2-channel Coil Research Articles

Streaming in Transposition of the Great Arteries by Using Cardiac Magnetic Resonance Imaging

A 6-month-old child with progressive cyanosis was referred to our service for assessment. Transthoracic echocardiography confirmed the diagnosis of transposition of the great arteries, a very large ventricular septal defect (VSD), and subpulmonary stenosis. The atrial septum was intact. The transcutaneous oxygen saturation levels measured 40% to 50% in room air with a hemoglobin value of 19 g/dL. Conventional treatment with an arterial switch and VSD closure was not possible, because it would result in neoaortic obstruction because of the significant subpulmonary stenosis. Additionally, the size of the VSD was such that achieving adequate septation of the ventricles remained questionable. To aid surgical planning, a cardiac magnetic resonance scan was performed to determine whether the low transcutaneous oxygen saturation levels were due to poor mixing of blood or limited pulmonary blood flow. The scan was performed on a commercial 1.5T scanner (Achieva; Philips Healthcare, Best, The Netherlands) with a 2-channel coil. The child was awake and self-ventilating with the use of a wrap-and-feed strategy. A validated highly undersampled 4D phase-contrast flow (4D flow) sequence1 was used to …

Experimental differentiation of intraocular masses using ultrahigh-field magnetic resonance imaging--a case series.

PurposeThe case reports presented here were compiled to demonstrate the potential for improved diagnosis and monitoring of disease progress of intraocular lesions using ultrahigh-field magnetic resonance microscopy (MRM) at 7.1 Tesla.MethodsHigh-resolution ex vivo ocular magnetic resonance (MR) images were acquired on an ultrahigh-field MR system (7.1 Tesla, ClinScan, Bruker BioScan, Germany) using a 2-channel coil with 4 coil elements and T2-weighted turbo spin echo (TSE) sequences of human eyes enucleated because of different intraocular lesions. Imaging parameters were: 40×40 mm field of view, 512×512 matrix, and 700 µm slice thickness. The results were correlated with in vivo ultrasound and histology of the enucleated eyes.ResultsImaging was performed in enucleated eyes with choroidal melanoma, malignant melanoma of iris and ciliary body with scleral perforation, ciliary body melanoma, intraocular metastasis of esophageal cancer, subretinal bleeding in the presence of perforated corneal ulcer, hemorrhagic choroidal detachment, and premature retinopathy with phthisis and ossification of bulbar structures. MR imaging allowed differentiation between solid and cystic tumor components. In case of hemorrhage, fluid-fluid levels were identified. Melanin and calcifications caused significant hypointensity. Microstructural features of eye lesions identified by MRM were confirmed by histology.ConclusionThis study demonstrates the potential of MRM for the visualization and differential diagnosis of intraocular lesions. At present, the narrow bore of the magnet still limits the use of this technology in humans in vivo. Further advances in ultrahigh-field MR imaging will permit visualization of tumor extent and evaluation of nonclassified intraocular structures in the near future.

Ultra High-Field Magnetic Resonance Imaging of a Glaucoma Microstent

Purpose: The aim of the present study was to use 7.1T magnetic resonance imaging (MRI) to determine the correct anatomical position of a non-metallic glaucoma microstent following implantation in rabbit eyes.Materials and Methods: In an in vitro experiment three microstents (made from silicone, polyurethane, and nickel titanium) were embedded in a standard vial filled with agar. In a second series of experiments a prefabricated polyurethane microstent connecting the anterior chamber with the suprachoroidal space (SCS) was implanted in rabbit eyes (n = 12). High-resolution images were acquired ex vivo (n = 6) and in vivo (n = 6) on an ultra high-field MRI unit using a 2-channel coil with four coil elements and T2-weighted turbo spin-echo sequences. Finally, the eyes were dissected and processed for histology.Results: Artifact-free MR imaging of silicone and polyurethane microstents was achieved in vitro, with slightly higher contrast for silicone stents. Image quality for the nickel titanium stent was greatly reduced due to artifacts. MRI examination of rabbit eyes ex vivo and in vivo following polyurethane microstent implantation presented no problems in terms of the size and placement of the coil. The sequences showed good image quality; the full length of the microstent was visualized in cross-section and longitudinal section, and correct anatomical placement was demonstrated from the anterior chamber into the SCS. These findings were verified by histology.Conclusions: The excellent image quality obtained with both of the non-metallic materials generates detailed information about microstent placement, including the surrounding tissues. High-resolution MRI can be used to monitor the anatomical position of a microstent after glaucoma surgery in animal experiments and is therefore a valuable tool for documenting experimental research findings ex vivo and in vivo.

In vivo 7.1 T magnetic resonance imaging to assess the lens geometry in rabbit eyes 3 years after lens-refilling surgery

To evaluate the utility of high-resolution magnetic resonance imaging (MRI) in assessing the normal and refilled lens geometry in rabbits after lens-refilling surgery. University of Rostock, Rostock, Germany. Experimental study. High-resolution ocular MRIs were acquired (7.1 T ClinScan) using a 2-channel coil with 4 coil elements and T2-weighted turbo spin-echo sequences (slice thickness 700 μm, field of view 40 mm × 40 mm) in rabbits after lens refilling surgery combined with intraoperative treatment to prevent lens epithelial cell proliferation. Single slices were used to assess the refilled lenses 3 years postoperatively. The entire geometry (cross-sectional area, radius of curvature, axial and equatorial diameters) of the crystalline and refilled lenses was visualized by in vivo 7.1T MRI 3 years postoperatively (in-plane resolution: 125 μm × 125 μm). In refilled eyes, the capsule and the homogenous silicone polymer remained in close contact with no visible interface. The dimensions of the refilled lens were significantly smaller than those of the crystalline lens of the contralateral eye. High-resolution MRI allows in vivo visualization and analysis of the spatial arrangement of the lens in rabbit eyes after lens refilling surgery and overcomes a number of major limitations in the quantitative evaluation of the lens shape. Further efforts are required to optimize the amount of polymer injected during lens refilling to achieve a predictable refractive outcome after lens refilling surgery. Drs. Stachs, Langner, Sternberg, Martin, Schmitz, Hosten and Guthoff have no financial or proprietary interest in any material or method mentioned. Additional financial disclosure is found in the footnotes.