| Popis: |
In order to use negative pions for the treatment of large deep‐seated tumors in radiotherapy, it is necessary to produce depth‐dose distributions tailored to specific shapes. We present here a method of beam shaping which utilizes a fluid‐filled piston having a programmable, computer‐controlled, time‐dependent thickness. The fluid alters the residual range of the pions such that predetermined depth‐dose distributions can be obtained. Changing from one distribution to another can be accomplished simply and rapidly without access to the treatment room. Depth‐dose distributions which are flat over a range in depth up to 10 cm have been produced. Distributions tailored to produce flat ‘‘effective dose’’ versus depth have also been obtained. |
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