Using radioactive drugs to see inside your body - Pedro Brugarolas - video Dailymotion

TED-Ed

Investigate the science behind how doctors use radioactive drugs and PET scans to detect and diagnose diseases like Alzheimer’s and cancer.  --  Is there a way to detect diseases like cancer and Alzheimer’s before they advance too far? Doctors are using injected radioactive drugs that circulate through the body and act as a beacon for PET scanners. These diagnostic tools can detect the spread of diseases before they can be spotted with other types of imaging. So how exactly does this work, and is it safe? Pedro Brugarolas investigates.  Lesson by Pedro Brugarolas, directed by Artrake Studio.

Transcript

00:00This syringe contains a radioactive form of glucose known as FDG.

00:14The doctor will soon inject its contents into her patient's arm,

00:18whom she's testing for cancer using a PET scanner.

00:21The FDG will quickly circulate through his body.

00:24If he has a tumor, cancer cells within it

00:27will take up a significant portion of the FDG,

00:30which will act as a beacon for the scanner.

00:33Pet tracers such as FDG are among the most remarkable tools in medical diagnostics,

00:39and their life begins in a particle accelerator, just hours earlier.

00:45The particle accelerator in question is called a cyclotron,

00:48and it's often housed in a bunker within hospitals.

00:51It uses electromagnetic fields to propel charged particles like protons

00:57faster and faster along a spiraling path.

01:00When the protons reach their maximum speed, they shoot out onto a target.

01:05That contains a few milliliters of a type of water with a heavy form of oxygen,

01:10called Oxygen 18.

01:12When a proton slams into one of these heavier oxygen atoms,

01:16it kicks out another subatomic particle called a neutron.

01:20This impact turns Oxygen 18 into Fluorine 18,

01:24a radioactive isotope that can be detected on a PET scan.

01:28In a little under two hours,

01:30about half the fluorine will be gone due to radioactive decay,

01:34so the clock is ticking to get the scan done.

01:37So how can Fluorine 18 be used to detect diseases?

01:41Radiochemists at the hospital can use a series of chemical reactions

01:45to attach the radioactive fluorine to different molecules creating radiotracers.

01:52The identity of the tracer depends on what doctors want to observe.

01:56FDG is a common one because the rate at which cells consume glucose

02:00can signal the presence of cancer, the location of an infection,

02:04or the slowing brain function of dementia.

02:07The FDG is now ready for the patient's scan.

02:11When a radio-labeled tracer enters the body,

02:14it travels through the circulatory system and gets taken up by its target,

02:18whether that's a protein in the brain, cancer cells, or otherwise.

02:22Within a few minutes,

02:24a significant amount of the tracer has found its way to the target area,

02:28and the rest has cleared from circulation.

02:30Now the doctors can see their target using a PET,

02:33or positron emission tomography, scanner.

02:37The radiation that the tracer emits

02:40is what makes this possible.

02:41The isotopes used in PET decay by positron emission.

02:46Positrons are essentially electrons with positive charge.

02:50When emitted, a positron collides with an electron from another molecule in its surroundings.

02:56This causes a tiny nuclear reaction,

02:59in which the mass of the two particles is converted into two high-energy photons,

03:04similar to X-rays, that shoot out in opposite directions.

03:08These photons will then impact an array of paired radiation detectors in the scanner walls.

03:15The software in the scanner uses those detectors to estimate where inside the body the collision occurred,

03:21and create a 3D map of the tracer's distribution.

03:25PET scans can detect the spread of cancer before it can be spotted with other types of imaging.

03:31They're also revolutionizing the diagnosis of Alzheimer's disease by allowing doctors to see amyloid,

03:37the tell-tale protein buildup that otherwise couldn't be confirmed without an autopsy.

03:43Meanwhile, researchers are actively working to develop new tracers,

03:47and expand the possibilities of what PET scans can be used for.

03:51But with all this talk of radiation and nuclear reactions inside the body,

03:56are these scans safe?

03:57Even though no amount of ionizing radiation is completely safe,

04:01the amount of radiation the body receives during a PET scan is actually quite low.

04:06One scan is comparable to what you're exposed to over two or three years from natural radioactive sources,

04:12like radon gas,

04:13or the amount a pilot would rack up from cosmic radiation after 20 to 30 transatlantic flights.

04:20Most patients feel that those risks are acceptable for the chance to diagnose and treat their illnesses.

04:27If you think scanning the human body is as fascinating as we do, check out this lesson.

04:32Otherwise, here's a playlist on other fascinating technologies that'll spark your curiosity.

04:43I'll see you next time.

04:45Bye.

Using radioactive drugs to see inside your body - Pedro Brugarolas

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