Will have a look at the DVH is now, so initially I've just brought up the PTV 54 so this is the volume that the 54 greys is prescribed to, so we're expecting 99% of our volume to be receiving at least 95% of the prescribed dose. So let's have a little look at what we've achieved here, so I've got 98.94% think that'll do. Receiving 96.5% of the dose.
So that is meeting our expectations.
When we look up PCV 45, we're gonna see a difference level because we know that actually that volume.
We're only attempting to treat 245 greys, So what we want for that volume is 99% of the volume to be receiving at least 95% of the prescribed dose, and for this volume, the prescribed dose is 45 greys. So again, if I have a go at finding 99, so that's just over 99% and we've got 42.
.9.
And a 95% of 45 is 42.75 greys, so fat volume is also receiving an adequate dose. Looking at that.
But obviously as Jenny will have said to you, when we were looking at the prostate plan and we were actually creating our own plans, that deviates only tells you some of the story. So yes, this looks pretty good on this, but you still need to scroll through your different slices to figure out which portion of your volume isn't receiving the adequate dose. And actually is your 95% too big? Does it actually cover an excessive amount of normal tissue?
So it's not enough to just look at the DVH is you need to be considering what does the dose distribution look like within your arm slices and actually have a look at those as well.
So I'm just going to have a little look at some of the dose constraints that are on the giny technique presentation and I will add to the next slide so that you can see them so when we look at the small bowel it tells us when we're delivering 54 greys and 25 fractions. The volume receiving 45 Grays should be less than 50 CCS. Now let's see if I can.
Demonstrate that.
I just had to check exactly how to do that before we started. OK, so at the moment we've got percentage of volume here, so I'm going to right click in my window. I'm in plan evaluation, but I'm assuming this probably also works when you're in external being planning and I'm going to go to absolute volume because that's what I want to know for this small in testing, so I want the volume receiving 45 grades to be less than 50 CCS, so let's have a little look at.
What I'm going to get SO50CC's is going to be along here and 45 greys, so actually on this I can see that definitely is the case, because 45 grazes along here somewhere. So let's have a little look.
43 so.
Say 45 Grace is being received by only about 1 1/2% and no one and a half CCS. Sorry of this man.
Structure.
The small bowel so and I've also got the volume receiving 30 grace should be less than 350 CCS, so let's find the point where we're going to be about 30 greys. So tiny bit further along.
So I've got, so I'm going to call that 30 grades 29.9 and I've got 51.7 centimeters cubed, which is equivalent to CCS receiving back to. So that's absolutely fine.
So for the small intestine, the dose constraint is is expressed in cubic centimeters, be cause the entire structure isn't outlined, so you can't say you can only treat 50% to a particular dose because only the volume that's in the relevant part of the patient is actually outlined.
So that's where you see a difference in some of these.
Dose constraints where they'll be expressed as a percentage of a structure, in which case you have to have outlined the entire structure. So if you're looking at a DVH where you need to meet along constraint, you must have outlined the entire long to be able to say that the volume receiving 20 greys must be less than a particular percentage of that organ. So for the small intestine we haven't outlined the entire structure.
And what we're interested in is what quantitive of this particular structure is receiving that dose. So the dose constraint is expressed in cubic centimeters. Or the volume constraint are should say, is expressed in cubic centimeters. So the author volumes are all an percentages, so the bladder the entire bladder has been outlined. The entire rectum has been outlined.
There's a dose constraint for kidneys, but actually for this lady and we are away from the kidneys, and we've got cordon and equinor and femoral heads, so I'm going to right click again and I'm going to take off absolute volume because we're back to being interested in percentage volume rather than an.
The actual absolute volume, so let's have a quick look at the rectum.
So we've got rectum there and looking at the dose constraints we want.
The volume receiving 40 greys should be less than 85% of the rectum, so that dose is 40 Grays.
Say let's put a point, though, so let's go there. OK, so that's 41.
So that's faulty raised there.
So the volume receiving 40 greys is 60, three point 3%. So we are well within that dose constraint. And then we've got the volume receiving 30 Greys should be less than 95%.
So let's open. It looks at 30 Grays.
So that's going to be somewhere along here.
There we are volume receiving 30 greys is 80%, so again, we're well within our constraint now and then. Let's have a little look at the bladder. So we've already discussed that the bladder is quite.
Radioresistant so will have a little look at the bladder and the fact that bladder is affected by.
It being an empty bladder protocol, so the the dose to bladder will be greater because of that empty and bladder protocol. So let's have a little look. If so, I've got a plain bladder there.
So this is our blood and our pink line, so we want Volume 2 receiving 40 Grays to be less than 75%. So again, it's actually the same and dose constraint as you seeing in the rectum. So bladder 40 Grays.
So we have got.
92% of our bladder receiving 40 grace so we are not meeting that bladder constraint and that is because we're using an empty bladder protocol which shrinks the bladder down. An means that the majority of the bladder is actually sitting right within our.
PCV region, where we're actually aiming to get off 45 Grays an if we look at the volume receiving 30 Grays should be less than 95%, so we're about there.
Volume receiving 30 grazes. Almost all of the bladder, so we have failed to meet those bladder constraints.
Because we've got an empty bladder, so hopefully that helps you to understand some of what we're seeing on those deviators.