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Alzheimer’s Disease, Cancer and Antimatter – not another Black Hole!
Posted on January 9th, 2017 by Dr. Sina Ebnesajjad in New Materials & Applications
What do Alzheimer’s disease and cancer have to do with particle physics? Let’s say it has had a major impact on human health. “Matter” is made of atoms, and atoms are made of electrons and quarks exchanging photons and gluons. “Antimatter” is made of anti-atoms, and anti-atoms are made of anti-electrons (usually called positrons) and anti-quarks exchanging photons and gluons—photons and gluons being their own antiparticles. We won’t go into what protons and gluons are here.
A hydrogen atom has one electron and one proton. Logically, one could say an anti proton and a positron together should form anti-hydrogen. It turns out there is no such thing as anti-hydrogen and the universe we can observe is made of matter only. This asymmetry of matter and antimatter in the creation of the visible universe is one of the greatest unsolved problems in physics.
Let’s take the positron and leave the rest of the antimatter particles behind. An electron has a miniscule mass and a negative charge (e–). A positron has the same mass and a positive charge (e+). When an electron and a positron meet, i.e. collide, the particles are destroyed and gamma rays are produced (Figure 1). Positrons have actually entered health care through positron emission tomography, PET scan in medical lexicon. It is as one of the most powerful diagnostic tools in today’s medicine.
How A PET Scan works
To generate a PET scan a patient is given a radiotracer (radionuclide) such as fluorodeoxyglucose. Positrons are emitted by the breakdown of the radiotracer. Gamma rays are created during the emission of positrons, and the scanner then detects the gamma rays. A computer analyzes the gamma rays and uses the information to create an image map of the organ or tissue being studied.
PET scan is unique in its capability for providing information. It can often detect biochemical changes in an organ or tissue that can identify the onset of a disease process before anatomical changes related to the disease can be seen with other imaging processes, such as computerized tomography (CT) scan or Magnetic resonance imaging (MRI). PET scan is an effective way to examine the chemical activity in parts of human body. It is used to identify a variety of conditions, including some cancers, heart disease and brain disorders.
There are specific reasons for acquiring PET scans of patients. A few examples are listed here (Source: Johns Hopkins Medicine, www.hopkinsmedicine.org):
- To diagnose neurological disorders such as Alzheimer’s, Parkinson’s, Huntington’s and epilepsy..
- To locate the specific surgical site prior to surgical procedures of the brain.
- To evaluate the brain after trauma to detect hematoma (blood clot).
- To detect the spread of cancer to other parts of the body from the original cancer site.
- To evaluate the effectiveness of cancer treatment.
- To evaluate the perfusion to the myocardium (heart muscle) as an aid in determining the usefulness of a therapeutic procedure to improve blood flow to the myocardium.
- To further identify lung lesions or masses detected on chest X-ray and/or chest CT.
- To assist in the management and treatment of lung cancer by staging lesions and following the progress of lesions after treatment
- To detect recurrence of tumors earlier than with other diagnostic tools
Alzheimer’s disease (AD) is a progressive degenerative brain disorder that damages and eventually destroys brain cells, leading to memory loss and changes in thinking and other brain functions. It has no current cure. Only the symptoms can be treated to slow down the progress of the disease. The Alzheimer’s Association reports 5.4 million Americans are currently affected by AD, expected to rise to 16 million by 2050 (Source: Alzheimer’s Association, www.ALZ.com). By mid-21st century, every 33 seconds someone in the US will de diagnosed with AD. In addition to human suffering the costs associated with AD are staggering; the total cost in 2016 to be US $240 billion.
Current diagnosis of Alzheimer’s disease relies largely on documenting mental decline. CT and MRI of the brain are used to rule out other conditions that may generate similar symptoms to AD. Alzheimer disease has already caused severe brain damage in individuals by the time they are diagnosed. Post mortem autopsies have revealed the presence of a plaque on the brain of the patients accompanies with dead cells and lost tissues.
The plaque is comprised of insoluble deposits of an apparently toxic protein peptide, or fragment, called beta-amyloid. Amyloid plaques were first described by Dr. Alois Alzheimer in 1906 and are found in the spaces between the brain’s nerve cells (Source: National Institutes on Aging, www.nia.nih.gov). In a healthy brain beta-amyloids are swept out. They build up in the brain due to aging but more rapidly in case of Alzheimer patients forming the plaque on the brain surface. Scientists are not absolutely sure what causes brain cell death and tissue loss in a brain afflicted with Alzheimer’s brain, but plaque is one of the prime suspects.
Researchers have long strived to discover an easy and accurate way to detect Alzheimer’s brain, in living patients, before these devastating symptoms begin. Experts believe that biomarkers (short for “biological markers”) offer one of the most promising paths. A biomarker is something that can be measured to accurately and reliably indicate the presence of disease. Several potential biomarkers are being studied for their ability to indicate early stages of Alzheimer’s disease. One of the biomarkers being studied is beta-amyloids.
Detection of AD by PET Scan
In 2012, the U.S. Food and Drug Administration approved the first molecular imaging biomarker for use in patients being evaluated for possible Alzheimer’s disease or other causes of cognitive decline. This biomarker (florbetapir F-18) is a molecule that binds to beta-amyloid in the brain. Because it is labeled with a radioactive tracer (fluorine isotope) it can be visualized during a positron emission tomography (PET) brain scan (Figure 2), thereby revealing the presence of amyloid plaques in the brains of living patients (Source: Alzheimer’s Association, www.ALZ.com).
Figure 2 Beta-amyloid brain PET imaging with Flutemetamol: the image on the left is a normal brain image, the image on the right shows a brain with Alzheimer’s (Source: GE Healthcare, http://gereports.com.au)
Scientists at the Stanford University School of Medicine have shown how a protein fragment known as beta-amyloid, strongly implicated in Alzheimer’s disease, begins destroying synapses before it clumps into plaques that lead to nerve cell death. “Our discovery suggests that Alzheimer’s disease starts to manifest long before plaque formation becomes evident,” said Dr. Carla Shatz, professor of neurobiology and of biology and senior author of a study, published in Sept. 20, 2013 issue of Science (source: Bruce Goldman, https://med.stanford.edu and http://science.sciencemag.org).
Beta-amyloid begins life as a solitary molecule but tends to bunch up – initially into small clusters that are still soluble and can travel freely in the brain, and finally into the plaques that are found in the brain of an AD patient. The study showed for the first time that in this clustered form, beta-amyloid can bind strongly to a receptor on nerve cells, setting in motion an intercellular process that erodes their synapses with other nerve cells.
Positron emission tomography holds great promise by providing doctors with a diagnostic tool for Alzheimer’s disease, when proven. PET would then provide physicians and patients early positive diagnosis of AD. That would allow early treatment of the symptoms far in advance of the presentation of full-fledged disease. Hopefully drug development research will lead to therapies to cure this disease. Early affirmative diagnosis of Alzheimer’s disease would be highly beneficial even before cures have been discovered.
How delicious, the positron, a little particle from the antimatter realm, is helping medicine take a giant leap forward. It would be worth all the research funds invested in particle physics just to reduce the human pain and grief of Alzheimer’s disease. The icing on the cake is saving hundreds of billions of dollars of cost to society.
All opinions shared in this post are the author’s own.
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Dr. Sina Ebnesajjad
President at FluoroConsultants Group, LLC