Intraoperative brain shift prediction using a 3D inhomogeneous patient-specific finite element model

2007 ◽  
Vol 106 (1) ◽  
pp. 164-169 ◽  
Author(s):  
Jingwen Hu ◽  
Xin Jin ◽  
Jong B. Lee ◽  
Liying Zhang ◽  
Vipin Chaudhary ◽  
...  
Keyword(s):  
Finite Element ◽  
Mr Imaging ◽  
Patient Specific ◽  
Computer Assisted ◽  
Brain Shift ◽  
Fe Modeling ◽  
Mr Images ◽  
Pia Mater ◽  
Template Model ◽  
Presurgical Planning

Object The aims of this study were to develop a three-dimensional patient-specific finite element (FE) brain model with detailed anatomical structures and appropriate material properties to predict intraoperative brain shift during neurosurgery and to update preoperative magnetic resonance (MR) images using FE modeling for presurgical planning. Methods A template-based algorithm was developed to build a 3D patient-specific FE brain model. The template model is a 50th percentile male FE brain model with gray and white matter, ventricles, pia mater, dura mater, falx, tentorium, brainstem, and cerebellum. Gravity-induced brain shift after opening of the dura was simulated based on one clinical case of computer-assisted neurosurgery for model validation. Preoperative MR images were updated using an FE model and displayed as intraoperative MR images easily recognizable by surgeons. To demonstrate the potential of FE modeling in presurgical planning, intraoperative brain shift was predicted for two additional head orientations. Two patient-specific FE models were constructed. The mesh quality of the resulting models was as high as that of the template model. One of the two FE models was selected to validate model-predicted brain shift against data acquired on intraoperative MR imaging. The brain shift predicted using the model was greater than that observed intraoperatively but was considered surgically acceptable. Conclusions A set of algorithms for developing 3D patient-specific FE brain models is presented. Gravity-induced brain shift can be predicted using this model and displayed on high-resolution MR images. This strategy can be used not only for updating intraoperative MR imaging, but also for presurgical planning.

Computer assisted evaluation of plate osteosynthesis of diaphyseal femur fracture considering interfragmentary movement: a finite element study

2017 ◽  
Vol 62 (3) ◽  
Author(s):  
Claudia Wittkowske ◽  
Stefan Raith ◽  
Maximilian Eder ◽  
Alexander Volf ◽  
Jan S. Kirschke ◽  
...  
Keyword(s):  
Finite Element ◽  
Plate Osteosynthesis ◽  
Computation Time ◽  
Fe Analysis ◽  
Patient Specific ◽  
Osteoporotic Bone ◽  
Computer Assisted ◽  
Efficient Computation ◽  
User Input ◽  
Patient Specific Modeling

AbstractA semi-automated workflow for evaluation of diaphyseal fracture treatment of the femur has been developed and implemented. The aim was to investigate the influence of locking compression plating with diverse fracture-specific screw configurations on interfragmentary movements (IFMs) with the use of finite element (FE) analysis. Computed tomography (CT) data of a 22-year-old non-osteoporotic female were used for patient specific modeling of the inhomogeneous material properties of bone. Hounsfield units (HU) were exported and assigned to elements of a FE mesh and converted to mechanical properties such as the Young’s modulus followed by a linear FE analysis performed in a semi-automated fashion. IFM on the near and far cortex was evaluated. A positive correlation between bridging length and IFM was observed. Optimal healing conditions with IFMs between 0.5 mm and 1 mm were found in a constellation with a medium bridging length of 80 mm with three unoccupied screw holes around the fracture gap. Usage of monocortical screws instead of bicortical ones had negligible influence on the evaluated parameters when modeling non-osteoporotic bone. Minimal user input, automation of the procedure and an efficient computation time ensured quick delivery of results which will be essential in a future clinical application.

ASSESSMENT OF OSTEOPOROTIC FEMORAL FRACTURE RISK: FINITE ELEMENT METHOD AS A POTENTIAL REPLACEMENT FOR CURRENT CLINICAL TECHNIQUES

2015 ◽  
Vol 15 (03) ◽  
pp. 1530003 ◽  
Author(s):  
SVEN VAN DEN MUNCKHOF ◽  
ALI ASADI NIKOOYAN ◽  
AMIR ABBAS ZADPOOR
Keyword(s):  
Finite Element ◽  
Fracture Risk ◽  
Risk Prediction ◽  
Femoral Fracture ◽  
Imaging Techniques ◽  
Pharmacological Intervention ◽  
Patient Specific ◽  
Fe Modeling ◽  
Fe Method ◽  
Fracture Risk Prediction

Femoral fracture risk prediction is a necessary step preceding effective pharmacological intervention or pre-operative planning. Current clinical methods for fracture risk prediction rely on 2D imaging methods and have limited predictive value. Researchers are therefore trying to find improved methods for fracture prediction. During last few decades, many studies have focused on integration of 3D imaging techniques and the finite element (FE) method to improve the accuracy of fracture assessment techniques. In this paper, we review the recent advances in FE and other techniques for predicting the risk of femoral fractures. Based on a number of selected studies, the different steps that are involved in generation of patient-specific FE models are reviewed with particular emphasis on the fracture criteria. The inaccuracies that might arise due to the imperfections of the involved steps are also discussed. It is concluded that compared to image- and geometry-based techniques, FE is a more promising approach for prediction of fracture loads. However, certain technological advancements in FE modeling protocols are required before FE modeling can be recruited in clinical settings.

scholarly journals Patient-specific Hip Fracture Strength Assessment with Microstructural MR Imaging–based Finite Element Modeling

Radiology ◽  
2017 ◽  
Vol 283 (3) ◽  
pp. 854-861 ◽  
Author(s):  
Chamith S. Rajapakse ◽  
Alexandra Hotca ◽  
Benjamin T. Newman ◽  
Austin Ramme ◽  
Shaleen Vira ◽  
...  
Keyword(s):  
Finite Element ◽  
Hip Fracture ◽  
Mr Imaging ◽  
Finite Element Modeling ◽  
Fracture Strength ◽  
Patient Specific ◽  
Strength Assessment ◽  
Element Modeling

scholarly journals Cardiac MR images of thalassemia major patients with myocardial iron overload: a data note

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Emad Shiae Ali ◽  
Mohamad Amin Bakhshali ◽  
Seyed Jafar Shoja Razavi ◽  
Hoorak Poorzand ◽  
Parvaneh Layegh
Keyword(s):  
Heart Failure ◽  
Mr Imaging ◽  
Iron Overload ◽  
Thalassemia Major ◽  
Patient Specific ◽  
Control Group ◽  
Specific Information ◽  
Myocardial Iron ◽  
Mr Images ◽  
Cardiac Mr

Abstract Objective Patients with thalassemia major (TM) have the highest mortality rate due to heart failure induced by myocardial iron overload. However, T2* weighted MR imaging is currently a gold standard approach for measuring iron overload. Examining ventricular volumes with magnetic resonance imaging (MR imaging) and measuring myocardial iron overload in TM patients allows for an early prediction of heart failure. This dataset includes cardiac MR images of TM patients and the control group with clinical and echocardiographic data. This dataset may be useful to researchers investigating myocardial iron overload. This dataset can also be used for medical image processing applications, such as ventricle segmentation. Data description This study provides open-source cardiac MR images of 50 subjects and clinical and echocardiographic data. From February 2016 to January 2019, all images and clinical data were obtained from the MRI department of a general hospital in Mashhad, Iran. All the images are 16-bit gray-scale and stored in DICOM format. All patient-specific information is removed from image headers to preserve patient privacy. In addition, all images associated with each subject are compressed and saved in the RAR format.

scholarly journals A Novel Method for Quantifying Smooth Regional Variations in Myocardial Contractility Within an Infarcted Human Left Ventricle Based on Delay-Enhanced Magnetic Resonance Imaging

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Martin Genet ◽  
Lik Chuan Lee ◽  
Liang Ge ◽  
Gabriel Acevedo-Bolton ◽  
Nick Jeung ◽  
...  
Keyword(s):  
Heart Failure ◽  
Finite Element ◽  
Magnetic Resonance ◽  
Finite Element Model ◽  
Myocardial Contractility ◽  
Element Model ◽  
Patient Specific ◽  
Mr Images ◽  
Pixel Intensity ◽  
Regional Variations

Heart failure is increasing at an alarming rate, making it a worldwide epidemic. As the population ages and life expectancy increases, this trend is not likely to change. Myocardial infarction (MI)-induced adverse left ventricular (LV) remodeling is responsible for nearly 70% of heart failure cases. The adverse remodeling process involves an extension of the border zone (BZ) adjacent to an MI, which is normally perfused but shows myofiber contractile dysfunction. To improve patient-specific modeling of cardiac mechanics, we sought to create a finite element model of the human LV with BZ and MI morphologies integrated directly from delayed-enhancement magnetic resonance (DE-MR) images. Instead of separating the LV into discrete regions (e.g., the MI, BZ, and remote regions) with each having a homogeneous myocardial material property, we assumed a functional relation between the DE-MR image pixel intensity and myocardial stiffness and contractility—we considered a linear variation of material properties as a function of DE-MR image pixel intensity, which is known to improve the accuracy of the model's response. The finite element model was then calibrated using measurements obtained from the same patient—namely, 3D strain measurements—using complementary spatial modulation of magnetization magnetic resonance (CSPAMM-MR) images. This led to an average circumferential strain error of 8.9% across all American Heart Association (AHA) segments. We demonstrate the utility of our method for quantifying smooth regional variations in myocardial contractility using cardiac DE-MR and CSPAMM-MR images acquired from a 78-yr-old woman who experienced an MI approximately 1 yr prior. We found a remote myocardial diastolic stiffness of C0¯=0.102 kPa, and a remote myocardial contractility of Tmax¯=146.9 kPa, which are both in the range of previously published normal human values. Moreover, we found a normalized pixel intensity range of 30% for the BZ, which is consistent with the literature. Based on these regional myocardial material properties, we used our finite element model to compute patient-specific diastolic and systolic LV myofiber stress distributions, which cannot be measured directly. One of the main driving forces for adverse LV remodeling is assumed to be an abnormally high level of ventricular wall stress, and many existing and new treatments for heart failure fundamentally attempt to normalize LV wall stress. Thus, our noninvasive method for estimating smooth regional variations in myocardial contractility should be valuable for optimizing new surgical or medical strategies to limit the chronic evolution from infarction to heart failure.

Cervical 1-2 Posterior Instrumented Fusion Utilizing Computer-Assisted Navigation With Harvest of Rib Strut Autograft: 2-Dimensional Operative Video

2021 ◽  
Author(s):  
Timothy J Yee ◽  
Michael J Strong ◽  
Matthew S Willsey ◽  
Mark E Oppenlander
Keyword(s):  
Surface Area ◽  
Odontoid Process ◽  
Odontoid Fracture ◽  
Patient Specific ◽  
Computer Assisted ◽  
Type Ii ◽  
Instrumented Fusion ◽  
Assisted Navigation ◽  
Patient Consent ◽  
Posterior Instrumented Fusion

Abstract Nonunion of a type II odontoid fracture after the placement of an anterior odontoid screw can occur despite careful patient selection. Countervailing factors to successful fusion include the vascular watershed zone between the odontoid process and body of C2 as well as the relatively low surface area available for fusion. Patient-specific factors include osteoporosis, advanced age, and poor fracture fragment apposition. Cervical 1-2 posterior instrumented fusion is indicated for symptomatic nonunion. The technique leverages the larger posterolateral surface area for fusion and does not rely on bony growth in a watershed zone. Although loss of up to half of cervical rotation is expected after C1-2 arthrodesis, this may be better tolerated in the elderly, who may have lower physical demands than younger patients. In this video, we discuss the case of a 75-yr-old woman presenting with intractable mechanical cervicalgia 7 mo after sustaining a type II odontoid fracture and undergoing anterior odontoid screw placement at an outside institution. Cervical radiography and computed tomography exhibited haloing around the screw and nonunion across the fracture. We demonstrate C1-2 posterior instrumented fusion with Goel-Harms technique (C1 lateral mass and C2 pedicle screws), utilizing computer-assisted navigation, and modified Sonntag technique with rib strut autograft.  Posterior C1-2-instrumented fusion with rib strut autograft is an essential technique in the spine surgeon's armamentarium for the management of C1-2 instability, which can be a sequela of type II dens fracture. Detailed video demonstration has not been published to date.  Appropriate patient consent was obtained.

scholarly journals Size Effects in Finite Element Modelling of 3D Printed Bone Scaffolds Using Hydroxyapatite PEOT/PBT Composites

Mathematics ◽  
2021 ◽  
Vol 9 (15) ◽  
pp. 1746
Author(s):  
Iñigo Calderon-Uriszar-Aldaca ◽  
Sergio Perez ◽  
Ravi Sinha ◽  
Maria Camara-Torres ◽  
Sara Villanueva ◽  
...  
Keyword(s):  
Finite Element ◽  
Additive Manufacturing ◽  
Tissue Regeneration ◽  
Finite Element Modelling ◽  
Bulk Material ◽  
Bone Tissue Regeneration ◽  
Patient Specific ◽  
Design Factor ◽  
Element Modelling ◽  
Uncertainty Sources

Additive manufacturing (AM) of scaffolds enables the fabrication of customized patient-specific implants for tissue regeneration. Scaffold customization does not involve only the macroscale shape of the final implant, but also their microscopic pore geometry and material properties, which are dependent on optimizable topology. A good match between the experimental data of AM scaffolds and the models is obtained when there is just a few millimetres at least in one direction. Here, we describe a methodology to perform finite element modelling on AM scaffolds for bone tissue regeneration with clinically relevant dimensions (i.e., volume > 1 cm3). The simulation used an equivalent cubic eight node finite elements mesh, and the materials properties were derived both empirically and numerically, from bulk material direct testing and simulated tests on scaffolds. The experimental validation was performed using poly(ethylene oxide terephthalate)-poly(butylene terephthalate) (PEOT/PBT) copolymers and 45 wt% nano hydroxyapatite fillers composites. By applying this methodology on three separate scaffold architectures with volumes larger than 1 cm3, the simulations overestimated the scaffold performance, resulting in 150–290% stiffer than average values obtained in the validation tests. The results mismatch highlighted the relevance of the lack of printing accuracy that is characteristic of the additive manufacturing process. Accordingly, a sensitivity analysis was performed on nine detected uncertainty sources, studying their influence. After the definition of acceptable execution tolerances and reliability levels, a design factor was defined to calibrate the methodology under expectable and conservative scenarios.

scholarly journals Gravity determines the direction of nerve roots sedimentation in the lumbar spinal canal

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Jun Yang ◽  
Zhiyun Feng ◽  
Nian Chen ◽  
Zhenhua Hong ◽  
Yongyu Zheng ◽  
...  
Keyword(s):  
Lumbar Spine ◽  
Mr Imaging ◽  
Spinal Canal ◽  
Ventral Side ◽  
Lateral Position ◽  
Dorsal Side ◽  
Mr Images ◽  
Nerve Roots ◽  
Cross Sectional ◽  
Dural Sac

Abstract Objectives To investigate the role of gravity in the sedimentation of lumbar spine nerve roots using magnetic resonance (MR) imaging of various body positions. Methods A total of 56 patients, who suffered from back pain and underwent conventional supine lumbar spine MR imaging, were selected from sanmen hospital database. All the patients were called back to our hospital to perform MR imaging in prone position or lateral position. Furthermore, the sedimentation sign (SedSign) was determined based on the suspension of the nerve roots in the dural sac on cross-sectional MR images, and 31 cases were rated as positive and another 25 cases were negative. Results The mean age of negative SedSign group was significantly younger than that of positive SedSign group (51.7 ± 8.7 vs 68.4 ± 10.5, P < 0.05). The constitutions of clinical diagnosis were significantly different between patients with a positive SedSign and those with a negative SedSign (P < 0.001). Overall, nerve roots of the vast majority of patients (48/56, 85.7%) subsided to the ventral side of the dural sac on the prone MR images, although that of 8 (14.3%) patients remain stay in the dorsal side of dural sac. Nerve roots of only one patient with negative SedSign did not settle to the ventral dural sac, while this phenomenon occurred in 7 patients in positive SedSign group (4% vs 22.6%, P < 0.001). In addition, the nerve roots of all the five patients subsided to the left side of dural sac on lateral position MR images. Conclusions The nerve roots sedimentation followed the direction of gravity. Positive SedSign may be a MR sign of lumbar pathology involved the spinal canal.

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