Multi Scroll Coil Setup for Simultaneous Acquisition of MR Microscopy Data of 3D Printed Cells
Gangchea Lee1, Jeongin Choi2, Eberhard Munz3,4, Ibrahim Tarik Ozbolat 5, Michael Lanagan5, and Thomas Neuberger1,6

1Bio Engineering, Pennsylvania State University, University Park, PA, United States, 2Physics, Pennsylvania State University, University Park, PA, United States, 3Experimental Physics 5, University of Wurzburg, Wurzburg, Germany, 4Leibniz Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany, 5Engineering Science and Mechanics, Pennsylvania State University, University Park, PA, United States, 6Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, United States


High resolution, and high Signal to Noise Ratio (SNR) images in Magnetic Resonance Imaging (MRI) require long imaging times. In this work a setup for two separate shielded scroll coils with a common gradient and magnet was introduced to produce two independent three dimensional MRI data sets for MR microscopy. The RF coils and shields were designed, fabricated, and tested. 3-D printed cell samples were imaged using the fabricated set up. Overall, two samples could be acquired with a larger field of view and a similar SNR in the same time compared to a single sample in a solenoid.


One of the biggest drawbacks of Magnetic Resonance Imaging (MRI) is the long acquisition time that is necessary to achieve high Signal to Noise Ratio (SNR) in high resolution data sets. Some of the ways to overcome this challenge are 1) the use of a higher main magnetic field to increase the net magnetization, 2) the fabrication of the optimized Radio Frequency coil (RF coil) which generates higher magnetic field (B1) with given power [1], and 3) Imaging several samples at the same time [2]. This project aimed to micro-image three dimensionally (3-D) printed cells more effectively by designing a new probe setup that satisfies all given tactics. Two scroll coils with appropriated shielding for decoupling were constructed to image two separate 3-D printed cell samples with 14.1 T high field MRI.


Two 2 turn scroll RF coils were fabricated (Figure 1). On top of the adhesive side of the copper tape, two layers of polytetrafluoroethylene, and polyimide silicon adhesive were placed. This layered piece was cut as shown in Figure 1b. It consists mainly out of the scroll coil body (51.9 mm x 26.3 mm rectangle) and the legs that deliver the current to the coil body. The cut out piece was rolled 2 turns such that the inner diameter was about 7mm. The resonance frequency was measured to be in between 680 MHz and 700 MHz. After attaching the tuning and matching network, the scroll coils were able to fine tune to 600 MHz, which is the Larmor frequency of the 14.1 T MRI machine.

The RF shield was fabricated as illustrated in Figure 2. The shield base to place up to 4 RF coils in separate chambers and two wings were designed using Solidworks (Dassault Systèmes SolidWorks Corporation, Waltham, MA, USA). The shield base and the wings were designed so that they provide a sealed room for each of the RF coils. These designs were 3-D printed with polylactic acid (PLA) using a LulzBot Taz 5 (Aleph Objects Incorporated, Loveland, CO, USA), and covered with copper tape. Two RF coils were placed in each of the bottom two quadrant of the shield base. With fine tuning and matching for both channels the following S-parameters at 600 MHz were measured to check the separation of the RF coils: S11=-40dB, S22=-32dB, and S12/S21=-26dB.

The scroll coils and the shield were tested by imaging 1% Magnevist water phantoms in 4.5mm inner diameter glass tubes at 14.1 T. A 2-D gradient echo image was taken using slice selection direction horizontal to both samples. The Field Of View (FOV) of 30mm x 30mm was chosen to enclose both samples in the slice. The scanner automatically sums up the two data sets from the different channels into one data set as shown in figure 3a. Therefore, MatLab (MathWorks Incorporated, Natick, MA, USA) was used to get two separate raw data sets and the processed images of the two separate channels (Figure 3b, and 3c).

Fixed 3-D printed cells were imaged using both channels. The cells were inserted in 1.7mm inner diameter glass tubes filled with phosphate buffered saline (PBS). Two samples were prepared and inserted into the two coils. With a FOV of 10mm x 2mm x 2mm, a matrix size of 480 x 96 x 96, a TR of 1000ms, and 8 averages the standard spin echo sequence took 20hr 29min scan.

Results and Discussion

The SNR of the water sample in Figure 3b and 3c were 10761 and 947. The SNR of the cross talk in Figure 3b and 3c were 63 and 133. Therefore, the cross talk can be neglected.

Figure 4a and 4c show MR images of two separate 3-D printed cells in the two coils. The SNR of the PBS was 9.4 and 6.3 respectively. The difference was probably due to the shimming that was optimized for the sample in the first channel. Compared to images using a 3 turn solenoid coil (SNR=9.4), a similar SNR was achieved while a much larger and homogeneous FOV in read direction could be utilized. Figure 4b and 4d show volume rendered 3-D printed cells in Avizo 8.0. This approach allowed imaging two samples within the time for a single sample to be imaged with one RF coil, while the SNR remained constant. Future research can be conducted with four shielded RF coils to further reduce the imaging time.


This work was supported by the National Science Foundation under Award DBI-1353664 and the Research Experiences for Undergraduates program of physics department at Pennsylvania State University


[1] H. Benveniste and S. Blackband, “MR microscopy and high resolution small animal MRI: Applications in neuroscience research,” Prog. Neurobiol., vol. 67, no. 5, pp. 393–420, 2002.

[2] N. A. Bock, N. B. Konyer, and R. Mark Henkelman, “Multiple-mouse MRI,” Magn. Reson. Med., vol. 49, no. 1, pp. 158–167, 2003.


Figure 1: Scroll coil was fabricated by layering of copper tape, Teflon and Polyimide silicon adhesive (1a). Dimension of layers (1b) was chosen to constructed scroll coil with 2 turns (1c). Matching network was added to fine tune at 600 MHz (1d).

Figure 2: Shield base (2a) and wings (2b) were designed. The assembly of those parts make the sealed room for the RF coils (2c). Shield assembly was 3-D printed and covered with copper tape (2c) to decouple the coils from each other.

Figure 3: Two shielded RF coils were tested with 1% Magnevist water phantoms. Two water samples were imaged simultaneously in the scanner (3a) and two images were separately reconstructed in MatLab (3b and 3c).

Figure 4: Two samples of 3-D printed cells in PBS were imaged simultaneously with two shielded scroll coils (4a and 4c). The volume was rendered for each of the 3-D printed cells (4b and 4d).

Proc. Intl. Soc. Mag. Reson. Med. 25 (2017)