Optimization of realtime adaptive navigator correction for 3D magnetic resonance coronary angiography

Nagel, Eike; Bornstedt, Axel; Schnackenburg, Bernhard; Hug, Jürgen; Oswald, H. R.; Fleck, Eckart

doi:10.1002/(sici)1522-2594(199908)42:2<408::aid-mrm24>3.0.co;2-u

Cited by 71 publications

(43 citation statements)

References 15 publications

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“…For each direction of motion, correction factors were determined as the slope of the displacements measured in: 1) the free-breathing datasets; 2) the multiple breath-hold data-sets; and 3) the multiple LED-guided breath-hold data-sets, which covered a reduced respiratory range. In addition, the data-sets for small inspiratory and expiratory breath-holds were also used to calculate the correction factors by a simple twopoint technique (7,8). For each direction of motion, a nonparametric analysis of variance (ANOVA) was used to determine if there were significant differences between the correction factors measured by each of the four techniques.…”

Section: Methodsmentioning

confidence: 99%

“…This may be due to a failure of the linear model, or to inaccuracies in the motion correction factors, the effects of which would become greater as the range of motion requiring correction increases. It is clear from the large standard deviation of the SI correction factors measured in the original study (4) that there is considerable variability between subjects, and this has led other groups to implement subject-specific values (7,8). However, such implementations have still assumed that AP motion is relatively small and fixed, and that there is no left-right (LR) motion.…”

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confidence: 99%

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Coronary artery motion with the respiratory cycle during breath‐holding and free‐breathing: Implications for slice‐followed coronary artery imaging

Keegan¹,

Gatehouse²,

Yang

et al. 2002

Magnetic Resonance in Med

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The displacement of the right coronary artery (RCA) origin with respiratory position was determined relative to the dome of the right hemidiaphragm in three orthogonal directions in eight healthy subjects. Both multiple breath-hold and free-breathing acquisitions were used, and motion correction factors for slicefollowing applications were determined. The correction factors for all three directions showed considerable intersubject variability. The mean superior-inferior factor was slightly less in free-breathing than in breath-holding (0.26 vs. 0.29, P ‫؍‬ ns), and much less than the fixed value of 0.6 frequently implemented with slice-following. The anterior-posterior correction factors were uniformly low in free-breathing, and significantly less than those obtained from breath-holding (0.04 vs. 0.14, P < .05), while the mean left-right correction factors were approximately 0.1 for both. It is concluded that subject variability in correction factors, together with within-subject differences between breath-holding and free-breathing, is such that slice-following should be performed with subject-specific factors determined from free-breathing acquisitions. Key words: respiratory motion; slice-following; coronary artery; breath-holding; free-breathing Navigator-echo controlled free-breathing coronary artery studies (1) typically use a navigator positioned through the dome of the right hemidiaphragm, and an acceptance window of 5 mm to give a reasonable compromise between scan efficiency and image quality. However, during prolonged studies drifting of the respiratory pattern leads to a corresponding fall in efficiency (2), resulting in registration errors between scans and a frequent need to reposition the acceptance window. Real-time slice-following (3) has the potential to increase the scan efficiency and reduce the sensitivity to respiratory drift by allowing the implementation of a larger navigator acceptance window.The efficacy of real-time slice-following is critically dependent on the accuracy with which the motion of the heart can be predicted from the navigator echo data. In 1995, Wang and colleagues (4) used multiple 2D breathhold acquisitions to show a linear relationship between the superior-inferior (SI) motion of the heart and that of the diaphragm in healthy volunteers. In this subject group, the mean correction factor relating the SI motion of the right coronary artery (RCA) origin to that of the diaphragm was 0.57 (Ϯ0.26), and the anterior-posterior (AP) motion was approximately 20% of that in the SI direction (or 12% of that of the diaphragm). Some implementations of slicefollowing consequently use a fixed SI correction factor of 0.6, with or without a fixed AP factor of 0.12 (5,6). This approach has been shown to improve the quality of images acquired with 5-mm and 7-mm navigator acceptance windows, but has failed to produce good quality images when the acceptance window is increased to cover the entire range of respiratory positions (3). This may be due to a failure of the linear model, or to in...

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Coronary artery motion with the respiratory cycle during breath‐holding and free‐breathing: Implications for slice‐followed coronary artery imaging

Keegan¹,

Gatehouse²,

Yang

et al. 2002

Magnetic Resonance in Med

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“…This correction was performed by shifting the craniocaudal imaging position by 30% of the actual diaphragmatic offset. 4 …”

Section: Image Acquisitionmentioning

confidence: 99%

Noninvasive Determination of Coronary Blood Flow Velocity With Cardiovascular Magnetic Resonance in Patients After Stent Deployment

et al. 2003

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Background-In patients with coronary artery stents, no direct noninvasive coronary artery imaging is possible with magnetic resonance (MR). A well-established method for the assessment of the functional significance of a coronary lesion is the measurement of coronary flow reserve by invasive intracoronary Doppler. The purpose of the study was to determine coronary flow velocity reserve (CFVR) with MR after stent deployment. Methods and Results-Thirty-eight patients after successful PTCA and stent deployment were included. CFVR was measured perpendicular to the artery distal to the stent using phase-contrast velocity quantification at rest and during adenosine-stimulated hyperemia with a 1.5T MR tomograph (ACS NT, Philips). Measurements were repeated after 3 months and compared with invasive coronary angiography. In 18 patients, additional invasive Doppler flow measurements were obtained. CFVR could be determined in 29 of 38 (76%) of the patients. After 3 months, significant differences were obtained between coronary arteries with and without restenosis. Using a threshold of 1.2, a sensitivity of 83% with a specificity of 94% was achieved for Ն75% stenoses. CFVR with CMR was similar to Doppler results (rϭ0.87), with a mean relative difference of 7.5%. Conclusions-In patients with preserved coronary microcirculating vasoreactivity that are suitable for MR coronary angiography and flow assessments, CMR measures of coronary blood flow velocities reserve may be used to detect in-stent restenosis.

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“…In addition, the acquisition of 3D-MR images was shown to be largely operator independent and quite reproducible and may serve as an alternative in interventional MRI application for the assessment of cardiovascular structures. 18,36 …”

Section: Discussionmentioning

confidence: 59%

Magnetic Resonance Imaging–Guided Balloon Angioplasty of Coarctation of the Aorta

et al. 2006

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Background-MRI guidance of percutaneous transluminal balloon angioplasty (PTA) of aortic coarctation (CoA) would be desirable for continuous visualization of anatomy and to eliminate x-ray exposure. The aim of this study was (1) to determine the suitability of MRI-controlled PTA using the iron oxide-based contrast medium Resovist (ferucarbotran) for catheter visualization and (2) to subsequently apply this technique in a pilot study with patients with CoA. Methods and Results-The MRI contrast-to-noise ratio and artifact behavior of Resovist-treated balloon catheters was optimized in in vitro and animal experiments (pigs). In 5 patients, anatomy of the CoA was evaluated before and after intervention with high-resolution respiratory-navigated 3D MRI and multiphase cine MRI. Position monitoring of Resovist-treated catheters was realized with interactive real-time MRI. Aortic pressures were continuously recorded.Conventional catheterization was performed before and after MRI to confirm interventional success. During MRI, catheters filled with 25 mol of iron particles per milliliter of Resovist produced good signal contrast between catheters and their background anatomy but no image distortion due to susceptibility artifacts. All MRI procedures were performed successfully in the patient study. There was excellent agreement between the diameters of CoA and pressure gradients as measured during MRI and conventional catheterization. In 4 patients, PTA resulted in substantial widening of the CoA and a decrease in pressure gradients. In 1 patient, PTA was ineffective. Conclusions-The MRI method described represents a potential alternative to conventional x-ray fluoroscopy for catheter-based treatment of patients with CoA. (Circulation. 2006;113:1093-1100.)

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Optimization of realtime adaptive navigator correction for 3D magnetic resonance coronary angiography

Cited by 71 publications

References 15 publications

Coronary artery motion with the respiratory cycle during breath‐holding and free‐breathing: Implications for slice‐followed coronary artery imaging

Coronary artery motion with the respiratory cycle during breath‐holding and free‐breathing: Implications for slice‐followed coronary artery imaging

Noninvasive Determination of Coronary Blood Flow Velocity With Cardiovascular Magnetic Resonance in Patients After Stent Deployment

Magnetic Resonance Imaging–Guided Balloon Angioplasty of Coarctation of the Aorta

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