Experimental Study On Multiple MRI Sequences Of Magnetic Resonance Imaging In Lumbar Zypophyseal Joints

Objective:To explore the optimal scanning sequence and thus to evaluate the capability and limitation of MRI for pigs lumbar zypophyseal joints imaging,then further to set up the guidelines for humans'MRI examination.Methods:6 fresh lumbar spines from adult pigs were inclined sagittaly scanned by Siemens 1.5T MRI,while a bag of 100ml saline was placed nearby to imitate joint fluid.The scan sequences were including:fast spin echo T1-weighted imaging(FSE T1WI),fast spin echo T2-weighted imaging(FSE T2 weighted T2WI),fat saturation proton density-weighted imaging(FS PDWI),three-dimensional fast low angle shot imaging(3D-FLASH),and water excitation three-dimensional fast low angle shot imaging(WE 3D-FLASH).All datas of 6 pairs of L3/L4 zypophyseal joints were measured by two doctors using double-blind method.The signal-noise ratio(SNR) for articular cartilage, contrast-noise ratio(CNR) for cartilage versus bone cortex,cartilage versus bone marrow,cartilage versus saline,and cartilage versus synovial fold were calculated.Right after scanning was finished,the lumbar spine were snap freeze-stored, sagittally incised along the lumbar zypophyseal joints where marked by MRI,and photographed to compare the gross specimen with corresponded MRI images. Moreover,the thicknesses of sagittal center of 6 pairs of L3/L4 zypophyseal joints cartilage were measured by vernier caliper.The thickness of cartilage were compared to the relevant MRI images.Joint capsule,synovial folds send to histological examination.Results:1.Comparison of the four different flip angle(FA10°,FA 20°,FA 30°,FA40°) 3D-FLASH sequences:The highest cartilage SNR and best CNR of cartilage versus bone cortex were both found in the 3D-FLASH(FA 20°) sequence,which were significantly different from the other three 3D-FLASH sequences.The better CNR of cartilage versus bone marrow,cartilage versus saline were found in the 3D-FLASH(FA 20°)sequence.3D-FLASH(FA 20°)sequence is better than the other three types of 3D-FLASH sequences in Cartilage imaging.2.Comparison of the four different flip angle(FA10°,FA 20°,FA 30°,FA40°) WE 3D-FLASH sequence:The highest cartilage SNR,best CNR of cartilage versus bone cortex,and best CNR of cartilage versus bone marrow were found in the WE 3D-FLASH(FA 20°) sequences,which were significantly different from the other three 3D-FLASH sequences.The better CNR of cartilage versus saline were found in the WE 3D-FLASH(FA 20°) sequence.WE 3D-FLASH(FA 20°) sequence is better than the other three WE 3D-FLASH sequences in Cartilage imaging.3.The highest cartilage SNR and best CNR of cartilage versus bone cortex were both found in the 3D-FLASH(FA 20°) sequence,which were significantly different from those in the PDWI,FSE T1WI,T2WI sequences,(P＜0.05),whereas not statistically significant(P＞0.05) in the WE 3D-FLASH(FA 20°)sequence.The highest CNR of cartilage versus bone marrow was seen in WE 3D-FLASH(FA 20°) sequence.It was statistically significant compared to that in FS PDWI,FSE T1WI,T2WI sequences respectively,but the difference was not significant compared with 3D-FLASH(FA 20°)sequence.(P＞0.05).Both the FS PDWI and T2WI sequences displayed ideal CNR of cartilage versus saline,there was no significant difference between them(P＞0.05).The lowest SNR of cartilage versus saline was shown in 3D-FLASH(FA 20°) and WE 3D-FLASH(FA 20°) sequences,the difference was not statistically significant(P＞0. 05).However,they were significantly different compared with FS PDWI and T2WI sequences,also with 3D-FLASH(FA 20°) and WE 3D-FLASH(FA 20°) sequence (P＜0.05).4.3D-FLASH(FA 20°)and WE 3D-FLASH(FA 20°)sequences were relatively better than FS PDWI when comparing the thickness of articular cartilage.5.There was a good correlation between the histologic features of joint capsules and synovial folds derived from MRI and the histologic sections,between the anatomic features of joint capsules and synovial folds derived from MRI and the gross specimen.Highest-quality images of the synovial folds and joint capsules were obtained for all lumbar zypophyseal joints examined in 3D-FLASH(FA 20°),WE 3D-FLASH(FA 20°) sequences.There was a good contrast between the synovial folds and cartilage in 3D-FLASH(FA 20°),WE 3D-FLASH(FA 20°) sequences.Conclusions:3D-FLASH(FA20°) sequence and the derivate WE 3D-FLASH(FA20°) sequence had the best definition of cartilage images and were mostly close to the real thickness.3D-FLASH(FA 20°)and WE 3D-FLASH(FA 20°)sequences have significant advantages compared with the other sequences in imaging joint capsules and synovial folds of lumbar zypophyseal joints.They are possibly the optimal scanning sequences for lumbar zypophyseal joints MRI imaging.FSE T2WI sequence can do a good job for lumbar zypophyseal joint effusion。The results of this study provides a basis for future in humans' lumbar zypophyseal joints MRI examination.