ISF Logo   IS Forum
Forum Index Register Members List Events Mark Forums Read Help

Go Back   International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology
 


Welcome to the International Skeptics Forum, where we discuss skepticism, critical thinking, the paranormal and science in a friendly but lively way. You are currently viewing the forum as a guest, which means you are missing out on discussing matters that are of interest to you. Please consider registering so you can gain full use of the forum features and interact with other Members. Registration is simple, fast and free! Click here to register today.
Reply
Old 31st July 2019, 12:36 PM   #1
JeanTate
Master Poster
 
Join Date: Nov 2014
Posts: 2,736
SBRT - what is the wavelength of the radiation?

As in Stereotactic Body Radiation Therapy, used to kill the cancer cells in small-ish tumors. It's a pretty amazing application of technology, designed to deliver pretty lethal doses of radiation to the tumors themselves while delivering less-than-lethal doses to surrounding tissues, as little as mm away.

The heart of the various machines (there are at least two manufacturers with big market share) is a lineac, a linear accelerator (of electrons). In striking a target inside the machine, the electrons produce a quite narrow beam of photons.

But what is the wavelength of those photons?

Some sources say it's "x-rays", some that it's gamma radiation. But no source that I've been able to find says what the wavelength (or, more likely, wavelength range) acutally is!

Yes, you can find the radiation dosage (in greys), and even mention of energies (of the beam), in kV and (sometimes) MV.

To be clear, there is no precise definition of the boundary between x-rays and gammas, and different branches of physics (and related fields, e.g. astronomy) seem to use different definitions. But in all you can fairly easily get values for the wavelength(s) being studied (OK, the units are not all that friendly; Angstroms (0.1nm, a unit of distance) and keV/MeV (a unit of energy) are both used, but at least there's no trouble converting them).

Maybe you, dear reader, have better DDG-foo than I have?
JeanTate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 02:25 PM   #2
casebro
Penultimate Amazing
 
casebro's Avatar
 
Join Date: Jun 2005
Posts: 16,680
AKA Gamma knife?

They have been using X-ray on tumors for what, nearly a century? Whatever it is now, it's better it was 20 years ago.

Now go get your radiation treatments and quit whining.
__________________
Great minds discuss ideas.
Medium minds discuss events.
Small minds spend all their time on U-Tube and Facebook.
casebro is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 02:41 PM   #3
JeanTate
Master Poster
 
Join Date: Nov 2014
Posts: 2,736
Originally Posted by casebro View Post
AKA Gamma knife?
Sorta.

Quote:
They have been using X-ray on tumors for what, nearly a century?
Probably closer to a half century.

Quote:
Whatever it is now, it's better it was 20 years ago.
One would certainly hope so!

Quote:
Now go get your radiation treatments and quit whining.
Been there, done that, got the T-shirt.

So, you donít know what the wavelength (range) of the radiation used in SBRT is?
JeanTate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 02:54 PM   #4
RecoveringYuppy
Philosopher
 
Join Date: Nov 2006
Posts: 8,978
Originally Posted by JeanTate View Post
Yes, you can find the radiation dosage (in greys), and even mention of energies (of the beam), in kV and (sometimes) MV.
V or eV? If you have an eV for photon energy cite you can calculate wavelength from that.
__________________
REJ (Robert E Jones) posting anonymously under my real name for 30 years.

Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.
RecoveringYuppy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 03:16 PM   #5
Thor 2
Philosopher
 
Thor 2's Avatar
 
Join Date: May 2016
Location: Brisbane, Aust.
Posts: 5,311
Originally Posted by JeanTate View Post
As in Stereotactic Body Radiation Therapy, used to kill the cancer cells in small-ish tumors. It's a pretty amazing application of technology, designed to deliver pretty lethal doses of radiation to the tumors themselves while delivering less-than-lethal doses to surrounding tissues, as little as mm away.

The heart of the various machines (there are at least two manufacturers with big market share) is a lineac, a linear accelerator (of electrons). In striking a target inside the machine, the electrons produce a quite narrow beam of photons.

But what is the wavelength of those photons?
Sorry I can't help you with your question Jean. I have a question that has niggled away at me for some time about Radiation Therapy and perhaps you, or someone else, can help me with it.

As you mention the treatment delivers - "pretty lethal doses of radiation to the tumours themselves while delivering less-than-lethal doses to surrounding tissues, as little as mm away." - which is quite impressive.

What I can't understand however, is the effect on tissues along the path of the beam, to and from the tumour. I was wondering if there was more than one beam, and they intersected at the tumour, thus giving a concentrated dose just there?
__________________
Thinking is a faith hazard.
Thor 2 is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 03:19 PM   #6
RecoveringYuppy
Philosopher
 
Join Date: Nov 2006
Posts: 8,978
Yes, 201 beams in the most advanced versions. Probably a dozen for the specific device JeanTate is referring to.
__________________
REJ (Robert E Jones) posting anonymously under my real name for 30 years.

Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.

Last edited by RecoveringYuppy; 31st July 2019 at 03:23 PM.
RecoveringYuppy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 03:29 PM   #7
Tanalia
Scholar
 
Join Date: Apr 2012
Posts: 80
From Wiki: External beam radiotherapy it says the linear accelerators used will typically run from about 4 to maybe 25 MeV, so about 3 picometer and smaller wavelengths.

Generally, Gamma ray is the name given to high-energy EM radiation produced from radioactive decay, which have narrow spectral lines (dependent on the source), while X-ray is EM produced by bremsstrahlung (rapid deceleration of charged particles, such as an electron beam striking a tungsten target), which have a wide, continuous spectrum. Other than that, plus the energy range for X-rays going much lower (often called soft X-rays), they are essentially the same, so the confusion in usages is understandable. Most people probably just use whichever term they are more familiar with when referring to high-energy EM.

Last edited by Tanalia; 31st July 2019 at 05:23 PM. Reason: slipped a decimal cobverting to wavelength
Tanalia is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 04:14 PM   #8
Thor 2
Philosopher
 
Thor 2's Avatar
 
Join Date: May 2016
Location: Brisbane, Aust.
Posts: 5,311
Originally Posted by Thor 2 View Post
Sorry I can't help you with your question Jean. I have a question that has niggled away at me for some time about Radiation Therapy and perhaps you, or someone else, can help me with it.

As you mention the treatment delivers - "pretty lethal doses of radiation to the tumours themselves while delivering less-than-lethal doses to surrounding tissues, as little as mm away." - which is quite impressive.

What I can't understand however, is the effect on tissues along the path of the beam, to and from the tumour. I was wondering if there was more than one beam, and they intersected at the tumour, thus giving a concentrated dose just there?
Originally Posted by RecoveringYuppy View Post
Yes, 201 beams in the most advanced versions. Probably a dozen for the specific device JeanTate is referring to.

Thanks for that ...... I did suspect that was the case.

The accuracy of the beams must be extraordinary however when you have so many hitting the right spot.
__________________
Thinking is a faith hazard.
Thor 2 is online now   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 04:16 PM   #9
JeanTate
Master Poster
 
Join Date: Nov 2014
Posts: 2,736
Originally Posted by RecoveringYuppy View Post
V or eV? If you have an eV for photon energy cite you can calculate wavelength from that.
V, never eV. That would have been easy, as you say, and Iíd have not written this!
JeanTate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 04:29 PM   #10
JeanTate
Master Poster
 
Join Date: Nov 2014
Posts: 2,736
Originally Posted by Thor 2 View Post
Sorry I can't help you with your question Jean. I have a question that has niggled away at me for some time about Radiation Therapy and perhaps you, or someone else, can help me with it.

As you mention the treatment delivers - "pretty lethal doses of radiation to the tumours themselves while delivering less-than-lethal doses to surrounding tissues, as little as mm away." - which is quite impressive.

What I can't understand however, is the effect on tissues along the path of the beam, to and from the tumour. I was wondering if there was more than one beam, and they intersected at the tumour, thus giving a concentrated dose just there?
If you dig into this (SBRT), youíll learn that itís pretty amazing.

Not only does the whole linear accelerator rotate about the patient, but the beam can be sent in different directions and its intensity modulated. Perhaps the coolest is that the setup tracks your breathing, and moves the beam to keep on target. And thereís all sorts of cool stuff about locating the tumors for each session.

Of course, there certainly is collateral damage; for sure youíll get radiation burns, etc. The technique aims to minimize this collateral damage, but it is unavoidable, especially as you want to be sure to kill all the cells in the tumor.
JeanTate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 04:31 PM   #11
JeanTate
Master Poster
 
Join Date: Nov 2014
Posts: 2,736
Originally Posted by Tanalia View Post
From Wiki: External beam radiotherapy it says the linear accelerators used will typically run from about 4 to maybe 25 MeV, so about 1/3 picometer and smaller wavelengths.

Generally, Gamma ray is the name given to high-energy EM radiation produced from radioactive decay, which have narrow spectral lines (dependent on the source), while X-ray is EM produced by bremsstrahlung (rapid deceleration of charged particles, such as an electron beam striking a tungsten target), which have a wide, continuous spectrum. Other than that, plus the energy range for X-rays going much lower (often called soft X-rays), they are essentially the same, so the confusion in usages is understandable. Most people probably just use whichever term they are more familiar with when referring to high-energy EM.
Thanks!
JeanTate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 04:31 PM   #12
RecoveringYuppy
Philosopher
 
Join Date: Nov 2006
Posts: 8,978
Quote:
V, never eV. That would have been easy, as you say, and Iíd have not written this!

Yeah, though that would be easy for you. But what attribute is being reporting in V that doesn't automatically give you eV, an estimate at least.
__________________
REJ (Robert E Jones) posting anonymously under my real name for 30 years.

Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.
RecoveringYuppy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 04:36 PM   #13
JeanTate
Master Poster
 
Join Date: Nov 2014
Posts: 2,736
Originally Posted by RecoveringYuppy View Post
Yeah, though that would be easy for you. But what attribute is being reporting in V that doesn't automatically give you eV, an estimate at least.
Iím not entirely sure ... I think it has to do with the energy of the electrons in the accelerator, or the voltage driving it; I donít think I came across a source where it was obviously referring to the photons.
JeanTate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 04:56 PM   #14
RecoveringYuppy
Philosopher
 
Join Date: Nov 2006
Posts: 8,978
Energy of the electron bounds the energy of the photons. I would think that would a good approximation for curiosity sake.
__________________
REJ (Robert E Jones) posting anonymously under my real name for 30 years.

Make a fire for a man and you keep him warm for a day. Set him on fire and you keep him warm for the rest of his life.
RecoveringYuppy is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 31st July 2019, 05:25 PM   #15
JeanTate
Master Poster
 
Join Date: Nov 2014
Posts: 2,736
Originally Posted by RecoveringYuppy View Post
Energy of the electron bounds the energy of the photons. I would think that would a good approximation for curiosity sake.
The link Tanalia posted has some good stuff on this; it turns out it is a good OOM (order of magnitude) approximation, but the details are pretty interesting.
JeanTate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st August 2019, 04:34 AM   #16
elgarak
Illuminator
 
elgarak's Avatar
 
Join Date: Nov 2003
Posts: 4,388
Originally Posted by JeanTate View Post
V, never eV. That would have been easy, as you say, and Iíd have not written this!
Doesn't matter. If you know the V, you know the eV (or at least have an upper limit). That's why physicists came up with the unit eV!
elgarak is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st August 2019, 06:05 AM   #17
JeanTate
Master Poster
 
Join Date: Nov 2014
Posts: 2,736
Originally Posted by elgarak View Post
Doesn't matter. If you know the V, you know the eV (or at least have an upper limit). That's why physicists came up with the unit eV!
If the reference was clear, and clearly referred to photons, then yes.

However, the sources I found were, in general, a) not clear, b) unclearly were referring to something other than photons, and c) more-than-sometimes mixed in references to dose. And, as the link Tanalia makes clear, 1 MV electrons produce photons of less than 1 MeV (on average).
JeanTate is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st August 2019, 08:38 AM   #18
CORed
Philosopher
 
Join Date: Dec 2008
Location: Central City, Colorado, USA
Posts: 8,928
Originally Posted by RecoveringYuppy View Post
Yes, 201 beams in the most advanced versions. Probably a dozen for the specific device JeanTate is referring to.
I have a vague recollection that some treatments (used to?) work by rotating the patient, as if on a rotisserie, with the rotation being centered on the tumor. Multiple beams, of course, would be much more comfortable for the patient, but likely make the equipment considerably more expensive.
CORed is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st August 2019, 08:58 AM   #19
Mikemcc
Graduate Poster
 
Join Date: Dec 2009
Location: UK
Posts: 1,787
Watched the recent Horizon about the two new Proton Beam Therapy centres being constructed. Very impressive bits of kit. From the look of it alot of the kit is very similar to the stuff I saw and worked on at Diamond Light Source. But I suppose one particle beam accelerator will use very similar kit to another one!
Mikemcc is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 1st August 2019, 10:07 AM   #20
casebro
Penultimate Amazing
 
casebro's Avatar
 
Join Date: Jun 2005
Posts: 16,680
Jean Tate, why would the difference be important?
__________________
Great minds discuss ideas.
Medium minds discuss events.
Small minds spend all their time on U-Tube and Facebook.
casebro is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 5th August 2019, 08:55 AM   #21
casebro
Penultimate Amazing
 
casebro's Avatar
 
Join Date: Jun 2005
Posts: 16,680
I read up on SBRT a bit. Apparently SBRT is an umbrella term, actual treatments might be gamma, xray, or proton. Each uses a totally different machine with a different tech to generate the different beams.

Jean, you may be able to look up the clinic where the treatment is/was done, they will only have one machine, they will brag about having the Binford 6000- ar-ar-ar.
__________________
Great minds discuss ideas.
Medium minds discuss events.
Small minds spend all their time on U-Tube and Facebook.
casebro is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 5th August 2019, 12:54 PM   #22
ponderingturtle
Orthogonal Vector
 
ponderingturtle's Avatar
 
Join Date: Jul 2006
Posts: 47,162
Originally Posted by RecoveringYuppy View Post
Yeah, though that would be easy for you. But what attribute is being reporting in V that doesn't automatically give you eV, an estimate at least.
If it is a proton beam being accelerated by many volts? But yea with an electron beam V and eV should be interchangeable.
__________________
Sufficiently advanced Woo is indistinguishable from Parody
"There shall be no *poofing* in science" Paul C. Anagnostopoulos
Force ***** on reasons back" Ben Franklin
ponderingturtle is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 5th August 2019, 05:32 PM   #23
elgarak
Illuminator
 
elgarak's Avatar
 
Join Date: Nov 2003
Posts: 4,388
Originally Posted by ponderingturtle View Post
If it is a proton beam being accelerated by many volts? But yea with an electron beam V and eV should be interchangeable.
For a proton, too. You still get the kinetic energy directly as eV when it is accelerated with that many Vs. Proton still has a charge of 1 e, after all.
elgarak is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 6th August 2019, 03:54 AM   #24
ponderingturtle
Orthogonal Vector
 
ponderingturtle's Avatar
 
Join Date: Jul 2006
Posts: 47,162
Originally Posted by elgarak View Post
For a proton, too. You still get the kinetic energy directly as eV when it is accelerated with that many Vs. Proton still has a charge of 1 e, after all.
Yea but I figured its lower/longer acceleration from higher rest mass might change things. But its been a long time since I did any of that math.
__________________
Sufficiently advanced Woo is indistinguishable from Parody
"There shall be no *poofing* in science" Paul C. Anagnostopoulos
Force ***** on reasons back" Ben Franklin
ponderingturtle is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 6th August 2019, 05:40 AM   #25
elgarak
Illuminator
 
elgarak's Avatar
 
Join Date: Nov 2003
Posts: 4,388
Re-reading the OP, as a physicist, I just have to say this: I do not care about wavelength. My training has me taught to think in eV. As long as I get eV, i'm happy, and I don't give a crap what word they use for different region of the EM spectrum (hard or soft x-rays? That's so quaint and ill-defined – I do not give a crap anymore.)

As long as it is clear what is referred to and what goes actually into the body (photons, electrons, protons, ions). So I probably could help you more if you give me a link to a document you have a problem with. I know that often those documents are written by physicists who have no idea how to talk to non-physicists (sometimes we physicist do not know how to talk to each other...), and translated by people who do not know anything about physics, often resulting in great sounding techno-babble with little more information than toilet paper.
elgarak is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 6th August 2019, 06:41 AM   #26
casebro
Penultimate Amazing
 
casebro's Avatar
 
Join Date: Jun 2005
Posts: 16,680
Originally Posted by elgarak View Post
Re-reading the OP, as a physicist, I just have to say this: I do not care about wavelength. My training has me taught to think in eV. As long as I get eV, i'm happy, and I don't give a crap what word they use for different region of the EM spectrum (hard or soft x-rays? That's so quaint and ill-defined Ė I do not give a crap anymore.)

As long as it is clear what is referred to and what goes actually into the body (photons, electrons, protons, ions). So I probably could help you more if you give me a link to a document you have a problem with. I know that often those documents are written by physicists who have no idea how to talk to non-physicists (sometimes we physicist do not know how to talk to each other...), and translated by people who do not know anything about physics, often resulting in great sounding techno-babble with little more information than toilet paper.
My assumption has been that there is some WOO involved in the OP. Like Gamma rays are deadly, but good old fashioned X-rays are safer?
__________________
Great minds discuss ideas.
Medium minds discuss events.
Small minds spend all their time on U-Tube and Facebook.
casebro is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Old 7th August 2019, 02:52 PM   #27
WhatRoughBeast
Graduate Poster
 
Join Date: Apr 2011
Posts: 1,385
If you know the energy in eV, you can use this calculator https://www2.chemistry.msu.edu/facul...ml/cnvcalc.htm to find the wavelength.
WhatRoughBeast is offline   Quote this post in a PM   Nominate this post for this month's language award Copy a direct link to this post Reply With Quote Back to Top
Reply

International Skeptics Forum » General Topics » Science, Mathematics, Medicine, and Technology

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -7. The time now is 12:32 AM.
Powered by vBulletin. Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.

This forum began as part of the James Randi Education Foundation (JREF). However, the forum now exists as
an independent entity with no affiliation with or endorsement by the JREF, including the section in reference to "JREF" topics.

Disclaimer: Messages posted in the Forum are solely the opinion of their authors.