Reduction of image lag in an x-ray detector panel

Abstract

A radiation therapy system is configured with fast readout of X-ray images with significantly reduced image lag. A reset phase is included in the process of acquiring an X-ray image to reduce image lag in a subsequently acquired X-ray image. During the reset phase, residual charge is concurrently transferred from multiple arrays of pixel detector elements in an X-ray detector panel. As a result, image lag present in a subsequent X-ray image is minimized or otherwise reduced.

We claim: 
     
         1 . A method of acquiring successive X-ray images of a target volume with an X-ray detector panel, the method comprising:
 determining that a first reset interval associated with a first X-ray image acquisition of the target volume is completed, wherein, during the first reset interval, at least a portion of residual charge is transferred from each pixel in a first array of pixels of the X-ray detector panel and at least a portion of residual charge is transferred from each pixel in a second array of pixels of the X-ray detector panel;   after determining that the first reset interval is completed, transferring first accumulated charge from each pixel in the first array of pixels of the X-ray detector panel to a readout device of the X-ray detector panel during a first readout interval, wherein residual charge remains in each pixel in the first array of pixels after transferring the first accumulated charge;   after the first readout interval, transferring second accumulated charge from each pixel in the second array of pixels of the X-ray detector panel to the readout device during a second readout interval, wherein residual charge remains in each pixel in the second array of pixels after transferring the second accumulated charge; and   during a second reset interval that follows the second readout interval and is associated with a second X-ray image acquisition of the target volume, concurrently transferring at least a portion of the residual charge from each pixel in the first array of pixels and at least a portion of the residual charge from each pixel in the second array of pixels.   
     
     
         2 . The method of  claim 1 , wherein, during the first reset interval:
 the portion of residual charge transferred from each pixel in the first array of pixels is transferred to a readout device of the X-ray detector panel; and   the portion of residual charge transferred from each pixel in the second array of pixels is transferred to the readout device of the X-ray detector panel.   
     
     
         3 . The method of  claim 1 , wherein the first accumulated charge and the second accumulated charge are associated with the second X-ray image acquisition of the target volume. 
     
     
         4 . The method of  claim 1 , wherein the first X-ray image acquisition and the second X-ray image acquisition are included in a cone-beam computed tomography process. 
     
     
         5 . The method of  claim 1 , wherein the first X-ray image acquisition and the second X-ray image acquisition are included in a digital tomosynthesis process. 
     
     
         6 . The method of  claim 1 , wherein the first X-ray image acquisition comprises acquiring a first X-ray projection image of the target volume and the second X-ray image acquisition comprises acquiring a second X-ray projection image of the target volume. 
     
     
         7 . The method of  claim 1 , further comprising, during the first reset interval, concurrently transferring at least a portion of the residual charge from each pixel in each array of pixels of the X-ray detector panel to the reference voltage associated with the readout device. 
     
     
         8 . The method of  claim 1 , wherein concurrently transferring at least the portion of the residual charge from each pixel in the first array of pixels and at least the portion of the residual charge from each pixel in the second array of pixels comprises electrically coupling each pixel in the second array of pixels to a reference voltage 
     
     
         9 . The method of  claim 8 , wherein the reference voltage is associated with the readout device. 
     
     
         10 . The method of  claim 1 , wherein the first array of pixels comprises a first row of pixels and the second array of pixels comprises a second row of pixels. 
     
     
         11 . The method of  claim 1 , wherein a start time of the first reset interval is selected to occur prior to a treatment beam pulse and an end time of the first reset interval is selected to occur after the treatment beam pulse. 
     
     
         12 . The method of  claim 7 , wherein a megavolt treatment beam is directed to the target volume during the treatment beam pulse. 
     
     
         13 . The method of  claim 1 , further comprising:
 prior to the first readout interval, preparing each pixel in the first array of pixels and each pixel in the second array of pixels to accumulate charge in response to incident X-rays; and   causing imaging X-rays to be directed to the X-ray detector panel.   
     
     
         14 . An apparatus comprising:
 an imaging X-ray source configured to direct imaging X-rays through a target volume and toward an X-ray detector panel; and   a controller configured to:   determine that a first reset interval associated with a first X-ray image acquisition of the target volume is completed, wherein, during the first reset interval, at least a portion of residual charge is transferred from each pixel in a first array of pixels of the X-ray detector panel and at least a portion of residual charge is transferred from each pixel in a second array of pixels of the X-ray detector panel;   after determining that the first reset interval is completed, transfer first accumulated charge from each pixel in the first array of pixels of the X-ray detector panel to a readout device of the X-ray detector panel during a first readout interval, wherein residual charge remains in each pixel in the first array of pixels after transferring the first accumulated charge;   after the first readout interval, transfer second accumulated charge from each pixel in the second array of pixels of the X-ray detector panel to the readout device during a second readout interval, wherein residual charge remains in each pixel in the second array of pixels after the second accumulated charge is transferred; and   during a second reset interval that follows the second readout interval and is associated with a second X-ray image acquisition of the target volume, concurrently transfer at least a portion of the residual charge from each pixel in the first array of pixels and at least a portion of the residual charge from each pixel in the second array of pixels.   
     
     
         15 . The apparatus of  claim 1 , wherein the first array of pixels comprises a first row of pixels of the X-ray detector panel and the second array of pixels comprises a second row of pixels of the X-ray detector panel. 
     
     
         16 . The apparatus of  claim 14 , wherein a start time of the second reset interval is selected to occur prior to a treatment beam pulse and an end time of the second reset interval is selected to occur after the treatment beam pulse. 
     
     
         17 . The apparatus of  claim 16 , further comprising linear accelerator configured to generate a megavolt treatment beam, wherein the megavolt treatment beam is directed to the target volume during the treatment beam pulse. 
     
     
         18 . The apparatus of  claim 14 , wherein the first accumulated charge and the second accumulated charge are associated with the second X-ray image acquisition of the target volume. 
     
     
         19 . The apparatus of  claim 14 , wherein the first X-ray image acquisition and the second X-ray image acquisition are included in a cone-beam computed tomography process. 
     
     
         20 . The apparatus of  claim 14 , wherein the first X-ray image acquisition and the second X-ray image acquisition are included in a digital tomosynthesis process.