Ultrasound has been a vital component of medical imaging since the 1950s, but like all imaging technology, it looks quite different today than it did when first clinically applied. The M-mode, one-dimensional images we relied on in the 70s have been replaced with 3D and even 4D images that are so life-like, mothers and fathers often feel they already know what their child looks like before it’s even born. This is only the beginning.
Ultrasound has matured into an imaging technique with an ever-expanding number of applications. Not only can we image any part of the body that allows for sound penetration, but there are even techniques to image bones for fractures using high-frequency transducers—a realm typically allocated to the penetrating photons of X-ray. Below are several additional examples of how this more than 60-year-old technology is still breaking with convention.
The chest X-ray, a staple for diagnosing pneumonia, has been widely used since the beginning of the last century. It is easily accessible, and has relatively low inter-user variation. However, in children where ionizing radiation is used sparingly, ultrasound can be an excellent alternative with low biophysical impact. While certain parts of the body cannot transduce sound waves adequately—such as air-filled lungs—consolidated lungs filled with fluid and infection, like those of a child battling pneumonia, are excellent mediums for transmission.
Ultrasound has actually been shown to be effective as a diagnostic modality for pediatric pneumonia with a reported sensitivity and specificity of 96 percent and 93 percent respectively.* The challenge with using ultrasound for diagnosing pediatric pneumonia is that it requires skilled users to achieve such a high diagnostic yield (see the prior post on using a robot as a “skilled sonographer”!). Even with this limitation, in the right setting, ultrasound shows promise to supplant the conventional chest X-ray.
The uses of ultrasound are always surprising, but some of the most intriguing research is in the field of therapeutic ultrasound. High-intensity focused ultrasound for the non-invasive treatment of uterine fibroids is currently among the most developed uses of therapeutic ultrasound, but there are many other interesting niche applications being pursued. For example, ultrasound is increasingly used to aid in modulation of intracranial delivery of medication and gene therapy. The blood-brain barrier, a natural mechanism to keep some circulating components in the blood separate from the intracranial spaces, can also act as a barrier limiting drug delivery to the brain. Focused ultrasound energy can transiently open the blood-brain barrier, allowing drug delivery. Combining this technique with MRI guidance, ultrasound can be focused to very specific anatomic regions of the brain that would benefit from localized drug delivery. This technique has shown some success for gene therapy delivery to the parts of the brain affected by Parkinson’s disease.
One of the most amazing aspects of advancing technologies is how we are able to improve quality of life. In healthcare, technology has brought bench top laboratory work to the patient, and as time goes on, what are now considered the most advanced technologies—like some of these highly innovative uses of ultrasound—will become more portable, affordable and accessible, helping to bring world-class healthcare to the entire world.
*Mead, B. P., Kim, N., Miller, G. W., Hodges, D., Mastorakos, P., Klibanov, A. L., … & Price, R. J. (2017). Novel focused ultrasound gene therapy approach non-invasively restores dopaminergic neuron function in a rat Parkinson’s disease model. Nano Letters.
