Dr. Sidarius, our Radiologist in Nuc Med, allowed me to shadow him for a morning to see what a Radiologist generally does. There weren't a lot of interesting cases that morning but I was able to see how he interacted with regular patients. It was interesting to see how he interacted with patients and his own professional work discipline. I watched how Dr. Sidarius kept a positive attitude during the day and when he explained the scan results to the patients. A large amount of his work with patients is reassuring them that things are ok, even if the results were not the best. It seems emotionally exhausting having to constantly maintain a positive attitude when one has to deal with the emotional and physical problems of patients. It was during this week when the fact struck me, that almost everyone coming in has cancer or is a cancer survivor. It makes me wonder about the fear and stress that the patients are experiencing.
There was a patient that recently had a skin tumor removed. Dr. Sidarius was going to inject a radioisotope to determine if there was any contamination of the lymph nodes. If there was, then those lymph nodes would have to be removed and the patient might have to receive a whole body scan to make sure that the cancer has not metastasized. The patient told me how teenagers are not mentally mature enough to realize the importance of sunscreen and how when they reach 40 years old they will regret it. I nodded my head in agreement.
Dr. Sidarius told me that the radiation dosage absorbed by radioisotopes is much less than the dosage absorbed by CT or X-ray scans. This surprised me because I was under the assumption that they had somewhat similar absorbed dosages. He explained to me how SPECT-CT and PET-CT scans provide more information than regular CT scans. For example, you can see on a CT-scan that, after therapy, a tumor may have the same mass and size prior to therapy. But in a PET-CT, the radiologist could say that although the mass and size may be the same, it is all dead tissue, and the tumor is not functional. The difference between PET-CT and SPECT-CT is the radioisotope used. PET-CT uses smaller isotopes such as Oxygen 15 (which is made by smashing a Deuteron with a Nitrogen-14 in a fusion reaction). Oxygen 15 gives off a positron which will interact with a free electron and combine, releasing gamma radiation in two directions. The PET machine then calculates the exact location by analyzing the distance traveled by the gamma rays.
I asked Dr. Sidarius, that if PET-CT and SPECT-CT are so effective and radioisotopes do less damage than CT-Scans, then why is there not a huge shift to PET and SPECT-CT? The reason seems to boil down to jobs and money. There are also various schools of thought in Medical Imaging and some of the "old-timers" are adamant about using CT-scans and measuring the millimeter change in anything. I am told that the next big step in Medical Imaging is a PET-MRI. The PET-MRI will get rid of the CT portion of the scan, and thus minimize the amount of radiation absorbed. I get the feeling that the CT-scan is a brute force scan like getting hosed, while Radioisotopes and MRI are more of a finesse scan.
I was also told how Iodine chemotherapy works. The body is dosed with TSH, which forces thyroid cells to take up Iodine. If there is any metastasis of thyroid cells, they will also absorb TSH. The patient then will take in 60-200 mCi (that's a lot) of Iodine-131. Iodine-131 will then damage the thyroid cell's functions beyond repair, thus preventing the thyroid cells from ever absorbing Iodine again and never producing Thyroid hormones. There are a lot of regulations regarding how the patient should act after the therapy (they are a literal walking source of radiation). The patient should not stand within 6ft of another person for extended periods of time to prevent the destruction of the other person's thyroid gland. The patient should also go to the bathroom and drink water every hour to prevent the accumulation of I-131 in the urine system (about 40% of the I-131 dose is absorbed by the thyroid gland).
In the afternoon, I got to see the Therasphere injection for a patient with Hepatocellular Carcinoma (Liver Cancer). Mr. McCormick got me set up with Dr. Woods to watch the "operation". My assumptions about Therasphere chemotherapy are not exactly correct. Therasphere, Yttrium-90, is actually sometimes the first treatment people opt for to combat their liver cancer. Also, the SIR-sphere, which causes clots, is actually not the optimal therapy. Dr. Woods says that he prefers the cancer get some oxygen. The reason is that the chemical reaction to destroy the DNA requires oxygen, and for radiation to actually kill tumors, it needs to rip and damage the DNA to the extent that the cells cannot replicate. This type of therapy can only be used on the Liver because the liver has a dual blood supply: the portal vein and it's artery. The veins of all the organs in the abdomen group up to fuse into the portal vein which will then go to the liver, which provides a little oxygen. Dr. Woods says that the portal vein is the reason why doctors can abuse the Liver's artery so much.
The actual Intravenous Radiology room for the "operation" is very amazing. I wish I could have taken a picture but it is not allowed because of HIPAA laws and the patient is in the room. There is a giant screen hanging from the ceiling next to the operating table which shows the live X-ray images. There is a blippy wave reading thing for reading the patient's heart rate and stuff (I have no idea what to call it). There are enormous rails on the ceiling for the CT-scanner and camera.
So something like this =
The previous guidelines to Therasphere therapy is 120Gy (Grey which is radiation/Volume (my interpretation)) for the whole one side of a liver. Now, there is a new way using Radiation Segmentectomy. This is concentrating the theraspheres to the area of the tumor. So instead of the whole part of the liver, it will go to the 1/4 where the tumors are. Dr. Woods would bring up the radiation dose to the tumor to 200Gy which is basically enough to kill anything. So part of the liver is dead, but at least so is the cancer. The problem with previous guidelines is that there would be some cancer cells left in the Liver which would require other therapies. There are a bunch of articles and research done on Radiation Segmentectomy which surprised me. I would think that something like changing the procedure by a little would not matter a lot, but it seems that any change in guidelines requires a lot of experiment and research. It goes to show how advance and secure the medical guidelines are.
On Friday, I had a sudden revelation watching the histogram of a patient. The histogram shows the amount of gamma rays detected and the strength of the rays. I can compare the patient's histogram to the pure source and then calculate the difference between the two. Unfortunately the machine only picks up rays that are parallel to the tubes in the detectors so I will have to take that into account. This means going back to learning manifolds (Much to Mrs. Bailey's Delight).
It also appears that Cell Division rates bring up different results on Google than Mitotic rates (Makes no sense to me... Must be the connotations *sigh* ). Mr. McCormick was about to bring up statistics about the turn over rates in less than 15 minutes whereas it took me about 2 hours of fruitless research to come up with nothing. I now know that I will be narrowing my research down to the radiation absorption rates and chance of cancer in epithelial tissue (skin and the guts in the abdominal area). There is an article talking about how "bad luck" influences cancer rates. I have not read too much into it, but it seems that 60-80% of cancer is generated by "bad luck". This does not mean that 60-80% of cancer rates are coincidental; multiple factors cause cancer. Also, the majority of cancer develops from stem cells in the body. I did not know this at all but apparently it is common knowledge in the medical field. Because Stem Cells are similar to being "blueprints", if they are mutated, the chance of it getting out of control increases by an enormous amount. This makes me think about Stem-Cell research and if those stem cells are more susceptible to cancer. Because the mitotic rates might be different and the surrounding cells might cause some changes (I am thinking of the sheep clone, Dolly, where it developed some sort of cancer while it was young. I think my correlation is off though).
I was going to attach my 3 page rant on Healthcare, American Society, the Middle Class, and International policy as well but it seems like this blog post is already dense and grueling enough. So see you guys next time!
Last thing : I keep on underestimating the human body! I got to watch an injected radioisotope in real time move through the aorta and to the arteries and back to the heart within 30 seconds.
