Dose gradient analyses in linac-based intracranial stereotactic radiosurgery using paddick's gradient index: Considerationof the optimal method for plan evaluation

Kazuhiro Ohtakara, Shinya Hayashi, Hiroaki Hoshi

Research output: Contribution to journalReview article

19 Citations (Scopus)

Abstract

The objective of our study was to describe the dose gradient characteristics of Linac-based stereotactic radiosurgery using Paddick's gradient index (GI) and to elucidate the factors influencing the GI value. Seventy-three plans for brain metastases using the dynamic conformal arcs were reviewed. The GI values were calculated at the 80% and 90% isodose surfaces (IDSs) and at the different target coverage IDSs (D99, D95, D90, and D85). The GI values significantly decreased as the target coverage of the reference IDS increased (the percentage of the IDS decreased). There was a significant inverse correlation between the GI values and target volume. The plans generated with the addition of a 1-mm leaf margin had worse GI values both at the D99 and D95 relative to those without leaf margin. The number and arrangement of arcs also affected the GI value. The GI values are highly sensitive to (1) the IDS selection variability for dose prescription or evaluation, (2) the target volume, and (3) the planning method. To objectively compare the quality of dose gradient between rival plans, it would be preferable to employ the GI defined at the reference IDS indicating the specific target coverage (e.g., D95), irrespective of the intended marginal dose. The modified GI (mGI), defined in this study, substituting the denominator of the original GI with the target volume, would be useful to compensate for the false superior GI value in cases of target over-coverage with the reference IDS and to objectively evaluate the dose gradient outside the target boundary.

Original languageEnglish
Pages (from-to)592-599
Number of pages8
JournalJournal of Radiation Research
Volume52
Issue number5
DOIs
Publication statusPublished - 2011

All Science Journal Classification (ASJC) codes

  • Radiation
  • Radiology Nuclear Medicine and imaging
  • Health, Toxicology and Mutagenesis

Fingerprint Dive into the research topics of 'Dose gradient analyses in linac-based intracranial stereotactic radiosurgery using paddick's gradient index: Considerationof the optimal method for plan evaluation'. Together they form a unique fingerprint.

  • Cite this