Faculty Bibliography

Cardiac MRI tagging is a valuable technique for evaluating regional heart function. Currently, there are a number of different techniques for analyzing the tagged images. Specifically, k-space-based analysis techniques showed to be much faster than image-based techniques, where harmonic-phase (HARP) and sine-wave modeling (SinMod) stand as two famous techniques of the former group, which are frequently used in clinical studies. In this study, we compared HARP and SinMod and studied inter-observer variability between the two techniques for evaluating myocardial strain and apical-to-base torsion in numerical phantom, nine healthy controls, and thirty diabetic patients. Based on the ground-truth numerical phantom measurements (strain = -20% and rotation angle = -4.4°), HARP and SinMod resulted in overestimation (in absolute value terms) of strain by 1% and 5% (strain values), and of rotation angle by 0.4° and 2.0°, respectively. For the in-vivo results, global strain and torsion ranges were -10.6% to -35.3% and 1.8°/cm to 12.7°/cm in patients, and -17.8% to -32.7% and 1.8°/cm to 12.3°/cm in volunteers. On average, SinMod overestimated strain measurements by 5.7% and 5.9% (strain values) in the patients and volunteers, respectively, compared to HARP, and overestimated torsion measurements by 2.9°/cm and 2.5°/cm in the patients and volunteers, respectively, compared to HARP. Location-wise, the ranges for basal, mid-ventricular, and apical strain in patients (volunteers) were -8.4% to -31.5% (-11.6% to -33.3%), -6.3% to -37.2% (-17.8% to -33.3%), and -5.2% to -38.4% (-20.0% to -33.2%), respectively. SinMod overestimated strain in the basal, mid-ventricular, and apical slices by 4.7% (5.7%), 5.9% (5.5%), and 8.9% (6.8%), respectively, compared to HARP in the patients (volunteers). Nevertheless, there existed good correlation between the HARP and SinMod measurements. Finally, there were no significant strain or torsion measurement differences between patients and volunteers. There existed good inter-observer agreement, as all measurement differences lied within the Bland-Altman ± 2 standard-deviation (SD) difference limits. In conclusion, despite the consistency of the results by either HARP or SinMod and acceptable agreement of the generated strain and torsion patterns by both techniques, SinMod systematically overestimated the measurements compared to HARP. Under current operating conditions, the measurements from HARP and SinMod cannot be used interchangeably.

Virtual reality (VR) systems can offer benefits of improved ergonomics, but their resolution may currently be limited for the detection of small features. For detection of lung nodules, we compared the performance of VR versus standard picture archiving and communication system (PACS) monitor. Four radiologists and 1 novice radiologist reviewed axial computed tomography (CTs) of the thorax using standard PACS monitors (SM) and a VR system (HTC Vive, HTC). In this study, 3 radiologists evaluated axial lung-window CT images of a Lungman phantom. One radiologist and the novice radiologist reviewed axial lung-window patient CT thoracic images (32 patients). This HIPAA-compliant study was approved by the institutional review board. Detection of 227 lung nodules on patient CTs did not result in different sensitivity with SM compared with VR. Detection of 23 simulated Lungman phantom lung nodules on CT with SM resulted in statistically greater sensitivity (78.3%) than with VR (52.2%, P = .041) for 1 of 3 radiologists. The trend was similar but not significant for the other radiologists. There was no significant difference in the time spent by readers reviewing CT images with VR versus SM. These findings indicate that performance of a commercially available VR system for detection of lung nodules may be similar to traditional radiology monitors for assessment of small lung nodules on CTs of the thorax for most radiologists. These results, along with the potential of improving ergonomics for radiologists, are promising for the future development of VR in diagnostic radiology.

Late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) is the gold standard for imaging myocardial viability. An important application of LGE CMR is the assessment of the location and extent of the myocardial scar in patients with ventricular tachycardia (VT), which allows for more accurate identification of the ablation targets. However, a large percentage of patients with VT have cardiac implantable electronic devices (CIEDs), which is a relative contraindication for cardiac magnetic resonance imaging due to safety and image artifact concerns. Previous studies showed that these patients can be safely scanned on 1.5 T scanners provided that an adequate imaging protocol is adopted. Nevertheless, imaging patients with a CIED result in metal artifacts due to the strong frequency off-resonance effects near the device; therefore, the spins in the surrounding myocardium are not completely inverted, and thus give rise to hyperintensity artifacts. These artifacts obscure the myocardial scar tissue and limit the ability to study the correlation between the myocardial scar structure and the electro-anatomical map during catheter ablation. In this study, we developed a modified inversion recovery technique to alleviate the CIED-induced metal artifacts and improve the diagnostic image quality of LGE images in patients with CIEDs without increasing scan time or requiring additional hardware. The developed technique was tested in phantom experiments and in vivo scans, which showed its capability for suppressing the hyperintensity artifacts without compromising myocardium nulling in the resulting LGE images.

Magnetic resonance imaging (MRI) is an extremely useful tool for the detection and characterization of numerous pathologic processes. Although patients can benefit from the use of MRI, claustrophobia is a major issue in some cases. This fear alone can lead to cancellation of the scanning procedure in some cases and the need for conscious sedation in others. Patient anxiety during the scan can also lead to increased motion-related artifacts on the images with associated degradation of the diagnostic quality of the study. To alleviate these problems, our team developed a virtual reality (VR) tool (app) to educate patients about MRI and simulate the experience of actually being scanned. The app is totally immersive and incorporates both the visual and auditory sensations that patients encounter during an MRI scan. Patients also learn about potential conditions and implanted devices that may preclude the safe performance of the examination. This VR tool not only educates patients about MRI and its importance in their care, but also allows them to virtually experience what it is like to have a MRI scan. This technology has the potential to decrease both claustrophobic cancellations and patient anxiety before a MRI scan.

Quantifying the amount of brown adipose tissue (BAT) within white adipose tissue (WAT) in human depots may serve as a target to combat obesity. We aimed to quantify proton density fat fraction (PDFF) of BAT and WAT in relatively pure and in mixed preparation using water-fat imaging. Three ex-vivo experiments were performed at 3 T using excised interscapular BAT and inguinal/subcutaneous WAT from mice. The first two experiments consisted of BAT and WAT in separate tubes, and the third used mixed preparation with graded quantities of BAT and WAT. To investigate the influence of partial volume on PDFF metrics, low (

RATIONALE AND OBJECTIVES:The study aimed to determine if intrathoracic fat volumes are associated with the presence and severity of systemic sclerosis (SSc), defined by the presence of pulmonary arterial hypertension (PAH). MATERIALS AND METHODS:A total of 265 patients were included in the study, 202 of whom had SSc (134 had SSc with no PAH and 68 had SSc-associated PAH) and who underwent high-resolution computed tomography, and 63 controls who underwent coronary computed tomography angiography with calcium scoring. Intrathoracic and epicardial (EFV) fat volumes were quantified by manual tracing of the mediastinum and the pericardium, the difference of which represents the extrapericardial fat volume. Associations between these three fat volumes and the presence and severity of SSc, adjusted for cardiovascular risk factors and interstitial lung disease, were evaluated by logistic regression analysis. RESULTS:Of the 202 patients with SSc, the mean age was 55 years (ranged from 20 to 86), and 79% (159 of 202) were women. Adjusted EFV (odds ratio [OR]: 1.065; 95% confidence interval [CI]: 1.046-1.084, P = < 0.0001), extrapericardial fat volume (OR: 1.028, 95% CI: 1.017-1.038, P = < 0.0001), and intrathoracic fat volume (OR: 1.033, 95% CI: 1.023-1.043, P = 0.001) were associated with the presence of SSc. Only EFV was associated with SSc severity (adjusted OR: 1.010, 95% CI: 1.003-1.018, P = 0.007). CONCLUSION:Increased epicardial fat volume is associated with the presence and severity of SSc, independent of cardiovascular risk factors and interstitial lung disease.

BACKGROUND:Frequent premature ventricular complexes (PVCs) have been associated with increased mortality. However, the optimal approach to the risk stratification of these patients is unclear. OBJECTIVE:The purpose of this study was to prospectively assess the use of cardiac magnetic resonance imaging (MRI) and programmed ventricular stimulation to identify patients with PVCs undergoing radiofrequency ablation at risk for adverse long-term outcomes. METHODS:A total of 321 consecutive patients (52 ± 15 years; 157 men [49%]; left ventricular ejection fraction 51% ± 12%) underwent PVC ablation between 2004 and 2015, preceded by cardiac MRI to assess for structural heart disease (SHD). Programmed stimulation was performed at the time of the ablation procedure. If ventricular tachycardia (VT) was induced in the presence of SHD, an implantable cardioverter-defibrillator (ICD) was implanted. RESULTS:SHD was identified by MRI in 64 patients (20%), and sustained monomorphic VT was inducible in 15 patients (5%). Fourteen patients had both SHD and inducible VT, and received an ICD after the procedure. The primary endpoint of VT/ventricular fibrillation or death was met in 15 patients after a median 20 months of follow-up. The combination of SHD by MRI and VT inducibility conferred independently an increased risk of adverse outcome (multivariate hazard ratio 25.73, 95% confidence interval 6.74-98.20; P <.001). CONCLUSION:Preablation cardiac MRI and programmed stimulation can be useful for risk stratification in patients with frequent PVCs. Patients with inducible VT in the setting of SHD may benefit from ICD implantation after ablation regardless of left ventricular ejection fraction.

BACKGROUND:Knowledge of complex arrhythmogenic substrates can help plan ventricular tachycardia (VT) ablation in patients with idiopathic dilated cardiomyopathy (DCM). OBJECTIVE:The purpose of this study was to assess whether preprocedural late gadolinium enhancement magnetic resonance imaging (LGE-MRI) can improve ablation outcomes in DCM. METHODS:Consecutive patients (N = 96) with idiopathic DCM underwent VT ablation with open-irrigated catheters (2006-2016). Before 2012, LGE-MRI was not performed at our institution in patients with implanted devices, but it has been performed routinely in all patients after implementation of a new MRI protocol in 2012. We retrospectively compared acute and long-term outcomes of initial VT ablation procedures in patients with (n = 41) and those without (n = 55) preprocedural LGE-MRI. Procedural outcome was classified as successful if VT was not inducible postablation. RESULTS:The 2 groups had a similar mean age and ejection fraction, comorbidities, and frequency of epicardial ablation. Preablation LGE-MRI was independently associated with improved procedural success (63% vs 24%) by logistic regression analysis (adjusted odds ratio [OR] 7.86, P <.001). This result was consistent even when patients with nondiagnostic MRIs due to artifact were included in the imaging group (OR 4.87, P = .005). Preablation imaging was also associated with improved survival free of the composite endpoint of VT recurrence, heart transplantation, or death, which was met by 11 (27%) and 33 (60%) patients in the imaging and no imaging groups, respectively, after median 7.6 months of follow-up (unadjusted log-rank P = .02). However, there was no association with long-term outcomes after adjustment for other covariates. CONCLUSION:Preprocedural imaging with LGE-MRI may be associated with improved outcomes of VT ablation in DCM.

Aims/UNASSIGNED:Magnetic resonance imaging (MRI) has been reported to be safe in patients with cardiac implantable electronic devices (CIED) provided a specific protocol is followed. The objective of this study was to assess whether this is also true for patients excluded from published protocols. Methods and results/UNASSIGNED:A total of 160 MRIs were obtained in 142 consecutive patients with CIEDs [106 patients had an implantable cardioverter defibrillator (ICD) and 36 had a pacemaker implanted] using an adapted, pre-specified protocol. A cardiac MRI was performed in 95 patients, and a spinal/brain MRI was performed in 47 patients. Forty-six patients (32%) had either abandoned leads (n = 10), and/or were pacemaker dependent with an implanted ICD (n = 19), had recently implanted CIEDs (n = 1), and/or had a CIED device with battery depletion (n = 2), and/or a component of the CIED was recalled or on advisory (n = 32). No major complications occurred. Some device parameters changed slightly, but significantly, right after or at 1-week post-MRI without requiring any reprogramming. In one patient with an ICD on advisory, the pacing rate changed inexplicably during one of his two MRIs from 90 to 50 b.p.m. Conclusion/UNASSIGNED:Using a pre-specified protocol, cardiac and non-cardiac MRIs were performed in CIED patients with pacemaker dependency, abandoned leads, or depleted batteries without occurrence of major adverse events. Patients with devices on advisory need to be monitored carefully during MRI, especially if they are pacemaker dependent.

The incidence of congenital heart disease (CHD) has been increasing in the adult patient population in part as a result of better patient survival. Patients with more severe CHD are living longer. Nearly all adults with known CHD require periodic imaging as a means of monitoring their disease process. Furthermore, adult patients with suspected CHD require imaging as a means of definitive diagnosis. As a result, it is important for both the referring clinician and the imager to be aware of the most appropriate imaging modality needed to obtain the data most needed to direct the next steps in patient care. Imaging procedures for the diagnosis of known or suspected CHD in the adult include chest radiography, fluoroscopy, echocardiography, nuclear scintigraphy, cardiac-gated CT, MRI, and cardiac catheterization/angiography. The physician trying to diagnose these often complex conditions needs complete and reliable information that includes details about intracardiac and vascular anatomy, hemodynamics, and function. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.