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This process began in the early 1990 when ultrasound techniques gained widespread use in India. There was a tendency for families to continuously produce children until a male child was born. [ 4 ] Foetal sex determination and sex-selective abortion by medical professionals has today grown into a Rs. 1,000 crore industry (US$244 million) in India.
Ultrasound technology arrived in China and India in 1979, but its expansion was slower in India. Ultrasound sex discernment technologies were first introduced in major cities of India in 1980s, its use expanded in India's urban regions in 1990s, and became widespread in 2000s.
Ultrasound-based pre-natal care and sex screening technologies were launched in India in the 1980s. With concerns about its misuse for sex-selective abortion, the Government of India passed the Pre-natal Diagnostic Techniques Act (PNDT) in 1994 to distinguish and regulate legal and illegal uses of ultrasound equipment. [122]
A curvilinear array ultrasonic transducer for use in medical ultrasonography Inside construction of a Philips C5-2 128 element curved array ultrasound sensor. Ultrasonic transducers and ultrasonic sensors are devices that generate or sense ultrasound energy. They can be divided into three broad categories: transmitters, receivers and transceivers.
Typical diagnostic ultrasound machines operate in the frequency range of 2-18 megahertz, whereas home ultrasound machines and therapeutic ultrasound machines operate in the frequency range of .7-3.3 megahertz. Diagnostic sonography is typically used to create an audio "image", such as during pregnancy to visualize the developing baby.
Ultrasound is defined by the American National Standards Institute as "sound at frequencies greater than 20 kHz". In air at atmospheric pressure, ultrasonic waves have wavelengths of 1.9 cm or less. Ultrasound can be generated at very high frequencies; ultrasound is used for sonochemistry at frequencies up to multiple hundreds of kilohertz.
Much research showed that 3D imaging which generates volumetric images, will result in better medical interpretations and more accurate diagnosis than the conventional 2D method. [18] However, the benefits of 3-D ultrasound imaging come with challenges concerning the computational complexities.
The sex of the fetus may be discerned by ultrasound as early as 11 weeks' gestation. The accuracy is relatively imprecise when attempted early. [15] [16] [17] After 13 weeks' gestation, a high accuracy of between 99% and 100% is possible if the fetus does not display intersex external characteristics. [18]