Study on Optimization Method of Quantization Step and the Image Quality Evaluation for Medical Ultrasonic Echo Image Compression by Wavelet Transform
Vimontha Khieovongphachanh, Kazuhiko Hamamoto, Shozo Kondo · IEEJ Transactions on Electronics Information and Systems · 2009
average method, subjective assessmentIn this paper, we attemped optimized quantization method in JPEG2000 application for medical ultrasonic echo images.JPEG2000 has been issued as the new standard for image compression technique, which is based on Wavelet Transform (WT).There are two quantization methods in JPEG2000.One is the scalar derived quantization (SDQ), which is usually used in standard JPEG2000, and the other is the scalar expounded quantization (SEQ).the latter can be optimized by user.Therefore, this paper is to find an optimization method of quantization step, which is determined by Genetic Algorithm (GA).Then, the results are compared with standard JPEG2000 (SDQ) and arithmetic average method.the proposes improve image quality and compression rate for medical ultrasonic images.The image quality is evaluated by objective assessment, PSNR (Peak Signal to noise Ratio) and subjective assessment is evaluated by ultrasonographers form Tokai University Hospital and Tokai University Hachioji Hospital.The results show that SEQ determined by Genetic Algorithm provides better image quality than SDQ and SEQ determined by arithmetic average method. Optimization Method for Quantization StepArithmetic average method: wavelet coefficients in each frequency component are averages.Then, the quantization step is based on reciprocal value of the average.Genetic Algorithm: Genetic Algorithm (GA) consists of initial population, which is evaluated using a fitness function.Then, a new population is generated by selection, crossover and mutation.The fitness function is modified to (Mean Square Error: MSE) and Peak Signal to Noise Ratio (PSNR).