Automatic segmentation of peripheral arteries and veins in ferumoxytol-enhanced MR angiography

PURPOSE

To automate the segmentation of the peripheral arteries and veins in the lower extremities based on ferumoxytol-enhanced MR angiography (FE-MRA).

METHODS

Our automated pipeline has 2 sequential stages. In the first stage, we used a 3D U-Net with local attention gates, which was trained based on a combination of the Focal Tversky loss with region mutual loss under a deep supervision mechanism to segment the vasculature from the high-resolution FE-MRA datasets. In the second stage, we used time-resolved images to separate the arteries from the veins. Because the ultimate segmentation quality of the arteries and veins relies on the performance of the first stage, we thoroughly evaluated the different aspects of the segmentation network and compared its performance in blood vessel segmentation with currently accepted state-of-the-art networks, including Volumetric-Net, DeepVesselNet-FCN, and Uception.

RESULTS

We achieved a competitive F1 = 0.8087 and recall = 0.8410 for blood vessel segmentation compared with F1 = (0.7604, 0.7573, 0.7651) and recall = (0.7791, 0.7570, 0.7774) obtained with Volumetric-Net, DeepVesselNet-FCN, and Uception. For the artery and vein separation stage, we achieved F1 = (0.8274/0.7863) in the calf region, which is the most challenging region in peripheral arteries and veins segmentation.

CONCLUSION

Our pipeline is capable of fully automatic vessel segmentation based on FE-MRA without need for human interaction in <4 min. This method improves upon manual segmentation by radiologists, which routinely takes several hours.

Temporally aware volumetric generative adversarial network-based MR image reconstruction with simultaneous respiratory motion compensation: Initial feasibility in 3D dynamic cine cardiac MRI

PURPOSE

Develop a novel three-dimensional (3D) generative adversarial network (GAN)-based technique for simultaneous image reconstruction and respiratory motion compensation of 4D MRI. Our goal was to enable high-acceleration factors 10.7X-15.8X, while maintaining robust and diagnostic image quality superior to state-of-the-art self-gating (SG) compressed sensing wavelet (CS-WV) reconstruction at lower acceleration factors 3.5X-7.9X.

METHODS

Our GAN was trained based on pixel-wise content loss functions, adversarial loss function, and a novel data-driven temporal aware loss function to maintain anatomical accuracy and temporal coherence. Besides image reconstruction, our network also performs respiratory motion compensation for free-breathing scans. A novel progressive growing-based strategy was adapted to make the training process possible for the proposed GAN-based structure. The proposed method was developed and thoroughly evaluated qualitatively and quantitatively based on 3D cardiac cine data from 42 patients.

RESULTS

Our proposed method achieved significantly better scores in general image quality and image artifacts at 10.7X-15.8X acceleration than the SG CS-WV approach at 3.5X-7.9X acceleration (4.53 ± 0.540 vs. 3.13 ± 0.681 for general image quality, 4.12 ± 0.429 vs. 2.97 ± 0.434 for image artifacts, P < .05 for both). No spurious anatomical structures were observed in our images. The proposed method enabled similar cardiac-function quantification as conventional SG CS-WV. The proposed method achieved faster central processing unit-based image reconstruction (6 s/cardiac phase) than the SG CS-WV (312 s/cardiac phase).

CONCLUSION

The proposed method showed promising potential for high-resolution (1 mm³ ) free-breathing 4D MR data acquisition with simultaneous respiratory motion compensation and fast reconstruction time.

Slice encoding for the reduction of outflow signal artifacts in cine balanced SSFP imaging

PURPOSE

Standard balanced SSFP (bSSFP) cine MRI often suffers from blood outflow artifacts. We propose a method that spatially encodes these outflowing spins to reduce their effects in the intended slice.

METHODS

Bloch simulations were performed to characterize through-plane flow and to investigate how the use of phase encoding along the slice select's direction ("slice encoding") could alleviate its issues. Phantom scans and in vivo cines were acquired on a 3T system, comparing the standard 2D acquisition to the proposed slice-encoding method. Nineteen healthy volunteers were recruited for short-axis and horizontal long-axis oriented scans. An expert radiologist evaluated each slice-encoded/standard cine pairs in a rank comparison test and graded their quality on a 1-5 scale. The grades were used for a nonparametric paired evaluation for independent samples with a null hypothesis that there was no statistical difference between the two quality-grade distributions for α = 0.05 significance.

RESULTS

Bloch simulation results demonstrated this technique's feasibility, showing a fully resolved slice profile given a sufficient number of slice encodes. These results were confirmed with the phantom experiments. Each in vivo slice-encoded cine had a higher quality than its corresponding standard acquisition. The nonparametric paired evaluation came to 0.01 significance, encouraging us to reject the null hypothesis and conclude that slice-encoding effectively works in reducing outflow effects.

CONCLUSION

The slice-encoding balanced SSFP technique is helpful in mitigating outflow effects and is achievable within a single breath hold, being a useful alternative for cases in which the flow artifacts are significant.

Right Ventricular Function and T1-Mapping in Boys With Duchenne Muscular Dystrophy

BACKGROUND

Clinical management of boys with Duchenne muscular dystrophy (DMD) relies on in-depth understanding of cardiac involvement, but right ventricular (RV) structural and functional remodeling remains understudied.

PURPOSE

To evaluate several analysis methods and identify the most reliable one to measure RV pre- and postcontrast T1 (RV-T1) and to characterize myocardial remodeling in the RV of boys with DMD.

STUDY TYPE

Prospective.

POPULATION

Boys with DMD (N = 27) and age-/sex-matched healthy controls (N = 17) from two sites.

FIELD STRENGTH/SEQUENCE

3.0 T using balanced steady state free precession, motion-corrected phase sensitive inversion recovery and modified Look-Locker inversion recovery sequences.

ASSESSMENT

Biventricular mass (Mi), end-diastolic volume (EDVi) and ejection fraction (EF) assessment, tricuspid annular excursion (TAE), late gadolinium enhancement (LGE), pre- and postcontrast myocardial T1 maps. The RV-T1 reliability was assessed by three observers in four different RV regions of interest (ROI) using intraclass correlation (ICC).

STATISTICAL TESTS

The Wilcoxon rank sum test was used to compare RV-T1 differences between DMD boys with negative LGE(-) or positive LGE(+) and healthy controls. Additionally, correlation of precontrast RV-T1 with functional measures was performed. A P-value <0.05 was considered statistically significant.

RESULTS

A 1-pixel thick RV circumferential ROI proved most reliable (ICC > 0.91) for assessing RV-T1. Precontrast RV-T1 was significantly higher in boys with DMD compared to controls. Both LGE(-) and LGE(+) boys had significantly elevated precontrast RV-T1 compared to controls (1543 [1489-1597] msec and 1550 [1402-1699] msec vs. 1436 [1399-1473] msec, respectively). Compared to healthy controls, boys with DMD had preserved RVEF (51.8 [9.9]% vs. 54.2 [7.2]%, P = 0.31) and significantly reduced RVMi (29.8 [9.7] g vs. 48.0 [15.7] g), RVEDVi (69.8 [29.7] mL/m² vs. 89.1 [21.9] mL/m² ), and TAE (22.0 [3.2] cm vs. 26.0 [4.7] cm). Significant correlations were found between precontrast RV-T1 and RVEF (β = -0.48%/msec) and between LV-T1 and LVEF (β = -0.51%/msec).

DATA CONCLUSION

Precontrast RV-T1 is elevated in boys with DMD compared to healthy controls and is negatively correlated with RVEF.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 2.

Patient adherence to LungRADS recommendations at an academic institution

e18592

Background: The National Lung Screening Trial (NLST) demonstrated a 20% reduction in lung cancer mortality when screened with low dose computed tomography (LDCT) as opposed to chest radiography. Notably, participants’ adherence to the screening protocol was 90%. To date, published evidence on the adherence of patients enrolled in clinical lung cancer screening (LCS) programs to LungRADS recommendations is limited. We investigate the adherence rate at our institution and determine the predictors of non-adherence to LungRADS recommendations. Methods: We performed a retrospective analysis on patients aged 50-80 years at time of baseline screen with initial screening exam at our institution between Jan 1, 2015 and Jan 12, 2021. Patients were excluded if 1) their follow-up period was insufficient to determine adherence as of Jan 28, 2021, 2) the follow-up recommendation was inconsistent with LungRADS guidelines, or 3) they died before the expected follow-up date. Adherence was defined as completion of recommended or more invasive follow-up at our institution within 12 months for LungRADS 0, 15 months for LungRADS 1/2, 9 months for LungRADS 3, 5 months for LungRADS 4A, and 3 months for LungRADS 4B/4X. A univariate logistic regression was used to determine predictors of non-adherence. Results: Among the 2120 eligible patients, 1266 (60%) were male and 854 (40%) were female with a median age of 65 at the baseline screen. One thousand four hundred and seventy-seven (70%) patients identified as White, 286 (13%) declared another racial group, and 357 (17%) did not disclose their race. One hundred and nine (5%) patients identified as Hispanic and 165 (8%) patients did not state their ethnicity. There were 1113 (53%) former smokers, 748 (35%) current smokers, and 259 (12%) patients of unspecified smoking status. Median tobacco exposure was 30 pack years (range 0.15 to 240). Fifty-seven percent of patients had private or commercial insurance while 39% had Medicare as primary insurance (3 patients were unspecified). The distribution of baseline LungRADS scores was 0: < 1%, 1: 14%, 2: 71%, 3: 7%, 4A: 4%, 4B: 2%, and 4X: < 1%. Overall adherence was 31% with 0: 38%, 1: 21%, 2: 27%, 3: 46%, 4A: 68%, 4B: 80%, and 4X: 100%. Of the 1463 non-adherent patients, 528 completed a follow-up exam beyond the expected date while 935 did not have any follow-up before the end of the study. Patients who were over 65 at baseline screen (OR = 1.34, 95% CI: 1.11, 1.61), former smokers (OR = 1.24, 95% CI: 1.02, 1.52), had Medicare insurance (OR = 1.35 95% CI: 1.12, 1.63), or had LungRADS 3/4 (referent: LR 1/2, OR = 4.29, 95% CI: 3.32, 5.55) were more likely to be adherent. Conclusions: Patient adherence to LungRADS recommendations at time of baseline screen in clinical practice is suboptimal, particularly among those with negative screens (LungRADS 1/2), with a non-adherence rate of > 70%. Baseline LungRADS scores, age, smoking status, and insurance are predictive of LCS non-adherence.

Pulmonary vein and left atrial posterior wall isolation for the treatment of atrial fibrillation: Comparable outcomes for adults with congenital heart disease

INTRODUCTION

Optimal treatment strategies for ACHD with AF are unknown. This study sought to assess outcomes of pulmonary vein isolation (PVI) ± left atrial (LA), posterior wall isolation (PWI) for adults with congenital heart disease (ACHD), and atrial fibrillation (AF).

METHODS

A retrospective review of all cryoballoon (CB) PVI ± PWI procedures at a single center over a 3-year period were performed. Clinical characteristics and outcomes for patients with and without ACHD were compared. The primary outcome was the occurrence of atrial tachyarrhythmia at 12-months postablation after a 90-day blanking period.

RESULTS

Three-hundred and sixteen patients (mean: 63 ± 12 years, [63% male]) underwent CB PVI ± PWI during the study, including 31 (10%) ACHD (simple 35%, moderate 39% complex 26%; nonparoxysmal AF in 52%). ACHD was younger (51 vs. 64 years; p < .001) with a lower CHADS₂ DS₂ -VASc score (1.2 vs. 2.1; p = .001) but had a greater LA diameter (4.9 vs. 4.0 cm; p < .001) and a number of prior cardioversions (0.9 vs. 0.4; p < .001) versus controls. 12-month freedom from recurrent AF was similar for ACHD and controls (76% vs. 80%; p = .6) and remained nonsignificant in multivariate analysis (hazard ratio: 1.8, 95% confidence interval: 0.7-5.1; p = .22). At 12-months postablation, 75% of ACHD versus 93% of control patients were off antiarrhythmic drug therapy (p = .07).

CONCLUSION

This study demonstrates younger age and lower conventional stroke risk, yet clinically advanced AF for ACHD relative to controls. CB PVI ± PWI was an effective strategy for the treatment of AF among all forms of ACHD with similar 12-month outcomes as compared to controls.

Retrospective respiratory motion correction in cardiac cine MRI reconstruction using adversarial autoencoder and unsupervised learning

The aim of this study was to develop a deep neural network for respiratory motion compensation in free-breathing cine MRI and evaluate its performance. An adversarial autoencoder network was trained using unpaired training data from healthy volunteers and patients who underwent clinically indicated cardiac MRI examinations. A U-net structure was used for the encoder and decoder parts of the network and the code space was regularized by an adversarial objective. The autoencoder learns the identity map for the free-breathing motion-corrupted images and preserves the structural content of the images, while the discriminator, which interacts with the output of the encoder, forces the encoder to remove motion artifacts. The network was first evaluated based on data that were artificially corrupted with simulated rigid motion with regard to motion-correction accuracy and the presence of any artificially created structures. Subsequently, to demonstrate the feasibility of the proposed approach in vivo, our network was trained on respiratory motion-corrupted images in an unpaired manner and was tested on volunteer and patient data. In the simulation study, mean structural similarity index scores for the synthesized motion-corrupted images and motion-corrected images were 0.76 and 0.93 (out of 1), respectively. The proposed method increased the Tenengrad focus measure of the motion-corrupted images by 12% in the simulation study and by 7% in the in vivo study. The average overall subjective image quality scores for the motion-corrupted images, motion-corrected images and breath-held images were 2.5, 3.5 and 4.1 (out of 5.0), respectively. Nonparametric-paired comparisons showed that there was significant difference between the image quality scores of the motion-corrupted and breath-held images (P < .05); however, after correction there was no significant difference between the image quality scores of the motion-corrected and breath-held images. This feasibility study demonstrates the potential of an adversarial autoencoder network for correcting respiratory motion-related image artifacts without requiring paired data.

T1-Mapping and extracellular volume estimates in pediatric subjects with Duchenne muscular dystrophy and healthy controls at 3T

BACKGROUND

Cardiovascular disease is the leading cause of death in patients with Duchenne muscular dystrophy (DMD)-a fatal X-linked genetic disorder. Late gadolinium enhancement (LGE) imaging is the current gold standard for detecting myocardial tissue remodeling, but it is often a late finding. Current research aims to investigate cardiovascular magnetic resonance (CMR) biomarkers, including native (pre-contrast) T1 and extracellular volume (ECV) to evaluate the early on-set of microstructural remodeling and to grade disease severity. To date, native T1 measurements in DMD have been reported predominantly at 1.5T. This study uses 3T CMR: (1) to characterize global and regional myocardial pre-contrast T1 differences between healthy controls and LGE + and LGE- boys with DMD; and (2) to report global and regional myocardial post-contrast T1 values and myocardial ECV estimates in boys with DMD, and (3) to identify left ventricular (LV) T1-mapping biomarkers capable of distinguishing between healthy controls and boys with DMD and detecting LGE status in DMD.

METHODS

Boys with DMD (N = 28, 13.2 ± 3.1 years) and healthy age-matched boys (N = 20, 13.4 ± 3.1 years) were prospectively enrolled and underwent a 3T CMR exam including standard functional imaging and T1 mapping using a modified Look-Locker inversion recovery (MOLLI) sequence. Pre-contrast T1 mapping was performed on all boys, but contrast was administered only to boys with DMD for post-contrast T1 and ECV mapping. Global and segmental myocardial regions of interest were contoured on mid LV T1 and ECV maps. ROI measurements were compared for pre-contrast myocardial T1 between boys with DMD and healthy controls, and for post-contrast myocardial T1 and ECV between LGE + and LGE- boys with DMD using a Wilcoxon rank-sum test. Results are reported as median and interquartile range (IQR). p-Values < 0.05 were considered significant. Receiver Operating Characteristic analysis was used to evaluate a binomial logistic classifier incorporating T1 mapping and LV function parameters in the tasks of distinguishing between healthy controls and boys with DMD, and detecting LGE status in DMD. The area under the curve is reported.

RESULTS

Boys with DMD had significantly increased global native T1 [1332 (60) ms vs. 1289 (56) ms; p = 0.004] and increased within-slice standard deviation (SD) [100 (57) ms vs. 74 (27) ms; p = 0.001] compared to healthy controls. LGE- boys with DMD also demonstrated significantly increased lateral wall native T1 [1322 (68) ms vs. 1277 (58) ms; p = 0.001] compared to healthy controls. LGE + boys with DMD had decreased global myocardial post-contrast T1 [565 (113) ms vs 635 (126) ms; p = 0.04] and increased global myocardial ECV [32 (8) % vs. 28 (4) %; p = 0.02] compared to LGE- boys. In all classification tasks, T1-mapping biomarkers outperformed a conventional biomarker, LV ejection fraction. ECV was the best performing biomarker in the task of predicting LGE status (AUC = 0.95).

CONCLUSIONS

Boys with DMD exhibit elevated native T1 compared to healthy, sex- and age-matched controls, even in the absence of LGE. Post-contrast T1 and ECV estimates from 3T CMR are also reported here for pediatric patients with DMD for the first time and can distinguish between LGE + from LGE- boys. In all classification tasks, T1-mapping biomarkers outperform a conventional biomarker, LVEF.

The ASOS Surgical Risk Calculator: development and validation of a tool for identifying African surgical patients at risk of severe postoperative complications

BACKGROUND

The African Surgical Outcomes Study (ASOS) showed that surgical patients in Africa have a mortality twice the global average. Existing risk assessment tools are not valid for use in this population because the pattern of risk for poor outcomes differs from high-income countries. The objective of this study was to derive and validate a simple, preoperative risk stratification tool to identify African surgical patients at risk for in-hospital postoperative mortality and severe complications.

METHODS

ASOS was a 7-day prospective cohort study of adult patients undergoing surgery in Africa. The ASOS Surgical Risk Calculator was constructed with a multivariable logistic regression model for the outcome of in-hospital mortality and severe postoperative complications. The following preoperative risk factors were entered into the model; age, sex, smoking status, ASA physical status, preoperative chronic comorbid conditions, indication for surgery, urgency, severity, and type of surgery.

RESULTS

The model was derived from 8799 patients from 168 African hospitals. The composite outcome of severe postoperative complications and death occurred in 423/8799 (4.8%) patients. The ASOS Surgical Risk Calculator includes the following risk factors: age, ASA physical status, indication for surgery, urgency, severity, and type of surgery. The model showed good discrimination with an area under the receiver operating characteristic curve of 0.805 and good calibration with c-statistic corrected for optimism of 0.784.

CONCLUSIONS

This simple preoperative risk calculator could be used to identify high-risk surgical patients in African hospitals and facilitate increased postoperative surveillance.

CLINICAL TRIAL REGISTRATION

NCT03044899.

A 63-Year-Old Woman With Neurofibromatosis Type 1 and Pulmonary Hypertension With Worsening Hypoxemia

CASE PRESENTATION

A 63-year-old woman with a history of neurofibromatosis type-1 (NF-1) and pulmonary arterial hypertension (PAH) thought to be secondary to the NF-1 presented with a few weeks of worsening dyspnea on exertion. She took no medications other than sildenafil for her pulmonary hypertension (PH). She denied tobacco, alcohol, and illicit or anorectic drug use. She had previously worked as a waitress. Her mother and her brother had NF-1 but no PH or lung disease.

Delayed Development of Multiple Pancreaticoduodenal Arcade Pseudoaneurysms after Abdominal Trauma

This case report demonstrates development and progressive enlargement of multiple pancreaticoduodenal arcade pseudoaneurysms using computed tomography angiographies over a period of 5 weeks after abdominal trauma. The mechanism of pseudoaneurysm formation, as shown by serial imaging, attributed to preexisting celiac axis stenosis by the median arcuate ligament, posttraumatic celiac artery dissection, and secondary occlusion of proper hepatic artery resulting in elevation of pressure and flow in the pancreaticoduodenal arcade and rupture of small arterial branches. Successful pseudoaneurysm occlusion was achieved through arterial embolization.