Comparison between windowing apodization functions techniques for medical ultrasound imaging

Ultrasound imaging is one of the important noninvasive technique that using in medical diagnosis. Unfortunately the far field beam pattern in ultrasound is a sinc function which has a better main-lobe (the resolution of ultrasound imaging) and high side-lobe about 13dB down from the maximum on axis value (the contrast of ultrasound imaging).The result for that is one of a famous artifact in medical ultrasound that the anatomy of the organ outside the main beam to be mapped into the main beam. In this work we used eleven windowing functions to rounded edges of the aperture that taper toward zero at the ends of the aperture to create low side-lobes level and reduce the false echo. Windowing functions used (hamming, hanning, Blackman, Bartlett, Nuttall, Kaiser (β=4,8,12 and 16), Parzen and Bohman) as apodization functions. Images are reconstructed by linear array image reconstruction and raster point technique. To evaluate these eleven windowing functions the SNR is calculated and also the sidelobe and mainlobe in dB are calculated for each window. The results showed that there is trade-off in selecting these function: the main lobe of the beam broadens as the sidelobes lower. However, Nutall, Kaiser (β =12) and Kaiser (β =16) have the best main-lobe, side-lobe and SNR. These windowing functions improve the resolution, contrast of the ultrasound image.