Ultrasound in Radiology

Abstract

During the past decade, ultrasound has expanded medical imaging well beyond the “traditional” radiology setting - a combination of portability, low cost and ease of use makes ultrasound imaging an indispensable tool for radiologists as well as for other medical professionals who need to obtain imaging diagnosis or guide a therapeutic intervention quickly and efficiently. Ultrasound combines excellent ability for deep penetration into soft tissues with very good spatial resolution, with only a few exceptions (i.e. those involving overlying bone or gas). Real-time imaging (up to hundreds and thousands frames per second) enables guidance of therapeutic procedures and biopsies; characterization of the mechanical properties of the tissues greatly aids with the accuracy of the procedures. The ability of ultrasound to deposit energy locally brings about the potential for localized intervention encompassing: tissue ablation, enhancing penetration through the natural barriers to drug delivery in the body and triggering drug release from carrier micro- and nanoparticles. The use of microbubble contrast agents brings the ability to monitor and quantify tissue perfusion, and microbubble targeting with ligand-decorated microbubbles brings the ability to obtain molecular biomarker information, i.e., ultrasound molecular imaging. Overall, ultrasound has become the most widely used imaging modality in modern medicine; it will continue to grow and expand.

Intra-Animal Comparison between Three-dimensional Molecularly Targeted US and Three-dimensional Dynamic Contrast-enhanced US for Early Antiangiogenic Treatment Assessment in Colon Cancer

“…Our findings show that US parameters obtained with both 3D molecularly targeted US and destruction-replenishment DCE US correlated well with the respective ex vivo reference standards, while bolus DCE US did not. Molecularly targeted US is a quantitative technique to monitor molecular markers in vivo (12–14,19). The imaging signal linearly correlates with the number of molecularly attached microbubbles (37), which depends on the number of tumor vessels that express the angiogenic marker, such as VEGFR2, and the density of the marker expression per tumor vessel area.…”

“…In parallel, US performed with molecularly targeted microbubble contrast agent has become a promising technique to visualize, characterize, and quantify biological processes at the molecular level in vivo (12–14), including tumor angiogenesis–associated molecular markers such as vascular endothelial growth factor receptor 2 (VEGFR2) (15–18). A clinical-grade VEGFR2-targeted US microbubble agent has been designed and translated into clinical trials (19).…”

Increasing Distribution of Drugs Released from In Situ Forming PLGA Implants Using Therapeutic Ultrasound

“…To overcome these challenges, ultrasound can be enlisted as a safe external force to facilitate drug release and distribution in vivo . 11, 16, 32, 33 Several prior studies have examined the use of ultrasound to enhance drug release from polymer implants. 5, 6, 22 In contrast to the current study, these studies included gas bubbles or generation of heat, which were able to drive drug release via inertial cavitation and/or mild hyperthermia.…”

“…Ultrasound exposure has also been shown to significantly increase degradation rate of the polymer matrix, especially polyanhydrides, or reform the structure of the polymer such as cross-link hydrogel or shape memory polymers. 4, 9, 12-14, 21 However, while the use of ultrasound for active, on demand, delivery of drugs has been under extensive investigation 1, 11, 30, 33 , its application in increasing drug distribution upon release from in situ forming polymer implants has not been investigated.…”

“…In addition to common clinical applications ultrasound has also been used to facilitate drug release on demand in transdermal drug delivery systems and nanoparticles 20 and has been shown to improve the penetration of nanoscale particles at the target site, allowing them to pass though epithelial cells or barriers. 11, 32, 33 In this process, typically it is the mechanical and thermal effects which are associated with an increase in penetration, perfusion or release of the drug. 6, 33 Recently ultrasound was also used to control release of insulin from a gel-like network system consisting of alginate-coated nanoparticles and chitosan-coated nanoparticles.…”