MLC monitoring using Beamnrc

[Wanggl180328]

I tried to use Beamnrc to track the behaviors of the MLC. I firstly tried to use the VARMLC codes provided by the manual to take place the second collimator, but the beam_gui show the data is mismatch. I think the version of the manual maybe too old. Therefore, I tried to customize the VARMLC but I did not find somewhere to set the leaf parameters including the size of tongue and groove, the leaf gap or the leaf radius. Otherwise, I wonder if there is a component to describe a MLC with an arbitrary shape.

[rtownson]

The modern varian MLC models best fit the SYNCVMLC or SYNCHDMLC CMs in BEAMnrc. For those component modules you'll find detailed control of the MLC shape. There is no option for arbitrary shape, you would have to do that using egs++ instead of BEAMnrc, but it would be tedious/tricky.

[Wanggl180328]

OK I will try to use the egs++ to find if it works. But I found the egs++ may be difficult to get the PDD or beam profile. If I want to get these parameters, should I use the geometry to partition the plane I concerned?

[rtownson]

You could try asking Varian for the CAD mesh of their MLCs, and then use the new mesh support in egs++ to model the MLCs. So far no one has tried this yet.

To get PDDs and profiles, you can use an XYZ geometry in egs++, and even an egsphant file in the same format that DOSXYZnrc uses. It's possible to output a 3ddose file from those and use the usual dose analysis tools. Otherwise, egs++ simulations can output the dose to every region, and so long as you understand the numbering you can produce a profile from that.

https://nrc-cnrc.github.io/EGSnrc/doc/pirs898/classEGS__XYZGeometry.html

[Wanggl180328]

Thank you for your valuable advise.

[Wanggl180328]

I tried to use SYNCHDMLC CM, but when I tried to beam_build the related modules, many warnings appeared. When I opened the gui, the leaf details are also not availiable to adjust. These warning do not exist when I use other jaws.

[rtownson]

If you're using SYNCHDMLC, why is it complaining about MLC_cm? Do you also have a MLC CM in the .module file? Make sure you completely remove the accelerator directory if you're trying to beam_build it with the same name after changing the .module file - or make sure to give the .module file a new name after making changes.