30. Radiation Dose, Dosimetry, and Background Radiation

MIT 22.01 Introduction to Nuclear Engineering and Ionizing Radiation, Fall 2016
Instructor: Michael Short
View the complete course: ocw.mit.edu/22-01F16
TH-cam Playlist: • MIT 22.01 Introduction...
Units of radiation dose to biological organisms are introduced and demystified (there are many, but they are all related). Methods of measuring dose are introduced, as well as measuring dose by different types of radiation. The difference between dose (energy absorbed per unit mass) and damage (dose times effectiveness of radiation at causing cellular defects) is specifically introduced. Ways of using ionizing radiation for medical treatment (brachytherapy, diagnostics, x-ray and proton cancer therapy) are explained from a physical point of view. Prof. Short explains how his uncle very intelligently used principles of ionizing radiation and mass attenuation to smuggle diamonds out from Apartheid South Africa.
License: Creative Commons BY-NC-SA
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[@mitocw]

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[@fjs1111]

Thank you MIT + Michael Short

[@diwitdharpatitripathi7427]

Building relationship as well as the friendship with the students. By the highly learned scholars of the school. Learning and teaching going side by side.

[@mohamedsakr5253]

Dear prof.
Thanking you very much for your valuable and informative course

[@ruyrayol9757]

One small correction: LET is equal to the collision factor of stopping power, or the restricted stopping power, not the total stopping power. Remember, Total SP = Collision SP + Radiation SP.
Great class! You can see perfectly the enjoyment in this teacher's eye when he talks about this subject.

[@fernandamagalhaes8871]

i agree :)

[@lucasmatta8503]

You can say that again!!
Did you see it in Attix? Great book

[@amirouchebouremani1213]

Plz can you more explication

[@ruyrayol9757]

@@amirouchebouremani1213, sure! LET is the Linear Energy Transfer, so, by that, you can understand that the particle gives energy to the medium through its trajectory. Mathematically, you can understand it as -dE/dX (the sign is negative because we consider the energy loss), and you can remember that this is the stopping power. However, we are not considering the total stopping power, but a restricted stopping power. The restricted stopping power is the mean energy loss per unit length thickness due to
collisions involving energy transfers, that are smaller than some chosen cut-off energy, denoted by greek capital letter delta. Here's where we have to consider the two components for the total stopping power, as I said in the comment, the radiative SP and the collision SP. If you have any more questions, I'll be happy to answer them!

[@mohamedsakr5253]

Dear prof. First thanking you very much for your excellent job. Second, please be notified that the tissue weighting factors are changed to a new values I will try to send you the website include them in my next message.

[@lsofia1871]

this was super interesting!! thank you for posting

[@diwitdharpatitripathi7427]

Teaching someone, or anyone is not just a simple office job, or business entrepreneur. It's about building a new future, better than the previous ones.

[@chadr2604]

We had to watch a safety video they had a guy I think he worked for Halliburton put a Cs137 source in his back pocket and walked around all day. It burned a chunk out of his rear end.

[@MohammadAliShafaei]

excellent

[@fisikmedik5003]

Could I have the PDF of the presentation?

[@peraperic1325]

Except LET is absolutely NOT the same thing as the stopping power. S=-dE/dx. It takes into consideration all mechanisms by which the initial beam of intensity I weakens, while LET=+dEabs/dx, that is, the part of ABSORBED energy per unit distance. It takes into account only the part of energy that is absorbed by the material.
In the example of Compton scattering the gamma ray for instance can knock out an orbital electron and change direction. The total intensity will decrease, but the gamma photon will not be absorbed by that atom.

[@diwitdharpatitripathi7427]

Radiation and ionization

[@joro8604]

This guy is brillIant, MIT is the real deal, and I am a moron.

[@Yodavid1]

if the stopping power of neutrons decreases because the cross section goes down after the resonances, how come that very same stopping power is low for low energies, when the cross section is way up?
shouldn't the stopping power follow the same trend we see in the cross section graph? high for low neutron energy and low for high energy?

[@foffjerkholes4995]

With neutrons, whether fast or slow spectrum beam. Regardless of the beams velocity, when you speaking of Neutrons specifically, the speed at which the travel and come into contact with a surface that you are targeting. I have professors explain it to me like this, think of using a grenade in the army against enemy forces. Some fighters can throw and hit you with that grenade really fast, some people don't have those quick pitching skills. In the analogy I'm using is why Neutron radiation is deadly no matter their speed. You as a human on the battle field are not at all worried about the grenade hitting you, that's why if your quick enough you might have time to through it back. With neutrons it is much the same thing, mammalian cells (you, me, other critters of the world, heck even plants for that reason are not worried about the ACTUAL NEUTRON HITTING YOU, fast or slow because it won't hurt you. HOWEVER, neutrons have an eight minute or so half life so when a short period of time goes by and the Neutron begins to decay, a single neutron, if I remember correctly absolutely BLASTS OUT HIGH ENERGY GAMMA AND BETA radiation that no living tissue on Earth has been found to have a tolerance to it. So, its like the soldier in combat analogy thing again, you are not worried about the grenade hitting you, BUT YOU ARE AFRAID WHEN IT BLOWS UP IN 20 SECONDS TO RELEASE ALL OF THAT ENERGY, killing you and maybe several of your squad. I can't remember the site I saw this type of thing, but it was a small science demonstration on the power of a single neutron held in safety chamber and you can actually see many beautiful little lights appear in the chamber. Very beautiful, but when you realize you are just witnessing just the release of energy of a single neutron decay that is even possible to be scene with the naked eye, which I believe you know how really small protons and neutrons are compared to us, you realize a neutron releases an astronomical amount of energy in the form of visible light we can see with our eyes, electron scopes or any of that jazz, just all of that energy in a single neutron releasing so much power, you can see it in plane sight, is just awe inspiring and frightening at the same time. If that single were to gather with many other neutrons and make a gram of the stuff, your talking a twenty, forty, heck 60 mile drive away might not be able to get you away from energy released in that first decay of a gram of neutrons. I can say with the utmost happiness that Neutrons love to stick to Protons that utilize the "strong nuclear force" to keep them nice and stable. On a side note, it's probably for the best that they do in fact "almost" always stay in the nucleus of the atom because of their nature if any bad actors try to make, I don't know, some sci-fi device for city destruction, that the neutron will be more than happy to horrifically irradiate anyone without many physicists, the best equipment, and facilities that can more or less harmlessly keep them from crazy people and uneducated people from trying to think of a way to use them for nefarious purposes. It's be safer to cover your self in gasoline and smoke a cigarette than try to make use of it.

[@tagumiraabudallah6538]

thank you for that information but how can i convert from μsv/h to ngy/h

[@marcosanaya9540]

micro to nano? then sievert to gray including Q.

[@daveb5041]

*If diamonds are round little things and money is flat, wouldnt they see a bunch of dots that would show up in a square of plastic? I would think you would need to grind up the diamonds and lay them flat over the money* Confused.

[@paulgush]

In point of fact, Jews weren't persecuted in Apartheid South Africa. Everyone, regardless of ethnicity, was limited to taking a very small amount of money out of the country.
Nevertheless, great lecture series!

[@diwitdharpatitripathi7427]

Radiation dosimetry

[@hezu2013]

FCKING EPIC

[@mohamedsakr5253]

Please be notified that the tissue weighting factors are changed. I sent you the website includes these changes. God bless you.

[@diwitdharpatitripathi7427]

MIT.

[@mikepalin1333]

Listen at 75% play back and he definitely sounds half cut

[@diwitdharpatitripathi7427]

Massachusetts Institute of technology.

[@diwitdharpatitripathi7427]

Diamond smuggling

[@diwitdharpatitripathi7427]

Diamond

[@no-de3lg]

Is this youtube channel official for the mit college for high iq people or not the same mit

[@stdesy]

It is the official MIT (their OpenCourseWare program), and the channel for everyone but you might like it more if you are a high IQ person

[@no-de3lg]

@@stdesy i like it since im in radiology college

[@marialiyubman]

That was such a Jewish story 😂
(Israeli Jew, don’t kill me).

[@pavelboico9283]

As a medical specialist should say that a lot of medical stuff is incorrect

[@monstaincity8219]

Dissipate

[@monstaincity8219]

Smuggle

[@monstaincity8219]

Muggle

[@amirouchebouremani1213]

Hello 🤗🤗🤗🤗

[@dwaynerobinson6494]

Watch Hidden Colors 1, 2, 3, 4 and 5 by Tariq Nasheed.