bluuebunny/crossref_metadata_2025_split huggingface dataset:
Delineation of liver necrosis using double contrast‐enhanced MRI
Authors: Dupas Benoǐt , Bach‐Gansmo Tore , Nomballais Marie Françoise , Meflah Kahled 
Published: March 2007

AbstractThe purpose of this study was to demonstrate the potential usefulness of the combination of gadolinium and dysprosium to enhance the difference between normal and necrotic liver tissue. Small regions of acute necrosis were induced by injecting 200–300 μl of 95% alcohol into the liver of 26 rats. MRI was performed 24 hours after necrosis induction, before and immediately after injection of one or both contrast agents. Using a mixed T1/T2‐weighted sequence, the signal intensity (SI) of the normal liver was reduced by 70%, whereas the necrotic regions had more than a 50% increase in SI after double contrast. The region that was enhanced corresponded largely with the region of necrosis as observed postmortem. The lesion size, when identified, was largely underestimated using either of the agents alone, albeit using the common pulse sequences. The double contrast effect of simultaneous administration of gadolinium and dysprosium allows accurate delineation of liver necrosis.
Influence of copper on MRI of hepatocellular carcinoma
Authors: Matsuzaki Kenji , Sano Nobuya , Hashiguchi Norihisa , Yoshida Shusaku , Nishitani Hiromu 
Published: March 2007

AbstractThe purpose of this paper is to clarify whether copper accumulation in hepatocellular carcinoma (HCC) is a cause of high intensity signal pattern on T1‐weighted images (T1‐WI) by comparing the histologically proven copper accumulation with MR images. Forty‐five surgically resected HCCs were analyzed. Distribution patterns of divalent copper by a modified Timm's method on their maximum cut surfaces were compared with signal patterns on corresponding T1‐WI. The degree of copper accumulation in tumor compared with surrounding liver tissue was higher in 6 lesions, equal in 17 lesions, and lower in 22 lesions. High intensity pattern on T1‐WI were observed in 3 of 6 lesions (50%), 10 of 17 lesions (59%), and 10 of 22 lesions (45%). Distribution patterns of copper were not correlated with intensity patterns on T1‐WI. We conclude that the paramagnetic effect of divalent copper accumulation in HCC is insufficient to influence the MRI.
Effects of ami‐25 on liver vessels and tumors on T1‐weighted turbo‐field‐echo images: Implications for tumor characterization
Authors: Van Gansbeke Daniel , Metens Thierry M. , Matos Celso , Nicaise Nicole , Gay France , Raeymaekers Hubert , Struyven Julien 
Published: March 2007

AbstractThis study was devoted to tumor differentiation in liver MR T1‐weighted imaging with superparamagnetic iron oxide (SPIO). Twenty‐one patients with 40 liver lesions were studied at 1.5 T. Before and at least 45 minutes after SPIO administration, turbo‐field‐echo (TFE) T1‐weighted, TFE T1 × T2*‐weighted (MXT), and fat‐suppressed turbo‐spin‐echo T2‐weighted images were acquired. A quantitative analysis was performed blindly. On TFE T1‐weighted images, the signal enhancement was −33% ± 12 for the liver, −24% ± 2 for adenomas and focal nodular hyperplasia, +60% ± 33 for the hemangiomas; metastases and cyst enhancement were not significant. After SPIO on TFE T1‐weighted images, the hemangioma‐to‐liver signal ratio (149% ± 18) was definitely higher than the mean metastasis‐to‐liver signal ratio (90% ± 16). This T1‐related differentiation ability lacked dramatically on TFE MXT images and, in one case, was reduced on post‐SPIO TFE T1‐weighted images by a long imaging delay after SPIO administration (2 hours).
MR multispectral analysis of multiple sclerosis lesions
Authors: Mitchell J. Ross , Jones Craig , Karlik Stephen J. , Kennedy Karen , Lee Donald H. , Rutt Brian , Fenster Aaron 
Published: March 2007

AbstractAlthough quantification of the lesion burden from serial MR examinations of patients with multiple sclerosis (MS) is a common technique to assess disease activity in clinical trials, pathologic change may occur within a lesion without a corresponding change in volume. Therefore, measures of lesion volume and composition may improve the sensitivity of detecting disease activity. A new technique has been developed that provides information about the intensity composition of MS lesions in standard spin‐echo MR examinations. The new technique is based on the multispectral “feature space” intensity distributions of the lesions and normal tissues. Analysis of MR examinations of materials with known T1 and T2 times showed that feature space position from spin‐echo examinations is largely determined from proton density (ρ), T2, and the interecho delay. Information about intensity composition was obtained by reducing the multidimensional intensity distribution to one dimension while minimizing the loss of information. This technique was used to analyze eight lesions in standard spin‐echo MR examinations of three patients with MS. Lesion distributions were compared between examinations by first calibrating the examinations based on the intensity distributions of cerebrospinal fluid (CSF), an internal reference tissue. Many of the lesion distributions had a distinctive peak at low intensity, corresponding to normal‐appearing white matter (WM). Within the lesion distributions, increases in high intensity peaks generally were accompanied by reductions in the WM peak. Serial analysis of the lesion distributions revealed some dramatic fluctuations, even when lesion volume remained constant.
Signal‐to‐noise analysis of cerebral blood volume maps from dynamic NMR imaging studies
Authors: Boxerman Jerrold L. , Rosen Bruce R. , Weisskoff Robert M. 
Published: March 2007

AbstractThe use of cerebral blood volume (CBV) maps generated from dynamic MRI studies tracking the bolus passage of paramagnetic contrast agents strongly depends on the signal‐to‐noise ratio (SNR) of the maps. The authors present a semianalytic model for the noise in CBV maps and introduce analytic and Monte Carlo techniques for determining the effect of experimental parameters and processing strategies upon CBV‐SNR. CBV‐SNR increases as more points are used to estimate the baseline signal level. For typical injections, maps made with 10 baseline points have 34% more noise than those made with 50 baseline points. For a given peak percentage signal drop, an optimum TE can be chosen that, in general, is less than the baseline T2. However, because CBV‐SNR is relatively insensitive to TE around this optimum value, choosing TE ≈ T2 does not sacrifice much SNR for typical doses of contrast agent. The TR that maximizes spin‐echo CBV‐SNR satisfies TR/T1 ≈ 1.26, whereas as short a TR as possible should be used to maximize gradient‐echo CBV‐SNR. In general, CBV‐SNR is maximized for a given dose of contrast agent by selecting as short an input bolus duration as possible. For image SNR exceeding 20–30, the Γ‐fitting procedure adds little extra noise compared with simple numeric integration. However, for noisier input images, as can be the case for high resolution echo‐planar images, the covarying parameters of the Γ‐variate fit broaden the distribution of the CBV estimate and thereby decrease CBV‐SNR. The authors compared the analytic noise predicted by their model with that of actual patient data and found that the analytic model accounts for roughly 70% of the measured variability of CBV within white matter regions of interest.
Relative quantification of pulmonary edema with noncontrast‐enhanced MRI
Authors: Caruthers Shelton D. , Paschal Cynthia B. , Pou N. Adrienne , Harris Thomas R. 
Published: March 2007

AbstractPulmonary edema is a debilitating effect of acute respiratory distress syndrome. The ability to measure it noninvasively with high sensitivity and in three dimensions could be useful in not only detection but also in assessment and guidance of treatment. To this end, a three‐dimensional MRI pulse sequence to measure the formation of edema was developed and tested. Another sequence was tested to measure blood flow in distal pulmonary arteries. Pulmonary edema was induced in nine dogs via venous injections of oleic acid. Edema was verified by wet‐to‐dry weight ratio (5.30 ± .38) and extravascular lung water at baseline (2.03 ± 1.12 ml/g dry lung weight) versus postinjury (3.00 ± 1.45 ml/g) (P < .005). The signal‐to‐noise ratio within the lungs increased from 5.47 ± 1.00 at baseline to 7.51 ± 1.96 (P < .005), and the time course of edema formation was resolved. Results from MR phase‐contrast blood flow measurements were variable. The authors conclude that the three‐dimensional scan provides a sensitive relative quantification of pulmonary edema formation without the use of contrast agents or ionizing radiation.
Measurement of collateral blood flow in a porcine model of aortic coarctation by velocity‐encoded cine MRI
Authors: Chernoff Daniel M. , Derugin Nikita , Rajasinghe Hiran A. , Hanley Frank L. , Higgins Charles B. , Gooding Charles A. 
Published: March 2007

AbstractThe purpose of this study was to investigate the time course of development of collateral blood flow in an animal model of aortic coarctation. A juxtaductal aortic stenosis (model coarctation) was surgically created in five juvenile pigs. MRI was performed preoperatively, 1 to 2 days postoperatively, and 2 to 10 weeks postoperatively. Aortic blood flow was measured by velocity‐encoded cine MR (VENC‐MR). The percent change in aortic blood flow (ΔBF) from proximal to distal descending thoracic aorta was calculated, and a multiple‐comparison paired t test used to assess changes in ΔBF over time. Invasive flow measurements were obtained in one animal before sacrifice using an ultrasonic probe. ΔBF preoperatively was −2 ± 8% (mean ± SE). ΔBF increased to 32 ± 7% (mean ± SE, P = .022) 2 days postoperatively and 55 ± 19% (P = .032) 2 to 8 weeks postoperatively. Invasive measurements were in qualitative agreement with the VENC‐MR data. VENC‐MR is an accurate noninvasive method of measuring collateral blood flow in aortic coarctation. Recruitment and development of collateral flow pathways occur rapidly in an animal model.
Probing tumor microvascularity by measurement, analysis and display of contrast agent uptake kinetics
Authors: Parker Geoffrey J. M. , Suckling John , Tanner Steven F. , Padhani Anwar R. , Revell Patrick B. , Husband Janet E. , Leach Martin O. 
Published: March 2007

AbstractThis paper describes a measurement protocol for acquiring quantitative dynamic MRI data and novel analysis and display software (Magnetic Resonance Imaging Workbench (MRIW)). Proton density‐weighted and T1‐weighted two‐dimensional gradient echo images are used to quantify tissue contrast agent concentration. The dynamic studies last approximately 7 minutes, with 10‐second temporal resolution. Analyses of signal and concentration changes with time are performed, allowing capillary permeability‐surface area product, tissue leakage space, enhancement onset time, mean enhancement gradient and maximum enhancement level to be mapped as false‐color parametric overlays registered with anatomic images. Quantification of permeability and leakage space provides a method for comparing physiology in patients between visits or for intersite comparisons.
Triangular fibrocartilage and intercarpal ligaments of the wrist: Does MR arthrography improve standard MRI?
Authors: Zanetti Marco , Bräm Jakob , Hodler Juerg 
Published: March 2007

AbstractThe objective of this study was to assess the value of adding MR arthrography to standard MRI for patients with chronic wrist disorders. Thirty consecutive patients (age range, 19–73 years; mean, 36.2 years) were included in the investigation. The images were evaluated blindly and separately by two radiologists with regard to lesions of the scapholunate (SL) and lunotriquetral (LT) ligaments and the triangular fibrocartilage (TFC). Conventional two‐ or three‐compartment arthrography was used as the standard of reference. For TFC lesions, standard MR images had a sensitivity of 92.3% (reader 1) and 84.6% (reader 2) and a specificity of 41.2% (reader 1) and 52.9% (reader 2). For MR arthrography, sensitivity was 84.6% (reader 1) and 84.6% (reader 2) and specificity was 88.2% (reader 1) and 100% (reader 2). For SL ligament tears, standard MRI had a sensitivity of 33.3% (reader 1) and 11.1% (reader 2) and a specificity of 47.6% (reader 1) and 57.1% (reader 2). For MR arthrography, sensitivity was 66.7% (reader 1) and 55.6% (reader 2) and specificity was 52.4% (reader 1) and 81.0% (reader 2). For LT ligament tears, standard MRI had a sensitivity of 28.6% (reader 1) and 35.7% (reader 2) and a specificity of 93.8% (reader 1) and 81.3% (reader 2). For MR arthrography, sensitivity was 35.7% (reader 1) and 23.1% (reader 2) and specificity was 93.8% (reader 1) and 94.1% (reader 2). In conclusion, the diagnostic performance of MRI in suspected lesions of the TFC and the SL and LT ligaments is improved by adding MR arthrography to the standard examination.
Breath‐holding in healthy and pulmonary‐compromised populations: Effects of hyperventilation and oxygen inspiration
Authors: Marks Burton , Mitchell Donald G. , Simelaro John P. 
Published: March 2007

AbstractSuspension of respiration during end‐expiration often is recommended to minimize body organ displacement between sequential image acquisitions. The purpose of this report is to evaluate techniques for end‐expiratory breath‐holding applicable to a pulmonary‐compromised population. Eighty‐seven consecutive outpatients with chronic pulmonary diseases and 31 healthy nonsmoking volunteers were recruited for the study. All subjects were asked to hold their breath in end‐expiration while in the supine position (29 after breathing room air, 29 after hyperventilating room air for six breaths, and 29 after breathing O2 from a portable oxygen tank via nasal cannula until pulse‐oximeter readings stabilized or reached 100%). Each volunteer was tested with all three methods. The mean length of time for a breath‐hold on room air without hyperventilation was 9.2 seconds for the patients and 31.7 seconds for the volunteers. A breath‐hold after hyperventilation of room air was timed at 12.3 seconds for the patients and 41.2 seconds for the volunteers, and after O2 administration, the breath‐hold was 22.4 seconds for the patients and 60.9 seconds for the volunteers. No adverse effects occurred. The pulmonary‐compromised patient can suspend respiration most successfully after O2 administration (P < .0001), whereas hyperventilation seems to be less beneficial. Nonpulmonary‐compromised volunteers can hold their breath for longer periods of time.
MRI acoustic noise: Sound pressure and frequency analysis
Authors: Counter S. Allen , Olofsson Ake , Grahn H. F. , Borg Erik 
Published: March 2007

AbstractThe large gradient colls used in MRI generate, simultaneously with the pulsed radiofrequency (RF) wave, acoustic noise of high intensity that has raised concern regarding hearing safety. The sound pressure levels (SPLs) and power spectra of MRI acoustic noise were measured at the position of the human head in the isocenter of five MRI systems and with 10 different pulse sequences used in clinical MR scanning. Each protocol, including magnetization‐prepared rapid gradient echo (MP‐RAGE; 113 dB SPL linear), fast gradient echo turbo (114 dB SPL linear), and spin echo Tl/2 mm (117 dB SPL linear), was found to have the high SPLs, rapid pulse rates, amplitude‐modulated pulse envelopes, and multi‐peaked spectra. Slice thickness and SPL were inversely related, and Tl‐weighted images generated more intense acoustic noise than the proton‐dense T2‐weighted measures. The unflltered linear peak values provided more accurate measurements of the SPL and spectral content of the MRI acoustic noise than the commonly used dB A‐weighted scale, which filters out the predominant low frequency components. Fourier analysis revealed predominantly low frequency energy peaks ranging from .05 to approximately.
Contrast‐enhanced, k‐space‐centered, breath‐hold MR angiography of the renal arteries and the abdominal aorta
Authors: Steffens Johann‐C. , Link Johann , Grässner Joachim , Mueller‐Huelsbeck Stefan , Brinkmann Gisbert , Reuter Michael , Heller Martin 
Published: March 2007

AbstractThe purpose of this study was to evaluate the capability of contrast‐enhanced breath‐hold fast imaging with steady‐state precession (FISP) three‐dimensional MR angiography (MRA) to detect stenotic lesions of the abdominal aorta, the renal arteries, and the iliac arteries by using a k‐space‐centered 20‐ml gadolinium‐diethylene pentaacetic acid (Gd‐DTPA) bolus. Fifty patients were studied before conventional x‐ray angiography. Contrast‐enhanced breath‐hold FISP three‐dimensional MRA was applied in the coronal view, centered at the renal arteries. Twenty ml of Gd‐DTPA was used in all subjects. A test bolus was applied to determine the injection time for the k‐space‐centered bolus injection. Of 300 segments, 284 segments were classified correctly, 11 were overestimated, and five were underestimated. Sensitivity was 98%, specificity was 96%, positive predictive value was 96%, negative predictive value was 98%, and accuracy was 97%. Of the 50 patients studied, 43 were staged correctly. No venous overlay was seen in 31 patients; partial overlay was seen in 16 patients, and venous structure overlay obscuring arterial anatomy was found in two patients. Six of nine accessory renal arteries could be identified by MRA. Intraobserver variability was .94. This study has shown the ability of contrast‐enhanced breath‐hold FISP three‐dimensional MRA to detect and grade vascular lesions in the abdominal aorta and the renal arteries. The method may serve as a screening tool in the future.
MR navigator‐echo monitoring of temporal changes in diaphragm position: Implications for MR coronary angiography
Authors: Taylor Andrew M. , Jhooti Permi , Wiesmann Frank , Keegan Jennifer , Firmin David N. , Pennell Dudley J. 
Published: March 2007

AbstractTemporal changes in respiration could influence navigator‐echo (NE)‐gated MR coronary angiography (MRCA), but systematic investigation of the effects of such variations and how to limit them has not been performed. We addressed these issues by studying the influence of time in the magnet on diaphragm position and respiratory patterns using NE diaphragm monitoring in volunteers and a phantom model. NE diaphragm monitoring was performed at .5 T in 10 subjects over a total period of 35 minutes. The end‐expiratory position was sustained for longer (1.1 vs .4 seconds, P < .001) and with greater position stability (SD 1.9 vs 5.9 mm, P = .01) than the end‐inspiratory position. Drift of the end‐expiratory position occurred over time, causing a fall in scan efficiency (44–28%, P = .01). Up‐drift of the end‐expiratory position was most common. Loss of scan efficiency was worse with up‐drift because of loss of the end‐expiratory pause from the NE window (up‐drift 10% mm−1, down‐drift 7% mm−1, both P = .03). Scan efficiency also was reduced during sleep (to a nadir of 0%), secondary to loss of the end‐expiratory pause, periodic breathing with oscillating end‐expiratory position, and periods of apnea. The phantom model used actual diaphragm traces to evaluate the artifact resulting from diaphragm motion during acquisition. Artifact was considerably reduced by NE adaptive motion correction compared with NE gating alone (ghosting ratio 2.0 vs 2.8, P < .01). Artifact also was significantly reduced with up‐drift if scan efficiency was maintained above 35% (P = .05). For optimal NE‐gated MRCA, the following features are important: the NE window should be placed around the end‐expiratory position; subjects should not sleep; scan efficiency should be monitored and the NE window should be repositioned if scan efficiency falls below 35%; and adaptive motion correction should be used.
Flow‐independent angiography for peripheral vascular disease: Initial in‐vivo results
Authors: Gronas Rolf , Kalman Peter G. , Kucey Daryl S. , Wright Graham A. 
Published: March 2007

AbstractFlow‐independent angiography (FIA), an approach that isolates arterial blood using MR relaxation characteristics rather than flow effects, was evaluated for application in peripheral vascular disease (PVD). First, pilot studies were conducted in which FIA coronal projection images were obtained from controls and symptomatic patients with PVD to assess clinical utility. All control images corresponded to the expected leg arterial anatomy with little interference from deep veins (one of five) and muscle (zero of five). Superficial venous signal was less well suppressed in comparison to deep veins (four of five). Images of symptomatic patients were less consistent with difficulty suppressing muscle and deep venous signal in some cases and edema when present. We then compared T2 values for muscle (T2m, tibialis anterior), arterial blood (femoral and popliteal arteries), and venous blood (femoral, popliteal, and saphenous veins) in controls (n = 8) and symptomatic patients with intermittent claudication (n = 5) or ischemic rest pain (n = 7). Changes in T2 measurements of various tissues accounted for poorer contrast in symptomatic patients. Patients with ischemic rest pain had significantly higher T2m compared with controls (T2m = 39.3 ± 2.1 (1 standard error of the mean [SEM]) versus 30.9 ± .4, P < .01). For all measurements, other than saphenous vein, variances were greater in symptomatic patients. To realize the inherent advantages of FIA for this clinical application, additional work on suppression of signals from muscle, veins, and edema is required. One promising approach involves shifting from projection images to three‐dimensional acquisitions for improved tissue suppression.
Proximal coronary artery stenosis: Three‐dimensional MRI with fat saturation and navigator echo
Authors: Müller Markus F. , Fleisch Martin , Kroeker Randall , Chatterjee Tushar , Meier Bernhard , Vock Peter 
Published: March 2007

AbstractThe purpose of this study was to compare the diagnostic value of MR angiography (MRA) with conventional contrast angiography in coronary artery disease. Thirty‐five patients underwent MRA and coronary angiography within 4 hours. Of these, three patients were investigated twice: once before and once after balloon angioplasty. The pulse sequence was a cardiac‐triggered, single‐slab, three‐dimensional gradient‐echo sequence, employing a spin‐echo navigator echo measurement to track the variation of the diaphragm during the scan. The following segments of the coronary arteries were included in this prospective study: left main coronary artery, proximal and middle left anterior descending, proximal and middle left circumflex, proximal and middle right coronary artery, and intermediate branch, if present. In total, 176 segments were classified as normal or having a stenosis of less than 50% and as having a stenosis of more than 50%. Five patients were excluded because of lack of cooperation. Over all, 45 of 54 stenoses were detected and interpretable by MRA. Sensitivity, specificity, and positive and negative predictive values of MRA for detecting significant stenoses were 83%, 94%, 87%, and 93%, respectively. MRA identified significant stenoses within the major coronary arteries with a high degree of accuracy. Sensitivity and specificity are higher compared with exercise tests or scintigraphy or top of the precise localization.