Farshid Faraji

Vascular Imaging With Ferumoxytol as a Contrast Agent

OBJECTIVE Ferumoxytol is increasingly reported as an alternative to gadolinium-based contrast agents for MR angiography (MRA), particularly for patients with renal failure. This article summarizes more than 3 years of clinical experience with ferumoxytol-enhanced MRA for a range of indications and anatomic regions. CONCLUSION Ferumoxytol-enhanced MRA has many advantages including that it is safe for patients with renal failure and provides a lengthy plateau of vascular signal as a blood pool agent that allows longer navigated MRA sequences.

Isotropic 3D black blood MRI of abdominal aortic aneurysm wall and intraluminal thrombus

INTRODUCTION The aortic wall and intraluminal thrombus (ILT) have been increasingly studied as potential markers of progressive disease with abdominal aortic aneurysms (AAAs). Our goal was to develop a high resolution, 3D black blood MR technique for AAA wall and ILT imaging within a clinically acceptable scan time. METHODS Twenty two patients with AAAs (maximal diameter 4.3±1.0cm), along with five healthy volunteers, were imaged at 3T with a 3D T1-weighted fast-spin-echo sequence using variable flip angle trains (SPACE) with a preparation pulse (DANTE) for suppressing blood signal. Volunteers and ten patients were also scanned with SPACE alone for comparison purposes. The signal to noise ratio (SNR) and the aortic wall/ILT to lumen contrast to noise ratio (CNR) were measured. Qualitative image scores (1-4 scale) assessing the inner lumen and outer wall boundaries of AAA were performed by two blinded reviewers. In patients with ILT, the ratio of ILT signal intensity (ILTSI) over psoas muscle SI (MuscleSI) was calculated, and the signal heterogeneity of ILT was quantified as standard deviation (SD) over the mean. RESULTS All subjects were imaged successfully with an average scan time of 7.8±0.7minutes. The DANTE preparation pulse for blood suppression substantially reduced flow artifacts in SPACE with lower lumen SNR (8.8 vs. 21.4, p<0.001) and improved the wall/ILT to lumen CNR (9.9 vs. 6.3, p<0.001) in patients. Qualitative assessment showed improved visualization of lumen boundaries (73% higher scores on average, p=0.01) and comparable visualization of outer wall boundary (p>0.05). ILT was present in ten patients, with relatively high signal and a wide SD (average ILTSI/MuscleSI 1.42±0.48 (range 0.75-2.11)) and with SD/mean of 27.7%±6.6% (range 19.6%-39.4%). CONCLUSION High resolution, 3D black blood MRI of AAAs can be achieved in a clinical accepted scan time with reduction of flow artifacts using the DANTE preparation pulse. Signal characteristics of ILT can be quantified and may be used for improved patient-specific risk stratification.

Segmentation of lumen and outer wall of abdominal aortic aneurysms from 3D black-blood MRI with a registration based geodesic active contour model

HighlightsMR image segmentation is performed on abdominal aortic aneurysm lumen and outer wall.Novel segmentation is proposed using image registration and shape terms in the model.The repeatability and reproducibility of the proposed method are validated. &NA; Segmentation of the geometric morphology of abdominal aortic aneurysm is important for interventional planning. However, the segmentation of both the lumen and the outer wall of aneurysm in magnetic resonance (MR) image remains challenging. This study proposes a registration based segmentation methodology for efficiently segmenting MR images of abdominal aortic aneurysms. The proposed methodology first registers the contrast enhanced MR angiography (CE‐MRA) and black‐blood MR images, and then uses the Hough transform and geometric active contours to extract the vessel lumen by delineating the inner vessel wall directly from the CE‐MRA. The proposed registration based geometric active contour is applied to black‐blood MR images to generate the outer wall contour. The inner and outer vessel wall are then fused presenting the complete vessel lumen and wall segmentation. The results obtained from 19 cases showed that the proposed registration based geometric active contour model was efficient and comparable to manual segmentation and provided a high segmentation accuracy with an average Dice value reaching 89.79%.

The manifestation of vortical and secondary flow in the cerebral venous outflow tract: An in vivo MR velocimetry study

Aberrations in flow in the cerebral venous outflow tract (CVOT) have been implicated as the cause of several pathologic conditions including idiopathic intracranial hypertension (IIH), multiple sclerosis (MS), and pulsatile tinnitus (PT). The advent of 4D flow magnetic resonance imaging (4D-flow MRI) has recently allowed researchers to evaluate blood flow patterns in the arterial structures with great success. We utilized similar imaging techniques and found several distinct flow characteristics in the CVOT of subjects with and without lumenal irregularities. We present the flow patterns of 8 out of 38 subjects who have varying heights of the internal jugular bulb and varying lumenal irregularities including stenosis and diverticulum. In the internal jugular vein (IJV) with an elevated jugular bulb (JB), 4Dflow MRI revealed a characteristic spiral flow that was dependent on the level of JB elevation. Vortical flow was also observed in the diverticula of the venous sinuses and IJV. The diversity of flow complexity in the CVOT illustrates the potential importance of hemodynamic investigations in elucidating venous pathologies.

Flow patterns in the jugular veins of pulsatile tinnitus patients.

Pulsatile Tinnitus (PT) is a pulse-synchronous sound heard in the absence of an external source. PT is often related to abnormal flow in vascular structures near the cochlea. One vascular territory implicated in PT is the internal jugular vein (IJV). Using computational fluid dynamics (CFD) based on patient-specific Magnetic Resonance Imaging (MRI), we investigated the flow within the IJV of seven subjects, four symptomatic and three asymptomatic of PT. We found that there were two extreme anatomic types classified by the shape and position of the jugular bulbs: elevated and rounded. PT patients had elevated jugular bulbs that led to a distinctive helical flow pattern within the proximal internal jugular vein. Asymptomatic subjects generally had rounded jugular bulbs that neatly redirected flow from the sigmoid sinus directly into the jugular vein. These two flow patterns were quantified by calculating the length-averaged streamline curvature of the flow within the proximal jugular vein: 130.3±8.1m-1 for geometries with rounded bulbs, 260.7±29.4m-1 for those with elevated bulbs (P<0.005). Our results suggest that variations in the jugular bulb geometry lead to distinct flow patterns that are linked to PT, but further investigation is needed to determine if the vortex pattern is causal to sound generation.

P-029 Turbulent Flow in the Venous Outflow Tract of Pulsatile Tinnitus Patients with Sigmoid Sinus Diverticulum

Introduction/purpose Pulsatile tinnitus (PT) has been linked to multiple anatomical variants of the venous outflow tract including sigmoid sinus diverticulum (SSD). We hypothesize that turbulence generated by the SSD, which is normally preceded by a transverse sinus stenosis (TSS), can explain the source of sound. Turbulent flow has a known association to vasculogenic bruit. Advanced magnetic resonance velocimetry (MRV) was performed in cerebral venous sinuses and internal jugular veins (IJV) to obtain both volumetric velocity and turbulence maps. Materials and methods A series of MRI protocols was performed at 3 T for patients with suspected venous PT including contrast-enhanced MRA (CE-MRA) to delineate the anatomy and identify SSD, 4 D-flow MR to acquire time-resolved phase (velocity) and flow-encoded magnitudes in all three directions, as well as 2 D flow to obtain flow waveforms. Flow turbulence was quantified based on turbulence kinetic energy (TKE). Five SSD patients were evaluated, four of which had an associated TSS upstream from the SSD. Results The TSS resulted in a jet of flow, the direction of which seemed to determine the position of the SSD downstream. The streamline visualization of the flow patterns revealed recirculation in the diverticulum. A helical flow pattern was also found adjacent to the jet flow opposite and downstream of the SSD (Figure 1). TKE mapping revealed a highly localized region of elevated TKE downstream from the stenosis extending to the opening of the diverticulum with a maximum value of 80 J/m3 (Figure 2).Abstract P-029 Figure 1 A tilted anterior-posterior projection of the venous sinuses and IJV in a PT patient with the SSD and upstream TSS.MRV-based streamlines colored by the magnitude of the velocity are overlaid on to the geometry captured by CE-MRA (black)Abstract P-029 Figure 2 MRV-based measurement of the TKE in the same PT patient as shown in Figure 1. The elevated TKE region is highly localized to the downstream of the stenosis and extends into the opening of the diverticulum Discussion and Conclusion The unique flow patterns and the presence of turbulence introduced by the TSS and SSD may help explain PT in these patients. Treatment of TSS with PTA and stent implantation, or treatment of the SSD with coil embolization can potentially alter the TKE level and pattern. Disclosures S. Kefayati: None. E. Kao: None. J. Liu: None. H. Haraldsson: None. F. Faraji: None. M. Ballweber: None. K. Meisel: None. V. Halbach: None. D. Saloner: None. M. Amans: None.

Short term doxycycline treatment induces sustained improvement in myocardial infarction border zone contractility

Decreased contractility in the non-ischemic border zone surrounding a MI is in part due to degradation of cardiomyocyte sarcomeric components by intracellular matrix metalloproteinase-2 (MMP-2). We recently reported that MMP-2 levels were increased in the border zone after a MI and that treatment with doxycycline for two weeks after MI was associated with normalization of MMP-2 levels and improvement in ex-vivo contractile protein developed force in the myocardial border zone. The purpose of the current study was to determine if there is a sustained effect of short term treatment with doxycycline (Dox) on border zone function in a large animal model of antero-apical myocardial infarction (MI). Antero-apical MI was created in 14 sheep. Seven sheep received doxycycline 0.8 mg/kg/hr IV for two weeks. Cardiac MRI was performed two weeks before, and then two and six weeks after MI. Two sheep died prior to MRI at six weeks from surgical/anesthesia-related causes. The remaining 12 sheep completed the protocol. Doxycycline induced a sustained reduction in intracellular MMP-2 by Western blot (3649±643 MI+Dox vs 9236±114 MI relative intensity; p = 0.0009), an improvement in ex-vivo contractility (65.3±2.0 MI+Dox vs 39.7±0.8 MI mN/mm2; p<0.0001) and an increase in ventricular wall thickness at end-systole 1.0 cm from the infarct edge (12.4±0.6 MI+Dox vs 10.0±0.5 MI mm; p = 0.0095). Administration of doxycycline for a limited two week period is associated with a sustained improvement in ex-vivo contractility and an increase in wall thickness at end-systole in the border zone six weeks after MI. These findings were associated with a reduction in intracellular MMP-2 activity.

O-032 Venous Blood Flow Visualization in Sigmoid Sinus Diverticulum Using MRI

Introduction/purpose Sigmoid sinus diverticulum (SSD) is one of the potentially treatable causes of pulsatile tinnitus (PT). How SSD causes PT is unknown, but it is thought to be secondary to aberrant blood flow in the diverticulum or parent sinus. We performed velocity field mapping using MR 4 D Flow (MRV) and computational fluid dynamics (CFD) in cerebral venous sinuses and internal jugular veins (IJV). We aim to determine if a distinct blood flow pattern may be responsible for PT in SSD. Materials and methods Patients suspected of venous etiology of PT underwent MRI at 3 T, using contrast-enhanced MRA (timed to venous phase), MRV and CFD. SSD was confirmed on MRA. Flow pathlines were evaluated. In patients with confirmed SSD, additional CFD modelling was performed with the SSD excluded from the models. Results Nineteen patients with suspected venous etiology of PT and 10 controls were evaluated. Six (31.5%) had SSD and five of these had transverse sinus stenosis upstream from the SSD. These five patients also demonstrated a unique pattern of flow not seen in the controls characterized by: 1. High velocity flow jet in an up-stream stenosis in the transverse sinus directed at the SSD opening, 2. Flow jet into the SSD along the long axis of the SSD, either anteriorly or laterally directed, 3. Vortex of flow in the SSD, 4. Prominent vortex component of flow in the sigmoid sinus downstream from SSD, 5. Vortex of flow in the jugular bulb Three of the patients had simulated post-coil treatment models developed excluding the SSD from the models. CFD showed no flow in SSD and decreased vortex component of flow in the sigmoid sinus downstream from the SSD. Conclusion PT caused by SSD may be caused by a unique flow pattern in the SSD and sinuses as visualized on both MRV and CFD.Abstract O-032 Figure 1 Townes projection CFD analysis of a patient with a left SSD and an upstream stenosis in the transverse sinus. The pretreatment analysis (A) shows a jet of flow from the stenosis into the SSD (arrow), vortex of flow in the SSD (double arrow), and a vortex component of flow in the sigmoid sinus down-stream from the SSD (arrow head). The post-treatment model (B) shows absence of the flow in the SSD as well as decreased vortex component of flow in down-stream sigmoid sinus Disclosures M. Amans: None. E. Kao: None. S. Kefayati: None. K. Meisel: None. F. Faraji: None. C. Glastonbury: None. M. Ballweber: None. V. Halbach: None. D. Saloner: None.

O-033 Jugular Vein Flow Patterns in Patients with Pulsatile Tinnitus Using Computational Fluid Dynamics

Introduction/purpose Aberrations of venous anatomy can cause pulsatile tinnitus (PT). However, venous anatomy variation in patients without pulsatile tinnitus (PT) is extremely variable. Conventional imaging modalities, including cerebral angiography, provide little insight into the complex flow patterns in the cerebral veins. The aim of this study was to use subject-specific contrast-enhanced MRA (CE-MRA) determined anatomy, and MRV-based inlet flow conditions to develop computational fluid dynamics (CFD) models of flow in subjects with suspected venous pulsatile tinnitus and subjects without pulsatile tinnitus to investigate how the geometry of the jugular vein affects flow. Materials and methods 7 jugular veins (4 normal, 3 with pulsatile tinnitus) were imaged with CE-MRA. 2 D phase contrast MRV was also acquired transverse to the sigmoid sinus to determine inlet flow conditions. Surfaces were segmented using VMTK (Orobix, Bergamo, Italy) and Geomagic Design X (Geomagic, Rock Hill, USA). Tetrahedral meshing was also performed in VMTK, using a target edge-length of 0.6 mm. CFD simulations were performed in FLUENT (ANSYS, Canonsburg, USA), using flow values obtained from the literature and in vivo measurements.Flow patterns in the jugular vein were characterized by their vortex core-lines, which were extracted from simulation data using Ensight (CEI, Apex, USA). Additional flow-parameters were calculated in MATLAB (Mathworks, Natick, USA) and pathlines visualized using Paraview (Kitware, New York, USA). Results Patients with suspected venous PT had flow distinct patterns from those in normal subjects. Non-PT flow was characterized by organized redirection of flow from the sigmoid sinus along the curvature of the bulb into the jugular vein (A) with vortex cores in the jugular bulb (C). PT flow was characterized by larger helical flow structures throughout the proximal jugular vein created by flow directed perpendicular to the sigmoid sinus flow (B) and vortex cores that were more diffusely organized (D). High flow rates, and even turbulence, were noted in the proximal jugular vein – near the level of the carotid bifurcation – where there was often pronounced narrowing of the jugular. Conclusion The geometry of the jugular vein significantly affects the position, size, and length of the vortex cores. Our results suggest a link between geometry, flow, and PT.Abstract O-033 Figure 1 Visualization of streamlines (A, B) and vortex cores by swirling strength (C, D) in internal jugular veins of subjects without (A, C) and with (B, D) PT. White arrows (A, B) reperent the general re-direction of flow from the sigmoid sinus into the jagular vein as dictated by the shape of the junction with the jugular bulb (red lines). Subjects without PT have strong vortex cores in jugular bulb (C, red arrows), while those with PT have larger, more diffuse vortex cores (D) that encompass nearly the entire proximal jugular vein (blue arrow). Disclosures E. Kao: None. S. Kefayati: None. K. Meisel: None. M. Ballweber: None. F. Faraji: None. V. Halbach: None. D. Saloner: None. M. Amans: None.