The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jens Frahm - One of the best experts on this subject based on the ideXlab platform.
-
iceberg or cut off how adults who stutter articulate fluent sounding utterances
bioRxiv, 2020Co-Authors: Andreas Leha, Arun A. Joseph, Jens Frahm, Walter Paulus, Susanne Dickhut, Annika Primassin, Alexandra Korzeczek, Martin SommerAbstract:Whether fluent-sounding utterances of adults who stutter (AWS) are normally articulated is unclear. We asked 15 AWS and 17 matched adults who do not stutter (ANS) to utter the pseudoword "natscheitideut" 15 times in a 3 T MRI scanner while recording Real-Time MRI videos at 55 frames per per second in a mid-sagittal plane. All stuttered or otherwise dysfluent runs were discarded. We used sophisticated analyses to model the movement of the tip of the tongue, lips and velum. We observed reproducible movement patterns of the inner and outer articulators which were similar in both groups. Speech duration was similar in both groups and decreased over repetitions, more so in ANS than in AWS. The variability of the movement patterns of tongue, lips and velum decreased over repetitions. The extent of variability decrease was similar in both groups. Across all participants, this repetition effect on movement variability for the lips and the tip of the tongue was less pronounced in severely as compared to mildly stuttering individuals. We conclude that there is no major difference in the movement patterns of a fluent-sounding utterance in both groups. This encourages studies looking at state rather than trait markers of speech dysfluency.
-
analyzing speech in both time and space generalized additive mixed models can uncover systematic patterns of variation in vocal tract shape in real time MRI
Laboratory Phonology, 2020Co-Authors: Christopher Carignan, Arun A. Joseph, Jens Frahm, Dirk Voit, Phil Hoole, Esther Kunay, Marianne Pouplier, Jonathan HarringtonAbstract:We present a method of using generalized additive mixed models (GAMMs) to analyze midsagittal vocal tract data obtained from Real-Time magnetic resonance imaging (rt-MRI) video of speech production. Applied to rt-MRI data, GAMMs allow for observation of factor effects on vocal tract shape throughout two key dimensions: time (vocal tract change over the temporal course of a speech segment) and space (location of change within the vocal tract). Examples of this method are provided for rt-MRI data collected at a temporal resolution of 20 ms and a spatial resolution of 1.41 mm, for 36 native speakers of German. The rt-MRI data were quantified as 28-point semi-polar-grid aperture functions. Three test cases are provided as a way of observing vocal tract differences between: (1) /aː/ and /iː/, (2) /aː/ and /aɪ/, and (3) accentuated and unstressed /aː/. The results for each GAMM are independently validated using functional linear mixed models (FLMMs) constructed from data obtained at 20% and 80% of the vowel interval. In each case, the two methods yield similar results. In light of the method similarities, we propose that GAMMs are a robust, powerful, and interpretable method of simultaneously analyzing both temporal and spatial effects in rt-MRI video of speech.
-
real time MRI for dynamic assessment of gastroesophageal reflux disease comparison to ph metry and impedance
European Journal of Radiology, 2020Co-Authors: Ali Seif Amir Hosseini, Martin Uecker, Johannes Uhlig, Nina Gliem, E Wedi, Volker Ellenrieder, Michael Ghadimi, Ulrike Streit, Saheeb Ahmed, Jens FrahmAbstract:Abstract Purpose To evaluate the diagnostic potential of Real-Time MRI for dynamic assessment of gastroesophageal reflux in patients with GERD (gastroesophageal reflux disease)-like symptoms compared to pH-metry and impedance. Methods Patients who underwent Real-Time MRI and pH-metry between 2015-2018 were included in this retrospective study. Real-Time MRI at 3 Tesla was achieved by undersampled radial FLASH acquisitions with iterative image reconstruction by NLINV. Real-Time MRI visualized transit of pineapple juice through the gastroesophageal junction and during Valsalva maneuver. MRI results were compared to 24 -h pH-metry to assess acidic reflux (following Lyon Consensus guidelines) and to impedance to assess non-acidic reflux. A standard 2 × 2 table was chosen to calculate diagnostic performance. Results 91/93 eligible patients fulfilled inclusion criteria (male n = 49; female n = 42; median age 55 y). All MRI studies were successfully completed without adverse events at a mean examination time of 15 minutes. On Real-Time MRI, reflux was evident in 60 patients (66%). pH-metry revealed reflux in 41 patients (45%), and impedance in 54 patients (59%). Compared to pH-metry and impedance, Real-Time MRI sensitivity was 0.78 (95% CI: 0.66-0.87), specificity 0.67 (95% CI: 0.45-0.84) and PPV 0.87 (95% CI: 0.75-0.94). Conclusion Real-Time MRI is an imaging method for assessment of gastroesophageal reflux in patients with GERD-like symptoms. Considering its high positive predictive value, Real-Time MRI can accurately identify patients in which further invasive testing with pH-metry and impedance might be considered.
-
Tongue involvement in embouchure dystonia: new piloting results using Real-Time MRI of trumpet players
Journal of Clinical Movement Disorders, 2019Co-Authors: Soenke J. Hellwig, Arun A. Joseph, Jens Frahm, Dirk Voit, Peter W. Iltis, Erwin Schoonderwaldt, Eckart AltenmüllerAbstract:Background The embouchure of trumpet players is of utmost importance for tone production and quality of playing. It requires skilled coordination of lips, facial muscles, tongue, oral cavity, larynx and breathing and has to be maintained by steady practice. In rare cases, embouchure dystonia (EmD), a highly task specific movement disorder, may cause deterioration of sound quality and reduced control of tongue and lip movements. In order to better understand the pathophysiology of this movement disorder, we use Real-Time MRI to analyse differences in tongue movements between healthy trumpet players and professional players with embouchure dystonia. Methods Real-Time MRI videos (with sound recording) were acquired at 55 frames per second, while 10 healthy subjects and 4 patients with EmD performed a defined set of exercises on an MRI-compatible trumpet inside a 3 Tesla MRI system. To allow for a comparison of tongue movements between players, temporal changes of MRI signal intensities were analysed along 7 standardized positions of the tongue using a customised MATLAB toolkit. Detailed results of movements within the oral cavity during performance of an ascending slurred 11-note harmonic series are presented. Results Playing trumpet in the higher register requires a very precise and stable narrowing of the free oral cavity. For this purpose the anterior section of the tongue is used as a valve in order to speed up airflow in a controlled manner. Conversely, the posterior part of the tongue is much less involved in the regulation of air speed. The results further demonstrate that healthy trumpet players control movements of the tongue rather precisely and stable during a sustained tone, whereas trumpet players with EmD exhibit much higher variability in tongue movements. Conclusion Control of the anterior tongue in trumpet playing emerges as a critical feature for regulating air speed and, ultimately, achieving a high-quality performance. In EmD the observation of less coordinated tongue movements suggests the presence of compensatory patterns in an attempt to regulate (or correct) pitch. Increased variability of the anterior tongue could be an objective sign of dystonia that has to be examined in further studies and extended to other brass instruments and may be also a potential target for therapy options.
-
spinal csf flow in response to forced thoracic and abdominal respiration
Fluids and Barriers of the CNS, 2019Co-Authors: Gokmen Aktas, Arun A. Joseph, Klaus-dietmar Merboldt, Jens Frahm, Hans-christoph Ludwig, Jost M Kollmeier, Jutta Gartner, Steffi DrehakulaczewskiAbstract:Respiration-induced pressure changes represent a powerful driving force of CSF dynamics as previously demonstrated using flow-sensitive Real-Time magnetic resonance imaging (MRI). The purpose of the present study was to elucidate the sensitivity of CSF flow along the spinal canal to forced thoracic versus abdominal respiration. Eighteen subjects without known illness were studied using Real-Time phase-contrast flow MRI at 3 T in the aqueduct and along the spinal canal at levels C3, Th1, Th8 and L3. Subjects performed a protocol of forced breathing comprising four cycles of 2.5 s inspiration and 2.5 s expiration. The quantitative results for spinal CSF flow rates and volumes confirm previous findings of an upward movement during forced inspiration and reversed downward flow during subsequent exhalation—for both breathing types. However, the effects were more pronounced for abdominal than for thoracic breathing, in particular at spinal levels Th8 and L3. In general, CSF net flow volumes were very similar for both breathing conditions pointing upwards in all locations. Spinal CSF dynamics are sensitive to varying respiratory performances. The different CSF flow volumes in response to deep thoracic versus abdominal breathing reflect instantaneous adjustments of intrathoracic and intraabdominal pressure, respectively. Real-Time MRI access to CSF flow in response to defined respiration patterns will be of clinical importance for patients with disturbed CSF circulation like hydrocephalus, pseudotumor cerebri and others.
Kanishka Ratnayaka - One of the best experts on this subject based on the ideXlab platform.
-
transcatheter myocardial needle chemoablation during real time magnetic resonance imaging a new approach to ablation therapy for rhythm disorders
Circulation-arrhythmia and Electrophysiology, 2016Co-Authors: Toby Rogers, Anthony Z. Faranesh, William H Schenke, Srijoy Mahapatra, Steven Kim, Michael Eckhaus, Jonathan R Mazal, Adrienne E Campbellwashburn, Merdim Sonmez, Kanishka RatnayakaAbstract:Background— Radiofrequency ablation for ventricular arrhythmias is limited by inability to visualize tissue destruction, by reversible conduction block resulting from edema surrounding lesions, and by insufficient lesion depth. We hypothesized that transcatheter needle injection of caustic agents doped with gadolinium contrast under Real-Time magnetic resonance imaging (MRI) could achieve deep, targeted, and irreversible myocardial ablation, which would be immediately visible. Methods and Results— Under Real-Time MRI guidance, ethanol or acetic acid was injected into the myocardium of 8 swine using MRI-conspicuous needle catheters. Chemoablation lesions had identical geometry by in vivo and ex vivo MRI and histopathology, both immediately and after 12 (7–17) days. Ethanol caused stellate lesions with patchy areas of normal myocardium, whereas acetic acid caused homogeneous circumscribed lesions of irreversible necrosis. Ischemic cardiomyopathy was created in 10 additional swine by subselective transcoronary ethanol administration into noncontiguous territories. After 12 (8–15) days, Real-Time MRI–guided chemoablation—with 2 to 5 injections to create a linear lesion—successfully eliminated the isthmus and local abnormal voltage activities. Conclusions— Real-Time MRI–guided chemoablation with acetic acid enabled the intended arrhythmic substrate, whether deep or superficial, to be visualized immediately and ablated irreversibly. In an animal model of ischemic cardiomyopathy, obliteration of a conductive isthmus both anatomically and functionally and abolition of local abnormal voltage activities in areas of heterogeneous scar were feasible. This represents the first report of MRI-guided myocardial chemoablation, an approach that could improve the efficacy of arrhythmic substrate ablation in the thick ventricular myocardium.
-
real time MRI guided right heart catheterization in adults using passive catheters
European Heart Journal, 2013Co-Authors: Kanishka Ratnayaka, Anthony Z. Faranesh, Michael S Hansen, Annette M Stine, Majdi Halabi, Israel M Barbash, William H Schenke, Victor J Wright, Laurie P Grant, Peter KellmanAbstract:We performed X-ray and MRI-guided transfemoral right heart catheterization in consecutive patients undergoing clinical cardiac catheterization. We sampled both cavae and both pulmonary arteries. We compared success rate, time to perform key steps, and catheter visibility among X-ray and MRI procedures using air-filled or gadolinium- filled balloon-tipped catheters. Sixteen subjects (four with shunt, nine with coronary artery disease, three with other) underwent paired X-ray and MRI catheterization. Complete guidewire-free catheterization was possible in 15 of 16 under both. MRI using gadolinium-filled balloons was at least as successful as X-ray in all procedure steps, more successful than MRI using air-filled balloons, and better than both in entering the left pulmonary artery. Total catheterization time and individual procedure steps required approximately the same amount of time irrespective of image guidance modality. Catheter conspicuity was best under X-ray and next-best using gadolin- ium-filled MRI balloons. Conclusion In this early experience, comprehensive transfemoral right heart catheterization appears feasible using only MRI for imaging guidance. Gadolinium-filled balloon catheters were more conspicuous than air-filled ones. Further workflow and device enhancement are necessary for clinical adoption.
-
closed chest transthoracic magnetic resonance imaging guided ventricular septal defect closure in swine
Jacc-cardiovascular Interventions, 2011Co-Authors: Kanishka Ratnayaka, Anthony Z. Faranesh, Israel M Barbash, Merdim Sonmez, Christina E Saikus, Jamie A Bell, Ozgur Kocaturk, Christine Reyes, William H SchenkeAbstract:Objectives The aim of this study was to close ventricular septal defects (VSDs) directly through the chest wall using magnetic resonance imaging (MRI) guidance, without cardiopulmonary bypass, sternotomy, or radiation exposure. Background Surgical, percutaneous, and hybrid management of VSD each have limitations and known morbidity. Methods Percutaneous muscular VSDs were created in 10 naive Yorkshire swine using a transjugular laser catheter. Under Real-Time MRI guidance, a direct transthoracic vascular access sheath was introduced through the chest into the heart along a trajectory suitable for VSD access and closure. Through this transthoracic sheath, muscular VSDs were occluded using a commercial nitinol device. Finally, the right ventricular free wall was closed using a commercial collagen plug intended for arterial closure. Results Anterior, posterior, and mid-muscular VSDs (6.8 ± 1.8 mm) were created. VSDs were closed successfully in all animals. The transthoracic access sheath was displaced in 2, both fatal. Thereafter, we tested an intracameral retention sheath to prevent this complication. Right ventricular access ports were closed successfully in all, and after as many as 30 days, healed successfully. Conclusions Real-Time MRI guidance allowed closed-chest transthoracic perventricular muscular VSD closure in a clinically meaningful animal model. Once applied to patients, this approach may avoid traditional surgical, percutaneous, or open-chest transcatheter (“hybrid”) risks.
Peter Kellman - One of the best experts on this subject based on the ideXlab platform.
-
real time MRI guided right heart catheterization in adults using passive catheters
European Heart Journal, 2013Co-Authors: Kanishka Ratnayaka, Anthony Z. Faranesh, Michael S Hansen, Annette M Stine, Majdi Halabi, Israel M Barbash, William H Schenke, Victor J Wright, Laurie P Grant, Peter KellmanAbstract:We performed X-ray and MRI-guided transfemoral right heart catheterization in consecutive patients undergoing clinical cardiac catheterization. We sampled both cavae and both pulmonary arteries. We compared success rate, time to perform key steps, and catheter visibility among X-ray and MRI procedures using air-filled or gadolinium- filled balloon-tipped catheters. Sixteen subjects (four with shunt, nine with coronary artery disease, three with other) underwent paired X-ray and MRI catheterization. Complete guidewire-free catheterization was possible in 15 of 16 under both. MRI using gadolinium-filled balloons was at least as successful as X-ray in all procedure steps, more successful than MRI using air-filled balloons, and better than both in entering the left pulmonary artery. Total catheterization time and individual procedure steps required approximately the same amount of time irrespective of image guidance modality. Catheter conspicuity was best under X-ray and next-best using gadolin- ium-filled MRI balloons. Conclusion In this early experience, comprehensive transfemoral right heart catheterization appears feasible using only MRI for imaging guidance. Gadolinium-filled balloon catheters were more conspicuous than air-filled ones. Further workflow and device enhancement are necessary for clinical adoption.
-
retrospective reconstruction of high temporal resolution cine images from real time MRI using iterative motion correction
Magnetic Resonance in Medicine, 2012Co-Authors: Michael S Hansen, Thomas Sangild Sorensen, Andrew E Arai, Peter KellmanAbstract:Cardiac function has traditionally been evaluated using breath-hold cine acquisitions. However, there is a great need for free breathing techniques in patients who have difficulty in holding their breath. Real-Time cardiac MRI is a valuable alternative to the traditional breath-hold imaging approach, but the Real-Time images are often inferior in spatial and temporal resolution. This article presents a general method for reconstruction of high spatial and temporal resolution cine images from a Real-Time acquisition acquired over multiple cardiac cycles. The method combines parallel imaging and motion correction based on nonrigid registration and can be applied to arbitrary k-space trajectories. The method is demonstrated with Real-Time Cartesian imaging and Golden Angle radial acquisitions, and the motion-corrected acquisitions are compared with raw Real-Time images and breath-hold cine acquisitions in 10 (N = 10) subjects. Acceptable image quality was obtained in all motion-corrected reconstructions, and the resulting mean image quality score was (a) Cartesian Real-Time: 2.48, (b) Golden Angle Real-Time: 1.90 (1.00-2.50), (c) Cartesian motion correction: 3.92, (d) Radial motion correction: 4.58, and (e) Breath-hold cine: 5.00. The proposed method provides a flexible way to obtain high-quality, high-resolution cine images in patients with difficulty holding their breath.
-
low latency temporal filter design for real time MRI using unfold
Magnetic Resonance in Medicine, 2000Co-Authors: Peter Kellman, Jonathan M. Sorger, Frederick H Epstein, Elliot R. McveighAbstract:To improve Real-Time control of interventional procedures such as guidance of catheters, monitoring of ablation therapy, or control of dosage during drug delivery, the image acquisition and reconstruction must be high speed and have low latency (small time delay) in processing. A number of different methods have been demonstrated which increase the speed of MR acquisition by decreasing the number of sequential phase-encodes. A design and implementation of the UNFOLD method which achieves the desired low latency with a recursive temporal filter is presented. The recursive filter design is characterized for this application and compared with more commonly used moving average filters. Experimental results demonstrate low-latency UNFOLD for two applications: 1) high-speed, Real-Time imaging of the heart to be used in conjunction with cardiac interventional procedures; and 2) the injection of drugs into muscle tissue with contrast enhancement, i.e., monitoring needle insertion and injection of a drug with contrast enhancement properties. Proof-of-concept was demonstrated by injecting a contrast agent. In both applications the UNFOLD technique was used to double the frame rate.
Dirk Voit - One of the best experts on this subject based on the ideXlab platform.
-
analyzing speech in both time and space generalized additive mixed models can uncover systematic patterns of variation in vocal tract shape in real time MRI
Laboratory Phonology, 2020Co-Authors: Christopher Carignan, Arun A. Joseph, Jens Frahm, Dirk Voit, Phil Hoole, Esther Kunay, Marianne Pouplier, Jonathan HarringtonAbstract:We present a method of using generalized additive mixed models (GAMMs) to analyze midsagittal vocal tract data obtained from Real-Time magnetic resonance imaging (rt-MRI) video of speech production. Applied to rt-MRI data, GAMMs allow for observation of factor effects on vocal tract shape throughout two key dimensions: time (vocal tract change over the temporal course of a speech segment) and space (location of change within the vocal tract). Examples of this method are provided for rt-MRI data collected at a temporal resolution of 20 ms and a spatial resolution of 1.41 mm, for 36 native speakers of German. The rt-MRI data were quantified as 28-point semi-polar-grid aperture functions. Three test cases are provided as a way of observing vocal tract differences between: (1) /aː/ and /iː/, (2) /aː/ and /aɪ/, and (3) accentuated and unstressed /aː/. The results for each GAMM are independently validated using functional linear mixed models (FLMMs) constructed from data obtained at 20% and 80% of the vowel interval. In each case, the two methods yield similar results. In light of the method similarities, we propose that GAMMs are a robust, powerful, and interpretable method of simultaneously analyzing both temporal and spatial effects in rt-MRI video of speech.
-
Tongue involvement in embouchure dystonia: new piloting results using Real-Time MRI of trumpet players
Journal of Clinical Movement Disorders, 2019Co-Authors: Soenke J. Hellwig, Arun A. Joseph, Jens Frahm, Dirk Voit, Peter W. Iltis, Erwin Schoonderwaldt, Eckart AltenmüllerAbstract:Background The embouchure of trumpet players is of utmost importance for tone production and quality of playing. It requires skilled coordination of lips, facial muscles, tongue, oral cavity, larynx and breathing and has to be maintained by steady practice. In rare cases, embouchure dystonia (EmD), a highly task specific movement disorder, may cause deterioration of sound quality and reduced control of tongue and lip movements. In order to better understand the pathophysiology of this movement disorder, we use Real-Time MRI to analyse differences in tongue movements between healthy trumpet players and professional players with embouchure dystonia. Methods Real-Time MRI videos (with sound recording) were acquired at 55 frames per second, while 10 healthy subjects and 4 patients with EmD performed a defined set of exercises on an MRI-compatible trumpet inside a 3 Tesla MRI system. To allow for a comparison of tongue movements between players, temporal changes of MRI signal intensities were analysed along 7 standardized positions of the tongue using a customised MATLAB toolkit. Detailed results of movements within the oral cavity during performance of an ascending slurred 11-note harmonic series are presented. Results Playing trumpet in the higher register requires a very precise and stable narrowing of the free oral cavity. For this purpose the anterior section of the tongue is used as a valve in order to speed up airflow in a controlled manner. Conversely, the posterior part of the tongue is much less involved in the regulation of air speed. The results further demonstrate that healthy trumpet players control movements of the tongue rather precisely and stable during a sustained tone, whereas trumpet players with EmD exhibit much higher variability in tongue movements. Conclusion Control of the anterior tongue in trumpet playing emerges as a critical feature for regulating air speed and, ultimately, achieving a high-quality performance. In EmD the observation of less coordinated tongue movements suggests the presence of compensatory patterns in an attempt to regulate (or correct) pitch. Increased variability of the anterior tongue could be an objective sign of dystonia that has to be examined in further studies and extended to other brass instruments and may be also a potential target for therapy options.
-
Hiatal hernias in patients with GERD-like symptoms: evaluation of dynamic Real-Time MRI vs endoscopy.
European Radiology, 2019Co-Authors: Ali Seif Amir Hosseini, Martin Uecker, Johannes Uhlig, E Wedi, Volker Ellenrieder, Michael Ghadimi, Ulrike Streit, Annemarie Uhlig, Thilo Sprenger, Dirk VoitAbstract:Purpose To assess the diagnostic potential of Real-Time MRI for assessment of hiatal hernias in patients with GERD-like symptoms compared to endoscopy. Material and methods One hundred eight patients with GERD-like symptoms were included in this observational cohort study between 2015 and 2017. Real-Time MRI was performed at 3.0 Tesla with temporal resolution of 40 ms, dynamically visualizing the esophageal transport of a pineapple juice bolus, its passage through the gastroesophageal junction, and functional responses during Valsalva maneuver. Hernia detection on MRI and endoscopy was calculated using contingency tables with diagnosis of hernia on either modality as reference. Results Of 108 patients, 107 underwent successful MRI without adverse events; 1 examination was aborted to inability to swallow pineapple juice in supine position. No perforation or acute bleeding occurred during endoscopy. Median examination time was 15 min. Eighty-five patients (79.4%) were diagnosed with hiatal hernia on either Real-Time MRI or endoscopy. Forty-six hernias were visible on both modalities. Seventeen hernias were evident exclusively on MRI, and 22 exclusively on endoscopy. Sixteen of the 63 MRI-detected hernias (25.4%) were detectable only during Valsalva maneuver, which were smaller compared to hernias at rest (median - 13.5 vs - 33.0 mm, p 0.99). Conclusion Real-Time MRI is a fast and safe modality for assessment of the gastroesophageal junction, without radiation exposure or administration of gadolinium-based contrast media. Although MRI and endoscopy yield comparable diagnostic accuracy, dynamic MRI sequences are able to visualize hiatal hernias that were occult on static MRI sequences or endoscopy in a relevant number of cases. Key points • Real-Time MRI is a safe and fast imaging modality for examination of the gastroesophageal junction, combining anatomical and functional information for enhanced detection of hiatal hernias. • Real-Time MRI and endoscopy yield comparably high diagnostic accuracy: Real-Time MRI visualizes hiatal hernias that were occult on endoscopy in a relevant number of patients; however, several hiatal hernias detected on endoscopy were occult on Real-Time MRI. • There is clinical potential of Real-Time MR imaging in patients with GERD-like symptoms and equivocal findings on endoscopy or pH-metry, for anatomical visualization in patients planned for surgical intervention, or those with suspected fundoplication failures.
-
real time MRI for the dynamic assessment of fundoplication failure in patients with gastroesophageal reflux disease
European Radiology, 2019Co-Authors: Ali Seif Amir Hosseini, Dirk Voit, Johannes Uhlig, Volker Ellenrieder, Michael Ghadimi, Ulrike Streit, Annemarie Uhlig, Thilo Sprenger, Alexander W Beham, Martin UeckerAbstract:To assess the diagnostic potential of dynamic Real-Time MRI for fundoplication failure in patients with persistent or recurrent GERD-like (gastroesophageal reflux disease) complaints. Twenty-two consecutive patients (male n = 11; female n = 11; median age 59 years) with recurrent or persistent GERD-like symptom after fundoplication were enrolled between 2015 and 2017. Median duration of GERD-like symptoms was 21 months. Real-Time MRI (3 Tesla) was performed at 40 ms temporal resolution using undersampled radial fast low-angle shot acquisitions with nonlinear inverse image reconstruction. MRI movies dynamically visualized bolus transit of pineapple juice through the gastroesophageal junction, position of the fundoplication wrap and recurring hernia or reflux during Valsalva maneuver. MRI results were compared to endoscopic findings. Real-Time MRI was successfully completed in all patients without adverse events (average examination time 15 min). Morphological correlates for GERD-like symptoms were evident in 20 patients (90.1%) with gastric reflux in 19 cases. Nine patients (40.1%) had wrap disruption and recurrent gastric hernia. Wrap migration or telescoping hernia was detected in nine patients (40.1%). One patient presented with continued reflux despite intact fundoplication wrap. Esophageal dysmotility with delayed bolus passage was observed in one case. On endoscopy, gastric hernia or wrap disruption was diagnosed in seven cases, and esophagitis or Barret’s metaplasia in nine cases. Real-Time MRI is a fast and safe modality for dynamic imaging after fundoplication, without radiation exposure or administration of gadolinium-based contrast media. In a relevant number of cases, Real-Time MRI reveals correlates for GERD-like symptoms. • Real-Time MRI reliably visualizes the gastroesophageal junction after fundoplication surgery. • Patients with recurring GERD-like symptoms have a high rate of morphological failure patterns that can be identified by Real-Time MRI. • Dynamic assessment of gastroesophageal junction by Real-Time MRI is a perspective diagnostic tool for detection of fundoplication failure.
-
Real-Time MRI at a resolution of 20 ms.
NMR in Biomedicine, 2010Co-Authors: Martin Uecker, Klaus-dietmar Merboldt, Shuo Zhang, Dirk Voit, Alexander Karaus, Jens FrahmAbstract:The desire to visualize noninvasively physiological processes at high temporal resolution has been a driving force for the development of MRI since its inception in 1973. In this article, we describe a unique method for Real-Time MRI that reduces image acquisition times to only 20 ms. Although approaching the ultimate limit of MRI technology, the method yields high image quality in terms of spatial resolution, signal-to-noise ratio and the absence of artifacts. As proposed previously, a fast low-angle shot (FLASH) gradient-echo MRI technique (which allows for rapid and continuous image acquisitions) is combined with a radial encoding scheme (which offers motion robustness and moderate tolerance to data undersampling) and, most importantly, an iterative image reconstruction by regularized nonlinear inversion (which exploits the advantages of parallel imaging with multiple receiver coils). In this article, the extension of regularization and filtering to the temporal domain exploits consistencies in successive data acquisitions and thereby enhances the degree of radial undersampling in a hitherto unexpected manner by one order of magnitude. The results obtained for turbulent flow, human speech production and human heart function demonstrate considerable potential for Real-Time MRI studies of dynamic processes in a wide range of scientific and clinical settings. Copyright © 2010 John Wiley & Sons, Ltd.
B George - One of the best experts on this subject based on the ideXlab platform.
-
laser thermal therapy real time MRI guided and computer controlled procedures for metastatic brain tumors
Lasers in Surgery and Medicine, 2011Co-Authors: Alexandre Carpentier, Roger J Mcnichols, Jason R Stafford, Jean Guichard, D Reizine, Suzette Delaloge, E Vicaut, Didier Payen, Ashok Gowda, B GeorgeAbstract:Background and Objective We report the final results of a pilot clinical trial exploring the safety and feasibility of Real-Time magnetic resonance-guided laser-induced thermal therapy (MRgLITT) for treatment of resistant focal metastatic intracranial tumors. Study Design In patients with chemotherapy, whole-brain radiation, and radiosurgery resistant metastatic intracranial tumors, minimally invasive stereotaxic placement of a saline-cooled interstitial fiberoptic laser applicator under local anesthesia was followed by laser irradiation during continuous magnetic resonance imaging (MRI) scanning. A computer workstation extracted Real-Time temperature-sensitive information for feedback control over laser delivery. A total of 15 metastatic tumors were treated in 7 patients. Patients were followed with physical exam and imaging for 30 months. Results In all cases, the procedure was well tolerated, and patients were discharged home within 24 hours. Follow-up imaging at up to 30 months showed an acute increase in apparent lesion volume followed by a gradual and steady decrease. No tumor recurrence within thermal ablation zones was noted. Kaplan–Meier analysis indicated that the median survival was 19.8 months. Conclusion Real-Time magnetic resonance (MR) guidance of laser-induced thermal therapy (LITT) offers a high level of control. This tool therefore enables a minimally invasive option for destruction and treatment of resistant focal metastatic intracranial tumors. MR-guided LITT appears to provide a safe and potentially effective treatment for recurrent focal metastatic brain disease. A larger phase II and III series would be of interest to quantify potential median survival advantage. Lasers Surg. Med. 43:943–950, 2011. © 2011 Wiley Periodicals, Inc.
