Comparison of conventional and 3D conformal treatments using linac energies for prostate cancer

ABSTRACT

To evaluate the dosimetric difference between conventional and three-dimensional conformal Radiotherapy [3D-CRT] using 6 and 18 MV X-ray photons. Computed tomography scans of 26 pelvic patients were acquired and transferred to the 3D treatment planning system. For each patient, 8 Conventional plans [3, 4, 5 and 6 Fields] and one 3D-CRT plan were prepared using 6 and 18 MV photon energies. The minimum dose [D[min]], maximum dose [D[max]] and mean dose [D[mean]] to target [PTV] and organs at risk [OAR], Integral dose, Homogeneity Index and Conformity Index were compared for each plan. Also, Experimental measurements were performed using farmer ionization chamber on a patient based pelvic phantom. On Average, six-field [6F1] plans, offer minimum dose to critical organs and sufficient dose to prostate. Increasing the beam energy lead to a decrease in D[mean] of the bladder and femoral heads, as well as D[max] of PTV. The CI and ID were decreased by 4% and 11% respectively with increasing the energy and the number of beams. Experimental measurements were also in good agreement with calculations. 3D-CRT reduced D[mean] of bladder, rectum and femoral heads and also CI and ID were significantly improved by 44.6% and 30.8%, respectively. Increasing the photon energy and number of beams, improve the treatment parameters of bladder, femoral heads and PTV, except the rectum. 3D-CRT offered the most conformity in the delivery doses to the prostate while sparing dose to OARs, uninvolved structures with lower integral dose