We really don't know what we're doing...

Zoomzoom said:
@TooFastTim The only ways to reduce costs are basic business models - reduce the cost of manufacture, increase the number of treatments. "buy cheaper / sell more". Time will take care of both. Tech almost always gets cheaper with time, and as the modality becomes more mainstream, more people will be treated with it.
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Pardon break. That was very strong cup of coffee.

Yes that's the plan we working on now. I've been doing historical comparisons between the emergence of electron/photon machines in radiotherapy and there are similarities. I'm not sure whether I can yet join the dots but there are similarities.

Zoomzoom said:
for the 'don't know WTF we are doing' bit - shhhh and don't tell anyone. It works. :) Maybe that is all you need for now, and the rest is someone else's problem, but I do completely understand the 'but I have to know what I don't know' itch. It's very frustrating when you know you know enough to know you don't know anything.
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Actually, having had a few days to think about it, my observations are the least of our worries. I talk about microns. Bloody patients move centimeters. Now if only we could put them into a coma! And that is exactly what they do with paediatrics.

Again, please pardon my break. I've had to deal with some academic stuff and some personal stuff. Some good. And some bad news from ex-SA colleagues.
 
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TooFastTim said:
I talk about microns. Bloody patients move centimeters. Now if only we could put them into a coma! And that is exactly what they do with paediatrics.
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You mean this medieval torture device restraint isn't immobilising enough?

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TooFastTim said:
I've been in this science/business for nearly thirty years now. It is really is (and I **** thee not) right at the cutting edge of the medical and physical sciences. This business and science is consuming vast amounts of capital (from which I am, handsomely, benefitting).

The modality does work. It has an extraordinarily successful cure rate for those cases for which it is recommended.

Now, from my 30 years of experience, I realise: WE KNOW NOTHING. Barely a jot. We are merely scratching the surface. I keep poking and prodding at this knowledge only to realise that they (they being collective the they. AKA I and my peers) are ignorant.

For those of you old enough to remember Supertramp. Supertramp had an album: Crime of the Century: "Well lets rip off the mask and lets see. Well there's you and there's me". Well, here am I and We are exposed. We are naked.

This is not bullshit. This is real. The more I dig the more I realise how little we understand of the physics underlying the modality.

Would you continue or retreat to a monastery?

Oh, I am an ex-Saffie and got my grounding in the modality in SA.
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The digital era has a Good technical innovative side but also an Abstract evil side poorly understood by most today.
The digital era could have been the Key to a better life for all, but instead it start sucking the money of every pocket surrounding it, it has to have disastrous consequences in the long run and today that run has not reached its end. This side of digital is overrated and overprised, and the code had became parasitic.
 
kolaval said:
And what stops you from finding those answers?
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We are looking. One of the surprising things was that we found the ionisation potential for some materials is very poorly understood. It's a start.
 
Moto Guzzi said:
The digital era has a Good technical innovative side but also an Abstract evil side poorly understood by most today.
The digital era could have been the Key to a better life for all, but instead it start sucking the money of every pocket surrounding it, it has to have disastrous consequences in the long run and today that run has not reached its end. This side of digital is overrated and overprised, and the code had became parasitic.
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The internet has the capacity to do enormous good as a library but is being abused?
 
TooFastTim said:
Yip, you can move a few mm in them. In a sub-millimeter game it's too much.
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LOL you know I meant that either sarcastically or rhetorically or both depending on your tone of voice when you read it LOL.

Patients BREATHE apart from anything else. I don't see how you can circumvent the problem at the margins. I was going to say unless your imaging can move with the patient somehow, but wow, my mind freaks out a little at imagining the complexity of working that out. You'd have to basically have an instantaneous and continuous mapping and targeting system to pull that off.
 
Zoomzoom said:
LOL you know I meant that either sarcastically or rhetorically or both depending on your tone of voice when you read it LOL.

Patients BREATHE apart from anything else. I don't see how you can circumvent the problem at the margins. I was going to say unless your imaging can move with the patient somehow, but wow, my mind freaks out a little at imagining the complexity of working that out. You'd have to basically have an instantaneous and continuous mapping and targeting system to pull that off.
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My reply was intended at the pic you posted. The pic you posted immobilises the head. That's ok for a head and neck treatment. Immobilising the torso isn't so simple because, as you mentioned, patients have a nasty propensity to breath. But even with that device the patient can still move a few mm. And we're dicking around with, theoretical, microns.

Gated therapy is a whole different story. I believe I may have been the first to implement (a very crude form) of gated therapy in proton therapy. I never published. It seemed so trivial an idea at that the time. This would have been about '92. There were, of course, many others involved but it was my basic idea. We really didn't realise how far ahead we were. Even today, what we did is spoken of in slightly awed tones.

Breathing gating isn't that complicated. 3-D gating is whole different ball game. We have it for photons using MRI. I think it's possible for protons but I need to think about it a bit more. If we can combine MRI and prompt-gamma stuff with a quickly responding accelerator we'll have it made. Kinda...
 
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TooFastTim said:
My reply was intended at the pic you posted. The pic you posted immobilises the head. That's ok for a head and neck treatment. Immobilising the torso isn't so simple because, as you mentioned, patients have a nasty propensity to breath. But even with that device the patient can still move a few mm. And we're dicking around with, theoretical, microns.

Gated therapy is a whole different story. I believe I may have been the first to implement (a very crude form) of gated therapy in proton therapy. I never published. It seemed so trivial an idea at that the time. This would have been about '92. There were, of course, many others involved but it was my basic idea. We really didn't realise how far ahead we were. Even today, what we did is spoken of in slightly awed tones.

Breathing gating isn't that complicated. 3-D gating is whole different ball game. We have it for photons using MRI. I think it's possible for protons but I need to think about it a bit more. If we can combine MRI and prompt-gamma stuff with a quickly responding accelerator we'll have it made. Kinda...
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Bloody hell you guys are actually attempting to compensate for movement.
 
Zoomzoom said:
Bloody hell you guys are actually attempting to compensate for movement.
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Yes. Have a looksee here: VisionRT. Not really motion compensation but more like accomodation of motion. For motion compensation have a look at MRI Linac

The gated system I conceived was similar to the Vision RT system. Patient would move less than a prescribed amount and the beam would be held, patient repositioned and beam released. If the patient moved more than the prescribed amount beam was stopped.
 
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TooFastTim said:
Yes. Have a looksee here: VisionRT. Not really motion compensation but more like accomodation of motion. For motion compensation have a look at MRI Linac

The gated system I conceived was similar to the Vision RT system. Patient would move less than a prescribed amount and the beam would be held, patient repositioned and beam released. If the patient moved more than the prescribed amount beam was stopped.
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I think the paper I read was talking about something in between these two - using the MRI / CT scans to get an image at full inhalation and an image at full exhalation and using that to program the beam to move within those parameters according to real time mapping. If I understood what I read correctly.

I was just blown up by the complexity of even attempting to do this. On one hand it seems very simple to do - just use some sort of imaging to give you real time positioning and adjust the beam accordingly - but scans are slow and by the time you've taken the image, and processed it, far too much time has elapsed. To be absolutely precise you have to be operating in fractions of a second.
 
Hi Zoom-Zoom.

'fraid you can't use CT for photon motion compensation. The photons emerging from the patient on the downstream side will swamp the CT detectors. So it has to be MRI. Which is inherently slow. I have no idea how they do this. I'm a beams/accelerator/engineer guy. Imaging is, IMO, a dark art and best left to the clever people.

In an earlier reply I referred to prompt gammas. Prompt gammas is a method by which we *may* be able to do in-vivo real-time dosimetry. Basically, measure the deposited radiation dose without invasive instrumentation. The idea is thus: protons arrive and deposit energy by exciting electrons along the path they traverse. These electrons subsequently relinquish that acquired energy as photons and that relinquished energy is proportional to that energy they absorbed from the proton. So by watching a treatment with CT we can develop a 3-D map of the dose deposition during treatment. Now, because we're treating with protons those protons will stop within the body so: no swamping of the detectors on the downstream side of the patient which would be the case with photons.

But, and here comes the fudge-factor, the prompt-gammas will now saturate the CT scanner (therapeutic doses are orders of magnitude greater than diagnostic doses) if we were to use that CT scanner for motion compensation. So, as current tech stands, we'll still need an MRI scanner for motion compensation. Problem is fitting all this tech into the same space. Unless... TBC.....
 
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TooFastTim said:
Hi Zoom-Zoom.

'fraid you can't use CT for photon motion compensation. The photons emerging from the patient on the downstream side will swamp the CT detectors. So it has to be MRI. Which is inherently slow. I have no idea how the do this. I'm a beams/accelerator/engineer guy. Imaging is, IMO, a dark art and best left to the clever people.

In an earlier reply I referred to prompt gammas. Prompt gammas is a method by which we *may* be able to do in-vivo real-time dosimetry. Basically, measure the radiation does without invasive instrumentation. The idea is thus: protons arrive and begin to deposit energy by exciting electrons along the path they traverse. These electrons subsequently relinquish that acquired energy as photons and that relinquished energy is proportional to that energy they absorbed from the proton. So by watching a treatment with CT we can develop a 3-D map of the dose deposition during treatment. Now, because we're treating with protons those protons will stop within the body so: no swamping of the detectors on the downstream side of the patient which would be the case with photons.

But, and here comes the fudge-factor, the prompt-gammas will now saturate the CT scanner (therapeutic doses are orders of magnitude greater than diagnostic doses) if we were to use that CT scanner for motion compensation. So, as current tech stands, we'll still need an MRI scanner for motion compensation. Problem is fitting all this tech into the same space. Unless... TBC.....
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Why not use sonar? Or is that insufficiently accurate? I'm probably answering my question lol ... but if you have mapped the tumour with other, more precise imaging, wouldn't sonar be sufficiently accurate to give fast real time positioning?
 
Zoomzoom said:
Why not use sonar? Or is that insufficiently accurate? I'm probably answering my question lol ... but if you have mapped the tumour with other, more precise imaging, wouldn't sonar be sufficiently accurate to give fast real time positioning?
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I had thought about this but sonar doesn't provide sufficient discrimination between tissue types that we require. If I remember my reasoning at that time. It's an argument not dissimilar to the CT v Cone Beam CT. CBCT gives a decent overview but lacks the detail (i.e. Hounsfield numbers) required for planning.

It's a bloody good point!! As mentioned above I had thought about it but got distracted...oooh look a squirrel.... I don't know whether ultrasound is capable of discriminating between soft tissue organs?
 
TooFastTim said:
I had thought about this but sonar doesn't provide sufficient discrimination between tissue types that we require. If I remember my reasoning at that time. It's an argument not dissimilar to the CT v Cone Beam CT. CBCT gives a decent overview but lacks the detail (i.e. Hounsfield numbers) required for planning.

It's a bloody good point!! As mentioned above I had thought about it but got distracted...oooh look a squirrel.... I don't know whether ultrasound is capable of discriminating between soft tissue organs?
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That is what it is used for - imaging soft tissue. I think the issue with sonar is loss of accuracy with increased depth. It's good at superficial soft tissue imaging, but less accurate the deeper the scan.
 
Zoomzoom said:
That is what it is used for - imaging soft tissue. I think the issue with sonar is loss of accuracy with increased depth. It's good at superficial soft tissue imaging, but less accurate the deeper the scan.
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You have the same exponential roll-off with photons but CT works great..Aha...ultra sound works on reflected signals. CT on those which have passed through the anatomy.

Pinged you.
 
TooFastTim said:
You have the same exponential roll-off with photons but CT works great..Aha...ultra sound works on reflected signals. CT on those which have passed through the anatomy.

Pinged you.
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Yes but the advantage of maybe looking at sonar is that it is fast, they are already using it for real time guided surgery so the underlying tech is there, and the necessary equipment isn't as huge as an MRI or CT scanner. Dunno LOL just an idea that popped into my head.
 
Zoomzoom said:
Yes but the advantage of maybe looking at sonar is that it is fast
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Au contraire. It is slow (330 m/s in air vs 3e8 in vacuum for gammas) but it could be fast enough for our purposes. But its simplicity and compactness is enticing.
 
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