本文是一篇在职硕士论文，在职硕士又称不脱产研究生，按照学习方式的不同，我国的研究生可分为脱产研究生和不脱产研究生。前者指在高等学校和科研机构进行全日制学习的研究生，又称全日制研究生；后者指在学习期间仍在原工作岗位承担一定工作任务的研究生。（以上内容来自百度百科）今天为大家推荐一篇在职硕士论文，供大家参考。
1. INTRODUCTION
Meningiomas are the most common nonglial primary brain tumor and the mostcommon intracranial extraaxial neoplasm accounting for 15-20% of all primarybrain tumors [1]. An annual incidence of 6 per100, 000 population has beenestimated for meningioma [2]. Approximately 2% to 3% of the population has anincidental asymptomatic meningioma, and in autopsy studies 8% of these aremultiple [2,3]. They are seen to be more common in older population and female[4].Most meningiomas arise from the “arachnoid cap cells”[5], which are thespecialized meningothelial cells in the arachnoid granulations, while a few arisefrom the dural fibroblasts and the others from arachnoids associated with cranialnerves and the choroid plexus. More than 90% of meningiomas are supratentorialwith the exception of children. Meningiomas are usually sharply circumscribedlesions with a well-delineated tumor-brain interface, presenting a homogenouscontrast enhancement with the dural tail sign a classic sign on imaging. Usuallysurrounding this extraaxial mass is a distinct cleft of arachnoids with trapped CSFand prominent vessels [1]. Heterogeneous enhancement, marked perilesionaledema, irregular cerebral surface, cystic appearance, intratumoral hemorrhage andparenchymal invasion are the atypical imaging features detected, which are notspecific or reliable diagnostic features for the differentiation of the non-benignmeningiomas from benign lesions [6].
According to the WHO 2007 classification of tumors, benign meningiomas (gradeI) are the most common accounting for of 80–90% of all meningiomas. Whereasatypical (Grade II) accounts for 4.7–7% and malignant meningiomas (Grade III)accounts for 1–2.8% [5,7]. Even after complete excision of these tumors, they arestill associated with recurrence feature, brain parenchymal invasion is an importantrecurrence marker, the high rate being associated with malignant meningioma 50-80% within 5 years followed by atypical being about 40% [8] while benign mayrecur in 7-15% of the cases [9,10,11,12] (approximately), leading to increasedmortality and morbidity. However, just the tumor grade might not justify tumorrecurrence, several other factors account for its recurrence, which includes, braininfiltration, proliferative activity and extent of tumor resection [13].Although the recurrence rate is low, benign meningiomas still needs to bedifferentiated as some of its subtypes like angiomatous and microcysticmeningiomas possesses features like extensive peritumoral edema which maymimic high grade meningiomas like atypical and anaplastic ones on routineMRI[14].Conventional magnetic resonance imaging (MRI) in the structural study ofintracranial neoplasms is commendable, no doubt, but it does have somelimitations over meningeal tumor grading. Meningiomas of the samehistopathological characterization and receiving similar treatment may displayperse outcome because of differences in the proliferative potential of the diseaseor because of different molecular characteristics which is why it is very importantto differentiate them, so as to facilitate surgical decision (a hard consistentfibroblastic subtype of benign meningioma if located in the skull base, makes itsurgical removal difficult) and imply treatment considerations[15,16,17,18] forbetter prognosis.Modern era has witnessed significant improvement in diagnostic specificity withthe help of functional and molecular imaging modalities including diffusionimaging, perfusion imaging, spectroscopy, nuclear imaging, all helping in theevaluation and determination of fundamental biological feature of brain tumors[19,20,21].
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2. MATERIALS and METHODS
2.1 Patient Profile
From the Neurosurgical Department of Union Hospital of Fujian MedicalUniversity, Fuzhou, P.R.China, a total of 80 patients with suspected meningiomaon conventional brain MRI over a 2-year period (August 2014- October 2016)were continuously included in the study. In all the above patient preoperativeimaging including conventional MRI, conventional DWI, DTI and DKI wereperformed. A total of 72 patients were included in this study. Among the 72patients, 61 were WHO grade I meningioma (benign) age range 30 to 72 years,mean 52.39±10.36 with 48 females and 13 males. 9 were WHO grade II and 2were WHO grade III meningioma, age range 32 to 79 years, mean 57-70±16.20with 9female and 2 male patients as shown in Table 1. Histological diagnoses ofthe tumor were done and verified by 2016 WHO classification of tumors of thecentral nervous system. We considered WHO grade II and grade III meningiomatogether as non-benign, thereby having 11 non-benign patient. Studies wereperformed abiding by the rules and guidelines of the hospital committee on clinicalinvestigations. Informed consent of each patient was taken following the protocolset by the local ethics committee of the hospital. All patients had undergone totalor partial surgical resection of the lesion in our hospital.
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2.2 Patient Selection
Inclusion criteria included patients with solitary brain tumor with conventionalMRI characteristics compatible with meningioma i.e. solitary, homogenous brainlesion showing enhancement after contrast administration. Adult co-operativepatient were preferred. Another thing considered was, no patient had beguncorticosteroid treatment, radiotherapy or chemotherapy before MR imaging.Exclusion criteria included patients with MRI studies performed outside thehospital, children, patient with multiple lesion and those with previous history ofsurgery or meningioma treatment, chemotherapy or radiotherapy. Furthermoreimages with motion artifacts were excluded.
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Materials and Methods........11
Results........15
Discussion........19
Conclusions........23
4. DISCUSSION
Pre-operative distinction of benign and non-benign meningioma is a critical stepfor it decides the therapeutical schedule and the surgical approach (to determinethe extent of tumor resection) for the different group differently. In cases withincidental findings, the dilemma as to treat or not to treat would be resolved to agreater extent with preoperative differentiation. Non-benign (Grade II/III)meningiomas display significant higher mean time for doubling of the tumorvolume than benign meningiomas [44]. Moreover non-invasive assessment ofmeningioma grade helps to permit dose escalation in Grade II/III meningiomas [45](non-benign) in which tumor control rate with Gama-knife surgery is 76% and56% respectively [46].In this study, we used DKI, an advanced non-Gaussian imaging technique forefficient differentiation of benign and non-benign meningiomas, comparativeanalysis of the kurtosis and conventional diffusion metrics between the benign andnon-benign meningiomas were done, and the subsequent efficiency wasdetermined by the ROC curve. The normalized value of MK, KA and KR allshowed significant result in differentiating benign and non-benign meningioma,they were shown to be effective in differentiating benign from non-benignmeningiomas, also AUC of ROC curve was greater for normalized KA than MK orKR and optimally promising than the other conventional diffusion metrics. Basedon the AUC curve it can be inferred that the increase of restriction in axialdirection was more obvious than in the radial direction or the normalized KA valuewas a better predictor for the change in restriction. MD, ADC and FA howevercould not show promising results for this study. Higher kurtosis metrics were seenwith non-benign meningiomas owing to their higher cellularity, increased nuclearatypia, pleomorphism, heterogeneity due to cystic, necrotic or hemorrhagiccomponents. All these tissue variation causes the water molecules to deviate fromthe Gaussian distribution, thereby increasing the kurtosis and decreasing thediffusion range. On the contrary lower kurtosis metrics were attributed to benignmeningioma due to their more homogenous nests of well-differentiated lowerdensity larger cells [39,40,47], all of these causes more diffusion range anddecreased kurtosis.
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CONCLUSION
In conclusion, our study indicated that the normalized DKI parameters can beefficiently used to differentiate between the benign and the no-benignmeningiomas. Also better directional estimation can be potentially seen with DKIespecially KA than other diffusional parameters suggesting microstructural changein non-benign meningioma allowing more accurate diagnosis and increasing thetreatment scope.
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References (abbreviated)