Large Field IMRT option for Varian MLC

[BrasAndKets]

Varian has a feature called Large Field IMRT (LF-IMRT). As I
understand it it is different than WF-DMPO in pinnacle. LF-IMRT is
basically the same as split field IMRT but each gantry angle set of
beams is combined into one beam and carriage shifts are part of the
MLC file. This makes life much easier for therapists or sites that
have paper charts and would have to hand chart each split field. I
have contacted Pinnacle to see if they currently support this and they
regrettably do not at this time. Does anyone know of a way to combine
these split fields into one to take advantage of this feature on the
linac until Pinnacle can implement this into the TPS directly?

Ian Gordon, MS
Physicist

[Feygelman, Vladimir]

I would be curious to know how people with paper charts do IMRT...
We have found the Pinnacle solution to provide better dosimetry than
split fields. I am not sure this is worth pursuing.

Vladimir Feygelman, PhD
Physicist
tel: (813) 745 8424 | fax: (813) 745-7231 | email:
vladimir....@moffitt.org

Ian Gordon, MS
Physicist

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[Scott Dube]

I am fascinated by your email address Ian.  "Bras and Kets"?  I am familiar with the former but not the latter.

[Tripathi, Sugata PHD]

Scott,

These refer to symbols to formulate/denote expectation values of field operators, as in quantum mechanics or quantum field theory. Thanks!

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[BrasAndKets]

It is a reference to Dirac notation in Quantum Physics. I became dear
friends with them while working on my physics degrees. Nice to see
your name pop up, I still remember my first tour of a RadOnc
department that you gave me back at Queens Medical Center, thanks
again.

-Ian

On Sep 15, 11:36 am, Scott Dube <scott.d...@gmail.com> wrote:
> I am fascinated by your email address Ian.  "Bras and Kets"?  I am familiar
> with the former but not the latter.
>

[BrasAndKets]

If you are referring to WF-DMPO as the Pinnacle solution then I do not
agree that it provides better dosimetry than split fields as do many
of the posters on this board. WF-DMPO will kill more motors on the
linac and gives Pinnacle less options when trying to both spare
critical structures and dose the target often providing worse
dosimetry. The pinnacle rep I spoke with about LF-IMRT said that more
and more physicists are asking about LF-IMRT and it may be supported
in the future. However, rather than debating yet again about the pros
and cons of WF-DMPO vs split field IMRT lets keep the conversation
about possibilities for implementing LF-IMRT for those of us who would
like to use it. BTW many clinics, even large ones still use paper
charting, it doesn't mean we don't also use R&V for loading plans.

-Ian

On Sep 15, 11:07 am, "Feygelman, Vladimir"

<Vladimir.Feygel...@moffitt.org> wrote:
> I would be curious to know how people with paper charts do IMRT...
> We have found the Pinnacle solution to provide better dosimetry than
> split fields. I am not sure this is worth pursuing.
>
> Vladimir Feygelman, PhD
> Physicist
> tel:  (813) 745 8424 | fax:  (813) 745-7231 | email:

> vladimir.feygel...@moffitt.org

> For more options, visit this group athttp://groups.google.com/group/pinnacle3-users?hl=en

[Feygelman, Vladimir]

By dosimetry I meant agreement between measurement and calculations, which is often pretty bad for split fields for obvious reasons. Sorry for the confusion. But If the Pinnacle rep promised you to implement the LF, you can take it to the bank. In the meantime, the WF-DMPO works fine and the motors seem OK with VMAT, let alone the WF. The MLC motors now are not what they used to be a few years ago...

VF

Vladimir Feygelman, PhD
Physicist
tel: (813) 745 8424 | fax: (813) 745-7231 | email: vladimir....@moffitt.org

[JGar...@mbhs.org]

Bra and Ket notation, also known as Dirac notation, is a common method of working with various quantum mechanics methods and operations. It's a simple yet powerful way of performing qm calculations.

Jeffrey A. Garrett, MS, DABR
Chief Physicist
Mississippi Baptist Medical Center
1225 North State Street
Jackson, MS 39202

Office: 601-968-1725
Cancer Center: 601-968-1416 or 1420
Fax: 601-960-3317

-----Scott Dube <scott...@gmail.com> wrote: -----

=======================
To: pinnacl...@googlegroups.com
From: Scott Dube <scott...@gmail.com>
Date: 09/15/2011 10:36AM
Subject: Re: [p3rtp] Large Field IMRT option for Varian MLC
=======================

[Elizabeth Shiner]

We prefer to do WF-DMPO but will do split fields on rare occasions. As for paper charting - because we have an R&V system I was finally able to 'let go' of paper charting of each field. Rather we just paper chart a daily dose site summary, cord max if applicable, daily shifts and weekly SSDs. We have managed to reduce our paper treatment chart to 1 double-sided sheet of paper - one side for patient photo, demographics and diagnosis and the other for daily tx charting.

This paper chart is meant as a 'quick reference' for the physicians to see where patients are in Tx and how close to a boost or final they are. Yes, I know all of that is in the R&V but the Docs like a piece of paper :). Our paper charts come in handy for various 'freak-emergency' situations and we are reluctant to completely eliminate them.

Elizabeth

VF

-Ian

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[Vadim Kuperman]

We have used both approaches (i.e., split fields and Wide-field DMPO) with Pinnacle.  At our site there exists no significant difference in mapcheck based QA results for these techniques.  The problem with having split fields primarily exists for those sites which are not paperless and, as a result, sometimes have to track the dose for two many fields.  The only potential problem with WF DMPO is abutment of MLC leaves in the field.   However, it appears that if one uses multiple fields (e.g., n > 5-7) then potential dosimetric uncertainties due to the inadequate modeling of transmission through the region of abutment should be small (but not always negligible!). 

 

Plan quality appears independent of the utilized technique.  Motor failure these days has become much less of a problem.  Delivery time is basically the same too.

 

Vadim Kuperman, PhD

Halifax Medical Center

Daytona Beach, FL

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[BrasAndKets]

This topic was not intended to debate WF-IMRT vs Split field IMRT.
There is a feature of Varian Linacs that allows combined split fields
at a single gantry angle for continuous delivery of split fields.
This feature is called Large Field IMRT and is a Linac addon. Is
there a way to combine the MLC files to allow users of Pinnacle to
take advantage of this feature? Mode up one field in Mosaiq and
deliver all fields at that gantry angle with one beam on. Varian
provided an MLC file to demonstrate this at acceptance but Pinnacle
doesn't have a way of combining these fields. Any ideas?

Ian

[Scott Dube]

Since you asked Ian, I will answer.  I assume Varian will charge you for the Large Field IMRT option.  If the price is anywhere close to the DMPO option, then I would forego the former and get the latter.

 

Besides, don't you want to run your plans with DMPO so you can limit the number of segments and eliminate the small area and/or low MU segments?

[BrasAndKets]

I think there is some confusion between the two. Large Field IMRT is
a Linac option, DMPO is an optimisation/planning tool. I would like
to use Pinnacle with DMPO to create an IMRT plan with split fields,
but combine the split fields for each gantry angle into one MLC file
that is compatible and can be delivered on the LF-IMRT enabled linac.
The only difference between what we already do and what LF-IMRT does
is currently we deliver 1-3 split fields per gantry angle for a high
quality plan but mode up each field separately and deliver
individually, using the LF-IMRT enabled Linac and a compatible plan,
which currently is not implemented by Pinnacle, you would mode up one
beam for each gantry angle but all the split fields would be delivered
one after another, reducing intrafractional motion and reducing
possible human errors by making delivery more automated. I know that
many of these terms can start to blend together and meaning is
sometimes abstract so I hope I am describing each feature vividly
enough to clear up the confusion. The LF-IMRT is a very nice feature
on Varian linacs so I am looking forward to the possibility of
utilizing it. If I can answer any questions on this I would be happy
to. Right now I am wondering if anyone knows enough about the
exported beam files to be able to combine these fields manually,
initially for experimental purposes and hopefully eventually for
clinical use.

Ian Gordon

[Ohm, Mike]

Ian and others,
While I'm not familiar with Varian LF-IMRT, the Siemens Artiste can do carriage moves during a single dynamic field and we currently plan those in Pinnacle v9. We just uncheck the option to 'split if necessary' and we get up to a 40 cm wide field for a particular gantry angle if needed. Perhaps the same thing would be done (in P3) if that option is added to the Varian linac?

The only 'commercial' way I'm aware of combining split fields is via RadCalc. Look in chapter 8 of the manual (I'm using v6.1). There is a specific function in the software to combine beams; not sure during which version this was introduced. You could also do some cutting and pasting of the raw RTP/DICOMRT text file(s) that are exported; I'm sure you would get into some uncomfortable editing then though....

Mike

-----Original Message-----
From: pinnacl...@googlegroups.com [mailto:pinnacl...@googlegroups.com] On Behalf Of BrasAndKets
Sent: Friday, September 16, 2011 12:00 AM
To: pinnacle3-users
Subject: [p3rtp] Re: Large Field IMRT option for Varian MLC

Ian Gordon

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