TY - JOUR
T1 - Technical Note
T2 - Dosimetric characterization of the dynamic beam flattening MLC sequence on a ring shaped, Jawless Linear Accelerator with double stacked MLC
AU - Bollinger, Douglas
AU - Laugeman, Eric
AU - Li, Taoran
AU - Hilliard, Jessica
AU - Heermann, Ana
AU - Kim, Hyun
AU - Hugo, Geoff
AU - Mutic, Sasa
AU - Dong, Lei
AU - Cai, Bin
N1 - Publisher Copyright:
© 2019 American Association of Physicists in Medicine
PY - 2020/3/1
Y1 - 2020/3/1
N2 - Purpose: To characterize the dosimetric features and limitations of the dynamic beam flattening (DBF) on the Halcyon 2.0 linear accelerator (Varian Medical Systems). Methods: A predefined multi-leaf collimator (MLC) sequence was introduced and used to flatten the 6 MV flattening filter free (FFF) beam on the Halcyon 2.0. Dosimetric characterizations of the flattened beams, including beam flatness, symmetry, percent depth dose (PDD), output factor and MU linearity, were investigated. Flatness and symmetry were obtained from profile measurements with both radiographic films (EDR2) and a two dimensional ion-chamber array (IC Profiler, Sun Nuclear Corporation). MU linearity, output factors, and PDDs were measured in a water tank with a CC13 ion chamber (Scanditronix Wellhöfer, Nuremburg, Germany). In addition, the effect of the DBF sequence on 3D plan quality was evaluated by creating DBF plans for a 4-field box rectum and an AP/PA spine plan. Patient specific QA was performed on these plans. Results: At 100 cm SSD and 10 cm depth, a flatness of <3% was observed on both transversal and radial profiles for all square field sizes ≥10 cm with DBF. For both larger and smaller field sizes the flatness showed a tendency to increase as the fields got bigger or smaller, respectively. Similar trends in flatness were observed at all depths measured. All measured output factors for square field sizes ≥5 cm were within 1% of the TPS prediction. Linearity was ≤2.02% for all measurements. For both treatment sites, the MD judged the plans created for the Halcyon without the use of DBF not to be clinically acceptable, however considered both the TrueBeam plan and the Halcyon plan with the DBF sequence to be clinically acceptable. Conclusions: The DBF sequence on the Halcyon and its characteristics were investigated. The analysis indicates that the DBF sequence can be used on the Halcyon to generate clinically acceptable 3D treatment plans.
AB - Purpose: To characterize the dosimetric features and limitations of the dynamic beam flattening (DBF) on the Halcyon 2.0 linear accelerator (Varian Medical Systems). Methods: A predefined multi-leaf collimator (MLC) sequence was introduced and used to flatten the 6 MV flattening filter free (FFF) beam on the Halcyon 2.0. Dosimetric characterizations of the flattened beams, including beam flatness, symmetry, percent depth dose (PDD), output factor and MU linearity, were investigated. Flatness and symmetry were obtained from profile measurements with both radiographic films (EDR2) and a two dimensional ion-chamber array (IC Profiler, Sun Nuclear Corporation). MU linearity, output factors, and PDDs were measured in a water tank with a CC13 ion chamber (Scanditronix Wellhöfer, Nuremburg, Germany). In addition, the effect of the DBF sequence on 3D plan quality was evaluated by creating DBF plans for a 4-field box rectum and an AP/PA spine plan. Patient specific QA was performed on these plans. Results: At 100 cm SSD and 10 cm depth, a flatness of <3% was observed on both transversal and radial profiles for all square field sizes ≥10 cm with DBF. For both larger and smaller field sizes the flatness showed a tendency to increase as the fields got bigger or smaller, respectively. Similar trends in flatness were observed at all depths measured. All measured output factors for square field sizes ≥5 cm were within 1% of the TPS prediction. Linearity was ≤2.02% for all measurements. For both treatment sites, the MD judged the plans created for the Halcyon without the use of DBF not to be clinically acceptable, however considered both the TrueBeam plan and the Halcyon plan with the DBF sequence to be clinically acceptable. Conclusions: The DBF sequence on the Halcyon and its characteristics were investigated. The analysis indicates that the DBF sequence can be used on the Halcyon to generate clinically acceptable 3D treatment plans.
KW - dynamic beam flattening
KW - halcyon
KW - photon radiotherapy
UR - http://www.scopus.com/inward/record.url?scp=85078779486&partnerID=8YFLogxK
U2 - 10.1002/mp.14001
DO - 10.1002/mp.14001
M3 - Article
C2 - 31885088
AN - SCOPUS:85078779486
SN - 0094-2405
VL - 47
SP - 948
EP - 957
JO - Medical physics
JF - Medical physics
IS - 3
ER -