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81.
目的 校正锥形束CT投影中的散射信号,以提高图像质量。 方法 使用条状挡板测量Varian机载kV级锥形束CT投影图像中的散射信号,并将其从再次扫描的投影中扣除,以获得原始射线的投影图像。使用空域自适应的BayesShrink小波对投影图像进行去噪处理,并导入Varian On Board Imager工作站进行重建;比较处理前后的图像质量。 结果 校正后图像的低对比度分辨力提高,噪声降低,CT值的准确性和均匀性得到改善。 结论 条状挡板能准确获取投影图像中的散射信号;扣除散射信号后使用小波阈值法去噪,可有效提高图像质量。 相似文献
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Freddy Odille Sergio Uribe Philip G. Batchelor Claudia Prieto Tobias Schaeffter David Atkinson 《Magnetic resonance in medicine》2010,63(5):1247-1257
This paper describes an acquisition and reconstruction strategy for cardiac cine MRI that does not require the use of electrocardiogram or breath holding. The method has similarities with self‐gated techniques as information about cardiac and respiratory motion is derived from the imaging sequence itself; here, by acquiring the center k‐space line at the beginning of each segment of a balanced steady‐state free precession sequence. However, the reconstruction step is fundamentally different: a generalized reconstruction by inversion of coupled systems is used instead of conventional gating. By correcting for nonrigid cardiac and respiratory motion, generalized reconstruction by inversion of coupled systems (GRICS) uses all acquired data, whereas gating rejects data acquired in certain motion states. The method relies on the processing and analysis of the k‐space central line data: local information from a 32‐channel cardiac coil is used in order to automatically extract eigenmodes of both cardiac and respiratory motion. In the GRICS framework, these eigenmodes are used as driving signals of a motion model. The motion model is defined piecewise, so that each cardiac phase is reconstructed independently. Results from six healthy volunteers, with various slice orientations, show improved image quality compared to combined respiratory and cardiac gating. Magn Reson Med 63:1247–1257, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
84.
Toshimune Kambara Sandeep Sood Zahraa Alqatan Christine Klingert Diksha Ratnam Akane Hayakawa Yasuo Nakai Aimee F. Luat Rajkumar Agarwal Robert Rothermel Eishi Asano 《Clinical neurophysiology》2018,129(1):145-154
A number of investigators have reported that event-related augmentation of high-gamma activity at 70–110?Hz on electrocorticography (ECoG) can localize functionally-important brain regions in children and adults who undergo epilepsy surgery. The advantages of ECoG-based language mapping over the gold-standard stimulation include: (i) lack of stimulation-induced seizures, (ii) better sensitivity of localization of language areas in young children, and (iii) shorter patient participant time. Despite its potential utility, ECoG-based language mapping is far less commonly practiced than stimulation mapping. Here, we have provided video presentations to explain, point-by-point, our own hardware setting and time–frequency analysis procedures. We also have provided standardized auditory stimuli, in multiple languages, ready to be used for ECoG-based language mapping. Finally, we discussed the technical aspects of ECoG-based mapping, including its pitfalls, to facilitate appropriate interpretation of the data. 相似文献
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Nanae Tsuchiya Edwin JR van Beek Yoshiharu Ohno Hiroto Hatabu Hans-Ulrich Kauczor rew Swift Jens Vogel-Claussen J rgen Biederer James Wild Mark O Wielp tz Mark L Schiebler 《World journal of radiology》2018,10(6):52-64
Pulmonary contrast enhanced magnetic resonance angiography (CE-MRA) is useful for the primary diagnosis of pulmonary embolism (PE). Many sites have chosen not to use CE-MRA as a first line of diagnostic tool for PE because of the speed and higher efficacy of computerized tomographic angiography (CTA). In this review, we discuss the strengths and weaknesses of CE-MRA and the appropriate imaging scenarios for the primary diagnosis of PE derived from our unique multi-institutional experience in this area. The optimal patient for this test has a low to intermediate suspicion for PE based on clinical decision rules. Patients in extremis are not candidates for this test. Younger women (< 35 years of age) and patients with iodinated contrast allergies are best served by using this modality We discuss the history of the use of this test, recent technical innovations, artifacts, direct and indirect findings for PE, ancillary findings, and the effectiveness (patient outcomes) of CE-MRA for the exclusion of PE. Current outcomes data shows that CE-MRA and NM V/Q scans are effective alternative tests to CTA for the primary diagnosis of PE. 相似文献
87.
The Goldvalve balloon is the only currently available detachable balloon. We undertook a study to determine safety and imaging artifacts in a MR environment. We found no evidence for heating or deflection of the balloon in a comprehensive series of in vitro experiments at 3 T. MR imaging at field strengths up to 3 T of patients with implanted Goldvalve balloons is safe. Imaging artifacts are minimal. 相似文献
88.
Introduction: The latest open MRI technology allows to perform open and closed surgical procedures under real-time imaging. Before performing
spinal trauma surgery preclinical examinations had to be done to evaluate the artifacts caused by the implants. Methods: The MRT presented is a prototype developed by GE. Two vertically positioned magnetic coils are installed in an operation
theater. By that means two surgeons are able to access the patient between the two coils. Numerous tests regarding the material
of instruments and implants were necessary in advance. The specific size of the artifact depending on the pulse sequence and
the positioning within the magnetic field had to be examined. Results: The magnifying factors of the artifact in the spin echo sequence regarding titanium are between 1.7 and 3.2, depending on
the direction of the magnetic vector. Regading stainless steel they are between 8.4 and 8.5. In the gradient echo sequence
the factors are between 7.5 and 7.7 for titanium and between 16.9 and 18.0 for stainless steel. The tip of an implant is imaged
with an accuracy of 0 to 2 mm. Since September 1997 16 patients with unstable fractures of the thoracic and lumbar spine have
been treated by dorsal instrumentation in the open MRI. Percutaneous insertion of the internal fixator has proven a successful
minimally invasive procedure. The positioning of the screws in the pedicle is secure, the degree of indirect reduction of
the posterior wall of the vertebral body can be imaged immediately. The diameter of the spinal canal can be determined in
any plane. Discussion and conclusion: The open MRI has proven useful in orthopedic and trauma surgery. The size and configuration of the artifacts caused by instruments
and implants is predictable. Therefore exact positioning of the implants is achieved more easily. Dorsal instrumentation
of unstable thoracolumbar fractures with a percutaneous technique has turned out safe and less traumatic under MR-imaging.
Real-time imaging of soft tissue and bone in any plane improves security for the patient and allows the surgeon to work less
invasively and more precisely.
Received: 30 July 1999 Accepted: 7 August 1999 相似文献
89.
Guillaume Lio Stéphane Thobois Bénédicte Ballanger Brian Lau Philippe Boulinguez 《Clinical neurophysiology》2018,129(10):2170-2185
A major question for deep brain stimulation (DBS) research is understanding how DBS of one target area modulates activity in different parts of the brain. EEG gives privileged access to brain dynamics, but its use with implanted patients is limited since DBS adds significant high-amplitude electrical artifacts that can completely obscure neural activity measured using EEG. Here, we systematically review and discuss the methods available for removing DBS artifacts. These include simple techniques such as oversampling, antialiasing analog filtering and digital low-pass filtering, which are necessary but typically not sufficient to fully remove DBS artifacts when each is used in isolation. We also cover more advanced methods, including techniques tracking outliers in the frequency-domain, which can be effective, but are rarely used. The reason for that is twofold: First, it requires advanced skills in signal processing since no user friendly tool for removing DBS artifacts is currently available. Second, it involves fine-tuning to avoid over-aggressive filtering. We highlight an open-source toolbox incorporating most artifact removal methods, allowing users to combine different strategies. 相似文献
90.