Study of MRI Susceptibility Artifacts for Nanomedical Applications

2010 ◽  
Vol 1 (4) ◽  
Author(s):  
Tim Wortmann ◽  
Christian Dahmen ◽  
Sergej Fatikow
Keyword(s):  
Scaling Laws ◽  
Position Control ◽  
Superparamagnetic Nanoparticles ◽  
Susceptibility Artifacts ◽  
Imaging Parameters ◽  
Object Locations ◽  
Gradient Fields ◽  
Mri Scans ◽  
3D Scans ◽  
The Impact

This article deals with the exploitation of magnetic susceptibility artifacts in magnetic resonance imaging (MRI) for the recognition of metallic delivery capsules. The targeted application is a closed-loop position control of magnetic objects implemented using the components of a clinical MRI scanner. Actuation can be performed by switching the magnetic gradient fields, whereas object locations are detected by an analysis of the MRI scans. A comprehensive investigation of susceptibility artifacts with a total number of 108 experimental setups has been performed in order to study scaling laws and the impact of object properties and imaging parameters. In addition to solid metal objects, a suspension of superparamagnetic nanoparticles has been examined. All 3D scans have been segmented automatically for artifact quantification and location determination. Analysis showed a characteristic shape for all three base types of sequences, which is invariant to the magnetic object shape and material. Imaging parameters such as echo time and flip angle have a moderate impact on the artifact volume but do not modify the characteristic artifact shape. The nanoparticle agglomerates produce imaging artifacts similar to the solid samples. Based on the results, a two-stage recognition/tracking procedure is proposed.

scholarly journals Robust Position Control of a Two-Sided 1-DoF Impacting Mechanical Oscillator Subject to an External Persistent Disturbance by Means of a State-Feedback Controller

Complexity ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Firas Turki ◽  
Hassène Gritli ◽  
Safya Belghith
Keyword(s):  
State Feedback ◽  
Position Control ◽  
External Disturbance ◽  
Feedback Controller ◽  
Linear Matrix ◽  
Stability Conditions ◽  
Mechanical Oscillator ◽  
Impact Oscillator ◽  
State Feedback Controller ◽  
The Impact

This paper proposes a state-feedback controller using the linear matrix inequality (LMI) approach for the robust position control of a 1-DoF, periodically forced, impact mechanical oscillator subject to asymmetric two-sided rigid end-stops. The periodic forcing input is considered as a persistent external disturbance. The motion of the impacting oscillator is modeled by an impulsive hybrid dynamics. Thus, the control problem of the impact oscillator is recast as a problem of the robust control of such disturbed impulsive hybrid system. To synthesize stability conditions, we introduce the S-procedure and the Finsler lemmas by only considering the region within which the state evolves. We show that the stability conditions are first expressed in terms of bilinear matrix inequalities (BMIs). Using some technical lemmas, we convert these BMIs into LMIs. Finally, some numerical results and simulations are given. We show the effectiveness of the designed state-feedback controller in the robust stabilization of the position of the impact mechanical oscillator under the disturbance.

scholarly journals Access to MRI for patients with cardiac pacemakers and implantable cardioverter defibrillators

Open Heart ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. e001598
Author(s):  
Christopher Pieri ◽  
Anish Bhuva ◽  
Russell Moralee ◽  
Aderonke Abiodun ◽  
Deepa Gopalan ◽  
...  
Keyword(s):  
Supply And Demand ◽  
Complication Rates ◽  
Similar Data ◽  
Implantable Cardioverter Defibrillators ◽  
Cardiac Pacemakers ◽  
Survey Tool ◽  
Mr Conditional ◽  
Mri Scans ◽  
Implantation Rates ◽  
The Impact

ObjectiveTo determine provision of MRI for patients with cardiac implantable electronic devices (CIEDs; pacemakers and defibrillators) in England, to understand regional variation and assess the impact of guideline changes.MethodsRetrospective data related to MRI scans performed in patients with CIED over the preceding 12 months was collected using a structured survey tool distributed to every National Health Service Trust MRI unit in England. Data were compared with similar data from 2014/2015 and with demand (estimated from local CIED implantation rates and regional population data by sustainability and transformation partnerships (STPs)).ResultsResponses were received from 212 of 223 (95%) hospitals in England. 112 (53%) MRI units’ scan patients with MR-conditional CIEDs (10% also scan non-MR conditional devices), compared with 46% of sites in 2014/2015. Total annual scan volume increased over fourfold between 2014 and 2019 (1090 to 4896 scans). There was widespread geographical variation, with five STPs (total population >3·5 million representing approximately 25 000 patients with CIED) with no local provision. There was no correlation between local demand (CIED implantation rates) and MRI provision (scan volume). Complication rates were extremely low with three events nationally in 12 months (0·06% CIED–MRI scans).ConclusionsProvision of MRI for patients with CIEDs in England increased over fourfold in 4 years, but an estimated 10-fold care gap remains. Almost half of hospitals and 1 in 10 STPs have no service, with no relationship between local supply and demand. Availability of MRI for patients with non-MR conditional devices, although demonstrably safe, remains limited.

scholarly journals The impact of the variation of imaging parameters on the robustness of Computed Tomography radiomic features: A review

2021 ◽  
Vol 133 ◽  
pp. 104400
Author(s):  
Reza Reiazi ◽  
Engy Abbas ◽  
Petra Famiyeh ◽  
Aria Rezaie ◽  
Jennifer Y.Y. Kwan ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Imaging Parameters ◽  
The Impact

Splash formation by spherical drops

2001 ◽  
Vol 427 ◽  
pp. 73-105 ◽  
Author(s):  
LIOW JONG LENG
Keyword(s):  
High Resolution ◽  
Quantitative Data ◽  
Water Surface ◽  
High Speed ◽  
Scaling Laws ◽  
Capillary Wave ◽  
Water Drop ◽  
Qualitative And Quantitative ◽  
High Resolution Images ◽  
The Impact

The impact of a spherical water drop onto a water surface has been studied experimentally with the aid of a 35 mm drum camera giving high-resolution images that provided qualitative and quantitative data on the phenomena. Scaling laws for the time to reach maximum cavity sizes have been derived and provide a good fit to the experimental results. Transitions between the regimes for coalescence-only, the formation of a high-speed jet and bubble entrapment have been delineated. The high-speed jet was found to occur without bubble entrapment. This was caused by the rapid retraction of the trough formed by a capillary wave converging to the centre of the cavity base. The converging capillary wave has a profile similar to a Crapper wave. A plot showing the different regimes of cavity and impact drop behaviour in the Weber–Froude number-plane has been constructed for Fr and We less than 1000.

Adaptive Motion and Force Control of Robots Performing a Complete Task

1999 ◽  
Author(s):  
Prabhakar R. Pagilla ◽  
Biao Yu
Keyword(s):  
Force Control ◽  
Position Control ◽  
Active Phase ◽  
Free Motion ◽  
Constrained Motion ◽  
Control Laws ◽  
Adaptive Motion ◽  
Inactive Phase ◽  
The Impact ◽  
Three Phases

Abstract In this work, we consider adaptive motion and force control of a robot performing a complete task. By a complete task we mean that the robot desired task contains both free motion and constrained motion. Further, we also consider transition from free motion to constrained motion. We divide the motion of the robot into three phases: (i) inactive phase, where the robot is in free motion, (ii) transition phase, where the transition from free motion to constrained motion takes place, and (iii) active phase, where the robot is in constrained motion with simultaneous force and position control. Uncertainty of the constraint results in the impact of robot with the constraint surface when transition from free motion to constrained motion. We design stable control laws for the three phases that results in an efficient algorithm for robots performing a complete task. Extensive experiments are conducted to show the validity of the proposed control designs.

THUR 198 Safe monitoring of natalizumab therapy in multiple sclerosis

2018 ◽  
Vol 89 (10) ◽  
pp. A29.1-A29
Author(s):  
Hosty J ◽  
Kass-Iliyya L ◽  
Bell S ◽  
Barker L ◽  
Packwood S ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Jc Virus ◽  
Safety Monitoring ◽  
Brain Infection ◽  
Audit Data ◽  
Relapsing Remitting ◽  
Mri Scans ◽  
Specialist Nurses ◽  
Relapsing Remitting Multiple Sclerosis ◽  
The Impact

Natalizumab is one of the most effective therapies for relapsing-remitting Multiple Sclerosis. One complication is Progressive Multifocal Leucoencephalopathy (PML), a viral brain infection in patients already infected with JC virus. Monitoring of neurological symptoms, JC virus serology and regular brain imaging are required to ensure safe use of this therapy. Local audit data from 2015 indicated poor compliance with safety monitoring, with less than 25% of patients undergoing required investigations within the recommended time intervals. Subsequently a protocol was implemented to improve monitoring, with specialist nurses coordinating the requests for MRI scans and arranging JC virus serology, the frequency of which was determined according to the JC virus index. The records of all patients receiving Natalizumab at the centre were audited to assess the impact of this protocol (n=155). 99.2% of patients were appropriately tested for JC virus and 95.3% were imaged within the recommended interval. Additional work with the informatics and virology team ensured serology results became more easily accessible. The use of a standardised nurse-led operating procedure has resulted in marked improvement in the safety monitoring of Natalizumab.

scholarly journals The impact of error frequency on errorless and errorful learning of object locations using a novel paradigm

Memory ◽  
2019 ◽  
Vol 27 (10) ◽  
pp. 1371-1380 ◽  
Author(s):  
Inge Scheper ◽  
Ellen R. A. de Bruijn ◽  
Dirk Bertens ◽  
Roy P. C. Kessels ◽  
Inti A. Brazil
Keyword(s):  
Error Frequency ◽  
Object Locations ◽  
The Impact

Should frequent MRI monitoring be performed in natalizumab-treated MS patients? A contribution to a recent debate

2019 ◽  
Vol 26 (10) ◽  
pp. 1227-1236 ◽  
Author(s):  
Cristina Scarpazza ◽  
Alessio Signori ◽  
Mirco Cosottini ◽  
Maria Pia Sormani ◽  
Simonetta Gerevini ◽  
...  
Keyword(s):  
Clinical Outcome ◽  
Small Volume ◽  
Brain Magnetic Resonance Imaging ◽  
Available N ◽  
Disability Status ◽  
Mri Scans ◽  
Recent Debate ◽  
Magnetic Resonance Imaging Mri ◽  
Mri Surveillance ◽  
The Impact

Background: Brain magnetic resonance imaging (MRI) is the most effective surveillance tool for the detection of asymptomatic progressive multifocal leukoencephalopathy (PML). However, the optimal frequency for routine MRI surveillance is under-investigated. Objective: To understand whether, upon their first MRI appearance, PML lesions present a difference in volume when comparing patients who frequently underwent MRI surveillance (3/4 months) with those who were assessed at longer intervals (6/12 months) and to understand the impact of the volume of lesions on clinical outcome. Methods: The data of patients included in the Italian PML cohort were retrospectively analysed. Patients who had all the pre-diagnostic MRI scans available ( n = 37) were included. The volume of PML lesion was calculated by manually outlining the PML lesion. Results: Compared with patients who underwent MRI examination at least every 4 months, patients who were assessed less frequently had a lesion of significantly higher volume (median: 2567 (883–3583) vs. 664 mm3 (392–963) p = 0.006) and suffered a higher rate of disability (median: 2.25 expanded disability status scale points (–2.5 to 8) vs. 0.5 (–1 to 2.5) p = 0.004). Conclusion: The positive clinical outcome of patients undergoing frequent MRI surveillance and the small volume of the PML lesion upon first appearance justify a frequent surveillance using MRI in patients at high risk of PML.

Impact of extent of resection of glioblastoma multiforme (GBM) in the era of chemoradiation

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. e13029-e13029
Author(s):  
B. J. Slotman ◽  
W. S. Eppinga ◽  
J. C. Reijneveld ◽  
D. P. Noske ◽  
J. Buter ◽  
...  
Keyword(s):  
Residual Tumor ◽  
Extent Of Resection ◽  
Partial Resection ◽  
Recurrence Time ◽  
Significant Prognostic Factor ◽  
Prognostic Impact ◽  
Total Resection ◽  
Mri Scans ◽  
Major Resection ◽  
The Impact

e13029 Background: Controversy remains regarding the impact of the extent of resection (EOR) on survival in patients with GBM (Sanai 2008). The main reason for this is the fact that most studies were based on the surgeon's estimate of the EOR, which is known to be unreliable, rather than early postoperative MRI scans (po-MRI). Data for the current standard of postoperative chemo-radiotherapy (CTRT) have recently been reported, but suffer from the same limitation (Gorlia 2008). We studied the prognostic impact of the EOR using early (<72 hours) po-MRI scans in a cohort of GBM patients treated with CTRT in a single center. Methods: The results of 48 consecutive patients (35 male, 13 female; age 18–73 yrs) treated with surgery, followed by concurrent CTRT (60 Gy plus temozolomide) and adjuvant temozolomide were assessed with respect to survival and relapse patterns. EOR was determined by both the surgeon's estimation and early po-MRI scans that were available in all but two patients. EOR was categorized as biopsy (N = 3), partial resection (N = 24), major resection (N = 11; i.e., total resection according to the surgeon's report, but residual tumor on po-MRI), and total resection (N = 10; i.e. no residual tumor on po-MRI). Results: Median overall survival of the entire cohort was 18.9 months, and EOR was the only significant prognostic factor (p = 0.02) on multivariate analysis, which also included age, gender, performance, and radiotherapy target volume. 2-year survival rates improved significantly with increasing EOR, with 0%, 18.9%, 68.6%, and 100% for biopsy, partial-, major-, and total resection, respectively. In-field progression was the predominant pattern of failure in 27 out of 30 patients (90%) with a recurrence. Time to neurological progression (TNP) was significantly correlated with EOR (p < 0.001). Median TNP was 3.0 months for biopsy, 7.0 months for partial resection, 20.5 months for major resection, and was not reached for total resection. Conclusions: With the use of more effective local therapy in the form of surgery and CTRT, the prognostic impact of the EOR on survival appears to be higher than previously reported. This should be accounted for in future trials. No significant financial relationships to disclose.

Can CRM status on MRI predict survival in locally advanced rectal cancers: Experience from the Indian subcontinent.

2017 ◽  
Vol 35 (15_suppl) ◽  
pp. e15167-e15167
Author(s):  
Jay Rashmi Anam ◽  
Mihir Chandarana ◽  
Supreeta Arya ◽  
Ashwin Luis Desouza ◽  
Vikas S. Ostwal ◽  
...  
Keyword(s):  
Overall Survival ◽  
Local Recurrence ◽  
Predictive Value ◽  
Locally Advanced ◽  
Disease Free Survival ◽  
Free Survival ◽  
Mri Scans ◽  
Rectal Cancers ◽  
The Impact ◽  
Disease Free

e15167 Background: Neoadjuvant chemoradiation has become the standard approach for treatment of locally advanced rectal cancers. Magnetic Resonence Imaging (MRI) is the staging modality of choice in rectal carcinoma. Recent reports have studied the impact of MRI on local recurrence and survival both in treatment naïve and post treatment settings Methods: A retrospective analysis of prospective database was performed over a period of 1 year. All pretreatment patients with carcinoma of rectum were included in the study. The status of CRM on MRI was compared to that on the histopathology and as a predictor of recurrence and survival. For analysis, the MRI scans done for patients at presentation were labeled as MRIT. This included all patients irrespective of further treatment received. Patients who were treated with NACTRT had two MRI scans. The MRI at presentation in this subset of patients was labeled as MRI1 and the reassessment MRI after NACTRT was labeled as MRI2. Thus, MRI1 represented a subset of MRIT with locally advanced tumors treated with NACTRT. All the sets of MRI scans were analyzed separately for prediction of CRM involvement and for their effect on local recurrence and survival rates. Results: 221 patients were included with a median follow-up 30 months. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of MRIT, MRI1 and MRI2 to predict CRM status were 50%, 62.3%, 96.5%, 5.6% and 61.8%, 50%, 55%, 95%, 6% and 54.7% and 77.8%, 63.7%, 98%, 11%, 64.5% respectively. On multivariate analysis pathological positive margins alone predicted a poor overall survival (OS) whereas involved CRM on pathology and pretreatment MRI predicted poorer disease free survival and OS Conclusions: CRM status on pathology remains the most important prognostic factor to impact overall survival, disease free survival and local recurrence. CRM status on MRI at presentation alone has significant impact on disease free survival and local recurrence. Although MRI done after neoadjuvant treatment may not predict survival, it has a role in helping modify the surgical approach with a goal to achieve a negative CRM on pathology.

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