Dissertation > Medicine, health > Clinical > Diagnostics > Diagnostic Imaging > Magnetic resonance imaging

The Preliminary Study of Animal Model Built and Clinical Imaging Analysis of Crypotococcal Meningoencephalitis

Author WangYueBo
Tutor ZhangZhiYong
School Fudan University
Course Medical Imaging and Nuclear Medicine
Keywords Cryptococcus neoformans meningoencephalitis animal model pathology changes 1.5T dedicated coil image quality AIDS
CLC R445.2
Type Master's thesis
Year 2011
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[Background]:Fungal infection in immunocompromised host is popular. In recent years, it has dramatically risen with the increase of immunity diseases as AIDS, the vastly performed of organ transplantation and the abuse of antibiotic and the immunosuppressant. Cryptococcal meningoencephalitis is a deep systemic fungal disease. It has a delitescence onset and has no clinical and imaging specificity. It can be easily misdiagnosed with high mortality. We will do animal experiment study and investigate clinical cases with cryptococcal meningoencephalitis retrospectively.Part I, The animal experimentation on cryptococcal meningoencephalitis in Rat——MRI Appearances and Pathology research[Objective]To optimize the optimal scanning parameters of 1.5T MRI with the dedicated rat coil. To study the early imagines of ctyptococcal meningitis and the correlation with the pathological changes. To compare the superiority of the two ways for short term imagine study of cryptococcal meningoencephalitis.[Material and Method]1. Technical parameters:6 rats were respectively scanned with T1WI with 585/40ms,450/31ms,700/50ms;T2WI with 2261/120ms,1892/100ms,2800/140ms;slice thickness with 2mm,1mm,0.8mm;FOV with 60/45mm,80/60mm,40/30mm;b value 600s/mm2,800s/mm2,1000s/mm2;FLAIR with 6000/140ms,7000/160ms,5000/12 Oms. Two experienced radiologists evaluated the imaging quality together, and investigated the optimal scanning parameters.2. Imaging study:90 Wistar rats were divided into group 1, intracranially infected and group 2, tail vain infected. Group 1 were subdivided into two subgroups which were infected by Cryptococcus neoformans suspension(36 rats) and saline(6 rats). The infected group was divided into six subgroups, each subgroup 6 rats. The first five subgroups were observed respectively at the 3rd day,7th day,14th day,21st day,28th day. The sixth subgroup was dynamic observed group and dissected at the 28th day. The saline group was observed at the same time point and then do pathology. One rat was dynamic observed. The tail vail infected group was divided into the suspension infected group(36 rats), the sole immunosuppressive infected group(6 rats) and saline group(6 rats). Tail vain infection group rats were injected intraperitoneally with cyclophosphamide (150mg/Kg) three days before injection. The suspension infected group was also divided into 6 subgroups, each subgroup had 6 rats. The 6th group was dynamic observed group and dissected at the 28th day. The last two groups were observed at the same time point and one was dynamic observed one. The intracerebral group was injected the suspension of Cryptococcus neoformans of concentration 1×105 cfu/ml into the lateral ventricle with dose of 60ul. The tail vein group was injected with 1×105 cfu/ml into the tail vein with dose of 0.01ml. Rats were fed in P2 laboratory and observed every day. Scan with the conventional series at 1.5T MRI scanner with special animal coil. Dissect immediately after scanning and take brain to detect the different pathological changes at different time point.[Result]:1.. Technical parameters: Among the six different parameters, T1WI TR/TE 585/40ms showed better imaging quality than 450/31ms and 700/50ms(p<0.05); T2WI TR/TE 2261/120ms showed better quality than 1892/100ms and 2800/140ms(p<0.05); slice thickness using 1mm showed better imaging quality than 2mm and 0.8mm (p<0.05);FOV 60/45mm showed better than 80/60mm and 40/30mm;DWI using b value 600s/mm2 showed better imaging quality than b value of 800s/mm2 and 1000s/mm2(p<0.05);FLAIR 6000/140ms showed better imagine quality than 7000/160ms and 5000/120ms(p<0.05).Those parameters got the most pictures of 3 score.Hence we adopted the parameters with T1WI TR/TE 585/40ms,T2WI TR/TE 2261/120ms,slice thickness lmm, FOV 60/45mm,DWI using b value 600s/mm2, FLAIR 6000/140ms.2. Imaging study: Rats of the two infected group showed anorexia,exhausted, depress and emaciated. It may recover after the 21st day and no rats died till the last timepoint. Two rats of the pure immunosuppression group showed dome shaped back,lowering of head,horripilation,exhausted,emaciated,mouse-nose-eye bleeding till the last point.The main MR images of cryptococcal meningoencephalitis of animal model included meningeal enhancement and intracerebral lesions. Meningeal enhancement mainly focus on the frontal and parietal lobe as mild linear enhancement. Meningeal vascular hyperemia,inflammatory cells and lymph cells infiltration were seen on pathology. Cryptococcus neoformans were seen on meninges. Cerebral parenchyma lesions maily appeared as iso-hypointense on T1WI, hyperintense on T2WI like linear, spot or nodular shape on the side of the lateral ventricle and the basal ganglia. Of which ten rats of the intracerebral group showed annual enhancement with periphery hyperintense, central hypointense, and diffusion was limited. Two rats showd tuberculiform enhancement at the bottom of brain. Brain tissue was dissolved with huge Cryptococcus neoformans on pathology. Ventriculara dilation maily appeared as mild lateral ventricular dilation with Cryptococcus neoformans on the edge of the ventricular.The rat number of the two groups with positive images were 27(75%)and 8(22.2%). There was significant difference of the two ways,p<0.01. There were 23(63.9%),20(55.6%),26(72.2%) rats showed meningeal enhancement, intracerebral parenchyma focus and ventricular dilation of the intracerebral group, while 5(13.9%),2(5.6%),7 (19.4%) of the tail vein group. Whats more, all of these phenomenons had statastical significance of the two group as p< 0.01. Also it had significant difference on the meningeal enhancement on the 14th day.It mainly manifested meningeal enhancement at the first two weeks after infection. There were 7(41.7%) and 10(45.8%) rats showed meningeal enhancement at the 7th and the 14th day. While 7(29.2%) and 9(37.5%) rats displayed as parenchyma lesions.9(37.5%) and 7(29.2%) rats appeared as ventricular dilation separately. The three kinds of lesions were most serious at the 14th and the 21st day with 11(45.8%),11(45.8%);9(37.5%),9(37.5%);11(45.8%),11(45.8%). It became 7(29.2%),6(25%),8(33.3%) respectively till the last time point.The contrast group:Intracerebral saline group:There were stip signal at the 3rd day,hypointense on T1WI,hyperintense on T2WI, hypointense on FLIAR and DWI, no enhancement after contrast on four rats. Pathologically it showed brain tissue swollen, inflammatory cells infiltration, no neoformans be found. It could be disappeared at the second time point and no positive pathological changes. Two rats showed exhausted,emaciated, mouse-nose-eye bleeding of the pure immunosuppressive group. Lateral ventricular dilation appeared without any enhancement lesions of the brain at the 1st observed time point. Cerebral swollen could be found after assection.Saline group had no obvious findings.[Conclusion]1. The optimization scanning parameters of 1.5T MRI with special animal coil were T1WI:585/40ms,T2WI:2261/120ms,FLAIR:6000/140ms,b value:600s/mm2,FOV:60/45m m,slice thickness:1mm.2. The early findings of Cryptococcal meningoencephalitis on MRI were meningeal thinkening and enhancement(meningeal hyperemia with a few Cryptococcus neoformans on pathology), following brain parenchymal lesions as inflammatory cell infiltration, gelatinous pseudocysts(inflammatory cells infiltration,cerebral tissues dissolved with huge neoformans), and ventricle involvement as ventricular dilation(cryptococcus neoformans on the side of the ventricle). The lesions could diminish as self-metabolism and immune system recovery.3. Intracerebroventricular injection is a straight way to cause diseases with few affected factors and can form integrated infection. It can be helpful for dynamic observation and summarization. While the tail-vein injection can be affected by blood-brain barrier, cyclophosphamide drug side effect and self-condition situation.Moreover, the lesions caused by this way are few. In all,the second infection way is not better than Intracerebroventricular injection way.PartⅡClinical and imaging investigation of patients with Cryptococcal meningoencephalitis:a comparison of AIDS and non-AIDS[Objective]To study the value of the animal model observed in part 1. To analyze clinical and imaging findings of the AIDS and non-AIDS related cryptococcal meningoencephalitis in patients.[Material and Method]Retrospectively analyzed the common and different points between AIDS and non-AIDS related cryptococcal meningoencephalitis on clinical features,duration of hospitalization,treatment,turnover,prognosis and images.[Result]The AIDS group and non-AIDS group had the same age bracket. The duration of hospitalization of the former group was longer than the latter one. Clinical features manifested as headache,fever,nausea and vomit, while the secondary disease of AIDS group as meningeal irritation sign, visual impairment and cryptococcal pneumonia were more serious than non-AIDS group (13.0%vs6.3%,13.0%vs6.3%,43.5%vs0).Of which the cryptococcal pneumonia had statistical difference between the two groups,p<0.01. Whats more, the CD4 cell count<100ul in AIDS group(23 cases) were more than non-AIDS group(12.5%,2cases),it had significant difference,p<0.01. Also AIDS group had a higher mortality than non-AIDS group(17.4%vs6.3%). The main images included Virchow-Robin space dilatation, meningeal enhancement, gelatinous pseudocysts and hydrocephalus. Encephalatrophy,granuloma and vasculitis could also happen. Meningeal enhancement, granulomous disease and enhancement focus were less than non-AIDS group (3vs9,1 vs5,Ovs4).The images were quite similar with those of the first part.[Conclusion]The images of the acute infection of cryptococcal meingencephalitis of animal model were quite similar with that of the clinical cases.It maily appeared as meningeal enhancement of animal model while patients usually demonstrated as cerebral parenchyma focus.Compared with non AIDS-related cryptococcal meningoencephalitis in patients, AIDS patients are immunocompromised,have more serious clinical secondary disease, worse treatment,higher mortality. The enhancement focus and granulomous disease of AIDS group are lower than non AIDS group. MR has high sensitivity on detecting of the related focus of cryptococcal meningoencephalitis. It can be used as an important means of early diagnosis.

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