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Ten ways physics has enhanced the medical field

From antimatter to X-rays, here’s how physics helps keep us healthy.

When Albert Einstein postulated his general theory of relativity, he was trying to figure out how the universe worked. He couldn’t have foreseen that, decades later, the principles would play a key role in GPS satellites, enabling millions of people to navigate around the globe.

Physics is full of such stories. While physicists are often motivated by pure curiosity, the knowledge they uncover eventually finds practical applications in chemistry, materials science, computer science, and more. Even today, in the midst of a global pandemic, physicists are contributing in unexpected ways, from exploring the role of causal models in assessing COVID-19 responses to helping create simple, much-needed ventilators.

Here, we look at some physics principles that have enhanced medical diagnostics and treatments.

While antimatter might sound like science fiction, it’s very real – and very useful. To image tissue and organs with a positron emission tomography (PET) scan, radioactive isotopes are attached to a material, like sugar, which gathers in cells that use more energy, such as cancer cells. The isotopes decay, producing positrons – the antimatter partner of electrons. When the positrons encounter electrons, they annihilate and produce radiation that can be imaged.

Quantum mechanics says that some particles have a property called “spin.” Magnetic resonance imaging (MRI) uses a strong magnetic field to nudge the spins of protons into alignment. An applied radio pulse causes some protons to absorb energy and change their spin alignment. As they fall back into line, the protons release that energy, which the MRI sensors detect.

Particle accelerators help physicists crack the secrets of the quantum world. But did you know they also treat cancer? Intensity-modulated radiation therapy uses a type of particle accelerator called a linear accelerator, or LINAC. It collides electrons to produce high-energy X-rays, which are guided to precisely target a patient’s tumour.

Ventilators regulate breathing, a process that relies on a difference in pressure between the atmosphere and the lungs. Early ventilators, like the iron lung, created a negative pressure around the chest. Today’s machines instead raise the pressure in a patient’s airway.

The unique quantum properties of lasers – focused light of one colour, with all the waves moving together in phase – make them useful across the medical field. They’re used in place of scalpels for surgery, to vaporize blockages in arteries, to detect cancerous growths, and more. Zap!

Technically, we all heart physics: your heart beats thanks to an electrical stimulus generated by the heart’s sinus node. An electrocardiogram (ECG) machine measures the tiny electrical changes with each heartbeat, graphing voltage over time to map out abnormalities.

When high-frequency sound waves are pulsed into the human body, they are reflected at various tissue boundaries. The waves are turned into a two-dimensional ultrasound image, or sonogram. The sound waves can also be used in treatments, such as breaking up kidney stones, killing cancer cells, and guiding drug delivery. Sounds good!

Astronomers developed adaptive optics as a method of smoothing out the effects of Earth’s atmosphere on distant starlight by using a deformable mirror to correct the image. Now, the technique is being applied to biological systems. For instance, adaptive optics can correct for turbulence in eye fluid to produce a clear image of the retina.

Many pharmaceutical drugs work by inhibiting enzymes (proteins that catalyze chemical reactions in cells). Researchers are currently seeking a deeper understanding of the physics of atomic motions within enzymes, which could lead to entirely new classes of pharmaceuticals.

Discovered in 1895 by Wilhelm Roentgen, X-rays are a type of light with high energy and a very short wavelength – too short to be seen with our eyes. They pass through most soft tissue, like fat and muscle, but are absorbed by dense material, such as bone, allowing us to obtain internal images without invasive procedures.



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