Ultrasound physics and instrumentation for pathologists.
ABSTRACT Interest in pathologist-performed ultrasound-guided fine-needle aspiration is increasing. Educational courses discuss clinical ultrasound and biopsy techniques but not ultrasound physics and instrumentation.
To review modern ultrasound physics and instrumentation to help pathologists understand the basis of modern ultrasound.
A review of recent literature and textbooks was performed.
Ultrasound physics and instrumentation are the foundations of clinical ultrasound. The key physical principle is the piezoelectric effect. When stimulated by an electric current, certain crystals vibrate and produce ultrasound. A hand-held transducer converts electricity into ultrasound, transmits it into tissue, and listens for reflected ultrasound to return. The returning echoes are converted into electrical signals and used to create a 2-dimensional gray-scale image. Scanning at a high frequency improves axial resolution but has low tissue penetration. Electronic focusing moves the long-axis focus to depth of the object of interest and improves lateral resolution. The short-axis focus in 1-dimensional transducers is fixed, which results in poor elevational resolution away from the focal zone. Using multiple foci improves lateral resolution but degrades temporal resolution. The sonographer can adjust the dynamic range to change contrast and bring out subtle masses. Contrast resolution is limited by processing speed, monitor resolution, and gray-scale perception of the human eye. Ultrasound is an evolving field. New technologies include miniaturization, spatial compound imaging, tissue harmonics, and multidimensional transducers. Clinical cytopathologists who understand ultrasound physics, instrumentation, and clinical ultrasound are ready for the challenges of cytopathologist-performed ultrasound-guided fine-needle aspiration and core-needle biopsy in the 21st century.
SourceAvailable from: Ghaleb A. Husseini[Show abstract] [Hide abstract]
ABSTRACT: Chemotherapy is widely used for cancer treatment; however, it causes unwanted side effects in patients. To avoid these adverse effects, nanocarriers have been developed, which can be loaded with the chemotherapeutic agents, directed to the cancer site and, once there, be exposed to stimuli that will trigger the drug release. Liposomes can be chemically modified to increase their circulation time, their stability, and their sensitivity to specific stimulus. Additionally, ligands can be conjugated to their surface, allowing for their specific binding to receptors overexpressed on the surface of cancer cells and the subsequent internalization via endocytosis. Using a triggering mechanism, including temperature, ultrasound, enzymes or a change in pH, the release of the drug is controlled and induced inside the cells, hence avoiding drug release in systemic circulation, which in turn reduces the undesired side effects of conventional chemotherapy. Ultrasound has been widely studied as a drug release trigger from liposomes, due to its well-known physics and previous uses in medicine. This review focuses on liposome-based drug delivery systems, using different trigger mechanisms, with a focus on ultrasound. The physical mechanisms of ultrasound release are also investigated and the results of in vitro and in vivo studies are summarized.Current Cancer Drug Targets 03/2015; 15(999). DOI:10.2174/1568009615666150311100610 · 3.58 Impact Factor
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ABSTRACT: Pathologist performance of ultrasound-guided fine-needle aspiration (USFNA) is an exciting new practice frontier that has been gaining national interest during the last few years. Herein, I provide an introductory pictorial essay on how to perform the free-hand technique of USFNA. I have divided this “how-to” USFNA essay into a 4-step process starting with (1) echolocation of the target for aspiration; followed by (2) planning the needle approach to the target lesion; (3) placing the needle using ultrasound guidance, including discussion of both parallel and perpendicular approaches; and finally (4) documenting the target lesion and needle placement. Being proficient in palpation-guided FNA is a prerequisite for an easier transition to USFNA, and it will be assumed that the reader has at least some experience in palpation-guided FNA. Understanding the basics of ultrasound physics and instrumentation, attending a certification course on USFNA, and practicing USFNA on phantoms until the operation of the US machine and needle placement skills are automatic are essential minimal requirements that need to be achieved before making the transition to USFNA on patients.Pathology Case Reviews 01/2013; 18(1):18-23. DOI:10.1097/PCR.0b013e318281c8d9
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ABSTRACT: Mirror artifacts are produced by the reflection of ultrasound waves after they propagate through a structure and encounter a strong and smooth interface capable of acting as a mirror. Ultrasound waves bounce back and forth between the mirroring interface and the reflective object and then eventually return to the transducer. The typical display of the mirror artifact consists of two similar structures separated and at similar distances from the reflective interface. We report a mirror artifact in a patient with a singleton gestation at 18 weeks. The image was interpreted as consistent with a twin gestation using transabdominal and transvaginal ultrasound. The differential diagnosis consisted of an abdominal heterotopic pregnancy. The presence of synchronized but opposite movements of both fetuses, and the blurred image of the second fetus, suggested a mirror artifact. The reflective surface was created by the interface located between a distended rectosigmoid filled with gas and the posterior uterine wall. Mirror artifacts can lead to diagnostic errors. This case illustrates how a distended rectosigmoid colon can generate an image that simulates either a twin gestation or an abdominal heterotopic pregnancy.Fetal Diagnosis and Therapy 09/2013; DOI:10.1159/000353702 · 2.30 Impact Factor