Nonenhanced Magnetic Resonance Angiography of the Lower Extremity Vessels at 7 Tesla

Fischer, Anja; Maderwald, Stefan; Orzada, Stephan; Johst, Sören; Schäfer, Lena; Ladd, Mark E.; Naßenstein, Kai; Umutlu, Lale; Lauenstein, Thomas C.

doi:10.1097/rli.0b013e3182839c2b

Cited by 10 publications

(24 citation statements)

References 35 publications

(39 reference statements)

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“…TOF MRA revealed its diagnostic superiority due to high vessel-tobackground contrast compared to FLASH imaging [70]. The application of non-enhanced ultra-high-field MRA has recently also been successfully expanded to imaging of the vessels of the lower extremities [71] ( • " Fig. 8).…”

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confidence: 99%

7 Tesla MR Imaging: Opportunities and Challenges

Umutlu

Ladd

Forsting³

et al. 2013

Fortschr Röntgenstr

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The urge to increase magnetic field strength is driven by a number of potentially beneficial physical changes, possibly resulting in improved MR diagnostics. With the successful introduction of in-vivo ultra-high-field MR imaging, by means of 7 Tesla MRI, the focus of scientific research has been set on compiling different applications of brain and body imaging. This review presents an overview on the current status of 7?T MR imaging, investigating the opportunities as well as challenges associated with ultra-high-field MRI. Citation Format: ??Umutlu L, Ladd ME, Forsting M et?al. 7 Tesla MR?Imaging: Opportunities and Challenges. Fortschr R?ntgenstr 2014; 186: 121???129

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confidence: 99%

7 Tesla MR Imaging: Opportunities and Challenges

Umutlu

Ladd

Forsting³

et al. 2013

Fortschr Röntgenstr

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“…However, we observed that during increased HRV, an artifact associated with inaccurate triggering [12] appeared in the MRA images. This is interesting because the triggers were quantitatively more similar to PO than during another scan that contained no artifacts.…”

Section: Discussionmentioning

confidence: 99%

“…Experiments were performed on an ultra-high-field whole-body MRI system (MAGNETOM 7T; Siemens GmbH, Erlangen, Germany) using the MRA setup as described by Fischer et al [12] with a 16-channel transmit/receive body coil [34]. …”

Section: Methodsmentioning

confidence: 99%

“…The latter was performed according to our MRA protocol [12], and PO was used as the triggering method. The stages were performed in order (1) (2) (3) with duration of 5 min each.…”

Section: Methodsmentioning

confidence: 99%

“…Our main research interest lies in ultra-high-field non-enhanced angiography (MRA), which requires relatively long scanning times of approximately 60 min [12]. Unfortunately, patients often suffer from decreasing perfusion of the upper extremities with increasing scanning time, which often also results in degraded PO signal quality.…”

Section: Introductionmentioning

confidence: 99%

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Initial evaluation of prospective cardiac triggering using photoplethysmography signals recorded with a video camera compared to pulse oximetry and electrocardiography at 7T MRI

et al. 2016

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BackgroundAccurate synchronization between magnetic resonance imaging data acquisition and a subject’s cardiac activity (“triggering”) is essential for reducing image artifacts but conventional, contact-based methods for this task are limited by several factors, including preparation time, patient inconvenience, and susceptibility to signal degradation. The purpose of this work is to evaluate the performance of a new contact-free triggering method developed with the aim to eventually replace conventional methods in non-cardiac imaging applications. In this study, the method’s performance is evaluated in the context of 7 Tesla non-enhanced angiography of the lower extremities.MethodsOur main contribution is a basic algorithm capable of estimating in real-time the phase of the cardiac cycle from reflection photoplethysmography signals obtained from skin color variations of the forehead recorded with a video camera. Instead of finding the algorithm’s parameters heuristically, they were optimized using videos of the forehead as well as electrocardiography and pulse oximetry signals that were recorded from eight healthy volunteers in and outside the scanner, with and without active radio frequency and gradient coils. Based on the video characteristics, synthetic signals were generated and the “best available” values of an objective function were determined using mathematical optimization. The performance of the proposed method with optimized algorithm parameters was evaluated by applying it to the recorded videos and comparing the computed triggers to those of contact-based methods. Additionally, the method was evaluated by using its triggers for acquiring images from a healthy volunteer and comparing the result to images obtained using pulse oximetry triggering.ResultsDuring evaluation of the videos recorded inside the bore with active radio frequency and gradient coils, the pulse oximeter triggers were labeled in 62.5% as “potentially usable” for cardiac triggering, the electrocardiography triggers in 12.5%, and the proposed method’s triggers in 62.5%. Evaluation of the angiography images demonstrated that under appropriate conditions the method is feasible to produce an image quality comparable to pulse oximetry.ConclusionWe conclude that cardiac triggering using the proposed method is technically feasible. However, for improved reliability the signal-to-noise ratio of the videos will have to be addressed by either replacing the camera sensor, improving the illumination, or by use of additional signal filtering techniques.

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MRI at 7 tesla and above: Demonstrated and potential capabilities

Kraff

Fischer

Nagel

et al. 2014

Magnetic Resonance Imaging

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With more than 40 installed MR systems worldwide operating at 7 Tesla or higher, ultra-high-field (UHF) imaging has been established as a platform for clinically oriented research in recent years. Along with technical developments that, in part, have also been successfully transferred to lower field strengths, MR imaging and spectroscopy at UHF have demonstrated capabilities and potentials for clinical diagnostics in a variety of studies. In terms of applications, this overview article focuses on already achieved advantages for in vivo imaging, i.e., in imaging the brain and joints of the musculoskeletal system, but also considers developments in body imaging, which is particularly challenging. Furthermore, new applications for clinical diagnostics such as X-nuclei imaging and spectroscopy, which only really become feasible at ultra-high magnetic fields, will be presented.

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Nonenhanced Magnetic Resonance Angiography of the Lower Extremity Vessels at 7 Tesla

Cited by 10 publications

References 35 publications

7 Tesla MR Imaging: Opportunities and Challenges

7 Tesla MR Imaging: Opportunities and Challenges

Initial evaluation of prospective cardiac triggering using photoplethysmography signals recorded with a video camera compared to pulse oximetry and electrocardiography at 7T MRI

MRI at 7 tesla and above: Demonstrated and potential capabilities

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