bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization and validation of methods for mapping of the radiofrequency transmit field at 3T
Authors: Lutti Antoine , Hutton Chloe , Finsterbusch Jürgen , Helms Gunther , Weiskopf Nikolaus 
Published: May 2010

AbstractMRI techniques such as quantitative imaging and parallel transmit require precise knowledge of the radio‐frequency transmit field (B). Three published methods were optimized for robust B mapping at 3T in the human brain: three‐dimensional (3D) actual flip angle imaging (AFI), 3D echo‐planar imaging (EPI), and two‐dimensional (2D) stimulated echo acquisition mode (STEAM). We performed a comprehensive comparison of the methods, focusing on artifacts, reproducibility, and accuracy compared to a reference 2D double angle method. For the 3D AFI method, the addition of flow‐compensated gradients for diffusion damping reduced the level of physiological artifacts and improved spoiling of transverse coherences. Correction of susceptibility‐induced artifacts alleviated image distortions and improved the accuracy of the 3D EPI imaging method. For the 2D STEAM method, averaging over multiple acquisitions reduced the impact of physiological noise and a new calibration method enhanced the accuracy of the B maps. After optimization, all methods yielded low noise B maps (below 2 percentage units), of the nominal flip angle value (p.u.) with a systematic bias less than 5 p.u. units. Full brain coverage was obtained in less than 5 min. The 3D AFI method required minimal postprocessing and showed little sensitivity to off‐resonance and physiological effects. The 3D EPI method showed the highest level of reproducibility. The 2D STEAM method was the most time‐efficient technique. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Automated segmentation of myocardial scar in late enhancement MRI using combined intensity and spatial information
Authors: Tao Qian , Milles Julien , Zeppenfeld Katja , Lamb Hildo J. , Bax Jeroen J. , Reiber Johan H.C. , van der Geest Rob J. 
Published: May 2010

AbstractAccurate assessment of the size and distribution of a myocardial infarction (MI) from late gadolinium enhancement (LGE) MRI is of significant prognostic value for postinfarction patients. In this paper, an automatic MI identification method combining both intensity and spatial information is presented in a clear framework of (i) initialization, (ii) false acceptance removal, and (iii) false rejection removal. The method was validated on LGE MR images of 20 chronic postinfarction patients, using manually traced MI contours from two independent observers as reference. Good agreement was observed between automatic and manual MI identification. Validation results showed that the average Dice indices, which describe the percentage of overlap between two regions, were 0.83 ± 0.07 and 0.79 ± 0.08 between the automatic identification and the manual tracing from observer 1 and observer 2, and the errors in estimated infarct percentage were 0.0 ± 1.9% and 3.8 ± 4.7% compared with observer 1 and observer 2. The difference between the automatic method and manual tracing is in the order of interobserver variation. In conclusion, the developed automatic method is accurate and robust in MI delineation, providing an objective tool for quantitative assessment of MI in LGE MR imaging. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Active microcoil tracking in the lungs using a semisolid rubber as signal source
Authors: Alt Stefan , Homagk Ann‐Kathrin , Umathum Reiner , Semmler Wolfhard , Bock Michael 
Published: May 2010

AbstractA new method to localize and track medical devices in air‐filled body cavities is proposed that uses active microcoils with a semisolid filling. In air spaces, e.g., the lung, microcoils require an independent signal source, which should be made of a biocompatible, solid and sterilizable material with a long shelf time. In a measurement of the T1 and T*2 and the relative spin density of several semisolid materials, latex was identified as a suitable material from which a prototype catheter was constructed with a microcoil at its tip. In a dual‐echo tracking pulse sequence, the very short T*2 of the rubber material allowed suppressing the background signal from surrounding tissue with a subtraction technique and additional dephasing gradients. With a roadmapping reconstruction, the microcoil's trajectory could be visualized on a previously acquired reference image set with a tracking rate of up to 60 Hz at a spatial resolution of better than 2mm. In a real‐time tracking implementation, an image update rate of 4 Hz was achieved by combining the tracking with a fast real‐time imaging sequence. Both methods were successfully applied in vivo to track the catheter in the lung of a pig. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Simulation model for contrast agent dynamics in brain perfusion scans
Authors: Bredno Jörg , Olszewski Mark E. , Wintermark Max 
Published: May 2010

AbstractStandardization efforts are currently under way to reduce the heterogeneity of quantitative brain perfusion methods. A brain perfusion simulation model is proposed to generate test data for an unbiased comparison of these methods. This model provides realistic simulated patient data and is independent of and different from any computational method. The flow of contrast agent solute and blood through cerebral vasculature with disease‐specific configurations is simulated. Blood and contrast agent dynamics are modeled as a combination of convection and diffusion in tubular networks. A combination of a cerebral arterial model and a microvascular model provides arterial‐input and time‐concentration curves for a wide range of flow and perfusion statuses. The model is configured to represent an embolic stroke in one middle cerebral artery territory and provides physiologically plausible vascular dispersion operators for major arteries and tissue contrast agent retention functions. These curves are fit to simpler template curves to allow the use of the simulation results in multiple validation studies. A γ‐variate function with fit parameters is proposed as the vascular dispersion operator, and a combination of a boxcar and exponential decay function is proposed as the retention function. Such physiologically plausible operators should be used to create test data that better assess the strengths and the weaknesses of various analysis methods. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Optimization of RF excitation to maximize signal and T2 contrast of tissues with rapid transverse relaxation
Authors: Carl Michael , Bydder Mark , Du Jiang , Takahashi Atsushi , Han Eric 
Published: May 2010

AbstractUltrashort echo time MRI requires specialized pulse sequences to overcome the short T2 of the MR signal encountered in tissues such as ligaments, tendon, or cortical bone. Theoretical work is presented, supported by simulations and experimental data on optimizing the radiofrequency excitation to maximize signal‐to‐noise ratio and contrast‐to‐noise ratio. The theoretical calculations and simulations are based on the classic Bloch equations and lead to a closed form expression for the optimal radiofrequency pulse parameters to maximize the MR signal in the presence of rapid T2 decay. In the steady state, the spoiled gradient recalled echo signal amplitude in response to the radiofrequency excitation pulses is not maximized by the classic Ernst angle but by a more general criterion we call “generalized Ernst angle.” Finally, it is shown that T2 contrast is maximized by flipping the magnetization at the Ernst angle with a radiofrequency pulse duration proportional to the targeted T2. Experimental studies on short T2 phantoms confirm these optimization criteria for both signal‐to‐noise ratio and contrast‐to‐noise ratio. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Simulated MR magnetic field induces steady‐state changes in brain dynamics: Implications for interpretation of functional MR studies
Authors: Marino Andrew A. , Carrubba Simona , Frilot Clifton , Chesson Andrew L. , Gonzalez‐Toledo Eduardo 
Published: May 2010

AbstractWe examined whether a magnetic field comparable to one of the fields produced during MRI induced steady‐state changes in brain electrical activity while the field was applied (called a presence effect to distinguish it from evoked potentials). The electroencephalogram was measured from standard scalp locations in the presence and absence of 100‐200 μT, 60 Hz, and the effect of the field was evaluated by nonlinear (recurrence analysis) and linear techniques; individual subjects served as their own controls. Using recurrence analysis, changes in brain activity lasting 1 sec (the longest interval considered) were found in 21 of 22 subjects (P < 0.05 for each subject). The presence effect was not detected using linear analysis and was reversible, as indicated by a return of brain activity to baseline levels in all subjects within 2 sec of field offset. The possible role of artifacts or systematic errors was ruled out by studies using electrical phantoms and by analyses of electroencephalograms recorded during sham exposure. It is reasonable to expect that actual scanner magnetic fields also produce nonlinear steady‐state perturbations of brain dynamical activity. The effect may influence the picture of brain connectivity inferred in some functional MR studies. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Reactions of young children to the MRI scanner environment
Authors: Malisza Krisztina L. , Martin Toby , Shiloff Deborah , Yu Dickie C. T. 
Published: May 2010

AbstractSeventy children aged 2 to 7 years were exposed to the MRI environment through a series of steps typical of a research study. Their willingness to proceed through the process was used to estimate the prevalence of fear. Thirty‐seven children (53%; 95% confidence interval [41%, 65%]) completed the approach sequence. Although the correlation of child age in months (Mean (M) = 60.1, standard deviation = 16.5, N = 70) and highest successful step (M = 5.8, standard deviation = 2.6, 95% confidence interval [5.2, 6.4]) completed was not statistically significant at the 0.05 level, r (68) = 0.21, P = 0.08, 95% confidence interval [−0.03, 0.42], the proportion of children aged 6‐7 years who successfully completed all steps (14 of 21, 67%, 95% confidence interval [50%, 84%]) was significantly different from the proportion of children aged 2‐3 years who completed all steps (six of 23, 26%, 95% confidence interval [11%, 41%]) (Fisher's exact test, two‐tailed P = 0.0148). A failure rate of at least 50% should be included into group size calculations when performing studies with young children (2‐7 years), in addition to motion and other experimental factors. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Standardization of relative cerebral blood volume (rCBV) image maps for ease of both inter‐ and intrapatient comparisons
Authors: Bedekar Devyani , Jensen Todd , Schmainda Kathleen M. 
Published: May 2010

AbstractRelative cerebral blood volume (rCBV) measured using dynamic susceptibility contrast MRI suffers from interpatient and interstudy variability for the same tissue type. Traditionally, when a more quantitative assessment of rCBV is required, as for comparison across studies and patients, the rCBV values are normalized to the rCBV in a reference region such as normal‐appearing white matter. However, this technique of normalization is subjective and time consuming and introduces user‐dependent variability. In this study, we demonstrate that a method called standardization, applied to rCBV maps, is an objective means of translating all rCBV values to a consistent scale. This approach reduces interpatient and interstudy variability for the same tissue type, thus enabling easy and accurate visual and quantitative comparison across studies. One caveat to this approach is that it is not appropriate for the evaluation of global changes in blood volume, since systematic differences are removed in the process of standardization. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Thoracic Aortic Aneurysms and Dissections: Endovascular Treatment
Authors: Baril Donald T. , Cho Jae S. , Chaer Rabih A. , Makaroun Michel S. 
Published: May 2010

AbstractThe treatment of thoracic aortic disease has changed radically with the advances made in endovascular therapy since the concept of thoracic endovascular aortic repair was first described 15 years ago. Currently, there is a diverse array of endografts that are commercially available to treat the thoracic aorta. Multiple studies, including industry‐sponsored and single‐institution reports, have demonstrated excellent outcomes of thoracic endovascular aortic repair for the treatment of thoracic aortic aneurysms, with less reported perioperative morbidity and mortality in comparison with conventional open repair. Additionally, similar outcomes have been demonstrated for the treatment of type B dissections. However, the technology remains relatively novel, and larger studies with longer term outcomes are necessary to more fully evaluate the role of endovascular therapy for the treatment of thoracic aortic disease. This review examines the currently available thoracic endografts, preoperative planning for thoracic endovascular aortic repair, and outcomes of thoracic endovascular aortic repair for the treatment of both thoracic aortic aneurysms and type B aortic dissections. Mt Sinai J Med 77:256–269, 2010. © 2010 Mount Sinai School of Medicine
Sports‐Related Injuries in the Young Female Athlete
Authors: Colvin Alexis C. , Lynn Abigail 
Published: May 2010

AbstractThe number of females participating in sports continues to increase. Adolescent and preadolescent females are at a risk injury to both their open growth plates as well as their joints. The purpose of this article is to review the common injuries seen with the most popular sports with females. Mt Sinai J Med 77:307–314, 2010. © 2010 Mount Sinai School of Medicine
Abdominal Aortic Aneurysms: Endovascular Repair
Authors: Jim Jeffrey , Sanchez Luis A. 
Published: May 2010

AbstractSince its introduction 2 decades ago, endovascular repair of abdominal aortic aneurysms has continued to evolve, and many now consider it the optimal treatment modality for infrarenal abdominal aortic aneurysms. There are currently 5 commercially approved endografts, each with its unique design, and all can be utilized with excellent technical results. The endovascular repair is performed with radiographic guidance utilizing general, spinal, or local anesthesia. Endoleak is the most common complication and unique to the procedure. Routine postoperative surveillance imaging is essential to ensure long‐term success. Clinical trials have demonstrated lower perioperative mortality and morbidity for endovascular repair of abdominal aortic aneurysms compared with open repair. However, evidence for long‐term survival benefits is lacking. Furthermore, the benefits of endovascular repair in “high‐risk” patients remain unclear. Though there is a subset of patients who benefit from endovascular repair of abdominal aortic aneurysms, objective identification of this population remains a challenge. Practitioners currently recommend elective repair for aneurysms ≥ 5.5 cm in diameter and in selected patients with smaller aneurysms. Current studies are underway to evaluate the utility of endovascular repair in small aneurysms. Patients with ruptured aneurysms, due to the high morbidity and mortality associated with their management, may significantly benefit from endovascular repair. Although there is a lack of sufficient randomized controlled trial data, available evidence does support the use of endovascular repair for ruptured abdominal aortic aneurysms. Multiple newer endovascular devices are under clinical investigation to address the limitations of available devices. Ultimately, we may be able to treat the vast majority of patients with all types of abdominal and thoracoabdominal aortic aneurysms with endovascular devices. Mt Sinai J Med 77:238–249, 2010. © 2010 Mount Sinai School of Medicine
Visceral Artery Aneurysms: Review of Current Management Options
Authors: Sachdev‐Ost Ulka 
Published: May 2010

AbstractVisceral artery aneurysms are relatively rare clinical entities, although their detection is rising due to an increased use of cross‐sectional imaging. Rupture is the most devastating complication, and is associated with a high morbidity and mortality. For this reason, elective repair is preferable in the appropriately chosen patient. In general, splenic artery aneurysms measuring 2 cm or larger and those found in women of childbearing age and in persons undergoing liver transplantation should be treated. Hepatic artery aneurysms 2 cm or larger and those that are multiple or nonatherosclerotic in nature should be repaired in the appropriate patient due to a higher risk of rupture. Endovascular coil embolization has excellent success rates and is the first‐line treatment for anatomically suitable splenic artery aneurysms and intrahepatic hepatic artery aneurysms. However, reperfusion is an important complication of endovascular management. Aneurysms involving the celiac, superior mesenteric, pancreaticoduodenal, gastroduodenal, and inferior mesenteric arteries, as well as visceral artery pseudoaneurysms, are unpredictable and should be repaired in the appropriate medical patient. These aneurysms are often amenable to ligation due to the presence of collateral circulation. Endovascular management is particularly useful in the treatment of pseudoaneurysms where comorbidities and previous surgery make open surgical repair less desirable. Mt Sinai J Med 77:296–303, 2010. © 2010 Mount Sinai School of Medicine
Ruptured Abdominal Aortic Aneurysms: Role of Endovascular Therapy
Authors: Cayne Neal S. , Veith Frank J. 
Published: May 2010

AbstractRuptured abdominal aortic aneurysms historically have high mortality rates. Despite improvements in many open surgical techniques and perioperative care, these mortality rates have not significantly changed. Some of the reasons for the high mortality rates include the excessive blood loss and hypothermia that occur during open operative repair. The blood loss and hypothermia, combined with resuscitative dilutional coagulopathy, can lead to an irreversible spiraling coagulopathy that ultimately ends in the patient's demise. The availability of endovascular approaches to treat abdominal aortic aneurysms in the early 1990s offered an opportunity to substantially alter the treatment outcomes of ruptured abdominal aortic aneurysms. Endovascular repair offers many advantages, including rapid aortic control under local anesthesia, as well as an opportunity to limit the hypothermia and blood loss that occur with an open abdomen. This article will review the endovascular management of ruptured abdominal aortic aneurysms and describe the endovascular techniques for safe and effective treatment. Mt Sinai J Med 77:250–255, 2010. © 2010 Mount Sinai School of Medicine
Intracranial Aneurysms: Endovascular Treatment
Authors: Moyle Henry , Patel Aman B. 
Published: May 2010

AbstractThe incidence of subarachnoid hemorrhage is estimated at 5 to 10 per 100,000 per year. In patients who survive the initial hemorrhage, the repeat hemorrhage rate is 15% to 20% in the first 2 weeks after presentation and is associated with devastating clinical outcomes even graver than the initial rupture. The current options for aneurysm treatment are surgical clipping and, since the mid‐1990s, neuroendovascular coil embolization. The former was at one time the gold standard of care, but consistent with the trend in modern medicine toward less‐invasive procedures, the latter has steadily gained prominence. Although there is still controversy as to its long‐term durability and safety, it is now the preferred procedure. This article describes the procedure's antecedents, rationale, and essential components. Mt Sinai J Med 77:279–285, 2010. © 2010 Mount Sinai School of Medicine
Deep Vein Thrombosis: Endovascular Management
Authors: Lookstein Robert A. , Giordano Christopher F. 
Published: May 2010

AbstractDeep vein thrombosis is a condition that affects hundreds of thousands of patients each year. The major complications include pulmonary embolus with the potential for loss of life and post‐thrombotic syndrome with the potential for loss of function of the limb. Extensive clinical research over the last 40 years has improved the techniques to remove the thrombus from the affected limb and reduce the likelihood of developing post‐thrombotic syndrome. These treatments have included intravenous systemic thrombolysis, catheter‐directed thrombolysis, surgical thrombectomy, and most recently pharmacomechanical thrombectomy to rapidly fragment, lyse, and remove the thrombus from the affected limb. This last technique may finally transform the treatment of acute deep vein thrombus from strictly conservative medical therapy to a minimally invasive procedure that can remove the thrombus to improve the quality of life of millions of individuals suffering from the symptoms of deep vein thrombosis. Mt Sinai J Med 77:286–295, 2010. © 2010 Mount Sinai School of Medicine
Minimally Invasive Vein Surgery: Latest Options for Vein Disease
Authors: Elias Steven 
Published: May 2010

AbstractThe goal of treatment for venous disease is to decrease ambulatory venous hypertension. Various strategies are employed. These can be divided into exogenous and endogenous treatments. Exogenous methods concern those employed from the outside of the limb, such as compression and elevation. Endogenous modalities treat from inside the limb the underlying venous pathology due to venous valvular dysfunction or venous obstruction. Traditional endogenous procedures include stripping, ligation, and phlebectomy. All these procedures require incisions, anesthesia, and perhaps hospitalization, and involve significant discomfort. Newer minimally invasive vein surgery procedures now exist. These are all same‐day, outpatient procedures, usually involving local anesthesia. Most can be performed percutaneously without incisions. Patients ambulate the day of the procedure. Morbidity is less than 1%. This article summarizes the concept of minimally invasive vein surgery and summarizes new technologies to manage all forms of venous disease. Mt Sinai J Med 77:270–278, 2010. © 2010 Mount Sinai School of Medicine
Pore scale study of permeability and tortuosity for flow through particulate media using Lattice Boltzmann method
Authors: Ghassemi Ali , Pak Ali 
Published: May 2010

AbstractIn this paper, Lattice Boltzmann method (LBM) has been used to study the effects of permeability and tortuosity on flow through saturated particulate media and identify the relationships between permeability and tortuosity with other parameters such as particles diameter, grain specific surface, and porosity. LBM is a simple kinematic model that can incorporate the essential physics of microscopic and mesoscopic processes involved in flow through granular soils.The obtained results indicate that the 2D LB model, due to its inherent theoretical advantages, is capable of demonstrating that the porosity and specific surface are the most influential parameters in determining the intrinsic permeability of granular media. The obtained results show that particles' size diameter has a two‐fold effect on the coefficient of permeability: one is through specific surface and the other is by tortuosity factor. Numerical study also reveals that tortuosity of granular soils decreases almost linearly with increasing the porosity. Copyright © 2010 John Wiley & Sons, Ltd.