Study on medical ultrasonic echo image compression by JPEG2000 : optimization and the subjective assessment of the quality

Lossy pulse echo ultrasonic image compression by a JPEG baseline system is permitted in DICOM and many papers about it have been presented. On the other hand, application of JPEG2000 to DICOM has been investigated. JPEG2000 is a new standard of image compression whose basis is wavelet transform. Although JPEG2000 is superior to JPEG in general, the viewpoint may not be applied to medical ultrasonic echo image since features of the image are unique and different from one of natural image significantly. In this paper, it is attempted to optimize the compression condition of JPEG2000 for medical ultrasonic echo image. There are two quantization methods in JPEG2000. One is the scalar derived quantization and the other is the scalar expounded quantization. The latter can be optimized by user. In this paper, firstly, it is shown that the scalar derived quantization is not appropriate for medical ultrasonic echo image even though the PSNR is high. Secondly, the scalar expounded quantization is optimized for the image. Lastly, the images by conventional JPEG2000 and ones by optimized JPEG2000 are evaluated by ultrasonographers. The results of the subjective assessment show the images by optimized JPEG2000 preserve more important diagnostic information than conventional JPEG2000.