Physics and the Life Sciences - 100 years of Medical Synergy

[PointRadix]

29/02/2008

Many innovations in modern medicine were developed by physicists who integrated technologies such as X rays, nuclear magnetic resonance, ultrasound, particle accelerators and radioisotope tagging and detection techniques into the medical domain. There they became magnetic resonance imaging (MRI), computerised tomography (CT) scanning, nuclear medicine, positron emission tomography (PET) scanning, and various radiotherapy treatment methods. These contributions have revolutionised medical techniques for imaging the human body and treating disease.

Medical physicists contribute to medicine in a number of ways. Some develop cutting-edge technologies in the physics laboratory, while others are certified health professionals who apply these technologies in the clinic and help diagnose illness and alleviate suffering. Virtually all hospitals have medical physicists on staff to help administer radiation therapy treatment and to ensure quality in both radiation treatment and imaging techniques. Some of the ways in which medical physics has revolutionised medicine include:

1) Using particle accelerators to defeat cancer

Once confined only to physics laboratories, linear accelerators are sophisticated high-energy machines that can deliver beams of energetic electrons or X rays to malignant tumours, at doses capable of killing cancerous cells and stopping the tumour's growth. In recent years, an advanced treatment technique called intensity-modulated radiation therapy (IMRT) has enhanced the ability of radiation to control tumours. IMRT uses computers to precisely shape the treatment field and control the accelerator beam in order to deliver an optimal dose of radiation to a tumour while minimising the doses to surrounding healthy tissues. It is already in use for treating cancers of the brain, head and neck, prostate and other malignant diseases.

2) Better detection of breast cancer

Techniques for breast imaging have undergone substantial advances since the introduction of the original film techniques. The early emulsion films were replaced with more sensitive film stocks, and finally with digital imaging. As each of these newer techniques was introduced, doses to the patient were reduced and the sensitivity of the techniques for finding early and treatable disease increased. Computer-aided diagnosis and the use of MRI and CT for breast imaging promises to further advance cancer detection and treatment. MRI breast imaging is proving particularly useful at finding growths in younger women and at earlier stages.

3) Matter / Anti-matter Collision Imaging

Another rapidly growing technique used to detect diseases is positron emission tomography (PET). This technique uses short-lived radionuclides produced in cyclotrons. These nuclides are labelled to compounds such as glucose, testosterone and amino acids to monitor physiological factors including blood flow and glucose metabolism. These images can be crucial in detecting seizures, coronary heart disease and ischemia. In cancer care PET imaging is used to detect tumours and monitor the success of treatment courses as well as detecting early recurrent disease.

The actual imaging technique involves matter and anti-matter annihilating one another. The short-lived radionuclides decay and emit particles known as positrons; the anti-matter equivalent to electrons. These positrons rapidly encounter electrons, collide, annihilate, and produce a pair of photons which move in opposite directions. These photons can be captured in special crystals and the images produced by computer systems. Other techniques, such as radioimmunoassay, use the decay of radioactive materials to study a variety of physiological conditions by imaging or chemical methods.

4) Ensuring the safety of people who get CT scans

With the intent to promote the best medical imaging practises and help ensure the health and safety of the millions of people who undergo CT scanning each year, the American Association of Physicists in Medicine (AAPM) issued a CT radiation dose management report in 2008, which recommended standardised ways of reporting doses and educating users on the latest dose reduction technology.

5) Medical Physics moments in history

Some of the greatest medical advances in the history of medicine occurred in the past century and came from the minds and laboratories of physicists including:

* X rays:
Discovered by Wilhelm Conrad Roentgen in 1895, the application of this to medical imaging was recognised and embraced immediately. When the Nobel Prizes were established in 1901, Roentgen won the first prize (in physics) for his discovery of X rays.

* Magnetic Resonance:
Felix Bloch and Edward M. Purcell shared the Nobel Prize in Physics in 1952 after discovering the phenomenon of magnetic resonance, however it took a few more decades before their discovery led to the development of MRI, which is now routinely used to image the human body. In 2003, the Nobel Prize in Physiology or Medicine was awarded to Paul Lauterbur and Peter Mansfield for their work in MRI.

* Radioimmunoassays:
In 1977, the Nobel Prize in Physiology or Medicine was awarded to Rosalyn Yalow for the development of radioimmunoassays, an extremely sensitive diagnostic technique that can quantify tiny amounts of biological substances in the body using radioactively-labelled materials.

* Computer-assisted tomography
In 1979, Allan M Cormack and Godfrey Newbold Hounsfield won the Nobel Prize in Physiology or Medicine for developing CT, which has revolutionised imaging because CT provides images with unprecedented clarity.

Source: eLab - European Laboratory Scientists Magazine