Analysis of Quality Parameters of Radiation Treatment Plans Using SRS (Stereotactic Radiosurgery) and SRT (Stereotactic Radiotherapy) – A Single Institution Six Year Experience

Aim: The study’s aims were to assess key plan quality indicators, including the Conformity Index, Gradient Index, and Homogeneity Index, which had previously been evaluated using isodose lines and DVH.
Materials and Methods: We reviewed the treatment plans for 37 retrospective cases that used the TrueBeam STx linac for stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) between 2019 and 2024.  Treatment plans were evaluated using the following plan quality parameters suggested by Radiation Therapy Oncology Group [RTOG] such as Quality of Coverage [QRTOG], Homogeneity Index [HIRTOG] and Conformity Index [CIRTOG] Apart from that, Paddick’s Conformity Index [CIPaddick], Lomax Conformity Index [CILomax], New Conformity Index, Gradient Measure (GM), Gradient Index (GI), R50%, and Equivalent Fall-off Distance [EFOD].
Results: The percentage accuracies of CIRTOG, CIPaddick, CILomax that are as per the protocol are 83.7%, 67.6%, 87.5%, respectively.  It was found that the plan quality metrics are independent of target volumes and shape.
Conclusion: On analysis, all the plan quality parameters of patient treatment plans which were treated earlier was found to be within the protocol.
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