Ultrasound Helps Doctors Go Farther
Ultrasound technology, or ultrasonography, refers to the use of high frequency sound waves, above the threshold of human hearing, to perform a task. In medicine, ultrasound has two broad uses; ultrasound can be used as an imaging modality and diagnostic aid to visualize tissues and organs within the body, and also as a therapeutic modality with a variety of applications. Each of these is discussed in detail. As an imaging modality and diagnostic aid, ultrasound technology reflects short pulses of high-frequency sound waves off of organs and tissues to create an image useful in identifying a variety of diseases and pathological conditions. Diagnostic ultrasound offers several distinct advantages over other medical imaging modalities such as
MRI, CT, or x-Ray.
- Ultrasound captures images in real-time, allowing internal organs and blood flow to be visualized “live” in motion
- Ultrasound has an excellent safety record; patients are not exposed to potentially harmful ionizing radiation
- Ultrasound costs less than many imaging alternatives, particularly MRI
- Ultrasound is portable and can be performed at the bedside
Diagnostic ultrasound is commonly used to image blood flow and vessels (a Doppler ultrasound), soft tissue, the heart (an echocardiogram), and other organs. Diagnostic ultrasound is also often used in obstetrics to estimate fetal age, screen for potential complications of pregnancy such as ectopic pregnancies or uterine abnormalities and bleeding, and can be used to guide needles during procedures such as amniocentesis. Diagnostic ultrasound is also often used in real-time for more accurate needle placement during biopsies and other procedures.
Ultrasound technology has long been used for therapeutic applications, engaging long or continuous pulses of high frequency sound waves to induce cellular effects and biological change. Although exact mechanisms to systematically explain the therapeutic benefits of ultrasound remain unknown, the primary effect of therapeutic ultrasound is thought to be the generation of heat within target tissues, which could have a number of beneficial effects such as increasing blood flow. Another potential mechanism of therapeutic ultrasound at higher intensities involves cavitation, or the creation of small bubbles that can render targeted tissue more porous, thus allowing for the delivery of medications and gene therapy through the skin.
Therapeutic applications of ultrasound technology are dependent upon the intensity used. Low power ultrasonography can be used for treating soft tissue injuries, hastening wound and bone fracture healing, softening scar tissue, and managing swelling-particularly in joints. Higher intensity ultrasonography can be used to destabilize cellular membranes, thus inducing the cavitation necessary to allow gene and drug delivery through the skin. High intensity ultrasound has also shown some promise in targeting tumor cells and other benign masses for cellular destruction, in dissolving blood clots, and in sealing blood vessels to prevent bleeding and block blood and nutrition flow to growing tumors.
When undergoing treatment or imaging with ultrasound technology, a device known as a transducer is placed such that it can aim sound waves at targeted tissue. Water or water-based gels are often used to buffer and help transmit the sound waves from the transducer to the target surface. Ultrasound imaging and treatment are generally painless procedures done over the skin; however some procedures are more invasive in that the transducer is inserted within a natural opening in the body for improved access or effect. Depending on the location and goal, an ultrasound procedure can take anywhere from a few minutes to an hour to perform. In the case of diagnostic ultrasound, a radiologist interprets the image and will report back to the patient and/ or referring doctor.
The future of ultrasound technology for physicians is monitoring needle positioning during surgical pain procedures. With this noninvasive imaging technique, physicians can facilitate his/her needle placement. This technique pro- vides a safe and effective way to assist physicians in delivering pain relief.