The Value Of T2W-FLAIR Sequence In The Diagnosis Of Meningeal Disease

Background and Purpose In recent years,with the progress of science and technology,MR technology has made a lot of breakthrough progress,and the fluid attenuated inversion recovery technology is one of the major advances.It was first reported in 1992 by Picker,Hajnal,and applied to the clinic,which made a breakthrough in the diagnosis of nervous system diseases.At home and abroad,it is commonly used in T1 WI to enhance the ab normal enhancement of meninges,which is the first choice for the diagnosis of meningeal lesions,but there are still some limitations.Using T2W-FLAIR sequence specific switching time(inversion time,TI)can obtain clear T2 weighted images in a higher degree of T2 weighted with inhibiting of cerebrospinal fluid signals at the sam e time.With improving the SNR of cortex and periventricular lesion and reducing the artifacts of cerebrospinal fluid flow form,T2W-FLAIR has gradually become a routine sequence of the nervous system.It has been found that the enhanced sequence of T2W-FLAIR is of great value in the diagnosis of meningeal lesions and many scholars have applied it to the diagnosis of brain diseases.However,it has been reported that the enhancement of T2W-FLAIR sequence is of limited value in the diagnosis of meningeal lesions.This study is to evaluate the effction on the sequence of T2W-FLAIR of lowering the concentration of contrast or delaying the start of the scan time(i.e.indirect change of concentration of contrast agent)and to investigate the clinical value of T2W-FLAIR sequence and T1 WI sequence in the diagnosis of meningeal lesions.Materials and Methods Part I 14 plastic tubes with a volume of 10 ml were taken and labeled as "1 to No.14",respectively,which were injected with different concentrations of GD-DTPA(Gd-DTPA,gadolinium pentaacetic acid).Different concentrations of tubes were subjected to T1WI-SPIR and T2W-FLAIR sequence scan and to measure the signal intensity(SI),signal enhancement degree(SED)and signal enhancement rate(SER)value.According to the contrast agent of Gd-DTPA,the plasma concentration of 3min and 60 min is 0.6 × 10-3mmol/ml ~ 0.24 × 10-3mmol/ml.Part II In this study,252 cases of meningeal disease from January 2013 to December 2016 were selected from our hospital with male 132 cases,female 120 cases,aged 6 ~76 years,mean age 42.33±12.11 years old.With 65 cases of viral meningitis,51 cases of tuberculous meningitis,69 cases of meningeal metastases,67 cases of meningeal changes after trauma,we received clear T1 WI,T1WI-SPIR enhanced,T2W-FLAIR plain and T2W-FLAIR enhanced images from al l cases and measured accurate signal intensity value.Another 10 healthy volunteers,6 males and 4 female patients with aged 35 ~65 years,mean age 50.31±9.55 years old.We received clear T1 WI,T1WI-SPIR enhanced,T2W-FLAIR plain and T2W-FLAIR enhanced images from all volunteers and measured accurate signal intensity value.All volunteers and patients before the exclusion of MRI contraindications(such as with a pacemaker,artificial heart valve,artificial cornea,metal artificial listening to bone and severe claustrophobia,etc.),Before the volunteers and patients into the examination room was details of the whole process of scanning and precautions,check the cotton ball with the ear,take the supine position,double upper limbs naturally placed on both sides of the body,calm breathing,try to keep the process of static.We use Philips Achieva 1.5T double gradient superconducting magnetic resonance imaging system,using 16-channel orthogonal SENSE head coil.According to head scan positioning of Zhenghan Yang editing the "magnetic resonance imaging technology guide",horizontal axis scan`s plane is parallel to the lower edge of the corpus callosum and the lower edge of the compression part of the connection,sagittal plane is pa rallel to the brain longitudinal deviation,coronal scan surface cross-sectional positioning on the image and the vertical deviation of the brain,sagittal positioning The imaging level is parallel to the brainstem.The rats were treated with Gd-DTPA(15ml/bottle)30ml at a rate of 2ml/s,after 5min with transection,sagittal and c oronal SE T1W-SPIR enhanced sequence,after 12 min with T2W-FLAIR enhances transversal,sagittal and coronal scans.Image processing was performed by Hina medical information workstation.Result 1.From the No.1 test tube to No.14 test tube,the concentration of the test tube reduced by multiple.In T2W-FLAIR sequence,8-14 test tube development,the highest signal strength in the No.12 test tube with the concentration about 0.24 × 10-3mmol/ml.In T1WI-SPIR enhanced sequence,5-14 test tube development,the highest signal strength in the 9 test tube with the concentration about 1.95 × 10-3mmol/ml.When the contrast agent concentration was 0.49 × 10-3mmol/ml in the No.11 test tube,the signal intensity of the two sequences is closest.When the concentration of the contrast agent was greater than 0.49 × 10-3mmol / ml,the s ignal intensity of T1W-SPIR enhanced sequence was higher than that of T2W-FLAIR.With the decrease of the contrast agent concentration,the signal intensity in T2W-FLAIR sequence is significantly higher than that of in T1W-SPIR sequence.The signal intensity of the T2W-FLAIR was much higher than that of the T1W-SPIR sequence when the concentration of the control agent was in the No.12 test tube(0.24 × 10-3mmol/ml)and the No.13 test tube(0.12 × 10-3mmol/ml).From the signal enhancement degree(SED)curve,the sensitivity of the T2W-FLAIR sequence was greater than 2 times the T1W-SPIR when the contrast agent concentration was in the No.12 test tube(0.24 × 10-3 mmol/ml)and No.13 test tube(0.12 × 10-3 mmol/ml).From the signal enhancement rate(SER)curve,when the contrast agent concentration was in the No.12 test tube(0.24 × 10-3mmol/ml)and the No.13 test tube(0.12 × 10-3mmol/ml),compared to T2W-FLAIR sequence and T1W-SPIR sequence,the SER value of little difference,but its clinical application value is not affected.2.The viral meningitis group compared with the other groups,age differences(P > 0.05),However,tuberculous meningitis and meningeal metastasis were no significant differences in tumor group and TBI group in age and gender(P < 0.05).3.MRI imaging analysis of viral meningitis Viral meningitis in the MRI scan image with the performance of the ditch blur,the scope is di fficult to defined,enhanced scan sequence was extensive and fine line-like abnormal enhancement.No cases of dural invasion,the amount of parietal lobe adjacent to the meningeal signal strength for reference,calculate the signal strength value.The T2W-FLAIR enhanced,30 cases of severe meningitis(range <3cm),extensive invasion(range> 3cm)35 cases,signal intensity of 1156.55 ± 20.16;The T1WI-SPIR enhanced sequence,meningeal limitation(range <5cm)40 cases,extensive invasion(range> 5cm)25 cases.The signal intensity was 921.26 ± 25.22.The intensity of T1 WI was higher than that of T2W-FLAIR(P <0.05).There was a significant difference between the two groups.4.MRI imaging analysis of tuberculous meningitis Tuberculous meningitis in the MRI scan image is similar to viral meningitis.The definition is more fifficult to define.The limit is more blur than viral meningitis and the scope is m ore difficult to define.Enhanced scan sequence was extensive and fine line-like abnormal enhancement.No cases of dural invasion,the amount of parietal lobe adjacent to the meningeal signal strength for reference,calculate the signal strength value.The T2W-FLAIR enhanced,22 ca ses of severe m eningitis(range <3cm),extensive invasion(range> 3cm)29 cases,signal intensity of 1396.33 ± 13.11;The T1WI-SPIR enhanced sequence,meningeal limitation(range <5 cm)30 cases,ex tensive invasion(range> 5cm)21 cases.The signal intensity was 1209.35 ± 20.92.The intensity of T1 WI was higher than that of T2W-FLAIR(P <0.05).There was a significant difference between the two groups.5.MRI imaging analysis of meningeal metastases The MRI fi ndings of meningeal metastases depend on their relationship with the meninges.Direct tumor invasion mainly for meningeal dura arachnoid enhancement,brain tumor to invade adjacent to th e surface of the brain,pia mater and dura mater,showed lesions adjacent to the l imitations of meningeal enhancement,the shape of "rat tail".Hematogenous meningeal metastasis and cerebrospinal fluid meningeal metastasis mainly perform mater-arachnoid enhancement.In this case,the T2W-FLAIR enhanced sequence,the dura mater-arachnoid enhancement 16 cases,t he pia mater-arachnoid enhancement 45 cases and the mixed enhancement(i.t whole meningeal enhancement)4 cases,no meningeal enhancement 1 case.The signal intensity is 1575.81 ± 110.66.The T1W-SPIR enhanced sequence,the dura mater-arachnoid enhancement 16 cases,the pia mater-arachnoid enhancement 43 cases and the mixed enhancement(i.t whole meningeal enhancement)4 cases,no meningeal enhancement 3 cases.The signal intensity is 1110.57 ± 120.77.The enhancement degree of T1 WI was lower than that of T2W-FLAIR(P <0.05).There was a significant difference between the two groups.6.MRI imaging analysis of brain after traumatic brain injury The MRI findings of the brain after traumatic brain injury are limited to the local area of dura arachnoid enhancement.Some patients showed focal or diffuse leptomeningeal enhancement or meningeal enhancement.In this group of cases,the T2W-FLAIR enhanced sequence,,the pia mater-arachnoid enhancement 55 cases and the mixed enhancement(i.t whole meningeal enhancement)10 c ases,no men ingeal enhancement 2 cases.The signal intensity is 1256.88 ± 320.71.The T1W-SPIR enhanced sequence,the signal intensity is 1103.22 ± 410.03.The enhancement degree of T1 WI was lower than that of T2W-FLAIR(P <0.05).There was a significant difference between thetwo groups.7.Comparison of signal intensities between T2W-FLAIR sequences and T1 WI sequences in each group There was a significant difference in signal intensity between the T2W-FLAIR sequence and the T1 WI sequence enhanced image of the tuberculous meningitis group,the meningeal metastasis group and the traumatic brain injury group(P < 0.05).Enhanced T2W-FLAIR sequence signal strength of the size of the image is as follows: the meningeal metastasis group,tuberculous meningitis group,brain injury group;T1WI sequence enhanced signal intensity of the size of the image is as follows: the tuberculous meningitis group,brain injury group,meningeal metastasis group.Conclusion 1.The T2W-FLAIR sequence can inhibit the cerebrospinal fluid signal and obtain clear T2 WI images,which can reduce the a rtifact of cerebrospinal fluid flow and get a good lesion/brain tissue contrast.2.The T2W-FLAIR sequence i s more sensitive to the low concentration contrast agent,and it is more likely to be used for the contrast agent with lower concentration than the T1 WI enh ancement sequence.It is very important to select the appropriate concentration for the T2W-FLAIR sequence imaging.3.According to the brain articals described abnormal enhancement of meninges can be divided into type 3:(1)dural-arachnoid enhancement(2)pia mater-arachnoid enhancement(3)meningeal enhancement.Viral meningitis and tuberculous meningitis is manifested as pia mater-arachnoid enhancement.Meningeal metastases are different depending on the mode of metastasis.The memingeal enhancement of brain after trauma has three different enhancement ways.Comparing the intensity of each image signal of different sequences,the enhancement degree of T1W-SPIR enhanced sequence is lower than that of T2W-FLAIR enhanced sequence.4.T2W-FLAIR enhanced sequence using contrast agent at low concentration and late start scanning time,it can obtain satisfactory meningeal T2W-FLAIR enhanced image and the signal intensity was higher than that of T1 WI.The signal intensity of image sequences are more likely to display meningeal lesions in contrast with low concentrations.