September 1, 2022
Imagine a world where you can buy a clinical-grade medical scanner for the same price as a new TV. This scanner can fit in your pocket and it plugs straight into your phone. It can accurately image any organ in your body, in real-time. The scanner’s software computes clinical measurements that can identify various conditions, even where there are no symptoms.
Moreover, you do not need to be a trained professional to use it, because this scanner comes with AI-based software. This interactively guides you to acquire the correct image and also computes clinical measurements. What would be the implications of such a device for medicine?
This scenario is not hypothetical. It is precisely the vision of handheld ultrasound manufacturers such as Butterfly Network and Caption Health, which recently launched its home-based heart ultrasound service ‘Caption Care.’ AI is the key technology here because it is AI-based applications that enable untrained individuals to acquire the correct diagnostic images.
Let’s take cardiology as a key example because heart disease is the number one killer in the West. People may be entirely asymptomatic but have treatable atherosclerosis, meaning they are not aware they are at high risk. To be sure, early treatment could save lives.
Ultrasound is a type of imaging that has been shown to be effective for detecting atherosclerosis. Therefore, having a home ultrasound device could be of great clinical value. For people who live in a country with good health care, it comes in handy because they may not seek a heart scan at the hospital if they are asymptomatic or due to cost. If they live in a country with poor access to health care, home scanning may be the only realistic option.
But cardiology is only one example. There are many more situations where home ultrasound could be potentially valuable. So, home ultrasound can be seen as a powerful instantiation of how medical AI could revolutionize medicine. Major ultrasound manufacturers are keenly watching how this area develops.
It is worth noting that the ultrasound is the only type of medical imaging feasible for home use. A CT or MRI scanner costs millions, has dangerous radioactive sources or ultra-high magnetic fields and needs a special room and a team of radiographers and technicians to operate it. Ultrasound is the only foreseeable way one could have bona fide medical imaging in the home.
Despite its potential value, home use of ultrasound is highly controversial. Some have argued that this is technology in the wrong hands and fraught with hidden dangers. The British Medical Ultrasound Society (BMUS) stated recently that “ultrasound equipment should only be used by properly trained professionals and only when an ultrasound examination is needed, either for clearly defined clinical reasons or for the training of health care professionals.” The group has been keen to point out that ultrasound involves small but real risks and therefore exposure should be “as low as reasonably achievable.”
What is the controversy? People may often assume that ultrasound scanning is risk-free, but this is not the case. Prolonged ultrasound exposure can cause bodily tissues to heat up by as much as 1.5 degrees Celsius (35 degrees Fahrenheit). Further, ultrasound exposure can cause small gas bubbles to appear in body tissue.
Moreover, there is a substantial body of literature indicating that ultrasound overexposure is associated with a range of symptoms including headaches, vertigo, fatigue and heating damage to the skin and even to the bones. Such issues must be taken seriously when considering home ultrasound use for monitoring fetal development, such as the effect of overexposure. To be sure, this issue is too new to have been properly researched. Perhaps the precautionary principle dictates that we should tread very carefully here.
This position represents a reasonable concern. The question then becomes, how far can ultrasound manufacturers go to address these kinds of concerns? Can they build in safety mechanisms to avoid or manage such dangers? How about systems to limit the number of minutes that a device can be used per day? Technically, such safety mechanisms may be very easy to implement. However, what is the risk of people trying to circumvent them? The history of medicine shows that innovations may have all sorts of unintended consequences. On the other hand, potential risks should not block all innovation.
Ultimately the degree to which such safety mechanisms can be implemented is a discussion between manufacturers and regulators. It is the hope of the manufacturers that safety features can be built into home ultrasound devices in the same way that they have been built into the kinds of defibrillators you may find outside your local convenience store or gym. In the past, a defibrillator in the wrong hands could be lethal. Now, sufficient safety mechanisms have been built into them so that their use by untrained individuals is no longer a concern.
In the context of home ultrasound, is following some precautionary principle too conservative, when the rates of preventable death are so high? This is the core of the current debate. The FDA is reviewing precisely the kinds of applications discussed here. Ultimately, this is an empirical question: The risks and benefits need to be assessed on the basis of research.