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:
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:
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:
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). The reconstruction processor (70) reconstructs the corrected projection data (112) into a corrected reconstructed image (120).
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. The resulting gain-corrected unwarped images are then made available to the second stage gain correction means (25), where a second corrective image (25a) is applied to the images resulting in a final set of images with a substantially reduced ring-shaped artifact. The final set of images is made available to the image reconstruction means (26) arranged for further processing of the final set of images, the result thereof being visualized on a computer monitor (30) for inspection purposes. The invention further relates to an X-ray imaging apparatus, a method for reducing an artifact in a three-dimensional reconstructed volume and a computer program.
Abstract:
A computer tomography device is provided with a reconstruction unit (1) for deriving brightness values of an image from density values. An image processing system (2) for deriving corrected brightness values from the brightness values of the image is arranged to calculate the variation of brightness values of the image in the radial direction and in the tangential direction. The image processing system is also arranged to calculate the deviation between the variation in the radial direction and the variation in the tangential direction and to derive corrected brightness values from brightness values of the image and the deviation.
Abstract:
Systems and methods are provided to perform efficient, automatic cyclotron initialization, calibration, and beam adjustment. A process is provided that allows the automation of the initialization of a cyclotron after overnight or maintenance imposed shutdown. In one embodiment, five independent cyclotron system states are defined and the transition between one state to another may be automated, e.g., by the control system of the cyclotron. According to these embodiments, it is thereby possible to achieve beam operation after shutdown with minimal manual input. By applying an automatic procedure, all active devices of the cyclotron (e.g., RF system, extraction deflectors, ion source) are respectively ramped to predefined parameters.
Abstract:
Systems and methods are provided to perform efficient, automatic cyclotron initialization, calibration, and beam adjustment. A process is provided that allows the automation of the initialization of a cyclotron after overnight or maintenance imposed shutdown. In one embodiment, five independent cyclotron system states are defined and the transition between one state to another may be automated, e.g., by the control system of the cyclotron. According to these embodiments, it is thereby possible to achieve beam operation after shutdown with minimal manual input. By applying an automatic procedure, all active devices of the cyclotron (e.g., RF system, extraction deflectors, ion source) are respectively ramped to predefined parameters.