Abstract: A heart rate value determined from a first physiological signal that is acquired independently from a second physiological signal, is used to control a band pass filter for controllably bandpass filtering the second physiological signal. In a system having sensors for independently acquiring both electrocardiogram (ECG) and pulse oximetry (SpO2) signals, a heart rate value determined from the ECG signal is used to controllably bandpass filter the red and infrared SpO2 signals, thereby reducing the level of artifact signal in the SpO2 signals.

Abstract: Methods and apparatus automatically detect alertness in humans by monitoring and analyzing brain wave signals (13) Steps include: acquiring the brain waves (EEG or MEG) data from the subject, digitizing the data, separating artifact data from raw data, and comparing trends in F-data alertness indicators, providing notification of inadequate alertness

Abstract: An improved inductive plethysmography sensor involving a conductor having alternating active and inactive segments. The active segments preferably have a narrow diamond shape which minimizes the possibility of artifact. Because of the conductor design, the sensors can be placed completely about the chest and abdomen with any overlap arranged so that active segments overlap inactive segments.

Abstract: We describe an algorithm that can achieve exact self-calibration for high-precision two-dimensional (2-D) metrology stages. Previous attempts to solve this problem have often given nonexact or impractical solutions. Self-calibration is the procedure of calibrating a metrology stage by an artifact plate whose mark positions are not precisely known. By assuming rigidness of the artifact plate, this algorithm extracts the stage error map from comparison of three different measurement views of the plate. The algorithm employs the orthogonal Fourier series to expand the stage error map, which allows fast numerical computation. When there is no random measurement noise, this algorithm exactly calibrates the stage error at those sites sampled by the mark array. In the presence of random measurement noise, the algorithm introduces a calibration error of about the same size as the random measurement noise itself, which is the limit to be achieved by any self-calibration algorithm. The algorithm has been verified by computer simulation with and without random measurement noise. Other possible applications of this algorithm are also discussed.

Abstract: Non-2DFT k-space readout strategies are useful in fast imaging but prone to blurring when reconstructed off resonance. Field inhomogeneities or susceptibility variations, coupled with a long readout time, are the major sources of this artifact. Correction methods based on a priori off-resonance information such as an acquired field map have been proposed in the literature. An alternative approach estimates the spatially varying off-resonance frequency from the data itself before applying a correction. In this latter approach there is a tradeoff between the extent of correction and the chance of increased artifact due to estimation error. This paper introduces an improved algorithm for field map estimation which is both faster and more robust than the existing method. It uses a multi-stage estimation of the field map, starting from a coarse estimate both in frequency and space and proceeds towards higher resolution. The new algorithm is applied to phantom and in vivo images acquired with radial and spiral sequences to give sharper images.

Abstract: A novel magnetic resonance imaging technique (STAR-HASTE) based on pulsed arterial spin labeling using a single shot acquisition method is described for perfusion imaging. The method is similar to EPISTAR in using STAR (Signal Targeting with Alternating Radiofrequency) technique for pulsed radiofrequency labeling of inflowing blood, but uses a half-Fourier single shot turbo spin-echo (HASTE) sequence for data acquisition instead of echo-planar imaging (EPI). Our preliminary studies show that STAR-HASTE permits perfusion imaging to be performed without many of the artifacts encountered with other imaging methods based on EPI acquisition. The novel method not only provides similar perfusion information to that obtained by EPISTAR, as demonstrated in the functional brain imaging study, but also eliminates magnetic susceptibility artifacts and image distortion commonly observed in EPI images. Furthermore, this technique can be readily implemented in MR systems without EPI capability.

Abstract: The simulated annealing algorithm has been applied successfully to conditional simulation of categorical variables (e.g., rock or facies units) with the objective of improving the match between measured and modeled spatial variability. In some implementation schemes, however, spurious features termed “artifact discontinuities” may occur near conditioning data, especially during the “zero- temperature” case referred to as simulated quenching. This paper shows that artifact discontinuities can be avoided by considering the anisotropy of the spatial variability model, reducing the number of lag vectors used in the objective function, and providing a rudimentary initial configuration. Results from several test cases suggest that the artifact discontinuities might be caused by overly precise fitting of measured to modeled spatial variability.

Abstract: Motion artifact, caused by skin stretch near an electrode is a significant source of noise in ECG recording, particularly during ambulatory recordings and stress tests. With recessed Ag-AgCI electrodes, motion artifact results, primarily, from potentials generated by skin stretch at the electrode site. We have investigated adaptive removal of motion artifact using a skin stretch signal derived from sensors mounted on a foam electrode. Preliminary results indicate that adaptive removal of motion artifact can reduce motion artifact by as much as 12.5 dB. Keywords-electrocardiogram, adaptive filter, motion artifact.

Abstract: The present invention discloses a system and method for performing image-based diagnosis. In this invention, historical artifact images and corresponding actions for repairing the artifacts are acquired and stored in a database. The database of historical artifact images and corresponding actions is used to diagnose an incoming artifact image having an unknown fault.

Abstract: Our objectives were to further characterize an artifact related to the localized failure of the frequency-selective (FATSAT) fat suppression magnetic resonance (MR) imaging technique We constructed two phantoms simulating human orbital anatomy and imaged them on a 15-T MR scanner using (FATSAT) and short T1 inversion recovery (STIR) techniques of fat suppression The first phantom resembled orbit structural configurations; it was imaged in coronal and axial planes and in varying orientations with respect to the main magnetic field (Z axis) to study the features of the artifact and to reproduce the asymmetry seen in clinical cases We designed the second phantom to enable quantification of the change in artifact size with change in orientation We imaged the orbits of a normal human volunteer in similar planes and orientations, and compared the results to clinical cases demonstrating the artifact and true orbital disease The artifact identified with localized failure of FATSAT fat suppression manifested as regions of hyperintensity maximal at fat-air interfaces, with gradual fading of the increased signal with distance from the interfaces The artifact was most prominent when the interfaces were perpendicular to the axis of the main magnetic field (Z axis) The regions of increased brightness obscured normal orbital structures but were not associated with alterations in the geometry of these structures Changes in orientation of the interfaces with respect to the Z axis, both in the phantoms and normal volunteer, reproduced the asymmetry of fat suppression failure seen in clinical cases The relationship of size of the artifact to change in orientation was non-linear The artifact was not seen on STIR images We concluded that failure of FATSAT fat suppression may mimic orbital disease, particularly if asymmetric As predicted by the Maxwell electromagnetism equation, slight variations in orientation of the fat-air interface to the Z axis may produce large asymmetries in fat suppression failure in the orbit Confirmation may require either comparison with additional pulse sequences [T1-weighted spin echo (T1W SE) or STIR] or repositioning the patient's head to check for persistence of the finding with varying orientations

Abstract: PURPOSE The influence of dental alloys on MRI of the temporomandibular joint was studied using a phantom model for this joint METHODS At 1,5 T, 15 dental alloys and 14 of their most important components were investigated acquiring sagittal (FOV: 150 mm) and transverse (FOV: 250 mm) T1-weighted SE images In 11 cases, T1- and T2*-weighted FLASH images were measured additionally The artifacts were assessed qualitatively as well as quantitatively, and the samples were subdivided into four artifact categories RESULTS Ag, Cu, Ga, In, Tl, Sn, Zn, amalgam, the precious alloys, the Au-Pd and Ag-Pd alloys showed no artifacts (category I) Minimal artifacts below 10 mm on transverse images (category II) were found for Cr, Pd, Pt and for the Ni-Cr alloy Mn and the remaining non-precious alloys induced artifacts up to 30 mm (category III) Significant artifacts-more than 30 mm-(category IV) were caused by Ni-Cr and 18/8 wires and by Co, Fe, and Ni T2*-weighted FLASH proved to be more susceptible for artifacts than T1-weighted SE and FLASH techniques CONCLUSIONS In contrast to dental alloys for fixed prosthodontics, Ni-Cr- or 18/8 wires used for orthodontic bands can influence not only the image quality, but also the diagnostic reliability of MRI of the temporomandibular joint

Abstract: We documented and quantified Monsel's solution-related artifacts after cervical biopsies. All loop electrosurgical cone biopsy specimens over a 3-month period were reviewed for necrosis artifact of the surface epithelium. The degree of change was quantified and correlated with the antecedent use of Monsel's solution. Twenty-four cone biopsy specimens were evaluated. Three of the eight cone biopsy specimens obtained fewer than 10 days after the use of Monsel's solution showed definite changes. Between 10 and 18 days after the use of Monsel's solution, four of eight specimens showed change. After 18 days, none of eight specimens showed change. One specimen at 18 days showed focal changes that seemed to be related to the use of an unusually large amount of Monsel's solution, because the patient had had six biopsies within 2 days. The routine use of Monsel's solution may interfere with the ability to recognize and characterize disease process in cone biopsy specimens when the cone procedure is done within 3 weeks after the use of Monsel's solution.

Abstract: If design, as Simon (1981) claims, is what people do when they devise courses of action “aimed at changing existing situations into preferred ones” (p. 129), and if preferences are inherently contentious — “the preferable,” Perelman (1982) writes, is one of two kinds of opinion about which people argue (p. 23) — then design is as much about arguing as it is about planning and building. It follows that learning to be a designer is, at least in part, learning how to argue in certain ways. Unfortunately, research and scholarship on design have paid insufficient attention to argument and how rhetoricians might intervene to improve it. In this paper, I examine the ways one group of student designers argued on behalf of their work for an actual client. I try to answer the following questions: What claims did the students make when presenting their work to others? What evidence did they offer? What values did they appeal to? Finally, were their arguments any good? The analysis offered here participates in the more general project of exploring the shape of rhetorical practice in particular social and cognitive contexts. As formulated by Nelson, Megill, & McCloskey (1987), this project rests on two presuppositions: first, that argument is more unified than the division of academic fields implies; second, that it is more diverse than notions of unitary method or reason allow (pp. 4-5). A rhetoric of design, then, is one interested in the particular but recognizable arguments of design practice. My analysis diverges from Nelson, Megill, & McCloskey’s project, however, in two ways. First, the design/rhetoric relationship is here primarily an educational problem (and not, say, an epistemological one). That is, I am looking at the social and discursive activities of expert practice from the point of view of students learning that practice. Second, like Leff (1987), I am as concerned with what this research tells us about rhetoric as with what it tells us about a special field of knowledge or practice. By “design,” I mean here the work of architects, engineers, urban planners, and others who plan and build the material world. By “rhetoric,” I mean the arts of planned, social discourse. In examining the relationship between these two, I begin with the following observation: Design appears to involve a

Abstract: A method based on wavelet shrinkage theory is proposed to reduce the truncation artifact in magnetic resonance imaging (MRI). This wavelet-based method takes advantages of various optimal and near-optimal properties of wavelets and wavelet shrinkage, which cannot be achieved by the methods based on other basis. Another advantage is that its performance does not degrade significantly in an environment with low SNR, which is usually the case in MRI applications. Different wavelet bases, including a recently proposed shift-invariant wavelet basis, are explored for improving the performance of the proposed approach. The proposed method is analyzed and compared with the conventional technique, based on Fourier analysis, using both simulated and real MR images.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Abstract: The authors have assessed the possibility of artifacts that can arise from performing simultaneous PET and MR imaging using a small prototype MR compatible PET scanner (McPET). The scanner consists of a single ring of 72, 2/spl times/2/spl times/5 mm/sup 3/, LSO (lutetium oxyorthosilicate) crystals read out by 3 Phillips XP1722 multi-channel photomultiplier tubes (MC-PMT's). The crystals are connected to the MC-PMT pixels using 4 meter long, 2 mm diameter double clad optical fibers, thus allowing the PET electronics to reside outside the main magnetic field. Experiments have been performed to critically examine any susceptibility artifacts or electromagnetic interference artifacts in the MR images caused by the PET system. The MR images were acquired by using a Siemens Vision 1.5 T clinical scanner. In addition, artifacts in the PET images caused by the operation of the PET scanner inside the MR system were investigated. Biological tissue (fruit) and a T2-weighted spin echo sequence (TR=2000 ms, TE=99 ms) were used to examine susceptibility artifacts due to McPET's components (LSO, optical fibers) in the MR field of view. A uniform disk shaped phantom was imaged using a T1-weighted spin echo sequence (TR=280 ms, TE=12 ms) with and without the PET electronics switched on to determine electromagnetic interference effects. A range of MR pulse sequences were studied for any possible artifacts they might introduce in either the PET or MR images at different field strengths. The results demonstrate that it is possible to achieve artifact free PET and MR images simultaneously using the authors' McPET scanner with several different conventional MR scanners.

Abstract: Echo-planar imaging (EPI) is sensitive to motion despite its rapid data acquisition rate. Compared with traditional imaging techniques, it is more sensitive to motion or flow in the phase-encode direction, which can cause image artifacts such as ghosting, misregistration, and loss of spatial resolution. Consequently, EPI of dynamic structures (eg, the cardiovascular system) could benefit from methods that eliminate these artifacts. In this paper, two methods of artifact reduction for motion in the phase-encode direction are evaluated. First, the k-space trajectory is evaluated by comparing centric with top-down ordered sequences. Next, velocity gradient moment nulling (GMN) of the phase-encode direction is evaluated for each trajectory. Computer simulations and experiments in flow phantoms and rabbits in vivo show that uncompensated centric ordering produces the highest image quality. This is probably due to a shorter readout duration, which reduces T2* relaxation losses and off-resonance effects, and to the linear geometry of phantoms and vessels, which can obscure centric blurring artifacts.

Abstract: Traditional objective metrics for the quality measure of coded images such as the mean squared error (MSE) and the peak signal-to-noise ratio do not correlate with the subjective human visual experiences well, since they do not take human perception into account. Quantification of artifacts resulted from lossy image compression techniques is studied based on a human visual systems (HVS) model and the time-space localization property of the wavelet transform is exploited to simulate HVS in this research. As a result of our research, a new image quality measure by using the wavelet basis function is proposed. This new metric works for a wide variety of compression artifacts. Experimental results are given to demonstrate that it is more consistent with human subjective ranking.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Abstract: PURPOSE: To restrain generation of an artifact by performing Fourier transform and absolute value operation with respective divided areas on sampling data with respective divided areas when scanning is performed by dividing a spatial frequency area. CONSTITUTION: When echo data of areas Sr to Sg on (k) spaces is obtained by divided scanning, data of the respective areas are juxtaposed on the respective (k) spaces, and the other areas are set in 0, and Fourier transform is performed with respective areas, and complex imacje data Va to Vs composed of a real number part R and an imaginary number part I are obtained. Operation is performed on this absolute value, and afterwards, absolute value image data of the respective areas are added together, and a magnetic resonance image is formed. Since generation of an artifact in an adjacent part of the areas can be prevented by carrying out in this way, even if phases of sampled data collected in the respective areas are different from each other, generation of the artifact such as ringing can be prevented.

Abstract: A new optical alignment artifact under development at NIST is described. This artifact, referred to as a stepped microcone, is designed to assist users and manufacturers of overlay metrology tools in the reduction of tool-induced measurement errors. We outline the design criteria and diamond turning lathe techniques used for manufacturing this structure. The alignment methods using this artifact allow the separation of error components associated with the optical system or the mechanical positioning systems as encountered when performing measurements in different focal planes.Although some difficulties have been encountered when performing measurements in different focal planes. Although some difficulties have been encountered in the actual diamond turning process,the data presented show some improvements with the more recent prototypes which indicate that this method of fabrication will be useful. Photometer scan data and CCD image acquisition hardware show a significant optical response at the step edges from these structures. Initial analysis of the optical response of these edges shows sensitivity to the material used and the details of the manufacturing processes.

Abstract: An image data modification technique addresses certain image defects characteristic of still images derived from original video sources, such as television or videotape. A lack of vertical alignment of pixels in a single frame, causing a "wobble" or "jitter" artifact in the image, is detected and corrected by a series of algorithms.

Abstract: As with "nonphysiological" devices, sensors that directly measure physiological variables have the potential to measure unexpected signals and for the physiological parameter being measured to respond in an unexpected manner. We present the case of a dP/dt sensing pacing system that functioned normally for 2 months and then developed upper rate behavior due to the sensing of a high frequency artifact on the pressure recording. Our case and others cited reinforce the need for future physiological rate responsive pacemakers to incorporate a second sensor to provide for backup rate response in cases of inappropriate rate response.