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- يستخدم جهاز الموجات فوق الصوتية(ultrasound) في التصوير الطبي ويعتمد على الموجات فوق الصوتية التي يكون ترددها أكثر من 20 كيلو هيرتز, ومن أنواعه ما يسمى بمسح السعة أو مسح المدى(Amplitude scan),ويرمز له(A scan). هذا النوع يقوم بإنتاج صورة ببعد واحد 1D حسب العلاقة الخطية بين العمق للنسيج الذي ننظر إليه والزمن الذي تحتاجه الموجات فوق الصوتية للوصول لهذا العمق والارتداد مرة أخرى باتجاه محول الطاقة (transducer-piezoelectric). (ar)
- A-scan ultrasound biometry, commonly referred to as an A-scan (short for Amplitude scan), is a routine type of diagnostic test used in optometry or ophthalmology. The A-scan provides data on the length of the eye, which is a major determinant in common sight disorders. The most common use of the A-scan is to determine eye length for calculation of intraocular lens power. Briefly, the total refractive power of the emmetropic eye is approximately 60. Of this power, the cornea provides roughly 40 diopters, and the crystalline lens 20 diopters. When a cataract is removed, the lens is replaced by an artificial lens implant. By measuring both the length of the eye (A-scan) and the power of the cornea (keratometry), a simple formula can be used to calculate the power of the intraocular lens needed. There are several different formulas that can be used depending on the actual characteristics of the eye. All the information here is not valid for medical purposes. The other major use of the A-scan is to determine the size and ultrasound characteristics of masses in the eye, in order to determine the type of mass. This is often termed quantitative A-scan. Instruments used in this type of test require direct contact with the cornea, however a non-contact instrument has been reported. Disposable covers, which come in actual contact with the eye, have also been evaluated. (en)
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- A-scan ultrasound biometry (en)
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- diagnostic test used in optometry (en)
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- يستخدم جهاز الموجات فوق الصوتية(ultrasound) في التصوير الطبي ويعتمد على الموجات فوق الصوتية التي يكون ترددها أكثر من 20 كيلو هيرتز, ومن أنواعه ما يسمى بمسح السعة أو مسح المدى(Amplitude scan),ويرمز له(A scan). هذا النوع يقوم بإنتاج صورة ببعد واحد 1D حسب العلاقة الخطية بين العمق للنسيج الذي ننظر إليه والزمن الذي تحتاجه الموجات فوق الصوتية للوصول لهذا العمق والارتداد مرة أخرى باتجاه محول الطاقة (transducer-piezoelectric). (ar)
- A-scan ultrasound biometry, commonly referred to as an A-scan (short for Amplitude scan), is a routine type of diagnostic test used in optometry or ophthalmology. The A-scan provides data on the length of the eye, which is a major determinant in common sight disorders. The most common use of the A-scan is to determine eye length for calculation of intraocular lens power. Briefly, the total refractive power of the emmetropic eye is approximately 60. Of this power, the cornea provides roughly 40 diopters, and the crystalline lens 20 diopters. When a cataract is removed, the lens is replaced by an artificial lens implant. By measuring both the length of the eye (A-scan) and the power of the cornea (keratometry), a simple formula can be used to calculate the power of the intraocular lens neede (en)
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- A-scan ultrasound biometry (en)
- المسح الضوئي بالموجات فوق الصوتية (ar)
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