sentences:  DCTs are also commonly used for high-definition television (HDTV) encoder/decoder chips.In 1972, the engineer from British company EMI Housfield invented the X-ray computed tomography device for head diagnosis, which is what we usually called CT(Computer Tomography).The CT nucleus method is based on the projection of the human head section and is processed by computer to reconstruct the cross-sectional image, which is called image reconstruction.