Improvements In Temporal Resolution Research Articles

Polarized neutron imaging using helium-3 cells and a polychromatic beam

Abstract We present the use of helium-3 spin filters for polarized neutron imaging of magnetic phenomena. These polarization devices allow improvements in both spatial (factor of 2–3) and temporal (factor of ∼5) resolution compared with previously used solid-state benders. This set-up has been used to visualize small-scale magnetic features in an Fe 65.7 Co 18 Si 0.8 B 15.5 foil with a thickness of 21–22 μm and a saturation magnetization of 1.7 T, and trapped magnetic flux in a superconducting lead cylinder.

In vitro evaluation of 56 coronary artery stents by 256-slice multi-detector coronary CT

Objective We sought to investigate stent lumen visibility of 56 coronary stents with the newest 256-multi-slice-CT (256-MDCT) technology for different reconstruction algorithms in an in vitro model. Background Early identification of in-stent restenosis (ISR) is important to avoid recurrent ischemia and prevent acute myocardial infarction (AMI). Since angiography has the disadvantage of high costs and its invasiveness, MDCT could be a convenient and safe non-invasive alternative for detection of ISR. Material and methods Percentages of in-stent lumen diameter and in-stent signal attenuation (measured as contrast-to-noise ratio (CNR)) of 56 coronary stents (group A ≤2.5 mm; group B = 2.75–3.0 mm; group C = 3.5–4.0 mm) were evaluated in a coronary vessel in vitro phantom (iodine-filled plastic tubes) employing four different reconstruction algorithms (XCD, CC, CD, XCB) on a novel 256-MDCT (Philips-iCT, collimation = 128 mm × 0.625 mm; rotation time = 270 ms; tube current = 800 mA s with 120 kV). Analysis was conducted with the semi-automatical full-width-at-half-maximum (FWHM) method. P-values <0.05 were regarded statistically significant. Results In-stent lumen diameter >60% for group C stents was significantly larger and CNR was significantly lower (both p < 0.05) for sharp kernels (CD; XCD) when compared to groups A/B. The FWHM-method showed significantly smaller in-stent lumen diameter ( p < 0.05) when compared to the manual method. Conclusion 256-MDCT could potentially be employed for clinical assessment of stent patency in stents >3.0 mm when analysed with cardio-dedicated sharp kernels, although clinical studies corroborating this claim should be performed. However, stents ≤3.0 mm reconstructed by soft kernels revealed insufficient in-stent lumen visualisation and should not be used in clinical practice. Further improvements in spatial and temporal image resolution as well as reductions of radiation exposure and image noise have to be accomplished for the ambitious goal of characterising both CT coronary artery anatomy and in-stent lumen.

Temporal resolution improvement in cardiac CT using PICCS (TRI‐PICCS): Performance studies

The recently proposed prior image constrained compressed sensing (PICCS) method has been applied in cardiac MDCT to improve the temporal resolution by approximately a factor of 2, by using projection data acquired from half of the standard short-scan angular range to reconstruct images with improved temporal resolution. The method was referred to as temporal resolution improvement using PICCS (TRI-PICCS). The primary purpose of this article is to study (1) the relationship between the performance of the TRI-PICCS algorithm and the angular range of projection data used in image reconstruction; (2) the relationship between the performance of the TRI-PICCS algorithm and the motion orientations and motion patterns of moving objects; and (3) the relationship between the performance of the TRI-PICCS algorithm and various heart rates. A hybrid phantom consisting of realistic cardiac anatomy and eight moving objects with known motion profiles to simulate coronary arteries was constructed by superimposing the analytical projection data of eight simulated moving vessels to the in vivo projection data from a cardiac MDCT scan. The motion profiles of the moving objects may independently change orientations, period, and amplitude. A prior image was reconstructed using a short-scan filtered backprojection method from a gated short-scan data set for each given motion profile. The TRI-PICCS method was applied to improve temporal resolution for each configuration of given motion profiles of moving objects and given active angular range specified by the target temporal resolution. To quantitatively study the performance, figures of merit were introduced to quantify signal intensity deficit, image distortion, and residual motion artifacts, respectively. The performance of the TRI-PICCS method is the same when the projection data are taken from 100 degrees to 120 degrees. The performance of the TRI-PICCS method is independent of location and motion orientations. The performance of the TRI-PICCS method does not significantly degrade for heart rates up to 100 bpm with a gantry rotation speed of 350 ms per rotation. The TRI-PICCS method can be used to systematically improve temporal resolution for MDCT cardiac imaging by a factor of 2-2.3 and the performance of the TRI-PICCS method is insensitive to motion locations and motion orientations. The TRI-PICCS method enables a single-source MDCT scanner with 350 ms or faster gantry speed to scan patients with heart rates as high as 100 bpm.

Multisensory Perceptual Learning of Temporal Order: Audiovisual Learning Transfers to Vision but Not Audition

BackgroundAn outstanding question in sensory neuroscience is whether the perceived timing of events is mediated by a central supra-modal timing mechanism, or multiple modality-specific systems. We use a perceptual learning paradigm to address this question.Methodology/Principal FindingsThree groups were trained daily for 10 sessions on an auditory, a visual or a combined audiovisual temporal order judgment (TOJ). Groups were pre-tested on a range TOJ tasks within and between their group modality prior to learning so that transfer of any learning from the trained task could be measured by post-testing other tasks. Robust TOJ learning (reduced temporal order discrimination thresholds) occurred for all groups, although auditory learning (dichotic 500/2000 Hz tones) was slightly weaker than visual learning (lateralised grating patches). Crossmodal TOJs also displayed robust learning. Post-testing revealed that improvements in temporal resolution acquired during visual learning transferred within modality to other retinotopic locations and orientations, but not to auditory or crossmodal tasks. Auditory learning did not transfer to visual or crossmodal tasks, and neither did it transfer within audition to another frequency pair. In an interesting asymmetry, crossmodal learning transferred to all visual tasks but not to auditory tasks. Finally, in all conditions, learning to make TOJs for stimulus onsets did not transfer at all to discriminating temporal offsets. These data present a complex picture of timing processes.Conclusions/SignificanceThe lack of transfer between unimodal groups indicates no central supramodal timing process for this task; however, the audiovisual-to-visual transfer cannot be explained without some form of sensory interaction. We propose that auditory learning occurred in frequency-tuned processes in the periphery, precluding interactions with more central visual and audiovisual timing processes. Functionally the patterns of featural transfer suggest that perceptual learning of temporal order may be optimised to object-centered rather than viewer-centered constraints.

076 Dual source computed tomography for characterisation of coronary atherosclerotic plaques. A comparison with virtual histology intravascular ultrasound

<h3>Background</h3> Non invasive plaque characterisation is important for risk stratification. Dual Source CT (DSCT) offers a significant improvement in temporal resolution over single source CT and may be a non invasive method to classify plaque components. Although CT plaque images have previously been compared with greyscale IVUS they have not been validated against virtual histology intravascular ultrasound (VH-IVUS), a technology which involves spectral analysis of IVUS radiofrequency signals. VH-IVUS is the gold standard for in vivo plaque classification, with proven validation against histology. Our aim was to show that DSCT could distinguish between plaque components as defined by VH-IVUS on the basis of their attenuation values in Hounsfield units (HU). <h3>Methods</h3> Twenty-one patients underwent DSCT and VH-IVUS prior to coronary stenting. Twenty-six plaques with VH-IVUS plaque burden &gt;40% were chosen. Plaques were either homogenous for fibrous plaque or contained large confluent areas of calcified plaque or a necrotic core. The VH- IVUS images were co-registered with the corresponding CT image by an unblinded observer. Accurate matching of lesions was performed by using measurements of distance from the coronary ostia. The images were orientated using fiduciary markers (side branches or characteristic calcifications). Multiple regions of interest (ROI) were placed within the plaque components and lumen on the cross sectional CT images in areas that had been pre-classified on the VH-IVUS images (Abstract 76 Figure 1). The density of these ROIs were measured (expressed in HU) and assigned to the relative plaque type or lumen. <h3>Results</h3> Attenuation values for 171 ROIs (necrotic core 28, fibrous plaque 38, calcified plaque 29 and lumen 76) were measured from the 26 plaques. Mean and standard deviation attenuation values were 35+/−17 HU, 128+/−49 HU, 719+/−237 HU and 362+/−51 respectively (Abstract 76 Table 1). There were statistically highly significant differences in the attenuation values among the four groups (necrotic core, fibrous plaque, calcified plaque and lumen) by nonparametric Kruskal–Wallis test (p&lt;0.0001) (Abstract 76 Figure 2). <h3>Conclusions</h3> VH-IVUS-defined plaque components have characteristic attenuation values that differ significantly enough to be differentiated by DSCT. This classification may facilitate non-invasive coronary plaque characterisation using DSCT for both therapeutic drug trials and assessment of vascular risk.

Tracking and Quantitative Analysis of Dynamic Movements of Cells and Particles

Understanding complex cellular processes requires investigating the underlying mechanisms within a spatiotemporal context. Although cellular processes are dynamic in nature, most studies in molecular cell biology are based on fixed specimens, for example, using immunocytochemistry or fluorescence in situ hybridization (FISH). However, breakthroughs in fluorescence microscopy imaging techniques, in particular, the discovery of green fluorescent protein (GFP) and its spectral variants, have facilitated the study of a wide range of dynamic processes by allowing nondestructive labeling of target structures in living cells. In addition, the tremendous improvements in spatial and temporal resolution of light microscopes now allow cellular processes to be analyzed in unprecedented detail. These state-of-the-art imaging technologies, however, provide a huge amount of digital image data. To cope with the enormous amount of image data and to extract reproducible as well as quantitative information, computer-based image analysis is required. In this article, we describe methods for computer-based analysis of multidimensional live cell microscopy images and their application to study the dynamics of cells and particles. First, we sketch a general workflow for quantitative analysis of live cell images. Then, we detail computational methods for automatic image analysis comprising image preprocessing, segmentation, registration, tracking, and classification. We conclude with a discussion of quantitative analysis and systems biology.

Physics-based image enhancement for infrared thermography

Thermal imaging with an infrared camera can be used to view the location and intensity of heat sources in space and time. In a thermal conductor, thermal diffusion blurs out those heat sources. Knowledge of the physics of thermal diffusion can be used to enhance the spatial and temporal resolution of thermal images. In two dimensions, quantitative reconstruction of the heat source intensity is possible. The same algorithm applied to three-dimensional heat flows provides dramatic improvements in temporal and spatial resolution of the thermal images. Performance is illustrated both in theory and by experiment. An application example demonstrates utility to nondestructive evaluation.

Improvement of chromatic temporal resolution during smooth pursuit eye movement

Improvement of chromatic temporal resolution during smooth pursuit eye movement

MR Imaging of small bowel in Crohn's disease

MR and CT techniques optimized for small bowel imaging are playing an increasing role in the evaluation of small bowel disorders. Several studies have shown the advantage of these techniques over traditional barium fluoroscopic examinations secondary to improvements in spatial and temporal resolution combined with improved bowel distending agents. The preference of MR vs. CT has been geographical and based on expertise and public policy. With the increasing awareness of radiation exposure, there has been a more global interest in implementing techniques that either reduce or eliminate radiation exposure [Brenner DJ, Hall EJ.

MR Cholangiopancreatography at 3.0 T

The rapid evolution of magnetic resonance (MR) imaging technology has produced much-needed improvements in temporal and spatial resolution that have led to greater recognition of diseases of the hepatobiliary and pancreatic ducts at MR cholangiopancreatography. This modality often substitutes for diagnostic evaluations with endoscopic retrograde cholangiopancreatography and percutaneous transhepatic cholangiography. Recent innovations in whole-body MR imaging, including fast imaging sequences, phased-array coils, parallel imaging techniques, and 3.0-T magnets, allow the acquisition of higher-quality diagnostic images in less time. An understanding of these technical advances and their potential clinical applications, limitations, and pitfalls for cholangiopancreatographic evaluation is as essential as a familiarity with the spectrum of possible findings; both are needed to accurately identify and characterize the disease process and to provide effective guidance for treatment.

Visualising Liquid Water in PEM Fuel Cells Using Neutron Imaging

AbstractIn this article, we review the neutron imaging techniques that have been used to visualise liquid water in PEM fuel cells. A list of the various facilities engaged in this research is provided and the published literature in this field reviewed. Neutron imaging has been successfully used to visualise water dynamics in the flow channels of operating fuel cells. This technique has also been used to understand water removal mechanisms and the importance of membrane hydration and GDL flooding to optimal fuel cell performance. More recently this technique has been applied to imaging the water in fuel cell cross‐sections in order to quantify the water contents in the different components of an operating fuel cell. Finally, this technique has also been utilised to examine ice formation during sub‐zero operation of single fuel cells. With ongoing improvements in spatial and temporal resolution, neutron imaging can be expected to play a greater role in any fuel cell development related to water transport.

Background, status and future of the Transmission Electron Aberration-corrected Microscope project

The strong interaction of electrons with small volumes of matter make them an ideal probe for nanomaterials, but our ability to fully use this signal in electron microscopes remains limited by lens aberrations. To bring this unique advantage to bear on materials research requires a sample space for electron scattering experiments in a tunable electron-optical environment. This is the vision for the Transmission Electron Aberration-corrected Microscope (TEAM) project, which was initiated as a collaborative effort to re-design the electron microscope around aberration-correcting optics. The resulting improvements in spatial, spectral and temporal resolution, the increased space around the sample and the possibility of exotic electron-optical settings will enable new types of experiments. This contribution will give an overview of the TEAM project and its current status, illustrate the performance of the TEAM 0.5 instrument, with highlights from early applications of the machine, and outline future scientific opportunities for aberration-corrected microscopy.

Cardiovascular magnetic resonance imaging as applied to patients with pulmonary arterial hypertension

Numerous imaging techniques are currently used to evaluate pulmonary arterial hypertension (PAH), including echocardiography, x-ray, electrocardiogram (ECG), computed tomography and magnetic resonance imaging (MRI). All such modalities have inherent advantages and disadvantages governed by physical principles that result in their clinical utility. In that PAH is a progressive disorder characterised by abnormally elevated blood pressure of the pulmonary circulation that leads to extensive vascular remodelling and increased pulmonary vascular resistance, a technique that can encapsulate those specific features that depict the multiple facets of this disease has obvious advantages. Recent advances in cardiovascular MRI (CMR) technology have led to the development of dedicated techniques for non-invasive assessment of cardiovascular structure and function, including haemodynamical parameters in the pulmonary circulation, which are superior in their identification of pulmonary arterial right ventricular morphological changes. These advantages make CMR a very attractive modality for diagnosing, following and providing prognoses for PAH patients. In this review, we highlight the developments in the use of CMR for the diagnosis, assessment and monitoring of patients with PAH. These remarkable improvements in image acquisition, physiological imaging and contrast techniques place CMR in a prime position for defining this disease. In the coming decade, it is anticipated that continued improvements in CMR image acquisition, spatial and temporal resolution and analytical techniques will result in improved understanding of PAH pathophysiology, diagnosis and prognostic variables, as well as the replacement of the most, if not all, invasive procedures currently applied routinely to the evaluation of PAH.

TU-D-304A-03: Temporal Resolution Improvement Using PICCS in MDCT Cardiac Imaging

Purpose: The current paradigm for temporal resolution improvement is to add more source‐detector units and/or increase the gantry rotation speed. The purpose of this letter is to present an innovative alternative method to improve temporal resolution by at least a factor of 2 for all MDCT scanners, without requiring hardware modification. Methods: The central enabling technology is a most recently developed image reconstruction method: Prior Image Constrained Compressed Sensing (PICCS). Using the method, cardiac CTimages can be accurately reconstructed using projection data acquired in an angular range of about 120 degrees, which is roughly 50% of the standard short‐scan angular range (∼240 degrees for an MDCT scanner). As a result, the temporal resolution of MDCT cardiac imaging can be universally improved by approximately a factor of 2. In order to validate the proposed method, two in vivo animal experiments were conducted using a state‐of‐the‐art 64‐slice CTscanner(GE Healthcare, Waukesha, WI) at different gantry rotation times and different heart rates. One animal was scanned at heart rate of 83 beat per minute (bpm) using 400ms gantry rotation time and the second animal was scanned at 94bpm using 350ms gantry rotation time respectively. Results: Cardiac coronary CTimaging can be successfully performed at high heart rates using a single source MDCT scanner with gantry rotation time of 400ms and 350ms. Conclusions: Using the proposed PICCS method, temporal resolution of cardiac CTimaging can be effectively improved by approximately a factor of two without modifying any scanner hardware. This potentially provides a new method for single source MDCT scanners to achieve motion artifact‐free coronary CTimaging for most patients without prescription of beta blocker. This method also enables dual source MDCT scanner to achieve higher temporal resolution without further hardware modifications.

Temporal resolution improvement using PICCS in MDCT cardiac imaging

The current paradigm for temporal resolution improvement is to add more source-detector units and/or increase the gantry rotation speed. The purpose of this article is to present an innovative alternative method to potentially improve temporal resolution by approximately a factor of 2 for all MDCT scanners without requiring hardware modification. The central enabling technology is a most recently developed image reconstruction method: Prior image constrained compressed sensing (PICCS). Using the method, cardiac CT images can be accurately reconstructed using the projection data acquired in an angular range of about 120 degrees, which is roughly 50% of the standard short-scan angular range (approximately 240 degrees for an MDCT scanner). As a result, the temporal resolution of MDCT cardiac imaging can be universally improved by approximately a factor of 2. In order to validate the proposed method, two in vivo animal experiments were conducted using a state-of-the-art 64-slice CT scanner (GE Healthcare, Waukesha, WI) at different gantry rotation times and different heart rates. One animal was scanned at heart rate of 83 beats per minute (bpm) using 400 ms gantry rotation time and the second animal was scanned at 94 bpm using 350 ms gantry rotation time, respectively. Cardiac coronary CT imaging can be successfully performed at high heart rates using a single-source MDCT scanner and projection data from a single heart beat with gantry rotation times of 400 and 350 ms. Using the proposed PICCS method, the temporal resolution of cardiac CT imaging can be effectively improved by approximately a factor of 2 without modifying any scanner hardware. This potentially provides a new method for single-source MDCT scanners to achieve reliable coronary CT imaging for patients at higher heart rates than the current heart rate limit of 70 bpm without using the well-known multisegment FBP reconstruction algorithm. This method also enables dual-source MDCT scanner to achieve higher temporal resolution without further hardware modifications.

Noninvasive Coronary Angiography Using Dual-Source Computed Tomography in Patients With Atrial Fibrillation

Despite constant improvements in scanner technology, reliable visualization of the coronary arteries with multislice spiral CT angiography (CTA) remains a major challenge in patients with atrial fibrillation (AF). The purpose of this study was to assess the image quality of coronary CT angiograms with coronary angiography, using a dual-source CT scanner (DSCT), comparing systolic and diastolic reconstruction techniques. Additionally, we sought to evaluate the diagnostic accuracy of DSCT with coronary angiography as the standard of reference. Sixty-eight patients with permanent AF were imaged on a DSCT system, with a temporal resolution of 82 milliseconds. The volume and flow rate of the contrast medium were adapted to the patient's body weight. The patients were not receiving any drugs for heart rate regulation. Each dataset was reconstructed at an absolute delay determined from the R wave at 300 milliseconds (ie, systolic reconstruction), as well as at 70% of the RR-cycle (diastolic reconstruction). Twenty-one patients underwent both DSCT and coronary angiography. Two blinded independent readers assessed significant stenoses (> or =50%), and image quality in terms of visibility and artifacts (4-point rating scale: 1 = excellent, 2 = good, 3 = poor, 4 = insufficient) on a per-patient- and a per-segment-based analysis (15-segment AHA model) for both the systolic and diastolic datasets. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated. : During 68 DSCT examinations, the mean heart rate ranged between 26 and 181 beats per minute (77 +/- 25). In the patient-based analysis, the image qualities of 64 of 68 CT angiograms (94%) were high enough to permit diagnosis, ie, 4 of 68 (6%) datasets were considered nonevaluable. Segment-based, a total of 898 of 979 coronary artery segments were rated as diagnostically evaluable (92%).In 57 of 68 evaluable patients (84%) the reconstructions in stole had fewer motion artifacts and thus showed superior image quality. The median image quality of all CT datasets was 2. In 21 patients undergoing both coronary angiography and DSCT, the overall sensitivity, specificity, positive predictive value, and negative predictive value for the diagnosis of significant stenoses were 89% (16 of 18), 98% (260 of 265), 76% (16 of 21), and 99% (260 of 262), respectively, in the per-segment analysis (including 283 vessel segments) and 90% (9 of 10), 82% (9 of 11), 82% (9 of 11), and 90% (9 of 10), respectively, in the patient-based analysis. The image quality of coronary CT angiograms obtained with a DSCT is satisfactory in most patients with AF. In the majority of patients with high and irregular heart rate, the absolute forward approach with end-systolic reconstruction 300 milliseconds after the R-peak yield a higher image quality than diastolic reconstructions. As a result of a significant improvement in temporal resolution, DSCT coronary angiography is feasible in patients with AF and can be used to exclude coronary artery disease in this patient cohort.

Application of an Ultrasonic array sensor to air-water bubbly flow measurement

The ultrasonic array sensor, which has been successfully applied in the field of medical diagnostics and non-destructive testing, was applied to single-phase and two-phase flow measurement. The applied array sensor has 128 elements on the surface and each of them has a basic frequency of 8 MHz. Flow measurement using the array sensor is very effective, because it can obtain the cross-sectional flow visualization images from outside the pipe without disturbing flows. In this study, the ultrasonic sound pressure distributions were measured by the sound field measuring system, and the ultrasonic beam characteristics and the grouping effects of elements were investigated from the sound pressure field. The velocity profiles of single-phase flows in a rectangular channel were measured with Ultrasonic Velocity Profiler (UVP) by scanning the parallel ultrasonic beam emitted from the array sensor. Furthermore, an ultrasonic array measuring system, which consists of a pulser/receiver, a multiplexer, an A/D converter and a signal processing device, was developed for the improvement of temporal resolution in bubbly flow measurement using the ultrasonic array sensor. Then the bubble distributions in the channel cross-section were confirmed by using the echo signals reflected from bubbles.

Comprehensive evaluation of diastolic function with MRI

Introduction: Diastolic dysfunction is a contributing factor in most cardiovascular diseases. For example, from the ischemic cascade, it is well known that ventricular relaxation is impaired prior to changes in systolic function. Diastolic parameters are predictive of outcome in acute MI, and a third to a half of all cases of heart failure have preserved LVEF (>50%). The importance of diastolic dysfunction in the many manifestations of heart failure is not well characterized. Clinical evaluation of diastolic function is predominantly by echocardiography, for which several conventional and novel quantitative measures of function are available, the vast majority of which are not routinely acquired using MRI. With its increasing use in the clinic and with improvements in temporal resolution it is now practical for MRI to provide an equivalent or superior assessment of diastolic function. We illustrate the measurement of conventional and novel diastolic parameters using universally available clinical pulse sequences in healthy controls and a population of heart failure patients.

MR imaging of the small bowel in Crohn's disease

MR and CT techniques optimized for small bowel imaging are playing an increasing role in the evaluation of small bowel disorders. Several studies have shown the advantage of these techniques over tradition barium fluoroscopic examinations secondary to improvements in spatial and temporal resolution combined with improved bowel distending agents. The preference of MR vs. CT has been geographical and based on expertise and public policy. With the increasing awareness of radiation exposure, there has been a more global interest in implementing techniques that either reduce or eliminate radiation exposure [Brenner DJ, Hall EJ. Computed tomography—an increasing source of radiation exposure. N Engl J Med 2007;357:2277–84]. This is especially important in patients with chronic diseases such as inflammatory bowel disease who may require multiple studies over a lifetime or in studies that require sequential imaging time points such as in assessment of gastrointestinal motility [Froehlich JM, Patak MA, von Weymarn C, Juli CF, Zollikofer CL, Wentz KU. Small bowel motility assessment with magnetic resonance imaging. J Magn Reson Imaging 2005;21:370–75]. A recent study showed that certain subgroups of patients with Crohn's disease may be exposed to higher doses of radiation; those diagnosed at an early age, those with upper tract inflammation, penetrating disease, requirement of intravenous steroids, infliximab or multiple surgeries [Desmond AN, O’Regan K, Curran C, et al. Crohn's disease: factors associated with exposure to high levels of diagnostic radiation. Gut 2008;57:1524–29]. Therefore it has been suggested that techniques that can reduce or eliminate radiation exposure should be considered for imaging [Brenner DJ, Hall EJ. Computed tomography—an increasing source of radiation exposure. N Engl J Med 2007;357:2277–84]. Owing to the excellent softtissue contrast, direct multiplanar imaging capabilities, new ultrafast breath-holding pulse sequences, lack of ionizing radiation and availability of a variety of oral contrast agents, MR is well suited to play a critical role in the imaging of small bowel disorders. In this article we will review the technical issues related to the performance of MR enterography and enteroclysis and discuss the role and controversies of using MR in the assessment of inflammatory bowel disease.

Improvement of temporal resolution for three-dimensional continuous-wave electron paramagnetic resonance imaging

This paper describes improved temporal resolution for three-dimensional (3D) continuous-wave electron paramagnetic resonance (EPR) imaging. To improve temporal resolution, the duration of magnetic filed scanning that is used to obtain an EPR spectrum for each projection was reduced to 40 ms. The Helmholtz coil pair for field scanning was driven by triangular waves. The uniform distribution of projections was also used to reduce the number of projections for 3D image reconstruction. The reduction reaction of 4-hydroxy-2,2,6,6-tetramethyl-piperidinooxy with ascorbic acid was visualized by improved 3D EPR imaging techniques with a temporal resolution of 5.8 s.