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Particle Accelerators, Radioisotopes, Antimatter, and Medicine

In my last blog, I mentioned I would include four topics in this weeks blog:
First, my plan for this blog. Second, the tracers for PET scans, in particular fluorine-18 tracers Third my answer to my prompt from last week Forth, a new prompt. I will do these topics in this order.


I am starting my next semester on the 16th of January. My courses will be Biology 196, Environmental Science 206, Math 286, and Chemistry 402.
After todays blog, my plan is to post every week during the weekend (somewhere from Friday to Sunday) with a real world application of a topic from one of these courses for the next 17 weeks, starting next week (the weekend prior to the beginning of the semester). It is likely that I will post later in the weekend, but early-weekend posts are possible.


Now, as promised, the tracers used for PET scans. PET scans are positron emission tomography, which makes a three-dimensional mapping of the functional processes of one aspect of the body, typically the brain. It takes advantage of the pair of gamma rays observed from the emission of positrons from a compound containing a radioisotope.
As a side note, positrons are antimatter. They are anti-electron particles, which, when they collide with electrons, completely annihilate to form energy in the form of the previously mentioned gamma-ray pair. This alone is not particularly harmful, and it can be easily seen when we apply the most famous equation in the world; Einsteins' . When we plug in the mass for an electron and a positron (both having the same mass of 9.11*10^(-31) kg), we get E=8.8188*10^(-14) Joules or 1.96*10^(-17) Calories. We breathe more energy than that with every breath, so it's not really enough to do any damage at all.
The radioisotope commonly used for the tracer for PET scans is fluorine-18. The main reason for this is a timing issue. All radioisotopes which could theoretically be used for a tracer have half-lives. This is a term used for all radioactive atoms, which is the time it takes for half of the materials to radioactively decay. It is an exponential decay curve, which means after the first half-life, half of the radioactive material is remaining; after two half-lives, a quarter is remaining; after three half-lives, one-eighth is remaining and so on. Of all of the radioisotopes viable for PET scan tracers, Fluorine-18 has the longest half-life, making it's use the best for time purposes.
Since fluorine-18 is a radioisotope – and therefore has a half-life and decays – it cannot be stockpiled. So it has to be created via a cyclotron, which is a small particle accelerator. Think of a very scaled down version of the Large Hadron Collider, used not for destroying matter for study, but rather making matter for a practical purpose, matter which is normally not readily available for use. Fluorine-18 is created by bombarding a proton against an Oxygen-18 labeled water molecule, which can only be done in these small scale accelerators.
It used to be that we were restricted by old school reactions to form aryl fluorides suitable for human consumption that will not be chemically harmful, but as reported in the 04NOV2011 issue of Science Magazine, there has been significant research to develop an reaction which will be more suitable for radiochemistry. These reactions are used to create the aryl fluorides which are then used to create the fluorocarbohydrates (carbohydrates with one of the hydrogens on the ring replaced by fluorine-18) used for the tracers.
For those of you who are unaware of what reactions are, this stands for Dimolecular Nucleophilic Substitution Reaction. The substitution part refers to reactions which one group of one molecule and one group from the other molecule switch molecules. The dimolecular part means the rate of the reaction is dependent on the concentration of both reactants. The nucleoplhilic part means that the “minor” reactant (the one that can be thrown away afterwards) is attracted to the nucleus of an atom as opposed to the electrons.
The major downfall of Fluorine-18 is that it's half-life is 110 minutes, which means it needs to be created, put into the final tracer state, put into the patient, and the PET scan completed relatively quickly. This is the reason why research of chemistry of fluorine-18 is being done; so as to lessen the time the reaction part takes away from the total process.
And the research shows a lot of success. The experiments seem to be highly repeatable and consistently procure high yields of aryl fluorides with fluorine-18. It looks good that pretty soon, this process will become the most common process to use for creating tracers for PET scans. Hopefully this will decrease the production cost of tracers, thusly decreasing the cost for the PET scan procedure for patients.


As far as my answer to last weeks prompts, with how my brain works, I have not completed it. I've begun it, but my realm of existence is pretty complex right now, and my brain works very scientifically meticulous, so I am far from complete with the prompt. I may have it finished by next week.
This weeks prompt is biochemical in nature. Think of a way you can improve your emotional state, your physical state, or how you view yourself through easily accessible biochemical processes, including (but not limited to) change in diet, alterations in breathing habits, increase in exercise, alteration of medication intake, etc. Think of all the ways in which you can improve your emotional state as stated above through means you have at your disposal. If you are confused on what I mean by biochemical means, I will refer you to my youtube videos on the Basics of Chemistry (The Basics of Chemistry 1 and The Basics of Chemistry 2). I hope that helps in this prompt.
Until next Friday, have a great week and DFTBA!

Take that as you will.
-K. “Alan” Eister Δαβ


References:
Research for F-18:
Periodical: Science Magazine
Issue 04NOV2011
Title: “A Fluoride-Derived Electrophilic Late-Stage Fluorination Reagent for PET Imaging”
Lead Author: Eunsung Lee
Other Authors:Adam S. Kamlet, David C Powers, Constanze N. Neumann, Gregory B. Boursalian, Takeru Furuya, Daniel C. Choi, Jacob M. Hooker, and Tobias Ritter.
Pages: 639-642
Videos for Prompt:
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