Interlayer donor-acceptor pair excitons in MoSe2/WSe2 moiré heterobilayer.

Localized interlayer excitons (LIXs) in two-dimensional moiré superlattices exhibit sharp and dense emission peaks, making them promising as highly tunable single-photon sources. However, the fundamental nature of these LIXs is still elusive. Here, we show the donor-acceptor pair (DAP) mechanism as one of the origins of these excitonic peaks. Numerical simulation results of the DAP model agree with the experimental photoluminescence spectra of LIX in the moiré MoSe2/WSe2 heterobilayer. In particular, we find that the emission energy-lifetime correlation and the nonmonotonic power dependence of the lifetime agree well with the DAP IX model. Our results provide insight into the physical mechanism of LIX formation in moiré heterostructures and pave new directions for engineering interlayer exciton properties in moiré superlattices.

Spin Defects in hBN assisted by Metallic Nanotrenches for Quantum Sensing.

The omnipresence of hexagonal boron nitride (hBN) in devices embedding two-dimensional materials has prompted it as the most sought after platform to implement quantum sensing due to its testing while operating capability. The negatively charged boron vacancy (VB-) in hBN plays a prominent role, as it can be easily generated while its spin population can be initialized and read out by optical means at room-temperature. But the lower quantum yield hinders its widespread use as an integrated quantum sensor. Here, we demonstrate an emission enhancement amounting to 400 by nanotrench arrays compatible with coplanar waveguide (CPW) electrodes employed for spin-state detection. By monitoring the reflectance spectrum of the resonators as additional layers of hBN are transferred, we have optimized the overall hBN/nanotrench optical response, maximizing thereby the luminescence enhancement. Based on these finely tuned heterostructures, we achieved an enhanced DC magnetic field sensitivity as high as 6 × 10-5 T/Hz1/2.

Which Types of Facebook Posts Yield the Best Response for Radiology Education: A One-Year Analysis of What We Learned.

RATIONALE AND OBJECTIVES: We post several times daily on our Facebook page, CTisus, to educate radiology students and professionals globally. We aimed to determine how our data compared for different types of posts and ascertain the popularity of videos versus case images, illustrations versus case images, and whether cinematic rendering performed better than traditional computed tomography. MATERIALS AND METHODS: We exported data for one year's worth of Facebook posts (November 1, 2020 to October 31, 2021) and categorized posts into 18 types. Our primary outcome was popularity of each post, measured by "reach" and "engagement" counts provided by Facebook. RESULTS: Among the 9057 posts exported, "just for fun" posts performed the best, followed by quiz images. Case images performed significantly better than instructional videos (p < 0.0001). However, the opposite was true for engagement, where instructional videos performed significantly better than case images (p = 0.0012). For both reach and engagement, case images performed better than medical illustrations (p < 0.0001). For both reach (p < 0.0005) and engagement (p < 0.0001), traditional computed tomography performed significantly better than cinematic rendering. All video types had better engagement than case images and medical illustrations (p < 0.0001) and both had significantly better engagement than text (p < 0.0001). CONCLUSION: Our results may help other educators choose what types of content to create and post on social media to achieve the best impact on learners.

External Validation of Deep Learning Algorithms for Radiologic Diagnosis: A Systematic Review.

Purpose: To assess generalizability of published deep learning (DL) algorithms for radiologic diagnosis. Materials and Methods: In this systematic review, the PubMed database was searched for peer-reviewed studies of DL algorithms for image-based radiologic diagnosis that included external validation, published from January 1, 2015, through April 1, 2021. Studies using nonimaging features or incorporating non-DL methods for feature extraction or classification were excluded. Two reviewers independently evaluated studies for inclusion, and any discrepancies were resolved by consensus. Internal and external performance measures and pertinent study characteristics were extracted, and relationships among these data were examined using nonparametric statistics. Results: Eighty-three studies reporting 86 algorithms were included. The vast majority (70 of 86, 81%) reported at least some decrease in external performance compared with internal performance, with nearly half (42 of 86, 49%) reporting at least a modest decrease (≥0.05 on the unit scale) and nearly a quarter (21 of 86, 24%) reporting a substantial decrease (≥0.10 on the unit scale). No study characteristics were found to be associated with the difference between internal and external performance. Conclusion: Among published external validation studies of DL algorithms for image-based radiologic diagnosis, the vast majority demonstrated diminished algorithm performance on the external dataset, with some reporting a substantial performance decrease.Keywords: Meta-Analysis, Computer Applications-Detection/Diagnosis, Neural Networks, Computer Applications-General (Informatics), Epidemiology, Technology Assessment, Diagnosis, Informatics Supplemental material is available for this article. © RSNA, 2022.

Role of Thigh Muscle Changes in Knee Osteoarthritis Outcomes: Osteoarthritis Initiative Data.

Background Longitudinal data on the association of quantitative thigh muscle MRI markers with knee osteoarthritis (KOA) outcomes are scarce. These associations are of clinical importance, with potential use for thigh muscle-directed disease-modifying interventions. Purpose To measure KOA-associated longitudinal changes in MRI-derived muscle cross-sectional area (CSA) and adipose tissue and their association with downstream symptom worsening and knee replacement (KR). Materials and Methods In a secondary analysis of the Osteoarthritis Initiative multicenter prospective cohort (February 2004 through October 2015), knees of participants with available good-quality thigh MRI scans at baseline and at least one follow-up visit were included and classified as with and without KOA according to baseline radiographic Kellgren-Lawrence grade of 2 or higher and matched for confounders with use of propensity score matching. An automated deep learning model for thigh MRI two-dimensional segmentation was developed and tested. Markers of muscle CSA and intramuscular adipose tissue (intra-MAT) were measured at baseline and 2nd- and 4th-year follow-up (period 1) and compared between knees with and without KOA by using linear mixed-effect regression models. Furthermore, in knees with KOA, the association of period 1 changes in muscle markers with risk of KR (Cox proportional hazards) and symptom worsening (mixed-effect models) during the 4th to 9th year (period 2) was evaluated. Results This study included 4634 matched thighs (2317 with and 2317 without KOA) of 2344 participants (mean age, 62 years ± 9 [SD]; 1292 women). Compared with those without, knees with KOA had a decrease in quadriceps CSA (mean difference, -8.21 mm2/year; P = .004) and an increase in quadriceps intra-MAT (1.98 mm2/year; P = .007). Decreased CSA and increased intra-MAT of quadriceps during period 1 was predictive of downstream (period 2) KOA symptom worsening (Western Ontario and McMaster Universities Osteoarthritis Index total score: odds ratio, 0.24 [negative association] [P < .001] and 1.38 [P = .012], respectively). Quadriceps CSA changes were negatively associated with higher future KR risk (hazard ratio, 0.70; P < .001). Conclusion Knee osteoarthritis was associated with longitudinal MRI-derived decreased quadriceps cross-sectional area and increased intramuscular adipose tissue. These potentially modifiable risk factors were predictive of downstream symptom worsening and knee replacement. Clinical trial registration no. NCT00080171 © RSNA, 2022 Online supplemental material is available for this article.

YouTube and Radiology: The Viability, Pitfalls, and Untapped Potential of the Premier Social Media Video Platform for Image-Based Education.

RATIONALE AND OBJECTIVES: There are several popular radiology channels on YouTube, reinforcing studies showing interest among medical students and trainees in video education and suggesting the potential use of YouTube for radiology education. MATERIALS AND METHODS: The CTisus YouTube channel, dedicated to radiology education and based in the Russell H. Morgan Department of Radiology and Radiological Science at Johns Hopkins Hospital, has 25,000 subscribers. The benefits of this social media platform for radiology education were analyzed. The most popular videos (n = 484) from July 1, 2017 to June 30, 2020 were categorized into "case clips" (short displays of case images); "Facebook Live" (15-20 minute discussions later posted to YouTube); "lectures" (weekly PowerPoint lectures); and "quizzes" (10-question quiz discussions posted monthly). The number of days videos were available from July 2017 to June 2020 were counted and median views per 30 days were recorded. Lecture content was used to determine which of the following topics were more popular (received the most views) than others: Artificial intelligence, chest, gastrointestinal, genitourinary, musculoskeletal, neuro, physics, technique (such as protocols and contrast), technology, and vascular. RESULTS: Facebook Live videos had the highest median views per 30 days (236.9), the highest median likes per 30 days (2.5), the highest median shares per 30 days (2.0), and the highest median subscribers gained per 30 days (0.7). Unlike video type, there was no obvious favorite lecture topic among viewers. CONCLUSION: Viewers were most engaged with longer videos, with interaction and watch time indicating greater interest than simple clicks/views. YouTube is an easy-to-use and valuable platform for hosting video content. It reaches a global audience and provides what many radiology trainees and professionals are looking for: video instruction.

One Algorithm May Not Fit All: How Selection Bias Affects Machine Learning Performance.

Machine learning (ML) algorithms have demonstrated high diagnostic accuracy in identifying and categorizing disease on radiologic images. Despite the results of initial research studies that report ML algorithm diagnostic accuracy similar to or exceeding that of radiologists, the results are less impressive when the algorithms are installed at new hospitals and are presented with new images. This phenomenon is potentially the result of selection bias in the data that were used to develop the ML algorithm. Selection bias has long been described by clinical epidemiologists as a key consideration when designing a clinical research study, but this concept has largely been unaddressed in the medical imaging ML literature. The authors discuss the importance of selection bias and its relevance to ML algorithm development to prepare the radiologist to critically evaluate ML literature for potential selection bias and understand how it might affect the applicability of ML algorithms in real clinical environments. ©RSNA, 2020.

Can AI outperform a junior resident? Comparison of deep neural network to first-year radiology residents for identification of pneumothorax.

PURPOSE: To (1) develop a deep learning system (DLS) using a deep convolutional neural network (DCNN) for identification of pneumothorax, (2) compare its performance to first-year radiology residents, and (3) evaluate the ability of a DLS to augment radiology residents by detecting missed pneumothoraces. METHODS: This was a retrospective study performed in September 2018. We obtained 112,120 chest radiographs (CXRs) from the NIH ChestXray14 database, of which 4360 cases (4%) were labeled as pneumothorax by natural language processing. We utilized 111,518 CXRs to train and validate the ResNet-152 DCNN pretrained on ImageNet to identify pneumothorax. DCNN testing was performed on a hold-out set of 602 CXRs, whose groundtruth was determined by a cardiothoracic radiologist. Two first-year radiology residents evaluated the test CXRs for presence of pneumothorax. Receiver operating characteristic (ROC) curves were generated for each evaluator with area under the curve (AUC) compared using the DeLong parametric method. RESULTS: The DCNN achieved AUC of 0.841 for identification of pneumothorax at a rate of 1980 images/min. In contrast, both first-year residents achieved significantly higher AUCs of 0.942 and 0.905 (p < 0.01 for both compared to DCNN), but at a slower rate of two images/min. The DCNN identified 3 of 31 (9.7%) additional pneumothoraces missed by at least one of the residents. CONCLUSION: A DLS for pneumothorax identification had lower AUC than 1st-year radiology residents, but interpreted images > 1000× as fast and identified 3 additional pneumothoraces missed by the residents. Our findings suggest that DLS could augment radiologists-in-training to identify potential urgent findings.

Use of Advanced Imaging for Radiographically Occult Hip Fracture in Elderly Patients: A Systematic Review and Meta-Analysis.

Background The overall rate of hip fractures not identified on radiographs but that require surgery (ie, surgical hip fractures) remains unclear in elderly patients who are suspected to have such fractures based on clinical findings. Moreover, the importance of advanced imaging in these patients has not been comprehensively assessed. Purpose To estimate the frequency of radiographically occult hip fracture in elderly patients, to define the higher-risk subpopulation, and to determine the diagnostic performance of CT and bone scanning in the detection of occult fractures by using MRI as the reference standard. Materials and Methods A literature search was performed to identify English-language observational studies published from inception to September 27, 2018. Studies were included if patients were clinically suspected to have hip fracture but there was no radiographic evidence of surgical hip fracture (including absence of any definite fracture or only presence of isolated greater trochanter [GT] fracture). The rate of surgical hip fracture was reported in each study in which MRI was used as the reference standard. The pooled rate of occult fracture, diagnostic performance of CT and bone scanning, and strength of evidence (SOE) were assessed. Results Thirty-five studies were identified (2992 patients; mean age, 76.8 years ± 6.0 [standard deviation]; 66% female). The frequency of radiographically occult surgical hip fracture was 39% (1110 of 2835 patients; 95% confidence interval [CI]: 35%, 43%) in studies of patients with no definite radiographic fracture and 92% (134 of 157 patients; 95% CI: 83%, 98%) in studies of patients with radiographic evidence of isolated GT fracture (moderate SOE). The frequency of occult fracture was higher in patients aged at least 80 years (44%, 529 of 1184), those with an equivocal radiographic report (58%, 71 of 126), and those with a history of trauma (41%, 977 of 2370) (moderate SOE). CT and bone scanning yielded comparable diagnostic performance in the detection of radiographically occult hip fracture (P = .67), with a sensitivity of 79% and 87%, respectively (low SOE). Conclusion Elderly patients with acute hip pain and negative or equivocal findings at initial radiography have a high frequency of occult hip fractures. Therefore, the performance of advanced imaging (preferably MRI) may be clinically appropriate in all such patients. © RSNA, 2020 Online supplemental material is available for this article.

Is a Picture Really Worth More than a Thousand Words? Which Instagram Post Types Elicit the Best Response for Radiology Education.

Since its 2010 launch, Instagram has rapidly risen to become one of the leading social media in the world, with more than one billion monthly users. Within the field of radiology, perhaps because of the image-weighted nature of the platform, several prominent organizations host Instagram accounts, including the Radiological Society of North America, American Roentgen Ray Society, American College of Radiology, and the American Board of Radiology. We started our own Instagram account in January 2016 because of the popularity of this social media platform among medical students. Our website contains over 260,000 images and is aimed at educating physicians, technologists, and nurses around the world on radiology, with an emphasis on body computed tomography. Given our varied selection of radiology resources, we were curious as to which posts perform best on Instagram and set out how to best characterize the interest in these posts. Our results point to an approach that can aid radiology educators who use social media, particularly Instagram, in producing popular content.

Imaging Publications in the COVID-19 Pandemic: Applying New Research Results to Clinical Practice.

Online supplemental material is available for this article.

Left Ventricular Mass at MRI and Long-term Risk of Cardiovascular Events: The Multi-Ethnic Study of Atherosclerosis (MESA).

Background Few data exist on the long-term risk prediction of elevated left ventricular (LV) mass quantified by MRI for cardiovascular (CV) events in a contemporary, ethnically diverse cohort. Purpose To assess the long-term impact of elevated LV mass on CV events in a prospective cohort study of a multiethnic population in relationship to risk factors and coronary artery calcium (CAC) score. Materials and Methods The Multi-Ethnic Study of Atherosclerosis, or MESA (ClinicalTrials.gov: NCT00005487), is an ongoing prospective multicenter population-based study in the United States. A total of 6814 participants (age range, 45-84 years) free of clinical CV disease at baseline were enrolled between 2000 and 2002. In 4988 participants (2613 [52.4%] women; mean age, 62 years ± 10.1 [standard deviation]) followed over 15 years for CV events, LV mass was derived from cardiac MRI at baseline enrollment by using semiautomated software at a central core laboratory. Cox proportional hazard models, Kaplan-Meier curves, and z scores were applied to assess the impact of LV hypertrophy. Results A total of 290 participants had hard coronary heart disease (CHD) events (207 myocardial infarctions [MIs], 95 CHD deaths), 57 had other CV disease-related deaths, and 215 had heart failure (HF). LV hypertrophy was an independent predictor of hard CHD events (hazard ratio [HR]: 2.7; 95% confidence interval [CI]: 1.9, 3.8), MI (HR: 2.8; 95% CI: 1.8, 4.0), CHD death (HR: 4.3; 95% CI: 2.5, 7.3), other CV death (HR: 7.5; 95% CI: 4.2, 13.5), and HF (HR: 5.4; 95% CI: 3.8, 7.5) (P < .001 for all end points). LV hypertrophy was a stronger predictor than CAC for CHD death, other CV death, and HF (z scores: 5.4 vs 3.4, 6.8 vs 2.4, and 9.7 vs 3.2 for LV hypertrophy vs CAC, respectively). Kaplan-Meier analysis demonstrated an increased risk of CV events in participants with LV hypertrophy, particularly after 5 years. Conclusion Elevated left ventricular mass was strongly associated with hard coronary heart disease events, other cardiovascular death, and heart failure over 15 years of follow-up, independent of traditional risk factors and coronary artery calcium score. © RSNA, 2019 See also the editorial by Hanneman in this issue.

Added value of apparent diffusion coefficient in distinguishing between serous and mucin-producing pancreatic cystic neoplasms.

OBJECTIVES: To evaluate the added value of diffusion-weighted imaging (DWI) on MRI in differentiating serous from mucin-producing pancreatic cystic neoplasms (PCNs). METHODS: One hundred seventeen patients with PCN measuring ≥ 10 mm were included. Three readers independently evaluated MRI with and without the use of apparent diffusion coefficient (ADC). Logistic regression was used to analyze whether confidence scores were different with the use of different image sets. Diagnostic performance with and without ADC was compared. RESULTS: DWI/ADC improved confidence in 44.8%, 73.6%, and 78.2% of patients by the three readers in distinguishing serous from mucin-producing PCNs. The use of ADC increased the probability of a higher confidence in the differentiation as compared to morphological imaging for all three readers (p < 0.001). Odds ratio for increase in the diagnostic confidence with the use of ADC for the three readers with decreasing years of experience were 5.8, 6.8, and 12.7. The diagnostic accuracy of morphological MRI with ADC was higher than that without ADC for two of three readers with lesser experience (87.2% vs. 80.8%; 91.5% vs. 80.8%). CONCLUSION: DWI may have added value as a complementary tool to conventional morphological MRI in differentiating between serous and mucin-producing PCNs with possibly greater value for readers with less experience in reading abdominal MRI. KEY POINTS: • Optimal management of PCNs requires differentiation of serous from mucin-producing PCNs. • ADC measurements allow increased confidence in differentiating serous from mucin-producing PCNs. • ADC measurements increase the accuracy in diagnosing serous versus mucin-producing PCNs.

Diagnosis of Knee Meniscal Injuries by Using Three-dimensional MRI: A Systematic Review and Meta-Analysis of Diagnostic Performance.

Purpose To investigate the diagnostic performance of three-dimensional (3D) MRI for depicting meniscal injuries of the knee by using surgery as the standard of reference. Materials and Methods A literature search was performed to identify original studies published between 1985 and 2017. Summary receiver operating characteristic curve and sensitivity analyses were performed to compare the diagnostic performance of 3D versus two-dimensional (2D) MRI for the assessment of knee meniscal injuries and to evaluate the impact of relevant covariates on the diagnostic performance for assessment of knee meniscal injuries. Results Of identified records, 31 studies (1743 3D knee MRI examinations) were included (23 studies also reported the results of 2D MRI). All studies before 2008 used gradient-echo (GRE) sequences, whereas all studies after 2011 used fast spin-echo (FSE) sequences. By comparing FSE and GRE sequences with 2D MRI, pooled estimate of sensitivity (90.0%; P = .2 and 90.1%; P = .2 vs 88.5%) and pooled estimate of specificity (91%; P = .3 and 89.8% vs 90.1%; P = .7) were comparable. The 3D FSE sequences demonstrated similar diagnostic performance as 3D GRE sequences, except for slightly improved sensitivity for depicting lateral meniscal injuries (FSE, 84.6%; GRE, 75%; P = .01). The specificity of 3D sequences improved when multiplanar reformatting was performed (P = .02). Conclusion Both three-dimensional (3D) fast spin-echo (FSE) and 3D gradient-echo (GRE) sequences had similar diagnostic performance as two-dimensional sequences, with slight superior sensitivity of 3D FSE sequences compared with 3D GRE sequences for depicting lateral meniscal injuries of the knee. © RSNA, 2018 Online supplemental material is available for this article.

Epicardial Fat Distribution Assessed with Cardiac CT in Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy.

Purpose To compare epicardial fat in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) with that in healthy subjects. Materials and Methods In this retrospective study, cardiac CT scans in 44 patients with ARVD/C (mean age, 39 years ± 12; 23 men) were compared with those in 45 control group participants between January 2008 and July 2015. Volumes of intrathoracic adipose tissue, mediastinal adipose tissue (MAT), and total epicardial adipose tissue (EAT) were quantified. EAT was subdivided into three regions-right ventricular (RV) EAT, left ventricular (LV) EAT, and peri-atrial EAT (atrial EAT)-and normalized to MAT for all regions. Logistic regression and receiver operating characteristic analysis were performed to evaluate the association between epicardial fat with the diagnosis of ARVD/C. Results Total EAT volume was higher in patients with ARVD/C than in healthy control group participants (median, 98 mL vs 76 mL, respectively; P = .04). Regionally, LV and RV EAT volumes were higher in patients with ARVD/C than in control group participants, most notably when indexed to MAT (median LV EAT index: 0.49 vs 0.15, respectively; median RV EAT index: 0.91 vs 0.52; P ˂ .0005 for both). The optimal cutoff for diagnosis of ARVD/C was an LV EAT index of 0.24, with a sensitivity and specificity of 91% and 71%, respectively. Atrial EAT volume and total intrathoracic adipose tissue volume were not different between groups. RV diameter showed a positive correlation with total EAT index and LV EAT index (r = 0.21, P = .05 and r = 0.33, P = .002, respectively). Conclusion Higher amounts of right ventricular and left ventricular epicardial fat are found in hearts with arrhythmogenic right ventricular dysplasia/cardiomyopathy, particularly adjacent to the left ventricle, which correlates with disease severity and helps differentiate patients from healthy subjects. © RSNA, 2018 Online supplemental material is available for this article.

Diagnostic Performance of Three-dimensional MRI for Depicting Cartilage Defects in the Knee: A Meta-Analysis.

Purpose To determine the diagnostic performance of three-dimensional (3D) MRI for the depiction and characterization of cartilage defects within the knee joint by using arthroscopy and/or open surgery as the standard of reference. Materials and Methods A systematic literature search was performed to extract diagnostic studies published between January 1985 and October 2017. Two independent investigators assessed the methodologic quality of each study by using Quality Assessment of Diagnostic Accuracy Studies 2. Bivariate random-effects model was used to compare the diagnostic odds ratio (DOR) of 3D and two-dimensional (2D) MRI for helping to detect knee cartilage defects and to assess the effect of relevant covariates on diagnostic performance of 3D MRI. Meta-regression analysis was performed to assess DOR of 3D MRI during the last 3 decades. Results Twenty-seven studies (composed of 1710 MRI examinations) were included. Of those, 16 (59%) studies compared the diagnostic performance of 3D and 2D MRI. The diagnostic performance of 3D MRI statistically significantly improved over the last 3 decades (P = .003). Three-dimensional MRI obtained by using 3.0-T field strength had higher DOR relative to 1.5-T or lower field strength (relative DOR, 4.05; P = .01). Three-dimensional multiplanar reformation was associated with higher specificity (P = .001) compared with conventional axial, sagittal, and coronal 2D MRI planes. Three-dimensional fast-spin-echo sequences provided higher sensitivity and specificity (P < .05) than did 2D MRI. Conclusion Three-dimensional MRI currently provides comparable diagnostic performance to two-dimensional MRI, with improvement in diagnostic performance achieved by using 3.0-T field strength, three-dimensional fast-spin-echo sequences, and multiplanar reformation. © RSNA, 2018 Online supplemental material is available for this article.

Lesions of Ligamentum Teres: Diagnostic Performance of MRI and MR Arthrography-A Systematic Review and Meta-Analysis.

OBJECTIVE: The purpose of this study is to determine the diagnostic performance of MRI and MR arthrography for depicting ligamentum teres lesions. MATERIALS AND METHODS: A literature search was performed. Original studies reporting the diagnostic accuracy of MRI examinations for the depiction of ligamentum teres lesions were included. RESULTS: Eight studies entailing 1456 MRI examinations were included (frequency of median ligamentum teres injury, 25.9%; interquartile range, 14.1-45.3%). Two studies reported the results of unenhanced MRI examinations, and their diagnostic performance could not be estimated. Sensitivity, specificity, and diagnostic odds ratio (DOR) of all MRI examinations were 64.7%, 86.9%, and 12.2, respectively, whereas the sensitivity, specificity, and DOR of MR arthrography examinations were 82.2%, 88.6%, and 35.9, respectively. The heterogeneity (I2) for all MRI and MR arthrography examinations was 92.3% and 88.2%, respectively. Five blinded MR arthrography studies with 643 MR arthrography examinations found an appropriate threshold effect for summary ROC construction (AUC, 0.95). The summary estimate of these studies yielded a sensitivity of 87.8%, a specificity of 91%, and DOR of 73.1. The heterogeneity (I2) for this group was 64.3%. In patients with low pretest probability (25%), MR arthrography enabled the exclusion of ligamentum teres lesion (postprobability for a negative result, 4%; negative likelihood ratio, 0.13). CONCLUSION: MR arthrography can depict ligamentum teres lesions with high accuracy. However, its diagnostic performance for differentiating various types of ligamentum teres lesions (partial, complete ligamentum teres tears, and hypertrophic ligamentum teres), as well as the diagnostic performance of unenhanced MRI for the depiction of ligamentum teres lesions, is yet to be determined because of the paucity of reported data in the literature.

Validation of contrast-enhanced time-resolved magnetic resonance angiography in pre-ablation planning in patients with atrial fibrillation: comparison with traditional technique.

Bolus timing is critical to optimal magnetic resonance angiography (MRA) acquisitions but can be challenging in some patients. Our purpose was to evaluate whether contrast-enhanced time-resolved magnetic resonance angiography (TR-MRA), a dynamic multiphase sequence that does not rely on bolus timing, is a viable alternative method to conventional 3D fast-long angle shot contrast-enhanced magnetic resonance angiography (CE-MRA). Coronal subtracted conventional CE-MRA images in 50 consecutive patients presenting for pre-atrial fibrillation ablation pulmonary venous (PV) mapping were compared with 50 TR-MRA images performed in 50 subsequent patients. The TR-MRA protocol was modified to optimize spatial resolution with slightly reduced temporal resolution (6.1 s scan time). Three experienced readers evaluated each scan's image quality and relative left atrial (LA) opacification based on a 4-point scale and diagnostic PV visualization in a binary fashion. Additionally, LA signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and PV dimensions were measured for both techniques. TR-MRA had significantly higher overall image quality (3.10 ± 0.69 vs. 2.42 ± 0.69, p < 0.0001), and LA opacification scores (3.33 ± 0.70 vs. 2.15 ± 1.13, p < 0.0001) compared to CE-MRA. The proportion of diagnostically visualized pulmonary veins was 137/150 (91%) in the CE-MRA group vs. 147/150 (98%) with TR-MRA (p = 0.010). Both SNR and CNR were higher with TR-MRA vs. CE-MRA (277.9 ± 48.9 vs. 106.8 ± 41, p = 0.002 and 100.3 ± 41.7 vs. 70.7 ± 48.0, p = 0.002, respectively). Inter-reader variance of individual PV measurements for each of the MR techniques ranged between 0.62 and 1.47 mm and the ICC for vein measurements was higher with TR-MRA (range: 0.62-0.81) compared to CE-MRA (range: 0.47-0.64). TR-MRA, modified to maximize spatial resolution, offers an alternative method for performing high quality MRA examinations in patients with AF. TR-MRA offers greater overall image quality, PV visualization, and similarly reproducible PV measurements compared to traditional CE-MRA, without the challenges of proper bolus timing.

Evaluation of Coronary Artery Disease and Coronary Anomalies with a Handheld Smartphone.

The purpose of this study was to determine the diagnostic accuracy of an iPhone for evaluation of the coronary arteries on coronary CT angiography (CTA) in comparison to a standard clinical workstation. Fifty coronary CTA exams were selected to include a range of normal and abnormal cases including both coronary artery disease (CAD) of varying severity and coronary artery anomalies. Two cardiac radiologists reviewed each exam on a standard clinical workstation initially and then on an iPhone 6 after a washout period. Coronary stenosis was evaluated on a 4-point scale and presence of coronary anomalies was recorded. Two additional cardiac radiologists reviewed all cases in consensus on the standard workstation and these results were used as the reference standard. When reader results were compared to the reference standard, there was no significant difference in agreement for per-vessel stenosis scores using either the iPhone or standard clinical workstation. The intraobserver intertechnology agreement on a per-vessel basis for obstructive CAD were 97.4% (299/307, kappa = 0.777) and 97.5% (317/325, kappa = 0.804) for the two readers. All cases of coronary anomalies were identified by both readers regardless of the device used. Coronary CTA examinations can be interpreted on a smartphone with diagnostic accuracy comparable to a standard workstation. 3D visualization app on the iPhone may facilitate urgent coronary CTA review when a workstation is not available.