Abstract: Time consuming calibration of a multi-element x-ray detector for an x-ray computed tomography machine that has multi-sample rate capabilities is reduced by determining through the use of air-scans, a scalar relationship between sensitivity of detector elements as a function of sampling rate. This scalar relationship is in vector form and may be applied to independently obtain calibration vectors at a base scan rate to provide effective calibration vectors at a variety of scan rates without the need for time consuming daily calibration scans at each of those sample rates.

Abstract: The present invention is, in one embodiment, a method for determining tracking control parameters for positioning an x-ray beam of a computed tomography imaging system having a movable collimator positionable in steps and a detector array including a plurality of rows of detector elements. The method includes steps of obtaining detector samples at a series of collimator step positions while determining a position of a focal spot of the x-ray beam; determining a beam position for each detector element at each collimator step utilizing the determined focal spot positions, a nominal focal spot length, and geometric parameters of the x-ray beam, collimator, and detector array; and determining a calibration parameter utilizing information so obtained.

Abstract: Time consuming calibration of a multi-element x-ray detector for an x-ray computed tomography machine that has multi-sample rate capabilities is reduced by determining through the use of air-scans, a scalar relationship between sensitivity of detector elements as a function of sampling rate. This scalar relationship is in vector form and may be applied to independently obtain calibration vectors at a base scan rate to provide effective calibration vectors at a variety of scan rates without the need for time consuming daily calibration scans at each of those sample rates.

Abstract: The present invention is, in one embodiment, a method for determining tracking control parameters for positioning an x-ray beam of a computed tomography imaging system having a movable collimator positionable in steps and a detector array including a plurality of rows of detector elements. The method includes steps of obtaining detector samples at a series of collimator step positions while determining a position of a focal spot of the x-ray beam; determining a beam position for each detector element at each collimator step utilizing the determined focal spot positions, a nominal focal spot length, and geometric parameters of the x-ray beam, collimator, and detector array; and determining a calibration parameter utilizing information so obtained.

Abstract: Methods and apparatus for detecting cell to cell variation to ensure that the maximum allowable channel to channel variation is not exceeded are described. In one embodiment, an algorithm is periodically executed to measure the relative gains in the channels. The gains are measured, for example, by recording the signal from an air scan and normalizing to a common reference. Part of the normalization process includes accounting for the non uniformity of the x-ray beam, for example, the heel effect. It is assumed that the x-ray flux profile in z is slowly changing in the x-direction and is obtained by low pass filtering in x. The normalized values are then compared to a predetermined specification. If any particular cell is not within the specification parameters, then the module in which such cell resides may be replaced. In addition to measuring gain variation and comparing it to a specification, a trending analysis also may be performed.

Abstract: Methods and apparatus for calibration simplification in a computed tomography (CT) system are described. In one embodiment, the CT system utilizes calibration values from a first scan type, or mode of operation, to determine calibration values for at least a second scan type. As a result, the time required to perform calibration of the CT system is reduced.

Abstract: The present invention is, in one embodiment, a method for determining tracking control parameters for positioning an x-ray beam of a computed tomography imaging system having a movable collimator positionable in steps and a detector array including a plurality of rows of detector elements. The method includes steps of obtaining detector samples at a series of collimator step positions while determining a position of a focal spot of the x-ray beam; determining a beam position for each detector element at each collimator step utilizing the determined focal spot positions, a nominal focal spot length, and geometric parameters of the x-ray beam, collimator, and detector array; and determining a calibration parameter utilizing information so obtained.

Abstract: The present invention comprises a system and method for correcting for z-slope variations in detector cell outputs represented by data obtained by a scan in a CT system. According to one aspect of the invention, a final error factor, based upon a combination of a correction factor and an initial error factor, is applied to the data. The correction factor having a computational complexity independent of the order of correction desired. The present invention transfers all of the computational complexity of z-slope correction to a calibration process, thereby improving the computational speed and efficiency of producing an accurate image based on the scan data. In another aspect, the present invention improves image quality by providing a correction factor comprising a plurality of channel correction factors, where each of the plurality of channels is the center channel for a corresponding moving segment used to respectively determine each of the channel correction factors.

Abstract: The present invention comprises a system and method for correcting for z-slope variations in detector cell outputs represented by data obtained by a scan in a CT system. According to one aspect of the invention, a final error factor, based upon a combination of a correction factor and an initial error factor, is applied to the data. The correction factor having a computational complexity independent of the order of correction desired. The present invention transfers all of the computational complexity of z-slope correction to a calibration process, thereby improving the computational speed and efficiency of producing an accurate image based on the scan data. In another aspect, the present invention improves image quality by providing a correction factor comprising a plurality of channel correction factors, where each of the plurality of channels is the center channel for a corresponding moving segment used to respectively determine each of the channel correction factors.

Abstract: Methods and apparatus for dose reduction in a computed tomography (CT) system are described. In one embodiment, the CT system includes a configurable multislice detector array and an adjustable source collimator. The detector array includes a photodiode cell array optically coupled to a scintillator array. The photodiode array includes a plurality of photodiodes arranged in rows and columns that may be combined to collect slice data from a number of inner and outer slices. The CT system also includes an x-ray source and a collimator. The x-ray source generates an x-ray beam that is collimated by the collimator to define the thickness of each outer slice. In operation, an operator determines the quantity and thickness of inner slices and the thickness of each outer slice. After altering the detector and collimator configuration, as defined by an operator, slice data for each inner slice and each outer slice is gathered.