Ok, it is an obvious choice but there really aren't many options for X. My wife has read the alphabet mystery novels by Sue Grafton (A is for Alibi, B is for Burgler, ...) and we can't imagine any other choice from her for the letter X either.
For me, X-ray is appropriate. After blood tests, scans of all variety are the only way to really track a cancer. Each type of scan has advantages and disadvantages and every cancer has its preferred scan or sets of scans. There are a number of scans that I have gotten over the years and each works in a different way and provides different information.
X-rays are the some of the first scans that allowed doctors and others to see inside of the body without cutting. X-rays are relatively simple in action. We have all taken a flashlight and shone it through a finger, seeing the glow of the blood and, with bright enough flashlights, a bit of a shadow where the bone lies. That is exactly how an x-ray works. A beam of x-rays are directed through the body and a detector (think photo-sensitive paper), picks up the x-rays that make it through. X-rays go through skin and flesh better than through bone so x-rays are very good at identifying broken bones or the structure of the skeleton.
Computerized Tomography (CT) works similarly except that now the pictures are taken in rapid succession from 360 degrees around the body and then are fused together in a computer. This gives 3d images because then the scans are done in slices along the length of the body. Just like x-rays, the skeleton shows up well and empty spaces (lungs) show up well. Other areas of the body show up as mostly a blob with slight increases or decreases in density because of more or less water in that area. For this reason, scans are generally done using a contrast injected into the veins to give definition. This contrast then acts similar to bone, highlighting critical areas such as liver, tumor and organs.
Two similar scans that Carcinoid patients receive are the Octroscan and an MIBG scan. Both of these operate by tagging a substance with a radioactive marker. The substance used is one that is often taken up by carcinoid tumors (octreotide in the case of octreoscan and a molecule similar to noradrenaline for MIBG), tagged with either indum-111 (octreoscan) or iodine 123 (MIBG). Unlike X-rays, the tumors now become the emitters of the waves (gamma waves) that are detected by cameras that move around the body. Essentially, the tumors suck up the marker and then begin to glow due to the radioactive decay of the tag.
Positive Electron Tomography (PET) scans are not very good for carcinoid in general. These scans usually use a sugar like substance that is tagged with positron emitting radioactive agent. Since carcinoid grows relatively slowly, it does not take up sugars in large amounts and, thus, the tumors do not turn into glowing sources of positrons in the body. There are some recent trials of a new PET scan using Galium-68 but this scan requires an accelerator on location because the half life of GA68 is just 62 minutes. That means that if you started with 100 units of GA68, you would only have 50 units in about an hour, 25 units in 2hrs and 12.5 units in 3hrs, ... Since it decays so fast, the substance needs to be created just before administration of the test.
The final scan is the one I understand the least and is one that many of you have had and that is a Magnetic Resonance Imaging (MRI). MRIs operate by creating extremely strong, alternating magnetic fields that then cause the hydrogen atoms in your body to vibrate and emit radio waves. These waves are detected and, by varying the types and strengths of fields, images can be generated. Similar to a CT scan, contrast is often used since so much of your body is made of water, one sack of water (kidney) is not terribly distinct from another sack of water (liver). Contrast makes the veins glow strongly and this can then give definition to these organs.
Finally, one of the simplest and oldest scanning techniques is the ultrasounds. Ultrasounds work similar to how bats echo-locate. Sound waves are sent into the body and their reflections are detected by the emitter. By calculating the time between the wave being sent and the time it is received, a calculation of the distance can be made and an image is then generated from that calculation. Ultrasounds also can detect doper shift so they can determine what direction fluids (blood in particular) is flowing and its relative speed.
For all the scans you get, you never really know what is going on until the surgeon opens up your body. In 2011, Dr. Boudreaux got a serious surprise as the scans told him nothing of the nightmare that my abdomen was in. They give information but they cannot tell the whole story. The scans are getting better and they can greatly assist diagnosis and treatment but nothing ever is better than actually going for a hands on look.
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