On punctate white matter lesions in preterm infants: Is ultrasound diagnosis feasible?

Objectives: To observe hyperechoic nodular or punctate white matter lesions (HNPL) in a population of preterm infants using routine cranial ultrasound (cUS), to describe the characteristics of HNPL, and to compare them with punctate white matter lesions (PWML) detected in magnetic resonance imaging (MRI).

Design: Retrospective observational single-center cohort study.

Setting: Level 2B neonatal unit in France.

Semi-automatic data annotation based on feature-space projection and local quality metrics: An application to cerebral emboli characterization.

We propose a semi-supervised learning approach to annotate a dataset with reduced requirements for manual annotation and with controlled annotation error. The method is based on feature-space projection and label propagation using local quality metrics. First, an auto-encoder extracts the features of the samples in an unsupervised manner.

Automatic segmentation and location learning of neonatal cerebral ventricles in 3D ultrasound data combining CNN and CPPN.

Preterm neonates are highly likely to suffer from ventriculomegaly, a dilation of the Cerebral Ventricular System (CVS). This condition can develop into life-threatening hydrocephalus and is correlated with future neuro-developmental impairments. Consequently, it must be detected and monitored by physicians.

A gradient-based optical-flow cardiac motion estimation method for cine and tagged MR images.

A new method is proposed to quantify the myocardial motion from both 2D C(ine)-MRI and T(agged)-MRI sequences. The tag pattern offers natural landmarks within the image that makes it possible to accurately quantify the motion within the myocardial wall. Therefore, several methods have been proposed for T-MRI.

Multi-Grid Phase Field Skin Tumor Segmentation in 3D Ultrasound Images.

The aim of this paper is to present a new method for skin tumor segmentation in the 3D ultrasound images. We consider a variational formulation, the energy of which combines a diffuse interface phase field model (regularization term) and a log-likelihood computed using nonparametric estimates (data attachment term). We propose a multi-grid implementation with the exact solutions which has the advantage to avoid space discretization and numerical instabilities.

Joint segmentation and characterization of the dermis in 50 MHz ultrasound 2D and 3D images of the skin.

We propose a novel joint segmentation and characterization algorithm for the assessment of skin aging using 50 MHz high-frequency ultrasound images. The proposed segmentation method allows a fine determination of the envelope signal's statistics in the dermis as a function of depth. The sequence of statistical estimates obtained is then combined into a single aging score.

Sequential Emboli Detection From Ultrasound Outpatient Data.

This paper addresses the detection of emboli from signals acquired with a new miniaturized and portable transcranial Doppler ultrasound device. The use of this device enables outpatient monitoring but increases the number of artifacts. These artifacts usually come from the patient voice and motion and can be superimposed to emboli.

Improved boundary segmentation of skin lesions in high-frequency 3D ultrasound.

In this article, we propose a segmentation algorithm for skin lesions in 3D high-frequency ultrasound images. The segmentation is done on melanoma and Basal-cell carcinoma tumors, the most common skin cancer types, and could be used for diagnosis and surgical excision planning in a clinical context. Compared with previously proposed algorithms, which tend to underestimate the size of the lesion, we propose two new boundary terms which provide significant improvements of the accuracy.

Discrimination between emboli and artifacts for outpatient transcranial Doppler ultrasound data.

This paper addresses the detection of emboli in transcranial Doppler ultrasound data acquired from an original portable device. The challenge is the removal of several artifacts (motion and voice) intrinsically related to long-duration (up to 1 h 40 mn per patient) outpatient signals monitoring from this device, as well as high intensities due to the stochastic nature of blood flow. This paper proposes an adapted removal procedure.

Estimation of cardiac motion in cine-MRI sequences by correlation transform optical flow of monogenic features distance.

Cine-MRI is widely used for the analysis of cardiac function in clinical routine, because of its high soft tissue contrast and relatively short acquisition time in comparison with other cardiac MRI techniques. The gray level distribution in cardiac cine-MRI is relatively homogenous within the myocardium, and can therefore make motion quantification difficult. To ensure that the motion estimation problem is well posed, more image features have to be considered.

Segmentation of Skin Tumors in High-Frequency 3-D Ultrasound Images.

High-frequency 3-D ultrasound imaging is an informative tool for diagnosis, surgery planning and skin lesion examination. The purpose of this article was to describe a semi-automated segmentation tool providing easy access to the extent, shape and volume of a lesion. We propose an adaptive log-likelihood level-set segmentation procedure using non-parametric estimates of the intensity distribution.

Internal strain estimation for quantification of human heel pad elastic modulus: A phantom study.

Shock absorption is the most important function of the human heel pad. However, changes in heel pad elasticity, as seen in e.g.

Motion estimation in ultrasound imaging applied to the diagnostic of pelvic floor disorders.

The main purpose of this paper is to show the potential of tissue motion estimation in ultrasound imaging for the diagnostic of pelvic floor disorders. We propose to evaluate the tissue motion using a method based on a local deformable model and on image features (local phase and orientation) extracted from the monogenic signal. The proposed method is well adapted to the pelvic organ deformations and estimates motion with subpixel precision without the need for interpolation.

Motion estimation using the monogenic signal applied to ultrasound elastography.

This paper presents a phase-based method for estimating subpixel motion in medical ultrasound imaging. The main novelty is to propose a closed form expression for local motion estimation in space domain based on the model of the monogenic signal. First, the proposed method uses the properties of the monogenic signal in order to extract local orientation and phase data of ultrasound images.

Blood flow evaluation in high-frequency, 40 MHz imaging: a comparative study of four vector velocity estimation methods.

Ultrasonic imaging is often used to estimate blood flow velocity. Currently, estimates are carried out using Doppler-based techniques. However, there are a number of shortcomings such as the limited spatial resolution and the inability to estimate longitudinal flows.

Transverse oscillations for tissue motion estimation.

This paper gives an overview of the methods developed for tissue motion estimation using transverse oscillation images (TO). TO images are specific radiofrequency ultrasound images featuring oscillations in both spatial directions. The initial studies on TO were published in the late 1990s.

Analysis of motion tracking in echocardiographic image sequences: influence of system geometry and point-spread function.

This paper focuses on motion tracking in echocardiographic ultrasound images. The difficulty of this task is related to the fact that echographic image formation induces decorrelation between the underlying motion of tissue and the observed speckle motion. Since Meunier's seminal work, this phenomenon has been investigated in many simulation studies as part of speckle tracking or optical flow-based motion estimation techniques.

Phase-based block matching applied to motion estimation with unconventional beamforming strategies.

A phase-based block matching method adapted to motion estimation with unconventional beamforming strategies is presented. The unconventional beamforming technique used allows us to obtain 2-D RF images with axial and lateral modulations. Based on these images, we propose a method that uses phase images instead of amplitude images.

Investigation of PVA cryogel Young's modulus stability with time, controlled by a simple reliable technique.

We describe a quasistatic method for mechanical characterization of tissue-mimicking material used in elastography. We demonstrate that it is possible to assess the elasticity modulus with a reasonable reproducibility using simple and easy tools and methods. Possessing a simple relevant technique with evaluated relative error to assess Young's modulus of these phantoms could deeply improve the quality of the research in the field of elastography.

Analytic estimation of subsample spatial shift using the phases of multidimensional analytic signals.

In this correspondence, a method of analytic subsample spatial shift estimation based on an a priori n-D signal model is proposed. The estimation uses the linear phases of n analytic signals defined with the multidimensional Hilbert transform. This estimation proposes: i) an analytic solution to the n-D shift estimation and ii) an estimation without processing complex cross-correlation function or cross-spectra between signals contrary to most phase shift estimators.

Lateral RF image synthesis using a synthetic aperture imaging technique.

The oscillating profile naturally present in ultrasound images has been shown to be extremely valuable in different applications, particularly in motion estimation. Recent studies have shown that it is possible to produce images with transverse oscillations (TOs) based on a specific type of beamforming. However, there is still a great difference between the nature of the lateral oscillations produced with current methods and the axial profile of ultrasound images.

A method for vector displacement estimation with ultrasound imaging and its application for thyroid nodular disease.

Ultrasound elastography is a promising imaging technique that can assist in diagnosis of thyroid cancer. However, the complexity of the tissue movements under freehand compression requires the use of a parametric displacement model and a specific estimation method adapted to sub-pixel motion. Therefore, the aim of this study was to develop a motion estimation method for ultrasound elastography and test its performances compared to a classical block matching technique.

Static mechanical assessment of elastic Young's modulus of tissue mimicking materials used for medical imaging.

Emerging medical imaging techniques usually provide quantitative diagnostic parameters. Since the description of a method for quantitative imaging of strain and elastic modulus distributions in soft tissues by Ophir et al. in 1991, research in elastography is progressing and experimental in vitro validation of new displacement estimators appears crucial for clinical applications.

Two-dimensional least-squares estimation for motion tracking in ultrasound elastography.

This paper proposes a method of 2-D translations estimation using an a priori signal model. Two analytical signals defined with multidimensional Hilbert transform are considered and shown to have linear phases with respect to the translations to estimate. A least squares estimator (LSE) is then developed to adjust the measured phases of the complex signals to their theoretical forms.