Abstract: An apparatus for cone beam computed tomography of lower leg portions of a patient has a radiation source and a source transport actuable to move the source along an arcuate source path within a housing, from one side of a circumferential gap to the other and has a radius R2 about a center. A housing is provided for placement of the patient's foot. A digital radiation detector has a detector transport actuable to move the detector along an arcuate detector path within the housing, the detector path having a radius R1 about the center and concentric with the source path, wherein R1 is less than R2, and wherein the detector path extends from one side of the pedestal indent to the other. A gap closure apparatus is movable to a position that continues the detector path across the circumferential gap and encloses the detector path.

Abstract: Acquisition techniques for dual energy (DE) chest imaging system. Technique factors include the added x-ray filtration, kVp pair, and the allocation of dose between low- and high-energy projections, with total dose equal to or less than that of a conventional chest radiograph. Factors are described which maximize lung nodule detectability as characterized by the signal difference to noise ratio (SDNR) in DE chest images. kVp pair and dose allocation are described using a chest phantom presenting simulated lung nodules and ribs for thin, average, and thick body habitus. Low- and high-energy techniques ranged from 60-90 kVp and 120-150 kVp, respectively, with peak soft-tissue SDNR achieved at [60/120] kVp for patient thicknesses and levels of imaging dose. A strong dependence on the kVp of the low-energy projection was observed.

Abstract: A method for obtaining a 3-D image. An initial volume image is obtained of a subject wherein the subject is stationary and in a first pose. One or more 2-D images of the subject are obtained as the subject is moving between the first pose and a second pose. An endpoint volume image of the subject with the subject stationary and in the second pose is obtained. At least the initial volume image is modified according to the one or more obtained 2-D images to form at least one intermediate volume image that is representative of the subject's position between the first and second pose. The at least one intermediate volume image can be displayed.

Abstract: An apparatus for cone beam computed tomography of an extremity has a digital radiation detector and a first device to move the detector along a circular detector path extending so that the detector moves both at least partially around a first extremity of the patient and between the first extremity and a second, adjacent extremity. The detector path has radius R1 sufficient to position the extremity approximately centered in the detector path. There is a radiation source with a second device to move the source along a concentric circular source path having a radius R2 greater than radius R1, radius R2 sufficiently long to allow adequate radiation exposure of the first extremity for an image capture by the detector. A first circumferential gap in the source path allows the second extremity to be positioned in the first circumferential gap during image capture.

Abstract: Methods are provided for cardiac gating of multiple-energy projection radiographic imaging utilizing an apparatus that measures the patient's peripheral blood perfusion. The choice of methods is dependant on the patient's heart rate and the delays inherent in the imaging system. A first method allows for imaging during the diastole period of the current cardiac cycle. A second method provides an implemented delay to acquire the image during the diastole period of a subsequent cardiac cycle. The use of the apparatus that measures the patient's peripheral blood perfusion allows for an efficient and convenient means of cardiac gating while avoiding occlusion of diagnostically important anatomy.

Abstract: Acquisition techniques for dual energy (DE) chest imaging system. Technique factors include the added x-ray filtration, kVp pair, and the allocation of dose between low- and high-energy projections, with total dose equal to or less than that of a conventional chest radiograph. Factors are described which maximize lung nodule detectability as characterized by the signal difference to noise ratio (SDNR) in DE chest images. kVp pair and dose allocation are described using a chest phantom presenting simulated lung nodules and ribs for thin, average, and thick body habitus. Low- and high-energy techniques ranged from 60-90 kVp and 120-150 kVp, respectively, with peak soft-tissue SDNR achieved at [60/120] kVp for patient thicknesses and levels of imaging dose. A strong dependence on the kVp of the low-energy projection was observed.

Abstract: A method is disclosed for resolving misregistration errors resulting from dual energy double-shot projection radiographic image acquisition. The method involves an iterative multi-scale, multi-resolution registration process that corrects misregistration errors progressively at scales ranging from bulk anatomical drift down to smaller scale motion such as that of fine pulmonary vasculature. The method may be incorporated as part of a dual energy image processing chain to create dual energy images with improved image quality and diagnostic performance.

Abstract: Methods are provided for cardiac gating of multiple-energy projection radiographic imaging utilizing an apparatus that measures the patient's peripheral blood perfusion. The choice of methods is dependant on the patient's heart rate and the delays inherent in the imaging system. A first method allows for imaging during the diastole period of the current cardiac cycle. A second method provides an implemented delay to acquire the image during the diastole period of a subsequent cardiac cycle. The use of the apparatus that measures the patient's peripheral blood perfusion allows for an efficient and convenient means of cardiac gating while avoiding occlusion of diagnostically important anatomy.

Abstract: The invention provides a method and imaging system for operating imaging computed tomography using a radiation source and a plurality of detectors to generate an image of an object. The method includes: defining a desired image characteristics; and performing calculations to determine the pattern of fluence to be applied by the radiation source, to generate said desired image quality or characteristics. Then, the radiation source is modulated, to generate the intended pattern of fluence between the beam source and the object to be imaged. The desired image characteristics can comprise at least one of desired levels of contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR), and may provide at least one of: desired image quality in at least one defined region of interest; and at least one desired distribution of said image quality.

Abstract: Artifacts 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 images 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 tumor is in the correct position when the radiation is delivered.

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: A system for obtaining coordinate data of a source and detector instrument are described. The system includes a marker assembly having a plurality of markers with a particular geometry, and an energy source for targeting the plurality of markers with energy packets. The system further includes a detector for detecting energy packets after the plurality of markers have interacted therewith, and an image device for forming image data of the plurality of markers from the energy packets detected by the detector. A calibration module for utilizes the particular geometry of the plurality of markers and the image data to non-iteratively determine coordinate data.

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 radiation therapy system that includes a radiation source that moves about a path and directs a beam of radiation towards an object and a cone-beam computer tomography system. The cone-beam computer tomography system includes an x-ray source that emits an x-ray beam in a cone-beam form towards an object to be imaged and an amorphous silicon flat-panel imager receiving x-rays after they pass through the object, the imager providing an image of the object. A computer is connected to the radiation source and the cone beam computerized tomography system, wherein the computer receives the image of the object and based on the image sends a signal to the radiation source that controls the path of the radiation source.