Premium
SU‐FF‐T‐111: Head‐And‐Neck IMRT Without Beam‐Splitting
Author(s) -
Lei S,
Harter W,
Collins S,
Xia F,
Pang D,
Gag G
Publication year - 2009
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3181585
Subject(s) - head and neck , beam (structure) , nuclear medicine , field size , radiation treatment planning , mathematics , medical physics , physics , medicine , optics , radiation therapy , radiology , surgery
Purpose: Varian MLC leaf travel is limited to 14.5 cm. For large PTV, an IMRT field will be split into two or three sub‐fields. Thus a 9‐beam head‐and‐neck plan may end up with 18 or more treatment fields. The purpose of this study is to develop a non‐split IMRT planning technique and compare the quality of non‐split plans with beam‐split counterparts. Method: Varian Eclipse user can choose fixed‐jaws and set field‐size less than 14.5 cm so that IMRT field will not split. A small part of the PTV may be blocked by x‐jaws in a particular beam, but the missing dose from one beam can be covered by other beams at different gantry angles. We compared our previously treated 9‐beam‐split‐18‐field head‐and‐neck IMRT plans with corresponding non‐split plans of 9, 11, and 15 gantry angles. Plan DVH and IMRT QA results were analyzed. Results: Non‐split plans produced the same dose coverage as beam‐split plans. DVH curves of PTV for split and non‐split plans almost overlapped with each other. DVH of organs‐at‐risk were slightly different. Total treatment MU were about the same for all the plans. All IMRT QA plans delivered on a Varian Trilogy passed physics QA criteria, with non‐split plans showing slightly better passing scores. Conclusions: Creating IMRT plans without beam‐splitting is encouraged. Non‐split IMRT plans can be as good as beam‐split plans, but use only half of the number of beams. Quality of non‐split plans improves with increasing number of beams. The amount of improvement was larger for the number of beams going from 9 to 11 than that from 13 to 15, demonstrating a balance of costs and benefits. Cutting the number of beams by half may result in a number of benefits: more accurate dose delivery, shorter treatment time, and increased machine throughput and productivity.