| 摘要 |
<p>Radiotherapy apparatus is disclosed, comprising a radiation source capable of emitting a beam of therapeutic radiation along a beam axis, collimation apparatus for delimiting the beam and comprising (i) a block of sufficient width to extend across the width of the beam, selectively movable into the beam from a first side of the beam axis, and (ii) an array of individually moveable elongate narrow leaves arranged side-by-side in a direction perpendicular to the beam, each being moveable longitudinally into the beam from a second and opposing side of the beam axis, in which there is no array of individually moveable elongate narrow leaves arranged side-by-side in a direction perpendicular to the beam moveable longitudinally into the beam from the first side of the beam axis. Thus, there is in effect a single bank of MLC leaves on one side of the aperture and a block collimator on the other. This is suitable for IMRT-based treatments. The block and the array of individually moveable elongate narrow leaves can be the only collimation apparatus in the head, offering weight reductions and height reductions relative to known radiation heads. The block can comprise an adjustable section defining its leading edge, capable of adjustment so as to vary the angle between the leading edge and the beam axis. This allows the leading edge of the block to be aligned to the local beam direction regardless of how far into the beam the block is positioned. This reduces the penumbra of the block and creates a better definition of the radiation field. Alternatively, the block can comprise a plurality of plates stacked in the direction of the beam axis and moveable relative to each other so that the leading edge of the thus-defined block is adjustable so as to vary the angle between the leading edge and the beam axis.</p> |
