Abstract: A T2 preparation sequence uses a segmented BIR-4 adiabatic pulse with two substantially equal delays and is insensitive to B1 field variations and can simultaneously suppress fat signals with low specific absorption rate (SAR). An adiabatic reverse half passage pulse is applied followed by a predetermined delay. An adiabatic full passage pulse is applied followed by a substantially equal delay, followed by an adiabatic half passage pulse. Fat signal suppression is achieved by increasing or decreasing either the first delay or the second delay.

Abstract: PRF shift MRI data is acquired. The PRF shift MRI data may include signals affected by both a desired PRF shift and an undesired PRF shift. Thus, example systems and methods describe manipulating the PRF shift MR! data to make it substantially free of the effects of the undesired PRF shift, which facilitates displaying certain MRI images based on the desired PRF shift.

Abstract: With the objective of reducing the number of times that RF pulses are idle-shot during an idling time upon executing an SSFP pulse sequence by a phase cycling method and thereby performing imaging efficiently, the angle of the phase of each RF pulse is changed during the idling time so as to sequentially increase every time of repetition to a phase-increased angle at the time that the RF pulses are repeatedly transmitted at a scan executed after the idling time, thereby transmitting the RF pulses.

Abstract: This invention provides methods, NMR probes, and NMR systems for the analysis of the contents of sealed food and beverage containers and the like.

Abstract: A method for producing images of a subject containing M spin species using a magnetic resonance imaging (MRI) system includes obtaining N k-space data matrices from N k-space data sets acquired with the MRI system using a pulse sequence with an individual associated echo time. The k-space data matrices each include corresponding data at the same plurality of k-space locations and time stamps are tracked for each k-space location. For each k-space location, a set of linear equations in k-space is solved. The set of linear equations relates corresponding data from the N k-space data matrices, echo times and time stamps to desired calculated k-space data. Calculated data in k-space which is corrected for chemical shift is produced corresponding to each k-space location and aggregated to obtain a k-space calculated data set. The k-space calculated data set is transformed to image space to obtain a corresponding image.

Abstract: An apparatus includes acquiring means for acquiring echo data of a plurality of views in which a phase difference between water and fat is 2?/m with spins within a subject brought to the SSFP state and repeating the acquisition for k=0 through M?1 with a step difference in a phase of an RF pulse of 2?·k/M; transforming means for conducting Fourier transformation on the echo data based on the phase step difference; separating means for separating water data and fat data respectively in F(0) term and F(1) term of the Fourier-transformed data using the phase difference between water and fat; adding means for obtaining a sum of absolute values of at least the water data or fat data in the F(0) term and F(1) term; and image producing means for producing an image based on the sum data.

Abstract: The present invention relates to a magnetic resonance spectroscopic imaging (MRSI) method, specifically to a magnetic resonance spectroscopic imaging method with up to three spatial dimensions and one spectral dimension. Interleaving dynamically switched magnetic field gradients into the spectroscopic encoding scheme enables multi-region shimming in a single shot to compensate the spatially varying spectral line broadening resulting from local magnetic field gradients. The method also employs sparse spectral sampling with controlled spectral aliasing and nonlinear sampling density to maximize encoding speed, data sampling efficiency and sensitivity.

Abstract: The present invention relates generally to nuclear magnetic resonance tomography (synonym: magnetic resonance tomography—MRT) as used in medical applications for examining patients; it relates in particular to a calibrating method when there is FOV displacement within a plane through angle-dependent modulating of the phase of the Fourier DC point of the respective read-out direction in MRT imaging for determining the device-specific dependency of the time delay requiring to be compensated between the reference signal effecting modulation and the read-out measuring data points of the respective read-out direction of settable measurement parameters.

Abstract: In a method for dynamic frequency detection of the resonance frequency in magnetic resonance spectroscopy, by measuring navigator signals at the same point in time in each of a number of successive sequence passes, and by comparing the navigator signals, a frequency shift of the resonance frequency is determined on the basis of which the respective individual spectrum obtained from each sequence repetition is corrected with respect to the measured frequency shift.

Abstract: A system and method for probing a specimen to determine one or more components by utilizing a first signal to excite the specimen at a nuclear quadrupole resonant frequency and observing changes in a specimen property. One exemplary property may be dielectric constant. Another exemplary property may be magnetic permeability. In one embodiment, the first signal is unmodulated and a second signal is observed for the presence of modulation at the frequency of the first signal. Alternatively, the first signal may be modulated and the second signal may be observed for the presence of the modulation. A system is disclosed wherein the specimen is excited using the first frequency and a radar at the second frequency is used to observe changes in radar reflectivity of the specimen due to the excitation.

Abstract: A controller for apparatus assuming a sequence of precisely synchronized states in accordance with a lengthy event stream is realized in an architecture comprising a register layer comprising a plurality of latched registers for receiving event descriptors and parameters from a bus and a computational/logical layer for operations on/among certain of said parameters for presentation to external operational devices. An RF controller controlling frequency, pulse width, amplitude with precise timing for magnetic resonance applications is one example and a magnetic gradient controller controlling vector magnitude and orientation is another.

Abstract: To analyze a network of conductors, especially an electrical power supply network, it is planned to measure the spectral (49) and temporal (50) nature of a signal available at a node of the network. An image (49–51) representing this state is produced. This image produced is compared with an expected image (52–55) showing an <<on >> state of one and/or the other of the appliances connected to this network. The state of the appliances, whether on or off, is deduced therefrom. This information can be used to optimize the use of the electrical power or to monitor the activity of the appliances concerned.

Abstract: A controller for apparatus assuming a sequence of precisely synchronized states in accordance with a lengthy event stream is realized in an architecture comprising a register layer comprising a plurality of latched registers for receiving event descriptors and parameters from a bus and a computational/logical layer for operations on/among certain of said parameters for presentation to external operational devices. An RF controller controlling frequency, pulse width, amplitude with precise timing for magnetic resonance applications is one example and a magnetic gradient controller controlling vector magnitude and orientation is another.

Abstract: A low cost, low power and lightweight swept sine wave analysis system that is affordable to engineers, university laboratories and students, providing accurate magnitude and phase response measurements over a wide bandwidth is described. An analog mixer mixes a local oscillator signal with an amplified input signal allowing AC signal coupling between input stages. This minimizes errors due to DC and low frequency drift. A computer graphical interface is used for controlling the acquisition hardware in real time, displaying results on the computer screen, and making the graphical results and numerical results immediately available for inclusion in documentation or spreadsheet applications.

Abstract: A method of inducing spin excitation by employing RF transmission fields of time-varying spatial characteristics in order to better control the overall distribution of spin excitation. The MRI transmit inductor system generates an RF transmission of particular spatial characteristics, followed by one or more additional RF transmissions with different spatial characteristics, where the additional RF transmissions alter the spin excitation produced by the first RF transmission. The spin excitation can be provided by a sequence of two or more discrete RF transmissions with different spatial characteristics, by a single RF transmission that has continuously varying spatial characteristics, by using successive RF transmissions of the primary and higher order modes of a volume coil, and/or by an RF transmission from a volume or surface coil followed by a second RF transmission from one or more local surface coils.

Abstract: An improved magnetic resonance imaging (MRI) methodology uses an abbreviated initial MRI sequence to generate sequence diagnostic parameters. The sequence diagnostic parameters have a fixed relationship to certain sequence-conditioning parameters, and are used for calculating characteristic values of the sequence-conditioning parameters. The read out gradient pulse sequence is modified in accordance with the calculated characteristic values of the sequence-conditioning parameters. The modified read out gradient pulse sequence is then incorporated into a subsequent MRI pulse sequence used for obtaining a diagnostic image. The methodology has particular application in so called ultra fast MRI process which include echo-planar imaging (EPI) and echo-volume imaging (EVI).

Abstract: The invention provides a method of magnetic resonance imaging of regional blood oxygenation which comprises administering into the vasculature of a vascularized human or non-human animal subject a T2 blood pool contrast agent, detecting a magnetic resonance signal from at least part of the vasculature of said subject into which said contrast agent distributes, and manipulating said signal to generate an indication of the partial pressure of oxygen (pO2) in at least part of said vasculature.

Abstract: For the purpose of improve rendering capability for a blood vessel, an MR. image producing method comprises: window-processing MR signals using a window function f(k) that has a “value less than one” at a center (O) and in its proximate region in a k-space and on a periphery and in its proximate region in the k-space, and has a value larger than the “value less than one” between the regions in which the window function has the “value less than one;” and applying Fourier-transformation processing to the window-processed MR signals to obtain an MR image.

Abstract: MR imaging with gradient oscillations that are essentially at the same frequency to reduce off-resonance effects. Frequencies that are sufficiently close to each other to reduce such effects compared with known approaches are considered essentially the same frequency.

Abstract: In a method for aligning a magnetic field-modifying structure (74) in a magnet bore (12) of a magnetic resonance imaging scanner (8), a reference magnetic field map of the magnet bore (12) is measured without the magnetic field-modifying structure (74) inserted. The magnetic field-modifying structure (74) is inserted into the magnet bore (12). A second magnetic field map of the magnetic bore (12) is measured with the magnetic field-modifying structure (74) inserted. At least one odd harmonic component of the first and second magnetic field maps is extracted. The magnetic field-modifying structure (74) is aligned in the magnet bore (12) based on a comparison of the odd harmonic component of the first and second magnetic field maps.

Abstract: In a method for evaluating data that are generated by a magnetic resonance technique and contain spectroscopic information, at least two spikes of a spectrum of the data are detected, position that the detected spikes exhibit relative to one another within the spectrum is compared to spikes of known substances; and a known substance is allocated to the detected spikes given a coincidence of the comparison.

Abstract: A method for performing MRI, including imposing N sets of steady-state free precession (SSFP) sequences on an object to be imaged, the sequences including respective initial radio-frequency (RF) excitation pulses, each initial RF excitation pulse having a predetermined phase shift relative to the other initial RF excitation pulses. N is a whole number larger than one and less than six. The method further includes setting the phase shift of the RF pulse of the sequences so that the phase shift of the RF pulse of an Mth sequence is substantially equal to 2 ⁢ π ⁡ ( M - 1 ) N radians, wherein M is a whole number larger than 0 and less than or equal to N, receiving a respective set of image signals from the object responsive to the N sets of SSFP sequences, and processing the set of received image signals to generate an image of the object.

Abstract: A method of magnetic resonance imaging is provided. It includes supporting a subject in an examination region of an MRI scanner (A), and applying an EPI pulse sequence with the MRI scanner (A) to induce a detectable magnetic resonance signal from a selected region of the subject. The magnetic resonance signal are received and demodulated to generate raw data. Applied to the raw data are a pair of ghost reducing correction factors (&thgr;,&Dgr;). The pair of corrections factors (&thgr;,&Dgr;) included a phase correction (&thgr;) and a read delay (&Dgr;). The phase correction (&thgr;) compensates for phase errors in the raw data, and the read delay (&Dgr;) effectively shifts a data acquisition window (120) under which the raw data was collected to thereby align the raw data in k-space. The correction factors affect how data is loaded into k-space to generate k-space data, and the k-space data is subjected to a reconstruction algorithm to generate image data.

Abstract: In a method for operating a magnetic resonance device, a magnetic resonance signal is recorded over a span of time, and in order to produce a magnetic resonance spectrum, the magnetic resonance signal in the time domain is subjected to a Fourier transformation. The magnetic resonance signal is weighted with a bell-shaped window function before the Fourier transformation, thereby preventing broadening of resonance lines in the displayed frequency spectrum, so that non-dominant resonance lines, such as those associated with the metabolites, can be more readily analyzed.

Abstract: A Fast Fourier Transform based digital radiometer providing a frequency contiguous set of noise temperature measurements to characterize an atmospheric vertical temperature profile. The radiometer also has Doppler correction to account for velocity of a vehicle on which the radiometer is located and direction changes of a scene being measured.

Abstract: The present invention provides an improved multi-channel analyzer designed to conveniently gather, process, and distribute spectrographic pulse data. The multi-channel analyzer may operate on a computer system having memory, a processor, and the capability to connect to a network and to receive digitized spectrographic pulses. The multi-channel analyzer may have a software module integrated with a general-purpose operating system that may receive digitized spectrographic pulses for at least 10,000 pulses per second. The multi-channel analyzer may further have a user-level software module that may receive user-specified controls dictating the operation of the multi-channel analyzer, making the multi-channel analyzer customizable by the end-user. The user-level software may further categorize and conveniently distribute spectrographic pulse data employing non-proprietary, standard communication protocols and formats.

Abstract: Nuclear magnetic resonance spectroscopy catheter probe comprising a permanent magnet arrangement (1,2,3,4) for generating a static magnetic field of suitable intensity and homogeneity for analysing a sample of fluid flowing into a catheter (6) traversing the permanent magnet arrangement. The probe further comprises an arrangement of electronic circuits (8,9) responsible for the excitation and detection of the nuclear magnetic resonance signal and at least one coil (7) to expose the fluid sample to the excitation signal and to collect the returned nuclear magnetic resonance signal.

Abstract: A computer program product for use in conjunction with a computer system, the computer program product comprising a computer readable storage medium and a computer program mechanism embedded therein. The computer program mechanism comprises a quantum computing integrated development environment (QC-IDE) module and a compiler module. The QC-IDE module is used to design a quantum logic for a plurality of qubits. The QC-IDE module includes instructions for generating a time resolved set of operators. The compiler module includes instructions for compiling the time resolved set of operators into a set of quantum machine language instructions.

Abstract: A method of screening a subject for the presence of lipoprotein X includes the steps of: producing a measured lipid signal lineshape of an NMR spectrum of a blood plasma or serum sample obtained from a subject; generating a calculated lineshape for the sample, the calculated lineshape being based on derived concentrations of lipoprotein components potentially present in the sample, the derived concentration of each of the lipoprotein components being the function of a reference spectrum for that component and a calculated reference coefficient, wherein one of the lipoprotein components for which a concentration is calculated is lipoprotein X; and determining the degree of correlation between the calculated lineshape of the sample and the measured lineshape spectrum of the sample.

Abstract: Signal recovery in functional magnetic resonance imaging (fMRI) is provided by generating a single excitation pulse and exciting a target region of a subject with the generated excitation pulse. A first image is obtained using a first partial k-space frame of the target region. A compensation pulse is generated and the target region excited with the compensation pulse. A second, compensated, image is obtained subsequent to the excitation by the compensation pulse using a second partial k-space frame of the target region. The first and second images are combined to form a combined image of the target region. The first and second obtaining steps are carried out sequentially during a single quadratic excitation pulse.

Abstract: An improved method for magnetic resonance imaging of a sample includes the following steps: producing a magnetic field to orient the magnetic dipoles of a sample along the z axis of an x,y,z Cartesian coordinate system; applying a first radio frequency (rf) pulse along a different axis, near the resonance frequency of the magnetic dipoles (for example, the hydrogen atoms in water); applying a gradient pulse for a time tg in order to modulate the magnetization along a preferred axis in space (for example, the z axis); allowing the magnetization to evolve for a time \zq, during which time the local variations in the susceptibility affect the excited spins; applying a second radio frequency pulse near the resonance frequency of the magnetic dipoles; allowing the sample to evolve for a second time interval TE to create observable magnetization; then detecting this magnetization, using gradients to spatially resolve the signal.

Abstract: An implantable nuclear magnetic resonance spectrometer for measuring the chemical composition of a fluid or for measuring the flow rate of the fluid. The spectrometer includes a housing and a catheter traversing across the housing so that a fluid external to the housing may flow through the catheter within the housing. A permanent magnet is disposed within the housing and generates an intense homogenous magnetic field in the vicinity of the catheter. An electronic circuit is disposed within the housing for detecting and formatting a nuclear magnetic resonance excitation signal. An excitation coil is connected to the electronic circuit and is disposed about the catheter to expose the fluid within the catheter to the excitation signal and to collect the nuclear magnetic resonance excitation signal.

Abstract: A novel magnetic resonance method for two-dimensional or three-dimensional imaging of an examination zone is described, in which k-space is scanned at predetermined sampling positions. Magnetic resonance signals of a first data set over k-space and magnetic resonance signals of subsequent reduced data sets over part of k-space are acquired, and data of the subsequent reduced data sets are completed with data of the first data set in order to obtain a full image of the scanned object. The acquisition of data of the subsequent reduced data sets (d2, d3, d4) will start or end with the highest value in k-space. Further a novel magnetic resonance apparatus and a computer program product are described, which are designed for performing the above mentioned method.

Abstract: In a method for prescribing an essentially linear ramp with a prescribable slope by a quantity, and which is clock-pulse-controlled and which describes the ramp by an increment per clock interval, the ramp is described by a number of regular increments and by at least one first and one second irregular increment. The regular increments exhibit a value corresponding to the prescribable slope. The irregular increments exhibit a value deviating from the prescribable slope. The first irregular increment is a first increment describing the ramp and the second irregular increment is a last increment describing the ramp.

Abstract: A technique is provided for characterizing and correcting for instabilities or variations in a magnet system of an MRI scanner. The technique makes use of a navigator pulse to read out navigator echo data in the absence of phase encode, or with phase encode effects rewound. The navigator data is used to characterize several potential effects of magnet system instabilities or variations, such as zeroth order phase shifts, first order (linear) phase shifts, bulk position shifts, and amplitude effects. The effects of the instabilities can be used, then, to correct image data acquired during an examination.

Abstract: In magnetic resonance imaging, a pulse sequence is used to obtain both water-only and fat-only signals within a single acquisition time. Pulses and readout gradients are applied to take a proton-density-weighted image of the water, a proton-density-weighted image of the fat, and a T2-weighted image of the water. Between the first water readout gradient and the fat readout gradient, a spoiling gradient is applied to spoil the first water echo. Between the fat readout gradient and the second water readout gradient, a refocusing gradient is applied to refocus the second water echo. The proton-density-weighted images of water and fat are combined to form water-plus-fat images free of in-plane and through-plane chemical-shift artifacts.

Abstract: The invention relates to an MR method in which a navigator pulse is generated to excite a nuclear magnetization in a spatially limited volume by at least one RF pulse and at least two gradient magnetic fields having gradients which extend differently in respect of time and space. After the navigator pulse excitation, at least one MR signal is received from the volume in conjunction with a further gradient magnetic field for evaluation. In order to enhance the navigator pulse, a variation in time is imposed on the gradient magnetic fields in order to generate at least two MR signals which correspond to an excitation in the k space along mutually offset trajectories. The MR signals are combined.

Abstract: A method and system for imaging using an inhomogeneous static magnetic field is disclosed herein. The imaging includes providing the inhomogeneous static magnetic field to an object of interest located within an imaging volume. The imaging further includes providing a pulse sequence including a readout gradient pulse and a slice selection gradient pulse, both gradient pulses comprising a part of the inhomogeneous static magnetic field. The pulse sequence is configured to acquire a plurality of lines of k-space data per excitation.

Abstract: In a nuclear magnetic resonance spectrometer, the shape of a detection coil is changed from a conventional cage type to a solenoid type of higher sensitivity. Accordingly, differing from the conventional superconductive magnet of multilayer air core solenoids, a superconductive magnet is right and left divided to split magnets for generating 11 T, preferably, 14.1 T in the horizontal direction, and the magnetic field uniformity is set to 0.001 ppm or less and the temporal stability is set to 0.001 ppm or less.

Abstract: Imaging and image reconstruction are sequentially performed for slices of a subject, and realtime images of the slices are displayed substantially at the same time. The slices may be perpendicular or parallel to one another, or they may form a stereoscopic pair. The images may be displayed two-dimensionally, or they may be combined and displayed three-dimensionally. One of the slices includes an insertion (a needle) for puncture or biopsy that is inserted into the subject by an operator, and it is parallel with a direction in which the insertion should advance. If the needle is displaced from the slice and a shade of the needle disappears from the sequentially-displayed images of the slice while the operator moves the needle toward an affected part in the subject in IVR, the shade of the needle appears on the sequentially-displayed images of another slice that is perpendicularly intersecting to or is adjacent and parallel to the above-mentioned slice.

Abstract: The invention relates to a method for analysing a sample. According to said method, the sample is irradiated by at least one excitation pulse and several rephasing pulses, in such a way that echo signals are generated and determined. The inventive method is characterised in that all echo signals are encoded with a substantially identical phase position and that the exposure sequence is then repeated at least once.

Abstract: A detecting method and detector expands the capabilities of Nuclear Magnetic Resonance (NMR) analysis. A Rotational Exchange Gradient Imager (REGI) allows for real-time, in situ investigation of materials subjected to the effects of centrifugal force by NMR analysis. The REGI comprises a cylindrical stator formed of an electrically conductive, non-magnetic material, a rotor contained in the cylindrical stator formed of an electrically non-conductive, non-magnetic material, and a conductor located along a central axis of the cylindrical stator. A sample is contained within the rotor. The stator and central conductor serve to generate the RF magnetic field for NMR analysis. The rotor containing the sample is rotated within a stable air bearing formed between the cylindrical stator and rotor.

Abstract: Disclosed is a method for regularized high-order shimming of a magnetic field in an MRI system. In one application a spiral pulse sequence is used to acquire field maps, and based on the user selection a shimming region, a least squares calculation of shim currents is performed that minimizes the root mean square (RMS) value of the B0 in homogeneity-over the volume of interest. The singular value decomposition (SVD) is used to enable regularized methods for solving the least squares problem. The regularization allows arbitrary regions to be shimmed without the divergence of shim currents.

Abstract: In order to reduce ghost artifacts due to a Maxwell term phase error caused by a data acquisition read gradient, an n-th Maxwell term collection pulse MTCPn is appended before an inversion RF pulse RF180 for an n-th shot in an I-echo N-shot EPI pulse sequence. The n-th Maxwell term collection pulse MTCPn has a waveform whose time integral value is zero, and gives a bias phase error such that a Maxwell term phase error which is caused by a data acquisition read gradient and contained in data filling out a k-space smoothly varies from a 1st row to an N·I-th row in the direction of a phase encoding axis.

Abstract: While monitor images continuously generated by a monitor scan are displayed, the parent image of a difference image may be updated at any particular point in time. Further, during the display, the image may be switched between a normal reconstructed image and a difference image, and the difference method applied to the presently displayed difference image may be changed. When the body of a to-be-examined subject has moved, or the inflow effect of breathing, blood, etc. has occurred, and therefore the parent image of the presently displayed difference image is considered to become inappropriate, the operator may input an instruction to update the parent image.

Abstract: Three MRI acquisitions are performed to acquire data from which separate water and fat images may be reconstructed using a three-point Dixon technique. The NMR data is acquired with a phased array coil having four separate coil elements. Low resolution images are reconstructed from the acquired NMR data sets and used to calculate phase corrections which are used to correct reconstructed high resolution images. The corrected high resolution images are processed using the Dixon technique to produce fat and water images for each coil element which are combined into a single fat and a single water image.

Abstract: To correct motion and magnetic field inhomogeneity phase errors, inverting data collecting read gradients Nr1 and Nr2 are applied to collect correcting data H (n, 1) and H (n, 2) corresponding to focused navigation echoes Ne1 and Ne2, data collecting read gradients r1, . . . , rM which are inverted alternately are applied, and phase encode gradients pdn, p2, . . . , pM are applied at inverting, thereby collecting imaging data F (n, 1), . . . , F (n, M) corresponding to the focused imaging echoes e1, . . . , eM. This sequence is repeated for n=1, . . . , N while changing the magnitude of the phase encode gradient pdn, whereby data F (1, 1) to F (N, M) for filling a k space are collected. Based on the correcting data H (n, 1) and H (n, 2), the imaging data F (n, 1), . . . , F (n, M) are phase corrected.

Abstract: A magnetic resonance imaging method involves acquisition of sets of magnetic resonance signals from several scan-volumes of an object. According to the invention different spatial approaches are taken in the scanning of the respective scan-volumes. In particular_respective scan-volumes include different numbers of scan-slices or scan slices of respective scan-volumes have different slice-thickness or scan-slices of respective scan-volumes have different fields-of-view or scan-slices of respective scan-volumes have different numbers of scanned points in k-space.

Abstract: A filter unit comprises a wideband bandpass filter; at least one band-elimination filter having a stop band within the passband of the bandpass filter, so that the passband is divided into a plurality of pass bands by the stop band; and the wideband bandpass filter and the band-elimination filter being disposed in a single dielectric member. Since the passband of a wideband bandpass filter is divided into a plurality of pass bands by stop bands of one or more band-elimination filters, signals having frequencies corresponding to these divided pass bands are able to pass through the filter unit simultaneously.

Abstract: An MRI image acquired with a phase-array coil is corrected for motion artifacts using an iterative, autocorrection process in which corrections are tried and the quality of the resulting reconstructed image is measured. In one embodiment autocorrections are calculated for the data acquired with one coil element and the same corrections are made to data acquired with the other coil elements. In another embodiment autocorrections are calculated separately for the data acquired with each coil element. In either embodiment, the separate corrected images are combined to form the output image.