| 摘要 |
A radiotherapy apparatus comprises a rotatable gantry, a source of therapeutic radiation 16 and a source of diagnostic radiation 22 rotationally spaced apart, at least one collimator, characterised by control means arranged to cause the apparatus to acquire images of a patient using the diagnostic radiation source, retain those images at least temporarily; subsequently, after further rotation of the gantry, select a retained image acquired when the source of diagnostic radiation was at a rotational position corresponding to the instantaneous rotational position of the source of therapeutic radiation, and control the beam relative to the patient using information derived from the selected image. An alternative apparatus is characterised by a reconstruction means arranged to obtain two-dimensional images of a patient using the source of diagnostic radiation, retain those images at least temporarily, apply a recency threshold to the retained images thereby to exclude images less recent than the threshold, select at least three such retained images meeting the recency threshold and reconstruct a CT volume or tomographic image using the apparatus, controlling the collimator using information derived from the CT volume. |
