The dosimetric impact of different photon beam energy on RapidArc radiotherapy planning for cervix carcinoma

Abstract

The main purpose of this study is to know the effect of three different photon energies viz., 6, 10, and 15 mega voltage (MV) on RapidArc (RA) planning for deep-seated cervix tumor and to develop clinically acceptable RA plans with suitable photon energy. RA plans were generated for 6, 10, and 15 MV photon energies for twenty patients reported with cervix carcinoma. RA plans were evaluated in terms of planning target volume (PTV) coverage, dose to organs at risk (OARs), conformity index (CI), homogeneity index (HI), gradient measure, external volume index of dose distribution produced, total number of monitor units (MUs), nontumor integral dose (ID), and low dose volume of normal tissue. A two-sample paired t-test was performed to compare the dosimetric parameters of RA plans. Irrespective of photon energy used for RA planning, plans were dosimetrically similar in terms of PTV coverage, OARs sparing, CI and HI. The numbers of MUs were 13.4 ± 1.4% and 18.2 ± 1.5% higher and IDs were 2.7 ± 0.8% and 3.7 ± 0.9% higher in 6 MV plans in comparison to that in the 10 and 15 MV plans, respectively. V1Gy, V2Gy, V3Gy, and V4Gy were higher in 6 MV plans in comparison to that in 10 and 15 MV plans. Based on this study, 6 MV photon beam is a good choice for RA planning in case of cervix carcinoma, as it does not deliver additional exposure to patients caused by photoneutrons produced in high energy beams.

Energy‐dependent OAR sparing and dose conformity for total marrow irradiation of obese patients

“…The decrease in monitor units for the 10 MV plans indicates that the higher energy beams were able to achieve equivalent target dose coverage more efficiently than the lower energy beams. This reduction in MUs for higher energy beams agrees with results found by other groups that have compared 6 MV with 10, 15, and 18 MV VMAT and IMRT plans for prostate and cervix cancer cases 34, 35, 36…”

Dosimetric impact of Acuros XB on cervix radiotherapy using RapidArc technique: a dosimetric study

“…The value of CI close to 1 and HI close to 0 signifies a better conformal and homogenous dose distribution to the PTV; gradient measure (GM): GM was determined as radius difference between the equivalent spheres of prescription and half prescription isodose volumes, which demonstrates dose falloff around PTV. The lower value for GM confirms a higher gradient in dose distribution around the target [16];…”

“…conformity index (CI): Volume of 95% isodose/Volume of PTV [15]; homogeneity index (HI) = (D 2% −D 98% ) D 50% [16].…”

Validation of the RapidArc delivery system using a volumetric phantom as per task group report 119 of the American association of physicists in medicine

“…The conformity index (CI) was calculated as the ratio between the volume covered by the prescribed isodose and the target volume. [ 16 ] The prescription doses (PD) for the C-shape, head and neck, multi-target, and prostate test cases were 50, 50, 50, and 76 Gy, respectively. Similarly, the homogeneity index (HI) was calculated as the DD normalized to the dose prescribed between doses covering 5% (D 5 ) and 95% (D 95 ) of the target.…”

“…Similarly, the homogeneity index (HI) was calculated as the DD normalized to the dose prescribed between doses covering 5% (D 5 ) and 95% (D 95 ) of the target. [ 16 ]…”