TDSC report to TPC, TPC Spring meeting, Apr 17 2013

Timothy Zhu, Chair

Lei Dong, Vice Chair

1.  WGPB summary of activities – Indra Das, Chair, Ron Zhu, Vice Chair.

Task group / Chair / Date started / End date / Comments
TG-185 / Jonathan Farr / 12/08/2008 / 12/31/2013 / Promised a report by annual meeting, 2013.
TG-202 / Michael Moyers / 5/11/2010 / 12/31/2013 / A draft report is written with a few sections remain outstanding. This will be written by AAPM 2013.
TG-224 / Bijan Arjomandy / 1/17/2012 / 12/31/2013 / A rough draft was written and distributed on Apr 5 2013. A second draft report is expected at AAPM annual meeting 2013.

(1)  WGPB has submitted a proposal for particle beam summer school in 2014 with Indra Das and Herald Paganetti as Co-Chairs but this is not selected this year.

2.  WGIMRT summary of activities – Siyong Kim, chair, Bill J Salter, Vice Chair

(1). Siyong Kim is the new Chair of WGIMRT. Three guest members (Anthony Doemer, Joseph Hanley, and Jie She) are now voting members of WGIMRT.

(2) WGIMRT has undergone a major restructuring and has now established four sub-groups and eachsub-group will monitor one of four main areas:delivery, planning, dosimetry, and protocol. Each subgroup will file a quarterly report if needed. There are four members in each group and each member rotate to a leading role for a quarter. Current structure is summarized in the following table.

Sub-Group / First / Last / Leading order
Chair / Siyong / Kim
Vice Chair / Bill / Salter
1 / Anthony / Doemer / 1
Murshed / Hossain / 2
Nikos / Papanikolaou / 3
Ying / Xiao / 4
2 / Jay / Burmeister / 1
Enrique / Izaguirre / 2
Ping / Xia / 3
Kamil / Yenice / 4
3 / Gary / Ezzell / 1
Jie / Shi / 2
Michael / Snyder / 3
Chuan / Wu / 4
4 / Nesrin / Dogan / 1
Joseph / Hanley / 2
Dimitris / Mihailidis / 3
William / Simon / 4

(3) Delivery subgroup: 1) A white paper entitled “A Report on Flattening Filter Free c-arm Linear Accelerators” was submitted to TPC by Ying Xiao. The first review by TPC is done and Ying is chairing the response. 2) The use of IMRT for SBRT continues to be a major topic. 3) Varian introduced ‘EdgeTM’, mainly designed for SBRT. 4) Vero, a ring gantry based machine by BrainLab, is also a recent platform, mostly for SBRT. 5) ViewRay, a real time MR guided machine, is first installed at Washington University. It would be useful to know little more detail about 3 recent systems, Varian Edge, Vero, and ViewRay in the aspect of IMRT. The WGIMRT Chair suggests sub-group 1 to investigate and summarize each one’s advantages over existing technologies and possible issues that users may need to pay attention

(4). Planning subgroup: 1) Wu et al. [Med. Phys. 40, 021714 (2013)] investigated whether an overlap volume histogram (OVH)-driven planning application using an IMRT database can guide and automate VMAT planning for head-and-neck cancer. 2) Bangert et al. [Med. Phys. 40, 011716 (2013)] presented a meta analysis of four beam angle selection (BAS) strategies that incorporates fluence optimization (FO) into BAS by combinatorial optimization (CO) and one BAS strategy that decouples FO from BAS, i.e., spherical cluster analysis (SCA). Then, the underlying parameters of the BAS process were investigated and the dosimetric benefits of the BAS strategies were quantified. 3) Younge et al. [Med. Phys. 39, 7160 (2012)] developed an aperture-regularization objective function into the optimization process for VMAT, and quantified the impact of using this objective function on dose delivery accuracy and optimized dose distributions. In specific, an aperture-based metric (“edge penalty”) was established that penalizes complex aperture shapes based on the ratio of MLC side edge length and aperture area. 4) Bedford [Phys Med Biol. 58(5):1235-50 (2013)] proposed a method of using iterative least-squares (ILS) for aperture optimization in VMAT and evaluated the performance by comparing with segment weight optimization. Sinograms showing effective monitor units delivered by MLC leaf pairs over the course of beam delivery were used to elucidate the comparison in five prostate and pelvic nodes patients retrospectively selected. The WGIMRT Chair suggests sub-group 2 to pay more attention on robust planning methods and consider leading a review article preparation, eventually.

(5) Dosimetry subgroup: 1) The IMRT QA white paper is still under revision. 2) Fredh et al. [Med Phys 40, 031716 (2013)] provide a comparison of different QA systems for rotational IMRT. 3) Traditional discussions such as what and how much QA should be done, how much of this should be machine specific, and how much should be patient specific are still active topics. 4) The ability of typical 2D dosimetry and gamma analysis techniques to catch clinically relevant delivery errors has been called into question [Kruse, Med Phys 37, 2516-2524 (2010), Nelms et al., Med Phys 38 1037-1044 (2011), and Stasi et al., Med Phys 39, 7626-7634 (2012), etc.]. 5) The RPC credentialing test results have improved with time but there are still far too many facilities failing, as indicated by the 66% pass rate on the spine anthropomorphic phantom presented last year at the AAPM meeting. We all know the limitations of using Gamma index for IMRT/VMAT plan QA, it might be important and worthy of further research to explore new (e.g., true 3D Gamma based) plan QA methods.

(6). At this moment, there is no suggestion on Task Group formation yet. WG-IMRT is planning to put more effort in stabilizing the new monitoring system in the first half of this year, then start to move our focus onto looking for other possible activities such as TG formation and writing guidelines.