AbstractID: 6802 Title: Dosimetry Verification of Dynamic IMRT: An In-Vivo Study in Canine
Subjects
The spatial and dosimetric accuracy with which dynamic intensity
modulated radiation beams (dIMRT) can deliver highly localized dose
distributions to tumors near critical structures has been
assessed.
Comparative studies of dose distributions between
measurements and calculations were carried out using
thermoluminescent dosimeters (TLD’s), films, and diodes in phantoms,
cadaver canines and live subject canines.
The method for which the delivery of the beams was carried
out uses a dynamically driven multileaf collimation (sliding window
technique) and the computation of dose-matrix is performed using a
macro pencil beam algorithm (MPB). The optimization of the weights of
beam fluences was based on projections onto convex sets (POCS),
performed with an inverse algorithm.
In-vivo dose measurements were performed in a selected
population of canines and a one year post-irradiation observation was
allowed to study the patterns of radiation damage to critical structures and
soft tissues in both controlled patients, receiving conventional
conformal therapy, and those receiving IMRT delivery. A quantitative
study based on image correlation of CT studies, obtained for planning
with CT studies obtained at treatment time was used to assess the
accuracy of the inverse and forward planning processes.
The results of our study show the deviation in point dose correlation
to be less than 3% on beam axis from the planned doses. The survival
rate for both the control patients and IMRT patients was found to be
markedly different, favoring those irradiated with the latter technique.