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Training the New Radiologists: Approaches for Education. Semin Ultrasound CT MR 2024; 45:139-151. [PMID: 38373671 DOI: 10.1053/j.sult.2024.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
The field of Radiology is continually changing, requiring corresponding evolution in both medical student and resident training to adequately prepare the next generation of radiologists. With advancements in adult education theory and a deeper understanding of perception in imaging interpretation, expert educators are reshaping the training landscape by introducing innovative teaching methods to align with increased workload demands and emerging technologies. These include the use of peer and interdisciplinary teaching, gamification, case repositories, flipped-classroom models, social media, and drawing and comics. This publication aims to investigate these novel approaches and offer persuasive evidence supporting their incorporation into the updated Radiology curriculum.
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Workflow interruptions in an era of instant messaging: A detailed analysis. Clin Imaging 2024; 108:110117. [PMID: 38457905 PMCID: PMC10960569 DOI: 10.1016/j.clinimag.2024.110117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 02/29/2024] [Accepted: 03/01/2024] [Indexed: 03/10/2024]
Abstract
INTRODUCTION The complex practice environment and responsibilities incumbent on diagnostic radiologists creates a workflow susceptible to disruption. While interruptions have been shown to contribute to medical errors in the healthcare delivery environment, the exact impact on highly subspecialized services such as diagnostic radiology is less certain. One potential source of workflow disruption is the use of a departmental instant messaging system (Webex), to facilitate communications between radiology faculty, residents, fellows, and technologists. A retrospective review was conducted to quantify the frequency of interruption experienced by our neuroradiology fellows. MATERIALS AND METHODS Data logs were gathered comprising all instant messages sent and received within the designated group chats from July 5-December 31, 2021, during weekday shifts staffed by neuroradiology fellows. Interruptions per shift were calculated based on month, week, and day of the week. RESULTS 14,424 messages were sent across 289 total shifts. The 6 fellows assigned to the main neuroradiology reading room sent 3258 messages and received 10,260 messages from technologists and other staff. There was an average of 50 interruptions per shift when examined by month (range 48-53), and 52 interruptions per shift when examined by day of the week (range 40-60). CONCLUSION Neuroradiology fellows experience frequent interruptions from the departmental instant messaging system. These disruptions, when considered in conjunction with other non-interpretative tasks, may have negative implications for workflow efficiency, requiring iterative process improvements when incorporating new technology into the practice environment of diagnostic radiology.
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Focused Abbreviated Survey MRI Protocols for Brain and Spine Imaging. Radiographics 2023; 43:e220147. [PMID: 37167089 PMCID: PMC10262597 DOI: 10.1148/rg.220147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 10/12/2022] [Accepted: 10/18/2022] [Indexed: 05/13/2023]
Abstract
There has been extensive growth in both the technical development and the clinical applications of MRI, establishing this modality as one of the most powerful diagnostic imaging tools. However, long examination and image interpretation times still limit the application of MRI, especially in emergent clinical settings. Rapid and abbreviated MRI protocols have been developed as alternatives to standard MRI, with reduced imaging times, and in some cases limited numbers of sequences, to more efficiently answer specific clinical questions. A group of rapid MRI protocols used at the authors' institution, referred to as FAST (focused abbreviated survey techniques), are designed to include or exclude emergent or urgent conditions or screen for specific entities. These FAST protocols provide adequate diagnostic image quality with use of accelerated approaches to produce imaging studies faster than traditional methods. FAST protocols have become critical diagnostic screening tools at the authors' institution, allowing confident and efficient confirmation or exclusion of actionable findings. The techniques commonly used to reduce imaging times, the imaging protocols used at the authors' institution, and future directions in FAST imaging are reviewed to provide a practical and comprehensive overview of FAST MRI for practicing neuroradiologists. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.
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Multimodality Imaging of Hamartomas: Interactive Case-based Approach. Radiographics 2023; 43:e220127. [PMID: 36862084 DOI: 10.1148/rg.220127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023]
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Bridging the gap: interactive, case-based learning in radiology education. Abdom Radiol (NY) 2021; 46:5503-5508. [PMID: 34086093 PMCID: PMC8175917 DOI: 10.1007/s00261-021-03147-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 05/06/2021] [Accepted: 05/22/2021] [Indexed: 12/03/2022]
Abstract
Traditional teaching methods in radiology education have not kept pace with advances in technology that foster successful transition into independent practice. This deficit has been exacerbated by the COVID-19 pandemic, as the need for social distancing and the introduction of hybrid staffing models have decreased the critical educational interactions at the reading room workstations between staff and trainees. By leveraging interactive, case-based learning, educators have the opportunity to bridge the substantial gap between basic pattern recognition and successfully making a diagnosis in independent practice. For the educator, this signals a shift away from perfect case selection and presenter authority, and toward the role of a guide facilitating an active case-based learning experience. This form of learning is best accompanied by guided interpretation and iterative feedback with the goal of developing similar levels of mastery and autonomy among graduating trainees. In this article, we present the tools and methods for incorporating interactive cases into existing and novel teaching materials to meet the unique challenges educators are facing today.
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The Updated Neuroradiology Milestones: Synapsing from 1.0 to 2.0. AJNR Am J Neuroradiol 2021; 42:E48-E52. [PMID: 33926899 DOI: 10.3174/ajnr.a7123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The Accreditation Council for Graduate Medical Education is currently in the process of specialty-by-specialty revision of the Milestones. As a result, the Neuroradiology Milestones 2.0 Workgroup was created to refine a system of competency-based assessments for fellow educational growth and development. Strengths of the new Milestones include decreased complexity and uniformity within a subcompetency as it relates to a specific educational development trajectory. The Supplemental Guide serves to decrease clutter in the Milestones 2.0 document and provides a more practical resource for guidance. This article serves to review the history of the Neuroradiology Milestones, followed by a summary of the timeline of events and discussions of the workgroup for development of Neuroradiology Milestones 2.0 and a synopsis of major changes. The plan is for the updated Neuroradiology Milestones to take effect in 2021 or 2022 based on public commentary.
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Factors Influential in the Selection of Radiology Residents in the Post-Step 1 World: A Discrete Choice Experiment. J Am Coll Radiol 2021; 18:1572-1580. [PMID: 34332914 DOI: 10.1016/j.jacr.2021.07.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Revised: 07/06/2021] [Accepted: 07/09/2021] [Indexed: 11/30/2022]
Abstract
OBJECTIVES Reporting of United States Medical Licensing Examination Step 1 results will transition from a numerical score to a pass or fail result. We sought an objective analysis to determine changes in the relative importance of resident application attributes when numerical Step 1 results are replaced. METHODS A discrete choice experiment was designed to model radiology resident selection and determine the relative weights of various application factors when paired with a numerical or pass or fail Step 1 result. Faculty involved in resident selection at 14 US radiology programs chose between hypothetical pairs of applicant profiles between August and November 2020. A conditional logistic regression model assessed the relative weights of the attributes, and odds ratios (ORs) were calculated. RESULTS There were 212 participants. When a numerical Step 1 score was provided, the most influential attributes were medical school (OR: 2.35, 95% confidence interval [CI]: 2.07-2.67), Black or Hispanic race or ethnicity (OR: 2.04, 95% CI: 1.79-2.38), and Step 1 score (OR: 1.8, 95% CI: 1.69-1.95). When Step 1 was reported as pass, the applicant's medical school grew in influence (OR: 2.78, 95% CI: 2.42-3.18), and there was a significant increase in influence of Step 2 scores (OR: 1.31, 95% CI: 1.23-1.40 versus OR 1.57, 95% CI: 1.46-1.69). There was little change in the relative influence of race or ethnicity, gender, class rank, or clerkship honors. DISCUSSION When Step 1 reporting transitions to pass or fail, medical school prestige gains outsized influence and Step 2 scores partly fill the gap left by Step 1 examination as a single metric of decisive importance in application decisions.
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Digital Didactics: Introducing the New ASNR Neuroradiology Fellowship Curriculum. AJNR Am J Neuroradiol 2021; 42:1360-1361. [PMID: 33985950 DOI: 10.3174/ajnr.a7150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Recommendations for Neuroradiology Training during Radiology Residency by the American Society of Neuroradiology Section Chiefs Leadership Group. AJNR Am J Neuroradiol 2021; 42:E7-E9. [PMID: 33541904 DOI: 10.3174/ajnr.a6968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Neuroradiology Fellowship Requirements: Updates in 2019. AJNR Am J Neuroradiol 2020; 41:370-372. [PMID: 32054619 DOI: 10.3174/ajnr.a6450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Reply. AJNR Am J Neuroradiol 2019; 40:E37. [PMID: 31171516 DOI: 10.3174/ajnr.a6094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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ACR Appropriateness Criteria® Ataxia. J Am Coll Radiol 2019; 16:S44-S56. [PMID: 31054758 DOI: 10.1016/j.jacr.2019.02.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 02/08/2019] [Indexed: 01/14/2023]
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Nontraumatic Vascular Emergencies of the Neck. Semin Ultrasound CT MR 2019; 40:157-171. [PMID: 31030739 DOI: 10.1053/j.sult.2018.10.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Nontraumatic vascular emergencies of the head and neck are uncommon, but can occur in patients with central venous catheters, head and neck infections, and in patients with head and neck cancer. Recognizing the imaging findings of vascular complications in these patient populations is critically important to ensure expeditious treatment to avoid significant morbidity and mortality.
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Contrast-Enhanced 3D-FLAIR Imaging of the Optic Nerve and Optic Nerve Head: Novel Neuroimaging Findings of Idiopathic Intracranial Hypertension. AJNR Am J Neuroradiol 2019; 40:334-339. [PMID: 30679213 DOI: 10.3174/ajnr.a5937] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 11/23/2018] [Indexed: 12/19/2022]
Abstract
BACKGROUND AND PURPOSE The sensitivity of contrast-enhanced 3D-FLAIR has not been assessed in patients with idiopathic intracranial hypertension. The purpose of this study was to evaluate whether hyperintensity of the optic nerve/optic nerve head on contrast-enhanced 3D-FLAIR imaging is associated with papilledema in patients with idiopathic intracranial hypertension. MATERIALS AND METHODS A retrospective review was conducted from 2012 to 2015 of patients with clinically diagnosed idiopathic intracranial hypertension and age- and sex-matched controls who had MR imaging with contrast-enhanced 3D-FLAIR. Two neuroradiologists graded each optic nerve/optic nerve head on a scale of 0-3. This grade was then correlated with the Frisén Scale, an ophthalmologic scale used for grading papilledema from 0 (normal) to 5 (severe edema). To estimate the correlation between the MR imaging and Frisén scores, we calculated the Kendall τ coefficient. RESULTS Forty-six patients (3 men, 43 women) with idiopathic intracranial hypertension and 61 controls (5 men, 56 women) with normal findings on MR imaging were included in this study. For both eyes, there was moderate correlation between the 2 scales (right eye: τ = 0.47; 95% CI, 0.31-0.57; left eye: τ = 0.38; 95% CI, 0.24-0.49). Interreader reliability for MR imaging scores showed high interreader reliability (right eye: κ = 0.76; 95% CI, 0.55-0.88; left eye: κ = 0.87; 95% CI, 0.78-0.94). Contrast-enhanced 3D-FLAIR imaging correlates with the Frisén Scale for moderate-to-severe papilledema and less so for mild papilledema. CONCLUSIONS Hyperintensity of the optic nerve/optic nerve head on contrast-enhanced 3D-FLAIR is sensitive for the detection of papilledema in patients with idiopathic intracranial hypertension, which may be useful when prompt diagnosis is crucial.
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Characteristics of Durable Quality Improvement: A 6-Year Case Study. J Am Coll Radiol 2018; 15:1749-1752. [PMID: 30031615 DOI: 10.1016/j.jacr.2018.05.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 05/28/2018] [Indexed: 11/30/2022]
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ACR Appropriateness Criteria® Orbits Vision and Visual Loss. J Am Coll Radiol 2018; 15:S116-S131. [PMID: 29724415 DOI: 10.1016/j.jacr.2018.03.023] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 03/04/2018] [Indexed: 01/22/2023]
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Abstract
Objective 18F-fluoro-deoxy-glucose positron emission tomography/computed tomography (FDG PET/CT) imaging is common in head and neck cancer and often identifies incidental findings that necessitate additional patient evaluations. Our goal was to assess the frequency and nature of these incidental imaging findings on FDG-PET/CT. Study Design Retrospective cohort study. Setting Tertiary medical center. Subjects and Methods All patients with head and neck cancer who had undergone FDG-PET/CT imaging between January 2014 and June 2015 at our institution were evaluated for incidental findings. Results A total of 293 patients met criteria; more than one-third (n = 103) had at least 1 finding unrelated to their head and neck cancer, for a total of 134 incidental findings. Incidental findings within the head and neck (33.5% of all) excluding the thyroid were most common: 35% incidental findings were concerning for malignancy; of these, 25.5% were malignant with further workup. Recommendations were given by the head and neck radiologist on 72 (53.7%) findings: 74.5% of potentially malignant findings and 42.5% of benign findings had recommendations for follow-up. Significantly more patients with findings described as malignant were given recommendations for follow-up ( P = .0004). Conclusion Incidental findings on FDG-PET/CT are present in more than one-third of patients with head and neck cancer. More than one-third of incidental findings were concerning for malignancy. This study illustrates how the incidental findings discovered on FDG PET/CT frequently necessitate additional evaluations unrelated to the index head and neck cancer. The impact of these additional assessments on the cost and quality of health care warrants future evaluation.
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ACR Appropriateness Criteria ® Cranial Neuropathy. J Am Coll Radiol 2017; 14:S406-S420. [DOI: 10.1016/j.jacr.2017.08.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 08/14/2017] [Indexed: 01/09/2023]
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An Enlarging Neck Mass. JAMA Otolaryngol Head Neck Surg 2017; 143:725-726. [PMID: 28472385 DOI: 10.1001/jamaoto.2016.3810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Workflow Dynamics and the Imaging Value Chain: Quantifying the Effect of Designating a Nonimage-Interpretive Task Workflow. Curr Probl Diagn Radiol 2016; 46:275-281. [PMID: 28049559 DOI: 10.1067/j.cpradiol.2016.11.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Revised: 11/10/2016] [Accepted: 11/13/2016] [Indexed: 11/22/2022]
Abstract
PURPOSE To assess the impact of separate non-image interpretive task and image-interpretive task workflows in an academic neuroradiology practice. MATERIALS AND METHODS A prospective, randomized, observational investigation of a centralized academic neuroradiology reading room was performed. The primary reading room fellow was observed over a one-month period using a time-and-motion methodology, recording frequency and duration of tasks performed. Tasks were categorized into separate image interpretive and non-image interpretive workflows. Post-intervention observation of the primary fellow was repeated following the implementation of a consult assistant responsible for non-image interpretive tasks. Pre- and post-intervention data were compared. RESULTS Following separation of image-interpretive and non-image interpretive workflows, time spent on image-interpretive tasks by the primary fellow increased from 53.8% to 73.2% while non-image interpretive tasks decreased from 20.4% to 4.4%. Mean time duration of image interpretation nearly doubled, from 05:44 to 11:01 (p = 0.002). Decreases in specific non-image interpretive tasks, including phone calls/paging (2.86/hr versus 0.80/hr), in-room consultations (1.36/hr versus 0.80/hr), and protocoling (0.99/hr versus 0.10/hr), were observed. The consult assistant experienced 29.4 task switching events per hour. Rates of specific non-image interpretive tasks for the CA were 6.41/hr for phone calls/paging, 3.60/hr for in-room consultations, and 3.83/hr for protocoling. CONCLUSION Separating responsibilities into NIT and IIT workflows substantially increased image interpretation time and decreased TSEs for the primary fellow. Consolidation of NITs into a separate workflow may allow for more efficient task completion.
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Abstract
OBJECTIVE Traumatic orbital encephalocele is a rare but severe complication of orbital roof fractures. We describe 3 cases of orbital encephalocele due to trauma in children. METHODS Retrospective case series from the University of Wisconsin - Madison and Medical College of Wisconsin. RESULTS Three cases of traumatic orbital encephalocele in pediatric patients were found. The mechanism of injury was motor vehicle accident in 2 patients and accidental self-inflicted gunshot wound in 1 patient. All 3 patients sustained orbital roof fractures (4 mm to 19 mm in width) and frontal lobe contusions with high intracranial pressure. A key finding in all 3 cases was progression of proptosis and globe displacement 4 to 11 days after initial injury. On initial CT, all were diagnosed with extraconal hemorrhage adjacent to the roof fractures, with subsequent enlargement of the mass and eventual diagnosis of encephalocele. CONCLUSION Orbital encephalocele is a severe and sight-threatening complication of orbital roof fractures. Post-traumatic orbital encephalocele can be challenging to diagnose on CT as patients with this condition often have associated orbital and intracranial hematoma, which can be difficult to distinguish from herniated brain tissue. When there is a high index of suspicion for encephalocele, an MRI of the orbits and brain with contrast should be obtained for additional characterization. Imaging signs that should raise suspicion for traumatic orbital encephalocele include an enlarging heterogeneous orbital mass in conjunction with a roof fracture and/or widening fracture segments.
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Abstract
Most patients presenting with uncomplicated, nontraumatic, primary headache do not require imaging. When history, physical, or neurologic examination elicits "red flags" or critical features of the headache, then further investigation with imaging may be warranted to exclude a secondary cause. Imaging procedures may be diagnostically useful for patients with headaches that are: associated with trauma; new, worse, or abrupt onset; thunderclap; radiating to the neck; due to trigeminal autonomic cephalgia; persistent and positional; and temporal in older individuals. Pregnant patients, immunocompromised individuals, cancer patients, and patients with papilledema or systemic illnesses, including hypercoagulable disorders may benefit from imaging. Unlike most headaches, those associated with cough, exertion, or sexual activity usually require neuroimaging with MRI of the brain with and without contrast to exclude potentially underlying pathology before a primary headache syndrome is diagnosed. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.
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Simultaneous, unilateral plugging of superior and posterior semicircular canal dehiscences to treat debilitating hyperacusis. J Laryngol Otol 2014; 128:174-8. [PMID: 24480590 PMCID: PMC4340474 DOI: 10.1017/s0022215113003605] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE To describe a case of bilateral superior and posterior semicircular canal dehiscences, and the use of a unilateral transmastoid approach to address both right-sided defects simultaneously. CASE REPORT In a patient with right-sided hyperacusis, bilateral dehiscence of both the superior and the posterior semicircular canals was identified, located adjacent to the common crus, together with a right-sided, anterosuperiorly positioned sigmoid sinus and a high-riding jugular bulb. Results for audiography and cervical vestibular evoked myogenic potential testing were consistent with right-sided semicircular canal dehiscence. At surgery, a right-sided transmastoid approach provided access to plug both defects simultaneously, following posterior mobilisation of the sigmoid sinus. The patient's hyperacusis was completely resolved, with a 10-30 dB improvement in his right ear air conduction hearing, without decrement in bone conduction. CONCLUSION In properly selected patients, a transmastoid approach can be used to effectively manage superior semicircular canal dehiscence and posterior semicircular canal dehiscence simultaneously. Pre-operative computed tomography is recommended to evaluate the dehiscence sites and to identify complicating vascular anatomy.
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Abstract
A quantum repeater is a system for long-distance quantum communication that employs quantum memory elements to mitigate optical fiber transmission losses. The multiplexed quantum memory (O. A. Collins, S. D. Jenkins, A. Kuzmich, and T. A. B. Kennedy, Phys. Rev. Lett. 98, 060502 (2007)) has been shown theoretically to reduce quantum memory time requirements. We present an initial implementation of a multiplexed quantum memory element in a cold rubidium gas. We show that it is possible to create atomic excitations in arbitrary memory element pairs and demonstrate the violation of Bell's inequality for light fields generated during the write and read processes.
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Directing nuclear spin flips in InAs quantum dots using detuned optical pulse trains. PHYSICAL REVIEW LETTERS 2009; 102:167403. [PMID: 19518754 DOI: 10.1103/physrevlett.102.167403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2008] [Indexed: 05/27/2023]
Abstract
We find that detuning an optical pulse train from electronic transitions in quantum dots controls the direction of nuclear spin flips. The optical pulse train generates electron spins that precess about an applied magnetic field, with a spin component parallel to the field only for detuned pulses. This component leads to asymmetry in the nuclear spin flips, providing a way to stabilize and control the nuclear spin polarization. This effect is observed using two-color, time-resolved Faraday rotation and ellipticity.
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Electron and nuclear spin interactions in the optical spectra of single GaAs quantum dots. PHYSICAL REVIEW LETTERS 2001; 86:5176-5179. [PMID: 11384450 DOI: 10.1103/physrevlett.86.5176] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2000] [Indexed: 05/23/2023]
Abstract
Fine and hyperfine splittings arising from electron, hole, and nuclear spin interactions in the magneto-optical spectra of individual localized excitons are studied. We explain the magnetic field dependence of the energy splitting through competition between Zeeman, exchange, and hyperfine interactions. An unexpectedly small hyperfine contribution to the splitting close to zero applied field is described well by the interplay between fluctuations of the hyperfine field experienced by the nuclear spin and nuclear dipole/dipole interactions.
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Abstract
Nuclear magnetic resonance (NMR) from constituent Ga and As nuclei was optically detected on excitonic recombination in single GaAs quantum dots formed by interface fluctuations in GaAs/Al0.3Ga0.7As quantum wells. Orientation of the nuclear spin system by optical pumping causes an Overhauser shift of the excitonic energy levels proportional to the degree of nuclear orientation. NMR was subsequently detected by monitoring changes in the combined Overhauser plus Zeeman splitting of excitons localized in single quantum dots as the RF frequency was swept through a nuclear resonance. The NMR signals originate from approximately 10(5) nuclei in the quantum dot-with dimensions of approximately 4 nm X 10 nm X 100 nm--illustrating the extreme sensitivity and spatial resolution of the technique. NMR from such small structures provides a chemically specific probe of the local environment on the nanometer scale.
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Spectrally resolved Overhauser shifts in single GaAs/AlxGa1-xAs quantum dots. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:R17339-R17342. [PMID: 9985952 DOI: 10.1103/physrevb.54.r17339] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Squeezing of cw light in a single-mode dispersive chi (2) medium. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1996; 54:4396-4407. [PMID: 9913991 DOI: 10.1103/physreva.54.4396] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Nonequilibrium Green-function theory of quantum-optical correlations. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1996; 53:3497-3513. [PMID: 9913293 DOI: 10.1103/physreva.53.3497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Symmetry and electronic structure of the Mn impurity in ZnS nanocrystals. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:14356-14359. [PMID: 9980758 DOI: 10.1103/physrevb.52.r14356] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Entrainment of solid-state laser arrays. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1995; 52:1500-1506. [PMID: 9912389 DOI: 10.1103/physreva.52.1500] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Correlation-function hierarchies in nonlinear quantum optics. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1995; 52:742-753. [PMID: 9912299 DOI: 10.1103/physreva.52.742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Optically detected magnetic resonance of GaN films grown by organometallic chemical-vapor deposition. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:13326-13336. [PMID: 9978136 DOI: 10.1103/physrevb.51.13326] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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39
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Investigation of the role of cysteines in catalysis by prostaglandin endoperoxide synthase. J Biol Chem 1994; 269:27357-64. [PMID: 7961646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The importance of cysteine residues in the cyclooxygenase activity of prostaglandin endoperoxide synthase (PGHS) was investigated using cysteine-specific reagents and site-directed mutagenesis. N-(7-Dimethyl-amino-4-methyl-3-coumarinyl)maleimide (DACM), a hydrophobic maleimide, inactivated both cyclooxygenase and peroxidase activities of apoPGHS in a time-dependent manner but did not affect holoPGHS. Heme titration experiments indicated that modification of apoPGHS with DACM prevented heme binding. Peptide mapping revealed that DACM modified Cys313, Cys512, and Cys540. N-Ethylmaleimide inactivated cyclooxygenase and peroxidase activities of holoPGHS in a time-dependent manner but did not affect apoPGHS. Peptide mapping demonstrated that N-ethylmaleimide reacted primarily with Cys313 in holoPGHS and with Cys540 in apoPGHS. Each of the 3 cysteines was changed to serine by site-directed mutagenesis, and the mutant proteins were expressed in COS-1 cells. The C512S mutant converted arachidonic acid to products to the same extent as wild-type PGHS. In contrast, the C313S and C540S mutants converted arachidonic acid to products to the extent of 10% of wild-type PGHS. These results indicate that Cys313, Cys512, and Cys540 are not essential for cyclooxygenase activity but that alteration of Cys540 or Cys313 dramatically decreases enzyme activity. Both residues are well removed from the cyclooxygenase and peroxidase active sites so our findings reveal that subtle changes, such as substitution of a single oxygen for sulfur atom as far as 30 A from the heme prosthetic group, can significantly alter enzyme activity.
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Nonlinear dynamics of dual-frequency-pumped multiwave mixing in optical fibers. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1994; 50:1732-1747. [PMID: 9911066 DOI: 10.1103/physreva.50.1732] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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41
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Conservation law for multiple four-wave-mixing processes in a nonlinear optical medium. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1994; 50:1807-1813. [PMID: 9911074 DOI: 10.1103/physreva.50.1807] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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42
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Optically detected magnetic resonance of shallow donors in GaAs. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:17031-17034. [PMID: 10008304 DOI: 10.1103/physrevb.48.17031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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43
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Optically detected magnetic resonance in zinc-doped indium phosphide under uniaxial stress. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:14157-14160. [PMID: 10007830 DOI: 10.1103/physrevb.48.14157] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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44
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45
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Many-body quantum theory of the optical parametric oscillator. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1993; 48:2374-2385. [PMID: 9909862 DOI: 10.1103/physreva.48.2374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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46
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Optical multiwave mixing: Dark solitary wave trains and quasiperiodic dynamics. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1993; 47:1252-1262. [PMID: 9909050 DOI: 10.1103/physreva.47.1252] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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47
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Photoluminescence and optically detected magnetic resonance of Si/Si1-xGex strained-layer superlattices grown by molecular-beam epitaxy. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 47:1305-1315. [PMID: 10006140 DOI: 10.1103/physrevb.47.1305] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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48
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Photon-number measurements with cold atoms. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1993; 47:566-570. [PMID: 9908950 DOI: 10.1103/physreva.47.566] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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49
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Spectral analysis of the protein-derived tyrosyl radicals from prostaglandin H synthase. J Biol Chem 1992; 267:23583-8. [PMID: 1331091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We have analyzed the low temperature EPR spectra of the protein-derived tyrosyl radicals detected upon addition of arachidonic acid or 5-phenyl-4-pentenyl-1-hydroperoxide (PPHP) to prostaglandin H synthase. With either arachidonic acid or PPHP the initial radical detected is a doublet (peak-to-trough = 35 Gauss) that disappears rapidly and is replaced by a broad singlet (peak-to-trough = 30 Gauss) followed by a narrow singlet (peak-to-trough = 26.5 Gauss). The relative amounts of these signals vary with time and concentration of arachidonic acid. The three tyrosyl radical signals were subjected to computer simulation and power saturation analysis. The data establish that there are only two distinct tyrosyl radical species, the doublet and the narrow singlet. The broad singlet seen at intermediate times and at low arachidonic acid concentrations is a composite of the doublet and the narrow singlet. The composition of the broad singlet in incubations of prostaglandin H synthase with 0.5 mM arachidonic acid is approximately 40% doublet and 60% singlet. The broad singlet signal does not represent a distinct tyrosyl radical species.
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31P electron-nuclear double resonance of the PIn antisite in InP:Zn detected via luminescence. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 46:1377-1381. [PMID: 10003779 DOI: 10.1103/physrevb.46.1377] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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