IMAGERS IN RADIATION THERAPY ENVIRONMENT
FIG5B is a diagram illustrating MV beam pulses being synchronous with the kV image readout
In some embodiments, the above "band" artifact problem may be addressed by configuring the line readout of the imager 200 so that it is synchronized with the treatment beam pulses. FIG5B is a diagram illustrating MV beam pulses being synchronous with the kV image readout. As shown in the figure, the readout of the kV image signals is synchronized with the treatment beam pulses, so that there are always twelve scatter pulses (from the treatment beams) between corresponding lines of two consecutive image frames. For example, there are twelve scatter pulses between the readout of line 289 in the kV-FRAME N, and the readout of line 289 (i.e., the same line) in the KV-FRAME N+1. There are also twelve scatter pulses between the readout of line 654 in the kV-FRAME N, and the readout of line 654 in the KV-FRAME N+1. Accordingly, the imager always integrates twelve scatter pulses from the treatment beams between two consecutive image frames for each of the pixel lines. As a result, the heights 562 of the kV frame lines shown in the figure (representing the amount of MV scatter signal received in different lines of the imager 200) are the same, thereby eliminating the band artifacts.
diagram
562
heights
12
gantry
289
line
654
line
['9. The imager of claim 6, 7 or 8, wherein the readout and control circuit is configured to perform signal readout for one or more lines of the imager during a treatment session when the treatment beam source is not delivering treatment energy, and to suspend signal readout for another line of the imager when the treatment beam source is delivering treatment energy.']