bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vascular space occupancy‐dependent functional MRI by tissue suppression
Authors: Wu Changwei W. , Chuang Kai‐Hsiang , Wai Yau‐Yau , Wan Yung‐Liang , Chen Jyh‐Horng , Liu Ho‐Ling 
Published: June 2008

AbstractPurposeTo measure the cerebral blood volume (CBV) dynamics during neural activation, a novel technique named vascular space occupancy (VASO)‐based functional MRI (fMRI) was recently introduced for noninvasive CBV detection. However, its application is limited because of its low contrast‐to‐noise ratio (CNR) due to small signal change from the inverted blood.Materials and MethodsIn this study a new approach—VASO with tissue suppression (VAST)—is proposed to enhance CNR. This technique is compared with VASO and blood oxygenation level‐dependent (BOLD) fMRI in block‐design and event‐related visual experiments.ResultsBased on acquired T1 maps, 75.3% of the activated pixels detected by VAST are located in the cortical gray matter. Temporal characteristics of functional responses obtained by VAST were consistent with that of VASO. Although the baseline signal was decreased by the tissue suppression, the CNR of VAST was about 43% higher than VASO.ConclusionWith the improved sensitivity, VAST fMRI provides a useful alternative for mapping the spatial/temporal features of regional CBV changes during brain activation. However, the technical imperfectness of VAST, such as the nonideal inversion efficiency and physiological contaminations, limits its application to precise CBV quantification. J. Magn. Reson. Imaging 2008;28:219–226. © 2008 Wiley‐Liss, Inc.
Detection of lymph node metastasis in cervical and uterine cancers by diffusion‐weighted magnetic resonance imaging at 3T
Authors: Lin Gigin , Ho Kung‐Chu , Wang Jiun‐Jie , Ng Koon‐Kwan , Wai Yau‐Yau , Chen Yen‐Ting , Chang Chee‐Jen , Ng Shu‐Hang , Lai Chyong‐Huey , Yen Tzu‐Chen 
Published: June 2008

AbstractPurposeTo evaluate diffusion‐weighted imaging (DWI) for detection of pelvic lymph node metastasis in patients with cervical and uterine cancers.Materials and MethodsFifty patients scheduled for pelvic lymph node dissection were enrolled for 3T magnetic resonance imaging (MRI) using a single‐shot echo‐planar DWI technique, body‐phased array coil, b = 0, 1000 s/mm2. We measured short/long‐axis diameters, mean apparent diffusion coefficient (ADC) values of all identifiable nodes, relative ADC values between tumors and nodes, and utilized their cutoff values to validate the diagnostic accuracy internally. Histopathologic results served as the reference standard.ResultsThe relative ADC values between tumor and nodes were significantly lower in metastatic than in benign nodes (0.06 vs. 0.21 × 10−3 mm2/s, P < 0.001; cutoff value 0.10 × 10−3 mm2/s). Compared to conventional MRI, the method combining size and relative ADC values resulted in better sensitivity (25% vs. 83%) and similar specificity (98% vs. 99%). The smallest metastatic lymph node detected by this method measured 5 mm on its short axis.ConclusionThe combination of size and relative ADC values was useful in detecting pelvic lymph node metastasis in patients with cervical and uterine cancers. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
MRI and contrast‐enhanced ultrasound monitoring of prostate microwave focal thermal therapy: An in vivo canine study
Authors: Cheng Hai‐Ling Margaret , Haider Masoom A. , Dill‐Macky Marcus J. , Sweet Joan M. , Trachtenberg John , Gertner Mark R. 
Published: June 2008

AbstractPurposeTo compare the value of diffusion‐weighted MRI (DWI), dynamic contrast‐enhanced (DCE) MRI, and microbubble contrast‐enhanced ultrasound (CEUS) for assessment of the thermal lesion created by interstitial microwave heating of the normal canine prostate.Materials and MethodsA microwave antenna was inserted into each lobe of the prostate in seven dogs to induce coagulation necrosis. Immediately after therapy the lesion was assessed using CEUS, DCE‐MRI, and DWI. The prostates were excised, photographed, and prepared for hematoxylin and eosin staining. Results from posttreatment MRI and ultrasound were compared to histology.ResultsThe apparent diffusion coefficient (ADC) was slightly lowered within the thermal lesion but was drastically reduced in a ring‐like region that corresponds to a grossly appearing red thermal damage zone immediately peripheral to the central coagulum. Both DCE‐MRI and CEUS delineated a smaller area of vascular damage, for which the borders lie within the red zone.ConclusionThe red zone encompasses a range of vascular responses, including hyperemia and hemostasis, and is known to progress to necrosis and tissue nonviability. DWI clearly depicts this zone as a region of sharply reduced ADC, and may be better than contrast‐enhanced imaging for accurate assessment of the eventual full extent of thermal damage. J. Magn. Reson. Imaging 2008;28:136–143. © 2008 Wiley‐Liss, Inc.
T2 and T quantification using optimal B1 image reconstruction for multicoil arrays
Authors: Graves Martin J. , Emmens Daniel , Lejay Hubert , Hariharan Hari , Polzin Jason , Lomas David J. 
Published: June 2008

AbstractPurposeTo investigate the accuracy of low signal‐to‐noise ratio (SNR) T2 and T measurements using array coils and optimal B1 image reconstruction (OBR) compared to the standard root sum of squares (RSS) reconstruction.Materials and MethodsCalibrated gels were used for the in vitro study of T2. T2 and T measurements were obtained from a volunteer's knee and liver, respectively. T2 and T measurements were performed using multiecho spin echo and multiecho gradient echo sequences, respectively. SNR was deliberately kept low. The same raw data were used for both reconstructions. For the in vivo studies the effect of signal averaging was also investigated.ResultsThe optimal reconstructions demonstrated a lower mean background noise level than RSS. In vitro, the T2 measurements made with OBR images agreed better with a reference high SNR measurement than measurements made from RSS images; the RSS image results overestimated the T2. In vivo, increasing the signal averages decreased the difference between the measurements obtained using the OBR and RSS methods, with RSS resulting in longer relaxation times.ConclusionThis work demonstrates improvements to the accuracy of T2 and T measurements obtained when OBR is used compared to RSS, particularly in the case of low SNR. J. Magn. Reson. Imaging 2008;28:278–281. © 2008 Wiley‐Liss, Inc.
MRA of intracranial aneurysms embolized with platinum coils: A vascular phantom study at 1.5T and 3T
Authors: Kakeda Shingo , Korogi Yukunori , Hiai Yasuhiro , Sato Toru , Ohnari Norihiro , Moriya Junji , Kamada Koji 
Published: June 2008

AbstractPurposeTo analyze the influence of matrix and echo time (TE) of three‐dimensional time‐of‐flight (3D TOF) magnetic resonance angiography (MRA) on the depiction of residual flow in aneurysms embolized with platinum coils at 1.5T and 3T.Materials and MethodsA simulated intracranial aneurysm of the vascular phantom was loosely packed to maintain the patency of some residual aneurysmal lumen with platinum coils and connected to an electromagnetic flow pump with pulsatile flow. MRAs were obtained altering the matrix and TE of 3D TOF sequences at 1.5T and 3T.ResultsThe increased spatial resolution and the shorter TE offered better image quality at 3T. For the depiction of an aneurysm remnant, the high‐spatial‐resolution 3T MRA (matrix size of 384 × 224 and 512 × 256) with a short TE of ≤3.3 msec were superior to the 1.5T MRA obtained with any sequences.Conclusion3T MRA is superior to 1.5T MRA for the assessment of aneurysms embolized with platinum coils; the combination of the 512 × 256 matrix and short TE (3.3 msec or less) seems feasible at 3T. J. Magn. Reson. Imaging 2008;28:13–20. © 2008 Wiley‐Liss, Inc.
Conspicuity of zones of ablation after radiofrequency ablation in porcine livers: Comparison of an extracellular and an SPIO contrast agent
Authors: Bangard Christopher , Stippel Dirk L. , Berg Frank , Kasper Hans U. , Hellmich Martin , Fischer Jürgen H. , Hölscher Arnulf , Lackner Klaus , Gossmann Axel 
Published: June 2008

AbstractPurposeTo compare conspicuity of zones of ablation on nonenhanced, gadopentetate dimeglumine‐(Gd‐DTPA) and ferucarbotran‐(SPIO)‐enhanced magnetic resonance (MR) images.Materials and MethodsIn all, 33 radiofrequency ablations (RFA) were performed in 17 healthy porcine livers at 1.5T MR imaging 1 day and 2 and 4 weeks after RFA: T2‐weighted (w) ultra turbo spin echo (UTSE), proton density (PD)‐w UTSE, T1‐w gradient echo (GRE) pre‐ and 5 minutes postcontrast administration, dynamic T1‐w GRE during Gd‐DTPA (Magnevist) or SPIO (Resovist) administration, T2‐w UTSE, and PD‐w UTSE sequences 10 minutes after SPIO administration. Regions of interest (ROIs) for contrast‐to‐noise ratio (CNR) and signal‐to‐noise ratio (SNR) were drawn in consensus by two radiologists.ResultsPD‐w SPIO‐enhanced images (23.5 ± 5.5) showed higher liver‐to‐lesion CNR than T1‐w GRE Gd‐DTPA‐enhanced images (13.5 ± 6.1) 1 day after RFA (P ≤ 0.05). At all other timepoints, liver‐to‐lesion CNR of PD‐w and T2‐w SPIO‐enhanced images did not differ significantly from T1‐w GRE Gd‐DTPA‐enhanced images (P ≥ 0.05). Nonenhanced T2‐w images revealed lower liver‐to‐lesion CNR (7.0 ± 7.5/6.5 ± 5.9/6.8 ± 5.0, 1 day/2 weeks/4 weeks, respectively) than T2‐w SPIO‐enhanced (17.4 ± 4.8/15.3 ± 4.5/14.2 ± 5.7), PD‐w SPIO‐enhanced (23.5 ± 5.5/16.9 ± 3.6, 1 day/2 weeks), and T1‐w Gd‐DTPA‐enhanced (15.3 ± 3.6/12.7 ± 3.5, 2/4 weeks) images (P ≤ 0.05). Liver‐to‐lesion CNR of SPIO‐enhanced dynamic T1‐w GRE images after 30, 80, 150, and 240 seconds did not change significantly over time (P ≥ 0.05).ConclusionOne day after RFA lesion conspicuity on PD‐w ferucarbotran‐enhanced images is better than on T1‐w GRE Gd‐DTPA‐enhanced images. At all other timepoints, ferucarbotran is not superior to gadolinium. Ferucarbotran‐ and gadolinium‐enhanced images improve lesion conspicuity compared with nonenhanced T2‐w images at all timepoints. J. Magn. Reson. Imaging 2008;28:263–270. © 2008 Wiley‐Liss, Inc.
One‐stop measurement of iron deposition in the anterior pituitary, liver, and heart in thalassemia patients
Authors: Lam Wynnie W.M. , Au W.Y. , Chu Winnie C.W. , Tam S. , Ha S.Y. , Pennell D.J. 
Published: June 2008

AbstractPurposeTo assess the feasibility of one‐stop evaluation of iron load of myocardium, liver, and anterior pituitary gland in thalassemia patients.Materials and MethodsFifty thalassemia major patients underwent a breath‐hold magnetic resonance imaging (MRI) sequence for assessment of T2* for liver and myocardium, a short axis cine trueFISP sequence covering base to apex to assess the ejection fraction of left ventricle, and a turbo spin echo T2‐weighted sequence for the anterior pituitary gland. The MRI parameters were correlated with serum growth hormone, insulin growth factor‐1 (IGF‐1), insulin growth factor binding protein‐3 (IGFBP‐3), and endocrine failure.ResultsFerritin was found to be associated with T2* liver (P < 0.005), T2SI (signal intensity) pituitary (P = 0.001), and T2 pituitary/fat (P = 0.001), but not with T2* heart. There was significant correlation of T2SI pituitary with IGF‐1 and IGFBP‐3. T2* liver (P < 0.001), T2* heart (P < 0.001), pituitary SI (P < 0.001) and pituitary/fat SI (P = 0.002) were also found to be significantly correlated with a history of hypogonadism. T2* heart was also found to be significantly correlated with IGF‐1.ConclusionA quick MRI protocol for assessment of T2* liver, T2* heart, and T2SI pituitary is technically feasible. This might form an objective basis to monitor the response to different organs to chelation therapy. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
Production of reduced calorie structured lipid by acidolysis of tripalmitin with capric acid: optimisation by response surface methodology
Authors: Bektaş Inan , Yucel Sevil , Ustun Guldem , Aksoy H Ayse 
Published: June 2008

AbstractBACKGROUND: Structured lipids (SLs) containing medium‐chain fatty acids (C8:0–C12:0) in the 1‐ and 3‐positions and long‐chain fatty acids in the 2‐position of triacylglycerols have interesting applications as reduced calorie fats. The aim of this study was to produce an SL by inserting capric acid (CA, C8:0) into tripalmitin (TP) and to optimise the reaction conditions by response surface methodology (RSM) with a three‐level, three‐factor face‐centred cubic design.RESULTS: Lipozyme TL IM from Thermomyces lanuginosa was used for the acidolysis of TP with CA in n‐hexane. The effects of three independent parameters, namely substrate molar ratio, enzyme amount and reaction time, on CA incorporation into TP were optimised. The range of each parameter was selected as follows: substrate molar ratio (CA/TP), 4–8; enzyme amount, 9–15 wt% of total substrate; reaction time, 6–10 h. Optimal conditions were determined to be a CA/TP molar ratio of 6.5, an enzyme amount of 11.6 wt% and a reaction time of 8.9 h. Experiments conducted under these optimised conditions yielded an SL containing 35.7 wt% (44.9 mol%) CA. A second‐order polynomial model was obtained for CA incorporation.CONCLUSION: The possibility of enriching CA in TP by enzymatic acidolysis has been established. The SL containing 44.9 mol% CA produced under optimal conditions may be considered a reduced calorie fat. Copyright © 2008 Society of Chemical Industry
Rivastigmine versus placebo in hyperhomocysteinemic Parkinson's disease dementia patients
Authors: Barone Paolo , Burn David J. , van Laar Teus , Hsu Chuanchieh , Poewe Werner , Lane Roger M. 
Published: June 2008

AbstractThe effects of rivastigmine versus placebo in Parkinson's disease dementia (PDD) patients with elevated or normal/low plasma homocysteine were determined. In this prospective analysis of a 24‐week, randomly assigned, placebo‐controlled study of rivastigmine in PDD, subpopulations comprised patients with plasma homocysteine ≥14 μmol/L (elevated) or <14 μmol/L (normal/low). Coprimary outcomes were the Alzheimer's Disease Assessment Scale–cognitive subscale (ADAS‐cog) and Alzheimer Disease Cooperative Society–Clinical Global Impression of Change (ADCS‐CGIC). Secondary outcomes included additional measures of cognition, including attention and executive function, daily function, and neuropsychiatric symptoms. Adverse events (AEs) were monitored. In total, 342 of 541 patients provided samples for analysis, from which 72% had elevated plasma homocysteine. Hyperhomocysteinemic patients showed treatment differences (rivastigmine vs. placebo) of 4.0 on ADAS‐cog and 0.7 on ADCS‐CGIC (both P < 0.01), and significant treatment differences on secondary outcomes. Rivastigmine‐ and placebo‐treated hyperhomocysteinemic patients (16.5% and 14.6%) discontinued the study because of AEs. Patients with normal/low homocysteine showed no treatment differences on primary or secondary outcomes (1.4 on the ADAS‐cog and 0.1 on ADCS‐CGIC, both P = ns); 16.7% and 10.3% rivastigmine‐ and placebo‐treated patients discontinued because of AEs. Elevated homocysteine was associated with greater rivastigmine treatment differences than normal/low homocysteine. © 2008 Movement Disorder Society
Multiresolution field map estimation using golden section search for water‐fat separation
Authors: Lu Wenmiao , Hargreaves Brian A. 
Published: June 2008

AbstractMany diagnostic MRI sequences demand reliable and uniform fat suppression. Multipoint water–fat separation methods, which are based on chemical‐shift induced phase differences, have shown great success in the presence of field inhomogeneities. This work presents a computationally efficient and robust field map estimation method. The method begins with subsampling image data into a multiresolution image pyramidal structure, and then utilizes a golden section search to directly locate possible field map values at the coarsest level of the pyramidal structure. The field map estimate is refined and propagated to increasingly finer resolutions in an efficient manner until the full‐resolution field map is obtained for final water‐fat separation. The proposed method is validated with multiecho sequences where long echo‐spacings normally impose great challenges on reliable field map estimation. Magn Reson Med 60:236–244, 2008. © 2008 Wiley‐Liss, Inc.
Water–fat separation with bipolar multiecho sequences
Authors: Lu Wenmiao , Yu Huanzhou , Shimakawa Ann , Alley Marcus , Reeder Scott B. , Hargreaves Brian A. 
Published: June 2008

AbstractMultiecho sequences provide an efficient means to acquire multiple echoes in a single repetition, which has found applications in spectroscopy, relaxometry, and water–fat separation. By replacing the fly‐back gradients in unipolar multiecho sequences with alternating readout gradients, bipolar multiecho sequences greatly reduce both echo‐spacing and repetition interval. This offers many attractive advantages, such as shorter scan times, higher SNR efficiency, more robust field map estimation, reduced motion‐induced artifacts, and less sensitivity to short T. However, the alternating readout gradients cause several technical problems, including delay effects and image misregistrations, which prevent direct application of existing water–fat separation methods. This work presents solutions to address these problems, including a post‐processing method that shifts k‐space data to correct k‐space echo misalignment, an image warping method that utilizes a low‐resolution field map to remove field‐inhomogeneity‐induced misregistration, and a k‐space water–fat separation method that eliminates chemical‐shift‐induced artifacts in separated water and fat images. In addition, a noise amplification factor, which characterizes the noise present in separated images, is proposed to serve as a useful guideline for choosing imaging parameters or regularization parameters in the case of ill‐conditioned separation. The proposed methods are validated both in phantoms and in vivo to enable reliable and SNR efficient water–fat separation with bipolar multiecho sequences. Magn Reson Med 60:198–209, 2008. © 2008 Wiley‐Liss, Inc.
Concomitant field terms for asymmetric gradient coils: Consequences for diffusion, flow, and echo‐planar imaging
Authors: Meier C. , Zwanger M. , Feiweier T. , Porter D. 
Published: June 2008

AbstractAs a consequence of the Maxwell equations, linear field gradients are accompanied by additional spatially dependent field components. A description of the Maxwell field terms is presented which explicitly takes into account the asymmetry of the gradient coil. It is shown both theoretically and experimentally that, in contrast to symmetric coils, an asymmetric coil generates concomitant field terms of zeroth and first order in space. Artifacts induced by concomitant fields can be much more pronounced for asymmetric coil designs than for symmetric ones. For the strong gradient amplitudes available on modern MR systems the effect of these concomitant magnetic fields on the evolution of magnetization has to be taken into consideration in a variety of NMR acquisition techniques. The formalism is used experimentally to compensate for artifacts observed in three different imaging methods: an image shift in standard echo planar imaging (EPI), an echo shift in diffusion‐weighted EPI, and a phase shift in a flow quantification technique based on phase contrast images. Magn Reson Med 60:128–134, 2008. © 2008 Wiley‐Liss, Inc.
Four‐dimensional MR microscopy of the mouse heart using radial acquisition and liposomal gadolinium contrast agent
Authors: Bucholz Elizabeth , Ghaghada Ketan , Qi Yi , Mukundan Srinivasan , Johnson G. Allan 
Published: June 2008

AbstractMagnetic resonance microscopy (MRM) has become an important tool for small animal cardiac imaging. In relation to competing technologies (microCT and ultrasound), MR is limited by spatial resolution, temporal resolution, and acquisition time. All three of these limitations have been addressed by developing a four‐dimensional (4D) (3D plus time) radial acquisition (RA) sequence. The signal‐to‐noise ratio (SNR) has been optimized by minimizing the echo time (TE) (300 us). The temporal resolution and throughput have been improved by center‐out trajectories resulting in repetition time (TR) <2.5 ms. The contrast has been enhanced through the use of a liposomal blood pool agent that reduces the T1 of the blood to <400 ms. We have developed protocols for three specific applications: 1) high‐throughput with spatial resolution of 87 × 87 × 352 um3 (voxel volume = 2.7 nL) and acquisition time of 16 min; 2) high‐temporal resolution with spatial resolution of 87 × 87 × 352 um3 (voxel volume = 2.7 nL) and temporal resolution at 4.8 ms and acquisition time of 32 minutes; and 3) high‐resolution isotropic imaging at 87 × 87 × 87 um3 (voxel volume = 0.68 nL) and acquisition time of 31 min. The 4D image arrays allow direct measure of cardiac functional parameters dependent on chamber volumes, e.g., ejection fraction (EF), end diastolic volume (EDV), and end systolic volume (ESV). Magn Reson Med 60:111–118, 2008. © 2008 Wiley‐Liss, Inc.
In vitro investigation of poor cerebrospinal fluid suppression on fluid‐attenuated inversion recovery images in the presence of a gadolinium‐based contrast agent
Authors: Bonzano L. , Roccatagliata L. , Levrero F. , Mancardi G.L. , Sardanelli F. 
Published: June 2008

AbstractCerebrospinal fluid (CSF) enhancement on fluid‐attenuated inversion recovery (FLAIR) images obtained post‐gadolinium (Gd)‐based agent injection is described in stroke and multiple sclerosis. Blood brain barrier (BBB) disruption with contrast agent extravasation into CSF shortens T1 relaxation times, reducing fluid suppression. Reduced fluid suppression on FLAIR images was investigated in vitro in the presence of escalating gadopentetate dimeglumine (Gd‐DTPA) concentrations mixed with artificial CSF. Low Gd‐DTPA concentrations impair fluid suppression of FLAIR imaging in association with progressively reduced T1 values. At higher concentrations, the prevalent T2 shortening effect can explain signal intensity (SI) reduction. Post‐Gd FLAIR may be useful in detecting subtle BBB leakage. Magn Reson Med 60:220–223, 2008. © 2008 Wiley‐Liss, Inc.
Acquisition‐weighted stack of spirals for fast high‐resolution three‐dimensional ultra‐short echo time MR imaging
Authors: Qian Yongxian , Boada Fernando E. 
Published: June 2008

AbstractUltra‐short echo time (UTE) MRI requires both short excitation (∼0.5 ms) and short acquisition delay (<0.2 ms) to minimize T2‐induced signal decay. These requirements currently lead to low acquisition efficiency when high resolution (<1 mm) is pursued. A novel pulse sequence, acquisition‐weighted stack of spirals (AWSOS), is proposed here to acquire high‐resolution three‐dimensional (3D) UTE images with short scan time (∼72 s). The AWSOS sequence uses variable‐duration slice encoding to minimize T2 decay, separates slice thickness from in‐plane resolution to reduce the number of slice encodings, and uses spiral trajectories to accelerate in‐plane data collections. T2‐ and off‐resonance induced slice widening and image blurring were calculated from 1.5 to 7 Tesla (T) through point spread function. Computer simulations were performed to optimize spiral interleaves and readout times. Phantom scans and in vivo experiments on human heads were implemented on a clinical 1.5T scanner (Gmax = 40 mT/m, Smax = 150 T/m/s). Accounting for the limits on B1 maximum, specific absorption rate (SAR), and the lowered amplitude of slab‐select gradient, a sinc radiofrequency (RF) pulse of 0.8ms duration and 1.5 cycles was found to produce a flat slab profile. High in‐plane resolution (0.86 mm) images were obtained for the human head using echo time (TE) = 0.608 ms and total shots = 720 (30 slice‐encodings × 24 spirals). Compared with long‐TE (10 ms) images, the ultrashort‐TE AWSOS images provided clear visualization of short‐T2 tissues such as the nose cartilage, the eye optic nerve, and the brain meninges and parenchyma. Magn Reson Med 60:135–145, 2008. © 2008 Wiley‐Liss, Inc.