Recent trends in ultrasound imaging

For the last five decades, ultrasound has been one of the primary diagnostic modalities with unique advantages – primarily lack of radiation, easy availability, excellent spatial and temporal resolution, real-time capability, and safety. It has seen a continuous and tremendous advancement in technology from A-mode to M-mode, B-mode, Doppler imaging, contrast enhanced ultrasound, US elastography, 3D and 4D imaging, high-definition intravascular ultrasound, laparoscopic, endoscopic, and intraoperative ultrasound. Here we shall have a brief look at some of the recent and nascent innovations in ultrasound imaging.

Super-resolution ultrasound imaging. Super-resolution ultrasound directly measures vessel density, inter-distance, size, unique flow pattern, and fractal factor. Super-resolution separates echoes coming from sources closer than the classic diffraction limit.

Ultrasound molecular imaging. Molecularly-targeted contrast agents can visualize disease processes at the molecular level and monitor disease processes that are characterized by a differential expression of molecules on the vasculature, such as cancer or inflammatory diseases.

Volumetric ultrasound. Volumetric ultrasound technology is used to create images with more depth and detail than traditional sonograms do. They can be used to identify tumors, analyze cardiac function, and more. It gets its name from the ability to produce images with more visual volume, rather than a flat appearance, closely replicating the actual appearance of organs and systems.

Radiomic ultrasound analysis. Radiomics describes the use of radiological data in a quantitative manner to establish correlations in between imaging biomarkers and clinical outcomes to improve disease diagnosis, treatment monitoring, and prediction of therapy responses.

Photoacoustic imaging. It is an emerging modality that uses a combination of optical excitation and acoustic detection for visualizing vascular, functional, and molecular changes within living tissue.

Ultra-high-frequency imaging. High-frequency ultrasound imaging, using frequencies above 20 MHz, enable the imaging of superficial structures at very high resolution of 50 microns. Applications include the anterior chamber of the eye, intravascular ultrasound of arterial walls, skin, and cartilage.

Extended field of view imaging. It combines static B-mode with real-time imaging so that a large subject area can be viewed on a single static image.

Three- and four-dimensional imaging. With 3-D ultrasound, an image of the surface of a structure is produced, which can be rotated through different planes and the surface viewed from many angles as also the inside of the structure. The same viewed in the time axis gives 4D imaging.

Other developments in the field include harmonic imaging, pulse-inversion imaging, elastography, compound imaging, tissue characterization, portable ultrasound machines, ultrasound-controlled fluorescence technology for deep-tissue optical imaging, high-intensity focused ultrasound (HIFU), fetal intelligent navigation echocardiography (FINE), 3D printing, fetal HQ, precision focused ultrasound surgery technology that destructs only the desired tissues, deep learning, and artificial intelligence.

Futuristically speaking, refined image postprocessing tools will enable quantitative multiparametric image analysis. True 3D imaging, and super-resolution imaging methods will contribute to improved image quality, and for radiomics analysis. The therapeutic perspectives for ultrasound are being evaluated in oncology and for neurologic and cardiovascular disorders and uterine fibroids. Furthermore, sonoporation-based drug delivery has proved promising, stimulating research on theranostic microbubbles.

In conclusion, ultrasound has evolved into a cutting-edge imaging modality with a highly impressive set of diagnostic and therapeutic techniques in its repertoire. Ultrasound has more than fulfilled the expectations evoked by it, when it came into use half a century back, and has contributed immensely to the advancement of scientific knowledge and mitigation of human suffering.