scholarly journals Measurement of Lead Localization Accuracy Based on Magnetic Resonance Imaging

2021 ◽  
Vol 15 ◽  
Author(s):  
Changgeng He ◽  
Feng Zhang ◽  
Linze Li ◽  
Changqing Jiang ◽  
Luming Li
Keyword(s):  
Magnetic Field ◽  
Magnetic Resonance ◽  
Mr Images ◽  
Registration Method ◽  
Localization Accuracy ◽  
Direct Localization ◽  
The Individual ◽  
Localization Approach ◽  
Post Implantation

Post-implantation localization of deep brain stimulation (DBS) lead based on a magnetic resonance (MR) image is widely used. Existing localization methods use artifact center method or template registration method, which may lead to a considerable deviation of > 2 mm, and result in severe side effects or even surgical failure. Accurate measurement of lead position can instantly inform surgeons of the imprecise implantation. This study aimed to identify the influencing factors in DBS lead post-implantation localization approach, analyze their influence, and describe a localization approach that uses the individual template method to reduce the deviation. We verified that reconstructing direction should be parallel or perpendicular to lead direction, instead of the magnetic field. Besides, we used simplified relationship between magnetic field angle and deviation error to correct the localization results. The mean localization error can be reduced after correction and favors the feasibility of direct localization of DBS lead using MR images. We also discussed influence of in vivo noise on localization frequency and the possibility of using only MR images to localize the contacts.

Spectroscopic imaging of human disease

1996 ◽  
Vol 54 ◽  
pp. 884-885
Author(s):  
D.J. Meyerhoff
Keyword(s):  
Magnetic Field ◽  
Magnetic Resonance ◽  
Field Gradient ◽  
Human Disease ◽  
Morphological Changes ◽  
Magnetic Field Gradient ◽  
Spectroscopic Imaging ◽  
Resonance Spectroscopy ◽  
Tissue Water

Magnetic Resonance Imaging (MRI) observes tissue water in the presence of a magnetic field gradient to study morphological changes such as tissue volume loss and signal hyperintensities in human disease. These changes are mostly non-specific and do not appear to be correlated with the range of severity of a certain disease. In contrast, Magnetic Resonance Spectroscopy (MRS), which measures many different chemicals and tissue metabolites in the millimolar concentration range in the absence of a magnetic field gradient, has been shown to reveal characteristic metabolite patterns which are often correlated with the severity of a disease. In-vivo MRS studies are performed on widely available MRI scanners without any “sample preparation” or invasive procedures and are therefore widely used in clinical research. Hydrogen (H) MRS and MR Spectroscopic Imaging (MRSI, conceptionally a combination of MRI and MRS) measure N-acetylaspartate (a putative marker of neurons), creatine-containing metabolites (involved in energy processes in the cell), choline-containing metabolites (involved in membrane metabolism and, possibly, inflammatory processes),

scholarly journals Magnetic Field Interactions of Copper-Containing Intrauterine Devices in 3.0-Tesla Magnetic Resonance Imaging: In Vivo Study

2013 ◽  
Vol 14 (3) ◽  
pp. 416 ◽  
Author(s):  
Vanessa Berger-Kulemann ◽  
Henrik Einspieler ◽  
Nilouparak Hachemian ◽  
Daniela Prayer ◽  
Siegfried Trattnig ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Field ◽  
Magnetic Resonance ◽  
In Vivo Study ◽  
Resonance Imaging ◽  
Intrauterine Devices ◽  
3.0 Tesla

In vivo diffusion–perfusion magnetic resonance imaging of acute cerebral ischemia

1991 ◽  
Vol 69 (11) ◽  
pp. 1719-1725 ◽  
Author(s):  
John Kucharczyk ◽  
Jan Mintorovitch ◽  
Haleh Asgari ◽  
Mitsuharu Tsuura ◽  
Michael Moseley
Keyword(s):  
Cerebral Ischemia ◽  
Magnetic Resonance ◽  
Resonance Imaging ◽  
Mr Images ◽  
Ischemic Brain ◽  
Diffusion Weighted ◽  
Acute Cerebral Ischemia ◽  
Planar Images ◽  
Echo Planar

We compared the anatomic extent and severity of ischemic brain injury shown on diffusion-weighted magnetic resonance (MR) images, with cerebral tissue perfusion deficits demonstrated by a nonionic intravascular T2*-shortening magnetic susceptibility contrast agent used in conjunction with standard T2-weighted spin-echo and gradient-echo echo-planar images. Diffusion-weighted images displayed increased signal intensity in the vascular territory of the middle cerebral artery 25–40 min after permanent occlusion, whereas T2-weighted images without contrast were negative or equivocal for at least 2–3 h after stroke was induced. Contrast-enhanced T2-weighted and echo-planar images revealed perfusion deficits that were spatially closely related to the anatomic regions of ischemic tissue injury. These data indicate that diffusion-weighted MR images are very sensitive to early onset pathophysiologic changes induced by acute cerebral ischemia. Combined sequential diffusion–perfusion imaging enables noninvasive in vivo examination of the relationship between hypoperfusion and evolving ischemic brain injury.Key words: in vivo, diffusion, perfusion, acute cerebral ischemia, magnetic resonance imaging.

scholarly journals Development of a Hybrid Magnetic Resonance and Ultrasound Imaging System

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Victoria Sherwood ◽  
John Civale ◽  
Ian Rivens ◽  
David J. Collins ◽  
Martin O. Leach ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Focused Ultrasound ◽  
Imaging System ◽  
Single Point ◽  
Image Data ◽  
High Intensity Focused Ultrasound ◽  
Thigh Muscle ◽  
Mr Images ◽  
Rf Noise

A system which allows magnetic resonance (MR) and ultrasound (US) image data to be acquired simultaneously has been developed. B-mode and Doppler US were performed inside the bore of a clinical 1.5 T MRI scanner using a clinical 1–4 MHz US transducer with an 8-metre cable. Susceptibility artefacts and RF noise were introduced into MR images by the US imaging system. RF noise was minimised by using aluminium foil to shield the transducer. A study of MR and B-mode US image signal-to-noise ratio (SNR) as a function of transducer-phantom separation was performed using a gel phantom. This revealed that a 4 cm separation between the phantom surface and the transducer was sufficient to minimise the effect of the susceptibility artefact in MR images. MR-US imaging was demonstratedin vivowith the aid of a 2 mm VeroWhite 3D-printed spherical target placed over the thigh muscle of a rat. The target allowed single-point registration of MR and US images in the axial plane to be performed. The system was subsequently demonstrated as a tool for the targeting and visualisation of high intensity focused ultrasound exposure in the rat thigh muscle.

Validation of Cartilage Thickness Calculations Using Indentation Analysis

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Matthew F. Koff ◽  
Le Roy Chong ◽  
Patrick Virtue ◽  
Dan Chen ◽  
Xioanan Wang ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Measurement Techniques ◽  
Magnetic Resonance Images ◽  
Cartilage Thickness ◽  
Mr Images ◽  
Data Set ◽  
Data Points ◽  
Indentation Analysis ◽  
Thickness Measurements

Different methods have been used to cross-validate cartilage thickness measurements from magnetic resonance images (MRIs); however, a majority of these methods rely on interpolated data points, regional mean and/or maximal thickness, or surface mean thickness for data analysis. Furthermore, the accuracy of MRI cartilage thickness measurements from commercially available software packages has not necessarily been validated and may lead to an under- or overestimation of cartilage thickness. The goal of this study was to perform a matching point-to-point validation of indirect cartilage thickness calculations using a magnetic resonance (MR) image data set with direct cartilage thickness measurements using biomechanical indentation testing at the same anatomical locations. Seven bovine distal femoral condyles were prepared and a novel phantom filled with dilute gadolinium solution was rigidly attached to each specimen. High resolution MR images were acquired, and thickness indentation analysis of the cartilage was performed immediately after scanning. Segmentation of the MR data and cartilage thickness calculation was performed using semi-automated software. Registration of MR and indentation data was performed using the fluid filled phantom. The inter- and intra-examiner differences of the measurements were also determined. A total of 105 paired MRI-indentation thickness data points were analyzed, and a significant correlation between them was found (r=0.88, p<0.0001). The mean difference (±std. dev.) between measurement techniques was 0.00±0.23 mm, with Bland–Altman limits of agreement of 0.45 mm and −0.46 mm. The intra- and inter-examiner measurement differences were 0.03±0.22 mm and 0.05±0.24 mm, respectively. This study validated cartilage thickness measurements from MR images with thickness measurements from indentation by using a novel phantom to register the image-based and laboratory-based data sets. The accuracy of the measurements was comparable to previous cartilage thickness validation studies in literature. The results of this study will aid in validating a tool for clinical evaluation of in-vivo cartilage thickness.

Model Studies of Nonsteady Flow Using Magnetic Resonance Imaging

1990 ◽  
Vol 112 (1) ◽  
pp. 93-99 ◽  
Author(s):  
Ding-Yu Fei ◽  
Kenneth A. Kraft ◽  
Panos P. Fatouros
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Velocity Profiles ◽  
Resonance Imaging ◽  
Mr Images ◽  
Model Studies ◽  
Physiological Limits ◽  
Theoretical Predictions ◽  
Magnetic Resonance Imaging Mri

A bolus-tracking magnetic resonance imaging (MRI) method has been employed to measure velocity profiles for oscillatory flow with and without a steady flow component as well as pulsatile flow in an axisymmetric tube model. A range of flow conditions within normal physiological limits was tested. The imaged velocity profiles were observed to be generally in accord with theoretical predictions. Instantaneous flow rates calculated from the MR images agreed well with those assessed using an ultrasonic flowmeter. Because MRI is noninvasive and poses few risks to subjects, this technique is potentially useful for studying vascular hemodynamics in vivo.

scholarly journals Relationship between patellofemoral finite helical axis and femoral trans-epicondylar axis using a static magnetic resonance-based methodology

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Zhenguo Yu ◽  
Hong Cai ◽  
Bin Yang ◽  
Jie Yao ◽  
Ke Zhang ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Knee Flexion ◽  
Spline Interpolation ◽  
Helical Axis ◽  
Mr Images ◽  
Full Extension ◽  
Epicondylar Axis ◽  
Maximum Angle ◽  
Finite Helical Axis

Abstract Background To manage patellofemoral joint disorders, a complete understanding of the in vivo patellofemoral kinematics is critical. However, as one of the parameters of joint kinematics, the location and orientation of the patellofemoral finite helical axis (FHA) remains unclear. The purpose of this study is to quantify the location and orientation of the patellar FHA, both in vivo and non-invasively at various flexion angles, and evaluate the relationship of the FHA and the trans-epicondylar axis (TEA). Methods The magnetic resonance (MR) images of 18 unilateral knees were collected at full extension, 30°, 60°, 90°, and maximum angle of knee flexion. Three-dimensional models of the knee joint at different flexion angles were created using the MR images, and then used to calculate the patellar tracking and FHA with a spline interpolation algorithm. By using a coordinate system based on the TEA, the FHA tracking was quantified. Six parameters concerning the location and orientation of the patellar FHA were analysed. Results The average patellar FHA drew an L-shaped tracking on the midsagittal plane moving from the posteroinferior to the anterosuperior side of the TEA with knee flexion. Before 90° flexion, the patellar rotational radius decreased slightly, with an average value of 5.65 ± 1.09 cm. During 20° to 90° knee flexion, the average angle between the patellar FHA and the TEA was approximately 10° and that between the FHA and the coronal plane was maintained at about 0°, while that between the FHA and the level plane fluctuated between − 10° and 10°. Conclusions This study quantitatively reported the continuous location and direction of the patellar FHA during knee flexion. The patellar FHA was close to but not coincident with the femoral TEA both in location and orientation, and the patellar rotational radius decreased slightly with knee flexion. These findings could provide a clear direction for further studies on the difference in patellofemoral FHA among various types of patellofemoral disorders, and provide a foundation for the application of FHA in surgical evaluation, preoperative planning and prosthesis design, thereby assisting in the diagnosis and treatment of patellofemoral disorders.

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