Development and Validation of a Novel Method for Kilovoltage Dose Computation
TITLE:
Development and Validation of a Novel Method for Kilovoltage Dose Computation
DATE:
Friday, Feb 15th, 2013
TIME:
3:30 PM
LOCATION:
GMCS 214
SPEAKER:
Mauro Tambasco.
San Diego State University.
ABSTRACT:
Significant kilovoltage (kV) x-ray dose can be accrued by patients undergoing interventional
radiology or daily imaging for image guided radiotherapy procedures. To address this, we are
developing and validating a fast, accurate, and clinically feasible method that uses computed
tomography (CT) voxel data to estimate radiation dose absorbed from kV imaging procedures.
Our approach computes kV dose at points of interests (POIs) by numerically evaluating the
linear Boltzmann transport equation using a combination of deterministic and Monte Carlo
(MC) techniques. This hybrid approach accounts for material heterogeneity, and uses kVp
and half value layer measurements to characterize the spatial fluence and spectra needed to
compute dose for a given imaging system and technique settings. The dose at a POI is computed
within seconds using the Intel© Core™ i7 CPU 920 2.67 GHz quad core architecture, and
we developed a method that uses a strategically constructed sparse grid of POIs to accurately
compute volumetric dose distributions. The calculations are performed using CT voxel data,
making it flexible and feasible for clinical applications. To validate our method, we compared
our calculations of depth and profile doses for a 125 kVp open beam incident on a heterogeneous
block phantom with calculations from standard MC codes (MCNP and EGSnrc) and with
experimental measurements using a Varian® On-Board Imager®. Our depth and profile dose
calculations agreed with MCNP and EGSnrc to within 1.4% and 1.3%, respectively, and they
agreed with experiment to within 2% and 4%, respectively. The level of accuracy of our method
is comparable to MCNP and EGSnrc, and agrees well with experiment. Hence, our voxel-based
hybrid approach provides rapid and accurate calculations of absorbed x-ray dose at any POI or
set of POIs, which makes it a practical tool for computing patient-specific dose from kV imaging
procedures.
HOST:
Dr. Jose Castillo.
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