MRI features of different sizes of small coil using a water phantom

Objective To explore the imaging characteristics of different sizes of MR small surface coil.Methods A water phantom with NiSO4· 6H2O for Siemens was scanned with 4 cm,7 cm and 11 cm small surface coils in Siemens 3.0 T MR system.T1WI,T2WI,three dimensional reversed fast imaging with steady state precession with diffusion-weighted(3D-PSIF-DWI) and three dimensional fast imaging with steady state precession and fat suppression(3D-FISP-FS) images were obtained.The imaging area,signal intensity (SI),standard deviation (SD) and signal-to-noise ratio (SNR) variations of different depths (from the near to the distant) were measured and compared.Curves according to the SI and SNR data were draw.SI and SNR characteristics of images obtained by L11 separately and used together with spine matrix coil were compared by using signed rank sum test.Results The signal intensity of images scanned by 4 cm,7 cm small surface coil decreased gradually in the depth of 0.2 to 2.2 cm,maintain good signal uniformity in the depth of 2.2 to 4.2 cm,and the signal intensity obtained by 11 cm coil maintain good signal uniformity in the depth of 5.2 cm.The optimum imaging widths of 4 cm,7 cm and 11 cm coil were about 7.0,8.5 and 11.0 cm.As the diameter of the coil increased,the imaging width and depth increased,but the received noise also increased.The SNR gradually reduced from the center to the edge of the coils.The imaging area increased but the local SNR decreased when using L11 coil combine with spine matrix coil,which showed a statistically significant difference (Z=-2.354,P=0.019).Conclusions A suitable size of small surface coil should be chosen according to the location and size of the organ or lesion before clinical MR examination.Other coils should be turned off to improve the SNR. Key words: Magnetic resonance imaging;  Coils;  Comparative study