Abstract
In this report, Chair Heterogeneity Index (CHI) was introduced to assess the dose heterogeneity inside the target with a boost volume. CHI was defined by dividing (VRx − VDl) by (VDm − VDh): VRx, VDl, VDm and VDh were four points selected from the target cumulative dose volume histogram curve. The effectiveness of CHI was validated by assessing the treatment plans for nasopharyngeal cancer (NPC, 12 cases), breast cancer after breast-conserving-surgery (BC, 10 cases), and stereotactic radiosurgery after whole brain irradiation (SRS, 9 cases). Our results indicate that both CHI and HI of the target can distinguish Volumetric Modulated Arc Therapy (VMAT) from Intensity Modulated Radiation Therapy (IMRT, p < 0.05) while the mean differences in CHI (NPC 1.16, BC 1.19 and SRS 3.3) were larger than those in HI (NPC 0.03, BC 0.02 and SRS 0.02). In addition, CHI of the combination volume (the target minus the boost) were statistically higher in VMAT than IMRT in all three kinds of cancer. In conclusion, CHI was effective in assessing the dose heterogeneity inside a target containing a boost volume.
Highlights
In this report, Chair Heterogeneity Index (CHI) was introduced to assess the dose heterogeneity inside the target with a boost volume
It was interesting that homogeneity index (HI) of the Targets in Volumetric Modulated Arc Therapy (VMAT) plans, like CHI, were better than those in intensity modulated radiation therapy (IMRT) plans for all three cancers
There were different target volumes in Radiation Oncology which were clearly defined in The International Commission on Radiation Units and Measurements (ICRU) Report 5010, such as gross tumor volume (GTV), Clinical Target Volume (CTV), planning tumor volume (PTV) and so on
Summary
Chair Heterogeneity Index (CHI) was introduced to assess the dose heterogeneity inside the target with a boost volume. Chair Heterogeneity Index (CHI) was introduced to characterize the dose homogeneity for a target volume in SIB. In this case, the ideal cumulative dose volume histogram (cDVH) curve for the target is not a vertical line but shapes like an outline of a chair (Fig. 1), which makes the CHI more suitable than HI in describing the dose heterogeneity inside the target. We further validated the effectiveness of CHI and compared it with other heterogeneity indexes
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