Amir Ali Rahsepar

The Safety of Cardiac and Thoracic Magnetic Resonance Imaging in Patients with Cardiac Implantable Electronic Devices

RATIONALE AND OBJECTIVES Studies reporting the safety of magnetic resonance imaging (MRI) in patients with a cardiac implantable electronic device (CIED) have mostly excluded examinations with the device in the magnet isocenter. The purpose of this study was to describe the safety of cardiac and thoracic spine MRI in patients with a CIED. MATERIALS AND METHODS The medical records of patients with a CIED who underwent a cardiac or thoracic spine MRI between January 2011 and December 2014 were reviewed. Devices were interrogated before and after imaging with reprogramming to asynchronous pacing in pacemaker-dependent patients. The clinical interpretability of the MRI and peak and average specific absorption rates (SARs, W/kg) achieved were determined. RESULTS Fifty-eight patients underwent 51 cardiac and 11 thoracic spine MRI exams. Twenty-nine patients had a pacemaker and 29 had an implantable cardioverter defibrillator. Seventeen percent (n = 10) were pacemaker dependent. Fifty-one patients (89%) had non-MRI-conditional devices. There were no clinically significant changes in atrial and ventricular sensing, impedance, and threshold measurements. There were no episodes of device mode changes, arrhythmias, therapies delivered, electrical reset, or battery depletion. One study was prematurely discontinued due to a patient complaint of chest pain of which the etiology was not determined. Across all examinations, the average peak SAR was 2.0 ± 0.85 W/kg with an average SAR of 0.35 ± 0.37 W/kg. Artifact significantly limiting the clinical interpretation of the study was present in 33% of cardiac MRI studies. CONCLUSIONS When a comprehensive CIED magnetic resonance safety protocol is followed, the risk of performing 1.5-T magnetic resonance studies with the device in the magnet isocenter, including in patients who are pacemaker dependent, is low.

Accelerated dual‐venc 4D flow MRI for neurovascular applications

To improve velocity‐to‐noise ratio (VNR) and dynamic velocity range of 4D flow magnetic resonance imaging (MRI) by using dual‐velocity encoding (dual‐venc) with k‐t generalized autocalibrating partially parallel acquisition (GRAPPA) acceleration.

Validation of highly accelerated real-time cardiac cine MRI with radial k-space sampling and compressed sensing in patients at 1.5T and 3T

To validate an optimal 12‐fold accelerated real‐time cine MRI pulse sequence with radial k‐space sampling and compressed sensing (CS) in patients at 1.5T and 3T.

A Papillary Fibroelastoma Involving Aortic and Pulmonary Valves: Findings on Multimodality Imaging

Cardiac papillary fibroelastoma, a rare entity, is the second most common benign primary cardiac tumor. Commonly involving the cardiac valves, this entity is increasingly diagnosed using different imaging modalities. We present a rare case of simultaneous involvement of both the aortic and pulmonary valves in an asymptomatic patient who underwent different imaging modalities, including transthoracic and transesophageal echocardiography, nongated and gated computed tomography, and magnetic resonance imaging. We will discuss the imaging findings and differential diagnosis.

4D flow MRI, cardiac function, and T1-mapping: Association of valve-mediated changes in aortic hemodynamics with left ventricular remodeling

Patients with bicuspid aortic valve (BAV) show altered hemodynamics in the ascending aorta that can be assessed by 4D flow MRI.

Wideband LGE MRI permits unobstructed viewing of myocardial scarring in a patient with an MR-conditional subcutaneous implantable cardioverter-defibrillator

A subcutaneous implantable cardioverter-defibrillator (S-ICD) is an alternative device for prevention of sudden cardiac death, without any leads within the heart. Patients implanted with any type of ICD may need catheter ablation of ventricular tachycardia (VT) to reduce the overall arrhythmia burden (e.g., recurrent monomorphic VT) and lower the incidence of painful shocks induced by the device. Late gadolinium enhancement (LGE) MRI is a useful pre-test for guiding VT ablation, because it can be used to map myocardial scar and produce better outcomes. Growing evidence suggests that MRI can be performed with manageable risks on patients with a cardiac implantable electronic device (CIED). Nonetheless, the diagnostic yield of cardiac MRI is still low because of severe image artifacts, regardless of MR-conditional or non-MR conditional labeling. Image artifacts in the heart induced by an S-ICD is expected to be larger than the artifacts induced by a transvenous ICD, because the former is twice as large in size and implanted closer to the heart. This is the first reported case of successful wideband LGE MRI in a patient implanted with an MR-conditional S-ICD. A 37-year-old man with ischemic cardiomyopathy was referred for a cardiac MRI at 1.5 T ten months after S-ICD implantation, in order to rule out constrictive pericarditis. Clinical standard LGE MRI produced severe image artifacts, rendering it useless. In contrast, wideband LGE MRI provided unobstructed viewing of myocardial scarring. This case illustrates the usefulness of wideband LGE MRI for assessment of myocardial scarring in a patient with an MR-conditional S-ICD.

Changes in the specific absorption rate (SAR) of radiofrequency energy in patients with retained cardiac leads during MRI at 1.5T and 3T

To evaluate the local specific absorption rate (SAR) and heating around retained cardiac leads during MRI at 64 MHz (1.5T) and 127 MHz (3T) as a function of RF coil type and imaging landmark.

Cardiac Structure-Function MRI in Patients After Heart Transplantation: Cardiac Structure-Function MRI

Following heart transplantation (Tx), recipients are closely monitored using endomyocardial biopsy, which is limited by cost and invasiveness, and echocardiography, which is limited regarding detailed structural and functional evaluation.

Motion-Corrected Real-Time Cine Magnetic Resonance Imaging of the Heart: Initial Clinical Experience

Objectives Free-breathing real-time (RT) imaging can be used in patients with difficulty in breath-holding; however, RT cine imaging typically experiences poor image quality compared with segmented cine imaging because of low resolution. Here, we validate a novel unsupervised motion-corrected (MOCO) reconstruction technique for free-breathing RT cardiac images, called MOCO-RT. Motion-corrected RT uses elastic image registration to generate a single heartbeat of high-quality data from a free-breathing RT acquisition. Materials and Methods Segmented balanced steady-state free precession (bSSFP) cine images and free-breathing RT images (Cartesian, TGRAPPA factor 4) were acquired with the same spatial/temporal resolution in 40 patients using clinical 1.5 T magnetic resonance scanners. The respiratory cycle was estimated using the reconstructed RT images, and nonrigid unsupervised motion correction was applied to eliminate breathing motion. Conventional segmented RT and MOCO-RT single-heartbeat cine images were analyzed to evaluate left ventricular (LV) function and volume measurements. Two radiologists scored images for overall image quality, artifact, noise, and wall motion abnormalities. Intraclass correlation coefficient was used to assess the reliability of MOCO-RT measurement. Results Intraclass correlation coefficient showed excellent reliability (intraclass correlation coefficient ≥ 0.95) of MOCO-RT with segmented cine in measuring LV function, mass, and volume. Comparison of the qualitative ratings indicated comparable image quality for MOCO-RT (4.80 ± 0.35) with segmented cine (4.45 ± 0.88, P = 0.215) and significantly higher than conventional RT techniques (3.51 ± 0.41, P < 0.001). Artifact and noise ratings for MOCO-RT (1.11 ± 0.26 and 1.08 ± 0.19) and segmented cine (1.51 ± 0.90, P = 0.088 and 1.23 ± 0.45, P = 0.182) were not different. Wall motion abnormality ratings were comparable among different techniques (P = 0.96). Conclusions The MOCO-RT technique can be used to process conventional free-breathing RT cine images and provides comparable quantitative assessment of LV function and volume measurements to conventional segmented cine imaging while providing improved image quality and less artifact and noise. The free-breathing MOCO-RT reconstruction method may have considerable clinical utility in cardiac magnetic resonance imaging for patients with difficulty breath-holding.

MR tissue phase mapping reveals reduced left ventricular velocities in patients with myocardial scar

Background Cardiac magnetic resonance (CMR) imaging is the reference standard for assessing biventricular systolic function. However, global measures of systolic function (i.e. ejection fraction) are relatively insensitive to regional alterations in myocardial structure, creating a need for quantitative analysis for regional myocardial function. Tissue phase mapping (TPM) is a CMR imaging technique that measures the regional myocardial velocities with high temporal resolution, complete left ventricular (LV) coverage, and full access to the 3-directional myocardial velocities. In this study, we evaluated the impact of myocardial scar detected with delayed enhancement imaging (DE-CMR) in patients with suspected infiltrative cardiomyopathy on global and regional myocardial velocities and dyssynchrony measured by TPM, comparing the results with controls.