Medical Imaging: Invisible rays make us see

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It just happened one day

Scientists were beginning to discover existence of invisible rays towards the end of 19th century. Physicists of the day, Humphry Davy, Micheal Faraday, Hemholtz and Lenard were all experimenting on properties of cathode rays. Nikola Tesla had also noted in 1894 that invisible rays affect photographic plates. On 8th November 1895 while experimenting on Cathode rays, Wilhelm Roentgen, a German physicist, discovered that these rays could pass through objects. He immersed himself in follow up experiments, and on 28th December 1895 reported existence of what he called “X-rays”. By this time, he had obtained first radiologic imaging, an X-ray of hand of his wife Anna Ludwig, who was also wearing her wedding ring at that time.

Aftermath

Scientific world was livid with excitement. The newspapers reported discovery of X-rays on 5th January 1896. We had entered the world of medical imaging. We obtained numerous X-rays of humans, insects and reptiles in the same year. Scientists developed fluoroscope in the same year, and obtained live images. In 1896, medical journals published as many as 1000 scientific articles. Roentgen was awarded the first Nobel Prize in 1901.

In the early years, we did not know dose, duration of exposure, and adverse effects of X-rays. Between 1896-1989, scientists reported cases of radiation dermatitis. Radiation led to cancers, and by 1903 we knew about such malignancies. Yet, despite these adverse effects, use of these rays extended beyond science and medicine, to motion pictures and even fitting of shoes. Roentgen never patented his discovery, and this helped early widespread use of this technological advance.

Other invisible rays

In 1895, the year of discovery of X-rays, Marie (Skłodowska)Curie graduated in Physics and married to Pierre Curie. Next year, in 1896 Henri Becquerel discovered invisible penetrating rays from Uranium. Marie and her husband Pierre started their research on spontaneously emitting rays, and discovered radioactivity. In 1903, the Nobel committee jointly awarded Nobel prize to Marie, Pierre, and Becquerel.

Pierre died in 1906, and Marie continued her academic pursuits. She discovered Radium and Polonium. This earned her a second Nobel Prize in 1911. During First World War, Marie Curie helped establish Red-Cross Radiology. Armies established Mobile X-ray units, and called them “petites Curies“.

One of the uses of radioactivity was in treatment of Cancer. Excess radioactivity would itself cause cancers, and blood disorders. Curie developed Aplstic anemia, and died in 1934, aged 66. Like Roentgen, Curie also refrained from patenting her discoveries. Both of them believed in making science available to all.

More invisible rays of medical importance : Ultrasound, CT scans and MRI

Ultrasound and doppler are based on invisible acoustic waves and their reflections. This technique was introduced in a big way in medical imaging after 1960s.

CT scans use rotating X-ray technology, and this invention in 1972 earned Cormack and Hounsfield, Nobel Prize in 1979.

MRI was developed shortly after by Damadian, Mansfield and Lauterbur in 1978. Today, in addition to conventional radiography, CT scans and MRI are cornerstone of image based diagnostics. Together these invisible rays make us see lesions, hidden deep inside vital organs.

Great Britain issued a four stamp series in 1994 on USG, CT , MRI and scanning electron microscopy. While later is not part of medical imaging as yet, it is also performed by a beam of invisible electrons. This beam is reflected by the surface atoms, and gives information about surface topography of microscopic proportions.

There are distinct clinical branches that deal with medical use ion these invisible rays. Radiodiagnosis, Radiotherapy, and Nuclear Medicine. Various sub-specialties have emerged from these three, and the current century will be one of advances in medical imaging.

In addition these invisible rays are used productively in nuclear physics, metallurgy, power generation. There is a constant struggle to eliminate its use from warfare, something humanity is still waiting for.