Breaking Bad | Season 4 | Episode 8 | “Hermanos”
While Walt continues to exude low-level stress, the characters around him take decisive action to keep events moving along the way they want them to. In this post, I’ll be talking about medical imaging.
Looking inside the body
The “loud one with the magnets” is almost certainly a MRI (magnetic resonance imaging) scanner. The noise is actually caused by the superconducting magnetic coils expanding and contracting due to the changing magnetic fields between them.
Walt and his luckless interlocuter are scheduled for a combination PET (positron emission tomography) – CT (X-ray computed tomography) scan. These techniques are often performed at the same time, because PET gives biochemical information (what biological processes are happening in the body) while CT gives anatomical information (what biological structures are present). Together, it is possible to see which process are occurring in which areas of the body, in three dimensions. PET can also be combined with MRI for similar results, but the information is not quite as accurate (PET and CT can be performed with the same machine in sequence, whereas PET and MRI use different detection processes and therefore require separate machines or a complicated and expensive combination instrument).
A CT scan is essentially several (2-dimensional) X-ray “slices” taken around an axis of rotation and then processed to give a 3-D image, almost like assembling a 3-D cake from lots of almost-2-D slices.
A PET scan works on an extremely elegant principle, and can be performed on the same instrument as a CT scan because it uses gamma rays (which are similar to X-rays and hence can be detected with similar apparatus). A short-lived radioactive isotope is introduced into the patient, usually into the blood and usually attached to a biologically-active molecule of interest. This isotope undergoes radioactive decay by emitting positrons (the antimatter equivalent of electrons). When a positron encounters an electron, which is pretty much immediately, the two particles annihilate and produce a pair of gamma rays. These rays are emitted in opposite directions, and reach the detector at almost exactly the same time. By taking the detection events that occur in pairs, looking at where on the ring-shaped detector they hit and applying knowledge of the speed of light, it is possible to calculate exactly where in the body they were emitted. The information from millions of annihilation/detection events is used to build up a 3-D model of where the radioisotope is in the body, and hence where the biologically-active molecule is going.
Walt mentions beryl, garnet, black tourmaline and morganite (a variety of beryl). His slightly self-effacing description of them is fairly accurate as far as I know; too bad Hank didn’t give him more warning about where they were really going.
Elements in the credits
|Steven MicHael Quezada||Hydrogen|
|Michael ShAmus Wiles||Americium|
|StewArt A. Lyons||Argon|