| BackgroundObstetric ultrasound is more and more widely applied in obstetrical department today, which is a obbligato imaging diagnostic tool. It can not only diagnosis abnormality of fetuses, but also can estimate diseases of the mother. During the past 20 years, as the improvement of ultrasonic instrument performance and the intensive study of ultrasound feature of pregnant and the occurrence and development of fetuses malformation, obstetric ultrasound plays a important role in reducing morbidity, mortality, and birth defects in the perinatal period. In the present stage of prenatal ultrasound diagnosis, many common congenital diseases have been able to diagnosis in the prenatal, and many common deformities of each system have been reported, but there are some agnogenic diseases, especially intracranial disease, puzzls clinica, making doctors at a loss. The embryonic development of the human central nervous system is a very complicated process, the ultrasound image of which has obvious staggered transformation in the process of developing. In this premise, if there are internal and environmental factors influencing embryonic development, it will inevitably cause the diversity and complexity of development results, which could explain the difficult diagnosis of fetal intracranial diseases.At the same time, ultrasound has its own physical effect, such as reverberation artifacts, partial volumeeffect and reflection when irradiate to high attenuation coefficient objects and so on, those all enhance the difficult of diagnosis of intracranial diseases. Fetal intracranial structures are complex, with a skull acoustic shadow block, though thanks to the typical characteristics some intracranial diseases such as holoprosencephaly, hydrocephalus and anencephaly can be diagnosised prenatal, there are many abnormalities are still in research stage or need a MRI scan. But the prenatal examination dominated by ultrasound, MRI is performed as the further examination when ultrasound detected abnormality. International MRI security council pointed out that prenatal MRI imaging method is suitable for diseases that non-radioactive methods cannot make a diagnosis but MRI is helpful to diagnosis. MRI is expensive and have contraindications such as claustrophobia, wear metal, pacemaker and so on. MRI also have demand for gestational age, if gestational age less than 20 weeks, the fetus volume is small and amniotic fluid is sufficient that all lead to frequently quickening, so the image resolution is easily to be affected. Therefore it is advisable to perform a MRI examination after 26 weeks. In addition, MRI can not perform real-time imaging for fetus, and limited by slice thickness and layer spacing, so MRI has certain limitation when examine the intracranial delicate structure of fetus. That’s why MRI is not been used as a routine examination. So how to perform prenatal diagnosis of fetal intracranial diseases, exploit blind angle of prenatal ultrasonic diagnosis come to be the new orientation. In this background, our study take fetal intracranial optic nerve, optic chiasma and optic tract as object, to research the relative diseases of them, aims to supplement the research of optic nerve, optic chiasma and optic tract of sensitization system in the domain of prenatal ultrasound.Chapter 1 Establish the normal reference range of optic chiasma of second and third trimester fetusesObjectiveUse high resolution prenatal transabdominal two-dimension ultrasound and three-dimensional volume ultrasound to research the size of optic nerve, optic chiasma, optic tract and optic nerve angle of fetuses in second and third trimester, to explore the displaying rate of optic nerve, optic chiasma and optic tract under prenatal ultrasound and establish the normal reference range of them, to research the difference between two-dimension ultrasound and three-dimensional volume ultrasound and the difference between left and right side of fetus.MethodsRotating the probe to display the optic chiasma plane on the base of ring of willis plane using high resolution two-dimension ultrasound, and measure the diameter of optic nerve and optic tract in two sides, the diameter and area of optic chiasma and optic nerve angle of 623 fetuses. Collecting the volume date on the optic chiasma plane using three-dimension, disposing with oblique view imaging mode to debug the objective plane on which to measure the size of optic nerve diameter, optic tract diameter, optic chiasma diameter and area of 623 fetuses. Comparing the difference between two sides, between two-dimension ultrasound and three-dimension ultrasound and sexual difference in the same gestational age. Using gestational age and corresponding biological parameters to establishing linear regression model of each measurement value.ResultsThe optic chiasma plane has a good displaying rate at 26-33 weeks. The measure method of this study has a good repeatability except for optic chiasma area, it had no significant difference between two observers. There is no significant difference between two sides, and no significant difference between two-dimension ultrasound and three-dimension ultrasound except for optic chiasma area. All the measurements except for optic nerve angle increase with gestational age, presenting positive correlation(r2=0.891-.0.914n 0.602), while optic nerve angle is decrease with gestational age, presenting negative correlation (r2=0.324). The fitting model of optic nerve diameter, optic tract diameter, optic chiasma diameter and optic nerve angle are mn=-0.001+0.01GA, mt=0.003+0.01GA, cc=0.276+0.015GA, A=129.7-1.445GA respectively. There is no significant sexual difference of all the measurements.ConclusionThe prenatal ultrasound can satisfied observe and assess the form and size of optic nerve, optic tract and optic chiasma, and offering imaging reference for diagnosis of abnormality of the optic chiasma and vicinity visual pathway. Because of the poor repeatability of optic chiasma and the difference under different measure modes, the optic chiasma area is not recommended as a index for assessing. The effect of two-dimension ultrasound and three-dimension ultrasound is comparative, to supplement each other, the former can confirm the latter, the latter can supplement the former when the fetus is malposition. We can regard the optic nerve and optic tract of two sides as the same size.Chapter 2 Explore the relationship between circle of willis size and optic chiasma sizeObjectiveTo explore the relationship between size of cirlce of willis parameter and optic chiasma.Methods Select 606 fetuses who have a good optic chiasma display and can get satisfied circle of willis blood flow information. Measure on the freezed circle of willis plane,Dl, straight-line distance between the two intersection point of both sides of the posterior cerebral artery and the posterior communicating artery; D2, straight-line distance between the two intersection point of both sides of the arteria cerebri anterior and end of the internal carotid artery; D3, straight-line distance between anterior communicating artery midpoint and posterior cerebral artery crotch; S, area of circle of willis, using trackball to trace along with the middle part of vessel of circle of willis as a quasi-circular. Using gestational age and corresponding parameters to perform liner regression analysis of circle of willis’s parameters. Combine the corresponding measurements of optic chiasma in chapter 1, to perform partial correlation analysis and model fitting of circle of Willis’s parameters and optic chiasma parameters.ResultsMultiple linear regression analysis indicate that circle of willis’s parameters and gestational age have the best significant relation. S, D1, D2, D3 all have a unary linear relation with gestational age, the adjusted R2 of each liner model is 0.451、 0.369、0.476、0.098 respectively. Partial correlation analysis indicate that the most significant relationship exist between optic never diameter and D1 (P=0.029), optic tract diameter and D1 (P= 0.037), optic chiasma diameter and S (P= 0.000) respectively. The liner fitting models are CC=0.0347 s+0.334, mn=0.242D1+0.106, mt=0.241D1+0.101, the adjusted R2 is 0.0.384、0.356、0.358 respectively.ConclusionThe parameters of circle of willis all have the best significant relation with gestational age, presenting positive correlation; The adjusted R2 of liner fitting models between parameters of circle of willis and gestational age are 0.369 (D1)、0.476 (D2)、0.098 (D3)、0.451 (S), among which D2 and gestational age has the best fitting effect, then S, D3 has worst. D1 and S have the most close relation with corresponding structure of optic chiasma, the adjusted R2 of liner fitting models between D1, S and mn, mt, cc are 0.356、0.358、0.384, so use S to fit optic chiasma diameter is the best model by contrast, but because of the adjusted R2 all under 0.5, the fitting effect is worth more considerations.Chapter 3 Explore the clinical significance of examining optic chiasma and corresponding structureObjectiveTo research the optic never, optic chiamsa, optic tract and optic never angle size of fetuses with intracranial middle structure abnormal especially SOD fetuses in second and third trimester. To explore the diagnostic value to abnormal cerebral midline structure of the results in chapter 1.MethodsCollect fetuses diagnosised with abnormal cerebral midline structure by ultrasound and confirmed by MRI from pregnant women who come to Shenzhen maternity and child healthcare hospital to have prenatal ultrasound examination or consultation during October,2014 to October,2015, we get 37 cases. Classified them by whether diagnosed as SOD, if not it will be grouped into group 1, if so, then group 2. Use the method described in chapter 1 to measure parameters of optic chiasma and corresponding structure and compare them with the dates obtained in chapter 1.ResultsThere is no significant difference between two-dimension ultrasound results and three-dimension results in group 1. Some gestational weeks in group 1 have significant difference when comparing with measurements of normal fetuses in chapter 1, the fetuses have significant difference all have agenesis of corpus callosum, septum pellucidum dysplasia. Fetus in group 2 have the left optic never diameter significantly lower than the 5th percentile line of normal fetuses measurements in group 1, the right optic never is also lower than the 5th percentile but thicker than left.ConclusionPrenatal ultrasound can satisfied assess the size of optic chiasma and corresponding struct of fetuses with abnormal cerebral middle structure; When the fetuses with abnormal cerebral structure in second and third trimester have agenesis of corpus callosum, septum pellucidum dysplasia, it can easily coexist with abnormality of optic chiasma and corresponding struct, so when ultrasound detect those two abnormalities, we should exame the optic chiamsa, if the latter is abnormal, a gene testing is necessary to exclude SOD. The normal reference range of normal fetuses measurements in second and third trimester of chapter 1 have reference value to assess the size of optic chiasma and corresponding struct of fetuses with abnormal cerebral middle structure in this chapter. |
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