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.

Objective To explore the value of small surface coil combine with three-dimensional fast imaging with steady state precession and fat-suppression (3D-FISP-FS) sequence in displaying intra-parotid facial nerves segment and parotid ducts.Methods The parotid regions of 18 healthy volunteers who were excluded any parotid diseases were scanned by head&neck coil (36 sides) and 4 cm small surface coil (32 sides) combined with 3D-FISP-FS sequence prospectively. The obtained original
images were treated through MIP, MPR and CPR, The MRI signal characteristics of parotid region structure, the subjective score of image quality, the signal intensity ratio (SIR) of facial nerve/parotid tissue (SIR N) and parotid duct/parotid tissue (SIRD) was calculated, and the displaying rates of the facial nerves and parotid ducts were observed. Wilcoxon matched-samples signed rank sum test was used to compare the scores of head&neck coil and small coil 3D-FISP-FS sequence images, paired t test was used to compare SIRN, SIRD of the two groups, Chi-square test was used to compare of the displaying rate of the facial nerves and parotid ducts in two groups. Results Eighteen volunteers were successfully performed MRI scan of parotid gland. On 3D-FISP-FS sequence images, the parotid gland was showed slightly low signal intensity, muscle tissue was showed medium signal intensity, the vessels were showed slightly high or high signal, parotid segment of facial nerve was showed tortuous line-like high signal intensity, and parotid duct was showed curve high signal intensity, lymph nodes were showed kidney shaped, oval or spindle shaped high signal intensity structures. The subjective scores for head and neck coil and coil images were (2.0 ± 0.9) and (1.5 ± 0.7) respectively, and the difference was statistically significant (Z=-2.714, P=0.007), image quality of small coil group was better than that of head and neck coil group. The SIRN of the two groups was 1.7±0.8 and 2.1± 1.2 respectively, and the SIRD was 1.8±0.7 and 2.5±1.7 respectively, which showed a statistically significant difference between the two groups (t value was 2.978, 2.427 respectively, P value was 0.006, 0.031 respectively).All facial nerve trunks could be displayed by head and neck coil and small coil. On head and neck coil images, 25 sides of temporofacial truck, 15 sides of cervicofacial truck, 17 sides of temporofacial branches, 11 sides of cervicofacial branches, 16 sides of the parotid duct could be displayed. On small coil images, 30 sides of temporofacial truck, 28 sides of cervicofacial truck, 26 sides of temporofacial branches, 23 sides of cervicofacial branches, 27 sides of the parotid duct could be displayed, which showed a statistically significant difference (P<0.05). Conclusion Small surface coil performed better in parotid MR imaging with 3D-FISP-FS sequence than that of head and neck coil, which can simultaneous clearly display the trunk and branches of the intra-parotid facial nerves and parotid ducts.

Objective To investigate the clinical value of three-dimensional sampling perfection with application optimized contrasts using different flip angle evolutions (3D-SPACE) sequence in preoperative evaluation of acoustic neuroma.Methods Totally 57 patients with acoustic neuroma confirmed by surgery and pathology were enrolled.All patients underwent preoperative routine head MR and 3D-SPACE sequence.The position,size and shape of the tumors were observed,and the display rate of surrounding cranial nerves was evaluated with 3D-SPACE sequence.The results were compared with those of conventional MRI and operation.Results All 57 patients were found with single tumor.The tumor in 1 patient (1/57,1.75％) limited in the internal auditory canal,and those in another 56 patients (56/57,98.25％) exceed the internal auditory canal crossing growth.The inner auditory canal fundus in 26 patients (26/57,45.61 ％) were completely filled by the tumors,while those in another 31 patients (31/57) were uncompletely filled.3D-SPACE sequence showed 21 patients (21/57,36.84％) with solid type lesions,35 patients (61.40％,35/57) with solid with cystic type lesions and 1 patient (1/57,1.76％) with cystic type lesion.The coincidence rate of lesion types showed with 3D-SPACE sequence and intraoperative findings was 85.96 ％ (49/57).The display rate of trigeminal nerve internal cisternal segment,lower cranial nerves cisternal segment,abducens nerve cisternal segment,facial nerve internal acoustic meatus segment,facial nerve cisternal segment and acoustic nerve cisternal segment was 100％ (57/57),100％(57/57),75.44％ (43/57),50.88％ (29/57),17.53％ (10/57) and 19.30％ (11/57),respectively,all significantly increased compared with those of conventional MRI (all P＜0.05).Conclusion 3D-SPACE sequence can accurately display the relationship between tumor and adjacent cranial nerves,therefore has important clinical value in preoperative evaluation of acoustic neuroma.

Objective To explore the value of small surface coil combined with three-dimensional double-echo steady-state with water excitation (3D-DESS-WE) sequence in displaying mandibular nerves and their branches. Methods The maxillofacial regions of 52 volunteers were scanned unilaterally by a small surface coil combined with 3D-DESS-WE sequence. According to the Gray's anatomy atlas,MPR and CPR was done according to the anatomic position of mandibular nerve and the branches,the signal characteristics of the nerves and neighboring structures were analyzed. The displaying rate of the mandibular nerves and their branches were evaluated.The image quality and display of the nerve were subjectively scored. The signal intensity(SI) of the nerve and adjacent lateral pterygoid muscle were measured. The signal intensity ratio(SIR) of mandibular nerve/lateral pterygoid muscle (SIRN/M) was calculated. Results Compared with the muscles, the nerve showed iso-signal intensity. The subjective scores for all small coil 3D-DESS-WE images were 3.02 ± 0.82. The displaying rates of V3 trunk,anterior trunk,buccal nerve, posterior trunk,inferior alveolar nerve and lingual nerve were all 100%. V3 posterior trunk,inferior alveolar nerve and lingual nerve showed the best quality scores,which were all about 3 points,and the SIRN/M were about 1. The auricular temporal nerve and masseter muscle nerve were also basically satisfied. The displaying rate of mylohyoid muscle nerve,medial pterygoid nerve and lateral pterygoid nerve was low. Conclusion Small surface coil combine with 3D-DESS-WE sequence performed high-quality in mandibular nerves and their branches MR imaging using MPR,CPR post-processing technology,which are suitable for clinical application.