Monte carlo dose calculations in conventional thorax fields for 60Co photons.
OBJECTIVE
Our purpose was to apply the MCNP4C Monte Carlo (MC) code for dose calculations in the thorax region and compare the results with those of measurements and a conventional treatment planning system (TPS).


METHODS
We modeled a Theratron 780E 60Co unit and benchmarked our modeling with percent depth doses (PDDs), beam profiles, and output factors measured in a water phantom. For PDDs and beam profiles, the differences between measurements and MC calculations were less than 1% and 2%, respectively. We used an anatomic thorax phantom for evaluation of a conventional TPS and our MC calculation results.


RESULTS
In comparing the results of calculations and measurements for our thorax geometries, the errors of conventional and MC methods were 20% and 2%, respectively. For the anterior mediastinal field and large thorax field the accuracy of the conventional method was acceptable, but for small fields of lateral thorax irradiation, the error of the conventional method was as high as to 20%. In all MC calculations, discrepancy from the measurements was less than 2%.


CONCLUSIONS
Our results showed that the MCNP4C MC code could be used in dose calculations in treatment planning for 60Co photon irradiation. In addition, the application of the MC method for dose calculations in radiotherapy with 60Co photons was recommended.
Mesbahi
Asghar
A
Medical Physics Department, Medical Faculty, Tabriz University of Medical Sciences, Tabriz, Iran.
Allahverdi
Mahmoud
M
Gheraati
Hossein
H
D000465:Algorithms; D003037:Cobalt Radioisotopes; D005720:Gamma Rays; D008953:Models, Anatomic; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D017785:Photons; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D015203:Reproducibility of Results; D013909:Thorax / Q000528:radiation effects*
D003037:Cobalt Radioisotopes