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: The disclosed CT scanner comprises at least one source of X-rays; a detector array comprising a plurality of detectors; and an X-ray filter mask arrangement disposed between the source of X-rays and detector array so as to modify the spectra of the X-rays transmitted from the source through the mask to at least some of the detectors so that the X-ray spectra detected by at least one set of detectors is different from the X-ray spectra detected by at least one other set of detectors.

Abstract: An energy-sensitive computed tomography system is provided. The energy-sensitive computed tomography system includes an X-ray source configured to emit an X-ray beam resulting from electrons impinging upon a target material. The energy-sensitive computed tomography system also includes an object positioned within the X-ray beam. The energy-sensitive computed tomography system further includes a detector configured to receive a transmitted beam of the X-rays through the object. The energy-sensitive computed tomography system also includes a filter having an alternating pattern disposed between the X-ray source and the detector, the filter configured to facilitate measuring projection data that can be used to generate low-energy and high-energy spectral information.

Abstract: A source of pulsed radiation is coupled to a positionable filter. The positionable filter includes an element that produces an indication of a position of the filter. The source is configured to receive the indication of the position of the filter, and to regulate emission of a pulse of radiation based on the indication. A device includes an area including a material that alters a parameter of a beam of radiation that interacts with the material. The device is configured to move relative to a source of pulsed radiation. An element provides a signal to the source of pulsed radiation that indicates a position of the area relative to the source. The signal causes the source to trigger emission of a pulse at a time such that the emitted pulse is incident upon a portion of the area.

Abstract: A filter includes a plurality of filter plates for adjusting X-ray energy spectrum, a plurality of rails for fixedly supporting the filter plates, a plurality of cams which are respectively provided with a groove curve on a surface thereof, a driving wheel for driving the cams, and a plurality of link levers, each link lever being connected to one of the filter plates at one end and being mounted to an axis at an opposite end such that the link lever is rotatable about the axis, and each link lever being provided with a pin which is in cooperation with the groove curve of the corresponding cam so that the link lever proceeds with a reciprocating movement according to rotation of the corresponding cam to move the filter connected to it into or out of the X-ray passing space. The plurality of cams are respectively located at different sides of the driving wheel to move the filter plates into the X-ray passing space from different directions.

Abstract: An x-ray source (32) for performing energy discrimination within an imaging system (10) includes a cathode-emitting device (82) for emitting electrons and an anode (81) that has a target (80) whereupon the electrons impinge to generate an x-ray beam (93) with multiple x-ray quantity energy peaks (116 and 120). A method of performing energy discrimination in the imaging system (10) includes emitting the electrons. The x-ray beam (93) with the x-ray quantity energy peaks (116 and 120) is generated. The x-ray beam (93) is directed through an object (44) and is thereafter received. An x-ray image having multiple energy differentiable characteristics is generated in response to the x-ray beam (93) as received.

Abstract: The invention is directed to an x-ray flux management device that adaptively attenuates an x-ray beam to limit the incident flux reaching a subject and radiographic detectors in potentially high-flux areas while not affecting the incident flux and detector measurements in low-flux regions. While the invention is particularly well-suited for CT, the invention is also applicable with other x-ray imaging systems. In addition to reducing the required detector system dynamic range, the present invention provides an added advantage of reducing radiation dose.

Abstract: A filter capable of adjusting spectrum in multiple stages and that capable of attaining the reduction of size, as well as an X-ray imaging system having such a filter, are provided. The filter, which is for adjusting the spectrum of passing radiation, comprises a support plate having an aperture for passage therethrough of radiation, plural filter plates supported by the filter plate and having mutually different filter characteristics, and moving device for moving the plural filter plates selectively to a position to close the aperture and a position to open the aperture.

Abstract: The disclosed CT scanner comprises at least one source of X-rays; a detector array comprising a plurality of detectors; and an X-ray filter mask arrangement disposed between the source of X-rays and detector array so as to modify the spectra of the X-rays transmitted from the source through the mask to at least some of the detectors so that the X-ray spectra detected by at least one set of detectors is different from the X-ray spectra detected by at least one other set of detectors.

Abstract: A multi-energy imaging system and method for selectively generating high-energy X-rays and low-energy X-ray beams are described. A pair of optic devices are used, one optic device being formed to emit high X-ray energies and the other optic device being formed to emit low X-ray energies. A selective filtering mechanism is used to filter the high X-ray energies from the low X-ray energies. The optic devices have at least a first solid phase layer having a first index of refraction with a first photon transmission property and a second solid phase layer having a second index of refraction with a second photon transmission property. The first and second layers are conformal to each other.

Abstract: Disclosed are an apparatus and method of filtering a narrow band X-ray. The apparatus includes a micro filter array to configure a plurality of micro filters in an array, a filter array storing unit to store a filter table having information about an angle of each of the plurality of micro filters within the micro filter array, and a control unit to retrieve the filter table to ascertain the angle of each of the plurality of micro filters. The control unit also controls an angle between each of the plurality of micro filters and a panel supporting the plurality of micro filters to be the ascertained angle, and filters and output a received broadband polychromatic X-ray to be the narrow band X-ray.

Abstract: The invention is directed to an x-ray flux management device that adaptively attenuates an x-ray beam to limit the incident flux reaching a subject and radiographic detectors in potentially high-flux areas while not affecting the incident flux and detector measurements in low-flux regions. While the invention is particularly well-suited for CT, the invention is also applicable with other x-ray imaging systems. In addition to reducing the required detector system dynamic range, the present invention provides an added advantage of reducing radiation dose.

Abstract: Disclosed are an energy spectrum modulation apparatus, a material discrimination method and a device thereof, as well as an image processing method are disclosed, which can discriminate the material in large- and medium-sized objects such as cargo containers, air cargo containers, etc. by using X-rays having different energy levels. The energy spectrum modulation apparatus comprises a first energy spectrum modulation part for modulating a first ray having a first energy spectrum, and a second energy spectrum modulation part coupled to the first energy spectrum modulation part and for modulating a second ray having a second energy spectrum different from the first energy spectrum. The present invention can be used in the non-opening inspection for large-sized container cargo at places such as Customs, ports and airports.

Abstract: The present invention is directed to a method and apparatus of multi-energy data acquisition. An imaging system is also provided and includes a number of HF electromagnetic energy filters. The filters include at least a first and a second filter wherein the first filter is positioned in a path of HF electromagnetic energy when an HF electromagnetic energy source is energized to a first voltage and the second filter is positioned in the path of HF electromagnetic energy when the HF electromagnetic energy source is energized to a second voltage.

Abstract: The present invention is directed to a method and apparatus of multi-energy data acquisition. An imaging system is also provided and includes a number of HF electromagnetic energy filters. The filters include at least a first and a second filter wherein the first filter is positioned in a path of HF electromagnetic energy when an HF electromagnetic energy source is energized to a first voltage and the second filter is positioned in the path of HF electromagnetic energy when the HF electromagnetic energy source is energized to a second voltage.

Abstract: The invention relates to a beam filter (10) that can particularly be used in spectral CT-applications for producing a desired intensity profile of a radiation beam without changing its spectral composition. In a preferred embodiment, the beam filter (10) comprises a stack of absorbing sheets (111) that are separated by wedge-shaped spaces (112) and focused to a radiation source (1). Furthermore, the absorbing sheets have a varying width in direct ion of the radiation. Different fractions of the radiation source (1) area are therefore masked by the beam filter (10) at different points (A, B) on a detector area (2). The absorbing sheets preferably comprise a material that is highly absorbing for the radiation to be filtered.

Abstract: A small-sized filter unit of a simple structure, as well as an X-ray tube unit and an X-ray imaging system both having the filter unit, are implemented. A filter unit in a first aspect of the present invention comprises a filter plate, the filter plate having a first filter, a second filter disposed in a first direction with respect to the first filter and a third filter disposed in a second direction having a predetermined angle from the first direction with respect to the first filter, a guide plate having a guide frame for movement of the filter plate in the first and second directions, and a drive device for moving the filter plate.

Abstract: An apparatus and method of attenuating radiation includes oscillating at least one fluid having a radiation attenuating property between at least two chambers, incident to applied radiation. The radiation attenuating device includes at least two communicating adjacent chambers, at least one fluid having radiation attenuating properties moveable between the at least two chambers, and a control circuit configured to oscillate the at least one fluid between the chambers.

Abstract: An apparatus for use in a radiation procedure includes a radiation filter having a first portion and a second portion, the first and the second portions forming a layer for filtering radiation impinging thereon, wherein the first portion is made from a first material having a first x-ray filtering characteristic, and the second portion is made from a second material having a second x-ray filtering characteristic. An apparatus for use in a radiation procedure includes a first target material, a second target material, and an accelerator for accelerating particles towards the first target material and the second target material to generate x-rays at a first energy level and a second energy level, respectively.

Abstract: The present invention is directed to a method and apparatus of multi-energy data acquisition. An imaging system is also provided and includes a number of HF electromagnetic energy filters. The filters include at least a first and a second filter wherein the first filter is positioned in a path of HF electromagnetic energy when an HF electromagnetic energy source is energized to a first voltage and the second filter is positioned in the path of HF electromagnetic energy when the HF electromagnetic energy source is energized to a second voltage.

Abstract: A device (100; 200; 300; 400) comprising a sealed cavity (210) containing n volumes of fluids (80, 87; 220, 230; 320, 332; 420, 422, 430, 432) is described, where n is an integer and n?2. Each volume of fluid is substantially immiscible with every contiguous volume of fluid. The cavity is defined by an interior surface divided into n continuous areas (60, 170; 260, 270; 360, 362, 370; 460, 462, 470, 472), each continuous area corresponding to and being in contact with a respective one of the volumes of fluid. The wettability of each area is such that each volume of fluid preferentially adheres to the corresponding continuous area rather than any one of the continuous areas adjacent to the corresponding area.

Abstract: A method for routine monitoring and quality assurance of field asymmetry of high energy circular radiation beam producing equipment. The quality assurance process of field symmetry for devices such as stereotactic radiosurgery (SRS) systems is simplified by directly measuring the integration of the half-beam profile. The method of the invention provides that the field symmetry is obtained by positioning the tip of an ion chamber, with a collecting length approximately half the diameter of the beam, at the central axis of the beam, and rotating the ion chamber at varying angular positions, acquiring and comparing readings at desired angular positions. Each pair of readings from positions 180 degrees opposed from each other, are plugged into the equation, Asymmetry=2(R1?R2)/(R1+R2) to compute asymmetry.

Abstract: An X-ray imaging apparatus is disclosed. The apparatus includes a radiator housing, an X-ray tube, a source of X-rays and at least one filtration material disposed on the X-ray tube. The X-ray tube is rotatable about a longitudinal axis and is disposed at least partially within the radiator housing. The source of X-rays emits at least one X-ray beam at least partially through the X-ray tube. The X-ray beam exits the X-ray tube at an annular X-ray window. The filtration material at least partially covers a portion of the annular X-ray window. Rotation of the X-ray tube causes the X-ray beam to pass through a plurality of locations in the annular X-ray window and at least a portion of the X-ray beam is filtered by the filtration material.

Abstract: A respiration phantom that may be used to perform quality assurance on a radiation delivery system. The respiration phantom includes a human-like skeletal structure, at least one deformable component, and a respiration actuator. The deformable component is positionable at least partially internal to the human-like skeletal structure, has a shape resembling an organ of a human anatomy, and attenuates radiation substantially similarly to the organ of the human anatomy. The respiration actuator is positioned to deform the deformable component with a respiration-like motion.

Abstract: Devices and methods for implementing selective, or asymmetric, attenuation of an x-ray beam. In one example, a filter is provided that is substantially in the form of a wedge where some portions of the filter are thicker, and thus provide greater attenuation, than other, thinner portions of the filter. The filter is situated between the target surface of the anode and the x-ray subject so that x-rays generated by the target pass through the filter before reaching the x-ray subject. Specifically, the filter is oriented so that the thicker portion of the filter receives the higher intensity portion of the x-ray beam, while the thinner portion of the filter receives the relatively lower intensity portion of the x-ray beam. Thus, the gain profile of the x-ray beam is flattened so that the intensity, or flux, of the x-ray beam is relatively uniform throughout a substantial portion of the beam profile.

Abstract: The invention is directed to an x-ray flux management device that adaptively attenuates an x-ray beam to limit the incident flux reaching a subject and radiographic detectors in potentially high-flux areas while not affecting the incident flux and detector measurements in low-flux regions. While the invention is particularly well-suited for CT, the invention is also applicable with other x-ray imaging systems. In addition to reducing the required detector system dynamic range, the present invention provides an added advantage of reducing radiation dose.

Abstract: A narrow band x-ray filter can include: a substrate; and a sheaf of one or more reflection units stacked upon each other on the substrate. Each reflection unit can include: a first set of at least two discrete spacers on a respective underlying structures, a reflector disposed on the first set of spacers so as to form a void between the respective underlying structure and the reflector; and a first set of at least two discrete shims disposed on the first set of at least two spacers, each shim being at least substantially the same thickness as the reflector. A first device to produce a narrow band x-ray beam may include such a filter or an x-ray telescope. A second device to make an x-ray image of a subject may include the first device.

Abstract: An x-ray reflector may include: a substrate; a first layer formed on the substrate, the first layer including a relatively higher-Z material, where Z represents the atomic number; and a second layer formed on the first layer, the second layer including a relatively lower-Z material; at least one of the first layer and the second layer exhibiting a taper in an axial direction extending between a first end of the substrate and a second end of the substrate.

Abstract: A bowtie filter is constructed to have a fluidic envelope filled with attenuating fluid and a displacement insert that can present various x-ray attenuation profiles during a scan. The insert is designed to displace the attenuating fluid to achieve a denied attenuating or filtering profile. The insert can be rotated, twisted, moved, and otherwise contorted within the fluidic envelope as needed during the course of a scan. As the angle, position and shape of the zombie is changed, the x-ray profile of the filter changes. The insert may have a default shape when at rest, but can have its shape changed when external forces are placed thereon. As x-ray filtering needs change during the course of the scan, the insert can be compressed, stretched, and/or contorted to achieve additional filtering profiles.

Abstract: The present invention provides for an x-ray system and method using dynamic automated spatial modulation of an x-ray beam. The system includes an x-ray source transmitting a spatially modulated beam towards an object to be imaged, an x-ray detector receiving the beam and measuring a plurality of intensities across the beam, a beam processor controlling the beam intensity profile, and an image processor producing an output image signal. The detector produces a residual image based on at least the intensities measured at the detector. The beam intensity profile may be based on at least some of the following: (a) the residual image from the x-ray detector, (b) current beam intensities, (c) regions on interest in the image, and (d) predicted or measured object motion in the image. The system's output image is based on one or more of said residual image and said beam intensity signal.

Abstract: A radiation therapy system is provided having a radiation source for providing radiation for treating a patient, including treating skin cancer, wherein the radiation source features a filtering device that changes its filtering characteristic for filtering the radiation for treating the patient in response to a control signal. The filtering device includes two filters and a radiation blocker circumferentially arranged on a cylindrical member. The filtering characteristic is changed by rotating the filtering device in response to the control signal. The filtering device includes a driving unit for rotating the filtering device in response to the control signal in order to change its filtering characteristic, such as a motor with a gearing arrangement for coupling to a corresponding gearing arrangement on the filtering device. In this embodiment, the means for providing the radiation, i.e. the x-ray tube, is arranged inside the filtering device.

Abstract: In order to realize a filter that can make a fine spectrum adjustment in a wide rage and can be miniaturized, and to realize an X-ray imaging apparatus provided with the filter, a filter of the present invention is provided with plural filter plates that can form a layer crossing X-ray and adjusting means that adjusts a combination of filter plates forming the layer by individually moving the plural filter plates so as to come in and out the X-ray passing space. The plural filter plates are formed such that the thickness of each filter plate is successively doubled with the thinnest filter plate defined as a reference. The adjusting means has a pair of moving in/out mechanisms for moving, every its half number, the plural filter plates in and out from both sides of the X-ray passing space.

Abstract: A method and apparatus for tailoring the profile of an x-ray beam for radiographic imaging for a specific subject is disclosed. The invention includes a filter assembly having a pair of filters, each of which may be dynamically controlled by a motor assembly during data acquisition. The filters are positionable in the x-ray beam so as to shape the intensity profile of the x-ray beam. In one exemplary embodiment, the filters are dynamically positioned during CT data acquisition based on the shape of the subject. A method of determining the shape of the subject prior to CT data acquisition is also disclosed.

Abstract: A stackable rack may comprise: at least two rails, a cross-section of each rail having a shape resembling a staircase, first step portion of which represents a first surface upon which a reflector can be disposed; and a second step portion of which represents a second surface which can support another rail. A method of making a narrow band x-ray filter may comprise: providing a substrate; and stacking one or more reflection units in succession upon the substrate, each reflection unit including a rack (such as mentioned above) and a reflector held by the rack. An apparatus to produce a substantially narrow band x-ray beam may include such a filter. An apparatus to make an x-ray image of a subject may include: the apparatus to produce a substantially narrow band x-ray beam, e.g., as set forth above, and an x-ray detector arranged to receive the narrow band x-ray.

Abstract: A filter assembly for a computed tomographic imaging system includes first and second endplates at opposite ends of the filter assembly. Also provided is a first moveable subassembly that includes at least a first x-ray filter and which is configured to move along an axis perpendicular to the first endplate between the first the second endplates. A second moveable subassembly is also provided that includes at least a second x-ray filter. The second moveable subassembly is configured to move along an axis perpendicular to the second endplate between the first and second endplates. The first moveable subassembly and the second moveable subassembly are independently movable to provide at least a small bowtie x-ray filter, a large bowtie x-ray filter, a medium bowtie x-ray filter, a flat filter, and a closed position for a radiation source positioned in a fixed position relative to the filter assembly.

Abstract: Filters for EUV lithography, methods of manufacture thereof, and methods of filtering in an EUV lithography system are disclosed. The filter comprises a nanotube material layer sandwiched by two thin material layers that are highly transmissive and provide structural support for the nanotube material layer. The filter is supported on at least one side by a patterned structural support. The filter mitigates debris, provides spectral purity filtering, or both.

Abstract: An DPP EUV source is disclosed which may comprise a debris mitigation apparatus employing a metal halogen gas producing a metal halide from debris exiting the plasma. The EUV source may have a debris shield that may comprise a plurality of curvilinear shield members having inner and outer surfaces connected by light passages aligned to a focal point, which shield members may be alternated with open spaces between them and may have surfaces that form a circle in one axis of rotation and an ellipse in another. The electrodes may be supplied with a discharge pulse shaped to produce a modest current during the axial run out phase of the discharge and a peak occurring during the radial compression phase of the discharge. The light source may comprise a turbomolecular pump having an inlet connected to the generation chamber and operable to preferentially pump more of the source gas than the buffer gas from the chamber.

Abstract: A spectrum measuring apparatus that includes an extinction member for decreasing a light intensity from an EUV light source, a spectrum member for extracting light with a desired wavelength band from the decreased intensity light and a detector for detecting a light intensity of the light with a desired wavelength band is disclosed. Then, a spectrum intensity distribution (spectrum) is obtained by (a) a plural opening is located in the extinction member, and the light from the EUV light source passes through the plural opening at the same time, or (b) the detector detects the light volume of the light with a desired wavelength band as thermal energy.

Abstract: An x-ray source (32) for performing energy discrimination within an imaging system (10) includes a cathode-emitting device (82) emitting electrons and an anode (81) that has a target (80) whereupon the electrons impinge to generate an x-ray beam (93) with multiple x-ray quantity energy peaks (116 and 120). A method of performing energy discrimination in the imaging system (10) includes emitting the electrons. The x-ray beam (93) with the x-ray quantity energy peaks (116 and 120) is generated. The x-ray beam (93) is directed through an object (44) and is received. An x-ray image having multiple energy differentiable characteristics is generated in response to the x-ray beam (93).

Abstract: Particles emitted by a radiation source, and moving from the radiation source towards a processing system for processing the radiation from the radiation source, are filtered out of radiation propagating through a predetermined cross section of the radiation as emitted by the radiation source by a filter system. The filter system includes a plurality of foils and a transporter for transporting the foils along a trajectory which extends within the beam so that the foils intercept the particles within the beam. The transporter is arranged to transport the foils by a substantially translatory movement of the foils along at least a part of the trajectory.

Abstract: The present invention is directed to a method and apparatus for CT data acquisition using a rotatable pre-subject filter having more than one filtering profile to control radiation exposure to a subject. The filter is caused to rotate by a motor and bearing assembly and has one profile used to filter radiation when the radiation source is positioned above a subject and another profile that is used to filter radiation when the radiation source is positioned at a side of the subject.

Abstract: An X-ray distribution adjusting filter apparatus for supplying a desired X-ray intensity distribution or adjusting the X-ray distribution to a desired profile, the bowtie filter as the X-ray distribution adjusting filter apparatus has a fixed section having a base portion and inclined portions, first and second movable sections configured to be tiltable pivoting on a center point, and first and second deformable sections whose cavities defined by the fixed section, the movable sections and an expansible bellows is to be filled with fluid, wherein the inclined faces of the fixed section and the flat faces of the movable sections are caused to approach or move away from each other by the tilting of the movable sections pivoting on the center point to vary the quantity of the fluid in the cavities of the movable sections, and to vary the sectional shape of the X-ray absorbing portion of the bowtie filter.

Abstract: A method and apparatus for tailoring the profile of an x-ray beam for radiographic imaging for a specific subject is disclosed. The invention includes a filter assembly having a pair of filters, each of which may be dynamically controlled by a motor assembly during data acquisition. The filters are positionable in the x-ray beam so as to shape the intensity profile of the x-ray beam. In one exemplary embodiment, the filters are dynamically positioned during CT data acquisition based on the shape of the subject. A method of determining the shape of the subject prior to CT data acquisition is also disclosed.

Abstract: An X-ray diagnostic device has an X-ray tube and a diaphragm housing in which diaphragm plates for limiting an X-ray field are contained, as are a lamp and a mirror. The lamp and mirror are configured so that, when the lamp is on, the light therefrom is reflected by the mirror so that the reflected ray field coincides with the hypothetical X-ray field. At least one filter for filtering the X-rays is disposed in the diaphragm housing. The mirror and the filter or filters are attached to a single disk that rotates around an axis such that either the mirror or a filter is within the hypothetical X-ray field.

Abstract: The present invention is directed to a method and apparatus for CT data acquisition using a rotatable pre-subject filter having more than one filtering profile to control radiation exposure to a subject. The filter has one profile used to filter radiation when the radiation source is positioned above a subject and another profile that is used to filter radiation when the radiation source is positioned at a side of the subject.

Abstract: A system and method of diagnostic imaging is provided that includes positioning a subject in an imaging device, performing at least one scout scan, and marking a user-defined region-of-interest. An attenuation characteristic of an attenuation filter is then automatically adjusted based on the user-defined region-of-interest. The present invention automatically selects a proper attenuation filter configuration, corrects patient centering, and corrects noise prediction errors, thereby increasing dose efficiency and tube output.

Abstract: A method of at least partially compensating for an x-ray tube target angle heel effect includes positioning a filter having an anode side and a cathode side between an x-ray source and an x-ray detector, wherein the cathode side has a higher attenuation coefficient than the anode side, to at least partially compensate for the target angle heel effect.

Abstract: The present invention is directed to a method and apparatus for CT data acquisition using a rotatable pre-subject filter having more than one filtering profile to control radiation exposure to a subject. The filter is caused to rotate by a motor and bearing assembly and has one profile used to filter radiation when the radiation source is positioned above a subject and another profile that is used to filter radiation when the radiation source is positioned at a side of the subject.

Abstract: A technique for selectively attenuating a radiation exposure in which a configurable collimator is employed between the radiation source and the radiation target. The configurable collimator typically comprises an array of independently addressable elements each of which has at least a high and a low attenuation state, though intermediate states may also be accommodated. The elements of the array may be selectively addressed to determine their state and to determine the attenuation profile of the collimator. One embodiment of the technique employs an array of microactuated attenuating louvers which may be selectively actuated to determine their radiation transmittance. A second embodiment of the technique employs a suspension of attenuating nematic colloids which may be ordered by the application of an electric or magnetic field. The ordered state of the nematic colloids within an element determine the radiation transmittance of that element.

Abstract: An apparatus, suited, for example, for extreme ultraviolet lithography, includes a radiation source and a processing organ for processing the radiation from the radiation source. Between the radiation source and the processing organ a filter is placed which, in the radial direction from the radiation source, comprises a plurality of foils or plates.