Abstract: A radiotherapeutic apparatus employs a collimator (52) set below a radiation source (50) and is adapted to move along an arc (54) substantially centered on the radiation source (50). As it sweeps the arc, the collimator (52) is adjusted so as to define the appropriate shape of radiation beam. A continuous sweep over the patient avoids edge artefacts and localized accumulation of leakage.

Abstract: A candidate selection system that generates data-driven candidate selections of large populations of submitted résumés using common independent assessment variables and against desired qualities is described. A processor executing the candidate selection program is pre-programmed to include a listing of desired qualities that the ideal candidate for the position should possess. Each submitted résumé is reviewed and data input from the résumés is normalized to produce values representing weighted scores unique to the specific candidate and in terms of the sought-after desired dependant qualities.

Abstract: A linear accelerator comprises a series of accelerating cavities, adjacent pairs of which are coupled via coupling cavities, in which at least one coupling cavity comprises a rotationally asymmetric element that is rotateable thereby to vary the coupling offered by that cavity. A control means for the accelerator is also provided, adapted to control operation of the accelerator and rotation of the asymmetric element, arranged to operate the accelerator in a pulsed manner and to rotate the asymmetric element between pulses to control the energy of successive pulses. A beneficial way of doing so is to rotate the asymmetric element continuously during operation of the linear accelerator. Then, the control means need only adjust the phase of successive pulses so that during the brief period of the pulse, the asymmetric element is “seen” to be at the required position.

Abstract: An apparatus, method and software module for selecting phase-correlated images from the output of a scanner such as a cone beam CT scanner operates by collapsing the images derived from the series from two dimensions to one dimension by summing the intensities of pixels along a dimension transverse to the one dimension, producing a further image from a composite of the one-dimensional images obtained from images in the series, analysing the further image for periodic patterns, and selecting from the series images having like phase in that periodic pattern. If desired, a plurality of reconstructions can be derived at different phases. The analysis of the further image for periodic patterns can include comparing the one-dimensional images therein, to identify a movement of features in that dimension. This allows (inter alia) the accurate determination of the breathing cycle in a patient and a concomitant improvement in the quality of CT scans by using phase-correlated images.

Abstract: Artefacts in the reconstructed volume data of cone beam CT systems can be removed by the application of respiration correlation techniques to the acquired projection images. To achieve this, the phase of the patients breathing is monitored while acquiring projection images continuously. On completion of the acquisition, projection images that have comparable breathing phases can be selected from the complete set, and these are used to reconstruct the volume data using similar techniques to those of conventional CT. Any phase can be selected and therefore the effect of breathing can be studied. It is also possible to use a feature in the projection image(s) such as the patient's diaphragm to determine the breathing phase. This feature in the projection images can be used to control delivery of therapeutic radiation dependent on the: patient's breathing cycle, to ensure that the tumour is in the correct position when the radiation is delivered.

Abstract: A radiotherapy apparatus comprises a source of therapeutic radiation, a source of imaging radiation and a two-dimensional imager for the imaging radiation, a computing means for preparing tomography data from the output of the imager, the therapeutic source being controllable on the basis of feedback from the tomography data, wherein the computing means is arranged to prepare a plurality of intersecting sectional views from the output of the imager, akin to a portal image but with better contrast and the detail of a section rather than that of a projection. This is easier to interpret and visualise a series of sectional than a three dimensional view. Pixels of the images are the result of averaging a plurality of voxels arranged transverse to the section, typically orthogonal and linear. Typically, good results can be achieved using between 5 and 20 voxels. About 10 is suitable, ie between 7 and 15. There is a ideally a display means for showing the sectional views to an operator.

Abstract: A radiotherapeutic apparatus employs a collimator (52) set below a radiation source (50) and is adapted to move along an arc (54) substantially centred on the radiation source (50). As it sweeps the arc, the collimator (52) is adjusted so as to define the appropriate shape of radiation beam. A continuous sweep over the patient avoids edge artefacts and localised accumulation of leakage.

Abstract: A radiotherapy apparatus comprises a first collimator and a second collimator, the first collimator being a multi-leaf collimator, the second collimator comprising a plurality of slits having a width which is a fraction of the width of the leaves of the first collimator, the first and second collimators being aligned such that each slit of the second collimator is associated with a leaf of the first collimator. A first irradiation is made, during which the first collimator will define the outer edge of the irradiation pattern, and the second collimator will serve to narrow the effective width of each leaf of the first collimator. This narrowing is a simple function of the relative widths of the slits of the second collimator and the leaves of the first. This will leave gaps in between the slits of the second collimator, which can then be filled by moving one or more of the patient, first and second collimators, so as to irradiate an area omitted in the first irradiation.

Abstract: A collimator set for a radiotherapy apparatus comprises, in sequence, an aperture collimator, a multi-leaf collimator with a pair of opposing arrays of elongate leaves each moveable longitudinally in a Y direction, and a leaf edge collimator, the aperture collimator being adapted to collimate the beam in the X and Y direction to a first extent, and the leaf edge collimator being adapted to further collimate the extent of the beam in the Y direction to a second and therefore lesser extend. This means that to close a pair of opposing leaves, they are moved to their minimum separation, with the gap being convered by the leaf edge collimator. The MLC is after the aperture collimator, so in combination with thin leaves, the MLC leaves will project a much reduced leaf width at the isocentre of the radiotherapy apparatus and collimation of the radiation field by fractional leaf widths becomes unnecessary. A radiotherapy apparatus comprising a collimator set as defined above is also disclosed.

Abstract: A collimator for a therapeutic linear accelerator comprising first and second opposed arrays of individually longitudinally moveable elongate leaves, and a blocking element arranged transverse to the two arrays and moveable in that transverse direction, thereby to move into a gap between the tips of a leaf from the first array and a leaf from the second array. The blocking element and the two arrays can be in the same plane, thereby reducing the overall height of the device. As the tips of the leaves are usually profiled, it is preferred that the side edges of the blocking element are profiled to a complementary shape. The side edges of the leaves are usually non-vertical in order to allow for the divergence of the radiation beam. Each leaf will have a different angle. Accordingly, it is preferred that the tip of the blocking element has a variable angle, in order to match the angle of whichever leaf is adjacent.

Abstract: A collimator for a therapeutic linear accelerator comprising first and second opposed arrays of individually longitudinally moveable elongate leaves, and a blocking element arranged transverse to the two arrays and moveable in that transverse direction, thereby to move into a gap between the tips of a leaf from the first array and a leaf from the second array. The blocking element and the two arrays can be in the same plane, thereby reducing the overall height of the device. As the tips of the leaves are usually profiled, it is preferred that the side edges of the blocking element are profiled to a complementary shape. The side edges of the leaves are usually non-vertical in order to allow for the divergence of the radiation beam. Each leaf will have a different angle. Accordingly, it is preferred that the tip of the blocking element has a variable angle, in order to match the angle of whichever leaf is adjacent.

Abstract: Apparatus for treatment by radiotherapy, comprises a patient table, a directional radiation source directed generally toward the patient table, the table and source being movable relative to each other at least axially with respect to the table and rotationally around the axis, the source being directionally adjustable within at least a plane including the longitudinal axis of the table, and including means to correlate axial relative motion of the table and directional adjustment of the source. Thus, the source of such an apparatus can be rotated about the table to access the predetermined position along a series of cones centered on the predetermined position and of the variable angle. Thus, the apparatus effectively accesses the predetermined position via lines of latitude rather than longitude. It is preferred if the source is directionally adjustable across an included angle of at least 20°, preferably more than 30°.