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Field-in-field technique with intrafractionally modulated junction shifts for craniospinal irradiation
Sue S Yom1, Erik K Frija, Anita Mahajan
1Division of Radiation Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Purpose:
To plan craniospinal irradiation with "field-in-field" (FIF) homogenization in combination with daily, intrafractional modulation of the field junctions, to minimize the possibility of spinal cord overdose.
Methods And Materials:
Lateral cranial fields and posterior spinal fields were planned using a forward-planned, step-and-shoot FIF technique. Field junctions were automatically modulated and custom-weighted for maximal homogeneity within each treatment fraction. Dose-volume histogram analyses and film dosimetry were used to assess results.
Results:
Plan inhomogeneity improved with FIF. Planning with daily modulated junction shifts provided consistent dose delivery during each fraction of treatment across the junctions. Modulation minimized the impact of a 5-mm setup error at the junction. Film dosimetry confirmed that no point in the junction exceeded the anticipated dose.
Conclusions:
Field-in-field planning and modulated junction shifts improve the homogeneity and consistency of daily dose delivery, simplify treatment, and reduce the impact of setup errors.
