Accommodation of couch constraints for coplanar intensity modulated radiation therapy

Jurgen Meyer, John A. Mills, Olivier C.L. Haas, Keith J. Burnham, Elizabeth M. Parvin

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20 Citations (Scopus)


Purpose: Three treatment couches, henceforth referred to as the standard, the variable standard and the C-arm couch, each based on a different supporting frame system, were investigated for their suitability for the delivery of a high number of coplanar beams (≥5) as may be required for intensity-modulated radiation therapy treatments. Materials and methods: A number of equispaced beam arrangements (five to nine) were examined in combination with two circular target sizes (∅6 and ∅10 cm) at different locations within an elliptical body on the investigated couches, resulting in 70 different plans per couch. A rule based advisory system determined possible intersections of the beam paths with the supporting frames of the respective treatment couch and suggested a suitable constellation for the supporting frames. In cases of intersection, a beam–couch collision was eliminated by minimal rotation of the beams from the initial equispaced beam arrangement. To investigate the effect of a rotation of the posterior-oblique beams for five, seven and nine initially equispaced beams by an angle of 10°, a prostate plan was generated and compared with equispaced beam arrangement. Results: Initial beam paths intersected with the standard couch in 63% of the plans, necessitating a rotation of one or two beams. It was necessary to modify the beam angles in 34% of the cases on the variable standard couch to avoid an intersection of the beams with the couch. All the plans would have been delivered satisfactorily on the C-arm couch without a rotation of beams. Simulation studies showed that the dose distribution for a prostate treatment could be affected significantly, but not detrimentally, by the rotation of the two posterior-oblique beam orientations by an angle of 10°.
Original languageEnglish
Pages (from-to)23-32
JournalRadiotherapy and Oncology
Issue number1
Publication statusPublished - Oct 2001

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  • Intensity-modulated radiotherapy
  • Treatment couch
  • Beam–couch intersection
  • Equispaced beam angles
  • Coplanar


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