A database of clinically approved stereotactic radiosurgery treatment plans was created. One hundred and seventy targets in the database were then retrospectively evaluated using conformity indices suggested by RTOG, SALT‐Lomax and Paddick. Relationships between the three alternative conformity indices were determined. The Paddick index combines the information provided by the RTOG and SALT‐Lomax indices into a single index. The variation in the geometric overlap ratio, which is related to the SALT‐Lomax index, was found to be not clinically relevant for our cohort of patients, and thus the Paddick and RTOG indices can be directly related. It was found that access to a dose volume histogram or dose distribution for a treatment plan renders the RTOG conformity index sufficient for plan quality evaluation.PACS number: 87.53.Ly
Purpose: This study summarizes the stereotactic radiosurgery (SRS) plans created over a period of five years. Additionally, factors that influenced the Radiation Therapy Oncology Group (RTOG) conformity indices of the plans were determined. Methods: A database of 170 SRS plans for brain metastases patients treated at the Tom Baker Cancer Centre using dynamic conformal arcs between November 2004 and December 2009 was constructed. This database was then used to retrospectively evaluate SRS plans and to determine target parameters that affect RTOG conformity index which is defined by CI= VRI/TV where VRI is the volume that receives the reference isodose and TV is the target volume. Results: Factors such as maximum dose to the target and minimum dose to the target did not appear to influence RTOG conformity index. However, target volume did relate to RTOG conformity index: conformity index increased as target volume decreased. For the 101 plans with target volumes larger than 1cm3 the average conformity index value was 1.68. For plans with target volumes smaller than 1cm3 the average conformity index value was 2.41. Additionally, a decrease in RTOG conformity index was correlated with a decrease in the volume of normal tissue receiving the prescription isodose. For plans where the volume of normal tissue receiving the prescription isodose was less than 1 cm3 the average RTOG conformity index was 1.32 while for plans where the volume of normal tissue receiving the prescription isodose was greater than 1 cm3 the average RTOG conformity index was 2.36 Conclusions: 170 SRS plans for brain metastases were evaluated and it was found that RTOG conformity index was influenced by target size and could be linked to the volume of non target tissue receiving the prescription isodose
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.