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Dose discrepancy between planning system estimation and measurement in spine stereotactic body radiation therapy: A case report
Author(s) -
Arumugam Sankar,
Berry Megan,
Ochoa Cesar,
Xing Aitang,
Beeksma Bradley,
Vial Philip
Publication year - 2017
Publication title -
journal of medical imaging and radiation oncology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.31
H-Index - 43
eISSN - 1754-9485
pISSN - 1754-9477
DOI - 10.1111/1754-9485.12617
Subject(s) - medicine , radiation treatment planning , nuclear medicine , quality assurance , pinnacle , spinal cord , radiosurgery , radiation therapy , vertebral body , radiology , surgery , external quality assessment , pathology , psychiatry
Summary Stereotactic body radiation therapy ( SBRT ) to treat spinal metastases has shown excellent clinical outcomes for local control. High dose gradients wrapping around spinal cord make this treatment technically challenging. In this work, we present a spine SBRT case where a dosimetric error was identified during pre‐treatment dosimetric quality assurance ( QA ). A patient with metastasis in T7 vertebral body consented to undergo SBRT . A dual arc volumetric modulated arc therapy plan was generated on the Pinnacle treatment planning system ( TPS ) with a 6 MV Elekta machine using gantry control point spacing of 4°. Standard pre‐treatment QA measurements were performed, including Arc CHECK , ion chamber in CTV and spinal cord (SC) region and film measurements in multiple planes. While the dose measured at CTV region showed good agreement with TPS , the dose measured to the SC was significantly higher than reported by TPS in the original and repeat plans. Acceptable agreement was only achieved when the gantry control point spacing was reduced to 3°. A potentially harmful dose error was identified by pre‐treatment QA . TPS parameter settings used safely in conventional treatments should be re‐assessed for complex treatments.