Enhanced efficiency in helical tomotherapy quality assurance using a custom-designed water-equivalent phantom

S. Murty Goddu, Sasa Mutic, Olga L. Pechenaya, Summer R. Chaudhari, Jose Garcia-Ramirez, Dharanipathy Rangaraj, Eric E. Klein, Deshan Yang, James Grigsby, Daniel A. Low

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Tomotherapy is an image-guided, intensity-modulated radiation therapy system that delivers highly conformal dose distributions in a helical fashion. This system is also capable of acquiring megavoltage computed-tomography images and registering them to the planning kVCT images for accurate target localization. Quality assurance (QA) of this device is time intensive, but can be expedited by improved QA tools and procedures. A custom-designed phantom was fabricated to improve the efficiency of daily QA of our Tomotherapy machine. The phantom incorporates ionization chamber measurement points, plugs of different densities and slide-out film cartridges. The QA procedure was designed to verify in less than 30 min the vital components of the tomotherapy system: static beam quality and output, image quality, correctness of image registration and energy of the helical dose delivery. Machine output, percent depth dose and off-axis factors are simultaneously evaluated using a static 5 × 40 cm2 open field. A single phantom scan is used to evaluate image quality and registration accuracy. The phantom can also be used for patient plan-specific QA. The QA results over a period of 6 months are reported in this paper. The QA process was found to be simple, efficient and capable of simultaneously verifying several important parameters.

Original languageEnglish
Pages (from-to)5663-5674
Number of pages12
JournalPhysics in medicine and biology
Issue number19
StatePublished - 2009


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