Wavelet-based recording stores data at high resolution
When electronic video recording was developed more than 40 years ago, few users complained that image recorders provided lower image quality than the other system components. Now, with scientific, charge-coupled-device cameras providing higher bandwidths and greater than 70-dB signal-to-noise ratios (S/Ns), the quality gap between current-generation recording devices and cameras becomes more apparent. Indeed, current recording systems cannot maintain the dynamic range or the signal bandwidth required for high-quality scientific, medical, or industrial imaging applications.
In medical imaging systems, for example, images can be generated by 2k ¥ 2k ¥ 12-bit digital angiography cameras at up to 30 frames/s. To store such images without compression would require huge data-storage capabilities. To meet these needs, most digital recording systems use Joint Photograph Experts Group (JPEG) or Moving Picture Experts Group (MPEG) methods to compress the data that need to be stored.
Unfortunately, such methods might produce artifacts, such as blocking effects and ringing, because of the partial image transform and coefficient truncation used. Higher-quality compression techniques, therefore, are especially need ed for medical applications dealing with motion-based modalities such as echo, ultrafast computed tomography, and real-time magnetic-resonance imaging.
QuVIS (Topeka, KS) has developed the QuBit digital recorder, based on a patented wavelet-compression technique, which is capable of recording images as large as 2k ¥ 2k ¥ 12-bits per component at 30 to 60 frames/s in full color or monochrome. According to Tamim Hamid, vice president of QuVIS` Scientific and Medical Division, the approach used does not generate JPEG/MPEG-like artifacts because the wavelet transform uses no coefficient truncation. He explains that in the JPEG and MPEG use of partial image transformation with coefficient truncation and operation in a data rate priority mode quality is compromised to control the data rate.
On the other hand, QuBit operates in a quality priority mode. In this mode, meeting or exceeding the specified quality level controls the data rate. In addition, loss is introduced as a noise-filtering process in which the S/N can be controlled, and the only artifact is the softening of the image as more loss is induced. QuBit retains full resolution and does not induce contouring in this process at any compression level.
QuVIS has formed an alliance with AAC (Dayton, OH), a provider of tele-health-care systems to Johnson & Johnson (Cincinnati, OH) and their customers. The provider will use the QuBit recorder in systems that will transmit 2k ¥ 2k ¥ 12-bit images over 100BaseT networks using the recorder`s Ethernet interface. For more information, contact Tamim Hamid at [email protected].
