Rick Robinson

Oct 25th 2019

X-Ray Alternative Tools Include Sound, Light, Terahertz Radiation


X-rays are an important medical tool, but as useful as they are, they have one serious complication: X-rays involve exposure to potentially dangerous high-energy radiation. This poses a problem for patients who cannot risk radiation exposure.

X-ray alternative technologies include ultrasounds, visible light techniques and terahertz radiation.


As the National Center for Biotechnology Information (NCBI) explains, X-rays allow medical professionals to “look through” the human body. Soft body tissues allow X-rays to pass through freely and appear dark on exposed X-ray films. Dense portions of the body, such as bones and teeth, block X-rays and show up as white on X-ray films.

Pregnant women are at risk of X-ray dangers and are almost never given X-rays because of the vulnerability of fetal tissues to radiation, says NCBI. While a small amount of radiation may not cause harm, Mayo Clinic notes, “If you received a large number of abdominal X-rays over a short period before you were aware of your pregnancy, your baby could be affected.”

Instead, ultrasounds — the most familiar X-ray alternative — are used in pregnancy examinations. But the usefulness of ultrasound is not limited to expectant mothers.

A study recorded in Emergency Nurse found ultrasound to be as effective as X-rays for detecting minor bone fractures. Ultrasounds can be used without the restrictions that apply to X-rays. Moreover, operators do not require as much specialized (and costly) training, says TechRadar.

While ultrasound is the most established and widespread X-ray alternative, other technologies are also showing promise, ranging from ordinary visible light to so-called terahertz radiation, intermediate between radio and infrared light.

Visible Light

We think of opaque materials, such as human tissue, as simply blocking all ordinary light, but as Engadget reports, this is not entirely true. Light can indeed penetrate human tissue. (You can see a hint of this by holding your hand close — but not too close — to a bright light bulb.)

The problem is that light passing through human tissue is so scattered that it is useless for creating an ordinary photographic image. But scientists borrowed a technique called adaptive optics from astronomy, where it is used to cancel out the effects of atmospheric turbulence. The borrowed technology, says Engadget, was “surprisingly effective” in imaging tissue, holding out promise for using ordinary light to image the body.

Terahertz Radiation

Like both X-rays and visible light (but unlike ultrasound) terahertz radiation is part of the electromagnetic spectrum. It is shorter than microwaves, but longer than infrared light. The Journal of Applied Physics notes that “THz radiation does not ionize molecules, presenting a significant advantage in medical imaging over X-rays, which can cause biological molecules to break down.”

Science Daily reports that large molecules, of the sort commonly found in drugs, explosives and living tissues, naturally vibrate at about the same rate as terahertz radiation. These molecules show up readily in terahertz spectral analysis, producing “fingerprints” that, as notes, can be identified and used for tasks ranging from medical examination to airport baggage inspection.

The use of X-rays is unlikely to disappear any time soon. But the range of emerging alternative technologies suggest that new imaging options that avoid X-ray dangers will soon become standard tools in areas ranging from medicine to security.