Well I only saw those metal masks you put where the beam hits, where you shape the hole to fit the shape of the tumor, this is totally different from what you are doing I believe.
I imagine if you look down on a patient lying on his back, if the radiation is coming from above, you basically would want something like a topographical map (like a 3D contour map). See this map to get an idea of what I mean. Mountain peaks are where it gets a few layers thick. Surely this would be optimum? You would use a single thickness lead sheet and cut it to make each layer of the map. Then you also wouldn't have vertical seams that could maybe burn the patient? There would be no packing problem then either.
That said, the (brass?) masks I saw did indeed seem to have been created by a computerized cutter, as the holes were made of many fine vertical cuts, perhaps <1mm in thickness and maybe more resolution in the y axis.
So my questions are:
1. Is this really the best solution? I mean you have to type in all those numbers, wouldn't it be better if you could go directly from some scanned data to a lead solution?
2. The other question is, this is all seems to be 2D, i.e. looking from the side at a cross section. But we're really talking about 3D, that is, an arrangement of many slabs all over the patient, more slabs in some places than others.
3. I feel pretty uncomfortable about how these threads tend to die quickly but you might need more help. I honestly don't think it's appropriate to be asking such important questions on this kind of a board when misunderstanding of a problem could jepoardize someone's life (though the basic ideas of packing and dynamic programming are of course good things to know). For example in the beginning I thought it was a student with a homework problem!
Maybe it's a problem with perlmonks that things are so evanescent (I still don't know how to view the list of nodes that showed on the homepage 2 days before). In particular I was wondering about whether vertical seams are dangerous, since it made me worry about a completely unattenuated beam burning a line into the patient if for example the pattern has a completely vertical seam, then how it is manufactured, i.e. could it come apart there, etc. That is how I came up with the idea of cutting each layer of a contour map with a jigsaw so there would be no seams and it could closely match the results of a CT scan, allowing much higher resolution than if you just type in the numbers (possibly making mistakes) yourself.
In reply to Re: Finding the simplest combination of descrete thicknesses that sums nearest to the target thickness.
by mattr
in thread Finding the simplest combination of descrete thicknesses that sums nearest to the target thickness.
by doowah2004
| For: | Use: | ||
| & | & | ||
| < | < | ||
| > | > | ||
| [ | [ | ||
| ] | ] |