Ligating Clips for Three-dimensional MR Angiography at 1.5 T: In Vitro Evaluation1
Dominik Weishaupt, MD,
Harald H. Quick, MSc,
Daniel Nanz, PhD,
Michaela Schmidt, RT,
Paolo C. Cassina, MD and
Jörg F. Debatin, MD
1 From the Institute of Diagnostic Radiology (D.W., H.H.Q., D.N., M.S., J.F.D.) and the Department of Surgery (P.C.C.), University Hospital Zürich, Switzerland. Received January 20, 1999; revision requested April 5; revision received June 18; accepted August 12. Address reprint requests to J.F.D., Department of Diagnostic Radiology, University Hospital Essen, Hufelandstrasse 55, D-45122 Essen, Germany (e-mail: debatin@uni-essen.de).
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Figure 1. Photograph of ligating clips 1-18, which are arranged as they were in the phantom. The numbers correspond to the clip numbers indicated in Table 1. Scale of ruler is centimeters.
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Figure 2a. Three-dimensional gradient-recalled MR images depict quantification of artifact size. (a) Clip-induced susceptibility artifact. (b) The areas of signal intensity more than 4 SDs lower or higher than that of the baseline agar in the immediate vicinity of the clip are shown in white and black, respectively. The sum of the black and white areas was defined as "signal intensity distortion." Artifact size was defined as the area of signal intensity distortion minus the clip area.
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Figure 2b. Three-dimensional gradient-recalled MR images depict quantification of artifact size. (a) Clip-induced susceptibility artifact. (b) The areas of signal intensity more than 4 SDs lower or higher than that of the baseline agar in the immediate vicinity of the clip are shown in white and black, respectively. The sum of the black and white areas was defined as "signal intensity distortion." Artifact size was defined as the area of signal intensity distortion minus the clip area.
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Figure 3. Graph depicts excellent correlation between clip length and artifact size on the basis of images obtained with 1.0 signal acquired, with the phantom positioned at a 45° angle to the main magnetic field.
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Figure 4a. Dependence of artifact size on the clip orientation within the main magnetic field. (a-c) Three-dimensional gradient-recalled MR images (5.7/1.7, flip angle of 30°, 0.5 signal acquired) illustrate embedded clips. The phantom is positioned parallel to the main magnetic field in a, at a 45° angle in b, and perpendicular in c. The size of the artifact for titanium clips 1-15 (top five rows) depends on the orientation of the phantom to the main magnetic field. Biocompatible clips 16-18 (bottom row) caused no artifacts. Scale of ruler is centimeters.
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Figure 4b. Dependence of artifact size on the clip orientation within the main magnetic field. (a-c) Three-dimensional gradient-recalled MR images (5.7/1.7, flip angle of 30°, 0.5 signal acquired) illustrate embedded clips. The phantom is positioned parallel to the main magnetic field in a, at a 45° angle in b, and perpendicular in c. The size of the artifact for titanium clips 1-15 (top five rows) depends on the orientation of the phantom to the main magnetic field. Biocompatible clips 16-18 (bottom row) caused no artifacts. Scale of ruler is centimeters.
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Figure 4c. Dependence of artifact size on the clip orientation within the main magnetic field. (a-c) Three-dimensional gradient-recalled MR images (5.7/1.7, flip angle of 30°, 0.5 signal acquired) illustrate embedded clips. The phantom is positioned parallel to the main magnetic field in a, at a 45° angle in b, and perpendicular in c. The size of the artifact for titanium clips 1-15 (top five rows) depends on the orientation of the phantom to the main magnetic field. Biocompatible clips 16-18 (bottom row) caused no artifacts. Scale of ruler is centimeters.
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Figure 5. Dependence of artifact size on the degree of k-space sampling. Three-dimensional gradient-recalled MR image of the phantom was obtained with full-k-space coverage (1.0 signals acquired) with the clip positioned at a 45° angle to the main magnetic field. Compared with the appearance on an image obtained with 0.5 signals acquired (Fig 4b), the artifact of titanium clips 1-15 (top five rows) is smaller. Scale of ruler is centimeters.
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Copyright © 2000 by the Radiological Society of North America.
