Abstract: A geometric calibration apparatus detects points from projection regions onto which markers disposed on a phantom are projected, and calculates an output vector representing a probability distribution that gives a probability with which each point is a projection of each marker, by inputting data corresponding to each point to a learning model. The geometric calibration apparatus extracts a predetermined number of samples based on the probability distribution, obtains a candidate projection matrix by transforming correspondences between markers determined based on the samples among the markers and points determined based on the samples among the points, calculates points into which the markers are transformed by the candidate projection matrix, calculates a difference between a set of the transformed points and a set of the detected points, and designates the candidate projection matrix as a projection matrix when the difference is less than or equal to a threshold.

Abstract: The invention provides a method for locating radioactive material implanted in a living body, the method having the steps of implanting a stent into the body, the stent containing the radioactive material; imaging the body to determine a first position of the stent relative to remote points on the body; determining a second position of the stent at a second time later than the time of the implanting step; and measuring the distance between said first position and said second position. Also provided is a system for determining movement of a radiation source implanted in a living body, the device having a radiographic film overlaying a region of the body so as to oppose the radiation source, whereby the film is positioned relative to a reference point on the body; a grid disposed between the film and the body; and a radio-opaque substrate overlaying the film.

Abstract: A specimen holding and positioning apparatus operable to substantially non-movably maintain a specimen (e.g., an excised tissue specimen) in a fixed or stable orientation with respect to the apparatus during imaging operations (e.g., x-ray imaging), transport (e.g., from a surgery room to a pathologist's laboratory), and the like for use in facilitating accurate detection and diagnosis of cancers and/or other abnormalities of the specimen.

Abstract: A method of calibrating a positioning system in a radiation therapy system which includes a radiation therapy unit having a fixed radiation focus, includes irradiating a calibration tool having at least one reference object, capturing at least one two-dimensional image including cross-sectional representations of reference objects of the calibration tool and determining image coordinates of the representation of each reference object. Based on the reference objects' image coordinates, positions of the reference objects in the stereotactic coordinate system relative to an origin of the calibration tool and the position of the origin of the calibration tool relative to the imaging unit, a position difference between the position of the calibration tool in the stereotactic coordinate system and a position of the calibration tool in an imaging system coordinate system including a translational and rotational position difference is calculated.

Abstract: A disclosure of the present invention is related to an apparatus and a method for generating three-dimensional information. The apparatus for generating three-dimensional information may include a light source providing light to an object to be reconstructed in three-dimensional information, a coordinate reference mechanism unit provided between the light source and the object and having a plurality of protrusions reflecting the light; a camera unit outputting an image capturing the coordinate reference mechanism unit and the object simultaneously; and a three-dimensional information processing unit generating the three-dimensional information of the object by identifying a projection plane formed by the light and using the projection plane, considering a relationship between a plurality of actual protrusion reflection points at which the light is reflected by the plurality of protrusions respectively and a plurality of protrusion reflection points displayed in the image.

Abstract: A calibration object is imaged in a radiographic system such as a CT system. The images are processed to calibrate the system, without prior measurement of the calibration object. Initial estimates are refined to improve accuracy.

Abstract: In an image analysis device, an image analysis method, and a non-transitory computer-readable recording medium, it is determined whether a radiographic image is captured by rocking a rocking imaging grid. The image analysis device includes: a radiographic image acquisition section; a dosage data acquisition section that acquires dosage data indicating, in a time-series manner, a dosage of radiation rays exposed to a specific position in an imaging area in a specific period; and a determining section that determines whether the dosage data has a first feature indicating a dosage variation as a plurality of radiation absorbing bodies and a radiation transmitting body disposed between adjacent radiation absorbing bodies pass through a space between the specific position and a radiation source, and determines that the radiographic image corresponding to the dosage data determined to have the first feature is a rocking grid use image captured by rocking a rocking imaging grid.

Abstract: An embodiment in accordance with the present invention provides a method for applying task-based performance predictors (measures of noise, spatial resolution, and detectability index) based on numerical observer models and approximations to the local noise and spatial resolution properties of the CBCT reconstruction process (e.g., penalized-likelihood iterative reconstruction). These predictions are then used to identify projections views (i.e., points that will constitute the scan trajectory) that maximize task performance, beginning with the projection view that maximizes detectability, proceeding to the next-best view, and continuing in an (arbitrarily constrained) orbit that can be physically realized on advanced robotic C-arm platforms.

Abstract: An apparatus includes a gaseous region extraction unit that extracts a gaseous region from a lumen image, a residue candidate region extraction unit that extracts a candidate of a residue region from the lumen image as a residue candidate region, a boundary candidate region detection unit that detects a boundary candidate region that includes a boundary between the gaseous region and the residue candidate region, a representative direction component obtaining unit that obtains a representative direction component representing a plurality of directional components of an image in the boundary candidate region, a boundary region detection unit that detects a boundary region that includes a boundary between the gaseous region and the residue region from the boundary candidate regions based on the representative direction component, and a residue region extraction unit that extracts the residue candidate region that includes the boundary region as the residue region.

Abstract: Systems and methods for color calibrating an image are described herein. In some embodiments, a method includes disposing a unique identifier and a fiducial marker that includes a plurality of color regions on an object. A first image of the object is captured with a first camera and a second image of the object that is captured with a second camera is received. The second image is associated with the first image based on the unique identifier and spectral information of at least a portion of the fiducial marker in the second image is compared with spectral information of at least the portion of the fiducial marker in the first image. Based on the comparison, the second image is resampled to substantially match at least the portion of the fiducial marker in the second image to at least the portion of the fiducial marker in the first image.

Abstract: A method of inspecting a part is provided that includes the steps of aligning a contoured sheet having at least one surface that corresponds to at least one surface of the part, the contoured sheet having first portions and second portions, the first portions being radiodense and the second portions being radiolucent, and at least some of the second portions corresponding to internal features of the part. The part with the contoured sheet is exposed to x-rays to produce a first radiograph with markings that correspond to the first and second portions of the contoured sheet.

Abstract: A patient safety system (PSS) (100) uses optical tracking in a linear accelerator treatment room to prevent gross setup errors. A patient (150) undergoes a computed tomography (CT) treatment-simulation scan while a CT ball bearing (BB) is on patient's surface. The CT BB is replaced with an infrared reflective marker (IRRM) (160) before radiotherapy treatment starts. Coordinates of the CT BB relative to an isocenter of the treatment room are used as reference for tracking. The coordinate system of an optical tracking system is converted to a coordinate system of the treatment room. The PSS evaluates setup accuracy for a radiotherapy session by comparing real-time position of the single IRRM determined by the optical tracking technology with a predicted reference position, and displays results on a graphical user interface. The PSS stops radiation when a deviation between real-time coordinates and predicted coordinates of the IRRM (160) exceeds a predefined threshold.

Abstract: Position errors of the flat-panel detector in the axes system of the radiation penetration system relative to a necessitated position which remain, for example, after a coarse setup of the radiation penetration system are balanced and thus the accuracy of the radiation penetration system is brought almost randomly close to the accuracy which would have resulted if the flat-panel detector had been exactly adjusted mechanically subsequently by executing a geometrical correction of the radiation penetration raw image, so that a change of a projection of the penetrated object in the radiation penetration raw image due to the position error is reduced or corrected.

Abstract: A method for correcting a volumetric image to address error due to deflection of a patient support is provided. The method includes obtaining a first set of projection data and a second set of projection data. The first and second sets of projection data are generated when the patient is at a first position and a second position, respectively, and are usable to reconstruct a first volumetric image and a second volumetric image, respectively. A corrected volumetric image is then determined based on the first and second sets of projection data.

Abstract: A dimensioned grid apparatus for determining: 1) leg length, offset, and cup position during arthroplasty replacement surgery; 2) fracture reduction/correction position during trauma procedures and 3) an apparatus to be used for deformity correction planning is provided.

Abstract: A radiation imaging system includes a radiation imaging cassette and a console device. A communication mode between the cassette and the console device is switchable between a wired mode and a wireless mode. Due to shortage of a battery of the cassette, the communication mode is switched to the wired mode to start charging the battery and send image data from the cassette to the console device through a cable. The console device has first and second judging sections. The first judging section judges whether or not a charge level of the battery exceeds a predetermined threshold value. The second judging section judges whether or not radiography is in progress. If it is judged that the charge level of the battery exceeds the predetermined threshold value and the radiography is not in progress, a window that indicates permission for switching to the wireless mode is displayed on a monitor.

Abstract: Some embodiments include obtaining a projection image of a plurality of fiducials associated with a coordinate system irradiated by a radiotherapy radiation source at a plurality of discrete locations on a trajectory path model, determination of a projection matrix from projection images of the fiducials irradiated by the radiotherapy radiation source at each of the discrete locations, determination of the actual coordinate of the radiotherapy radiation source in the coordinate system associated with the fiducials at the plurality of discrete locations based on the determined projection matrices, and correlating the trajectory path model of the radiotherapy radiation source to the determined actual position of the radiotherapy radiation source at the discrete locations.

Abstract: A biopsy grid is provided that is useful in medical imaging. The biopsy grid comprises a hydrogel layer containing a mixture of contrast agents that are visible in images from X-ray, CT scans, MRI, and/or positron emission tomographs. The hydrogel mixture is attached to a frame having a silicone coated release liner and an adhesive layer. The hydrogel layer is cut into strips that serve as markers in an image. The biopsy grid can be used to locate the position of the marker relative to a tissue of interest in a medical image.

Abstract: Systems and techniques for implanting medical devices. In one aspect, an apparatus includes a flexible base member that can be flexed manually to conform to a contour of an anatomy, the base member including a radioscopic indicium that has a characteristic such that, under radioscopic imaging, passage of a skin-penetrating electromagnetic radiation is hindered to an extent that is distinguishable from a hindrance of the electromagnetic radiation by another portion of the base member.

Abstract: An MRI-compatible patch for identifying a location includes a flexible base layer, a flexible substrate and at least one of MRI-visible fiducial element. The flexible base layer is mountable on and substantially conformable to a patient's body surface. The base layer has opposed upper and lower primary surfaces. The flexible substrate is releasably attached to the upper primary surface of the base layer and substantially conformable to the patient's body surface. The at least one MRI-visible fiducial element is defined by or secured to the flexible substrate. The patch may include a plurality of the MRI-visible fiducial elements arranged in a defined pattern.

Abstract: An X-ray imaging apparatus includes an X-ray generation unit configured to irradiate an object with X-rays in a rectangular shape, and an imaging unit which has a rectangular imaging plane and is configured to receive the X-rays transmitted through the object as an X-ray image, wherein the imaging unit is arranged on a plane which is spaced a predetermined distance apart from the X-ray generation unit and perpendicular to an X-ray reference axis such that a center of an irradiation field and a center of the imaging plane match with each other and rotational angles of the irradiation field and the imaging plane around the X-ray reference axis match with each other, by matching at least three visible light beams which have directionality and are irradiated from the X-ray generation unit, with distance indexes provided in the imaging unit.

Abstract: The invention relates to a fiducial marker having a marking grid that is used to correlate and view images produced by different imaging modalities or different imaging and viewing modalities. More specifically, the invention relates to the fiducial marking grid that has a grid pattern for producing either a viewing image and/or a first analytical image that can be overlaid with at least one other second analytical image in order to view a light path or to image different imaging modalities. Depending on the analysis, the grid pattern has a single layer of a certain thickness or at least two layers of certain thicknesses. In either case, the grid pattern is imageable by each imaging or viewing modality used in the analysis. Further, when viewing a light path, the light path of the analytical modality cannot be visualized by viewing modality (e.g., a light microscope objective).

Abstract: A calibration cage for use in Roentgen Stereophotogrammetric Analysis (RSA), comprising a biplanar configuration of two compartments, each with a fiducial plate at the bottom and a control plate at the top and parallel thereto, the fiducial and control plates of one compartment being oriented at approximately 90° to fiducial and control plates of the other compartment such that a region of interest is positioned on one side of the fiducial and control plates of both compartments.

Abstract: Disclosed is a mobile radiographic unit with improved x-ray scatter control. Improved x-ray scatter control is provided through the alignment of the system with the focal line of an anti-scatter grid. In a preferred embodiment, the system comprises an x-ray source assembly, a tube housing mounting, a measuring system, a motion control system and a processor in communication with the measuring system and the motion control system.

Abstract: A method and device are provided for matching a patient coordinate system (PCS) of a nuclear medical imaging scanner with a coordinate system of a CT scanner in a multimodality modular imaging system, based on a predefined relationship between a vertical position of a patient bed during the NM scan; an axial position of the patient bed during the NM scan; an axial distance between a gantry of the NM scanner and a gantry of the CT scanner; and a vertical distance between a center of orbit of the NM scanner and a center of rotation of the CT gantry.

Abstract: A radiopaque diagnostic kit, tool and method for helping a practitioner define an optimal anatomical location of a patient to perform diagnostic and interventional procedures.

Abstract: An article of manufacture comprising a radiation sensitive material, and a measuring scale that is part of the radiation sensitive material. A method of measuring at least one parameter relating to an irradiated material is also described. A radiation sensitive material including a measuring scale is exposed to radiation and at least one parameter relating to one or more exposed areas of the material is measured by reference to the measuring scale on the material.

Abstract: A method and apparatus for determining a degree of deflection in a breast compression plate. The mammography apparatus further includes an optical measuring device. The method and apparatus involve (a) providing a pattern on the breast compression plate, the pattern being imagable by the optical measuring device, and having a plurality of local pattern indicia; (b) adjusting the breast compression plate to a selected height; (c) imaging the breast compression plate using the optical measuring device to provide an image of the pattern, the image having a plurality of local image indicia including an associated local image indicia for each local pattern indicia in the plurality of local pattern indicia; and (d) for each local pattern indicia in the plurality of local pattern indicia, determining an associated local deflection of the breast compression plate from the associated local image indicia.

Abstract: A calibration system is disclosed for a stereoradiographic device having an X-ray source and a vertical X-ray receiver, the calibration system includes a horizontal table which rotates between two reference positions that are separated by 90 degrees in a horizontal plane of the table. A vertical frame is fastened to the horizontal table and is symmetrical with an axis of rotation of the table, the frame accommodates a patient that remains stationary relative to the frame as the table is rotated between its two reference positions wherein corresponding X-ray photographs are taken. At least three markers made of radio-opaque material are firmly attached to the frame, one of the markers represents the origin of orthogonal X,Y and Z axes, a second of the markers is located at a predetermined point along the X-Y axes, the third marker located at a known distance along the Z axis, the markers defining respective distances Lx, Ly or H relative to the origin.

Abstract: A method for detecting and attenuating grid artifacts in a digital radiographic image comprising; providing an input digital radiographic image; processing the input digital radiographic image with a detection algorithm based on 2-D dynamic correlation in both spatial and frequency domains to determine whether the input digital radiographic image has a grid artifacts; and if it does detecting the grid orientation, frequency, and signal-to-noise ratio of the grid artifacts, designing a frequency bandstop (notch) digital 1-D filter as a function of the grid frequency and attenuation level; and suppressing the grid artifacts by further processing said input digital radiographic image with said designed filter to produce an output digital radiographic image of improved image quality.

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: The invention relates to a grid (10) adapted to be arranged on a patient's skin to provide positioning information in CT-guided percutaneous operations. In one embodiment, the grid (10) comprises a flat and generally rectangular frame having two long sides (11a, 11b) and two short sides (12a, 12b), with a number of transverse ribs (13, 14) being provided between the two long sides (11a, 11b). According to the invention, at least some of the transverse ribs (13, 14) are elastic. By using his/her fingers, a doctor can thereby separate two neighbouring ribs (13, 14) such that an opening is provided in the grid (10). Through this opening access is obtained to the skin area under the grid (10), or the grid (10) can be threaded over and removed from a medical instrument which, between two adjacent ribs (13, 14), is inserted into the patient's body.

Abstract: A marking grid is provided for use in radiographic imaging, and a method is provided for manufacturing the marking grid. The marking grid is comprised of a radiolucent substrate with a pressure sensitive adhesive on one side, a plurality of parallel strips of radiopaque material fixed to the substrate on the side opposite the pressure sensitive adhesive, and apertures in the substrate between the parallel strips of radiopaque material. The substrate is provided on a releasable backing with a plurality of holes longitudinally spaced relative to each other, which can be used to register the position of the substrate in the equipment used to produce the marking grids.

Abstract: A tomographic image reading method for extracting a comparison image corresponding to a diagnostic image, the diagnostic image being one of first tomographic images, the comparison image being one of second tomographic images, the method including the steps of: inputting the first images and the second images; generating a first projection image from the first images and a second projection image from the second images; measuring shift amount between the first projection image and the second projection image by using a template; correcting the slice position according to the shift amount; and displaying the diagnostic image and the comparison image to a monitor.

Abstract: A method and system for calibrating x-ray image data for medical navigation using a calibration instrument that is detected and tracked by a medical navigation system and has a plurality of localization structures that are detectable in x-ray images. The localization structures are arranged on at least two spaced supports. The method includes producing an x-ray image without a patient of the localization structures while the calibration instrument is tracked by a medical navigation system. After the x-ray image is registered in the medical navigation system using the localization structures, at least one of the spaced supports is removed from the calibration instrument. A second x-ray image is taken of a patient together with the calibration instrument with the support removed. The two images are compared to determine whether there is sufficient correspondence of the localization structures visible in the two images.

Abstract: A system includes acquisition of first electronic image data representing a phantom located at a first position and irradiated by a first radiation field emitted by a radiation emitter, acquisition of second electronic image data representing the phantom located at a second position based at least on a first light field emitted by a light emitter and irradiated by a second radiation field emitted by the radiation emitter, generation of third electronic image data by correcting the second electronic image data based at least on the first electronic image data, and determination of a deviation between the first light field and the second radiation field based at least on the third electronic image data.

Abstract: A marking grid is provided for use in radiographic imaging, and a method is provided for manufacturing the marking grid. The marking grid is comprised of a radiolucent substrate with a pressure sensitive adhesive on one side, a plurality of parallel strips of radiopaque material fixed to the substrate on the side opposite the pressure sensitive adhesive, and apertures in the substrate between the parallel strips of radiopaque material. The substrate is provided on a releasable backing with a plurality of holes longitudinally spaced relative to each other, which can be used to register the position of the substrate in the equipment used to produce the marking grids.

Abstract: A marking grid is provided for use in radiographic imaging, and a method is provided for manufacturing the marking grid. The marking grid is comprised of a radiolucent substrate with a pressure sensitive adhesive on one side, a plurality of parallel strips of radiopaque material fixed to the substrate on the side opposite the pressure sensitive adhesive, and apertures in the substrate between the parallel strips of radiopaque material. The substrate is provided on a releasable backing with a plurality of holes longitudinally spaced relative to each other, which can be used to register the position of the substrate in the equipment used to produce the marking grids.

Abstract: A shielding grid constructed of a radiation absorbing material for use with an array of discreet, non contiguous radiation sensors to protect such sensors from scattered radiation. The sensors each have a radiation sensitive area with a width and a length. In designing the grid a prototile having a prototile width and a prototile length is developed. The prototile width is equal to the radiation sensitive area width divided by an integer and the prototile length is also equal to the radiation sensitive area length divided by an integer. The prototile contains a pinwheel motif of radiation absorbing material contained solely within the prototile that forms a pattern when a plurality of prototiles sufficient to cover the array of discreet sensor are arrayed contiguously. The grid is constructed with the radiation absorbing material in this pattern.

Abstract: In a method applied and an x-ray system for determining a spatial relationship of X-ray datasets measured independently of one another, an x-ray apparatus registers X-ray datasets of a patient and a scale is provided that makes position data available that are identifiable in at least one of the registered dataset. The position data serve for the determination of the spatial relationship between at least two X-ray datasets that were registered from different body portions of the patient.

Abstract: A marking grid is provided for use in radiographic imaging, and a method is provided for manufacturing the marking grid. The marking grid is comprised of a radiolucent substrate with a pressure sensitive adhesive on one side, a plurality of parallel strips of radiopaque material fixed to the substrate on the side opposite the pressure sensitive adhesive, and apertures in the substrate between the parallel strips of radiopaque material. The substrate is provided on a releasable backing with a plurality of holes longitudinally spaced relative to each other, which can be used to register the position of the substrate in the equipment used to produce the marking grids.

Abstract: An X-ray image photographing apparatus includes an image obtaining portion for obtaining an X-ray distribution transmitted through an object, a grid detecting system having a construction for obtaining information from a grid side by the action of inserting the grid for decreasing scattered rays into the apparatus, and detecting at least one of the presence or absence of the grid, the kind of the grid and the presence or absence of the replacement of the grid by the use of the construction, an image processing system for image processing and outputting image data collected by the image obtaining portion, and a memory portion preserving therein a plurality of sets of image processing parameters for controlling the image processing system. The image processing system selects the image processing parameters preserved in the memory on the basis of at least the result of the detection by the grid detecting system and executes image processing.

Abstract: The shutters (2) in an X-ray device which include at least a radiation source (1), a diaphragm device (8) with shutters (2) and a recording (3) and image processing unit (4), are provided with hole and/or edge patterns (11-14) which reproduce non-anatomical patterns in the radiation image; the shutter edges (15) are detected in the radiation image in the image processing unit on the basis of such patterns, so that only the directly irradiated part of the patient is displayed.

Abstract: A reference grid is incorporated into a flexible transport media for use in internal inspection equipment such as airport x-ray equipment. The reference grid is used as a standard calibration of known density to analyze threat potential of baggage components.

Abstract: The invention relates to an X-ray examination apparatus for and a method of forming distortion-free X-ray images, which apparatus and method enable the imaging properties of the C-arm X-ray system to be derived from the patient image. To this end, a reference image (FIG. 4) is formed in a reference orientation of the X-ray examination apparatus and the reference imaging properties of the C-arm X-ray system are determined on the basis of the positions of calibration members (7, 8), which are mounted on the image intensifier (2) and/or the X-ray source (3) and are reproduced, and the known geometry and position relative to the image intensifier (2) and/or the X-ray source (3); the positions of the calibration members (7, 8) reproduced in a patient X-ray image (FIG. 5) are compared with the positions of the calibration members (7, 8) in the reference image (FIG.

Abstract: A shielding grid constructed of a radiation absorbing material for use with an array of discreet, non contiguous radiation sensors to protect such sensors from scattered radiation. The sensors each have a radiation sensitive area with a width and a length. In designing the grid a prototile having a prototile width and a prototile length is developed. The prototile width is equal to the radiation sensitive area width divided by an integer and the prototile length is also equal to the radiation sensitive area length divided by a integer. The prototile contains a motif contained solely within the prototile that forms a pattern when a plurality of prototiles sufficient to cover the array of discreet sensor are arrayed contiguously. The grid is constructed with the radiation absorbing material in this pattern.

Abstract: A pressure-sensitive adhesive sheet comprising a plastic sheet having on one surface thereof a pressure-sensitive adhesive layer, wherein the plastic sheet has on at least one surface thereof a print layer having a thickness of 40 to 1,000 &mgr;m and containing 30 to 90% by weight based on the total weight of the print layer of an X-ray absorbing metal. The print pattern may be scales, grid lines, numbers, etc. singly or in combination. Information on individual subject or scales or grid lines pattern may be copied in a radiograph having an image of the inside of the subject body. This enables surgeons to determine the size of the inside of the subject body or position of target organ with ease.

Abstract: An orientation marker for a digital radiogram formed by a plurality of pixels arrayed along a plurality of rows and columns. The pixels have densities which represent the radiogram optical density at each pixel point, and the densities are represented by digital values. The marker is made by a number of marker pixels arrayed along at least one row and one column of the radiogram. Each of the pixels forming the marker, have a marker pixel digital value which has been selected to form an asymmetrical marker pixel pattern on the radiogram, replacing the original radiogram pixel values.

Abstract: A parallel X-ray beam generated from an X-ray generator is radiated onto a CCD of a CCD camera via a metal mesh disposed in front of the CCD. In order to detect the X-ray, a multi-pitch metal mesh (11) is disposed as the metal mesh. The incident position of the X-ray is determined on the basis of a ratio between a primary electron cloud produced by the X-ray spread over a plurality of pixels and a portion of the cloud existing in each of the plurality of pixels.

Abstract: According to an embodiment of the present invention, an isocenter of an image may be found by using a multi-leaf collimator. According to this embodiment, a center leaf is projected into the center of the x-ray field with all other leaves retracted. An image is acquired. A line through the center of the center leaf is identified. This line is also a line through isocenter. Another method according to an embodiment of the present invention for finding isocenter uses an accessory. The accessory according to an embodiment of the present invention includes a metal marker in the center of the accessory with metal markers interspersed away from the center at a predetermined interval. An image may be acquired through the accessory, with the patient on the table. The resulting image may be analyzed to identify the position of the metal markers to determine isocenter.