A Beginner’s Guide to Ultrasound Technology

The Importance of Ultrasound

Diagnostic ultrasound, or sonography, is a common, noninvasive method for taking real time images from inside your body. The first thing that may come to mind when you think about ultrasound is probably pregnancy. This makes sense, as ultrasound is a bit of a gold standard for obstetrics and gynecology. Safe and gentle, routine scanning for pregnant women can aid in preventing perinatal and maternal mortality due to complications such as prematurity, birth asphyxia and congenital malformations1. Sonography was introduced to OB/GYN beginning in 19582, with early abdominal ultrasound images. These paved the way for the eventual development of equipment and scanners that could be used to locate the placenta and later conduct fetal biometry2. The technology took off through the rest of the 20th century as scientists improved upon scanning systems and probes that displayed its robust range of capabilities such as detecting placenta location, observing the heartbeat, identifying the presence of twins and monitoring high risk pregnancies. By the year 2000, medical professionals offered real-time scanning and 3D images with high resolution abdominal and endovaginal transducers2. With all of its modern capabilities, sonography is on the rise in other areas of medicine such as cardiology, emergency point of care, sports medicine and even ophthalmology.

How it Works

Ultrasound probes generally utilize piezoelectric crystalsto transmit high frequency soundwaves into the body through a transducer. Ultrasonic frequencies differ from others in that they cannot be heard by the human ear (above 20,000 Hz), with typical scanners operating in a range of 2 to 18 megahertz3. Rapidly applying and removing voltage to said crystals causes them to expand and contract, producing the ultrasonic waves. As the waves travel some are absorbed, and others are reflected back.  Modern methods use a sonar-like principle to register the pulse reflected off of the boundary between two tissues with differing acoustic resistance3. The acoustic resistance is simply the resistance to the flow of sound through a given surface. These echoes travel back to the crystal and generate a different voltage depending on the wave intensity. The transducer sends these signals to the ultrasound machine to be converted to an image.

There are four primary modes3 for scanning tissue:

  • A-mode or amplitude mode, which uses a single transducer to scan a line through the body and plot the echoes as a function of depth.
  • B-mode or 2D mode, uses a linear array of transducers (phased array) to scan a plane through the body and generate a 2D image.
  • M-mode or motion, employs a rapid sequence of B-mode scans in sequence to view range of motion.
  • Doppler mode, chiefly used to measure and visualize blood flow using the doppler effect.

Common Probe Types

Different devices tune the sound waves to focus on particular depths, either through controlled pulses from the machine or by utilizing differently shaped probes. Some common probe types include linear, curvilinear, phase array and endocavity4,5. Numerous probe types allow for diverse imaging applications:

  • Linear probes are used for imaging structures near the surface as well as vascular imaging and guided procedures. High frequency waves offer better resolution, but cannot penetrate as deep.
  • Curvilinear or convex probes use lower frequency waves in order to gain deeper penetration and have a wider field depth. They can be general purpose and are commonly used for abdominal imaging.
  • Phased Array probes have a smaller contact area and are primarily used for intercostal imaging of the liver between the ribs and for cardiac scans.
  • Endocavity or Intracavity probes are designed to image inside the body cavity and have a longer, slim design.

Challenges

Despite numerous benefits, traditional cart-based ultrasound equipment is expensive and difficult to maneuver. Ultrasound units can cost anywhere between $10,000 and $200,0006 depending on the machine, and may require more budget for additional probes and maintenance. Components such as piezoceramics tend to be expensive, though recent progress in fabrication of capacitive micromachined transducers could eventually reduce the cost as well as advance current technology 7. Another pitfall is the need for a trained operator as experience is generally necessary to obtain quality images and for making a correct diagnosis. Detailed user training courses can cost providers an additional $1000-$6000 6, consuming valuable time and resources. Portable scanners are an emerging technology targeted at addressing some of these issues. Conventional ultrasound machines require higher voltages to drive their transducers7, and early scaled-down applications struggled to compete at first. However, recent advances in computing and batteries have allowed for the development of new, smaller equipment that can image on a similar level to cart based systems.

The Benefits of Portable Ultrasound

Easy-to-use handheld ultrasound systems present a cost effective solution for diagnostic imaging on the go as well as reducing the learning curve for operators. The VistaScan software shrinks your typical carted ultrasound machine into a conveniently sized cell phone or tablet, in addition to being 20 times less expensive. This mobile health innovation makes it possible for clinicians to capture and save images and video loops at the touch of a button with choice of four different types of probes. USB probes can conveniently be swapped out to adapt to a doctor’s needs even out of the hospital or in rural areas. Those seeking a second opinion or assistance in diagnosing a patient are able to send an image through the platform and receive a diagnosis report back within minutes. By reducing the time and cost to diagnose patients, VistaScan helps people receive treatment faster and feel better sooner.

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References

[1] Amo Y, T. A, T. E. The Role of Obstetric Ultrasound in Reducing Maternal and Perinatal Mortality. Ultrasound Imaging – Medical Applications. August 2011. doi:10.5772/22847.

[2] Campbell S. A short history of sonography in obstetrics and gynaecology. Facts Views Vis Obgyn. 2013;5(3):213-29.

[3] Carovac A, Smajlovic F, Junuzovic D. Application of ultrasound in medicine. Acta Inform Med. 2011;19(3):168-71.

[4] Szabo, T. L. and Lewin, P. A. (2013), Ultrasound Transducer Selection in Clinical Imaging Practice. Journal of Ultrasound in Medicine, 32: 573-582. doi:10.7863/jum.2013.32.4.573

[5] Stanford Medicine 25. (2019). Bedside Ultrasound. [online] Available at: https://stanfordmedicine25.stanford.edu/the25/ultrasound.html [Accessed 1 Feb. 2019].

[6]Costowl.com. (2019). 2019 Average Ultrasound Machine Prices: How Much Does an Ultrasound Machine Cost?. [online] Available at: https://www.costowl.com/healthcare/healthcare-ultrasound-machine-costs.html [Accessed 1 Feb. 2019].

[7]J. M. Baran and J. G. Webster, “Design of low-cost portable ultrasound systems: Review,” 2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Minneapolis, MN, 2009, pp. 792-795. doi: 10.1109/IEMBS.2009.5332754

More than Obstetrics: 5 Unlikely Uses for Ultrasound

Today’s medical professionals have access to a variety of imaging procedures. Ultrasound is one of the more convenient methods as it doesn’t require exposing patients to radiation and provides relative freedom in movement. Because of this added safety, sonography is a preferred method for monitoring pregnancy and majorly contributed to recent developments in obstetrics. Nonetheless, obstetricians don’t have a monopoly on this expanding technology. Here are 5 other areas where its adoption proved useful:

1: Cardiology and Acute Care

Cardiovascular ultrasound provides physicians with a valuable look inside of the chest cavity as well as a look at vasculature throughout the body. Cardiac ultrasounds, or echocardiograms, produce images of heart anatomy such as valves, chambers and shed light on any abnormalities that may be present when investigating heart function. Vascular ultrasound is used to evaluate blood flow and detect blockages as well as blood clots. This is especially helpful for following up and monitoring recent recipients of stents or grafts. Echocardiograms are traditionally interpreted by a cardiologist. Recently however, the use of limited echocardiography by providers such as anesthesiologists and emergency medicine physicians is becoming more common 1 . These point of care echocardiograms are utilized by non-cardiologists along with thoracic ultrasonography to evaluate for cardiac trauma, hypotension, pneumothorax and alveolar/interstitial diseases that can lead to respiratory failure 2 . Though it cannot replace a comprehensive exam, ultrasound delivers vital supplementary information for monitoring patients and establishing diagnosis in an acute setting.

2: Radiology

In situations where a standalone PET, MRI or CT scan doesn’t afford enough scope, radiologists take advantage of an innovative technique that incorporates ultrasound to gather more data. Fusion imaging is the process in which images from the above scans are overlaid or used side by side with ultrasound images. Newer high-end software is even capable of fusing scans with live ultrasound 3 . This is advantageous for both physicians and patients because tissues can be viewed in real time and compared to findings from multiple modalities. Sonography is also a more convenient option for real time scanning compared to MRI as there’s no need to factor in things like contrast injections or worry about metal implants. With applications ranging from brain surgery and liver procedures to ultrasound guided tumor removal 3 , fusion imaging is gaining momentum in the diagnostic world.

3: Musculoskeletal Imaging

Another useful trait of sonography is that it’s the most sensitive imaging technique for assessing the extent of tendon tears 4 . This is particularly helpful in sports medicine as well as podiatry, where clinicians frequently need to evaluate injury sites and differentiate between inflammation and actual tears. Other key applications include evaluating conditions such as plantar fasciitis and determining whether an athlete has merely suffered from a muscle strain or a full on avulsion fracture 4 . In addition to visualizing muscle tissue, joints, fascia and tendons, musculoskeletal sonography assists in outlining bones. Although ultrasonic waves do not penetrate bones, they can still image features on the surface. Research even suggests that ultrasound is a feasible method for diagnosing stress fractures, particularly in the lower extremities 5 . An added trait of newer ultrasound is that more portable technologies allow evaluations to take place out of the clinic as well as assessing the function of moving parts while in use as opposed to being limited to static images.

4: Dermatology

Ultrasound is employed by dermatologists to evaluate skin conditions and adjust treatment plans. Cost is factor that inhibits dermatologists from adopting new imaging methodologies because advanced techniques such as reflectance confocal microscopy and optical coherence tomography require expensive computing systems as well as training 7 . When extreme detail isn’t necessary, skin ultrasonography serves as an economic, reliable solution for rapid examination and measurements. High frequency scanners are able to monitor detectable, irregular properties in the dermis while lower frequencies detect deeper structures such as lymph nodes and subcutaneous tumors 6 . Given these capabilities, sonography is a cost-saver for identifying inflammatory conditions such as psoriasis or looking at skin lesions and tumor thickness.

5: Handheld, Bedside Ultrasound

This final application utilizes multiple modalities. The adoption of diagnostic ultrasound is growing in the rural and developing world, and in particular, handheld, bedside ultrasound performed by clinicians 8 . This is a simple and elegant solution in regions where more expensive systems and infrastructure are difficult to access. Portable devices with abdominal, cardiac and musculoskeletal capabilities among others are making a difference where medical imaging may not have been an option previously. Sonography provides a basic diagnostic tool for a number of ailments in low and middle income countries such as tuberculosis, malaria, and ectopic pregnancy 8 . Medical professionals worldwide have taken advantage of the technology and are making a statistical impact by administering obstetrical, abdominal, cardiac, renal, pulmonary, soft tissue and vascular exams in rural areas of Africa, Asia and North America 8 . Diagnostic ultrasound is a powerful mechanism with functionality in all areas of medicine. With varying frequencies and modes, physicians from different backgrounds utilize sonography to image conditions spanning from the most superficial of ailments all the way to organ trauma and tumor identification. Its diverse capabilities and relative cost make it a tool worth having available.

References

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    2016;20(1):227. Published 2016 Aug 15. doi:10.1186/s13054-016-1399-x
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    Involving Diagnostic Ultrasound. American Journal of Roentgenology. 2013;200(3).
    doi:10.2214/ajr.12.8904
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    Annals of the New York Academy of Sciences. 2009;1154(1):171-203. doi:10.1111/j.1749-
    6632.2009.04391.x.
  5. Amoako A, Abid A, Shadiack A, Monaco R. Ultrasound-Diagnosed Tibia Stress Fracture: A
    Case Report. Clin Med Insights Arthritis Musculoskelet Disord. 2017;10:1179544117702866.
    Published 2017 Apr 10. doi:10.1177/1179544117702866
    6.Schmid-Wendtner M, Burgdorf W. Ultrasound Scanning in Dermatology. Arch Dermatol.
    2005;141(2):217–224. doi:10.1001/archderm.141.2.217
    7.Hibler B, Qi Q, Rossi A. Current state of imaging in dermatology. Seminars in Cutaneous
    Medicine and Surgery. 2016;35(1):2-8. doi:10.12788/j.sder.2016.001.
  6. Sippel S, Muruganandan K, Levine A, Shah S. Review article: Use of ultrasound in the
    developing world. Int J Emerg Med. 2011;4:72. Published 2011 Dec 7. doi:10.1186/1865-1380-
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