Abstract: The present invention refers to 3D rotational X-ray imaging systems for use in computed tomography (CT) and, more particularly, to a fast, accurate and mathematically robust calibration method for determining the effective center of rotation (I) in not perfectly isocentric 3D rotational C-arm systems and eliminating substantially circular ring artifacts (RA) which arise when using such a CT scanner system for acquiring a set of 2D projection images of an object of interest to be three-dimensionally reconstructed.

Abstract: According to an exemplary embodiment a targeting method for targeting a first object from an entry point to a target point in an object (110) under examination is provided, wherein the method comprises selecting a two-dimensional image (301) of the object under examination depicting the entry point (305) and the target point (303) and determining a planned path (304) from the entry point to the target point, wherein the planned path has a first direction. Furthermore, the method comprises recording data representing a fluoroscopic image of the object under examination, wherein the fluoroscopic image is recorded under a second direction so that a normal of the image coincide with the first direction and determining whether the first object is on the determined planned path based on shape and/or position of the projection of the first object in the fluoroscopic image.

Abstract: The present invention refers to 3D rotational X-ray imaging systems for use in computed tomography (CT) and, more particularly, to a fast, accurate and mathematically robust calibration method for determining the effective center of rotation (I) in not perfectly isocentric 3D rotational C-arm systems and eliminating substantially circular ring artifacts (RA) which arise when using such a CT scanner system for acquiring a set of 2D projection images of an object of interest to be three-dimensionally reconstructed.

Abstract: It is described a gain calibration for a two-dimensional X-ray detector (315), in which the gain coefficients for scattered radiation (307b) and direct radiation (307a) are measured or estimated separately. A weighed average may be applied on the appropriate scatter fraction. The scatter fraction depending gain calibration method produces less ring artifacts in X-ray images as compared to known gain calibration methods, which do not take into account the fraction of scattered radiation reaching the X-ray detector (315).

Abstract: Method and apparatus are disclosed for treating a non-continuous particle beam produced by an accelerator in order to irradiate a target volume, wherein an irradiation spot located in the target volume is formed from this beam, and wherein the location of the irradiation spot is controlled by location controlling elements. The setting of the location controlling elements may take place in between subsequent particle bunches of the beam, for example.

Abstract: Prior to an intervention, a 3D rotational scan is acquired (at block 10) in respect of a body volume and reconstructed. In addition, three-dimensional image data in respect of the body volume is acquired (at block 12) using another modality, such as computerised tomography (CT) or magnetic resonance (MR), reconstructed, and prepared for visualisation. During the actual intervention, live two-dimensional fluoroscopic images are acquired (at block 14), using the imaging system employed to acquire the 3D rotational scan, and processed for visualisation.

Abstract: According to an exemplary embodiment a targeting method for targeting a first object from an entry point to a target point in an object (110) under examination is provided, wherein the method comprises selecting a two-dimensional image (301) of the object under examination depicting the entry point (305) and the target point (303) and determining a planned path (304) from the entry point to the target point, wherein the planned path has a first direction. Furthermore, the method comprises recording data representing a fluoroscopic image of the object under examination, wherein the fluoroscopic image is recorded under a second direction so that a normal of the image coincide with the first direction and determining whether the first object is on the determined planned path based on shape and/or position of the projection of the first object in the fluoroscopic image.

Abstract: An imaging system including an artifact reducer arranged to correct for a ring-shaped artifact in a three-dimensional reconstructed volume. The artifact reducer includes a first stage correction arranged to eliminate structured noise of an output screen of an image intensifier of an X-ray imaging apparatus using a first corrective image. A raw image of a patient is first processed with the first corrective image. The gain-corrected images are forwarded to an image deformation correction where a suitable unwarping function performed. The gain-corrected unwarped images are then made available to a second stage gain correction where a second corrective image is applied resulting in a final set of images with a substantially reduced ring-shaped artifact. The final set of images is made available to an image reconstructor arranged for further processing of the final set of images, the result thereof being visualized on a computer monitor for inspection purposes.

Abstract: It is described a gain calibration for a two-dimensional X-ray detector (315), in which the gain coefficients for scattered radiation (307b) and direct radiation (307a) are measured or estimated separately. A weighed average may be applied on the appropriate scatter fraction. The scatter fraction depending gain calibration method produces less ring artifacts in X-ray images as compared to known gain calibration methods, which do not take into account the fraction of scattered radiation reaching the X-ray detector (315).

Abstract: Method and apparatus are disclosed for treating a non-continuous particle beam produced by an accelerator in order to irradiate a target volume, wherein an irradiation spot located in the target volume is formed from this beam, and wherein the location of the irradiation spot is controlled by location controlling elements. The setting of the location controlling elements may take place in between subsequent particle bunches of the beam, for example.

Abstract: A method for generating a set of kernels for convolution error compensation of a projection image of a physical object recorded by an imaging system comprises calculating the set of kernels in such a way that for each pixel of the projection image an asymmetric scatter distribution for error compensation is calculated representing a X-ray scatter originating along a ray from an X-ray source to the pixel.

Abstract: Prior to an intervention, a 3D rotational scan is acquired (at block 10) in respect of a body volume and reconstructed. In addition, three-dimensional image data in respect of the body volume is acquired (at block 12) using another modality, such as computerised tomography (CT) or magnetic resonance (MR), reconstructed, and prepared for visualisation. During the actual intervention, live two-dimensional fluoroscopic images are acquired (at block 14), using the imaging system employed to acquire the 3D rotational scan, and processed for visualisation.

Abstract: An artifact correcting image reconstruction apparatus includes a reconstruction processor (70) that reconstructs acquired projection data (60) into an uncorrected reconstructed image (74). A classifying processor (78) classifies pixels of the uncorrected reconstructed image (74) at least into high, medium, and low density pixel classes. A pixel replacement processor (88) replaces pixels of the uncorrected reconstructed image (74) that are of the high density and low density classes with pixel values of the low density pixel class to generate a synthetic image (90). A forward projecting processor (94) forward projects the synthetic image (90) to generate synthetic projection data (96). A projection replacement processor (100, 110) replaces acquired projection data (60) contributing to the pixels of the high density class with corresponding synthetic projection data (96) to generate corrected projection data (112).

Abstract: An artifact correcting image reconstruction apparatus includes a reconstruction processor (70) that reconstructs acquired projection data (60) into an uncorrected reconstructed image (74). A classifying processor (78) classifies pixels of the uncorrected reconstructed image (74) at least into high, medium, and low density pixel classes. A pixel replacement processor (88) replaces pixels of the uncorrected reconstructed image (74) that are of the high density and low density classes with pixel values of the low density pixel class to generate a synthetic image (90). A forward projecting processor (94) forward projects the synthetic image (90) to generate synthetic projection data (96). A projection replacement processor (100, 110) replaces acquired projection data (60) contributing to the pixels of the high density class with corresponding synthetic projection data (96) to generate corrected projection data (112).

Abstract: The invention relates to an imaging system (15) comprising artifact reduction means (20) arranged to correct for a ring-shaped artifact in the three-dimensional reconstructed volume. The artifact reduction means (20) comprises a first stage correction means (21) arranged to eliminate the structured noise of the output screen of the image intensifier of an X-ray imaging apparatus (10) using a first corrective image. Preferably, the first corrective image (21a) is pre-calculated and is stored in a suitable memory unit of a computer (not shown). A raw image of the patient is first processed with the first corrective image (21a). The thus obtained gain-corrected image is forwarded to an image deformation correction means (23), where a suitable unwarping function (23a) is being pre-stored.

Abstract: A computed-tomography system comprises a data-processing system arranged to receive attenuation profiles for respective orientations. A lowest representative noise level of the individual attenuation profiles is determined. The attenuation profiles are filtered in dependence of said lowest representative noise level. In particular it is achieved that the filtered attenuation profiles have the lowest maximum noise level among the received attenuation profiles.

Abstract: A computed-tomography system comprises a data-processing system arranged to receive attenuation profiles for respective orientations. A lowest representative noise level of the individual attenuation profiles is determined The attenuation profiles are filtered in dependence of said lowest representative noise level. In particular it is achieved that the filtered attenuation profiles have the lowest maximum noise level among the received attenuation profiles.

Abstract: The size of a detail of an object is derived from a data set of data values relating to the object. The data set assigns the data values to positions in a multidimensional space. A direction is selected in the multidimensional space. The spatial resolution of the data set is higher in the selected direction as compared to the spatial resolution in other directions. The size of the detail is derived from data values in the selected direction. The selected direction can extend along the line of intersection which intersects a scanning plane in which the data values are acquired and a transverse plane extending at right angles to the longitudinal axis of the detail. The data values can be acquired an X-ray computed tomography imaging system, a magnetic resonsance imaging system, or a 3D ultrasound imaging system.

Abstract: A cross-sectional distribution along a cutting plane is derived from an object data set of data values. The cross-sectional distribution comprises density values. The density values are calculated from data values of the object data set in positions outside the cutting plane. The object data set represents an object to be examined and is, for example, acquired by way of volumetric computed tomography or magnetic resonance imaging. For example, the density values of the cross-sectional distribution are calculated by local (slab) MIP or mIP or by interpolation.

Abstract: The invention relates to a computer tomography apparatus in which the scanning trajectory is shaped as a helix and a conical radiation beam traverses the examination zone. According to the invention, the dimension of the detector window (or the part thereof which is used for the reconstruction) is a factor of 3, 5, 7 . . . larger than the distance between neighboring turns of the helix. Using this geometry, each voxel in the examination zone is irradiated exactly from an angular range of 3&pgr;, 5&pgr;, 7&pgr; . . . when it traverses the cone beam. Such data acquisition yields an improved image quality.