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A stereotactic radiation therapy device for retinoblastoma using a noncircular collimator and intensity filter
Author(s) -
Cormack R. A.,
Kooy H. M.,
Bellerive M. R.,
Loeffler J. S.,
Petersen R. A.,
Tarbell N. J.
Publication year - 1998
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.598317
Subject(s) - collimator , imaging phantom , isocenter , optics , lens (geology) , dosimetry , retina , linear particle accelerator , retinoblastoma , stereotactic radiation therapy , physics , materials science , radiosurgery , radiation therapy , nuclear medicine , beam (structure) , medicine , radiology , biochemistry , chemistry , gene
The proximity of the lens to the retina makes the treatment of retinoblastoma a challenge for external beam radiation therapy. The ∼1 mm separation between the posterior edge of the lens and the anterior region of the retina causes a trade‐off between coverage of the entire retina and excessive dose to the lens. A stereotactic, LINAC based, lens sparing technique for treating retinoblastoma is presented. The technique uses noncoplanar arcs with the lens at isocenter. A special noncircular collimator blocks the lens but it also causes the dose distribution to vary across the retina. A fluence modulation filter is used to reduce the dose inhomogeneity across the target. The resulting dose distribution is roughly hemispheric, providing both anterior coverage of the retina and lens blocking unlike conventional techniques. The method used to develop the collimator and filter assembly is presented. Dosimetry of the assembly was carried out using radiochromic film, and the results were entered in a treatment planning system. The dose distribution as measured in a phantom is provided and compared to calculations.