Publications by authors named "Robert E Watson"

56 Publications

Scout it out! Wake-Up Stroke Protocol to Expedite MRI in Stroke Patients.

Curr Probl Diagn Radiol 2021 Dec 2. Epub 2021 Dec 2.

Department of Radiology, Mayo Clinic, Jacksonville, FL.

In wake-up stroke patients, magnetic resonance imaging (MRI) is useful to identify patients that would benefit from thrombolytic therapy. Our multidisciplinary stroke team developed and implemented a workflow to rapidly identify patients that are able to safely undergo an MRI exam, thus decreasing time to treatment. We employ a full-body CT scout image in our CT head protocol for acute stroke in order to identify implantable devices and foreign bodies. This protocol highlights the importance of radiology playing an active role on the multidisciplinary stroke team in order to effectively and promptly treat patients.
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http://dx.doi.org/10.1067/j.cpradiol.2021.11.005DOI Listing
December 2021

Cochlear Implants and Magnetic Resonance Imaging: Experience With Over 100 Studies Performed With Magnets in Place.

Otol Neurotol 2021 01;42(1):51-58

Department of Otorhinolaryngology.

Objective: To evaluate adverse events and feasibility of performing 1.5-T MRI in patients with cochlear implants (CI) and auditory brainstem implants (ABI).

Setting: Single tertiary academic referral center.

Patients: CI and ABI recipients undergoing 1.5-T MRI without internal magnet removal.

Intervention(s): MRI after tight headwrap application.

Main Outcome Measures: Adverse events, patient tolerance.

Results: A total of 131 MR studies in 79 patients were performed, with a total of 157 study ears. Sixty-one patients (77%) had unilateral devices. Four patients (5%) underwent MRI with ABI magnets in place. Sixteen patients (20%) had MRI-compatible devices that did not require a head wrap. There were no instances of device stimulation, device malfunction, or excessive heating of the receiver-stimulator package. Magnet tilt requiring manual repositioning occurred during seven studies (4.5%) and magnet displacement requiring operative intervention occurred during seven studies (4.5%). Significant pain where imaging had to be discontinued occurred during three episodes (2%). No adverse events were noted among patients who underwent MRI with an MRI-compatible magnet.

Conclusions: MRI with CI or ABI magnets in place is associated with a low prevalence of adverse events when performed in a controlled setting. Many partial magnet displacements can be corrected with firm manual pressure. Devices with magnets that align with the field within their housing were not associated with any adverse events and do not require immobilization of the magnet during the scan. These may be valuable in patients with known or anticipated need for MRI.
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http://dx.doi.org/10.1097/MAO.0000000000002866DOI Listing
January 2021

MR Safety: Coming of Age.

Authors:
Robert E Watson

Magn Reson Imaging Clin N Am 2020 11 11;28(4):xv-xvi. Epub 2020 Sep 11.

Department of Radiology, Mayo Clinic, 200 First Street, Rochester, MN 55905, USA. Electronic address:

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http://dx.doi.org/10.1016/j.mric.2020.08.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7485547PMC
November 2020

MR Imaging Safety Events: Analysis and Improvement.

Magn Reson Imaging Clin N Am 2020 Nov 17;28(4):593-600. Epub 2020 Sep 17.

Department of Radiology, University of Washington, 1959 Northeast Pacific Street, Seattle, WA 98195, USA.

Multiple factors, including tight patient scheduling, complex electronic medical records, and increasing numbers of implanted devices, increase chances of MR imaging safety event occurrence. Several MR imaging safety incidents are described in this article, including the safety conditions and other factors that contributed to the events. MR imaging safety policy and procedural improvements that address these are also described. Specific new revision points in the American College of Radiology Manual on MR Safety are viewed in the context of these events, with emphasis on how their implementation could reduce probability of similar event recurrence.
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http://dx.doi.org/10.1016/j.mric.2020.07.004DOI Listing
November 2020

Magnetic Resonance Safety in the 7T Environment.

Magn Reson Imaging Clin N Am 2020 Nov 17;28(4):573-582. Epub 2020 Sep 17.

Department of Radiology, Mayo Clinic, 200 First Street Southwest, Rochester, MN 55905, USA.

The arrival of 7T MR imaging into the clinic represents a significant step-change in MR technology. This article describes safety concerns associated with imaging at 7T, including the increased magnetic forces on magnetic objects at 7T and the interaction of the 300 MHz (Larmor) radiofrequency energy with tissue in the body. A dedicated multidisciplinary 7T Safety team should develop safety policies and procedures to address these safety challenges and keep abreast of best practice in the field. The off-label imaging of implanted devices is discussed, and also the need for staff training to deal with complexities of patient handling and image interpretation.
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http://dx.doi.org/10.1016/j.mric.2020.07.002DOI Listing
November 2020

MR Safety: Active Implanted Electronic Devices.

Magn Reson Imaging Clin N Am 2020 Nov;28(4):549-558

Department of Radiology, Mayo Clinic, 200 First Street Southwest, Rochester, MN 55905, USA.

New implanted medical devices continue to be made available for treatment of medical conditions. Many recipients can benefit from the diagnostic power of MR imaging. Provisions must be made to determine if these patients can be safely scanned. Metal-containing devices can be considered either MR unsafe or conditional. It is essential that all components of an implanted system are completely and accurately identified, with the most restrictive MR safety condition dictating the scanning approach. MR safety considerations for major classes of implanted devices are discussed, recognizing that there have been reports of serious device-related MR safety incidents.
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http://dx.doi.org/10.1016/j.mric.2020.08.001DOI Listing
November 2020

Magnetic Resonance Imaging-Guided Focused Ultrasound Ablation of Lumbar Facet Joints of a Patient With a Magnetic Resonance Image Non-Conditional Pacemaker at 1.5T.

Mayo Clin Proc Innov Qual Outcomes 2020 Aug 5;4(4):464-468. Epub 2020 Aug 5.

Department of Radiology, Mayo Clinic, Rochester, MN 55905.

Objective: To provide an initial report that patients with magnetic resonance imaging (MRI) non-conditional cardiac implanted electronic device (CIED) can undergo state-of-the-art magnetic resonance imaging-guided focused (MRgFUS) ablation procedures with careful planning and integration of the procedure into an established CIED MRI practice.

Patient And Methods: We describe an MRgFUS ablation treatment of lumbar facet joints in a patient with an MRI non-conditional CIED (pacemaker), completed in accordance with our institutional CIED/MRI practice guidelines.

Results: A risk-benefit analysis by a coordinated multidisciplinary team before this treatment was performed to account for the risks associated with the MRI non-conditional pacemaker in the context of the MRgFUS procedure.

Conclusion: The patient had no adverse cardiac event during or following this procedure.
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http://dx.doi.org/10.1016/j.mayocpiqo.2020.04.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7411156PMC
August 2020

Prospective evaluation of the utility of magnetic resonance imaging in patients with non-MRI-conditional pacemakers and defibrillators.

J Cardiovasc Electrophysiol 2020 11 31;31(11):2931-2939. Epub 2020 Aug 31.

Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, USA.

Background: Magnetic resonance imaging (MRI) in patients with legacy cardiovascular implantable electronic devices (CIEDs) in situ is likely underutilized. We hypothesized the clinical benefit of MRI would outweigh the risks in legacy CIED patients.

Methods: This is a single-center retrospective study that evaluated and classified the utility of MRI using a prospectively maintained database. The outcomes were classified as aiding in diagnosis, treatment, or both for the patients attributable to the MRI. We then assessed the incidence of adverse effects (AE) when the MRI was performed.

Results: In 668, MRIs performed on 479 patients, only 13 (1.9%) MRIs did not aid in the diagnosis or treatment of the patient. Power-on reset events without clinical sequelae in three scans (0.45%) were the only AE. The probability of an adverse event happening without any benefit from the MRI scan was 1.1 × 10 . A maximum benefit in diagnosis using MRI was obtained in ruling out space-occupying lesions (121/185 scans, 65.4%). Scans performed in patients for elucidating answers to queries in treatment were most frequently done for disease staging at long term follow-up (167/470 scans, 35.5%). Conservative treatment (184/470 scans, 39%) followed by medication changes (153/470 scans, 28.7%) were the most common treatment decisions made.

Conclusions: The utility of MRI in patients with non-MRI-conditional CIEDs far outweighs the risk of adverse events when imaging is done in the context of a multidisciplinary program that oversees patient safety.
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http://dx.doi.org/10.1111/jce.14705DOI Listing
November 2020

Image Artifact Management for Clinical Magnetic Resonance Imaging on a 7 T Scanner Using Single-Channel Radiofrequency Transmit Mode.

Invest Radiol 2019 12;54(12):781-791

From the Department of Radiology, Mayo Clinic.

Objectives: The aim of this work was to devise mitigation strategies for addressing a range of image artifacts on a clinical 7 T magnetic resonance imaging scanner using the regulatory-approved single-channel radiofrequency transmit mode and vendor-supplied radiofrequency coils to facilitate clinical scanning within reasonable scan times.

Materials And Methods: Optimized imaging sequence protocols were developed for routine musculoskeletal knee and neurological imaging. Sources of severe image nonuniformities were identified, and mitigation strategies were devised. A range of custom-made high permittivity dielectric pads were used to compensate for B1 and B1 inhomogeneities, and also for magnetic susceptibility-induced signal dropouts particularly in the basal regions of the temporal lobes and in the cerebellum.

Results: Significant improvements in image uniformity were obtained using dielectric pads in the knee and brain. A combination of small voxels, reduced field of view B0 shimming, and high in-plane parallel imaging factors helped to minimize signal loss in areas of high susceptibility-induced field distortions. The high inherent signal-to-noise ratio at 7 T allowed for high receiver bandwidths and thin slices to minimize chemical shift artifacts. Intermittent artifacts due to radiofrequency inversion pulse limitations (power, bandwidth) were minimized with dielectric pads. A patient with 2 implanted metallic cranial fixation devices located within the radiofrequency transmit field was successfully imaged, with minimal image geometric distortions.

Conclusions: Challenges relating to severe image artifacts at 7 T using single-channel radiofrequency transmit functionality in the knee and brain were overcome using the approaches described in this article. The resultant high diagnostic image quality paves the way for incorporation of this technology into the routine clinical workflow. Further developmental efforts are required to expand the range of applications to other anatomical areas, and to expand the evidence- and knowledge-base relating to the safety of scanning patients with implanted metallic devices.
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http://dx.doi.org/10.1097/RLI.0000000000000598DOI Listing
December 2019

Segmentation errors and intertest reliability in automated and manually traced hippocampal volumes.

Ann Clin Transl Neurol 2019 09 6;6(9):1807-1814. Epub 2019 Sep 6.

Department of Radiology, Mayo Clinic, Rochester, Minnesota.

Objective: To rigorously compare automated atlas-based and manual tracing hippocampal segmentation for accuracy, repeatability, and clinical acceptability given a relevant range of imaging abnormalities in clinical epilepsy.

Methods: Forty-nine patients with hippocampal asymmetry were identified from our institutional radiology database, including two patients with significant anatomic deformations. Manual hippocampal tracing was performed by experienced technologists on 3T MPRAGE images, measuring hippocampal volume up to the tectal plate, excluding the hippocampal tail. The same images were processed using NeuroQuant and FreeSurfer software. Ten subjects underwent repeated manual hippocampal tracings by two additional technologists blinded to previous results to evaluate consistency. Ten patients with two clinical MRI studies had volume measurements repeated using NeuroQuant and FreeSurfer.

Results: FreeSurfer raw volumes were significantly lower than NeuroQuant (P < 0.001, right and left), and hippocampal asymmetry estimates were lower for both automatic methods than manual tracing (P < 0.0001). Differences remained significant after scaling volumes to age, gender, and scanner matched normative percentiles. Volume reproducibility was fair (0.4-0.59) for manual tracing, and excellent (>0.75) for both automated methods. Asymmetry index reproducibility was excellent (>0.75) for manual tracing and FreeSurfer segmentation and fair (0.4-0.59) for NeuroQuant segmentation. Both automatic segmentation methods failed on the two cases with anatomic deformations. Segmentation errors were visually identified in 25 NeuroQuant and 27 FreeSurfer segmentations, and nine (18%) NeuroQuant and six (12%) FreeSurfer errors were judged clinically significant.

Interpretation: Automated hippocampal volumes are more reproducible than hand-traced hippocampal volumes. However, these methods fail in some cases, and significant segmentation errors can occur.
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http://dx.doi.org/10.1002/acn3.50885DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6764491PMC
September 2019

Gadolinium Administration in Undetected Pregnancy: Cause for Alarm?

Radiology 2019 Oct 20;293(1):201-202. Epub 2019 Aug 20.

From the Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.

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http://dx.doi.org/10.1148/radiol.2019191634DOI Listing
October 2019

ACR guidance document on MR safe practices: Updates and critical information 2019.

J Magn Reson Imaging 2020 02 29;51(2):331-338. Epub 2019 Jul 29.

American College of Radiology, Reston, Virginia, USA.

The need for a guidance document on MR safe practices arose from a growing awareness of the MR environment's potential risks and adverse event reports involving patients, equipment, and personnel. Initially published in 2002, the American College of Radiology White Paper on MR Safety established de facto industry standards for safe and responsible practices in clinical and research MR environments. The most recent version addresses new sources of risk of adverse events, increases awareness of dynamic MR environments, and recommends that those responsible for MR medical director safety undergo annual MR safety training. With regular updates to these guidelines, the latest MR safety concerns can be accounted for to ensure a safer MR environment where dangers are minimized. Level of Evidence: 1 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2020;51:331-338.
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http://dx.doi.org/10.1002/jmri.26880DOI Listing
February 2020

Safety Considerations of 7-T MRI in Clinical Practice.

Radiology 2019 09 16;292(3):509-518. Epub 2019 Jul 16.

From the Department of Radiology, University of Washington, 1959 NE Pacific St, Seattle, WA 98195-7117 (M.N.H.); Department of Radiology, University of Minnesota, Minneapolis, Minn (A.M., J.F.); Department of Clinical Physical Therapy, University of Southern California, Los Angeles, Calif (F.G.S.); Department of Radiology, University of Utah Health Sciences Center, Salt Lake City, Utah (U.R.); RADIOLOGY-Planning, Kansas City, Mo (T.G.); Department of Radiology, Mayo Clinic, Rochester, Minn (R.E.W.); G3 Global Group, Boulder, Colo, Mo (T.D.G.); and Department of Radiology, University of Pittsburgh Medical Center, Pittsburgh, Pa (E.K.).

Although 7-T MRI has recently received approval for use in clinical patient care, there are distinct safety issues associated with this relatively high magnetic field. Forces on metallic implants and radiofrequency power deposition and heating are safety considerations at 7 T. Patient bioeffects such as vertigo, dizziness, false feelings of motion, nausea, nystagmus, magnetophosphenes, and electrogustatory effects are more common and potentially more pronounced at 7 T than at lower field strengths. Herein the authors review safety issues associated with 7-T MRI. The rationale for safety concerns at this field strength are discussed as well as potential approaches to mitigate risk to patients and health care professionals.
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http://dx.doi.org/10.1148/radiol.2019182742DOI Listing
September 2019

Safety of thoracic magnetic resonance imaging for patients with pacemakers and defibrillators.

Heart Rhythm 2019 11 29;16(11):1645-1651. Epub 2019 May 29.

Department of Cardiovascular Medicine, Mayo Clinic, Rochester, Minnesota; Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota. Electronic address:

Background: During magnetic resonance imaging (MRI), cardiac implantable electronic device (CIED) leads can be antennae to focus energy onto myocardium, leading to heating and arrhythmias. Clinical data on thoracic MRI safety for patients with legacy devices are limited.

Objective: The purpose of this study was to identify patients undergoing thoracic MRI with legacy devices, compare the incidence of adverse events of those patients with control patients undergoing brain MRI with legacy devices, and compare paired cardiac troponin T (cTnT) values.

Methods: In this single-center study, we reviewed a prospectively collected database of patients with CIED undergoing MRI from January 25, 2008, through February 28, 2017.

Results: Of 952 patients (1290 scans), 120 patients (12.6%) underwent 134 thoracic MRI scans with legacy CIEDs (median [range] age 61.98 [21.24-86.96] years; male 71.1%). Median (range; interquartile range [IQR]) age of leads across devices was 3.5 (1.6-7.1; 5.5) years; implantable cardioverter-defibrillators (ICDs) were oldest (median [range; IQR], 3.7 [1.1-8.0; 6.9] years). No difference was observed in incidence of adverse events between groups. Paired cTnT values were compared for 19 patients (19 scans) with no difference between pre- and postimaging values. No significant difference was present in device setting values before and after MRI (mean follow-up 72.5 days). Incidence of adverse events was no different after adjustment for ICD coil number.

Conclusion: Thoracic MRI is relatively safe in an institutional multidisciplinary program. It does not represent greater risk than brain MRI for patients with legacy CIEDs.
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http://dx.doi.org/10.1016/j.hrthm.2019.05.031DOI Listing
November 2019

Patient-oriented education and visual-aid intervention are inadequate to identify patients with potential capsule retention: a prospective randomized study.

Scand J Gastroenterol 2019 May 29;54(5):662-665. Epub 2019 Apr 29.

a Division of Gastroenterology and Hepatology , Mayo Clinic , Rochester , MN , USA.

The key procedure-related risk with video capsule endoscopy (VCE) is capsule retention, which should be suspected in patients who have not reported capsule passage. The study aims were to determine the frequency of capsule passage visualization and the difference in self-reporting of capsule passage between patients who receive patient-oriented education (POE) and patients who receive POE and a visual aid intervention in the form of a wrist band (WB). This was a prospective randomized study that enrolled patients undergoing VCE. Patients were randomly assigned to a POE group versus a POE and WB group. POE consisted of verbal education and an information booklet. Both groups received instructions to notify the study team regarding capsule passage. Sixty patients (mean age 57 ± 18 years; 61% female) were included. A total of 57 patients were included in the analysis (3 lost to follow-up; 28 in POE group; 29 in WB group). Capsule passage status was reported by 68% without significant difference between POE and WB groups (72% vs. 64%;  = .51). Capsule passage status was obtained from all 57 patients with the addition of a proactive follow-up. Only 56% ( = 32) reported visualizing capsule passage. Of the remaining patients who did not visualize capsule passage, 60% ( = 15) reported on this without significant difference between the POE and WB groups ( = .23). Lack of visualization of capsule passage is a poor indicator of retention. Self-reporting of VCE passage status is suboptimal and the addition of a visual aid did not improve this parameter.
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http://dx.doi.org/10.1080/00365521.2019.1608465DOI Listing
May 2019

Augmenting MRI Safety Screening Processes: Reliable Identification of Cardiac Implantable Electronic Devices by a Ferromagnetic Detector System.

J Magn Reson Imaging 2019 Jun 26;49(7):e297-e299. Epub 2018 Sep 26.

Metrasens Inc, Lisle, Illinois, USA.

Level Of Evidence: 1 Technical Efficacy Stage: 5 J. Magn. Reson. Imaging 2019;49:e297-e299.
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http://dx.doi.org/10.1002/jmri.26277DOI Listing
June 2019

Autoimmune epilepsy: findings on MRI and FDG-PET.

Br J Radiol 2019 Jan 20;92(1093):20170869. Epub 2018 Sep 20.

1 Department of Radiology, Mayo Clinic , Rochester, MN , USA.

Autoimmune epilepsy (AE) is becoming increasingly recognized as a potentially reversible cause of frequent or medically intractable seizures and cognitive deterioration. We describe various presentations of autoimmune encephalopathy which have specifically presented with seizure and describe reported imaging findings. This is organized as a review of the more common autoantibodies which can specifically precipitate seizure according to the intracellular or extracellular location of the targeted antigen. For each antibody, we illustrate their pathophysiology, characteristic clinical presentations with typical effective treatments and prognoses and imaging findings on MRI and PET/CT exams. Parenchymal involvement is variable with the limbic structures typically affected; however, non-limbic cortex, cerebellum, brainstem and basal ganglia can also be involved. In the acute setting, affected regions typically demonstrate T hyperintensity with mild mass effect from edema and increased F-fludeoxyglucose uptake. Chronically involved parenchyma will often undergo atrophy and demonstrate decreased metabolism; mesial temporal sclerosis is often the end result when the limbic system is involved. Without treatment, long-term effects from AE range from ongoing cognitive dysfunction and refractory seizures to death. Familiarity with AE may prompt appropriate antibody screening, particularly in cases of refractory seizure disorders. Early investigation and proper management of AE cases may help to prevent parenchymal and neurologic deterioration in these patients.
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http://dx.doi.org/10.1259/bjr.20170869DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435058PMC
January 2019

Lipoid proteinosis: Unfamiliar skin findings delay diagnosis.

JAAD Case Rep 2018 Jul 28;4(6):609-611. Epub 2018 Jun 28.

Department of Dermatology, Mayo Clinic, Rochester, Minnesota.

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http://dx.doi.org/10.1016/j.jdcr.2018.03.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6039698PMC
July 2018

Laser ablation for mesial temporal epilepsy: a multi-site, single institutional series.

J Neurosurg 2018 Jul 1:1-8. Epub 2018 Jul 1.

11Neurosurgery, Mayo Clinic, Rochester, Minnesota.

OBJECTIVEAlthough it is still early in its application, laser interstitial thermal therapy (LiTT) has increasingly been employed as a surgical option for patients with mesial temporal lobe epilepsy. This study aimed to describe mesial temporal lobe ablation volumes and seizure outcomes following LiTT across the Mayo Clinic's 3 epilepsy surgery centers.METHODSThis was a multi-site, single-institution, retrospective review of seizure outcomes and ablation volumes following LiTT for medically intractable mesial temporal lobe epilepsy between October 2011 and October 2015. Pre-ablation and post-ablation follow-up volumes of the hippocampus were measured using FreeSurfer, and the volume of ablated tissue was also measured on intraoperative MRI using a supervised spline-based edge detection algorithm. To determine seizure outcomes, results were compared between those patients who were seizure free and those who continued to experience seizures.RESULTSThere were 23 patients who underwent mesial temporal LiTT within the study period. Fifteen patients (65%) had left-sided procedures. The median follow-up was 34 months (range 12-70 months). The mean ablation volume was 6888 mm3. Median hippocampal ablation was 65%, with a median amygdala ablation of 43%. At last follow-up, 11 (48%) of these patients were seizure free. There was no correlation between ablation volume and seizure freedom (p = 0.69). There was also no correlation between percent ablation of the amygdala (p = 0.28) or hippocampus (p = 0.82) and seizure outcomes. Twelve patients underwent formal testing with computational visual fields. Visual field changes were seen in 67% of patients who underwent testing. Comparing the 5 patients with clinically noticeable visual field deficits to the rest of the cohort showed no significant difference in ablation volume between those patients with visual field deficits and those without (p = 0.94). There were 11 patients with follow-up neuropsychological testing. Within this group, verbal learning retention was 76% in the patients with left-sided procedures and 89% in those with right-sided procedures.CONCLUSIONSIn this study, there was no significant correlation between the ablation volume after LiTT and seizure outcomes. Visual field deficits were common in formally tested patients, much as in patients treated with open temporal lobectomy. Further studies are required to determine the role of amygdalohippocampal ablation.
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http://dx.doi.org/10.3171/2018.2.JNS171873DOI Listing
July 2018

Safety of Laser Interstitial Thermal Therapy in Patients With Pacemakers.

Oper Neurosurg (Hagerstown) 2018 11;15(5):E69-E72

Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota.

Background And Importance: Laser interstitial thermal therapy (LiTT) has increasingly been used as a treatment option for medically refractory epilepsy, tumors, and radiation necrosis. The use of LiTT requires intraoperative magnetic resonance (MR) thermography. This can become an issue in patients with other implanted therapeutic devices such as pacemakers and vagal nerve stimulators due to concerns regarding increases in the specific absorption rate (SAR). This is a technical case report demonstrating a successfully and safely performed LiTT in a 1.5-T magnetic resonance imaging (MRI) in a patient with a pacemaker for mesial temporal sclerosis.

Clinical Presentation: An 83-yr-old gentleman who had an implanted cardiac pacemaker presented with medically intractable epilepsy and was confirmed to have mesial temporal sclerosis on imaging. Video electroencephalography demonstrated concordant ipsilateral seizures and semiology. He underwent LiTT for ablation of the mesial temporal lobe. This was performed with the below described protocol with a cardiology nurse monitoring the patient's cardiac condition and a physicist monitoring SAR, and MR imaging quality without any adverse events.

Conclusion: This study reports on a protocol of cardiac and MR SAR to safely perform MR-guided LiTT in the setting of traditional pacemakers in patients who are not pacemaker dependent.
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http://dx.doi.org/10.1093/ons/opx292DOI Listing
November 2018

Mortality After Magnetic Resonance Imaging of the Brain in Patients With Cardiovascular Implantable Devices.

Circ Arrhythm Electrophysiol 2018 01;11(1):e005480

From the Division of Cardiovascular Diseases (D.P., N.G.A., C.M.D., S.K., S.J.A., Y.-M.C., P.A.F.), Department of Radiology (M.L.J., J.P.F., R.E.W.), and Division of Biomedical Statistics and Informatics (R.A.M.), Mayo Clinic, Rochester, MN; and Division of Biomedical Statistics and Informatics, Mayo Clinic, Jacksonville, FL (D.O.H.).

Background: Use of magnetic resonance imaging (MRI) brain is restricted in patients with cardiovascular implantable electronic devices (CIEDs). We proposed to determine whether mortality difference exists for patients with non-MRI-conditional CIEDs undergoing brain MRI compared with controls.

Methods And Results: Retrospective analysis of prospectively collected data was performed to compare all-cause mortality in patients with CIEDs undergoing brain MRI (CIED-MRI) with 3 control groups matched for age, sex, imaging year, and type of CIED: (1) no CIED, brain MRI (no-CIED-MRI); (2) CIED, brain computerized tomography (CT) scan (CIED-CT); and (3) no CIED, brain CT (no-CIED-CT). The primary outcome was a significant difference (<0.05) between estimated mortality rates. Secondary outcomes were changes in device function before and after brain MRI. The estimated all-cause mortality at 5 years for the CIED-MRI group [mean age (±SD), 68.2 years (15.3 years); 61.2% men] was not significantly different from patients who underwent CT with or without a device (CIED-CT group: hazard ratio, 0.814; 95% confidence interval, 0.593-1.117; =0.2; no-CIED-CT group: hazard ratio, 1.149; 95% confidence interval, 0.818-1.613; =0.4). There was a significant increase in mortality between CIED-MRI and no-CIED-MRI groups (hazard ratio, 1.463; 95% confidence interval, 1.019-2.099; =0.04).

Conclusions: Brain MRI in patients with CIEDs does not carry an increased mortality risk compared with brain CT and can be performed with adherence to appropriate procedural protocols.
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http://dx.doi.org/10.1161/CIRCEP.117.005480DOI Listing
January 2018

MR Imaging and Cochlear Implants with Retained Internal Magnets: Reducing Artifacts near Highly Inhomogeneous Magnetic Fields.

Radiographics 2018 Jan-Feb;38(1):94-106

From the Departments of Radiology (H.A.E., A.C.P., R.E.W.) and Otorhinolaryngology (M.L.C.), Mayo Clinic, 200 First St SW, Rochester, MN 55905.

The number of patients receiving cochlear implants and auditory brainstem implants for severe to profound sensorineural hearing loss has rapidly increased. These implants consist of an internal component implanted between the skull and the temporal scalp and an external removable speech processor unit. A small magnet within the internal component is commonly used to hold the external speech processor unit in place. Several cochlear implant models have recently received U.S. Food and Drug Administration and European Economic Area regulatory approval to allow magnetic resonance (MR) imaging examinations to be performed under certain specified conditions. The small internal magnet presents a challenge for imaging of the head and neck near the implant, creating a nonlinear magnetic field inhomogeneity and significant MR imaging artifacts. Fat-saturation failures and susceptibility artifacts severely degrade image quality. Typical artifacts at diffusion-weighted imaging and accelerated imaging are exacerbated. Each examination may require impromptu adjustments to allow visualization of the tissue or contrast of interest. Patients may also be quite uncomfortable during the examination, as a result of either imposed magnetic forces or a tight head wrap that is often applied to minimize internal magnet movement. Translational forces and torque sometimes displace the implanted magnet even when a head wrap is used. Diseases such as neurofibromatosis type 2 that are associated with bilateral vestibular schwannomas and hearing loss often require lifelong tumor surveillance with MR imaging. A collaborative team of radiologists, technologists, and/or medical physicists or MR imaging scientists, armed with strategies to mitigate artifacts near implanted magnets, can customize the examination for better visualization of tissue and consistent comparison examinations over time. RSNA, 2018.
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http://dx.doi.org/10.1148/rg.2018170135DOI Listing
August 2018

Safety of magnetic resonance imaging in patients with legacy pacemakers and defibrillators and abandoned leads.

Heart Rhythm 2018 02 16;15(2):228-233. Epub 2017 Oct 16.

Division of Cardiovascular Diseases, Rochester, Minnesota. Electronic address:

Background: During magnetic resonance imaging (MRI), abandoned leads may act as antennae that result in tissue heating and arrhythmia induction.

Objective: The purpose of this study was to assess the safety of MRI in patients with abandoned leads, with the addition of cardiac troponin T (cTnT) assessment to screen for myocardial damage.

Methods: We reviewed our prospectively collected database of patients with cardiovascular implantable electronic devices (CIEDs) undergoing MRI between 2008 and 2017 at Mayo Clinic, Rochester, MN, and selected patients who had abandoned leads. We compared the adverse events in this population with an age, sex, and site of MRI-matched cohort of patients selected from this database. We evaluated paired (before/after) cTnT values using MRI in these patients.

Results: Of 952 patients, 80 (8.4%) underwent 97 MRI scans with CIEDs in situ with 90 abandoned leads in place during the scans. The median age was 66 years (interquartile range 22.3 years) 66.1 years (interquartile range, Q1,Q3: 53.6, 75.9) with 66.3% (53 patients) men. There was no clinical or electrical evidence of CIED dysfunction, arrhythmias, or pain. Paired samples for the measurement of cTnT values were available in 40 patients undergoing 44 MRI examinations. The mean difference between the pre- and postimaging values was -0.002 ± 0.006 ng/mL (interquartile range 0). There was no difference after adjustment for total number of leads per patient and total number of implantable cardioverter-defibrillator coils.

Conclusion: There was no evidence of myocardial injury as measured by paired cTnT. The risk of MRI with abandoned leads appears low, suggesting a favorable risk-benefit profile in patients with CIEDs and abandoned leads who are considered for MRI.
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http://dx.doi.org/10.1016/j.hrthm.2017.10.022DOI Listing
February 2018

Evaluation of feasibility of 1.5 Tesla prostate MRI using body coil RF transmit in a patient with an implanted vagus nerve stimulator.

Med Phys 2017 Nov 9;44(11):5749-5754. Epub 2017 Oct 9.

Department of Radiology, Mayo Clinic, Rochester, MN, 55905, USA.

Purpose: To assess risks of RF-heating of a vagus nerve stimulator (VNS) during 1.5 T prostate MRI using body coil transmit and to compare these risks with those associated with MRI head exams using a transmit/receive head coil.

Methods: Spatial distributions of radio-frequency (RF) B1 fields generated by transmit/receive (T/R) body and head coils were empirically assessed along the long axis of a 1.5 T MRI scanner bore. Measurements were obtained along the center axis of the scanner and laterally offset by 15 cm (body coil) and 7 cm (head coil). RF-field measurements were supplemented with direct measurements of RF-heating of 15 cm long copper wires affixed to and submerged in the "neck" region of the gelled saline-filled (sodium chloride and polyacrylic acid) "head-and-torso" phantom. Temperature elevations at the lead tips were measured using fiber-optic thermometers with the phantom positioned at systematically increased distances from the scanner isocenter.

Results: B1 field measurements demonstrated greater than 10 dB reduction in RF power at distances beyond 28 cm and 24 cm from isocenter for body and head coil, respectively. Moreover, RF power from body coil transmit at distances greater than 32 cm from isocenter was found to be lower than from the RF power from head coil transmit measured at locations adjacent to the coil array at its opening. Correspondingly, maximum temperature elevations at the tips of the copper wires decreased with increasing distance from isocenter - from 7.4°C at 0 cm to no appreciable heating at locations beyond 40 cm.

Conclusions: For the particular scanner model evaluated in this study, positioning an implanted VNS farther than 32 cm from isocenter (configuration achievable for prostate exams) can reduce risks of RF-heating resulting from the body coil transmit to those associated with using a T/R head coil.
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http://dx.doi.org/10.1002/mp.12567DOI Listing
November 2017

Expanded phenotypes and outcomes among 256 LGI1/CASPR2-IgG-positive patients.

Ann Neurol 2017 Jul;82(1):79-92

Neuroimmunology Laboratory, Department of Neurology, Mayo Clinic, Rochester, MN.

Objective: To describe an expanded phenotypic spectrum and longitudinal outcome in 256 LGI1-IgG-seropositive and/or CASPR2-IgG-seropositive patients.

Methods: Patients were identified through service neural autoantibody evaluation. Ninety-five had longitudinal follow-up (7-456 months; median = 35).

Results: Among 3,910 patients tested, 196 were LGI1-IgG positive, 51 were CASPR2-IgG positive, and 9 were dual positive. Cerebrospinal fluid testing was less sensitive than serum testing, detecting only 24 of 38 (63%) LGI1-IgG-positive and 5 of 6 (83%) CASPR2-IgG-positive patients. LGI1-IgG-positive specimens had higher voltage-gated potassium channel-IgG immunoprecipitation values (0.33nmol/l, range = 0.02-5.14) than CASPR2-IgG-positive specimens (0.10nmol/l, range = 0.00-0.45, p < 0.001). Of patients presenting with pain or peripheral nervous system (PNS) manifestations, 39% were LGI1-IgG seropositive (7% had solely neuropathy or pain). Multivariate analysis identified age as the only significant predictor of central nervous system (CNS) versus PNS involvement (>50 years; odds ratio = 15, p < 0.001). Paroxysmal dizziness spells (PDS), a unique LGI1-IgG accompaniment (14% of patients), frequently delayed the diagnosis. T2-mesiotemporal hyperintensity was more common in LGI1-IgG-positive (41%) than in CASPR2-IgG-positive patients (p = 0.033). T1-bright basal ganglia were confined to LGI1-IgG-positive patients with faciobrachial-dystonic seizures (9 of 39, 31%). Cancer was found in 44% of LGI1-IgG/CASPR2-IgG dual seropositive patients (one-third thymoma). Response to initial immunotherapy was favorable in 97%; mean modified Rankin score was 3 (range = 1-5) at onset and 1.74 (range = 0-6) at last follow-up, with 9% having severe refractory disability, 20% being asymptomatic, 28% receiving immunotherapy, and 58% receiving antiepileptic medication.

Interpretation: Older age is a strong predictor of CNS involvement in patients seropositive for CASPR2-IgG or LGI1-IgG. Pain, peripheral manifestations, and stereotypic paroxysmal dizziness spells are common with LGI1-IgG. Response to initial immunotherapy is often favorable, but some patients remain severely disabled, requiring long-term immunotherapy and/or antiepileptic medications. Ann Neurol 2017;82:79-92.
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http://dx.doi.org/10.1002/ana.24979DOI Listing
July 2017

Magnetic Resonance Imaging in Nondependent Pacemaker Patients with Pacemakers and Defibrillators with a Nearly Depleted Battery.

Pacing Clin Electrophysiol 2017 May 23;40(5):476-481. Epub 2017 Mar 23.

Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota.

Background: Magnetic resonance imaging (MRI) in patients with non-MRI-conditional cardiac implantable electronic devices (CIEDs) has been shown to be safe when performed under closely monitored protocols. However, the safety of MRI in patients with devices with a nearly depleted battery has not been reported.

Methods: Prospective data were collected between January 2008 and May 2015 in patients with non-MRI-conditional CIEDs undergoing clinically indicated MRI under institutional protocol. Patients who were pacemaker dependent were excluded. Patients whose devices were at elective replacement indicator (ERI) at the time of MRI or close to ERI (ERI or replacement for battery depletion within 3 months of scan) were identified through database review and analyzed for clinical events.

Results: MRI scans (n = 569) were performed in 442 patients. Of these, we identified 13 scans performed with a nearly depleted battery in nine patients. All scans with implantable cardioverter defibrillators (ICDs, n = 9) were uneventful. However, two scans with pacemakers close to ERI resulted in a power-on-reset (PoR) event. One scan with a pacemaker close to ERI that was programmed to DOO mode reached ERI during MRI and automatically changed to VVI mode. Additionally, one scan with a pacemaker at ERI did not allow programming. All pacemakers with events were implanted before 2005.

Conclusion: Patients with pacemakers and ICDs with a nearly depleted battery can safely undergo MRI when patients are not pacemaker dependent. Attention should be paid because old devices can result in PoR or ERI during MRI, which may lead to oversensing and inhibition of pacing.
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http://dx.doi.org/10.1111/pace.13042DOI Listing
May 2017

Magnetic resonance imaging-guided laser interstitial thermal therapy for previously treated hypothalamic hamartomas.

Neurosurg Focus 2016 Oct;41(4):E8

Departments of 1 Neurosurgery.

OBJECTIVE Hypothalamic hamartomas (HHs) are associated with gelastic seizures and the development of medically refractory epilepsy. Magnetic resonance imaging-guided laser interstitial thermal therapy (MRg-LITT) is a minimally invasive ablative treatment that may have applicability for these deep-seated lesions. Here, the authors describe 3 patients with refractory HHs who they treated with MRg-LITT. METHODS An institutional review board-approved prospective database of patients undergoing Visualase MRg-LITT was retrospectively reviewed. Demographic and historical medical data, including seizure and medication histories, previous surgeries, procedural details, and surgical complications, along with radiological interpretation of the HHs, were recorded. The primary outcome was seizure freedom, and secondary outcomes included medication reduction, seizure frequency, operative morbidity, and clinical outcome at the latest follow-up. RESULTS All 3 patients in the multi-institutional database had developed gelastic seizures related to HH at the ages of 7, 7, and 9 years. They presented for further treatment at 25, 28, and 48 years of age, after previous treatments with stereotactic radiosurgery in all cases and partial hamartoma resection in one case. One ablation was complicated by a small tract hemorrhage, which was stable on postoperative imaging. One patient developed hyponatremia and experienced weight gain, which were respectively managed with fluid restriction and counseling. At the most recent follow-up at a mean of 21 months (range 1-32 months), one patient was seizure free while another had meaningful seizure reduction. Medication was reduced in one case. CONCLUSIONS Adults with gelastic seizures despite previous treatments can undergo MRg-LITT with reasonable safety and efficacy. This novel therapy may provide a minimally invasive alternative for primary and recurrent HH as the technique is refined.
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http://dx.doi.org/10.3171/2016.7.FOCUS16218DOI Listing
October 2016

Usefulness of repeat review of head magnetic resonance images during presurgical epilepsy conferences.

Epilepsy Res 2016 10 1;126:106-8. Epub 2016 Jul 1.

Department of Neurology, Mayo Clinic, 200 First St SW, Rochester, MN, 55905, United States. Electronic address:

Surgical epilepsy conferences are an important part of the process of determining whether a patient is a candidate for resective epilepsy surgery. At these conferences, repeat review (re-review) of the magnetic resonance images (MRIs) of the patient's head often occurs. This study assessed how often radiologic re-review at a presurgical epilepsy conference resulted in a changed interpretation of the head MRI. Charts were reviewed for 239 patients who had been presented at presurgical epilepsy conferences between 2008 and 2012. Of the 233 patients whose MRIs were re-reviewed, resective surgery was performed in 94 patients (40.3%). Forty-one patients (17.6%) had a previously undiagnosed finding, and 18 of the 41 (43.9%) underwent resective surgery. For 4 of the 41 patients (9.8%) with a previously undiagnosed pertinent finding, re-review detected abnormalities that were not amenable to surgical resection (autoimmunity or significant bilateral pathology).
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http://dx.doi.org/10.1016/j.eplepsyres.2016.06.005DOI Listing
October 2016

Presentation and Medical Management of Fibrocartilaginous Embolism in the Emergency Department.

J Emerg Med 2016 Sep 29;51(3):315-8. Epub 2016 Jun 29.

Department of Emergency Medicine, Mayo Clinic, Rochester, Minnesota.

Background: Fibrocartilaginous embolism is an exceedingly rare condition that was formerly a clinical diagnosis based on mechanism of injury, physical examination findings, and older magnetic resonance imaging (MRI) technologies without a specific histologic diagnosis. Spinal cord MRI diffusion-weighted imaging allows for a more specific diagnosis.

Case Report: A 14-year-old male felt a sudden pop in his back while running sprints in his gym class. He slowly developed bilateral lower extremity weakness and urinary incontinence, prompting an emergency department evaluation. A MRI scan of his lumbar spine revealed degeneration, desiccation, and bulging of the T12-L1 disc with an accompanying subacute Schmorl's nodule. There was adjacent cord swelling and central cord T2 hyperintensity, with accompanying restricted diffusion consistent with spinal cord infarction. These findings, in conjunction with paraplegia and mechanism of injury, were highly suggestive of fibrocartilaginous embolism. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: An emergent MRI scan with the proper sequencing and immediate consultation with a spine surgery specialist are important to exclude a compressive myelopathy that would necessitate acute surgical decompression. There is significant uncertainty in the initial management and stabilization of this rare condition that has not been addressed in the emergency medicine literature.
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http://dx.doi.org/10.1016/j.jemermed.2016.05.049DOI Listing
September 2016

Double Inversion Recovery Magnetic Resonance Imaging in Identifying Focal Cortical Dysplasia.

Pediatr Neurol 2016 08 5;61:87-93. Epub 2016 May 5.

Department of Neurology, Mayo Clinic, Rochester, Minnesota; Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, Minnesota.

Background: Focal cortical dysplasia is commonly recognized in pediatric epilepsy surgery. Despite characteristic radiographic features, focal cortical dysplasia can be subtle on magnetic resonance imaging. Double inversion recovery acquisition suppresses the white matter signal, which may enhance visualization of abnormal features at the gray-white matter interface. We assessed the ability of double inversion recovery to distinguish focal cortical dysplasia from periventricular nodular heterotopia and normal brain.

Methods: Patients with focal cortical dysplasia were identified from our patient database, as was a control group comprising patients with periventricular nodular heterotopia and healthy persons. A senior neuroradiologist reviewed all clinical images and classified them as patients with focal cortical dysplasia (n = 16) or control subjects (periventricular nodular heterotopia, n = 13; normal, n = 20). Four neuroradiologists reviewed the de-identified and randomized double inversion recovery and magnetization prepared rapid acquired gradient echoes (MPRAGE) sequences for each person and scored them as normal, focal cortical dysplasia, or periventricular nodular heterotopia.

Results: Among individual reviewers, double inversion recovery showed sensitivity from 50% to 88% and specificity from 67% to 91% in detecting focal cortical dysplasia. The sensitivity was notably higher in reviewers with more clinical experience with the technique. Consensus agreement among the three most experienced reviewers gave a sensitivity of 88% (95% confidence interval [CI], 72% to 97%) and specificity of 88% (95% CI, 62% to 98%) for double inversion recovery and sensitivity of 44% (95% CI, 20% to 70%) and specificity of 100% (95% CI, 89% to 100%) for MPRAGE.

Conclusions: Double inversion recovery is sensitive for detection of focal cortical dysplasia with experienced users, particularly when there is consensus agreement. The use of two clinically available magnetic resonance imaging acquisitions-double inversion recovery and another sequence with high specificity such as MPRAGE-would be complementary in the evaluation of lesional epilepsy.
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http://dx.doi.org/10.1016/j.pediatrneurol.2016.04.013DOI Listing
August 2016
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