Cumulative polarization in conductive interfacial ferroelectrics.

Ferroelectricity in atomically thin bilayer structures has been recently predicted1 and measured2-4 in two-dimensional materials with hexagonal non-centrosymmetric unit-cells. The crystal symmetry translates lateral shifts between parallel two-dimensional layers to sign changes in their out-of-plane electric polarization, a mechanism termed 'slide-tronics'4. These observations have been restricted to switching between only two polarization states under low charge carrier densities5-12, limiting the practical application of the revealed phenomena13. To overcome these issues, one should explore the nature of polarization in multi-layered van der Waals stacks, how it is governed by intra- and interlayer charge redistribution and to what extent it survives the addition of mobile charge carriers14. To explore these questions, we conduct surface potential measurements of parallel WSe2 and MoS2 multi-layers with aligned and anti-aligned configurations of the polar interfaces. We find evenly spaced, nearly decoupled potential steps, indicating highly confined interfacial electric fields that provide a means to design multi-state 'ladder-ferroelectrics'. Furthermore, we find that the internal polarization remains notable on electrostatic doping of mobile charge carrier densities as high as 1013 cm-2, with substantial in-plane conductivity. Using density functional theory calculations, we trace the extra charge redistribution in real and momentum spaces and identify an eventual doping-induced depolarization mechanism.

Visualizing Poiseuille flow of hydrodynamic electrons.

Hydrodynamics, which generally describes the flow of a fluid, is expected to hold even for fundamental particles such as electrons when inter-particle interactions dominate1. Although various aspects of electron hydrodynamics have been revealed in recent experiments2-11, the fundamental spatial structure of hydrodynamic electrons-the Poiseuille flow profile-has remained elusive. Here we provide direct imaging of the Poiseuille flow of an electronic fluid, as well as a visualization of its evolution from ballistic flow. Using a scanning carbon nanotube single-electron transistor12, we image the Hall voltage of electronic flow through channels of high-mobility graphene. We find that the profile of the Hall field across the channel is a key physical quantity for distinguishing ballistic from hydrodynamic flow. We image the transition from flat, ballistic field profiles at low temperatures into parabolic field profiles at elevated temperatures, which is the hallmark of Poiseuille flow. The curvature of the imaged profiles is qualitatively reproduced by Boltzmann calculations, which allow us to create a 'phase diagram' that characterizes the electron flow regimes. Our results provide direct confirmation of Poiseuille flow in the solid state, and enable exploration of the rich physics of interacting electrons in real space.

Mid-Infrared Mapping of Four-Layer Graphene Polytypes Using Near-Field Microscopy.

The mid-infrared (MIR) spectral region attracts attention for accurate chemical analysis using photonic devices. Few-layer graphene (FLG) polytypes are promising platforms, due to their broad absorption in this range and gate-tunable optical properties. Among these polytypes, the noncentrosymmetric ABCB/ACAB structure is particularly interesting, due to its intrinsic bandgap (8.8 meV) and internal polarization. In this study, we utilize scattering-scanning near-field microscopy to measure the optical response of all three tetralayer graphene polytypes in the 8.5-11.5 µm range. We employ a finite dipole model to compare these results to the calculated optical conductivity for each polytype obtained from a tight-binding model. Our findings reveal a significant discrepancy in the MIR optical conductivity response of graphene between the different polytypes than what the tight-binding model suggests. This observation implies an increased potential for utilizing the distinct tetralayer polytypes in photonic devices operating within the MIR range for chemical sensing and infrared imaging.

Violation of expectations is correlated with satisfaction following hip arthroscopy.

PURPOSE: The mechanism by which preoperative expectations may be associated with patient satisfaction and procedural outcomes following hip preservation surgery (HPS) is far from simple or linear. The purpose of this study is to better understand patient expectations regarding HPS and their relationship with patient-reported outcomes (PROs) and satisfaction using machine learning (ML) algorithms. METHODS: Patients scheduled for hip arthroscopy completed the Hip Preservation Surgery Expectations Survey (HPSES) and the pre- and a minimum 2 year postoperative International Hip Outcome Tool (iHOT-33). Patient demographics, including age, gender, occupation, and body mass index (BMI), were also collected. At the latest follow-up, patients were evaluated for subjective satisfaction and postoperative complications. ML algorithms and standard statistics were used. RESULTS: A total of 69 patients were included in this study (mean age 33.7 ± 13.1 years, 62.3% males). The mean follow-up period was 27 months. The mean HPSES score, patient satisfaction, preoperative, and postoperative iHOT-33 were 83.8 ± 16.5, 75.9 ± 26.9, 31.6 ± 15.8, and 73 ± 25.9, respectively. Fifty-nine patients (86%) reported that they would undergo the surgery again, with no significant difference with regards to expectations. A significant difference was found with regards to expectation violation (p < 0.001). Expectation violation scores were also found to be significantly correlated with satisfaction. CONCLUSION: ML algorithms utilized in this study demonstrate that violation of expectations plays an important predictive role in postoperative outcomes and patient satisfaction and is associated with patients' willingness to undergo surgery again. LEVEL OF EVIDENCE: IV.

Preoperative Expectations Do Not Correlate With Postoperative iHOT-33 Scores and Patient Satisfaction Following Hip Arthroscopy for the Treatment of Femoroacetabular Impingement Syndrome.

PURPOSE: To examine the correlation between preoperative patient expectation and International Hip Outcome Tool (iHOT-33) score and postoperative satisfaction of patients undergoing hip arthroscopy for the treatment of femoroacetabular impingement syndrome. METHODS: Patients scheduled for surgery completed the Hip Preservation Surgery Expectations Survey (HPSES), as well as the preoperative and a minimum 2-year postoperative iHOT-33. Patient demographics that were collected included gender, age, occupation, and body mass index (BMI). At the latest follow-up, patients were evaluated for their subjective satisfaction and postoperative complications. An in-depth analysis was performed to assess the correlation between HPSES, iHOT-33, and patient satisfaction. RESULTS: Sixty-nine patients (62.3% males; mean age: 33.7 ± 13.1 years; BMI: 23.9 ± 3.5 kg/m2) were included in this study. The mean HPSES score was 83.8 ± 16.5. The mean iHOT-33 improved from 31.6 ± 15.8 preoperatively to 73 ± 25.9 postoperatively (95% CI = 35.2,47.8; P < .01), and the mean patient satisfaction was 75.9 ± 26.9. There were no statistically significant differences in mean HPSES score between males and females (95% CI = 79.9,87.8; P = .35) nor between different occupational groups (95% CI = 79.4,87.6, P = .095). No correlation was found between age and HPSES score (r = .036; P =.76). There was a negligible correlation between HPSES score and postoperative iHOT-33 score (r = -.117; P = .34) and patient satisfaction (r = -.042; P = .73). Postoperative iHOT-33 score had a significant high correlation with patient satisfaction (r = .8; P < .001). CONCLUSION: Preoperative expectations do not correlate with postoperative iHOT-33 scores and patient satisfaction with surgery at 2 years after surgery. Gender and occupation did not differ significantly with regard to preoperative expectations, and there was no correlation between age and HPSES score. LEVEL OF EVIDENCE: IV, retrospective case series.

Quantum Hall Response to Time-Dependent Strain Gradients in Graphene.

Mechanical deformations of graphene induce a term in the Dirac Hamiltonian that is reminiscent of an electromagnetic vector potential. Strain gradients along particular lattice directions induce local pseudomagnetic fields and substantial energy gaps as indeed observed experimentally. Expanding this analogy, we propose to complement the pseudomagnetic field by a pseudoelectric field, generated by a time-dependent oscillating stress applied to a graphene ribbon. The joint Hall-like response to these crossed fields results in a strain-induced charge current along the ribbon. We analyze in detail a particular experimental implementation in the (pseudo)quantum Hall regime with weak intervalley scattering. This allows us to predict an (approximately) quantized Hall current that is unaffected by screening due to diffusion currents.

Impact of COVID-19 on emergency medical services utilization and severity in the U.S. Upper Midwest.

The COVID-19 pandemic has claimed over one million lives in the United States and has drastically changed how patients interact with the healthcare system. Emergency medical services (EMS) are essential for emergency response, disaster preparedness, and responding to everyday emergencies. We therefore examined differences in EMS utilization and call severity in 2020 compared to trends from 2015-2019 in a large, multi-state advanced life support EMS agency serving the U.S. Upper Midwest. Specifically, we analyzed all emergency calls made to Mayo Clinic Ambulance, the sole advanced life support EMS provider serving a large area in Minnesota and Wisconsin, and compared the number of emergency calls made in 2020 to the number of calls expected based on trends from 2015-2019. We similarly compared caller demographics, call severity, and proportions of calls made for overdose/intoxication, behavioral health, and motor vehicle accidents. Subgroup analyses were performed for rural vs. urban areas. We identified 262,232 emergent EMS calls during 2015-2019 and 53,909 calls in 2020, corresponding to a decrease of 28.7% in call volume during 2020. Caller demographics shifted slightly towards older patients (mean age 59.7 [SD, 23.0] vs. 59.1 [SD, 23.7] years; p<0.001) and to rural areas (20.4% vs. 20.0%; p = 0.007). Call severity increased, with 95.3% of calls requiring transport (vs. 93.8%; p<0.001) and 1.9% resulting in death (vs. 1.6%; p<0.001). The proportion of calls for overdose/intoxication increased from 4.8% to 5.5% (p<0.001), while the proportion of calls for motor vehicle collisions decreased from 3.9% to 3.0% (p<0.001). All changes were more pronounced in urban areas. These findings underscore the extent to which the COVID-19 pandemic impacted healthcare utilization, particularly in urban areas, and suggest that patients may have delayed calling EMS with potential implications on disease severity and risk of death.

Clinical Predictors of Overall Survival in Very Elderly Patients With Glioblastoma: A National Cancer Database Multivariable Analysis.

BACKGROUND AND OBJECTIVES: Surgery for the very elderly is a progressively important paradigm as life expectancy continues to rise. Patients with glioblastoma multiforme often undergo surgery, radiotherapy (RT), and chemotherapy (CT) to prolong overall survival (OS). However, the efficacy of these treatment modalities in patients aged 80 years and older has yet to be fully assessed in the literature. METHODS: The National Cancer Database was used to retrospectively identify patients aged 65 years and older with glioblastoma multiforme (1989-2016). All available patient demographic characteristics, disease characteristics, and clinical outcomes were collected. To study OS, bivariable survival models were created using Kaplan-Meier estimates. A Cox proportional-hazards model was used for final adjusted analyses. RESULTS: A total of 578 very elderly patients (aged 80 years and older) and 2836 elderly patients (aged 65-79 years) were identified. Compared with elderly patients, very elderly patients were more likely to have Medicare (odds ratio [OR] 1.899 [95% CI: 1.417-2.544], P < .001) while less likely to have private insurance status (OR 0.544 [95% CI: 0.401-0.739], P < .001). In addition, very elderly patients were more likely to travel the least distance for treatment and have multiple tumors (P < .001). When controlling for demographic and disease characteristics, very elderly patients were less likely to receive gross total resection (GTR) (OR 0.822 [95% CI: 0.681-0.991], P < .041), RT (OR 0.385 [95% CI: 0.319-0.466], P < .001), or postoperative CT (OR 0.298 [95% CI: 0.219-0.359], P < .001) relative to elderly counterparts. Within very elderly patients, GTR, RT, and CT all independently and significantly predicted improved OS (P < .001 for all). These predictive models were deployed in an online calculator (https://spine.shinyapps.io/GBM_elderly). CONCLUSION: Very elderly patients are less likely to receive GTR, RT, or CT when compared with elderly counterparts despite use of these therapies conferring improved OS. Selected very elderly patients may benefit from more aggressive attempts at surgical and adjuvant treatment.

Stem Cells in the Treatment of Spinal Cord Injury: A Review of Currently Registered Clinical Trials.

BACKGROUND: Spinal cord injury (SCI) affects around 18,000 individuals annually, representing nearly one-third of all paralysis cases. Stem cell therapy, a focal point in contemporary neuroregeneration research for SCI treatment, holds potential in leveraging undifferentiated stem cells to regenerate damaged tissues. This study seeks to comprehensively analyze current clinical trials exploring the potential use of stem cells in treating spinal cord injuries. METHODS: A data retrieval approach examined the ClinicalTrials.gov database using the terms "spinal cord injury" and "stem cells." Exclusion criteria eliminated studies not recruiting, terminated prematurely, suspended, withdrawn, or of unknown status. Data for each trial, including ClinicalTrial.gov NCT identifier, title, intervention details, initiation/completion dates, and sample size, were systematically collected. Literature searches on PubMed.gov were conducted for completed trials with results. RESULTS: Thirty clinical trials were analyzed, with 20 completed and six with published results on PubMed.gov. Interventions included 20 biological (66.7%), 6 procedural (20%), and 4 drug interventions (13.3%). Stem cell sources varied, including bone marrow (46.7%), umbilical cells (20%), adipose tissue (20%), embryonic cells (6.7%), and neural cells (6.7%). Trials spanned 2005 to 2022, with 11 (36.7%) commencing in or after 2017. Among six trials with results, 50% used bone marrow-derived stem cells. CONCLUSIONS: The promising potential of stem cells in neuroregenerative SCI treatment necessitates further exploration through large-scale, multicenter clinical trials to enhance understanding and guide wider adoption of this emerging treatment paradigm.

Polarization Saturation in Multilayered Interfacial Ferroelectrics.

Van der Waals polytypes of broken inversion and mirror symmetries  have been recently shown to exhibit switchable electric polarization even at the ultimate two-layer thin limit. Their out-of-plane polarization has been found to accumulate in a ladder-like fashion with each successive layer, offering 2D building blocks for the bottom-up construction of 3D ferroelectrics. Here, it is demonstrated experimentally that beyond a critical stack thickness, the accumulated polarization in rhombohedral polytypes of molybdenum disulfide saturates. The underlying saturation mechanism, deciphered via density functional theory and self-consistent Poisson-Schrödinger calculations, point to a purely electronic redistribution involving: 1. Polarization-induced bandgap closure that allows for cross-stack charge transfer and the emergence of free surface charge; 2. Reduction of the polarization saturation value, as well as the critical thickness at which it is obtained, by the presence of free carriers. The resilience of polar layered structures to atomic surface reconstruction, which is essentially unavoidable in polar 3D crystals, potentially allows for the design of new devices with mobile surface charges. The findings, which are of general nature, should be accounted for when designing switching and/or conductive devices based on ferroelectric layered materials.

Fractionated radiotherapy after gross-total resection of spinal chordoma: a systematic review of survival outcomes using individualized patient data.

OBJECTIVE: Spinal chordoma treatment guidelines recommend resection. However, in patients in whom gross-total resection (GTR) is achieved, the benefits of radiation therapy (RT) are unclear. Therefore, the authors performed a systematic review to determine if RT is associated with postoperative progression-free survival (PFS) or overall survival (OS) after achieving GTR of spinal chordoma. METHODS: The PubMed database was searched for studies including individualized data of patients undergoing GTR with or without RT for spinal chordoma. Patients < 18 years of age or those who underwent stereotactic body RT were excluded. Qualitative assessment was performed using Newcastle-Ottawa Scale guidelines. Log-rank tests for time-to-event data and a Cox proportional-hazards model were generated for a multivariable statistical model. RESULTS: Complete data of 132 patients were retrieved, with 37 (28%) patients receiving adjuvant RT and 95 (72%) not receiving adjuvant RT. The mean follow-up was not statistically significantly different between those undergoing RT and not undergoing RT (54.02 months and 65.43 months, respectively). Patients were more likely not to undergo RT if their disease was located in the sacrum versus the mobile spine (p < 0.001). When controlling for age ≥ 65 years, male sex, disease location, and treatment year ≥ 2010, patients undergoing RT had similar PFS and OS when compared with those not undergoing RT on multivariable survival analysis (HR 0.935 [95% CI 0.703-2.340], p = 0.844 and HR 2.078 [95% CI 0.848-5.090], p = 0.110, respectively). However, age ≥ 65 years was associated with poorer OS in adjusted analyses (HR 2.761 [95% CI 1.185-6.432], p = 0.018) relative to patients < 65 years of age. CONCLUSIONS: After achieving GTR of spinal chordoma, the utility of RT on PFS and OS remains unclear. Age ≥ 65 years appears to be associated with OS in spinal chordoma patients. Additional multicenter prospective studies are needed to determine the utility of RT in this patient population.

Glycemic outcomes and patient satisfaction and self-management improves in transition from standard to virtual multidisciplinary care.

AIMS: With advances in cloud-based technologies, there has been a rise in remote T1D care. We hypothesized that transitioning T1DM care to a virtual, multidisciplinary clinic could improve measures beyond HbA1c. METHODS: To assess the impact of transitioning from standard to virtual T1DM care, we evaluated glycemic measures and patient reported outcomes. RESULTS: Sixty-one adults with T1DM were included, with mean age 40.2 ± 13.5 years and diabetes duration 16.9 ± 9.0 years. Most patients were treated with insulin pumps and CGM. The number of annual diabetes care encounters rose from 2.1 ± 4.2 to 12.8 ± 5.5. Baseline HbA1c was 7.9 ± 1.6 %(63 ± 16.9 mmol/mol), declining to 7.3 ± 1.1 %(56 ± 8.5 mmol/mol) and 7.1 ± 1.0 %(54 ± 7.7 mmol/mol) at 6 and 12 months respectively (p < 0.001 for both). In parallel, TIR improved from 63.1 ± 19.3 % to 69.2 ± 13.8 % (p < 0.001) and 67.5 ± 19.4 % (p = 0.03) at 6 and 12 months respectively, while TBR declined. Scores from validated diabetes treatment and self-management questionnaires rose significantly and these rises were associated with a reduction in HbA1c, the latter score was also associated with increased TIR. There was a trend toward a correlation between encounter frequency and improvement in HbA1c and TIR. CONCLUSIONS: Transitioning from standard to virtual, coordinated, multidisciplinary T1DM care is associated with increased visit frequency, improving glycemic control, treatment satisfaction and self-care behaviors.

Utilizing Neuromodulation in the Treatment of Spinal Cord Injury: An Assessment of Clinical Trials from the National ClinicalTrials.gov Database.

OBJECTIVE: Spinal cord injury (SCI) is responsible for approximately 18,000 trauma cases each year in the United States, often resulting in debilitating motor and autonomic disability. Neuromodulation is a rapidly growing field of interest in the neurosurgical field and has additionally shown promise in the treatment of SCI. This review characterizes all clinical trials to date studying neuromodulation for the treatment of SCI. METHODS: The ClinicalTrials.gov database was queried using the search terms "neuromodulation" and "spinal cord injury" on ClinicalTrials.gov. Trials were excluded if they were not yet recruiting, suspended, terminated early, or of unknown status. RESULTS: In total, 33 clinical trials were included in this study. Of the 33 trials, 8 were completed and 1 had published results. Most trials studied deficits of motor function (60%) and bladder control (37%). Fourteen studies (42.4%) utilized transcutaneous spinal stimulation, 7 (21.2%) utilized epidural electrical stimulation, and 6 (18.2%) utilized tibial nerve stimulation. There was an uptrend of clinical trials studying SCI indexed on PubMed, which was comparable to the increased number of publications indexed overall (Pearson correlation, P < 0.001). Of these, only 1 study regarding home tibial nerve stimulation for neurogenic bladder had published data, which was performed with no adverse events. CONCLUSIONS: Neuromodulation in SCI studies currently assess transcutaneous spinal stimulation, epidural electrical stimulation, and tibial nerve stimulation. There is currently 1 completed study suggesting feasibility of home neuromodulation techniques without adverse events. The results of trials that will be completed in the next few years will help dictate the potential of neuromodulation as a treatment for SCI.

Endoscopic Rhizotomy for Facetogenic Back Pain: A Review of the History, Financial Considerations, Patient Selection Criteria, and Clinical Outcomes.

BACKGROUND: Chronic back pain (CBP) is a condition that places a considerable burden on society, with several million people affected in the United States alone. Treatment options to address this problem and relieve CBP are constantly evolving, and one of the most promising treatment modalities for CBP that is refractory to conservative treatment options is endoscopic rhizotomy (ER). METHODS: A thorough search of the PubMed (MEDLINE) database was conducted to assess the full progression of ER from its earliest uses to present day in a historical narrative review of ER, with treatment of facetogenic pain as a model pathology. RESULTS: ER allows for direct visualization and ablation of sensory branches of the dorsal ramus to provide pain relief in up to 80% of patients faced with refractory CBP. This technique has been built upon since the early 20th century, and the novel endoscopic approach continues to gain popularity among physicians. Benefits of ER include superior postoperative median pain-free duration compared with traditional percutaneous radiofrequency ablation, as well as direct visualization of regional anatomy. Patient selection criteria for the procedure and a modest list of contraindications allow the use of ER as a viable treatment option for a significant population of patients suffering from CBP. Potential barriers to ER include high cost of the procedure, longer intraoperative time, and expensive proprietary equipment. CONCLUSIONS: ER is an effective treatment for refractory CBP with notable advantages. As the technology and popularity of this procedure progress, improvements in the cost, training, and intraoperative time may make it a favorable alternative to the current standard of care.

Treatment with Pulsed Extremely Low Frequency Electromagnetic Field (PELF-EMF) Exhibit Anti-Inflammatory and Neuroprotective Effect in Compression Spinal Cord Injury Model.

BACKGROUND: Spinal cord injury (SCI) pathology includes both primary and secondary events. The primary injury includes the original traumatic event, and the secondary injury, beginning immediately after the initial injury, involves progressive neuroinflammation, neuronal excitotoxicity, gliosis, and degeneration. Currently, there is no effective neuroprotective treatment for SCI. However, an accumulating body of data suggests that PELF-EMF has beneficial therapeutic effects on neurotrauma. The purpose of this study was to test the efficacy of the PELF-EMF SEQEX device using a compression SCI mouse model. METHODS: C57BL/6 mice were exposed to PELF-EMF for 4 h on a daily basis for two months, beginning 2 h after a mild-moderate compression SCI. RESULTS: The PELF-EMF treatment significantly diminished inflammatory cell infiltration and astrocyte activation by reducing Iba1, F4/80, CD68+ cells, and GAFP at the lesion borders, and increased pro-survival signaling, such as BDNF, on the neuronal cells. Moreover, the treatment exhibited a neuroprotective effect by reducing the demyelination of the axons of the white matter at the lesion's center. CONCLUSIONS: Treatment with SEQEX demonstrated significant anti-inflammatory and neuroprotective effects. Considering our results, this safe and effective rehabilitative device, already available on the market, may provide a major therapeutic asset in the treatment of SCI.

Blood glutamate scavengers increase pro-apoptotic signaling and reduce metastatic melanoma growth in-vivo.

Inhibition of extracellular glutamate (Glu) release decreases proliferation and invasion, induces apoptosis, and inhibits melanoma metastatic abilities. Previous studies have shown that Blood-glutamate scavenging (BGS), a novel treatment approach, has been found to be beneficial in attenuating glioblastoma progression by reducing brain Glu levels. Therefore, in this study we evaluated the ability of BGS treatment to inhibit brain metastatic melanoma progression in-vivo. RET melanoma cells were implanted in C56BL/6J mice to induce brain melanoma tumors followed by treatment with BGS or vehicle administered for fourteen days. Bioluminescent imaging was conducted to evaluate tumor growth, and plasma/CSF Glu levels were monitored throughout. Immunofluorescence staining of Ki67 and 53BP1 was used to analyze tumor cell proliferation and DNA double-strand breaks. In addition, we analyzed CD8, CD68, CD206, p-STAT1 and iNOS expression to evaluate alterations in tumor micro-environment and anti-tumor immune response due to treatment. Our results show that BGS treatment reduces CSF Glu concentration and consequently melanoma growth in-vivo by decreasing tumor cell proliferation and increasing pro-apoptotic signaling in C56BL/6J mice. Furthermore, BGS treatment supported CD8+ cell recruitment and CD68+ macrophage invasion. These findings suggest that BGS can be of potential therapeutic relevance in the treatment of metastatic melanoma.

Neurological symptoms due to Coronavirus disease 2019.

In this review, we focus on summarizing everything that is known about the neurological effects of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-COV-2). It has been shown that Coronavirus Disease 2019 (Covid-19) may result in neuromuscular disorders or damage to nerves outside of the brain and spinal cord, which may lead to weakness, numbness, and pain. Published literature has stated that SARS-COV-1 may infect the central nervous system and due to its similarities to SARS-COV-2, we suspect that SARS-COV-2 has the same potential. We conclude that Covid-19 has neurological manifestations. Further research should be done in this field to understand the full extent of this virus.

Simultaneous voltage and current density imaging of flowing electrons in two dimensions.

A variety of physical phenomena associated with nanoscale electron transport often results in non-trivial spatial voltage and current patterns, particularly in nonlocal transport regimes. While numerous techniques have been devised to image electron flows, the need remains for a nanoscale probe capable of simultaneously imaging current and voltage distributions with high sensitivity and minimal invasiveness, in a magnetic field, across a broad range of temperatures and beneath an insulating surface. Here we present a technique for spatially mapping electron flows based on a nanotube single-electron transistor, which achieves high sensitivity for both voltage and current imaging. In a series of experiments using high-mobility graphene devices, we demonstrate the ability of our technique to visualize local aspects of intrinsically nonlocal transport, as in ballistic flows, which are not easily resolvable via existing methods. This technique should aid in understanding the physics of two-dimensional electronic devices and enable new classes of experiments that image electron flow through buried nanostructures in the quantum and interaction-dominated regimes.