3D-Printed Microstrip Resonators for 4.7T MRI

• Author / Creator

  Javidmehr, Saeed

• Radiofrequency (RF) coils are a substantial part of Magnetic Resonance Imaging System. Microstrip transmission line (MTL) coils are widely used as they have a low coupling between array elements and negligible radiation loss. Matching and tuning capacitors are usually soldered to MTL coils in order to tune them to Larmor frequency and match them to 50Ω. Typically, these coils need to be adjusted according to different sample loadings (patients) in MRI. Availability and high cost of MR compatible variable or fixed capacitors for tuning and matching and the labour-intensive work encourage us to find an easy way to satisfy these requirements with low cost and less process steps.
  Here, we propose to use rapid prototyping (additive manufacturing), such as 3D printing, to overcome the existing problems and print MRI coils all at once including the matching/tuning capacitors. Additive Manufacturing is an emerging manufacturing technology that offers new prototyping and fabrication methods to RF world. Additive manufacturing technology could potentially grant reduction of fabrications steps for MTL coils. A typical desktop 3D printer is capable of printing only plastics, such as ABS and PLA. Moreover, there is no low cost 3D printer to provide metal and plastic printing in one machine. In this thesis, a low cost desktop 3D printer has been modified to add ink printing capability.
  In addition, the design procedure of MTL coils with parallel plate capacitors as matching and tuning capacitors is reported. 3D printing as a new technology is adopted to fabricate the MTL coils. The MTL coils with built-in parallel plate capacitors from plastic materials and two different conductive materials (copper tape and silver ink) are designed and fabricated for 4.7 T MRI systems. Moreover, the fabricated coil’s performance in terms of quality factor and SNR is investigated.
  Based on the results of this thesis, 3D printing technology provided faster prototyping process for MRI coils. It also allowed design iterations to increase the coil’s performance in MRI. 3D-printed parallel plate capacitors integrated with MTL coils eliminated the repetitive work of soldering, and mitigated the process for iterations during measurements. Thermoplastic material such as ABS and PLA showed comparable SNR and efficiency values to standard low loss foam, and therefore they can be used in MR applications. Ink-printed MTL coils showed lower performance compared to low loss foam, and that can be attributed to the ink conductivity.

• Subjects / Keywords

  • Coils
  • 3D-printing
  • Microstrip

• Graduation date

  Spring 2015

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R35717V47

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.