High-Sensitivity Coil Array for Head and Neck Imaging: Technical Note
Roland G. Henrya,
Nancy J. Fischbeina,
William P. Dillona,
Daniel B. Vignerona and
Sarah J. Nelsona
a From the Department of Radiology, University of California at San Francisco.
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FIG 1. Schematic drawings of overlapping 7 x 8-cm octagonal elements used to construct the head and neck surface coil array
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FIG 2. Graph shows the relative SNR in units of the average SNR from the volume coils for the head and neck surface coil array (smooth lines); temporomandibular joint phased array coils (dotted-and-dashed line); and volume head and neck coils, which are the anterior neck coil (dashed line, ANC) and quadrature neck coil (dotted line, QNC). The SNR for the head and neck phased array and temporomandibular joint phased array were calculated from a region near the surface of the phantom (HNPA Edge and TJMPA Edge, respectively) and also from the center of the phantom for the head and neck phased array (HNPA Center). The SNR for the volume coils were calculated from regions near the center of the phantom for best uniformity
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FIG 3. Graphs shows the right-to-left SNR for the head and neck surface coil array in units of the average SNR from the volume coils. The head and neck surface coil array has a transaxial SNR more than four times higher than that of the volume coil as far as 2 cm inside the phantom at the center of the coils (125 mm in fig 2)
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FIG 4. 2D T2-weighted FSE MR images (4-mm section, 16-cm FOV, 256 x 256 matrix) of a healthy volunteer's neck. A bright region at the posterior edge is the result of inadequate edge completion.
A, Uncorrected image.
B, Images corrected with a low-pass filter algorithm.
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FIG 5. 3D T2-weighted FSE MR images (1-mm section, 18-cm FOV, 256 x 192 matrix) of a healthy volunteer's neck. As in figure 4, the edge completion at the posterior edge of the images is suboptimal.
A, Uncorrected image.
B, Image corrected with a low-pass filter algorithm.
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FIG 6. Comparison of corrected FSE MR images obtained with the head and neck phased array coil.
A, 2D images (256 x 256 matrix, 4-mm section, 30 images, 16 [axial] x 15 [transaxial]-cm FOV).
B, 3D images (256 x 192 matrix, 1.5-mm section, 18 [axial] x 18 [transaxial]-cm FOV). The SNR is slightly worse with the 3D sequence, but resolution and coverage are better in the same imaging time.
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FIG 7. A and B, Reformations from corrected axial T2-weighted 3D FSE MR data (1.0-mm section thickness, 18 cm FOV, 256 x 192 matrix). The thin sections allow for good-quality reformations, and even small lymph nodes are clearly depicted
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FIG 8. Axial 2D FSE MR images (4-mm section, 16-cm FOV, 256 x 256 matrix).
A, Images acquired with the head and neck phased array coil. Compared with the anterior neck coil, the head and neck phased array has a higher SNR that results in sharper images with better definition of small structures, such as cervical lymph nodes.
B, Images acquired with the anterior neck coil.
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AJNR - American Journal of Neuroradiology