Performance evaluation of an improved optical computed tomography polymer gel dosimeter system for 3D dose verification of static and dynamic phantom deliveries.
The performance of a next-generation optical computed tomography scanner (OCTOPUS-5X) is characterized in the context of three-dimensional gel dosimetry. Large-volume (2.2 L), muscle-equivalent, radiation-sensitive polymer gel dosimeters (BANG-3) were used. Improvements in scanner design leading to shorter acquisition times are discussed. The spatial resolution, detectable absorbance range, and reproducibility are assessed. An efficient method for calibrating gel dosimeters using the depth-dose relationship is applied, with photon- and electron-based deliveries yielding equivalent results. A procedure involving a preirradiation scan was used to reduce the edge artifacts in reconstructed images, thereby increasing the useful cross-sectional area of the dosimeter by nearly a factor of 2. Dose distributions derived from optical density measurements using the calibration coefficient show good agreement with the treatment planning system simulations and radiographic film measurements. The feasibility of use for motion (four-dimensional) dosimetry is demonstrated on an example comparing dose distributions from static and dynamic delivery of a single-field photon plan. The capability to visualize three-dimensional dose distributions is also illustrated.
Department of Radiation Oncology, M.D. Anderson Cancer Center Orlando, Orlando, Florida 32806, USA.
O
O
Lopatiuk-Tirpak
K M
KM
Langen
S L
SL
Meeks
P A
PA
Kupelian
O A
OA
Zeidan
M J
MJ
Maryanski
D005782:Gels / Q000737:chemistry*; D019047:Phantoms, Imaging; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D041622:Tomography, Optical / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods
D005782:Gels