connect the internal logic of each sequential step. This novel approach proposed in this paper, in which the depth of the cascade forest is procedurally generated for recovered images, rather than being a constant. After training each layer, the recovered image is automatically evaluated, and new layers are constructed for training until an optimal restored image is obtained. Experiments show that this method improves the quality of image reconstruction while preserving the details of the image.

Image segmentation is a typical operation in many image analysis and computer vision applications. However, hyperspectral image segmentation is a field which have not been fully investigated. In this study an analogue- digital image segmentation technique is presented. The system uses an acousto-optic tuneable filter, and a CCD camera to capture hyperspectral images that are stored in a digital grey scale format. The data set was built considering several objects with remarkable differences in the reflectance and brightness components. In addition, the work presents a semi-supervised segmentation technique to deal with the complex problem of hyperspectral image segmentation, with its corresponding quantitative and qualitative evaluation. Particularly, the developed acousto-optic system is capable to acquire 120 frames through the whole visible light spectrum. Moreover, the analysis of the spectral images of a given object enables its segmentation using a simple subtraction operation. Experimental results showed that it is possible to segment any region of interest with a good performance rate by using the proposed analogue-digital segmentation technique.

Ultrasonic methods of human body internal structures imaging are being continuously enhanced. New algorithms are created to improve certain output parameters. A synthetic aperture method (SA) is an example which allows to display images at higher frame-rate than in case of conventional beam-forming method.

Higher computational complexity is a limitation of SA method and it can prevent from obtaining a desired reconstruction time. This problem can be solved by neglecting a part of data. Obviously it implies a decrease of imaging quality, however a proper data reduction technique would minimize the image degradation.

A proposed way of data reduction can be used with synthetic transmit aperture method (STA) and it bases on an assumption that a signal obtained from any pair of transducers is the same, no matter which transducer transmits and which receives. According to this postulate, nearly a half of the data can be ignored without image quality decrease.

The presented results of simulations and measurements with use of wire and tissue phantom prove that the proposed data reduction technique reduces the amount of data to be processed by half, while maintaining resolution and allowing only a small decrease of SNR and contrast of resulting images.

Commercially available cardiac scanners use 64–128 elements phased-array (PA) probes and classical delay-and-sum beamforming to reconstruct a sector B-mode image. For portable and hand-held scanners, which are the fastest growing market, channel count reduction can greatly decrease the total power and cost of devices. The introduction of ultra-fast imaging methods based on plane waves and diverging waves provides new insight into heart’s moving structures and enables the implementation of new myocardial assessment and advanced flow estimation methods, thanks to much higher frame rates. The goal of this study was to show the feasibility of reducing the channel count in the diverging wave synthetic aperture image reconstruction method for phased-arrays. The application of ultra-fast 32-channel subaperture imaging combined with spatial compounding allowed the frame rate of approximately 400 fps for 120 mm visualization to be achieved with image quality obtained on par with the classical 64-channel beamformer. Specifically, it was shown that the proposed method resulted in image quality metrics (lateral resolution, contrast and contrast-to-noise ratio), for a visualization depth not exceeding 50 mm, that were comparable with the classical PA beamforming. For larger visualization depths (80–100 mm) a slight degradation of the above parameters was observed. In conclusion, diverging wave phased-array imaging with reduced number of channels is a promising technology for low-cost, energy efficient hand-held cardiac scanners.

Therapeutic and surgical applications of focused ultrasound require monitoring of local temperature rises induced inside tissues. From an economic and practical point of view ultrasonic imaging techniques seem to be the most suitable for the temperature control. This paper presents an implementation of the ultrasonic echoes displacement estimation technique for monitoring of local temperature rise in tissue during its heating by focused ultrasound The results of the estimation were compared to the temperature measured with thermocouple. The obtained results enable to evaluate the temperature fields induced in tissues by pulsed focused ultrasonic beams using non-invasive imaging ultrasound technique

This paper proposes a new approach to the processing and analysis of medical images. We introduce the term and methodology of medical data understanding, as a new step in the way of starting from image processing, and followed by analysis and classification (recognition). The general view of the situation of the new technology of machine perception and image understanding in the context of the more well known and classic techniques of image processing, analysis, segmentation and classification is shown below

At the current stage of diagnostics and therapy, it is necessary to perform a geometric evaluation of facial skull bone structures basing upon virtually reconstructed objects or replicated objects with reverse engineering. The objective hereof is an analysis of imaging precision for cranial bone structures basing upon spiral tomography and in relation to the reference model with the use of laser scanning. Evaluated was the precision of skull reconstruction in 3D printing, and it was compared with the real object, topography model and reference model. The performed investigations allowed identifying the CT imaging accuracy for cranial bone structures the development of and 3D models as well as replicating its shape in printed models. The execution of the project permits one to determine the uncertainty of components in the following procedures: CT imaging, development of numerical models and 3D printing of objects, which allows one to determine the complex uncertainty in medical applications.

The water’s edge is the most iconic and identifiable image related to the city of Durban and in seeking an ‘authenticity’ that typifies the built fabric of the city, the image that this place creates is arguably the answer. Since its formal establishment as a settlement in 1824, this edge has been a primary element in the urban fabric. Development of the space has been fairly incremental over the last two centuries, starting with colonial infl uenced built interventions, but much of what is there currently stems from the 1930’s onwards, leading to a Modernist and later Contemporary sense of place that is moderated by regionalist infl uences, lending itself to creating a somewhat contextually relevant image. This ‘international yet local’ sense of place is however under threat from the increasingly prominent ‘global’ image of a-contextual glass high-rise towers placed along a non-descript public realm typical of global capital interests that is a hallmark of the turnkey project trends by developers from the East currently sweeping the African continent.

Evaluating the image quality is a very important problem in image and video processing. Numerous methods have been proposed over the past years to automatically evaluate the quality of images in agreement with human quality judgments. The purpose of this work is to present subjective and objective quality assessment methods and their classification. Eleven widely used and recommended by International Telecommunication Union (ITU) subjective methods are compared and described. Thirteen objective method is briefly presented (including MSE, MD, PCC, EPSNR, SSIM, MS-SSIM, FSIM, MAD, VSNR, VQM, NQM, DM, and 3D-GSM). Furthermore the list of widely used subjective quality data set is provided.