The advancements in computer science provide important developments in imaging technology. In parallel with these developments, significant improvements have occurred in ultrasound imaging over the years. The acceptability of ultrasound imaging is high due to its advantages including ease of use, free of radiation, instantaneous availability of findings, noninvasiveness, low price compared to other imaging methods, and excellent record safety, and so this support the phenomenon of continuous innovation. Various advanced technologies have been presented in recent years for clinical use. Some methods can lead to an innovation almost as valuable as real-time as the real-time imaging, Color Doppler imaging, Tissue Harmonic Imaging, Volumetric ultrasound, contrast-enhanced ultrasonography, and elastography are some of them. All of them have already presented great advancements in diagnostic skills. These will be described below.
5.2 Panoramic Imaging
Ultrasonographic imaging has limited fields of view (FOV) area compared with the other imaging techniques such as Computed Tomography (CT), Magnetic Resonance Imaging (MRI) because the image FOV is restricted by the ultrasound probe width and scanning angle [1, 2]. So, the system cannot show a full view of the complete anatomy and it is difficult to acquire an expanded view of superficial structures. Panoramic imaging is an advance ultrasonographic technic which supplies images with a large FOV which is known also as “ultrasound CT” or “panorama ultrasound.” [3] Panoramic imaging provides the transducer to move through the patient’s anatomy and combine multiple images to create one long image with an extremely wide field of view. (Figs. 5.1, 5.2 and 5.3) This component uses cross-correlation methods to correlate consecutive images, revolves and fasten them to produce the final image [4]. While, it is maintaining the traditional benefits of sonography including high spatial resolution, low-cost, and lack of ionizing radiation, it gives expanded-view images with lower distortion that has more easiness in real-time practices [4, 5]. Therefore, panoramic ultrasonography technique is promising in clinical applications.
Fig. 5.1
Panoramic imaging of thyroid gland
Fig. 5.2
Panoramic imaging of vessel
Fig. 5.3
Panoramic Imaging of Superficial Musculoskeletal (MSK) tissues
5.3 Tissue Harmonic Imaging
Various structure layers in the tissue spread the sound wave at different speeds that cause phase shift in the sound wave. The high-pressure part of the sound wave in the tissue moves faster than the low-pressure part which causes an increase in the frequency of the high-pressure part in the waveform. This increase of frequency occuring in the frequency layers of the ultrasound wave are called “Harmonics.” [6] Harmonics have been shown by nonlinear propagation in conventional US physics. Tissue Harmonic Imaging (THI) uses nonlinear portions of ultrasound echo signals reflected from tissue for image production [6–9]. THI can supply higher quality images than conventional gray-scale sonography. While the same frequency spectrum is received, which is transmitted to the patient to produce ultrasonographic images in conventional gray-scale sonography, higher harmonic frequencies produced by the diffusion of ultrasound beam into tissue are used to generate sonograms in THI sonography [6–10] (Fig. 5.4). Many artifacts arise from the interaction of the ultrasound beam with superficial structures are eliminated by using THI sonography. Because the artifact generating signals have no energy to create harmonics, these can be easily filtered while the image is being rendered. THI sonography has many advantages, such as enhanced lateral resolution, diminished side-lobe artifacts, and enhanced signal-to-noise rate. B-mode and Doppler mode of ultrasonography can be used in THI [6–12].
Fig. 5.4
Comparing the images with Tissue Harmonic Imaging (a) Tissue Harmonic Imaging—OFF (b) Tissue Harmonic Imaging—ON
5.4 Real-Time Spatial Compound Imaging
Real-time spatial compound imaging is an ultrasound method which obtain various overlapping scans of an object from different directions and then integrating scans to create a single compound image (Fig. 5.5). In this method, different and irrelevant artifact patterns were produced because of the scanning from different perspectives using electronic beam steering of a transducer array. So, compound images have low levels of speckle, clutter, and other acoustic artifacts. Averaging distinctive patterns constrain artifacts, and thereby enhancing image quality. Real-time spatial compound imaging has higher contrast resolution and tissue distinction than conventional ultrasound images (Figs. 5.6 and 5.7). [4, 5, 9, 10, 13–15]
Comparing the images of carotid artery and jugular vein with Real-Time Spatial Compound Imaging mode (a) Real-Time Spatial Compound Imaging—OFF (b) Real-Time Spatial Compound Imaging—ON
Fig. 5.7
Comparing the images with Real-Time Spatial Compound Imaging mode (a) Real-Time Spatial Compound Imaging—OFF (b) Real-Time Spatial Compound Imaging—ON
5.5 Chromatic Imaging
Chromatic imaging present shades of a different color than gray in gray-scale examination. No different parameter is used in rendering than the gray-scale display. Chromatic imaging provides enhancement of image clarity, the edge acuity, create a difference in visual perception, and presents detail determination (Figs. 5.8, 5.9, 5.10 and 5.11).
Fig. 5.8
Chromatic Imaging of Internal Carotid Artery (ICA)
Fig. 5.9
Chromatic Imaging of Spine
Fig. 5.10
Chromatic Imaging of Fetus
Fig. 5.11
Chromatic Imaging of Bowel
5.6 Volumetric Ultrasound (Three-Dimensional (3D) and Four-Dimensional (4D) Ultrasound Imaging)
Volumetric ultrasound was developed in response to the existing challenges of standard two-dimensional (2D) ultrasound. Volume data acquisition, imaging, and storage capabilities have expanded with advances in high-speed computing technology. Volumetric ultrasonography has proven many advantages with its basic operating principles. It is expected to be a routine part of patient diagnosis and treatment soon [4, 9, 16, 17]. Three perpendicular plans can be displayed simultaneously with this method. Rotating and moving these plans in their circles and moving back and forth to obtain accurate sections for diagnosis and geometric measurement is the greatest advantage of three-dimensional (3D) modality. In this way, 3D ultrasonography combines the advantages of conventional ultrasound (such as safety, ease of application, and low cost) with the advantage of obtaining consecutive sections in an unlimited number and in the desired plane. Sonographic volumes can be stored continuously and used for three-dimensional anatomical reconstructions. In addition, these volumes can be analyzed by examining conventional B-mode planar reformat sections and even images that are not available in routine examinations [4, 9, 16–18] (Figs. 5.12, 5.13, 5.14 and 5.15).
Fig. 5.12
Volumetric ultrasound image of Fetus
Fig. 5.13
Volumetric ultrasound images of fetus in 3 (Three) views
Fig. 5.14
Volumetric ultrasound Tomographic Imaging of Fetal Heart
Fig. 5.15
Volumetric ultrasound images of Spine in 3 (Three) views
3D ultrasound is introduced as volume rendering of ultrasonographic data and it is also named as four-dimension (4D) when it includes a series of 3D volumes gathered in course of the time. Modern ultrasonography equipment can quickly obtain 3D and 4D data sets thanks to their large computing power. The obtained volume from reconstructed 3D dataset can be presented as different forms including transparent appearance, surface rendering mode or maximum intensity projection (MIP). Furthermore, 3D presentations show topography and volume information [16–20].
5.7 Contrast-Enhanced Ultrasound Imaging
A contrast-enhanced ultrasound imaging (CEUI) is a method which uses specific contrast agents consist of encapsulated microbubbles enhancing the characterization of anatomic structures with the scanning of slight vascular structures [5, 9, 17, 21–24]. Microbubbles make up of a gas core and external shell contributing stability. These are nearly 1–10 mm in size. The main purpose of ultrasonographic contrast agents is to increase the signal intensity returning to the transducer. The primary mechanism of signal increase is the scattering of ultrasound beam caused by microbubbles instead of blood. When the contrast material is used together with harmonic imaging, a significant increase in image quality is achieved. Tissue harmonics formed in tissue are less severe than harmonics formed by microbubbles [5, 9, 17, 21–26]. CEUI is an economical, safe, and efficient method with multiple clinical procedures. This technique can be used to characterize different perfusion models that are effective in distinguishing abnormal tissues from normal tissues (Figs. 5.16 and 5.17). CEUI could be a useful tool for evaluation of metastases in lymph nodes, differential diagnosis of benign and malignant thyroid nodules [5, 9, 17, 21–26].
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