摘要:
If, in cardiac CT, the time window becomes shorter than the time required for a complete rotation of the gantry, the volume that can be reconstructed becomes small due to the non-existence of related pi-lines. According to an exemplary embodiment of the present invention, an examination apparatus is provided which generates a radiation beam oscillating in z-direction with an oscillation frequency higher than the rotational frequency of the source. This may provide for an exact image reconstruction of large volumes.
摘要:
A computer tomography apparatus (100) for examination of an object of interest (107), the computer tomography apparatus (100) comprising a first electromagnetic radiation source (104) adapted to emit electromagnetic radiation to an object of interest (107), a second electromagnetic radiation source (203) adapted to emit electromagnetic radiation to the object of interest (107), at least one detecting device (108) adapted to detect electromagnetic radiation generated by the first electromagnetic radiation source (104) and by the second electromagnetic radiation source (203) and scattered on the object of interest (107), and a determination unit (118) adapted to determine structural information concerning the object of interest (107) based on an analysis of detecting signals received from the at least one detecting device (108).
摘要:
The invention relates to a method and a system for the reconstruction of an object function (f(x)) based on projections acquired during the motion of a radiation source on a helical trajectory (17). The method is particularly suited for an n-PI+ acquisition which by definition completely comprises an n-PI and additionally some overscan data from the (n+2)−PI window. According to the method, two sets (Σ≧m, Σ≧m) of filtered projections are generated from the measuring values and separately back-projected to yield two absorption functions. The first absorption function (flf(x)) is based on contributions of Radon-planes with at most m intersections with the source trajectory (17), while the second absorption function (fhf(x)) is based on Radon-planes with more than m intersections with the source trajectory (17). The two absorption functions are added to yield the final absorption function (f(x)) of an object in the examination zone. In an approximative version of the method, the sets (Σ≧m, Σ≧m) of filtered projections are first added and then back-projected.
摘要:
The invention relates to a computer tomography method in which an examination area is passed through by a cone-shaped bundle of rays. The bundle of rays comes from a radiation source location which moves around the examination area on an overall trajectory. The overall trajectory consists of a first, closed partial trajectory, at least one second, closed partial trajectory and at least one third partial trajectory which connects the first and the at least one second partial trajectories to one another. Measured values which depend on the intensity in the bundle of rays on the other side of the examination area are acquired by means of a detector unit while the radiation source location is moving on the overall trajectory, and a CT image of the examination area is reconstructed from these measured values.
摘要:
A method and system to perform region-of-interest (ROI) reconstruction is provided, even if the original projection data are truncated. The reconstruction is performed on a superset of the ROI, including the ROI as well as other areas which are outside the scan field-of-view of the imaging system but still within the imaging bore.
摘要:
Method for influencing and/or detecting magnetic particles in a field of view. Selection coils/magnets generate a magnetic selection field and drive coils generate a magnetic drive field for moving a field-free point along a predetermined trajectory through the field of view, changing the magnetization of the magnetic material locally. The drive field comprises a time-dependent oscillating drive field current per drive field coil having one or more individual oscillating frequencies and one or more individual current amplitudes and being generated by a corresponding drive field voltage generated by a superposition of a number of drive field voltage components including a drive field voltage component per drive field coil, wherein a drive field voltage component corresponding to a drive field coil comprises one or more sub-components, each having an individual voltage amplitude and having the same individual oscillating frequency as the respective drive field current of said particular drive field coil.
摘要:
A scanning method and apparatus useful for correcting artifacts which may appear in a primary short circular CT scan are provided. A secondary helical scan performed on a stationary subject, or a secondary circular scan, may be used to correct for artifacts. The secondary scan may be performed with a smaller radiation dosage than the primary circular CT scan.
摘要:
The invention relates to a computed tomography method in which a periodically moving object is irradiated by a conical beam bundle. An nPi-relative movement is generated between a radiation source, which generates the conical beam bundle, and the object. During the nPi-relative movement, measured values are acquired, which depend on the intensity in the beam bundle on the other side of the object and from these measured values filter values are determined, which are divided into different groups. The filter values of at least one group are weighted in dependence on the movement of the object, wherein, when filter values of several groups are weighted, filter values of different groups are weighted differently in dependence on the movement of the object. Finally, a CT image of the object is reconstructed from the filter values.
摘要:
A computer tomography apparatus (100) for examination of an object of interest (107) comprising an electromagnetic radiation source (104) adapted to emit electromagnetic radiation to an object of interest (107), a detecting device (108) adapted to detect electromagnetic radiation generated by the electromagnetic radiation source (104) and passed through the object of interest (107), and a motion generation device (101, 119) adapted to move the electromagnetic radiation source (104) and the detecting device (108) with respect to the object of interest (107) along a first trajectory and along a second trajectory which differs from the first trajectory, wherein the second trajectory is selected in such a manner that electromagnetic radiation detected during performing the second trajectory provides data which complete mathematically incomplete data detected during performing the first trajectory to thereby allow a reconstruction of structural information concerning the object of interest (107).
摘要:
Image quality is an important feature for CT scanning, in particular for helical cone-beam CT scanning. By using projection data acquired at two different positions of the focal spot of the radiation beam and rebinning that projection data from a first geometry to a second geometry the two sub-sets of projection data are combined to one rebinned projection data set, thereby improving the radial resolution of the data set. Advantageously, according to an aspect of the present invention, a further rebinning may be performed, from the second geometry back to the first geometry, therefore resulting in a projection data set in the initial geometry with a higher radial resolution.