Study on Quantitative Echography of Ocular Lesions with A Newly Developed Ultrasonic Diagnostic Equipment

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In ultrasonic diagnosis of ocular and orbital lesions it is important to evaluate the ultrasonic reflectivity of the target tissue. The method used for the purpose, is termed as quantitative echography. It can be divided into two categories: the one is to estimate the nature of point-like or membrane-like lesions from their surface reflectivity, and the other is to estimate the histologic characteristics of space-occupying lesions from their internal reflectivity. In the former point-like or membrane-like lesions in the eye, and point-like lesions in the orbit are diagnosed on the reflectivity of ultrasound to the target tissue. We have studied many cases of ocular membrane-like lesions such as retinal detachment, vitreous hemorrahge and proliferative membrane formation using Kretztechnik 7200 MA. From those results two problems in doing quantitative echography have become the subject of investigation. One of the problems is that the direction of A-mode ultrasonic beam through the targ … More et tissue could not be displayed on the monitor. The problem has been solved after the advent of the modern ultrasonic diagnostic equipment, in which the direction of A-mode ultrasonic beam can be displayed on the B-mode image. It is easily and precisely to apply the ultrasonic beam perpendicularly to the surface or to the center of the lesion. The second problem is that for determining the reflectivity of a ceratin membrane-like lesion, it is necessary to have the reflectivity from the standard tissue, the sclera to compare with. Ordinarily reflectivity judgment should have been done twice at least, the one from the target tissue and the other from the standard tissue. In the newly developed equipment A-mode image can be extended and enlarged on the screen. Reflectivity of the individual peaks can be shown with the scale. Therefore the value of reflectivity with the unit of dB can be directly read. The only point to be inquired is on what level the gain should be initially set. There are several ways to decide the initial level of the gain. First, it is decided on the data of ours obtained with Kretztechnic 7200 MA. Second, it is judged from four B-mode images of different level of gain. Third, the results of reflectivity of the sclera in the normal eyes would be considered. Further investigation is necessary to decide the best way.The most important thing in quantitative echography in the ocular lesion is to differentiate the detached retina from other lesions. It is extremely important that in some case the detached retina fail to show high reflectivity to the ultrasonic beam. The followings are the cases. 1) The time interval after the onset. As the time passes, atrophic changes develop. As the result, the characteristic high reflectivity of the detached retina become absent. (2) Extension of the detached retina. In some cases of the detached retina of small extent, the figure is bullous, and the ultrasonic reflectivity is erroneously as low, because of the angle of reflection. In the cases of large extent the atrophic processes frequently develop. (3) Retinoschisis. It is one of the lesions to be differentiated from the detached retina. Other characteristics such as size, figure or thickness should be considered. (4) Inflammation. In secondary retinal detachment the reflectivity is often low. (5) Proliferative processes. In cases of proliferative processes in the vitreous such as diabetic vitreoretinopathy the ultrasonic reflectivity is much effected. (6) Difference of the reflectivity in the different localization. It is said that in detached retina the reflectivity in the periphery is the same or higher, compared with that in the posterior. (7) Comparison to the prescleral layer. Sometimes reflectivity of the prescleral layer is useful to differentiate the detached retina. (8) Age. Age is said to be considered to evaluate the reflectivity.Upon those points mentioned above, investigation in many kinds of retinal detachment, fresh and old, simple or complicated, idiopathic or secondary, are going on. A part of the results or opinions have been presented in international and domestic meetings. Less