4d ultrasound research papers
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A Review on Real-Time 3D Ultrasound Imaging Technology
Real-time three-dimensional 3D ultrasound US has attracted much more attention in medical researches because it provides interactive feedback to help clinicians acquire high-quality images as well as timely spatial information of the scanned area and hence is necessary in intraoperative ultrasound examinations.
Plenty of publications have been declared to complete the real-time or near real-time visualization of 3D ultrasound using volumetric probes or the routinely used two-dimensional 2D probes. So far, a review on how to design an interactive system with appropriate processing algorithms remains missing, resulting in the lack of systematic understanding of the relevant technology.
In this article, previous and the latest work on designing a real-time or near real-time 3D ultrasound imaging system are reviewed. Specifically, the data acquisition techniques, reconstruction algorithms, volume rendering methods, and clinical applications are presented. Moreover, the advantages and disadvantages of state-of-the-art approaches are discussed in detail. Each imaging modality has its strengths and limitations in different applications [ 1 ].
Among these diagnosis-aid technologies, US gains more and more attention in recent years. Aside from low cost and no radiation, the interactive nature of US which is mostly needed in surgery facilitates its widespread use in clinical practices. Conventional 2D US has been widely used because it can dynamically display 2D images of the region of interest ROI in real-time [ 2 , 3 ]. However, due to the lack of the anatomy and orientation information, clinicians have to imagine the volume with the planar 2D images mentally when they need the view of 3D anatomic structures.
The limitation of 2D US imaging makes the diagnostic accuracy much uncertain as it heavily depends on the experience and knowledge of clinicians. In order to address the foresaid problem, 3D US was proposed to help the diagnosticians acquire a full understanding of the spatial anatomic relationship.
Physicians can view arbitrary plane of the reconstructed 3D volume as well as panoramic view of the ROI which helps surgeons to ascertain whether a surgical instrument is placed correctly within the ROI or just locates peripherally during the surgery [ 4 ]. It is undeniable that 3D US enables clinicians to diagnose fast and accurately as it reduces the time spent on evaluating images and interacts with diagnosticians friendly to obtain a handle of the shape and location of the lesion.
Generally, 3D US imaging can be conducted with three main stages: that is, acquisition, reconstruction, and visualization. The acquisition refers to collecting the B-scans with relative position using conventional 2D probes or directly obtaining 3D images using dedicated 3D probes.
The reconstruction aims to insert the collected 2D images into a predefined regular volume grid. The visualization is to render the built voxel array in a certain manner like any-plane slicing, surface rendering, or volume rendering. Traditional 3D US is temporally separated into the B-scan frame collection, volume reconstruction, and visualization stages individually, making it time-consuming and inefficient to obtain an accurate 3D image.
Clinician has to wait for the data collection and volume reconstruction which often take several minutes or even longer time before visualizing any part of the volume, rather than visualizing 3D anatomy simultaneously during the scanning of the ROI. Hence the clinician cannot select an optimal way to conduct the scanning process for subsequent diagnosis. Moreover, the separation has limited the applications in surgery where physicians require immediate feedback on intraoperative changes in the ROI [ 5 ].
Many investigators have made their efforts to develop the real-time or near real-time US systems in recent decade. Several attempts with the dedicated 3D probe or traditional 2D probe to reconstruct and render a volume during data acquisition are now available. To provide systematic understanding of the relevant technology in real-time US, we review the state-of-the-art approaches for designing real-time or near real-time 3D US imaging system.
Data acquisition techniques, reconstruction algorithms, rendering methods, and clinical applications are discussed in the following sections, including the advantage and disadvantages of each approach. Obtaining 3D real-time US image without distortions is crucial for the subsequent clinical diagnosis. In any approach of data acquisition, the objectives are twofold: first to acquire relative locations and orientations of the tomographic images accurately, which ensures the 3D reconstruction without errors, and second to capture the ROI expeditiously, which is aimed at avoiding the artifacts caused by cardiac, respiratory, and involuntary motion, as well as enabling the 3D visualization of dynamic structures in real-time.
Four representative real-time 3D US data acquisition techniques have been proposed, that is, 2D array transducers, mechanical 3D probes, mechanical localizers, and freehand scanners. In conventional 1D array transducer, a subset of transducer elements or subaperture is sequentially selected to send an acoustic beam perpendicularly to the transducer surface, and one line is drawn at the same time. Through multiplexing or simply turning elements on and off, the entire aperture can be selected which forms a rectangular scan [ 6 ].
Analogously, 2D array transducers derive an acoustic beam steering in both azimuth and elevation dimensions, which enables obtaining a volumetric scan [ 7 ]. As illustrated in Figure 1 , the elements of 2D array transducer generate a diverging beam in a pyramidal shape and the received echoes are processed to integrate 3D US images in real-time.
Since the beams can be steered and focused on the ROI by adjusting the phased array delays [ 8 ], the transducers can remain stationary while being used to scan. A variety of 2D array patterns are proposed to fabricate 2D array transducers, such as sparse periodic array, Mills cross array [ 9 ], random array, and Vernier array.
As 1D linear transducers, 2D array transducers can be sorted of concave surface and flat surface. Concave transducers have an advantage of concentrating a higher energy to the focal areas. Flat transducers have a wider steerable area of acoustic field [ 10 ]. The elements of 2D array transducers can be arranged as either a rectangle or an annular array [ 11 ]. The substrates of 2D array transducers can be fabricated with various piezoelectric materials Figure 2 , such as lead zirconate titanate PZT , lead magnesium niobate—lead titanate PMN—PT , and piezocomposites [ 12 ].
Aside from piezoelectric transducers, capacitive micromachined US transducers CMUTs have also shown a potential performance as their counterparts [ 13 ].
Since the concept of 2D array transducers was proposed by Duke University in s, various researchers and commercial companies are concentrated on the development of 2D array transducers. The real-time performance and fabrication parameters of several typical 2D array transducers are listed in Table 1. Although 2D array transducers are capable of realizing the 3D visualization of dynamic structures in real-time directly and ideally, the electrical impedance of each element in 2D array transducers is much greater than that in 1D array transducers, which makes impedance matching of 2D array elements challenging [ 14 ].
Furthermore, to avoid the cross-talk between elements, a half-wavelength distance is needed for the neighbor elements, which results in a large number of elements and extremely small size of each element. To reduce the difficulties in fabrication of 2D array transducer, the size of the array cannot be large, which leads to a small field of view in imaging.
Several problems should be resolved before 2D array transducer becoming widespread in clinical examinations. Other 3D probes are developed for real-time 3D US imaging by assembling a linear array transducer inside a handheld instrument Figure 3. In a mechanical 3D probe, a regular linear array transducer is motored to rotate, tilt, or translate within the probe under the computer control [ 15 ].
Multiple 2D images are acquired over the examined area when the motor is activated [ 16 ]. The axis of rotation, tilt, or translation can be used as reference frame for 3D images reconstruction. Three types of mechanical scanning are illustrated in Figure 4 , that is, linear scanning, tilting scanning, and rotational scanning. In this approach, the transducer is driven by a mechanism to translate across the ROI.
The scanning route of the transducer is parallel to the surface of the skin and perpendicular to the image plane. The acquired images are parallel and equidistantly spaced and their spacing interval can be adjusted by changing the image frame rate. The resolution of 3D images produced by this approach is not isotropic.
The resolutions in the directions parallel to acquired 2D image planes are the same as the original 2D images, and the resolution in the direction of scanning route depends on the elevational resolution of mechanical 3D probe. In the tilting scanning, the transducer is motored to tilt about an axis at the transduce surface. A fan of planes is acquired and the angular separation between images is adjustable, which depends on the rotational speed of motors and the image frame rate.
When acquiring images, the probe should be fixed on the skin of patients. The resolution of produced 3D images is not isotropic which degrades as the distance from the tilt axis increases. The time of obtaining 3D volume depends on image update rate and the quantity of the required images. In rotational scanning method, the transducer is driven to rotate with central axis of the probe. The axis should remain fixed when the ROI is being scanned.
The rotational scanning probe is sensitive to the motion of transducer such that resulting 3D images will contain artifacts if any motion occurs during the scan.
The resolution of the obtained 3D images is also not isotropic. The resolution will degrade as the distance from the axis increases. If a convex transducer is assembled in the probe, the corresponding resulting 3D images will be in a conical shape; otherwise, a cylinder will be obtained when a flat transducer is employed.
For various applications in clinical practice, a variety of mechanical 3D probes are developed in recent decades. For instance, Downey and Fenster [ 17 ] proposed a real-time 3D US imaging system which consists of rotating and linear mechanical 3D probes for different applications.
The sequence of images can be acquired at The system has been applied in breast, prostate, and vascular examination, and the acquisition resolution can be set as 0. Mechanical 3D probes are made compactly and they are convenient to operate, though they are comparatively larger than conventional linear probes.
The needed imaging and reconstruction time is short which enables viewing high-quality 3D images in real-time. However, clinicians are required to hold the mechanical 3D probes statically while acquiring images, which will lead to latent errors for data acquisition. Furthermore, a particular mechanical motor is needed for integrating with transducer, which is lack of universality. Similar to mechanical 3D probes, mechanical localizers are driven by motorized mechanisms. In a 3D mechanical probe, the scanning mechanism is integrated inside a handheld instrument together with a special 1D linear transducer.
Nevertheless, a mechanical localizer consists of an external fixture which holds a conventional 1D transducer to acquire a series of sequential 2D images [ 18 , 19 ]. Generally, the scanning route is predefined such that the relative positions and orientations of acquired 2D images can be precisely recorded in computers.
With this location information, 3D US images can be reconstruction in real-time. The angular and spacing interval between each frame can be adjusted to obtain optimal resolution and minimize the scanning time. Similar to mechanical 3D probes, the patterns of mechanical localizers scanning can be grouped into 3 types: that is, linear, tilt, and rotation. Several mechanical localizers systems have been proposed for real-time 3D US imaging, such as Life Imaging System L3Di 3D US acquisition system, which can drive probes in linear scanning for carotid arteries diagnosis [ 20 ].
The mechanical localizers have capacity of holding any conventional transducers such that they can undertake the developed US imaging probes without any update to themselves [ 21 ]. However, the mechanical localizers are always enormous and heavy, making them inconvenient in applications. Obviating the need for cumbersome mechanism, freehand scanners are flexible and convenient to operate. Using a freehand scanner, clinicians can scan the ROI in arbitrary directions and positions, enabling clinicians to choose optimal views and accommodate complexity of anatomy surface.
Positions and orientations of 2D B-scans are needed for reconstructing 3D images. Four approaches with different positional sensors were proposed for tracking the US probe: that is, acoustic positioner, optical positioner, articulated arm positioner, and magnetic field sensor Figure 5. In addition, image-based approaches without positional sensors were also developed, for example, speckle decorrelation. In this approach, three sound emitting devices are mounted fixedly on the transducer, and an array of microphones is placed over the patient.
The microphones receive acoustic wave continuously from sound emitters during the scanning. Positions and orientations can be calculated for reconstructing 3D images with knowledge of the speed of sound in air, the measured time-of-flight from each sound emitter to microphones, and the positions of microphones [ 22 ]. To guarantee a good signal-to-noise ratio SNR , microphones should be placed closely to the patients and the space between emitters and microphones should be free of obstacles.
A freehand transducer with optical positioner system consists of passive or active targets fixed on the transducer and at least two cameras used to track targets. By observing targets from 2D images, the position and orientation can be calculated with knowledge of relative positions of targets [ 23 ].
Optical positioners can be divided into passive stereovision system and active marker system.
Inclusion criteria were as follows: (1) studies related to the use of 3DUS or 4DUS in perinatal medicine; (2) full text were available in English; (3). View 3D/ 4D ultrasound Research Papers on parrotsprint.co.nz for free.
Medical ultrasound also known as diagnostic sonography or ultrasonography is a diagnostic imaging technique, or therapeutic application of ultrasound. It is used to create an image of internal body structures such as tendons , muscles , joints, blood vessels, and internal organs. Its aim is often to find a source of a disease or to exclude pathology. The practice of examining pregnant women using ultrasound is called obstetric ultrasound , and was an early development and application of clinical ultrasonography.
Children cerebral palsy CCP encompasses a group of nonprogessive and noninfectious conditions, which cause light, moderate, and severe deviations in neurological development. Diagnosis of CCP is set mostly by the age of 3 years.
Real-time three-dimensional 3D ultrasound US has attracted much more attention in medical researches because it provides interactive feedback to help clinicians acquire high-quality images as well as timely spatial information of the scanned area and hence is necessary in intraoperative ultrasound examinations. Plenty of publications have been declared to complete the real-time or near real-time visualization of 3D ultrasound using volumetric probes or the routinely used two-dimensional 2D probes.
3D/4D Sonography
Three-dimensional 3D ultrasound has been the most rapidly evolving technique and technology in fetal ultrasound in the past few years [ 1 ], [ 2 ], [ 3 ]. In fact, it is fair to say that, the technology advances have been so profound that most sonologists have caught up with recent developments. It is the most widely used imaging technology worldwide. Its popularity has greatly increased due to availability, speed and low cost. With enhancement in computer technology doing real-time processing, we are starting to get images that are so clear; patients do not even realize the images are ultrasound. The tremendous technological advances developed by prenatal ultrasound diagnosis are unmatched in other areas of medicine.
The Role of 4D Ultrasound in the Assessment of Fetal Behaviour
Fetal behavioral patterns have been considered as indicators of fetal brain development. Numerous studies employing conventional 2D ultrasound have shown that normally developing fetuses and fetuses at risk exhibit different patterns of behavior. With the appearance and development of 4D ultrasound, fetal behavioral movements, and the full range of facial expressions can be observed. After standardization of valid reference ranges of movements appropriate for the gestational age, the Zagreb group published a new scoring system for fetal neurobehavior based on prenatal assessment by 4D sonography, the Kurjak Antenatal Neurological Test. The aims and objectives of this article were to describe the latest 4D sonographic studies on fetal behavior and to present results of behavioral assessment by KANET in high-risk pregnancies. Fetal behavior can be described as any fetal action or reaction observed by the mother or more objective method, such as ultrasonography [ 1 ]. Analysis of the fetal dynamics in comparison with morphological studies led to the conclusion that fetal behavior reflects the activity of the fetal CNS [ 2 ]. Therefore, it was assumed that the evaluation of fetal behavior in different periods of gestation might give the possibility to differentiate normal from abnormal brain development, and enable early diagnosis of various structural or functional abnormalities [ 3 ].
Fetal behavior is defined as any fetal action seen by the mother or fetus diagnosed by objective methods such as cardiotocography CTG or ultrasound. Analysis of the dynamics of the fetal behavior with morphological studies has lead to the conclusion that fetal behavior patterns are directly reflecting development and maturation of the central nervous system.
Metrics details. Pregnant women who are at risk of preterm birth are often stressed, anxious and depressed because of worries and fears related to the health of the unborn baby, their own health and uncertainty about the future. Only a few studies have assessed the types of psychological support that would relieve these stress symptoms among women with high-risk pregnancies. This qualitative study was conducted at one university hospital in Finland in
