Updated to correct unfinished thought: Your explanation of the intensity of the gamma bursts detected (being 180° from one another) in one direction having to travel through more tissue than the bursts in the opposite direction as the way to locate where the bursts are originating, does not take into account the different distances traveled for each photon (of a particular photon pair) from the point of annihilation to the detector ring, nor the angles of incidence of each photon (of that photon pair) to the tangents of the detector ring at the points of detection: obviously if the annihilation occurrence is not dead center of the detector ring (circle), then either the resulting distances traveled by each photon (of that photon pair) to the detector ring will be different, or the angles of incidence of each photon (of that photon pair) to the tangents of the detector ring at the points of detection will not be 90°, or both. Re: your explanation from about 6:48 to about 10:36. Therefore, I submit that determining the locations from where the gamma bursts are originating is more a function of the values of their different distances from the detector ring, their angles of incidence to the tangents at the points of detection on the detector ring, or both. For any photon pair, knowing the difference in distance each photon has to travel to the detector ring, the diameter of the detector ring, and the angle of incidence to the tangents of the detector ring at the points of detection (angle will be the same [mirror-imaged] for both photons as their paths of travel are 180° in opposite directions to the detector ring: combined paths of both photons can be represented as a chord on a circle) is what is needed to locate where the gamma bursts are originating. The other information is known: speed of light, wavelength of photon and subsequent properties, mapping instrumentation, etc.
Very comprehensive explaination ..only thing the 180 degree angle between photons is consequence of conservation of momentum not conservation of energy .Masses of positron and electron anihilate and because the momentum must be conserved that is the reason instead of a single photons we have two photons moving anti phase.
It’s mind boggling how someone theorized how this could all work, and how someone engineered it to actually work as well. Stunning. This is slightly off topic, but this is one of those things that really highlights how insanely developed we have become over the last century and a half. The fact we went from just barely figuring out how to build an automobile to theorizing and engineering something like this in such a relatively short amount of time is outrageous.
The population explosion and increase in life standards certainly helped. It's harder to develop science when 90% of the population are farmers vs 50% attending university. All off the back of oil and transgenic farming!
I have watched endless scientific videos having explanations but most of them were hard to understand.. that I ended up searching another 100000 videos to understand them... but this video!!! clears out all the complexity!!! thank you for providing me with such a clear explanation! :)
Back in the late 80s I worked for a Danish company producing PET- and SPECT-scanners. This little recap on how the PET-scanner works brought back many fond memories. Thanks for sharing!
such a great video!! thank you sooo much!! this is the best explanation I found after looking at many resources and even better than what I learnt in my class! Super thanks for your work! Also looking to understand SPECT, I hope I can another video of yours explaining SPECT.
Hey! Student from Cognitive Neuroscience! Very useful! Thanks a lot :) way more fast and interesting way to learn than good old books. You made the subject passionating! :D
Excellent and simple explanation of the PET physics. Just one comment, though: what you say around 9.25 that the scanner is able to determine the source of the annihilation by calculating the energy difference between the two coincidence photons is purely wrong - for many reasons. Most importantly, the LSO or LYSO detectors do not have sufficient energy resolution to determine the location of the annihilation within a few mm - as you suggest. If that was possible, you wouldn't really require a ring of detectors, because you could just simply histogram the coincidence events into an image. However, this is NOT possible and tomographic information is necessary (i.e. events around the object) to resolve the location of the annihilation. Having said that, most clinical scanners nowadays can measure the arrival time of the coincidence photons with high accuracy (in the order of pico-seconds) and as such they can narrow down the location of the annihilation within a few millimeters (the location is actually a Gaussian distribution). This is called Time of Flight and although it can substantially improve the signal to noise of the reconstructed images, you still require sufficient tomographic information around the object. There were a couple other minor inaccuracies in your explanation, but most of it was really good and simple! Well done!
Thanks for your feedback. I’m aware of my error (made this video quite a few years ago. I will need to add an errata to my description. I appreciate your efforts.
I don't get how the detector can know the location of the Annihilation when both 180° y-rays are detected at the same time. Does the detector compare the amplitude of the Photon energy? It must compare something to know the difference in distance of the travel from the 2 y-rays right?
Brilliant explanation. I have unfortunately had 2 of these scans in the last 6 months, so understanding what is happening is excellent. Quick question? How sensitive is this though? Will a scan only pick up a glucose hungry tumour? Or could it potentially find just initial stages on cancer cells etc? Thank you for a very clever video.
my PET /CT showed " metabolic activity" in ascending colon same area 4 yrs apart. no one said anything was amiss. i don't understand. my dr is away for extended leave so i cannot ask him
Your explanation of the intensity of the gamma bursts detected (being 180° from one another) in one direction having to travel through more tissue than the bursts in the opposite direction as the way to locate where the bursts are originating, does not take into account the different distances traveled for each photon (of a particular photon pair) from the point of annihilation to the detector ring, nor the angles of incidence of each photon (of that photon pair) to the tangents of the detector ring at the points of detection: obviously if the annihilation occurrence is not dead center of the detector ring (circle), then either the resulting distances traveled by each photon (of that photon pair) to the detector ring will be different, or the angles of incidence of each photon (of that photon pair) to the tangents of the detector ring at the points of detection will not be 90°, or both. Re: your explanation from about 6:48 to about 10:36. Therefore, I submit that determining the locations from where the gamma bursts are originating is more a function of the values of their different distances from the detector ring, their angles of incidence to the tangents at the points of detection on the detector ring, or both. For any photon pair, knowing the difference in distance each photon has to travel to the detector ring, the diameter of the detector ring, and the angle of incidence to the tangents of the detector ring at the points of detection (angle will be the same [mirror-imaged] for both photons as their paths of travel are 180° in opposite directions to the detector ring; combined paths of both photons can be represented as a chord on a circle). The other information is known: speed of light, wavelength of photon and subsequent properties, mapping instrumentation, etc.
This is good. The emission of 2 gamma rays and the useful info from those was news to me. Is the position of the emitting cells calculated by the speed of light being different through different media ie. slower through the body tissues?
I had one pet scan Wednesday and on Friday doctor (professor) told me to have an MRI scan Wednesday (nextweek) ,"to have a closer look". At my pancreas; he said he saw what looks like a benign mark. I think doctors always say benign, then when they say tumor, after a closer look, MRI, you're a bit better prepared for hearing tumor after all. One other doctor, the professor's assistant told me earlier that I am "blessed", because I came in early. He is Italian, he means lucky. I asked him if examining my self (anus) and coming to the (gp) doctor, was helpful, he said yes, it was. oOo
Hi ! Thank you very much for the amazing video ! I am actually studying radiology for my exam and in the PET part they say that the process to create FDG is normally done using a very complex machine called ciclotron which accelerates the particles in a spiral system. In the end of the spiral there is a pure chemical element (in this case 18O that is transformed in 18F). I am not understanding how they do it: do they put glucose at the exit of the ciclotron to create the FDG or they first create the radioactive element and then combine it to the glucose ? I don't know if I expressed myself in a very clear way... In case I will reformulate the question in another way. thank you for your help
18F is usually made in cyclotron by bombarding 18O. It’s got a relatively short half life so it then goes under a series of complex reactions to get it attached to the glucose molecule.
Sir, my mother has undergone breast cancer surgery 6 years ago, in 2016 Oct, with wide excision of right breast, in Er pr and HER2 report it has detected as invasive duct carcinoma. Followingly treated with 12 chemo and 32 radiations after slow release leterosole tablets. But now in a CT scan done on 11 Aug 2022. Primarily it is detected as a lymph node near the lugs on the right side. She is feeling lot of giddiness . What detection may I expect in a PET scan.
Sorry to hear. I’m not a doctor so I’d be asking medical questions to the professionals. But I do know that a PET scan will pick up excessive uptake of glucose and so will help identify tumour growth. Hope it goes well.
I’m confused about how intensity of the photon is measured. I thought that according to quantum physics, a single photon has a fixed amount of energy that depends upon its wavelength and when detecting individual photons, intensity is the probability that it will be detected at a particular location and not how much energy it has.
thank you for your clarification, but could you please what are the different between PET, and SPECT and as you explain on this video the main aim of the PET is for functions, so the SPECT for what, if you have another video which explains the SPECT please guide me. regards,,, Ali
If the, let's say tumour, is not in the middle of the ring of gamma cameras, how do both y-photons reach the camera at the same time?? I mean do they not have the same velocity? Therefore one should arrive earlier than the other, when the origin is not in the centre of the gamma cameras, right?
They both teach at the same time however the one that travels further is more attenuated. That’s how they determine the distance. It’s a fair bit more complex than that but you get the idea.
Whoa antimatter! This is cool. I’m just here for fun. Just kidding. PET found a mass. Just want to see how useful this is for diagnosis of masses in lower abdominal area. Especially when a doctor “claims” to see a fed tumor 😒 🤷🏻♀️ I want to know info and not just trust from one scan. I should have been in the med field this stuff is better than astrophysics. (Similar with the applications - so funny!) It’s like studying the beginning of the universe here haha!
Updated to correct unfinished thought:
Your explanation of the intensity of the gamma bursts detected (being 180° from one another) in one direction having to travel through more tissue than the bursts in the opposite direction as the way to locate where the bursts are originating, does not take into account the different distances traveled for each photon (of a particular photon pair) from the point of annihilation to the detector ring, nor the angles of incidence of each photon (of that photon pair) to the tangents of the detector ring at the points of detection: obviously if the annihilation occurrence is not dead center of the detector ring (circle), then either the resulting distances traveled by each photon (of that photon pair) to the detector ring will be different, or the angles of incidence of each photon (of that photon pair) to the tangents of the detector ring at the points of detection will not be 90°, or both. Re: your explanation from about 6:48 to about 10:36. Therefore, I submit that determining the locations from where the gamma bursts are originating is more a function of the values of their different distances from the detector ring, their angles of incidence to the tangents at the points of detection on the detector ring, or both. For any photon pair, knowing the difference in distance each photon has to travel to the detector ring, the diameter of the detector ring, and the angle of incidence to the tangents of the detector ring at the points of detection (angle will be the same [mirror-imaged] for both photons as their paths of travel are 180° in opposite directions to the detector ring: combined paths of both photons can be represented as a chord on a circle) is what is needed to locate where the gamma bursts are originating. The other information is known: speed of light, wavelength of photon and subsequent properties, mapping instrumentation, etc.
Very comprehensive explaination ..only thing the 180 degree angle between photons is consequence of conservation of momentum not conservation of energy .Masses of positron and electron anihilate and because the momentum must be conserved that is the reason instead of a single photons we have two photons moving anti phase.
It’s mind boggling how someone theorized how this could all work, and how someone engineered it to actually work as well. Stunning.
This is slightly off topic, but this is one of those things that really highlights how insanely developed we have become over the last century and a half. The fact we went from just barely figuring out how to build an automobile to theorizing and engineering something like this in such a relatively short amount of time is outrageous.
The population explosion and increase in life standards certainly helped. It's harder to develop science when 90% of the population are farmers vs 50% attending university. All off the back of oil and transgenic farming!
I have watched endless scientific videos having explanations but most of them were hard to understand.. that I ended up searching another 100000 videos to understand them... but this video!!! clears out all the complexity!!! thank you for providing me with such a clear explanation! :)
Back in the late 80s I worked for a Danish company producing PET- and SPECT-scanners. This little recap on how the PET-scanner works brought back many fond memories. Thanks for sharing!
such a great video!! thank you sooo much!! this is the best explanation I found after looking at many resources and even better than what I learnt in my class! Super thanks for your work! Also looking to understand SPECT, I hope I can another video of yours explaining SPECT.
Great explanation of the PET scanner with good graphics and simple terms. Many thanks.
Hey! Student from Cognitive Neuroscience! Very useful! Thanks a lot :) way more fast and interesting way to learn than good old books. You made the subject passionating! :D
Thank you for all the explanations. Helps me a lot. Wish u all the best in future....
Excellent teaching aid - thanks very much!
Thank you for the video, this is definitely going to help me in the presentation today :-) !!
wow this is the most interesting thing ever and thankyou for explaining it so so well
Good summary, thank you
you helped me pass grade nine thank you so much-
You’re welcome. 🤓
@@PhysicsHigh 🙏🙏🤠
M@@PhysicsHigh
This sure gonna helps me a lot in my presentation today. Thanks
Glad it helps
Great video and explains really in a simple way I just had a pet scan you really explained everything that happened to me thank you
thank you this was so helpful!! very clear explanation
Excellent and simple explanation of the PET physics. Just one comment, though: what you say around 9.25 that the scanner is able to determine the source of the annihilation by calculating the energy difference between the two coincidence photons is purely wrong - for many reasons. Most importantly, the LSO or LYSO detectors do not have sufficient energy resolution to determine the location of the annihilation within a few mm - as you suggest. If that was possible, you wouldn't really require a ring of detectors, because you could just simply histogram the coincidence events into an image. However, this is NOT possible and tomographic information is necessary (i.e. events around the object) to resolve the location of the annihilation. Having said that, most clinical scanners nowadays can measure the arrival time of the coincidence photons with high accuracy (in the order of pico-seconds) and as such they can narrow down the location of the annihilation within a few millimeters (the location is actually a Gaussian distribution). This is called Time of Flight and although it can substantially improve the signal to noise of the reconstructed images, you still require sufficient tomographic information around the object. There were a couple other minor inaccuracies in your explanation, but most of it was really good and simple! Well done!
Thanks for your feedback. I’m aware of my error (made this video quite a few years ago. I will need to add an errata to my description. I appreciate your efforts.
Wow this video is amazing ! 🥳🤩
Thanks a lot, it was really helpful and an amazing video !! Excellent..
Great explanation. You are very good teacher.
Thankyou
Thank you so much for your explanations! Really clear and very useful !
Thank you a lot
I wish I could hit that like button twice !!!👍👍TYSM
Samreen farooq me to.
Photons are emitted at 180 degrees by the Law of Conservation of momentum
Thank you very much sir.
Nicely explained Sir. Thank you.
I don't get how the detector can know the location of the Annihilation when both 180° y-rays are detected at the same time.
Does the detector compare the amplitude of the Photon energy? It must compare something to know the difference in distance of the travel from the 2 y-rays right?
Carbon MatrixG3 Yes. I think the detector is also measuring the intensity of the gamma rays on each end.
It measures the time delay btw the two photons and thus relative position can be calculated.
thanks... med student here :)
Thanks lot. Beautiful explanation.
Excellent.
Educative indeed. Thank you.
Brilliant explanation. I have unfortunately had 2 of these scans in the last 6 months, so understanding what is happening is excellent. Quick question? How sensitive is this though? Will a scan only pick up a glucose hungry tumour? Or could it potentially find just initial stages on cancer cells etc? Thank you for a very clever video.
Thank you 😊
my PET /CT showed " metabolic activity" in ascending colon same area 4 yrs apart. no one said anything was amiss. i don't understand. my dr is away for extended leave so i cannot ask him
Your explanation of the intensity of the gamma bursts detected (being 180° from one another) in one direction having to travel through more tissue than the bursts in the opposite direction as the way to locate where the bursts are originating, does not take into account the different distances traveled for each photon (of a particular photon pair) from the point of annihilation to the detector ring, nor the angles of incidence of each photon (of that photon pair) to the tangents of the detector ring at the points of detection: obviously if the annihilation occurrence is not dead center of the detector ring (circle), then either the resulting distances traveled by each photon (of that photon pair) to the detector ring will be different, or the angles of incidence of each photon (of that photon pair) to the tangents of the detector ring at the points of detection will not be 90°, or both. Re: your explanation from about 6:48 to about 10:36. Therefore, I submit that determining the locations from where the gamma bursts are originating is more a function of the values of their different distances from the detector ring, their angles of incidence to the tangents at the points of detection on the detector ring, or both. For any photon pair, knowing the difference in distance each photon has to travel to the detector ring, the diameter of the detector ring, and the angle of incidence to the tangents of the detector ring at the points of detection (angle will be the same [mirror-imaged] for both photons as their paths of travel are 180° in opposite directions to the detector ring; combined paths of both photons can be represented as a chord on a circle). The other information is known: speed of light, wavelength of photon and subsequent properties, mapping instrumentation, etc.
This is good. The emission of 2 gamma rays and the useful info from those was news to me. Is the position of the emitting cells calculated by the speed of light being different through different media ie. slower through the body tissues?
Nice explanation!
thank you sir
I had one pet scan Wednesday and on Friday doctor (professor) told me to have an MRI scan Wednesday (nextweek) ,"to have a closer look". At my pancreas; he said he saw what looks like a benign mark. I think doctors always say benign, then when they say tumor, after a closer look, MRI, you're a bit better prepared for hearing tumor after all.
One other doctor, the professor's assistant told me earlier that I am "blessed", because I came in early. He is Italian, he means lucky.
I asked him if examining my self (anus) and coming to the (gp) doctor, was helpful, he said yes, it was.
oOo
Just awesome. thank you sir for this video.(y)
Dear Sir, i am sending my PET scan report. Please suggest me the stage of disease i am in. I have attached just the final written report.
Perfect summary 👌🏼
Hi ! Thank you very much for the amazing video ! I am actually studying radiology for my exam and in the PET part they say that the process to create FDG is normally done using a very complex machine called ciclotron which accelerates the particles in a spiral system. In the end of the spiral there is a pure chemical element (in this case 18O that is transformed in 18F). I am not understanding how they do it: do they put glucose at the exit of the ciclotron to create the FDG or they first create the radioactive element and then combine it to the glucose ? I don't know if I expressed myself in a very clear way... In case I will reformulate the question in another way. thank you for your help
18F is usually made in cyclotron by bombarding 18O. It’s got a relatively short half life so it then goes under a series of complex reactions to get it attached to the glucose molecule.
They are emited in opposite directions not because of conservation of energy but of momentum! It is mentioned twice wrongly in the video.
can't believe this is high school physics
Sir, my mother has undergone breast cancer surgery 6 years ago, in 2016 Oct, with wide excision of right breast, in Er pr and HER2 report it has detected as invasive duct carcinoma. Followingly treated with 12 chemo and 32 radiations after slow release leterosole tablets. But now in a CT scan done on 11 Aug 2022. Primarily it is detected as a lymph node near the lugs on the right side. She is feeling lot of giddiness . What detection may I expect in a PET scan.
Sorry to hear.
I’m not a doctor so I’d be asking medical questions to the professionals.
But I do know that a PET scan will pick up excessive uptake of glucose and so will help identify tumour growth. Hope it goes well.
is this for detection of only malignancies or benign tumours can also be detected?
It depends . It’s for identifying any tissue that has a higher than usual glucose consumption
sir please show its working practically if possible, like demonstrating actually how it works! thanks for the knowledge though! it will be helpful
I’m confused about how intensity of the photon is measured. I thought that according to quantum physics, a single photon has a fixed amount of energy that depends upon its wavelength and when detecting individual photons, intensity is the probability that it will be detected at a particular location and not how much energy it has.
amazing
thank you for your clarification, but could you please what are the different between PET, and SPECT and as you explain on this video the main aim of the PET is for functions, so the SPECT for what, if you have another video which explains the SPECT please guide me.
regards,,,
Ali
GREAT!
If the, let's say tumour, is not in the middle of the ring of gamma cameras, how do both y-photons reach the camera at the same time?? I mean do they not have the same velocity? Therefore one should arrive earlier than the other, when the origin is not in the centre of the gamma cameras, right?
They both teach at the same time however the one that travels further is more attenuated. That’s how they determine the distance. It’s a fair bit more complex than that but you get the idea.
Thanks sir
What does PET scan not show ?
very good
Thank you very much! Clearly explained.
Gamma radiations move in opposite direction due to law of conservation of momentum not the law of conservation energy.
did you say electrons have mass? - JC
you are great! omg
awesome
How come, that the half life of 18F is longer the higher the temperature?
Is pet scan has a lot of radiation?
Why aren't you teaching at my university?? WHYYYY???!!!!! *cries in nuclear rain*
Thanks for the compliment.
Correction alert:The chemical formula for FDG is C6 H11 FO5 not C6 H12 FO5
Notes. Thanks
Whoa antimatter! This is cool. I’m just here for fun. Just kidding.
PET found a mass. Just want to see how useful this is for diagnosis of masses in lower abdominal area. Especially when a doctor “claims” to see a fed tumor 😒 🤷🏻♀️ I want to know info and not just trust from one scan. I should have been in the med field this stuff is better than astrophysics. (Similar with the applications - so funny!) It’s like studying the beginning of the universe here haha!
Ha! I was right! You can’t see a “fed tumor” 😅 actually this video didn’t really touch on that…🙄 back to research. (Yes I’m in denial stage 🥸)
cool
There is only physics , no need to point out “ High School”
True true. That’s one of the reason I changed my name.
Hahaha since when is Elementary Particles a high school physics topic???
It is in Australia
High School Physics Explained That's awesome! Is that a junior or senior level class? What other topics does the high school curriculum cover?