Value Of MRI3D-SHINKEI Sequence In Olfactory Bulb And Its Lesions

Objective:The methods of olfactory examination and olfactory pathway imaging are varied and inconsistent,and there is still a lack of ideal display technology of olfactory nerve,olfactory bulb and olfactory tract.In this study,we compared magnetic resonance three-dimensional nerve-SHeath signal increased with INKed rest-tissue RARE Imaging(3D-SHINKEI)sequence with 3D-DRIVE sequence,to investigate the advantages and clinical value of 3D-SHINKEI sequence with image post-processing techniques in showing the olfactory bulb and its lesions.Materials and methods:In this study,40 patients,15 males and 25 females,aged 20 to 70 years(mean age 45.4±14.5 years),with olfactory disorders diagnosed clinically in the Department of Otorhinolaryngology of Shandong Provincial Hospital between November 2020 and November 2022 were included.30 healthy volunteers,12 males and 18 females,aged 20 to 68 years(mean age 44.8±13.7 years)were also included.All healthy volunteers had no history of olfactory dysfunction or neurological related diseases.All patients were underwent nasal endoscopy.Clinical assessment of olfactory function was based on the Sniffin’ Sticks olfactory stick test.MRI scans were performed using Philips Achieva 3.0 T MRI scanner with 32-channel head coil.All subjects were underwent conventional MRI plain scan,3D-SHINKEI and 3D-DRIVE sequence scans of the olfactory bulb.Two head and neck neuroradiologists scored the image quality of 3D-SHINKEI and 3DDRIVE sequences in 30 healthy volunteers.The scoring criteria were divided into four levels based on tissue contrast,signal homogeneity and the presence of artifacts.The SNR,CNR,and SIR values of the bilateral olfactory bulbs of the two sequences were measured in 30 healthy volunteers.MRI olfactory bulb volume measurement and morphological typing were performed on 3D-SHINKEI sequence images of all subjects.Statistical analysis was performed to correlate the Sniffin’ Sticks olfactory stick test scores with MRI olfactory bulb volume in patients with olfactory impairment.3D-SHINKEI and 3D-DRIVE sequences olfactory bulb image quality scores were evaluated by Mann-Whitney U test.Two paired samples t-test was used to compare the SNR,CNR,and SIR of the two sequences.The difference in olfactory bulb volume between the olfactory dysfunction group and the volunteer group was tested by two independent samples ttest.The comparison of olfactory bulb morphological typing of 3D-SHINKEI olfactory bulb imaging between the olfactory dysfunction group and the control group was performed by Fisher’s exact probability method.Correlation analysis of olfactory bulb volume and olfactory function was performed using Pearson correlation analysis.Take P<0.05 was considered statistically significant.Results:The subjective scores of 3D-SHINKEI images in the healthy volunteer group were higher than those of 3D-DRIVE sequence,and the differences were statistically significant(P<0.05).SNR and SIR of 3D-SHINKEI sequence were significantly higher than those of 3D-DRIVE sequence,and the differences were statistically significant;the differences of CNR between them were not statistically significant(P>0.05).The differences were statistically significant(all P<0.001)when comparing the left and right sides and the total olfactory bulb volume between the healthy volunteer group and the olfactory impairment group,and the olfactory bulb volume was reduced in the olfactory impairment group.There were 34 cases of olfactory bulb morphological typing type D in the olfactory impairment group and 25 cases of type J in the healthy control group,and the difference between the two groups was statistically significant(P<0.001).The morphological typing of the olfactory bulb could be visualized in three dimensions by multiplanar reconstruction and volumetric display.There was a moderate positive correlation between left,right and total olfactory bulb volumes and TDI scores of the olfactory function test in the olfactory impairment group(r=0.604,P<0.001;r=0.621,P<0.001;r=0.661,P<0.001).Conclusions:3D-SHINKEI sequence showed better olfactory bulb image quality than 3D-DRIVE sequence,and 3D-SHINKEI sequence showed better structure inside olfactory bulb than 3DDRIVE sequence.3D-SHINKEI sequence was reliable in determining olfactory bulb volume of normal volunteers,and could display the structure of olfactory bulb in three dimensions.The volume of olfactory bulb measured by the olfactory dysfunction group with 3DSHINKEI sequence was significantly correlated with olfactory function.The volume measurement of olfactory bulb can be used as an important reference index to evaluate olfactory function.