1. Scan Equipments and Parameters
The Scan was used Skyra Elf 3.0T (Magnetom Skyra Elf, Siemens Healthcare, Erlangen, Germany) and 16 channel Foot and Ankle Coil(Foot and Ankle 16A 3T Tim Coil, Siemens Healthcare Gmbh, Germany) and the detailed MR scan parameter is summarized in [table]1.
2. Phantom and Self-made Carbon Fabric Fiber Tool
1) Phantom
The phantom uses the Foot and Ankle Phantom(3300ml) provided by SIEMENS[fig]2. The phantom solution is a phantom in which NiSO4, Nacl, and H20 are properly distributed to prevent bubbles from being generated(1,25g NISO4 * 6H20. 2,6g NaCl).
2) Self-made Carbon Fabric Fiber Tool
In order to prevent direct skin contact of the fabric and minimize the absorption and infection of sweat that occurs during the MRI scan, a carbon fabric fiber made of carbon film 3K(KN#c125, 0.23mm, 200g/m2) was placed between a tarp made of polyethylene and polyester and then sealed. The overall shape was made in a shape similar to Foot and Ankle Coil using acrylic [fig]3,[fig]4.
3. Image Aquisition
Two identical Foot and Ankle Phantom(3300ml) provided by SIEMENS and Chiken legs were used to know RF shielding performance by the carbon fabric fiber and the effect on adjacent areas, and the one without the carbon fabric fiber was classified as a control group. The T1 and T2 Axial images of standard group(Used Tool) and control group(Not Used Tool) were obtained[fig]5,[fig]6.
4. Image Analysis and Comparison(SNR)
SNR measurement was performed by NEMA method[4][5][6]. We measured SNR of phantom and chicken leg in T1, T2 axial according to whether or not the Self-made carbon fabric fiber tool. The measurement software used the RadiAnt DICOM Viewer 3.4.2 (build on decision 9, 2016). First, the In phantom image, ROIs on the reconstructed signal image was designated to be 75% rectangle of the total area of the phantom images to obtain the average signal intensity value, and standard deviation value of noise levels in 4 surrounding areas were measured [6][fig]7. On the chicken leg images, the average signal intensity of three ROIs of fat, muscle, bone among anatomical structures and standard deviation of noise levels in 3 surrounding areas were measured[fig]8. SNR was calculated by substituting the two values obtained . The value was set as the average measured twice by 4 observers.
5. RF Heating Test of Carbon Fabric Fiber Tool
For an RF heating test, thermographic camera was used UWEI(UW832)[fig]9. And the maximum SAR was set below 4 W/kg in accordance with the American Society for Testing and Materials (ASTM) Safety Standard and the FDA guideline [7],[8]. The scan was repeated for 60 minite and temperatures were measured every 5 minutes. The measurers were repeated twice at one week intervals in succession
6. Qualitative evaluation
Three evaluation items [9], including image noise, image blur, and aliasing artifacts, were performed twice by three observers (1; poor, 2; model, 3; fair, 4; good, 5; excellent) with the obtained Phanotm images and chicken leg images.
-Statistical analysis
SPSS 23 (SPSS Inc., Chicago, IL, USA) was used for statistical tests. For comparison of SNR and Scores used wilcoxon signed rank test among nonparametric tests, and the temperature change of the carbon fabric fiber in Self-made Tool was repeated measure ANOVA test. All statistical methods were interpreted as statistically significant differences when p<0.05.