SRP Week 6 : Books made of Papers

It has been quite a while since my last post! A lot of events have transpired since then but thanks for sticking with me so far~!

A major resource that I have found at Banner is it's medical library. When I first entered it, I thought it was just a small room with a single shelf of books to the side and computers at the far end. Turns out the single shelf of books are just reference books if the doctors need an immediate source (some chapters have more than 200 references... ). The majority of books are stored in the section called the "Stacks" (so cool!!! the name that is [I'm pretty sure that's a generic name but oh well]. Reminds me of Name of the Wind). The Stacks is pretty much a giant collection of journals, textbooks and a few novels. Some of these books are older than I am!

I initially searched for something related to the genetic component of gastronomy. I wanted to find a specific organ that I could use to calculate the dose absorption and was wondering how various sections developed cancer. Although I did find a few books, they were very difficult to read. Initially it took me about 15 minutes to read a single page because I had to search up every single word I didn't know (and there were a lot) and the background to the term. Eventually I realized that most of the information that I was looking for is close to the end. The passages of medical journals seem to be similar to mathematical proofs except instead of numbers, there are words. I've decided to stick with the liver at the moment because of my previous interaction with the theraspheres.

I've grown particularly fond of scientific magazines, especially Nature and Science. When I read these magazines, I feel as though I am part of an elite group of people who can read scientific articles. I am sure this hubris will eventually come back to bite me in a posterior area. There was an article in Nature that particularly interested me titled "MTH1 inhibition eradicates cancer by preventing sanitation of the dNTP pool"(the article only has MTH and NTP capitalized...). I have an extremely vague idea what the article is saying and can only grasp at a few important things (thank goodness I can understand a professional scientific abstract (I now know why abstracts are so important)). But pretty much it talks about dNTP pools which are the building blocks of nucleic acids and how they are oxidized which mess up the DNA chains (super shortened explanation).

Pretty much all I am saying is that there are dozens of factors (like Protein Kinase Inhibitors) that I have probably not taken into account. I can only probably attempt to find the possible number of mutations.

While I knew that multiple codons coded for the same amino acid, I did not take them into account. Although I found molecular biology fascinating, the amount of variables that codon usage bias would introduce would destroy my brain. Masatoshi Nei why you do this to meeeeeee (I spent a whole day just reading up on molecular biology literature even though I have no use for genetic evolution).

Another factor that I did not think of when analyzing dose absorption is the breathing patterns of the body. Because your body continually moves with each breath cycle, the exposure rates start to differ (basically your body is constantly moving and the dose absorbed changes with that). Although the change in the amount of dose absorbed is probably very small, it should not be completely ignored. In medical imaging, they have ways to get around breathing cycles by doing gate-controlled imaging (I think that's what it's called). And there is something called manifold learning which is an automated program/algorithm that balances out the image/data. So when you add in breathing into your image, you get into 4D imaging (so cool right?) and apparently it can go up to 6D imaging if you take into account all of the factors (I don't have a great idea on how that works).

Manifold learning : (I imagine this is what it looks like?...)

I have slowly been able to read research papers (although most of it has too much context for me to make head or toes of it). There was one discussing the development of making new organic compounds (I understood about 2/50 of the reactions) and another having a heated debate over catalysis (catalysis = the increasing of the rate of a chemical reaction)\(apparently the exact reaction of catalysis has not been agreed on yet?)). (People can calculate the number of electron transfers to palladium? cool)

I have found the exact copy of the article discussing the bad luck factor in cancer rates (reference week 3). What it is actually discussing is the possibility of genetic corruption based upon stem cell replication. The data from the actual article was somewhat lacking and only provided a few graphs discussing log 10 values. But perhaps I can gleam a little more from the references the authors use.

My current favorite book in the library is On Being a Doctor 2. It provides great stories and insight into the world of patients and doctors. In addition, it addresses multiple viewpoints and beliefs.

Well thanks for reading! Until next time!

SRP Week 5 : Dosimetry

It seems hard to believe that it has been 5 weeks since our 2nd trimester has ended. I never thought I would say this, but I truly do sometimes miss school. I have been trying to continue learning by reading books and watching videos, but it feels so different from learning at school. I keep on expecting a period change to a new class or 5 minute breaks between every 50 minutes of reading to talk to somebody. It feels like I am studying 60+ hours for an exam that I am never going to take.

Recently I have been trying to relearn Chinese. I never really did try hard at Chinese School and my parents told me I would regret it when I was older. I truly feel the brunt of that pressure now (Feeling regret and I'm only 18 years old). I have tried to dabble a little in Japanese and Korean. My friend Sonya tells me that Japanese is easier than Korean and she occasionally helps me with my pronunciation. I walk around in my backyard saying "are" or "arigatou" or "wakaranai" and the occasional "cake" (Japanese "cake" is different from the English version where the "a" is more like an elongated "e". To me, it sounds like k-ee-k-i which is still probably wrong). Sonya says that, if I can learn the R/L sound, I can sound less foreign and possibly surprise someone.

I have been finishing up the second book that Mr. McCormick has given me. The title is Physics in Nuclear Medicine. I tried to learn by osmosis, but that never seems to work. Dr. Deng says that Radiobiology for the Radiologist is the so-called bible for the physicist and radiologists, I might check that book out sometime. The good thing about Physics in Nuclear Medicine (and probably any good medical book) is that it has a whole bibliography section after every chapter. I can look up the individual articles/books that it mentions and find even more details. It has has a whole 6 pages of tables, telling me the S-values of the entire human body for different radionuclides. That will help immensely in my calculations. It feels too basic if I do a Dosimetry of the epithelial tissue and internal organs with the given values by the book. I will probably also do a comparison of the histograms in the database with a scan from a Phantom (I need Mr. McCormick to do it because I can't touch the radionuclides in the hot lab).

I have a better understanding of why CT and x-ray have a growth in the amount of radiation dosage. In general for all medical imaging, the amount of exposure has decreased. The only exception is CT. The reason is that even with the amount of technological improvements, CT requires more dosage to improve image quality. So when they do a chest CT with contrast, they have to increase the dosage to have a good image of the blood vessels in the chest. There has been a big debate between using a chest CT with contrast or a VQ nuclear medicine scan. There are good arguments on both sides, but a big factor is that many doctors are comfortable with looking at CT-images. Even though a VQ can give around 90% probability and some additional details, doctors are afraid of the remaining 10% of uncertainty.

Although there is probably a 1-2 difference in mSv (milli Sievert) between CT and Radionuclides, it is the amount of CT's used by the hospital that makes the difference. Say a patient comes into the Emergency room with chest pain and wants to talk to a physician. By the time the patient talks to a physician, there is no more chest pain. The physician is pretty sure that the patient has no issues. But because the hospital does not want to be sued in case the patient does, the physician tells the patient to have a CT scan done. CT is so convenient, cheap, accurate, and efficient, physicians can tell patients to get one anytime. If a doctor doesn't have the images yet because of paperwork, he can just tell the patient to take another one and it will be done in 5 minutes.

Physics in Nuclear Medicine says that immediate radiation is much more damaging than prolonged radiation. I do not know if the effective radiation dose takes into account the different types of radiation, but if you compare the time difference between a Nuclear Medicine scan and a CT scan, the CT scan dose is probably quicker by factors of 10.

I am slowly getting the hang of the concept of radiation usage. By next week, I hope to have a calculated model of an internal organ, such as the stomach (that seems like an important organ to BASIS kids).

Mata ne! (See you later!)

Phillip Yang

SRP Week 4 : Locked On

I am constantly reminded of the complexity and precision of the medical field and its administration. It took me a while to see how researchers and doctors systemically carve away new discovers and modify procedures and guidelines. But in order to keep this sort of complexity, there is division of labor and specialization. I think I am ranting about social structure now, my apologies.

It feels as though every new idea I have has already been done by someone else or a government agency. My initial idea was to use manifolds to determine tissue structure and calculate the probability of irradiation. Turns out, the International Commission on Radiological Protection (ICRP) has already calculated out the risk factors for different types of tissues. The unit of Sieverts is an actual measure of health effect on different types of tissues. The information about the effective radiation dosage (Sieverts) is found easily on the internet.

Effective radiation dosage gives a good general idea about the possibility of adverse effects caused by radiation with different types of scans. The issue is that nature of each scan differ from each other and the risk changes per individual. Generally, Computed Tomography (CT) and x-ray will affect the superficial parts of your body: the skin and some tissue below that. Radioisotopes are more spread around the interior of the body because it is injected intravenously.

You would think that Radioisotopes would be more harmful because it is entering the interior of the body where everything is more vulnerable. It is true in some aspects, but the radioisotopes will be in your blood flow for a little while before it is taken up by the organs. The main source of irradiation from radioisotopes is where they accumulate. Eventually your body will remove the radioisotopes through the digestive and urinary systems. Your digestive and urinary systems are actually very hardy and already receive damage from stomach acids and bodily wastes. There might be some lingering fears about radioisotopes going to sensitive areas of the body like the brain. The thing is, radionuclides are different from CT and x-ray because it gives off radiation over time, unlike the direct hit from CT. So for the initial hour the radionuclides are in your body, the amount of radiation absorbed is actually small and generally insignificant. Assuming that your body takes about 6-10 hours to process and excrete wastes, the radioisotope is in your blood stream (entire body) for about an hour, where it will then decrease as it is taken up by the targeted organ for while and then excreted in another few hours. The amount of concentration when it is in the blood stream is minimal and it is only when radionuclides enters the targeted organ or digestive/urinary systems that there is enough concentration and radiation to be significant.

Aside from all that technical stuff, I got to visit Banner's Radiation Oncology. Oncology is involved with treatment of cancer and they use radiation to solve the problems. I was shown around by Dr. Hanny, Dr. Deng, and Ms. Mickie, medical physicists who work in Radiation Oncology. A big part of cancer treatment in Radiation Oncology is Stereotatic Body Radiation Therapy (SBRT). This is basically surgery using radiation.

In SBRT, the people are using linear accelerators to slam electrons/protons into your body. The Mayo Clinic in Phoenix is currently constructing their proton accelerator building (sidenote). In x-ray and CT, most of the radiation is absorbed by the skin and superficial tissues. By changing the x-ray used, the payload can be deposited deeper into the body. Although the skin will absorb a chunk of it, most will go through towards the target. Then it is the precise obliteration of the tumor (I am romanticizing this too much I think). To be more in-depth, it is not the radiation that is actually destroying the cells. The electrons/protons shot from the linear accelerator (nearly at the speed of light), will interact with the atoms to generate x-rays. The x-rays, with oxygen (O2) and water (H2O), will generate a hydroxyl radical (OH free radical). The hydroxyl radical is highly attracted to DNA, which will then disrupt the structure of the DNA. Because SBRT is 7000 times stronger than CT, destruction is assured (I am totally blowing this out of proportion).

Hydroxyl Radical damage to Guanine :

Linear Accelerator :

The planning of SBRT to irradiate a brain tumor. The physicists need to construct a plan prior to irradiation. They will try to spread out the dosage over a large area of skin. This is because several shots of 7000rem will destroy the skin as well. So if you spread it out over a large area, the dose given to the skin is much lower. Sometimes hitting sensitive structures is inevitable, and the doctors will have to decide the tradeoff. There is always a tradeoff in SBRT, because there is a splash spreading effect of radiation as well. Basically, in an exaggerated situation (probably unlikely but this is what it is like), the doctor has to decide to irradiate your eyes, giving you a 25% chance of getting cataracts, or your Cochlea in your ear, which might lead to hearing loss. The program (the amount of programming that goes into medical programs is so impressive) will do a hundred iterations after the physicist puts in base values. Then there is the fine tuning of the plan where the doctor decides if the values are acceptable.

Cancer cells have a different radiation toleration compared to regular cells because of their irregular growth and structure. This gives a small gap where you can destroy a major portion of the cancer cells at the cost of some normal cells : 

Please feel free to ask lots of questions. After 2 hours in Radiation Oncology I ran out of questions to ask and I felt completely incompetent. Asking good questions is a very difficult skill to master.

Until Next Time! 

-Phillip Yang