bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regional cerebral blood volume measured by dynamic susceptibility contrast MR imaging in alzheimer's disease: A principal components analysis
Authors: Maas Luis C. , Harris Gordon J. , Satlin Andrew , English Camper D. , Lewis Robert F. , Renshaw Perry F. 
Published: March 2007

AbstractDynamic susceptibility contrast (DSC) MRI is an alternative to positron emission tomography (PET) and single photon emission computed tomography (SPECT) for the evaluation of cerebral hemodynamics in patients with Alzheimer's disease. DSC MRI allows the construction of high resolution images of cerebral blood volume (CBV) without the use of radionuclides or ionizing radiation. In this study, DSC MRI data were collected from 16 patients with probable Alzheimer's disease and 16 age‐matched control subjects. Characteristic patterns of regional CBV variation were found using principal component analysis. Three such patterns were identified: a global variation pattern, an anterior‐to‐posterior CBV gradient, and a temporoparietal pattern. Group differences in the principal component scores associated with the global and temporoparietal patterns (P = .08 and P = .007, respectively) suggest that these deficits reflect characteristic CBV abnormalities in Alzheimer's disease. Using only these two scores, the Alzheimer's disease group was classified with a sensitivity of 81% and a specificity of 88%. Additionally, disease severity, as measured by the Mini‐Mental State Examination (MMSE), was correlated significantly with the third principal component score (Pearson's r = .50, P = .05).
Effect of oxygen inhalation on relaxation times in various tissues
Authors: Tadamura Eiji , Hatabu Hiroto , Li Wei , Prasad Pottumarthi V. , Edelman Robert R. 
Published: March 2007

AbstractThe effect of the oxygen inhalation on relaxation times was evaluated in various tissues, including the myocardium, liver, spleen, skeletal muscle, subcutaneous fat, bone marrow, and arterial blood, with a [1H]MR system. Statistically significant decrease of T1 relaxation times was observed in the myocardium, spleen, and arterial blood after inhalation of 100% oxygen, whereas no significant change was observed in liver, skeletal muscle, subcutaneous fat, or bone marrow. The T2 relaxation time of these tissues did not differ significantly between before and after inhalation of the oxygen. These results indicate that [1H]MRI can be used to evaluate changes with oxygen inhalation and that the effect of the oxygen inhalation on T1 relaxation time is different among various tissues.
Preliminary experience with the application of Gadolinium‐DTPA before MR imaging‐guided laser‐induced interstitial thermotherapy of brain tumors
Authors: Kahn Thomas , Harth Thorsten , Bettag Martin , Ulrich Birgit Schwabe Frank , Schwarzmaier Hans‐Joachim , Modder Ulrich 
Published: March 2007

AbstractThe purpose of this study was to investigate the potential value of i.v. gadolinium‐diethylenetriamine penta‐acetic acid (Gd‐DTPA) applied before MRI‐guided laser‐induced interstitial thermotherapy (LITT) of brain tumors without original enhancement, especially in defining total lesion size during therapy. MRI‐guided LITT was performed on two patients with astrocytoma WHO II. For both patients, Gd‐DTPA was administered intravenously after a first irradiation period and LITT was continued after pulling back the light guide to coagulate the upper parts of the tumor. In both patients, the whole irreversible damaged zone of the second irradiation period after Gd‐DTPA showed an intense increase of signal intensity. The spatial expansion correlated with the diameter of an enhancing rim after Gd‐DTPA on follow‐up studies. Our preliminary results indicate that the application of Gd‐DTPA before MRI‐guided LITT may be of value in defining exactly the size of the irreversible damaged zone during therapy in nonenhancing brain tumors.
Dual dynamic contrast‐enhanced MR imaging
Authors: Miyati Tosiaki , Banno Tatsuo , Mase Mitsuhito , Kasai Harumasa , Shundo Hideo , Imazawa Masayoshi , Ohba Satoru 
Published: March 2007

AbstractA method was devised for obtaining dynamic contrast‐enhanced T1‐weighted and relaxation rate (ΔR2*) images simultaneously to evaluate regional hemodyn‐amics of the brain tumors. On a 1.5‐T MR system, dual dynamic contrast‐enhanced images were obtained using a gradient echo (dual echo fast field echo) pulse sequence with the keyhole technique to improve temporal and spatial resolution during a rapid bolus injection of gadopentetate dimeglumine. The dynamic T1 contrast images were obtained from the first echo; moreover.∫ ΔR2*dt values were calculated from the first and the second echo images. The dynamic T1 contrast images provided information about characteristic enhancement pattern (vascularization and disruption of bloodbrain barrier), and the f ΔR2*dt values provided a map of regional blood pool in tumor site, peritumoral edema, and other surrounding regions of the brain. The ability to obtain dynamic contrast‐enhanced T1 contrast and ΔR2* imaging at the same time allows optimization of the advantages of each and thereby more information about the microvascular circulation of the brain lesions.
Initial experience with dynamic MR imaging in evaluation of normal bone marrow versus malignant bone marrow infiltrations in humans
Authors: Bollow Matthias , Knauf Wolfgang , Korfel Agnieszka , Taupitz Matthias , Schilling Andreas , Wolf Karl‐Jürgen , Hamm Bernd 
Published: March 2007

AbstractThe purpose of this study was (a) evaluation of dynamic contrast‐enhanced MR imaging of normal bone marrow versus malignant bone marrow infiltrations in patients with proven B‐cell‐type chronic lymphocytic leukemia (B‐CLL) and (b) correlation with the clinical stage according to Binet (stages A, B, C) and response to therapy. Bone marrow imaging of the lumbar spine, pelvis, and proximal femurs was performed at 1.5 T in 45 patients without known malignancy and in 30 patients with B‐CLL. The differences between opposed‐phase and in‐phase dynamic gradient‐echo sequences before and up to 10 minutes after intravenous application of .1 mmol/kg body weight of gadolinium‐diethylenetriamine penta‐acetic acid (Gd‐DTPA) were evaluated in normal bone marrow. The contrast‐enhancement patterns of normal and malignant bone marrow were compared using the opposed‐phase dynamic gradient‐echo sequence. Ten of the patients with bone marrow infiltrations (Binet stage C) additionally underwent MR imaging follow‐up during therapy. Opposed‐phase gradient echo sequences demonstrated a signal decrease of normal bone marrow, and in‐phase gradient echo sequences demonstrated a signal increase of normal bone marrow after administration of Gd‐DTPA. The dynamic signal intensity time courses differed significantly (P < .05) between Binet stages B and C and controls as well as among the three Binet stages of B‐CLL. In the 10 patients followed during therapy, MR imaging sensitively demonstrated response (n = 6), nonresponse (n = 2), or relapse after initial response (n = 2). In out‐of‐phase imaging, both normal bone marrow and initial bone marrow infiltration in CLL stage Binet A show signal decrease after administration of contrast agent, whereas there is increase in signal intensity in higher‐grade bone marrow infiltration in Binet stage B or C disease. The signal loss of normal bone marrow in out‐of‐phase imaging is a phase effect rather than a T2* effect. The differentiation of initial from higher‐grade bone marrow infiltration on out‐of‐phase images relies solely on a shift in the fat/water ratio.
Phased array breath‐hold versus non‐breath‐hold MR imaging of focal liver lesions: A prospective comparative study
Authors: Yamashita Yasuyuki , Yamamoto Hiroaki , Namimoto Tomohiro , Abe Yasuko , Takahashi Mutsumasa 
Published: March 2007

AbstractThis study was undertaken to determine whether phased array breath‐hold T1‐ and T2‐weighted sequences can replace non‐breath‐hold spin echo (SE) sequences in the imaging of focal liver lesions by comparing overall image quality, liver‐lesion contrast, and artifact. Both breath‐hold and non‐breath‐hold T1‐weighted and T2‐weighted imagings of focal liver lesions were prospectively compared in 120 patients with suspected focal liver lesions imaged at 1.5 T with use of a body phased array multicoil. Breath‐hold images were acquired with T1‐weighted fast low‐angle shot (FLASH) and T2‐weighted turbo spin echo (TSE) sequences, and non‐breath‐hold images were made with conventional T1‐ and T2‐weighted SE sequences. Qualitative image analysis was done by three blinded readers, and quantitative analysis was done. The highest signal‐to‐noise ratios were obtained with breath‐hold T1‐weighted FLASH sequence. The signal‐to‐noise ratios of breath‐hold T2‐weighted TSE sequence were slightly inferior to those of non‐breath‐hold SE sequence. Both T1‐weighted and T2‐weighted breath‐hold sequences had less image artifact. Overall image quality of breath‐hold sequences was better than that of non‐breath‐hold sequences for both T1‐ and T2‐weighted sequences (P < .01). The tissue contrast of T1‐weighted FLASH sequence was superior to that of SE sequence (P < .01). On T2‐weighted imaging, tissue contrast of solid lesions was better on conventional SE sequence than that on breath‐hold TSE sequence (P < .01). Respiratory ghost artifact was less prominent on T1‐weighted FLASH sequence, although this artifact was occasionally seen on breath‐hold T2‐weighted TSE sequence. In a state‐of‐art MR unit with use of a phased array multicoil, conventional T1‐weighted can be replaced by breath‐hold sequences. On T2‐weighted imaging, because solid tumor‐liver contrast on breath‐hold TSE imaging is inferior to that on non‐breath‐hold SE image, breath‐hold imaging may not replace conventional non‐breath‐hold T2‐weighted SE sequence.
Motion artifact in T2‐weighted fast spin‐echo images of the liver: Effect on image contrast and reduction of artifact using respiratory triggering in normal volunteers
Authors: Choe Kyuran A. , Smith Robert C. , Wilkens Ken , Constable R. Todd 
Published: March 2007

AbstractThe purpose of our study was to evaluate the effect of respiratory motion on the image contrast of T2‐weighted fast spin‐echo (FSE) images of the liver as well as the reduction of motion artifact using respiratory triggering of the data acquisition. We imaged the livers of 10 healthy volunteers using a fast spin‐echo T2‐weighted sequence. Images were obtained both without and with patient triggering. Triggered images were acquired in a segmented fashion during multiple sequential breath‐holds using an echo train of 8 or 16, both with and without flow compensation (gradient moment nulling). Ratios of signal difference to noise (SD/N) of the liver and gallbladder as well as the liver and spleen were compared for all sequences. All of the triggered images showed statistically significant improvement of SD/N for the liver and gallbladder as well as for the liver and spleen when compared with the nontriggered images. Triggered images obtained with an echo train length of 8 and, with flow compensation, showed the highest SD/N ratios. In one volunteer whose liver contained multiple small cysts, the triggered images showed improved visualization of individual cysts and identified a larger number of cysts. Respiratory motion causes a significant loss of contrast on T2‐weighted fast spin‐echo images of the liver. This can be reduced by using a segmented data acquisition triggered by the respiratory cycle obtained during sequential breath‐holds.
Three‐dimensional coronary angiography of the perfused rat heart
Authors: Roder Fridtjof , Hiller Karl‐Heinz , Henz Peter , Kienlin Markus V. , Bauer Wolfgang R. , Ertl Georg , Haase Axel 
Published: March 2007

AbstractThe purpose of this work was to visualize the whole three‐dimensional coronary artery tree of the perfused beating rat heart using three‐dimensional MRI. The spatial resolution amounts to 140 μm. Also, vessels having smaller diameters could be detected. Different strategies for the visualization of the three‐dimensional coronary angiograms including maximum intensity projection, data thresholding, and segmentation, were shown. The coronary artery tree was best visualized by hysteresis threshold segmentation and subsequent surface reconstruction.
Phase‐derivative analysis in MR angiography: Reduced Venc dependency and improved vessel wall detection in laminar and disturbed flow
Authors: Hoogeveen Romhild M. , Bakker Chris J. G. , Viergever Max A. 
Published: March 2007

AbstractA problem of current MRA techniques is the inability to accurately depict the vascular anatomy, particularly in areas of disturbed flow. Various reasons, such as intravoxel phase dispersion, saturation, temporal variations, and maximum intensity projection (MIP) nonlinearity, cause a wrong delineation of vessel boundaries. A phase contrast (PC)‐based postprocessing operation, the phase derivative (PhD), is introduced to detect phase fluctuations indicating flow. Two‐dimensional and three‐dimensional angiographic reconstruction algorithms are presented. Mathematical formulas are derived to predict the effect of sampling to flow profiles and the effect on the PhD of these profiles. Numerical, phantom, and preliminary in vivo experiments demonstrate that PhD images do not suffer from phase wraps and allow a velocity dynamic range extension only limited by a differential phase change. It is also shown that PhD MIPs produce higher signal‐to‐noise ratios than conventional PC angiograms and give a better impression of the anatomy of (stenotic) vessels and of their diameters for both laminar and disturbed flow.
Inadequacy of motion correction algorithms in functional MRI: Role of susceptibility‐induced artifacts
Authors: Wu Dee H. , Lewin Jonathan S. , Duerk Jeffrey L. 
Published: March 2007

AbstractFunctional MR (fMR) has been useful in providing insight into the localization and detection of neural cortical activity. However, patient head motion is inevitable over the course of most fMR experiments. Although methods to align the control and activation fMR images may correct for some of this motional error, they will be incomplete in correcting for those that depend on spatial orientation. MR signal amplitude of structures that lie along air‐tissue interfaces, for example, are sensitive to susceptibility errors introduced by their reorientation with respect to the main magnetic field. This analysis, using phantoms, cadaver brain, and volunteers, has shown that this reorientation between control and activation images can create regions of “false activation” that increase in area with rotation. Anatomic regions that are expected to be most affected by these susceptibility‐induced magnetic field homogeneity variations are those adjacent to bone or air, such as the mesial and inferior temporal lobes and the inferior and anterior frontal lobes. Interpretation of “activation” in these areas on fMR studies must be performed with careful consideration of this important source of error.
Localized echo‐volume imaging methods for functional MRI
Authors: Yang Yihong , Mattay Venkata S. , Weinberger Daniel R. , Frank Joseph A. , Duyn Jeff H. 
Published: March 2007

AbstractTo perform true three‐dimensional activation experiments in the human brain, dedicated localized echo‐volume imaging (L‐EVI) methods were developed. Three‐dimensional acquisition allows generation of activation maps with minimal vascular enhancement related to inflow effects. The rapid acquisition of the L‐EVI (∼100 msec) reduces signal instabilities caused by motion, facilitating the detection of the small intensity changes expected with brain activation. Single‐shot L‐EVI was performed on normal volunteers at 1.5 T, imaging a three‐dimensional predefined volume (240 × 45 × 45 mm3) in the superior portion of the brain with a spatial resolution of 3.75 × 5 × 5 mm3. Increased brain coverage was achieved with a multi‐volume imaging (three‐shot) version, which simultaneously achieved effective suppression of signals from cerebrospinal fluid. In addition, both asymmetric spin‐echo (ASE) and spin‐echo (SE) versions of the technique were used to detect blood oxygenation level dependent (BOLD) signal changes in the motor cortex with a finger‐tapping paradigm. Images obtained by the L‐EVI sequence were qualitatively comparable to standard multislice two‐dimensional echo‐planar images. Both ASE and SE functional MRI (fMRI) experiments showed consistent activation in the contralateral primary sensorimotor cortex. Furthermore, significant differences in location and magnitude of activation was observed between the two methods, confirming theoretical predictions.
Implementation of a reduced field‐of‐view method for dynamic MR imaging using navigator echoes
Authors: Kyriakos Walid E. , Panych Lawrence P. , Zientara Gary P. , Jolesz Ferenc A. 
Published: March 2007

AbstractA new technique was designed and implemented that increases imaging speed in dynamic imaging in which change is restricted to a fraction of the full field of view (FOV). The technique is an enhancement of a reduced FOV method first reported by Hu and Parrish. This enhancement extends the use of the Hu and Parrish method to cases in which there is cyclic motion throughout the entire FOV that normally would be aliased into the reduced FOV. This method requires the initial acquisition of a number of baseline k‐space data sets to characterize the background physiological motion during imaging. Projection navigator echoes along both the phase‐ and the frequency‐encoded directions are acquired and used to correct for motion outside the reduced FOV. Automatic placement or repositioning of the updated fraction of the FOV using navigators also is investigated. With this method, when using a 32‐echo rapid acquisition with relaxation enhancement (RARE) sequence, single‐shot updates of T2‐weighted, 128 × 128 pixel images are obtained, yielding a fourfold increase in temporal resolution compared to full k‐space update methods.
In vivo comparison of MR phase distribution and 1/T2* with morphologic parameters in the distal radius
Authors: Allein Sophie , Majumdar Sharmila , De Bisschop Elke , Newitt David C. , Luypaert Rob , Eisendrath Henri 
Published: March 2007

AbstractA new approach based on the calculation of the phase variance in a region of interest on the phase images of a simple gradient echo sequence, was used to assess the properties of trabecular bone in the distal radius. The phase variance reflects the distribution of field inhomogeneities due to the difference in magnetic susceptibility between bone and marrow in a way similar to T2*. However, the phase variance monitors the intervoxular differences, whereas T2* studies the intravoxular inhomogeneities. In this study of the radius of seven volunteers, both techniques were compared with parameters characterizing trabecular bone structure derived from high resolution MR images. Parameters such as the apparent bone area fraction, trabecular number, thickness and spacing, and box‐counting fractal dimension were determined.
Peripheral nerve stimulation in a whole‐body echo‐planar imaging system
Authors: Ehrhardt James C. , Lin Chin‐S , Magnotta Vincent A. , Fisher David J. , Yuh William T. C. 
Published: March 2007

AbstractEcho‐planar techniques in MRI use a rapidly oscillating frequency‐encoding gradient with the potential to produce peripheral nerve stimulation. To evaluate the incidence, type, and location of stimulation in a commercial whole‐body scanner, we studied two groups: (a) 173 consecutive individuals scanned by echo‐planar imaging for other purposes and (b) seven subjects who were scanned with an extensive set of 36 echo‐planar sequences (with prompting after each scan to report any peripheral nerve stimulation) to test the effects of various parameters. Although only 5% of group A reported symptoms of peripheral nerve stimulation, all in group B experienced some type of stimulation, dependent primarily on direction of the oscillating gradient and location of the body within the gradient coil. Maximum stimulation typically occurred 30 to 40 cm from isocenter in the region of maximum dB/dt. Generally, y gradients produced truncal stimulation, and x gradients produced stimulation in the head. When hands were clasped over the abdomen, a tingling in the hands occasionally was felt. Patients should be instructed to keep their hands apart.
Multi‐echo 31P spectroscopic imaging of ATP: A scan time reduction strategy
Authors: Chao Hui , Bowers John L. , Holtzman David , Mulkern Robert V. 
Published: March 2007

AbstractSpectroscopic imaging of 31P metabolites and adenosine triphosphate (ATP) in particular with multiple spin echoes may prove useful for reducing data acquisition times. The usual T2 decay processes that degrade multi‐echo spectroscopic imaging methods, however, are further compounded by J‐coupling modulations in the case of ATP. We determine how these modulations affect multi‐echo spectroscopic imaging k‐space data and produce systematic spatial misregistrations of the ATP resonances. The specific J‐coupling modulations of ATP are determined to identify echo‐spacing effects in multi‐echo spectroscopic imaging of ATP and to determine appropriate post‐processing correction schemes to address the spatial misregistration problem. An in vivo demonstration of the technique that offers a threefold reduction in scan time compared to conventional SI methods is provided and compared with the conventional SI approach.
A programmable eddy‐current compensation system for MRI and localized spectroscopy
Authors: Fry Martin E. , Pittard Simon , Summers Ian R. , Vennart William , Goldie Frederick T. D. 
Published: March 2007

AbstractA programmable preemphasis system has been developed for eddy‐current compensation in gradient sets with or without active screening. Preemphasis parameters are nonvolatile but can be changed rapidly when working with interchangeable gradient sets. The design allows easy retrofit to existing systems. A method for setting the preemphasis is presented, together with specimen results.
Ovarian fibromas and cystadenofibromas: MRI features of the fibrous component
Authors: Outwater Eric K. , Siegelman Evan S. , Talerman Alexander , Dunton Charles 
Published: March 2007

AbstractOvarian fibromas and cystadenofibromas are neoplasms that share a similar distinctive tissue component of dense fibrous tissue. We sought to describe the MRI features of these neoplasms and to determine if the fibrous component shows distinctive characteristics. Fourteen patients in whom MR images performed with multicoil and fast‐spin‐echo images and who subsequently underwent surgery for resection of ovarian fibromas or cystadenofibromas were identified from two institutions. Five patients had ovarian fibromas, and nine patients had fourteen cystadenofibromas. 1.5‐T MR studies used T1‐weighted spin echo and multiplanar T2‐weighted fast‐spin‐echo images, with fat saturation gadoliniumenhanced fast multiplanar gradient‐echo images in seven patients. Studies were reviewed for findings of low (≈ skeletal muscle) signal intensity solid components on T2‐weighted images, characteristics of gadolinium enhancement, and associated endometrial findings. Images were obtained ex vivo from three adnexal surgical specimens with an 8‐cm field of view and correlated with histology. All five of the fibromas showed predominantly very low signal intensity, similar to skeletal muscle, on T2‐weighted images. Two of five fibromas were in patients with endometrial polyps and increased amounts of fluid in the pelvis. Thirteen cystadenofibromas were multicystic masses with bands of very low signal intensity ranging from 2 to 20 mm in the wall of the mass, and one was predominantly solid fibrous tissue. Pathologic correlation with specimen images showed that the low signal intensity material was the subepithelial fibrous component of the Cystadenofibromas. Fibrous components of ovarian fibromas and cystadenofibromas are demonstrable by MR as solid components representing fibrous tissue of very low signal intensity on T2‐weighted images.