Fast cardiac T1ρ,adiab mapping using slice-selective adiabatic spin-lock preparation pulses.

PURPOSE: Myocardial T1ρ mapping techniques commonly acquire multiple images in one breathhold to calculate a single-slice T1ρ map. Recently, non-selective adiabatic pulses have been used for robust spin-lock preparation (T1ρ,adiab). The objective of this study was to develop a fast multi-slice myocardial T1ρ,adiab mapping approach. METHODS: The proposed-sequence reduces the number of breathholds required for whole-heart 2D T1ρ,adiab mapping by acquiring multiple interleaved slices in each breathhold using slice-selective T1ρ,adiab preparation pulses. The proposed-sequence was implemented with two interleaved slices per breathhold scan and was quantitatively evaluated in phantom experiments and 10 healthy-volunteers against a single-slice T1ρ,adiab mapping sequence. The sequence was demonstrated in two patients with myocardial scar. RESULTS: The phantom experiments showed the proposed-sequence had slice-to-slice variation of 1.62% ± 1.05% and precision of 4.51 ± 0.68 ms. The healthy volunteer cohort subject-wise mean relaxation time was lower for the proposed-sequence than the single-slice sequence (137.7 ± 5.3 ms vs. 148.4 ± 8.3 ms, p < 0.001), and spatial-standard-deviation was better (18.7 ± 1.8 ms vs. 21.8 ± 3.4 ms, p < 0.018). The mean within-subject, coefficient of variation was 5.93% ± 1.57% for the proposed-sequence and 6.31% ± 1.92% for the single-slice sequence (p = 0.35) and the effect of slice variation (0.81 ± 4.87 ms) was not significantly different to zero (p = 0.61). In both patient examples increased T1ρ,adiab (maximum American Heart Association-segment mean = 174 and 197 ms) was measured within the myocardial scar. CONCLUSION: The proposed sequence provides a twofold acceleration for myocardial T1ρ,adiab mapping using a multi-slice approach. It has no significant difference in within-subject variability, and significantly better precision, compared to a 2D T1ρ,adiab mapping sequence based on non-selective adiabatic spin-lock preparations.

Fast, automated, real-time 3D passive balloon catheter tracking during MRI-guided cardiac catheterization using orthogonal projection imaging and real-time image-based catheter detection.

PURPOSE: MRI-guidance of cardiac catheterization is currently performed using one or multiple 2D imaging planes, which may be suboptimal for catheter navigation, especially in patients with complex anatomies. The purpose of the work was to develop a robust real-time 3D catheter tracking method and 3D visualization strategy for improved MRI-guidance of cardiac catheterization procedures. METHODS: A fast 3D tracking technique was developed using continuous acquisition of two orthogonal 2D-projection images. Each projection corresponds to a gradient echo stack of slices with only the central k-space lines being collected for each slice. To enhance catheter contrast, a saturation pulse is added ahead of the projection pair. An offline image processing algorithm was developed to identify the 2D coordinates of the balloon in each projection image and to estimate its corresponding 3D coordinates. Post-processing includes background signal suppression using an atlas of background 2D-projection images. 3D visualization of the catheter and anatomy is proposed using three live sagittal, coronal, and axial (MPR) views and 3D rendering. The technique was tested in a subset of a catheterization step in three patients undergoing MRI-guided cardiac catheterization using a passive balloon catheter. RESULTS: The extraction of the catheter balloon 3D coordinates was successful in all patients and for the majority of time-points (accuracy >96%). This tracking method enabled a novel 3D visualization strategy for passive balloon catheter, providing enhanced anatomical context during catheter navigation. CONCLUSION: The proposed tracking strategy shows promise for robust tracking of passive balloon catheter and may enable enhanced visualization during MRI-guided cardiac catheterization.

Real-time automatic image-based slice tracking of gadolinium-filled balloon wedge catheter during MR-guided cardiac catheterization: A proof-of-concept study.

PURPOSE: MR-guided cardiac catheterization procedures currently use passive tracking approaches to follow a gadolinium-filled catheter balloon during catheter navigation. This requires frequent manual tracking and repositioning of the imaging slice during navigation. In this study, a novel framework for automatic real-time catheter tracking during MR-guided cardiac catheterization is presented. METHODS: The proposed framework includes two imaging modes (Calibration and Runtime). The sequence starts in Calibration mode, in which the 3D catheter coordinates are determined using a stack of 10-20 contiguous saturated slices combined with real-time image processing. The sequence then automatically switches to Runtime mode, where three contiguous slices (acquired with partial saturation), initially centered on the catheter balloon using the Calibration feedback, are acquired continuously. The 3D catheter balloon coordinates are estimated in real time from each Runtime slice stack using image processing. Each Runtime stack is repositioned to maintain the catheter balloon in the central slice based on the prior Runtime feedback. The sequence switches back to Calibration mode if the catheter is not detected. This framework was evaluated in a heart phantom and 3 patients undergoing MR-guided cardiac catheterization. Catheter detection accuracy and rate of catheter visibility were evaluated. RESULTS: The automatic detection accuracy for the catheter balloon during the Calibration/Runtime mode was 100%/95% in phantom and 100%/97 ± 3% in patients. During Runtime, the catheter was visible in 82% and 98 ± 2% of the real-time measurements in the phantom and patients, respectively. CONCLUSION: The proposed framework enabled real-time continuous automatic tracking of a gadolinium-filled catheter balloon during MR-guided cardiac catheterization.

Structural phenotyping in atrial fibrillation with combined cardiac CT and atrial MRI: Identifying and differentiating individual structural remodelling types in AF.

INTRODUCTION: Atrial remodelling (AR) is the persistent change in atrial structure and/or function and contributes to the initiation, maintenance and progression of atrial fibrillation (AF) in a reciprocal self-perpetuating relationship. Left atrial (LA) size, geometry, fibrosis, wall thickness (LAWT) and ejection fraction (LAEF) have all been shown to vary with pathological atrial remodelling. The association of these global remodelling markers with each other for differentiating structural phenotypes in AF is not well investigated. METHOD: Patients referred for first-time AF ablation and controls without AF were prospectively recruited to undergo cardiac computed tomographic angiography (CCTA) and magnetic resonance imaging (MRI) with 3D atrial late-gadolinium enhanced (LGE) sequences. LAWT, atrial myocardial mass, LA volume and sphericity were calculated from CT. Biplane LA EF and LA fibrosis burden were derived from atrial MRI. Results were compared between patients with AF and controls. RESULTS: Forty two AF patients (64.3% male, age 64.6 ± 10.2 years, CHA2DS2-VASc 2.48 ± 1.5, 69.0% paroxysmal AF, 31% persistent AF, LVEF 57.9 ± 10.5%) and 37 controls (64.9% male, age 56.6 ± 7.2, CHA2DS2-VASc 1.54 ± 1.1, LVEF 60.4 ± 4.9%) were recruited. Patients with AF had a significantly higher LAWT (1.45 ± 0.52 mm vs 1.12 ± 0.42 mm, p = 0.003), tissue mass (15.81 ± 6.53 g vs. 12.18 ± 5.01 g, p = 0.011), fibrosis burden (9.33 ± 8.35% vs 2.41 ± 3.60%, p = 0.013), left atrial size/volume (95.68 ± 26.63 mL vs 81.22 ± 20.64 mL, p = 0.011) and lower LAEF (50.3 ± 15.3% vs 65.2 ± 8.6%, p < 0.001) compared to controls. There was no significant correlation between % fibrosis with LAWT (p = 0.29), mass (p = 0.89), volume (p = 0.49) or sphericity (p = 0.79). LAWT had a statistically significant weak positive correlation with LA volume (r = 0.25, p = .041), but not with sphericity (p = 0.86). LAEF had a statistically significant but weak negative correlation with fibrosis (r = -0.33, p = 0.008) and LAWT (r = -0.24, p = 0.07). CONCLUSION: AF is associated with significant quantifiable structural changes that are evident in LA size, tissue thickness, total LA tissue mass and fibrosis. These individual remodelling markers do not or only weakly correlate with each other suggesting different remodelling subtypes exist (e.g. fibrotic vs hypertrophic vs dilated). If confirmed, such a detailed understanding of the structural changes observed has the potential to inform clinical management strategies targeting individual mechanisms underlying the disease process.

Convergent ablation for persistent atrial fibrillation: A UK multicentre perspective.

Atrial fibrillation (AF) is the most common sustained arrhythmia worldwide and remains a major cause of morbidity and mortality. Unfortunately, a significant proportion of patients have persistent AF, for which conventional catheter ablation is less effective. However, convergent ablation has emerged in recent years as a hybrid treatment targeting both the epicardium and endocardium in a multidisciplinary joint cardiothoracic and electrophysiology procedure, with promising efficacy outcomes in recent studies. This treatment is increasingly being performed in the United Kingdom. This review article discusses the rationale and evidence behind convergent ablation, along with factors that need to be considered when setting up a successful ablation service.

T2*-Relaxometry MRI to Assess Third Trimester Placental and Fetal Brain Oxygenation and Placental Characteristics in Healthy Fetuses and Fetuses With Congenital Heart Disease.

BACKGROUND: Congenital heart disease (CHD) has been linked to impaired placental and fetal brain development. Assessing the placenta and fetal brain in parallel may help further our understanding of the relationship between development of these organs. HYPOTHESIS: 1) Placental and fetal brain oxygenation are correlated, 2) oxygenation in these organs is reduced in CHD compared to healthy controls, and 3) placental structure is altered in CHD. STUDY TYPE: Retrospective case-control. POPULATION: Fifty-one human fetuses with CHD (32 male; median [IQR] gestational age [GA] = 32.0 [30.9-32.9] weeks) and 30 from uncomplicated pregnancies with normal birth outcomes (18 male; median [IQR] GA = 34.5 [31.9-36.7] weeks). FIELD STRENGTH/SEQUENCE: 1.5 T single-shot multi-echo-gradient-echo echo-planar imaging. ASSESSMENT: Masking was performed using an automated nnUnet model. Mean brain and placental T2* and quantitative measures of placental texture, volume, and morphology were calculated. STATISTICAL TESTS: Spearman's correlation coefficient for determining the association between brain and placental T2*, and between brain and placental characteristics with GA. P-values for comparing brain T2*, placenta T2*, and placental characteristics between groups derived from ANOVA. Significance level P < 0.05. RESULTS: There was a significant positive association between placental and fetal brain T2* (⍴ = 0.46). Placental and fetal brain T2* showed a significant negative correlation with GA (placental T2* ⍴ = -0.65; fetal brain T2* ⍴ = -0.32). Both placental and fetal brain T2* values were significantly reduced in CHD, after adjusting for GA (placental T2*: control = 97 [±24] msec, CHD = 83 [±23] msec; brain T2*: control = 218 [±26] msec, CHD = 202 [±25] msec). Placental texture and morphology were also significantly altered in CHD (Texture: control = 0.84 [0.83-0.87], CHD = 0.80 [0.78-0.84]; Morphology: control = 9.9 [±2.2], CHD = 10.8 [±2.0]). For all fetuses, there was a significant positive association between placental T2* and placental texture (⍴ = 0.46). CONCLUSION: Placental and fetal brain T2* values are associated in healthy fetuses and those with CHD. Placental and fetal brain oxygenation are reduced in CHD. Placental appearance is significantly altered in CHD and shows associations with placental oxygenation, suggesting altered placental development and function may be related. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 3.

Double aortic arch: a comparison of fetal cardiovascular magnetic resonance, postnatal computed tomography and surgical findings.

BACKGROUND: In double aortic arch (DAA), one of the arches can demonstrate atretic portions postnatally, leading to diagnostic uncertainty due to overlap with isolated right aortic arch (RAA) variants. The main objective of this study is to demonstrate the morphological evolution of different DAA phenotypes from prenatal to postnatal life using three-dimensional (3D) fetal cardiac magnetic resonance (CMR) imaging and postnatal computed tomography (CT)/CMR imaging. METHODS: Three-dimensional fetal CMR was undertaken in fetuses with suspected DAA over a 6-year period (January 2016-January 2022). All cases with surgical confirmation of DAA were retrospectively studied and morphology on fetal CMR was compared to postnatal CT/CMR and surgical findings. RESULTS: Thirty-four fetuses with surgically confirmed DAA underwent fetal CMR. The RAA was dominant in 32/34 (94%). Postnatal CT/CMR was undertaken at a median age of 3.3 months (interquartile range 2.0-3.9) demonstrating DAA with patency of both arches in 10/34 (29%), with 7 showing signs of coarctation of the left aortic arch (LAA). The LAA isthmus was not present on CT/CMR in 22/34 (65%), and the transverse arch between left carotid and left subclavian artery was not present in 2 cases. CONCLUSION: Fetal CMR provides novel insights into perinatal evolution of DAA. The smaller LAA can develop coarctation or atresia related to postnatal constriction of the arterial duct, making diagnosis of DAA challenging with contrast-enhanced CT/CMR. This highlights the potentially important role for prenatal 3D vascular imaging and might improve the interpretation of postnatal imaging.

Retrospective motion correction through multi-average k-space data elimination (REMAKE) for free-breathing cardiac cine imaging.

PURPOSE: To develop a motion-robust reconstruction technique for free-breathing cine imaging with multiple averages. METHOD: Retrospective motion correction through multiple average k-space data elimination (REMAKE) was developed using iterative removal of k-space segments (from individual k-space samples) that contribute most to motion corruption while combining any remaining segments across multiple signal averages. A variant of REMAKE, termed REMAKE+, was developed to address any losses in SNR due to k-space information removal. With REMAKE+, multiple reconstructions using different initial conditions were performed, co-registered, and averaged. Both techniques were validated against clinical "standard" signal averaging reconstruction in a static phantom (with simulated motion) and 15 patients undergoing free-breathing cine imaging with multiple averages. Quantitative analysis of myocardial sharpness, blood/myocardial SNR, myocardial-blood contrast-to-noise ratio (CNR), as well as subjective assessment of image quality and rate of diagnostic quality images were performed. RESULTS: In phantom, motion artifacts using "standard" (RMS error [RMSE]: 2.2 ± 0.5) were substantially reduced using REMAKE/REMAKE+ (RMSE: 1.5 ± 0.4/1.0 ± 0.4, p < 0.01). In patients, REMAKE/REMAKE+ led to higher myocardial sharpness (0.79 ± 0.09/0.79 ± 0.1 vs. 0.74 ± 0.12 for "standard", p = 0.004/0.04), higher image quality (1.8 ± 0.2/1.9 ± 0.2 vs. 1.6 ± 0.4 for "standard", p = 0.02/0.008), and a higher rate of diagnostic quality images (99%/100% vs. 94% for "standard"). Blood/myocardial SNR for "standard" (94 ± 30/33 ± 10) was higher vs. REMAKE (80 ± 25/28 ± 8, p = 0.002/0.005) and tended to be lower vs. REMAKE+ (105 ± 33/36 ± 12, p = 0.02/0.06). Myocardial-blood CNR for "standard" (61 ± 22) was higher vs. REMAKE (53 ± 19, p = 0.003) and lower vs. REMAKE+ (69 ± 24, p = 0.007). CONCLUSIONS: Compared to "standard" signal averaging reconstruction, REMAKE and REMAKE+ provide improved myocardial sharpness, image quality, and rate of diagnostic quality images.

Total and Regional Brain Volumes in Fetuses With Congenital Heart Disease.

BACKGROUND: Congenital heart disease (CHD) is common and is associated with impaired early brain development and neurodevelopmental outcomes, yet the exact mechanisms underlying these associations are unclear. PURPOSE: To utilize MRI data from a cohort of fetuses with CHD as well as typically developing fetuses to test the hypothesis that expected cerebral substrate delivery is associated with total and regional fetal brain volumes. STUDY TYPE: Retrospective case-control study. POPULATION: Three hundred eighty fetuses (188 male), comprising 45 healthy controls and 335 with isolated CHD, scanned between 29 and 37 weeks gestation. Fetuses with CHD were assigned into one of four groups based on expected cerebral substrate delivery. FIELD STRENGTH/SEQUENCE: T2-weighted single-shot fast-spin-echo sequences and a balanced steady-state free precession gradient echo sequence were obtained on a 1.5 T scanner. ASSESSMENT: Images were motion-corrected and reconstructed using an automated slice-to-volume registration reconstruction technique, before undergoing segmentation using an automated pipeline and convolutional neural network that had undergone semi-supervised training. Differences in total, regional brain (cortical gray matter, white matter, deep gray matter, cerebellum, and brainstem) and brain:body volumes were compared between groups. STATISTICAL TESTS: ANOVA was used to test for differences in brain volumes between groups, after accounting for sex and gestational age at scan. PFDR -values <0.05 were considered statistically significant. RESULTS: Total and regional brain volumes were smaller in fetuses where cerebral substrate delivery is reduced. No significant differences were observed in total or regional brain volumes between control fetuses and fetuses with CHD but normal cerebral substrate delivery (all PFDR > 0.12). Severely reduced cerebral substrate delivery is associated with lower brain:body volume ratios. DATA CONCLUSION: Total and regional brain volumes are smaller in fetuses with CHD where there is a reduction in cerebral substrate delivery, but not in those where cerebral substrate delivery is expected to be normal. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 3.

Long-term survival following transvenous lead extraction: unpicking differences according to sex.

AIMS: Female sex is a recognized risk factor for procedure-related major complications including in-hospital mortality following transvenous lead extraction (TLE). Long-term outcomes following TLE stratified by sex are unclear. The purpose of this study was to evaluate factors influencing long-term survival in patients undergoing TLE according to sex. METHODS AND RESULTS: Clinical data from consecutive patients undergoing TLE in the reference centre between 2000 and 2019 were prospectively collected. The total cohort was divided into groups based on sex. We evaluated the association of demographic, clinical, device-related, and procedure-related factors on long-term mortality. A total of 1151 patients were included, with mean 66-month follow-up and mortality of 34.2% (n = 392). The majority of patients were male (n = 834, 72.4%) and 312 (37.4%) died. Males were more likely to die on follow-up [hazard ratio (HR) = 1.58 (1.23-2.02), P < 0.001]. Males had a higher mean age at explant (66.2 ± 13.9 vs. 61.3 ± 16.3 years, P < 0.001), greater mean co-morbidity burden (2.14 vs. 1.27, P < 0.001), and lower mean left ventricular ejection fraction (LVEF) (43.4 ± 14.0 vs. 50.8 ± 12.7, P = 0.001). For the female cohort, age > 75 years [HR = 3.45 (1.99-5.96), P < 0.001], estimated glomerular filtration rate < 60 [HR = 1.80 (1.03-3.11), P = 0.037], increasing co-morbidities (HR = 1.29 (1.06-1.56), P = 0.011), and LVEF per percentage increase [HR = 0.97 (0.95-0.99), P = 0.005] were all significant factors predicting mortality. The same factors influenced mortality in the male cohort; however, the HRs were lower. CONCLUSION: Female patients undergoing TLE have more favourable long-term outcomes than males with lower long-term mortality. Similar factors influenced mortality in both groups.

Clinical benefit of AI-assisted lung ultrasound in a resource-limited intensive care unit.

BACKGROUND: Interpreting point-of-care lung ultrasound (LUS) images from intensive care unit (ICU) patients can be challenging, especially in low- and middle- income countries (LMICs) where there is limited training available. Despite recent advances in the use of Artificial Intelligence (AI) to automate many ultrasound imaging analysis tasks, no AI-enabled LUS solutions have been proven to be clinically useful in ICUs, and specifically in LMICs. Therefore, we developed an AI solution that assists LUS practitioners and assessed its usefulness in  a low resource ICU. METHODS: This was a three-phase prospective study. In the first phase, the performance of four different clinical user groups in interpreting LUS clips was assessed. In the second phase, the performance of 57 non-expert clinicians with and without the aid of a bespoke AI tool for LUS interpretation was assessed in retrospective offline clips. In the third phase, we conducted a prospective study in the ICU where 14 clinicians were asked to carry out LUS examinations in 7 patients with and without our AI tool and we interviewed the clinicians regarding the usability of the AI tool. RESULTS: The average accuracy of beginners' LUS interpretation was 68.7% [95% CI 66.8-70.7%] compared to 72.2% [95% CI 70.0-75.6%] in intermediate, and 73.4% [95% CI 62.2-87.8%] in advanced users. Experts had an average accuracy of 95.0% [95% CI 88.2-100.0%], which was significantly better than beginners, intermediate and advanced users (p < 0.001). When supported by our AI tool for interpreting retrospectively acquired clips, the non-expert clinicians improved their performance from an average of 68.9% [95% CI 65.6-73.9%] to 82.9% [95% CI 79.1-86.7%], (p < 0.001). In prospective real-time testing, non-expert clinicians improved their baseline performance from 68.1% [95% CI 57.9-78.2%] to 93.4% [95% CI 89.0-97.8%], (p < 0.001) when using our AI tool. The time-to-interpret clips improved from a median of 12.1 s (IQR 8.5-20.6) to 5.0 s (IQR 3.5-8.8), (p < 0.001) and clinicians' median confidence level improved from 3 out of 4 to 4 out of 4 when using our AI tool. CONCLUSIONS: AI-assisted LUS can help non-expert clinicians in an LMIC ICU improve their performance in interpreting LUS features more accurately, more quickly and more confidently.

Prenatal diagnosis of hypoplastic left heart syndrome on ultrasound using artificial intelligence: How does performance compare to a current screening programme?

BACKGROUND: Artificial intelligence (AI) has the potential to improve prenatal detection of congenital heart disease. We analysed the performance of the current national screening programme in detecting hypoplastic left heart syndrome (HLHS) to compare with our own AI model. METHODS: Current screening programme performance was calculated from local and national sources. AI models were trained using four-chamber ultrasound views of the fetal heart, using a ResNet classifier. RESULTS: Estimated current fetal screening programme sensitivity and specificity for HLHS were 94.3% and 99.985%, respectively. Depending on calibration, AI models to detect HLHS were either highly sensitive (sensitivity 100%, specificity 94.0%) or highly specific (sensitivity 93.3%, specificity 100%). Our analysis suggests that our highly sensitive model would generate 45,134 screen positive results for a gain of 14 additional HLHS cases. Our highly specific model would be associated with two fewer detected HLHS cases, and 118 fewer false positives. CONCLUSION: If used independently, our AI model performance is slightly worse than the performance level of the current screening programme in detecting HLHS, and this performance is likely to deteriorate further when used prospectively. This demonstrates that collaboration between humans and AI will be key for effective future clinical use.

Quantification of balanced SSFP myocardial perfusion imaging at 1.5 T: Impact of the reference image.

PURPOSE: To investigate the use of a high flip-angle (HFA) balanced SSFP (bSSFP) reference image (in comparison to conventional proton density [PD]-weighted reference images) for conversion of bSSFP myocardial perfusion images into dynamic T1 maps for improved myocardial blood flow (MBF) quantification at 1.5 T. METHODS: The HFA-bSSFP (flip angle [FA] = 50°), PD gradient-echo (PD-GRE; FA = 5°), and PD-bSSFP (FA = 8°) reference images were acquired before a dual-sequence bSSFP perfusion acquisition. Simulations were used to study accuracy and precision of T1 and MBF quantification using the three techniques. The accuracy and precision of T1 , and the precision and intersegment variability of MBF were compared among the three techniques in 8 patients under rest conditions. RESULTS: In simulations, HFA-bSSFP demonstrated improved T1 /MBF precision (higher T1 /MBF SD of 30%-80%/50%-100% and 30%-90%/60%-115% for PD-GRE and PD-bSSFP, respectively). Proton density-GRE and PD-bSSFP were more sensitive to effective FA than HFA-bSSFP (maximum T1 /MBF errors of 13%/43%, 20%/43%, and 1%/3%, respectively). Sensitivity of all techniques (defined as T1 /MBF errors) to native T1 , native T2 , and effective saturation efficiency were negligible (<1%/<1%), moderate (<14%/<19%), and high (<63%/<94%), respectively. In vivo, no difference in T1 accuracy was observed among HFA-bSSFP, PD-GRE, and PD-bSSFP (-9 ± 44 ms vs -28 ± 55 ms vs -22 ± 71 ms, respectively; p > .08). The HFA-bSSFP led to improved T1 /MBF precision (T1 /MBF SD: 41 ± 19 ms/0.24 ± 0.08 mL/g/min vs PD-GRE: 48 ± 20 ms/0.29 ± 0.09 mL/g/min and PD-bSSFP: 59 ± 23 ms/0.33 ± 0.11 mL/g/min; p ≤ .02) and lower MBF intersegment variability (0.14 ± 0.09 mL/g/min vs PD-GRE: 0.21 ± 0.09 mL/g/min and PD-bSSFP: 0.20 ± 0.10 mL/g/min; p ≤ .046). CONCLUSION: We have demonstrated the feasibility of using a HFA-bSSFP reference image for MBF quantification of bSSFP perfusion imaging at 1.5 T. Results from simulations demonstrate that the HFA-bSSFP reference image results in improved precision and reduced sensitivity to effective FA compared with conventional techniques using a PD reference image. Preliminary in vivo data acquired at rest also demonstrate improved precision and intersegment variability using the HFA-bSSFP technique compared with PD techniques; however, a clinical study in patients with coronary artery disease under stress conditions is required to determine the clinical significance of this finding.

Simultaneous multislice steady-state free precession myocardial perfusion with full left ventricular coverage and high resolution at 1.5 T.

PURPOSE: To implement and evaluate a simultaneous multi-slice balanced SSFP (SMS-bSSFP) perfusion sequence and compressed sensing reconstruction for cardiac MR perfusion imaging with full left ventricular (LV) coverage (nine slices/heartbeat) and high spatial resolution (1.4 × 1.4 mm2 ) at 1.5T. METHODS: A preliminary study was performed to evaluate the performance of blipped controlled aliasing in parallel imaging (CAIPI) and RF-CAIPI with gradient-controlled local Larmor adjustment (GC-LOLA) in the presence of fat. A nine-slice SMS-bSSFP sequence using RF-CAIPI with GC-LOLA with high spatial resolution (1.4 × 1.4 mm2 ) and a conventional three-slice sequence with conventional spatial resolution (1.9 × 1.9 mm2 ) were then acquired in 10 patients under rest conditions. Qualitative assessment was performed to assess image quality and perceived signal-to-noise ratio (SNR) on a 4-point scale (0: poor image quality/low SNR; 3: excellent image quality/high SNR), and the number of myocardial segments with diagnostic image quality was recorded. Quantitative measurements of myocardial sharpness and upslope index were performed. RESULTS: Fat signal leakage was significantly higher for blipped CAIPI than for RF-CAIPI with GC-LOLA (7.9% vs. 1.2%, p = 0.010). All 10 SMS-bSSFP perfusion datasets resulted in 16/16 diagnostic myocardial segments. There were no significant differences between the SMS and conventional acquisitions in terms of image quality (2.6 ± 0.6 vs. 2.7 ± 0.2, p = 0.8) or perceived SNR (2.8 ± 0.3 vs. 2.7 ± 0.3, p = 0.3). Inter-reader variability was good for both image quality (ICC = 0.84) and perceived SNR (ICC = 0.70). Myocardial sharpness was improved using the SMS sequence compared to the conventional sequence (0.37 ± 0.08 vs 0.32 ± 0.05, p < 0.001). There was no significant difference between measurements of upslope index for the SMS and conventional sequences (0.11 ± 0.04 vs. 0.11 ± 0.03, p = 0.84). CONCLUSION: SMS-bSSFP with multiband factor 3 and compressed sensing reconstruction enables cardiac MR perfusion imaging with three-fold increased spatial coverage and improved myocardial sharpness compared to a conventional sequence, without compromising perceived SNR, image quality, upslope index or number of diagnostic segments.

Mental health among UK university staff and postgraduate students in the early stages of the COVID-19 pandemic.

OBJECTIVES: To characterise the baseline King's College London Coronavirus Health and Experiences of Colleagues at King's cohort and describe patterns of probable depression and anxiety among staff and postgraduate research students at a large UK university in April/May 2020. METHODS: An online survey was sent to current staff and postgraduate research students via email in April 2020 (n=2590). Primary outcomes were probable depression and anxiety, measured with the Patient Health Questionnaire-9 and Generalised Anxiety Disorder-7, respectively. Secondary outcomes were alcohol use and perceived change in mental health. Outcomes were described using summary statistics and multivariable Poisson regression was used to explore associations with six groups of predictors: demographics and prior mental health, living arrangements, caring roles, healthcare, occupational factors and COVID-19 infection. All analyses were weighted to account for differences between the sample and target population in terms of age, gender, and ethnicity. RESULTS: Around 20% of staff members and 30% of postgraduate research students met thresholds for probable depression or anxiety on the questionnaires. This doubled to around 40% among younger respondents aged <25. Other factors associated with probable depression and anxiety included female gender, belonging to an ethnic minority group, caregiving responsibilities and shielding or isolating. Around 20% of participants were found to reach cut-off for hazardous drinking on Alcohol Use Disorders Identification Test, while 30% were drinking more than before the pandemic. CONCLUSIONS: Our study shows worrying levels of symptoms of depression, anxiety and alcohol use disorder in an occupational sample from a large UK university in the months following the outbreak of the COVID-19 pandemic.

Trajectories of mental health among UK university staff and postgraduate students during the pandemic.

OBJECTIVES: The COVID-19 pandemic has disrupted the social and working lives of many. Past studies have highlighted worsening mental health during the pandemic, but often rely on small samples or infrequent follow-up. This study draws on fortnightly assessments from a large occupational cohort to describe differing trajectories of mental health between April 2020 and April 2021 and individual characteristics associated with these trajectory types. METHODS: King's College London Coronavirus Health and Experiences of Colleagues at King's is an occupational cohort study at a large university in London, UK. Participants (n=2241) completed online questionnaires fortnightly between April 2020 and April 2021. Symptoms of anxiety and depression were assessed using Generalised Anxiety Disorder (GAD-7) and Patient Health Questionnaire (PHQ-9). RESULTS: On average, participants reported low levels of anxiety and depression (GAD-7 and PHQ-9 scores of 0-9, consistent with 'none', 'minimal' or 'mild' symptoms) throughout the year, with symptoms highest in April 2020 and decreasing over the summer months when no lockdown measures were in place. However, we observed more severe and variable symptoms among subgroups of participants. Four trajectory types for anxiety and depression were identified: 'persistent high severity' (6%-7% of participants), 'varying symptoms, opposing national cases' (4%-8%), 'varying symptoms, consistent with national cases' (6%-11%) and 'persistent low severity' (74%-84%). Younger age, female gender, caring responsibilities and shielding were associated with higher severity trajectory types. CONCLUSIONS: These data highlight differing individual responses to the pandemic and underscore the need to consider individual circumstances when assessing and treating mental health. Aggregate trends in anxiety and depression may hide greater variation and symptom severity among subgroups.

Exploring a new paradigm for the fetal anomaly ultrasound scan: Artificial intelligence in real time.

OBJECTIVE: Advances in artificial intelligence (AI) have demonstrated potential to improve medical diagnosis. We piloted the end-to-end automation of the mid-trimester screening ultrasound scan using AI-enabled tools. METHODS: A prospective method comparison study was conducted. Participants had both standard and AI-assisted US scans performed. The AI tools automated image acquisition, biometric measurement, and report production. A feedback survey captured the sonographers' perceptions of scanning. RESULTS: Twenty-three subjects were studied. The average time saving per scan was 7.62 min (34.7%) with the AI-assisted method (p < 0.0001). There was no difference in reporting time. There were no clinically significant differences in biometric measurements between the two methods. The AI tools saved a satisfactory view in 93% of the cases (four core views only), and 73% for the full 13 views, compared to 98% for both using the manual scan. Survey responses suggest that the AI tools helped sonographers to concentrate on image interpretation by removing disruptive tasks. CONCLUSION: Separating freehand scanning from image capture and measurement resulted in a faster scan and altered workflow. Removing repetitive tasks may allow more attention to be directed identifying fetal malformation. Further work is required to improve the image plane detection algorithm for use in real time.

Indicators of recent COVID-19 infection status: findings from a large occupational cohort of staff and postgraduate research students from a UK university.

BACKGROUND: Researchers conducting cohort studies may wish to investigate the effect of episodes of COVID-19 illness on participants. A definitive diagnosis of COVID-19 is not always available, so studies have to rely on proxy indicators. This paper seeks to contribute evidence that may assist the use and interpretation of these COVID-indicators. METHODS: We described five potential COVID-indicators: self-reported core symptoms, a symptom algorithm; self-reported suspicion of COVID-19; self-reported external results; and home antibody testing based on a 'lateral flow' antibody (IgG/IgM) test cassette. Included were staff and postgraduate research students at a large London university who volunteered for the study and were living in the UK in June 2020. Excluded were those who did not return a valid antibody test result. We provide descriptive statistics of prevalence and overlap of the five indicators. RESULTS: Core symptoms were the most common COVID-indicator (770/1882 participants positive, 41%), followed by suspicion of COVID-19 (n = 509/1882, 27%), a positive symptom algorithm (n = 298/1882, 16%), study antibody lateral flow positive (n = 124/1882, 7%) and a positive external test result (n = 39/1882, 2%), thus a 20-fold difference between least and most common. Meeting any one indicator increased the likelihood of all others, with concordance between 65 and 94%. Report of a low suspicion of having had COVID-19 predicted a negative antibody test in 98%, but positive suspicion predicted a positive antibody test in only 20%. Those who reported previous external antibody tests were more likely to have received a positive result from the external test (24%) than the study test (15%). CONCLUSIONS: Our results support the use of proxy indicators of past COVID-19, with the caveat that none is perfect. Differences from previous antibody studies, most significantly in lower proportions of participants positive for antibodies, may be partly due to a decline in antibody detection over time. Subsequent to our study, vaccination may have further complicated the interpretation of COVID-indicators, only strengthening the need to critically evaluate what criteria should be used to define COVID-19 cases when designing studies and interpreting study results.

A fast navigator (fastNAV) for prospective respiratory motion correction in first-pass myocardial perfusion imaging.

PURPOSE: To develop and evaluate a fast respiratory navigator (fastNAV) for cardiac MR perfusion imaging with subject-specific prospective slice tracking. METHODS: A fastNAV was developed for dynamic contrast-enhanced cardiac MR perfusion imaging by combining spatially nonselective saturation with slice-selective tip-up and slice-selective excitation pulses. The excitation slice was angulated from the tip-up slice in the transverse plane to overlap only in the right hemidiaphragm for suppression of signal outside the right hemidiaphragm. A calibration scan was developed to enable the estimation of subject-specific tracking factors. Perfusion imaging using subject-specific fastNAV-based slice tracking was then compared to a conventional sequence (ie, without slice tracking) in 10 patients under free-breathing conditions. Respiratory motion in perfusion images was quantitatively assessed by measuring the average overlap of the left ventricle across images (avDice, 0:no overlap/1:perfect overlap) and the average displacement of the center of mass of the left ventricle (avCoM). Image quality was subjectively assessed using a 4-point scoring system (1: poor, 4: excellent). RESULTS: The fastNAV calibration was successfully performed in all subjects (average tracking factor of 0.46 ± 0.13, R = 0.94 ± 0.03). Prospective motion correction using fastNAV led to higher avDice (0.94 ± 0.02 vs. 0.90 ± 0.03, P < .001) and reduced avCoM (4.03 ± 0.84 vs. 5.22 ± 1.22, P < .001). There were no statistically significant differences between the 2 sequences in terms of image quality (both sequences: median = 3 and interquartile range = 3-4, P = 1). CONCLUSION: fastNAV enables fast and robust right hemidiaphragm motion tracking in a perfusion sequence. In combination with subject-specific slice tracking, fastNAV reduces the effect of respiratory motion during free-breathing cardiac MR perfusion imaging.

Interventional cardiac MRI using an add-on parallel transmit MR system: In vivo experience in sheep.

PURPOSE: We present in vivo testing of a parallel transmit system intended for interventional MR-guided cardiac procedures. METHODS: The parallel transmit system was connected in-line with a conventional 1.5 Tesla MRI system to transmit and receive on an 8-coil array. The system used a current sensor for real-time feedback to achieve real-time current control by determining coupling and null modes. Experiments were conducted on 4 Charmoise sheep weighing 33.9-45.0 kg with nitinol guidewires placed under X-ray fluoroscopy in the atrium or ventricle of the heart via the femoral vein. Heating tests were done in vivo and post-mortem with a high RF power imaging sequence using the coupling mode. Anatomical imaging was done using a combination of null modes optimized to produce a useable B1 field in the heart. RESULTS: Anatomical imaging produced cine images of the heart comparable in quality to imaging with the quad mode (all channels with the same amplitude and phase). Maximum observed temperature increases occurred when insulation was stripped from the wire tip. These were 4.1℃ and 0.4℃ for the coupling mode and null modes, respectively for the in vivo case; increasing to 6.0℃ and 1.3℃, respectively for the ex vivo case, because cooling from blood flow is removed. Heating < 0.1℃ was observed when insulation was not stripped from guidewire tips. In all tests, the parallel transmit system managed to reduce the temperature at the guidewire tip. CONCLUSION: We have demonstrated the first in vivo usage of an auxiliary parallel transmit system employing active feedback-based current control for interventional MRI with a conventional MRI scanner.