Sarah N Khan

Device artifact reduction for magnetic resonance imaging of patients with implantable cardioverter-defibrillators and ventricular tachycardia: late gadolinium enhancement correlation with electroanatomic mapping.

BACKGROUND Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) of ventricular scar has been shown to be accurate for detection and characterization of arrhythmia substrates. However, the majority of patients referred for ventricular tachycardia (VT) ablation have an implantable cardioverter-defibrillator (ICD), which obscures image integrity and the clinical utility of MRI. OBJECTIVE The purpose of this study was to develop and validate a wideband LGE MRI technique for device artifact removal. METHODS A novel wideband LGE MRI technique was developed to allow for improved scar evaluation on patients with ICDs. The wideband technique and the standard LGE MRI were tested on 18 patients with ICDs. VT ablation was performed in 13 of 18 patients with either endocardial and/or epicardial approach and the correlation between the scar identified on MRI and electroanatomic mapping (EAM) was analyzed. RESULTS Hyperintensity artifact was present in 16 of 18 of patients using standard MRI, which was eliminated using the wideband LGE and allowed for MRI interpretation in 15 of 16 patients. All patients had ICD lead characteristics confirmed as unchanged post-MRI and had no adverse events. LGE scar was seen in 11 of 18 patients. Among the 15 patients in whom wideband LGE allowed visualization of myocardium, 10 had LGE scar and 5 had normal myocardium in the regions with image artifacts when using the standard LGE. The left ventricular scar size measurements using wideband MRI and EAM were correlated with R(2) = 0.83 and P = .00003. CONCLUSION Wideband LGE MRI improves the ability to visualize myocardium for clinical interpretation, which correlated well with EAM findings during VT ablation.

Orbital masses: CT and MRI of common vascular lesions, benign tumors, and malignancies

A wide variety of space occupying lesions may be encountered in the orbit. CT and MR imaging frequently help confirm the presence of a mass and define its extent. Characteristic imaging features may help distinguish among lesions that have overlapping clinical presentations. This review focuses on some of the common orbital masses. Common vascular lesions that are reviewed include: capillary (infantile) hemangioma, cavernous hemangioma (solitary encapsulated venous-lymphatic malformation), and lymphangioma (venous-lymphatic malformation). Benign tumors that are reviewed include: optic nerve sheath meningioma, schwannoma, and neurofibroma. Malignancies that are reviewed include: lymphoma, metastasis, rhabdomyosarcoma, and optic glioma. Key imaging features that guide radiological diagnosis are discussed and illustrated.

Four-dimensional, multiphase, steady-state imaging with contrast enhancement (MUSIC) in the heart: a feasibility study in children.

To develop a technique for high resolution, four‐dimensional (4D), multiphase, steady‐state imaging with contrast enhancement (MUSIC) in children with complex congenital heart disease.

Pediatric cardiovascular interventional devices: effect on CMR images at 1.5 and 3 Tesla

BackgroundTo predict the type and extent of CMR artifacts caused by commonly used pediatric trans-catheter devices at 1.5 T and 3 T as an aid to clinical planning and patient screening.MethodsEleven commonly used interventional, catheter-based devices including stents, septal occluders, vascular plugs and embolization coils made from either stainless steel or nitinol were evaluated ex-vivo at both 1.5T and 3T. Pulse sequences and protocols commonly used for cardiovascular magnetic resonance (CMR) were evaluated, including 3D high-resolution MR angiography (MRA), time-resolved MRA, 2D balanced-SSFP cine and 2D phase-contrast gradient echo imaging (GRE). We defined the signal void amplification factor (F) as the ratio of signal void dimension to true device dimension. F1 and F2 were measured in the long axis and short axes respectively of the device. We defined F3 as the maximum extent of the off-resonance dark band artifact on SSFP measured in the B0direction. The effects of field strength, sequence type, orientation, flip angle and phase encode direction were tested. Clinical CMR images in 3 patients with various indwelling devices were reviewed for correlation with the in-vitro findings.ResultsF1 and F2 were higher (p<0.05) at 3T than at 1.5T for all sequences except 3D-MRA. Stainless steel devices produced greater off-resonance artifact on SSFP compared to nitinol devices (p<0.05). Artifacts were most severe with the stainless steel Flipper detachable embolization coil (Cook Medical, Bloomington, IN), with F1 and F2 10 times greater than with stainless steel stents. The orientation of stents changed the size of off-resonance artifacts by up to two fold. Sequence type did influence the size of signal void or off-resonance artifact (p<0.05). Varying the flip angle and phase encode direction did not affect image artifact.ConclusionStainless steel embolization coils render large zones of anatomy uninterpretable, consistent with predictions based on ex-vivo testing. Most other commonly used devices produce only mild artifact ex-vivo and are compatible with diagnostic quality in-vivo studies. Knowledge of ex-vivo device behavior can help predict the technical success or failure of CMR scans and may preempt the performance of costly, futile studies.

Three-phase parathyroid 4-dimensional computed tomography initial experience: inexperienced readers have high accuracy and high interobserver agreement.

Objective Multiphase multidetector contrast-enhanced parathyroid CT (4-dimensional computed tomography [4D-CT]) is an emerging tool for evaluating patients with primary hyperparathyroidism. Our goal was to describe the initial performance of 2 inexperienced readers in interpretation of 4D-CT. Methods Twenty-three subjects who received 4D-CT and successful surgical exploration were studied (14 initial and 9 repeat explorations; 15 single-gland disease and 8 multigland disease) A staff neuroradiologist prospectively interpreted all studies, and a neuroradiology fellow retrospectively interpreted all studies; their results were compared with the surgical findings for each side of the neck separately. Results The prospective readings were 78% accurate overall, 97% accurate in the subset of single-gland disease cases, and 89% accurate in re-exploration cases. There was 91% concordance in interpretation between observers, with &kgr; of 0.83. Conclusions Initial results after implementation of 4D-CT show high accuracy of interpretation for inexperienced observers, comparable to published data, and high interobserver agreement.

Contrast-enhanced MR angiography of cavopulmonary connections in adult patients with congenital heart disease

OBJECTIVE The purpose of this study is to evaluate combined time-resolved and high-spatial resolution contrast-enhanced MR angiography (MRA) for assessment of cavopulmonary connections in adult patients with congenital heart disease. MATERIALS AND METHODS Twenty-eight adults with various surgical cavopulmonary connections (Glenn shunt and Fontan connection) underwent high-spatial-resolution contrast-enhanced MRA (voxel size, 1.95 mm(3); temporal resolution, 22 seconds) and time-resolved contrast-enhanced MRA (voxel size, 6.5-9.3 mm(3); temporal resolution, < 1.2 seconds). Ten patients had 2D phase contrast flow quantification measurements performed at the same setting. Two readers independently assessed anatomic dimensions of cavopulmonary connections (using high-spatial-resolution contrast-enhanced MRA) and pulmonary artery (PA) perfusion patterns (using time-resolved contrast-enhanced MRA). RESULTS High-spatial-resolution contrast-enhanced MRA yielded diagnostic-quality images for morphologic assessment of cavopulmonary connections in 27 of 28 (96%) patients. The anatomic dimensions (cross-sectional area) of the PA and cavopulmonary connections showed a wide variation (right PA, 0.99-5.67 cm(2); left PA, 0.80-5.69 cm(2); Glenn shunt, 0.93-6.94 cm(2); and Fontan connection, 1.25-6.67 cm(2)). The anatomic dimensions could be assessed with excellent interobserver agreement on high-spatial-resolution contrast-enhanced MRA (r = 0.895). Time-resolved contrast-enhanced MRA yielded diagnostic-quality images in all patients and enabled characterization of PA perfusion via the superior vena cava as follows: preferential inflow to the right PA (n = 12), preferential inflow to the left PA (n = 5), and balanced inflow to the right and left PA (n = 11). In those patients who had technically successful flow quantification measurements, phase contrast data confirmed patency of the cavopulmonary connections. CONCLUSION Combined time-resolved contrast-enhanced MRA and high-spatial-resolution contrast-enhanced MRA allowed detailed morphologic and dynamic evaluation of cavopulmonary connections in adult patients with congenital heart disease. A wide variation in anatomic dimensions and perfusion patterns was confidently identified in this patient population.

Myocardial tagging in the polar coordinate system; early clinical experience

Background Quantitative MR myocardial strain analysis is typically performed using rectilinear or Cartesian grid tagging, and regional contractility is visually assessed by the deformation of the grid1. However, it is difficult to visually isolate circumferential and radial components of displacement and strain from parallel straight lines on short axis images. This study evaluates the potential of a polar coordinate tagging system2 for quantification of circumferential myocardial displacement in a variety of clinical conditions.

Regional rotation of the left ventricle in healthy and cardiomyopathic subjects measured with radial myocardial tagging

Background Left ventricular rotational deformation, which arises from contraction of myofibers arranged in a helical structure, plays a crucial role in cardiac mechanics. Myocardial dysfunction in cardiomyopathies is usually associated with altered diastolic rotation [1-3]. However, regional myocardial abnormalities in various cardiomyopathies may result in regional alterations of both systolic and diastolic rotational motion. The regional variation of LV rotation in healthy subjects has been previously studied [4-7]. We hypothesize that LV regional rotation abnormalities may be a sensitive marker in heart diseases where myocardial structure is disordered. In this regard, we investigate the regional rotation pattern of the mid LV wall in both healthy subjects and patients with cardiomyopathies. In this study, LV regional rotation is assessed through dense radial tagging [8], which facilitates analysis of the rotational motion and provides detailed regional measurement by increasing the achievable circumferential resolution. Methods LV tagging in a dense radial pattern was performed at the mid LV short axis level in twelve healthy subjects and nine cardiomyopathic patients at 1.5T or 3.0T. Number of radial taglines was set to 22 per circle. Corresponding short axis cine images were available in all subjects. The mid LV short axis was divided into 6 circumferential segments according to the AHA 17-segment model. To compute rotation of each specific segment, the tag points located on the segment were automatically detected and traced through successive frames. Finally, the rotation of each LV sector was estimated using the spatial coordinate of the tag points plus that of the LV center of mass. Results The resulting mid ventricular rotation values and rotation rates in myopathic patients were decreased relative to healthy subjects in most circumferential segments (table 1 & Figure 1). Moreover, as is shown in Figure 1, the homogeneity of regional rotations at the mid level is more pronounced in healthy subjects compared with cardiomyopathic patients. Conclusions Initial results with high density radial tagging suggest a heterogeneous and diminished pattern of regional rotation in patients with cardiomyopathy. This may potentially reflect an imbalance in LV mechanical function and lead to decreased global rotation. Regional heterogeneity of rotation may merit further study as a myocardial functional marker. The simple and rapid calculation of regional

CMR in pediatric patients with congenital heart disease: comparison at 1.5T and at 3.0T

Author(s): Nguyen, Kim-Lien; Khan, Sarah; Moriarty, John; Mohajer, Kiyarash; Renella, Pierangelo; Satou, Gary; Ayad, Ihab; Patel, Swati; Boechat, Ines; Finn, J

Portal Venous Interventions: How to Recognize, Avoid, or Get Out of Trouble in Transjugular Intrahepatic Portosystemic Shunt (TIPS), Balloon Occlusion Sclerosis (ie, BRTO), and Portal Vein Embolization (PVE)

Portal venous interventions comprise a large portion of many Interventional Radiology practices today, and remain some of the more technically challenging cases in ones repertoire of procedures. The patients upon whom these procedures are performed are often critically ill, have decompensated disease, or are burdened with comorbid conditions such that they are poor surgical candidates. This leaves them with few options outside the care of Interventional Radiology. Some portal venous interventions, such as transjugular intrahepatic portosystemic shunt, have an established history of excellent clinical success with numerous technical advancements over the years helping to improve outcomes. Others, like balloon occlusion sclerotherapy or portal venous recanalization, are less well established but are nonetheless invaluable in the treatment of portal venous diseases. The goal of this article is to help dispel some of the anxiety experienced by individuals performing the three main procedures of the portal venous system, namely transjugular intrahepatic portosystemic shunt, balloon-occlusion retrograde transvenous obliteration, and portal vein embolization.