bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantification of white matter and gray matter volumes from T1 parametric images using fuzzy classifiers
Authors: Herndon R. Craig , Lancaster Jack L. , Toga Arthur W. , Fox Peter T. 
Published: March 2007

AbstractWhite matter (WM) and gray matter (GM) were accurately measured using a technique based on a single standardized fuzzy classifier (FC) for each tissue. Fuzzy classifier development was based on experts' visual assessments of WM and GM boundaries from a set of T1 parametric MR images. The fuzzy classifier method's accuracy was validated and optimized by a set of T1 phantom images that were based on hand‐detailed human brain cryosection images. Nine sets of axial T1 images of varying thickness equally distributed throughout the brain were simulated. All T1 data sets were mapped to the standardized FCs and rapidly segmented into WM and GM voxel fraction images. Resulting volumes revealed that, in most cases, the difference between measured and actual volumes was less than 5%. This was consistent throughout most of the brain, and as expected, the accuracy improved to generally less than 2% for the 1‐mm simulated brain slices.
A model for detecting early metabolic changes in neonatal asphyxia by 1H‐MRS
Authors: Nakai Toshiharu , Rhine William D. , Enzmann Dieter R. , Stevenson David K. , Spielman Daniel M. 
Published: March 2007

AbstractIn newborn rabbits, the early cerebral metabolic changes caused by hypoxic‐ischemic (H‐I) insult was examined by using volume localized 1H‐MRS (STEAM). Partial ischemia was caused by unilateral carotid artery ligation, and hypoxia was induced by 10% oxygen inspiration for 150 minutes. Lactate immediately increased after hypoxia induction and almost disappeared 120 to 150 minutes after removal of hypoxia in both H‐I and hypoxia‐only experiments. Lactate production correlated well with decrease of the blood oxygen saturation. More lactate was produced on ischemic side 50 minutes post‐hypoxia induction in H‐I study. Ischemia alone did not cause any significant lactate production. Lactate caused by hypoxia can be dynamically monitored by localized 1H‐MRS. Existence of regional ischemia can induce greater anaerobic glycolysis and may affect the pattern of brain injury under hypoxia. 1H‐MRS is a sensitive tool to detect the acute metabolic changes caused by H‐I insult.
Rectal carcinoma: Prospective comparison of conventional and gadopentetate dimeglumine enhanced fat‐suppressed MR imaging
Authors: Okizuka Hiromi , Sugimura Kazuro , Yoshizako Takeshi , Kaji Yasushi , Wada Akihiko 
Published: March 2007

AbstractThe purpose of this study is to compare the usefulness of conventional MR imaging and gadopentetate dimeglumine enhanced fat‐suppressed MR imaging for the depiction and staging of rectal carcinoma. Thirty‐two patients were prospectively evaluated by MR imaging using a 1.5‐T unit. Based on the results of a barium study and/or digital examination, a balloon catheter was inserted to the level of the lesion before examination. Both conventional T1‐ and T2‐weighted images and gadopentetate dimeglumine enhanced fat‐suppressed T1‐weighted images were obtained for all patients. The kappa statistics were performed for the evaluation of interobserver agreement and the McNemar test was performed for the analysis of staging accuracy. When only T1‐ and T2‐weighted images were used, 5 of 32 tumors were not detected and the extent of 18 of 32 tumors were unclear. However, when gadopentetate dimeglumine enhanced fat‐suppressed imaging was added, 24 of 32 tumors were well defined and only one tumor was not detected. In determining the depth of invasion, the staging accuracy was 72% for conventional imaging and 68% for all images combined. There was no significant difference between with gadopentetate dimeglumine fat‐suppressed imaging and conventional imaging (P > .05). Use of gadopentetate dimeglumine (fat‐suppressed imaging) resulted in overestimation of muscular invasion, peri‐rectal fat invasion, and adjacent organ invasion in 12 patients, whereas nine patients were overestimated without the use of gadopentetate dimeglumine. In the detection of metastatic lymph nodes, gadopentetate dimeglumine enhanced fat‐suppressed imaging also was not useful. Tumor detection was excellent using gadopentetate dimeglumine enhanced fat‐suppressed images. However, the accuracy of staging was not improved by obtaining such images.
Intracapsular implant rupture: MR findings of incomplete shell collapse
Authors: Soo Mary Scott , Kornguth Phyllis J. , Walsh Ruth , Elenberger Charlotte , Georgiade Gregory S. , Delong David , Spritzer Charles E. 
Published: March 2007

AbstractThe objective of this study was to determine the frequency and significance of the MR findings of incomplete shell collapse for detecting implant rupture in a series of surgically removed breast prostheses. MR images of 86 breast implants in 44 patients were studied retrospectively and correlated with surgical findings at explanation. MR findings included (a) complete shell collapse (linguine sign), 21 implants; (b) incomplete shell collapse (subcapsular line sign, teardrop sign, and keyhole sign), 33 implants; (c) radial folds, 31 implants; and (d) normal, 1 implant. The subcapsular line sign was seen in 26 implants, the teardrop sign was seen in 27 implants, and the keyhole sign was seen in 23 implants. At surgery, 48 implants were found to be ruptured and 38 were intact. The MR findings of ruptured implants showed signs of incomplete collapse in 52% (n = 25), linguine sign in 44% (n = 21), and radial folds in 4% (n = 2). The linguine sign perfectly predicted implant rupture, but sensitivity was low. Findings of incomplete shell collapse improved sensitivity and negative predictive values, and the subcapsular line sign produced a significant incremental increase in predictive ability. MRI signs of incomplete shell collapse were more common than the linguine sign in ruptured implants and are significant contributors to the high sensitivity and negative predictive values of MRI for evaluating implant integrity.
Using cardiac phase to order reconstruction (CAPTOR): A method to improve diastolic images
Authors: Feinstein Jeffrey A. , Epstein Frederick H. , Arai Andrew E. , Foo Thomas K. F. , Hartley Michael R. , Balaban Robert S. , Wolff Steven D. 
Published: March 2007

AbstractA method is proposed to reconstruct multiphase images that accurately depicts the entire cardiac cycle. A segmented, gradient‐recalled‐echo sequence (FASTCARD) was modified to acquire data continuously. Images were reconstructed retrospectively by selecting views from each heartbeat based on cardiac phase rather than the time elapsed from the QRS complex. Cardiac phase was calculated using a model that compensates for beat‐to‐beat heart rate changes. Images collected using cardiac phase to order reconstruction (CAPTOR) depict the entire cardiac cycle and lack the temporal gap that is characteristic of prospectively reconstructed sequences. Time‐volume curves of the left ventricle capture the contribution of atrial contraction to end‐diastolic volume (EDV). Transmitral phase‐contrast flow measurements show a second peak inflow (a wave) that is absent in the standard sequence. Because atrial contraction contributes to ventricular EDV, images using CAPTOR potentially may provide a more reliable measure of EDV, stroke volume, and ejection fraction than standard techniques.
Model‐free reconstruction of three‐dimensional myocardial strain from planar tagged MR images
Authors: Denney Thomas S. , McVeigh Elliot R. 
Published: March 2007

AbstractA technique is presented for reconstructing a three‐dimensional myocardial strain map from a set of parallel‐tagged MR images. Radial strains were reconstructed from in vivo data from an anesthetized dog with values between .05 and .1 with a precision of ± .003 for a tag detection accuracy of .1 mm and a tag spacing of 2.5 mm. The reconstruction spatial resolution was demonstrated by reconstructing a localized displacement abnormality. In the circumferential direction, the abnormality that resulted in 50% displacement attenuation had a full width at half maximum of 5.4 ± .4 mm (mean ± SD). Graphs are presented showing the relationship between the size of an abnormality and the ability of the method to reconstruct that abnormality. The combination of high resolution parallel‐tagged MR images and the model‐free, coordinate system‐free strain reconstruction technique presented in this paper is capable of producing accurate, high resolution strain maps of the myocardium.
Effect of and correction for in‐plane myocardial motion on estimates of coronary‐volume flow rates
Authors: Frayne Richard , Polzin Jason A. , Mazaheri Yousef , Grist Thomas M. , Mistretta Charles A. 
Published: March 2007

AbstractThe sensitivities of phase‐difference (PD) and complex‐difference (CD) processing strategies to in‐plane motion were examined theoretically and experimentally. Errors in velocity and volume flow rate (VFR) estimates were attributed to (a) motion between different velocity encodings and, in the case of segmented k‐space acquisition strategies, (b) motion over the segment duration. PD estimates were found to be insensitive to in‐plane motion between velocity encodings, whereas CD VFR estimates were found to be sensitive to this motion. PD estimates, however, were affected by partial volume effects. A corrected CD (CD') scheme was developed that minimizes both partial‐volume and in‐plane motion effects. Segmented k‐space acquisitions with sequential offset and sequential interleaved offset (or centric) phase‐encoding schemes were studied. Images obtained using these techniques were found to include both blurring and replication artifacts. The amount of artifact generally increased with the number of views per segment (vps) and the in‐plane velocity. PD, CD, and CD' VFR estimates were found to be degraded by these artifacts. The sequential offset phase‐encoding scheme generally had acceptable VFR errors (at 4 vps, a CD' VFR error of 7.0%) when averaged over the physiologic range of myocardial motion (>12 cm second−1); however, larger errors were observed outside this range. VFR estimates obtained using the sequential interleaved phase‐encoding scheme at 4 vps were unacceptable. More accurate VFR measurements were obtained using a revised segmented PC strategy, which reversed the order in which the velocity and phase encodings were interleaved. The weighted average CD' VFR error obtained using the revised strategy was 24.5% (for 4 vps). Using displacement information obtained from the two velocity‐encoded images, an estimate of the in‐plane velocity was obtained and used to correct the acquired data. This decreased the VFR error (weighted average CD' error at 4 vps decreased from 24.5% to −6.3%); however, the implemented correction algorithm could potentially introduced other artifacts in the images.
Velocity encoding using both phase and magnitude
Authors: Madore Bruno , Henkelman R. Mark 
Published: March 2007

AbstractImaging time constitutes a major limitation of phase‐contrast (PC) angiography. It is possibly the main disadvantage of PC methods over the time‐of‐flight (TOF) methods that actually are used clinically. This relatively long imaging time comes from the fact that conventional PC methods require the acquisition of at least four images with different velocity sensitization to reconstruct a single angiogram (1, 2). However, more than one‐half of the information gathered through the acquisition of these four images is either redundant or simply discarded. We propose a faster approach to making PC angiograms in which the quantity of data acquired is diminished by as much as a factor 2. This is made possible by encoding velocity information in both the phase and magnitude of the image. Due to the use of extra radiofrequency (RF) and gradient waveforms, decreases in data requirements do not translate in a direct manner into decreases in imaging time. Nevertheless, significant reductions in imaging time are achieved with the present approach.
Multistep phase difference phase contrast imaging
Authors: Lamothe M. J. Reina , Rutt Brian K. 
Published: March 2007

AbstractA new technique for multistep phase‐contrast image processing is presented. The N‐step method consists of simply forming the linear average of the N — 1 adjacent phase‐difference signals. It has similar noise reduction properties as other multistep techniques, but the simplicity of the noise variance of the N‐step technique allows intuitive insight into phase‐difference phase‐contrast processing and noise reduction, which can aid in the design of efficient and improved phase‐contrast imaging sequences. As well, the computational simplicity of the N‐step phase‐difference technique compared with any other known multistep technique is advantageous. Like other multistep techniques, it has far more efficient noise reduction properties than simple two‐step, multiple average phase‐contrast imaging, even when normalized for total scan time. A three‐step phase‐difference velocity image has 50% less variance than an image acquired with two steps and two scans averaged but is obtained in 25% less scan time. Given its advantages, it should now be the chosen technique for increasing velocity‐to‐noise and contrast‐to‐noise ratios in all phase‐difference phase‐contrast clinical applications.
Localized 31P MR spectroscopy of the transplanted human kidney in situ shows altered metabolism in rejection and acute tubular necrosis
Authors: Heindel Walter , Kugel Harald , Wenzel Folker , Stippel Dirk , Schmidt Rainer , Lackner Klaus 
Published: March 2007

AbstractThe purpose of this study was to investigate the function of transplant kidneys in situ, and to detect pathologic changes, using volume‐selective phosphorous NMR spectroscopy (31P MRS). Localized 31P MR spectra were obtained from 37 patients using a whole‐body MR scanner with a combination of surface coils, adiabatic excitation pulses, and a modified image‐selected in vivo spectroscopy (ISIS) sequence. Seventeen patients with pathologic changes after renal transplant were compared with a control group of 20 patients with no evidence of transplant dysfunction. The transplant kidneys with rejection reaction showed higher ratios of inorganic phosphate (Pi) to adenosine triphosphate‐α (ATP‐α) than the normal control group (.4 ± .16 compared with .22 ± .11, P = .01) and reduced pH. The spectra of transplant kidneys with tubular necrosis had lower phosphomonoester (PME)/phosphodiester (PDE) ratios than the control group (.65 ± .35 compared with .96 ± .5, P = .04). The pathologies of rejection and tubular necrosis could be differentiated from each other by pH (6.93 ± .1 in rejection versus 7.14 ± .19 in tubular necrosis, P = .04). Preliminary results indicate that localized image‐guided 31P MR spectroscopy of transplant kidneys in situ can detect rejection reactions and acute tubular necrosis noninvasively, providing an incentive for further research.
A multicenter clinical trial of gadolite oral suspension as a contrast agent for MRI
Authors: Rubin Daniel L. , Falk Karen L. , Sperling Malcolm J. , Ross Michael , Saini Sanjay , Rothman Barry , Shellock Frank , Zerhouni Elias , Stark David , Outwater Eric K. , Schmiedl Udo , Kirby Louis C. , Chezmar Judith , Coates Terry , Chang Miles , Silverman Jeffery M. , Rofsky Neil , Burnett Keith , Engel Julie , Young Stuart W. 
Published: March 2007

AbstractThe purpose of this study was to assess the effectiveness and safety of Gadolite Oral Suspension as a gastrointestinal (GI) contrast agent for MRI in a phase II and two phase III multicenter clinical trials. Gadolite was administered to 306 patients with known or suspected abdominal and/or pelvic disease. MRI with T1‐ and T2‐weighted sequences was performed before and after ingestion. Efficacy was evaluated by having two masked readers rate the certainty of their MR diagnosis (0 = uncertain, 1 = probable, 2 = definite) on randomly presented pre‐ and post‐Gadolite Oral Suspension enhanced images. Principal investigators also evaluated the images and established the final diagnosis. Vital signs, clinical chemistries, and adverse events were documented. Blood and urine samples were analyzed for gadolinium content to determine whether Gadolite Oral Suspension was absorbed systemically. Certainty in MR diagnosis increased significantly (P < .001) for both blinded readers between pre‐ and post‐Gadolite images (.49–1.18 for reader 1; .46–1.53 for reader 2). Sensitivity, specificity, and accuracy also increased for both masked readers. No gadolinium was detected in blood or urine samples. There were no serious adverse events and no apparent drug‐related trends in mean vital signs or laboratory values. Gadolite is a highly effective, safe, and well tolerated contrast agent for clinical use with MRI.
Origin of cartilage laminae in MRI
Authors: Xia Yang , Farquhar Tony , Burton‐Wurster Nancy , Lust George 
Published: March 2007

AbstractTo understand the origin of the laminated appearance of cartilage in MRI (the magic angle effect), microscopic MRI (μMRI) experiments were performed at 14‐μm pixel resolution on normal canine articular cartilage from the shoulder joints. Two‐dimensional images of the spin‐spin relaxation time (T2) of the cartilage‐bone plug at two angles (0° and 55°) were calculated quantitatively. A distinct T2 anisotropy was observed as a function of the cartilage tissue depth. The surface and the deep regions exhibit strong orientational dependence of T2, whereas the upper‐middle region exhibits little orientational dependence of T2. These three μMRI regions correspond approximately to the three histologic zones in cartilage tissue. The results from the bulk T2 measurements agreed with these μMRI results. Our studies show that the laminated appearance of cartilage in MRI is caused by T2 anisotropy of the tissue. We further suggest that the molecular origin of the T2 anisotropy is the nuclear dipolar interaction. The structure of the cartilage tissue indicates that the collagen meshwork defines this T2 anisotropy. The results show that the T2 anisotropy provides an indirect but sensitive indicator for the orientation of macromolecular structures in cartilage. The clinical implications of this anisotropy are discussed.
Understanding pulsed magnetization transfer
Authors: Graham S. J. , Henkelman R. Mark 
Published: March 2007

AbstractUsing a two‐pool exchange model of magnetization transfer (MT), numeric simulations were developed to predict the time dependence of longitudinal magnetization in both semisolid and liquid pools for arbitrary pulsed radiofrequency (RF) irradiation. Whereas RF excitation of the liquid pool was modeled using the time‐dependent Bloch equations, RF saturation of the semi‐solid pool was described by a time‐dependent rate proportional to both the absorption lineshape of the semisolid pool and the square of the RF pulse amplitude. Simulations show good agreement with experimental results for a 4% agar gel aqueous system in which the two‐pool kinetics have been well studied previously. These simulations provide a method for interpreting pulsed MT effects, are easily extended to biologic tissues, and provide a basis for optimizing clinical imaging applications that exploit MT contrast.
Low power method for estimating the magnetization transfer bound‐pool macromolecular fraction
Authors: Lee Roland R. , Dagher Azar P. 
Published: March 2007

AbstractWe present a practical method to estimate the magnetization transfer (MT) bound‐pool fraction (Mb0). The method is based on a first‐order approximation of the saturation equation and allows an in vivo estimate of Mb0, previously estimated only in vitro and requiring multiple (on the order of 102) measurements. This method requires one saturation measurement, a T1 estimate, an accurate value for input power, and uses to advantage the low power limitations of clinical scanners. The approximation is shown to be feasible in expected tissue parameter ranges using simulations. Unlike the phenomenologic magnetization transfer ratio (MTR), Mb0 is a true tissue parameter representing the semisolid proton concentration involved in saturation transfer, allowing comparability of MT effect independent of input power, off‐resonance frequency, or equipment.
Phase imaging on a .2‐T MR scanner: Application to temperature monitoring during ablation procedures
Authors: Sinha Shantanu , Oshiro Thomas , Sinha Usha , Lufkin Robert 
Published: March 2007

AbstractProton phase shift imaging methods with keyholing were developed to rapidly monitor temperature during MR‐guided radiofrequency (RF) interventional procedures on a .2‐T open configuration scanner. Temperature calibration was performed on thermally controlled gel phantom and ex vivo bovine liver samples. Keyholing methods were implemented for rapid imaging and tested both in simulation experiments and in the gel phantom. Phase drifts from extraneous sources were monitored and compensated for using reference phantoms. Sequence parameters TE, TR, and flip angle (FA) were optimized for maximum temperature sensitivity and minimum noise. Reduction of phase noise from coupling of the magnetic field to external perturbations using navigator‐echo‐based correction schemes were also investigated. The extraneous phase drifts from the magnet could be minimized by keeping the electromagnet on continuously. Navigator echo corrected keyholed FLASH sequences (TE = 30 msec, TR = 60 msec, FA = 40°, 64 × 128 matrix) were used to monitor the RF lesioning process in gel phantoms yielding images every 4 seconds with a temperature sensitivity of .015 ppm/°C. RF ablation in the bovine tissue was monitored using navigator‐echo‐corrected keyholed fast low angle shot (FLASH) sequences (TE = 30 msec, TR = 100 msec, FA = 40°, 128 × 256 matrix) with a temporal resolution of 13 seconds and a temperature sensitivity of .007 ppm/°C. The results indicate that monitoring of an RF ablation procedure by mapping temperature with sufficient temporal resolution is possible using phase images of FLASH sequences on a .2‐T open scanner.
MRI diagnosis and follow‐up of subcutaneous fat necrosis
Authors: López Jorge A. , Saez Fermín , Larena J. Alejandro , Capelastegui Ana , Martín Jose I. , Canteli Begoña 
Published: March 2007

AbstractThe purpose of this report is to present the MRI features of subcutaneous fat necrosis (SFN) and the natural history of this process. We have seen 12 patients with SFN, one case of which was confirmed histopathologically. In six patients, a follow‐up MRI study was performed. MRI findings were very similar in all of the cases: small, linear, and spiculated lesions with one or two components: a globular area yielding high signal intensity on T1‐weighted images, intermediate to high signal intensity on fast SE T2‐weighted images and focal signal void on short‐inversion ‐time inversion recovery (STIR) sequence, corresponding to an area of fat necrosis; and a laminar starred component, with low signal intensity on T1 and fast SE T2‐weighted images and high signal intensity on the STIR sequence, corresponding to reactive fibrous tissue. The follow‐up MRI study of six patients showed either disappearance (n = 2) or decrease in size (n = 3) of the globular component; in one patient, no change was observed. A less prominent decrease of the laminar component also was seen in five patients. One patient did not present any change in this laminar component. The most characteristic MRI findings of this lesion are the high signal intensity areas on T1‐weighted images, their small size (<3 cm), their linear spiculated shape with both laminar and globular components, and no contrast enhancement after injection of gadolinium‐diethylenetriamine pentaacetic acid (Gd‐DTPA) injection. We believe that the location, size, morphology, and MRI signal intensity of SFN may allow its differentiation from other types of soft tissue lesions.